Category Nature Science & Wildlife

Human beings are far from being the longest-living animals. The giant tortoise can reach 150 years, while several aquatic creatures, such as the killer whale and some species of sea anemone, can survive for well over 80 years. At the other end of the scale, the adult mayfly lives for less than two days. The plant kingdom has far longer-living species. Several trees, such as the yew and giant sequoia, live for thousands of years.

There are tortoises alive today that were 25 to 50 years old when Charles Darwin was born. There are whales swimming the oceans with 200-year-old ivory spear points embedded in their flesh. There are cold-water sponges that were filter-feeding during the days of the Roman Empire. In fact, there are a number of creatures with life spans that make the oldest living human seem like a spring chicken in comparison.

Greenland shark: This shark lives in Arctic waters and slowly grows to an average length of 16 feet. It scavenges for its food and is attracted to the smell of rotting meat in the ocean. It’s also known to primarily live in deeper ocean depths compared to other sharks. A group of scientists conducted radiocarbon testing on the eye lens of 28 female sharks and determined its life span to reach at least 272 years. They concluded that the Greenland shark is the longest-living vertebrae known to man.

Geoducks: These large saltwater clams that are native to the Puget Sound and have been known to live for at least 160 years. They are characterized by their long ‘necks’, or siphons, which can grow to more than 1 meter long.

Tuatara: The word “dinosaur” is commonly used to describe an old person, but when it refers to tuataras, the term is perfectly metaphorical. The two species of tuatara alive today are the only surviving members of an order that flourished about 200 million years ago — they are living fossils. They are also among the longest-lived vertebrates on Earth, with some individuals living for between 100 and 200 years.

Lamellibrachia tube worms: These colorful deep sea creatures are tube worms (L. luymesi) that live along hydrocarbon vents on the ocean floor. They have been known to live 170 years, but many scientists believe there may be some that have lived for more than 250 years.

Red sea urchins: The red sea urchin or Strongylocentrotus franciscanus is found only in the Pacific Ocean, primarily along the West Coast of North America. It lives in shallow, sometimes rocky, waters from the low-tide line down to 90 meters, but they stay out of extremely wavy areas. They crawl along the ocean floor, using their spines as stilts. If you discover one, remember to respect your elders — some specimens are more than 200 years old.

Bowhead whales: Also known as the Arctic whale, the bowhead is by far the longest living mammal on Earth. Some bowhead whales have been found with the tips of ivory spears still lodged in their flesh from failed attempts by whalers 200 years ago. The oldest known bowhead whale was at least 211 years old.

Koi: Koi are an ornamental, domesticated variety of the common carp. They are common in artificial rock pools and decorative ponds. Amazingly, some varieties are capable of living more than 200 years. The oldest known koi was Hanako, a fish that died at the age of 226 on July 7, 1977.

Tortoises: Tortoises are considered the longest living vertebrates on Earth. One of their oldest known representatives was Harriet, a Galápagos tortoise that died of heart failure at the age of 175 years in June 2006 at a zoo owned by the late Steve Irwin. Harriet was considered the last living representative of Darwin’s epic voyage on the HMS Beagle. An Aldabra giant tortoise named Adwaita died at the rumored age of 250 in March 2006.

Living things are said to be animate. Inanimate things are not living. Metal, plastic and glass, for example, are inanimate. All animate things are able to do six things that inanimate things cannot.

Although seemingly diverse, living things, or organisms, share certain essential characteristics. The most recent classification system agreed upon by the scientific community places all living things into six kingdoms of life, ranging from the simplest bacteria to modern-day human beings. With recent innovations such as the electron microscope, scientists peered inside cells and began to understand the intracellular processes that defined life.

Composition

Cells compose all life, performing the functions necessary for an organism to survive in its environment; even the most primitive of life forms, bacteria, consists of a single cell. While peering through a microscope at slices of cork tissue in the late 17th century, scientist Robert Hooke discovered numerous tiny compartments which he coined “cells.” After several developments regarding cell structure and function, Robert Virchow compiled a book, “Cellular Pathology,” describing the nature of cells in relation to life. He formed three conclusions: cells form the basis of all life, cells beget other cells and cells can exist independent of other cells.

Energy Use

All processes occurring within organisms, whether single-celled or multicellular, expend energy. The method of procuring that energy, however, differs between organisms. Organisms called autotrophs make their own energy while heterotrophs must feed to obtain their energy needs. Autotrophs such as plants and some bacteria produce their own food by converting carbon dioxide and water into sugar with the aid of the sun’s energy via photosynthesis. Other autotrophic bacteria use chemicals such as sulfur to make energy in a process called chemosynthesis. The energy organisms need comes in the form of a molecule called ATP, or adenosine triphosphate. Living things make ATP by breaking down glucose.

Response

Organisms use their senses to obtain information from and have the capability of reacting to stimuli in their environments. Even unicellular organisms such as bacteria and seemingly immobile plants can respond to stimuli. Plants such as sunflowers can sense heat and light, so they turn toward the sun’s rays. Predators such as cats can track their prey with keen senses of vision, smell and hearing and then hunt them down with superior agility, speed and strength.

Growth

Living things grow and change through the process of cell division, or mitosis. In organisms composed of more than one cell, mitosis either repairs damaged cells or replace older ones that have died. Additionally, multicellular organisms grow larger in size by increasing the number of cells in their bodies. Unicellular organisms take in nutrients and enlarge. They grow to a certain point and then must divide into two new daughter cells. The process of mitosis takes place in four phases. Certain signals trigger cells to divide. The cell replicates its genetic information, resulting in two exact copies of the gene-bearing structures called chromosomes. Cellular structures separate the chromosome copies, moving them to different sides of the cell. The cell then pinches itself down the middle, creating a new barrier to separate the two new cells.

Reproduction

For a species or organism to continue existing, members of the species must reproduce, either asexually or sexually. Asexual reproduction produces offspring that exactly resemble the parent organism. Certain members in each of the kingdoms of life can reproduce asexually. Bacteria from Kingdoms Archaebacteria and Eubacteria, amoeba of the Kingdom Protista and yeast of Kingdom Fungi use binary fission to simply divide in two, resulting in two identical daughter cells. Worms called planaria can break off a segment that grows into a new organism. Plants such as potatoes form buds which, when cut off and planted, will produce a new potato plant. Sexual reproduction, which allows a mixing of genes from two individuals of a species, evolved from asexual reproduction because the benefits of sex outweigh its costs.

Adaptation

Since the beginning of life, organisms have adapted and evolved to survive according to their environments. Those individuals unable to adapt to changing conditions will die or be unable to pass on much of their genes to the next generation. Many times in the history of the earth, entire species, including many dinosaur groups, have died out when they failed to respond appropriately to environmental changes such as droughts or cooling climates. The environment selects for those individuals best acclimated to live under specific conditions; these creatures have the best selections of mates and will contribute to a greater percentage of descendants.

All cells have a cell wall, hut in plant cells this is made of a stiff, tough layer of cellulose. Cellulose is made of tiny fibres, layered together to form a strong sheet. Most plant cells also contain organelles called chloroplasts. It is in these that photo-synthesis takes place.

Animal cells and plant cells are similar in that they are both eukaryotic cells. These cells have a true nucleus, which houses DNA and is separated from other cellular structures by a nuclear membrane. Both of these cell types have similar processes for reproduction, which include mitosis and meiosis. Animal and plant cells obtain the energy they need to grow and maintain normal cellular function through the process of cellular respiration. Both of these cell types also contain cell structures known as organelles, which are specialized to perform functions necessary for normal cellular operation. Animal and plant cells have some of the same cell components in common including a nucleus, Golgi complex, endoplasmicreticulum, ribosomes, mitochondria, peroxisomes, cytoskeleton, and cell (plasma) membrane. While animal and plant cells have many common characteristics, they are also different.

Size

Animal cells are generally smaller than plant cells. Animal cells range from 10 to 30 micrometers in length, while plant cells range from 10 and 100 micrometers in length.

Shape

Animal cells come in various sizes and tend to have round or irregular shapes. Plant cells are more similar in size and are typically rectangular or cube shaped.

Energy Storage

Animal cells store energy in the form of the complex carbohydrate glycogen. Plant cells store energy as starch.

Proteins

Of the 20 amino acids needed to produce proteins, only 10 can be produced naturally in animal cells. The other so-called essential amino acids must be acquired through diet. Plants are capable of synthesizing all 20 amino acids.

Differentiation

In animal cells, only stem cells are capable of converting to other cell types. Most plant cell types are capable of differentiation.

Growth

Animal cells increase in size by increasing in cell numbers. Plant cells mainly increase cell size by becoming larger. They grow by absorbing more water into the central vacuole.

Cell Wall

Animal cells do not have a cell wall but have a cell membrane. Plant cells have a cell wall composed of cellulose as well as a cell membrane.

Centrioles

Animal cells contain these cylindrical structures that organize the assembly of microtubules during cell division. Plant cells do not typically contain centrioles.

Cilia

Cilia are found in animal cells but not usually in plant cells. Cilia are microtubules that aid in cellular locomotion.

Cytokinesis

Cytokinesis, the division of the cytoplasm during cell division, occurs in animal cells when a cleavage furrow forms that pinches the cell membrane in half. In plant cell cytokinesis, a cell plate is constructed that divides the cell.

Glyoxysomes

These structures are not found in animal cells but are present in plant cells. Glyoxysomes help to degrade lipids, particularly in germinating seeds, for the production of sugar.

Lysosomes

Animal cells possess lysosomes which contain enzymes that digest cellular macromolecules. Plant cells rarely contain lysosomes as the plant vacuole handles molecule degradation.

Plastids

Animal cells do not have plastids. Plant cells contain plastids such as chloroplasts, which are needed for photosynthesis.

Plasmodesmata

Animal cells do not have plasmodesmata. Plant cells have plasmodesmata, which are pores between plant cell walls that allow molecules and communication signals to pass between individual plant cells.

Vacuole

Animal cells may have many small vacuoles. Plant cells have a large central vacuole that can occupy up to 90% of the cell’s volume.

Prokaryotic Cells

Animal and plant eukaryotic cells are also different from prokaryotic cells like bacteria. Prokaryotes are usually single-celled organisms, while animal and plant cells are generally multicellular. Eukaryotic cells are more complex and larger than prokaryotic cells. Animal and plant cells contain many organelles not found in prokaryotic cells. Prokaryotes have no true nucleus as the DNA is not contained within a membrane, but is coiled up in a region of the cytoplasm called the nucleoid. While animal and plant cells reproduce by mitosis or meiosis, prokaryotes propagate most commonly by binary fission.

Other Eukaryotic Organisms

Plant and animal cells are not the only types of eukaryotic cells. Protists and fungi are two other types of eukaryotic organisms. Examples of protists include algae, euglena, and amoebas. Examples of fungi include mushrooms, yeasts, and molds.

Everything in the universe is mare of atoms, arranged in different ways. But living things, unlike rocks or metal, have larger building blocks called cells. Some living things have only one cell, while others contain millions. Each cell has a job to do, but they all work together to make a living organism.

Living organisms are made up of cells. Cells are the structural and functional units of a living organism. In 1665, Robert Hooke discovered the existence of cells using a microscope, which further paved way for the discovery of various other microscopic organisms. Some organisms consist of a single cell, for example, the amoeba. Other organisms are multicellular, having millions of cells.

A single cell is able to produce many cells through a process known as cell division. Different organisms have different kinds of cells. A human body alone shows various kinds of cells such as – blood cells, nerve cell, fat cell etc. Shapes and sizes of cells depend upon the functions they perform. Amoeba has an ever-changing shape as it changes form to locomote. Some cells have a fixed shape and perform a specific function, such as nerve cells, which are usually shaped like trees.

An organism is any being that consists of a single cell or a group of cells, and exhibit properties of life. They have to eat, grow and reproduce to ensure the continuation of their species. Organ systems collectively work together for the proper functioning of a living organism, failure of even one of these systems has an impact on our lives.

A fast-flowing river sweeps soil from the riverbed so that plants cannot grow there. On the other hand, there is more oxygen dissolved in the water, so that fish such as salmon thrive. Rivers in areas where the soil is peaty often have very little wildlife, because acid from the soil washes into the water.

Unlike temperature and dissolved oxygen, the presence of normal levels of nitrates usually does not have a direct effect on aquatic insects or fish.  However, excess levels of nitrates in water can create conditions that make it difficult for aquatic insects or fish to survive.

Algae and other plants use nitrates as a source of food. If algae have an unlimited source of nitrates, their growth is unchecked.  So, why is that a problem?

A bay or estuary that has the milky colour of pea soup is showing the result of high concentrations of algae.  Large amounts of algae can cause extreme fluctuations in dissolved oxygen.  Photosynthesis by algae and other plants can generate oxygen during the day. However, at night, dissolved oxygen may decrease to very low levels as a result of large numbers of oxygen consuming bacteria feeding on dead or decaying algae and other plants.

Eutrophication – “The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.

Anoxia is a lack of oxygen caused by excessive nutrients in waterways which triggers algae growth. When the plants die and decay, oxygen is stripped from the water, which then turns green or milky white and gives off a strong rotten egg odour.  The lack of oxygen is often deadly for invertebrates, fish and shellfish.

Beavers are rodents with very long, sharp front teeth. They use their teeth to gnaw down small trees for use in dam building or for food. Beavers build dams of sticks and mud across a river. This makes a calm pool the other side of the dam in which the beaver can build its home, or lodge. The inside of the lodge is reached by means of underwater tunnels. This keeps the beaver safe from predators such as wolves, even when the surface of the water is frozen in winter.

Dam-building is synonymous with beavers, the ultimate aquatic engineers. Using branches from trees they have felled, these large rodents dam lakes to create moat-like ponds of still water where they construct islands known as ‘conical lodges’ out of timber, mud and rocks. The body of water surrounding the lodges provides protection from predators – resident beavers enter and exit their sophisticated homes incognito via water-filled tunnels leading from the lodges to the pond. The largest lodge, found in Alberta, Canada, measures over 500m in length – though contrary to a widely circulated myth, it is not visible from space! In deep or fast-moving water areas, beavers simply excavate into river banks and set up home there instead.

Beaver dam building is a pretty fascinating topic. Unfortunately, no-one really knows how beavers evolved, let alone how dam building behaviour evolved. Beavers appear to build dams for two main reasons: protection from predators and to provide a stable source of food and easy access to it for themselves.

This offers some clues about how they evolved – almost certainly as a response to selection pressures for these two reasons avoid predation, obtain food. These dams are made of branches stuck down into the stream bed and then built up with a thick mortar of mud, gravel and interwoven branches.

The dam is constantly maintained to keep the water at the same level for beaver comfort and security. Beaver dams are sometimes maintained and expanded over many generations. They can be up to 1,000 feet long and 15-20 feet high.

Beavers are famous for their logging skills, chiseling down trees up to 3 feet in diameter. However, they are not clever enough to aim a tree’s fall and on rare occasions a beaver has been crushed by a tree trunk. The beaver is a very powerful animal, capable of dragging a heavy log through the woods and down into the water.

Although they often lay hundreds or even thousands of eggs, some fish do build nests to protect their young. The stickleback, found in European ponds and rivers, builds a nest of plant fibres in which the male guards the eggs until they have hatched, chasing away even the female that laid them.

The most interesting habits of fishes are their parental behavior in guarding the eggs and caring the young ones. In Chondrichthyes, young ones hatch out in a fully developed condition. But, in Osteichthyes larvae hatch out from eggs and then metamorphose to young adults. In most cases these larvae are quite numerous and so chance will favor at least few of them to tide over adverse condition.

Nest and nursery building Nest building is the commonest method adopted by fishes to protect their eggs and young ones. It is exhibited mostly by fresh water fishes and also by marine fishes having demersal eggs. Nest building involves active participation of either males or females or both. The simplest form of nest building is exhibited by salmons, darters, sunfishes, cichlids, etc. Salmons select gravelly shallows of running streams as their spawning ground. Here they assemble in shoals. Female will make a nursery in the form of pit to lay eggs. After fertilization, she will cover them with layer of gravel. Similar method is adopted by Australian fresh water, Arius. In case of darters , sun fishes and cichlids males make shallow basin like dipressions on the bottom.

The male of N. American bowfin (Amia calva) constructs a crude circular nest of soft weeds and rootless amidst aquatic vegetation. Spawning takes place in the “weedy castle”. Sometimes later the young ones leave the nest in a swarm escorted by their watchful father. The male of N. American bowfin (Amia calva) constructs a crude circular nest of soft weeds and rootless amidst aquatic vegetation. Spawning takes place in the “weedy castle”. Sometimes later the young ones leave the nest in a swarm escorted by their watchful father.

The male of two-spinned stickle back builds an elaborate nest in fresh water, using twigs and weeds, fastened together by the threads of a sticky secretion from the kidney.

Nest building by female is rarely known. Female Heterotis has been shown to make nests in swamps. There are instances in which both the parents take part in nest building. Eg: Labrus Labrus.

Carrying the eggs on the body some fishes ensure protection to their eggs by carrying them safely either in the mouth or anywhere in the body. In Aspredo and Platystacus, the skin of the lower part of the female becomes smooth and spongy during breeding seasons. Fertilized eggs get attached to it.

 In some fishes like Arius and Tilapia mouth-brooding or buccal incubation is a characteristic property both the male and female carries eggs and young ones in their mouth. In oral incubation, the parent will not feed until young ones hatch out. male nursery fish krutus has a cephalic horn upon which female deposits grape like egg clusters.

Keeping the eggs in brood chambers in most species of Syngnathus, Hippocampus, siphonostoma, male has a brood pouch for the deposition of eggs. In Hippocampus, some sort of” placenta” may be formed for gas exchange between the father and the developing young ones. In syngnathus, brood pouch has a highly vascular spongy lining from which the developing young ones may draw nourishment. in unique pipe fish of Indian and pacific oceans, Salenostomus the inner side of the ventral fin of female coalesces with the integument forming a large pouch for keeping the eggs.

Coiling round the eggs The British gunnel or the butter fish has a peculiar way of parental care. The female roll the eggs to a ball and then curls around them. Often male may assist her in this process. Butter Fish.

Keeping the eggs in egg capsules Some chondrichthyes, gives maximum protection to eggs by enclosing them in an egg capsule. In Scyllium, Raja etc, fertilized eggs are kept in a specially designed horny egg capsule, popularly called “Mermaid’s purse”. Egg filled capsules get attached to aquatic weeds with the help of tendril like filaments. Development is completed inside the capsule, utilizing the yolk reserve. Young ones hatch out by breaking the capsule.

Oviposition means, act of laying or depositing eggs. It is mostly exhibited by central European bitterling. In this the genital papilla of the female serves as an ovipositor. With its help eggs may be introduced to the gill chamber of a pond mussel.  During this female takes to a vertical posture and spawning. Male swims around her and discharges sperms in to the mussel. Fertilization and development take place in the gill chamber and young ones leave the host later.

Several fishes provide maximum pre-natal protection to their embryos by adopting ovoviviparity. Here the development is internal and the special portion of the oviduct serves as an unspecialized uterus.  A true mammalian type of placenta is absent. Nutrition is given either by yolk reserve or the uterine milk which is secreted by uterine wall. Eg: for ovoviviparous chondrichthyes are scoliodon, sphyrna, pristis, stegastoma, squalus, mustelus, myliobatis, trygon pteroplatea,etc. Eg: for ovoviviparous osteichthyes are Gambusia,poicilia,blennis,allis,zoarces,cymogaster etc.

Freshwater habitats include both still and moving water. Living things within rivers and streams can travel through the water to different areas. Many underwater inhabitants of ponds and Lakes, however, cannot escape from what may be quite a small area of water. However, even a tiny pool may have a complete, self-contained ecosystem. As well as plants and fish, freshwater ecosystems support living things that visit the water but spend part of their lives on land, such as amphibians, birds and insects. Many mammals also spend time in and around the water. Finally, the kinds of wildlife found in freshwater ecosystems will be affected by the climate and landscape around it. For example, the crocodile may be the fiercest predator in an African river, but its place may be taken by an otter in a European stream.

Cast out your fishing line or scoop your net through the water. You are bound to catch something when you are along the river’s edge or at the lake. Catching fish is always exciting, but while you wait for that fish to come along.

Freshwater ecosystems include lakes, ponds, rivers, streams, springs, and wetlands. You will find them in many different sizes, from very small to very large. The water within the ecosystem can be still (not moving), like in a pond, or it can be running (moving), like a river or stream.

Freshwater ecosystems are broken into three zones: littoral, open water and deep water – we’ll talk more about these below. The plants and animals within the ecosystem interact with light, food, oxygen, weather, and climate in different ways.

Plants and animals grow in different zones in freshwater ecosystems. The littoral (or marsh) zone refers to the plants and animals that grow closest to the edge of the water. The plants in this area can make great hiding spots for animals to hide from predators. You might find snails, clams, or even eggs and larvae from reptiles and insects in this area. Common predators (animals who prey, or feed, on other animals) in this zone include snakes, ducks and swans.

The open water zone refers to plants and animals that live near the top of the water. Some float on top of the water and have tiny roots that go down into the water, like duckweed. Others have their roots down in the mud at the bottom of the pond and leaves that float at the top of the pond, like water lilies. These plants get lots of sunlight, which makes them the top energy producers for the animals in the water. Many fish also swim in this open water zone.

Freshwater ecosystems play a fundamental ecological role and provide economically important products and services. They provide critical habitats for a large number of aquatic plants, fishes, reptiles, birds and mammals. They host many migratory and threatened species of birds, reptiles and fish. The freshwater ecosystems are areas of tourist attraction by providing recreation sites for game and bird watching.

Freshwater ecosystems, especially vegetated wetlands, play an important role in mitigation against climate variability. They do so through a number of ecosystem functions including flood control, water purification, shoreline stabilization and sequestration of carbon dioxide. At landscape level, wetlands control soil erosion and retain sediments and in so doing concentrate nutrients in the wetland soil. They also provide economic benefits such as fresh water, fisheries, fuel-wood, building material, medicinal products, honey and foliage for livestock and wildlife. Wetlands provide fertile land for agricultural, mineral salts, sand and soil for making pottery and building bricks. Wetlands are central to rural subsistence economies and livelihood activities of many rural communities in Kenya. Freshwater ecosystems in general are critical to poverty alleviation and creation of employment and wealth.

Oceans offer various habitats at different depths below the surface. These are called zones. The euphotic zone is at the top, ending at a depth of about 200m (660ft). Below this, very little light from the Sun can reach. The bathypelagic zone below is totally dark, so no plants can live there, but a number of fish, squid and crustaceans do make this zone their home, feeding on waste material that sinks down from above and on each other. Deep-sea creatures cannot see in total darkness, but their other senses help them to find food. Some, such as angler fish, carry their own lights. They are not bright enough to search for food by, but they may lure other fish towards them and help fish of the same species to recognize each other.

When the ancestors of cave fish and certain crickets moved into pitch-black caverns, their eyes virtually disappeared over generations. But fish that ply the sea at depths greater than sunlight can penetrate have developed super-vision, highly attuned to the faint glow and twinkle given off by other creatures. They owe this power, evolutionary biologists have learned, to an extraordinary increase in the number of genes for rod opsins, retinal proteins that detect dim light. Those extra genes have diversified to produce proteins capable of capturing every possible photon at multiple wavelengths—which could mean that despite the darkness, the fish roaming the deep ocean actually see in color.

The finding “really shakes up the dogma of deep-sea vision,” says Megan Porter, an evolutionary biologist studying vision at the University of Hawaii in Honolulu who was not involved in the work. Researchers had observed that the deeper a fish lives, the simpler its visual system is, a trend they assumed would continue to the bottom. “That [the deepest dwellers] have all these opsins means there’s a lot more complexity in the interplay between light and evolution in the deep sea than we realized,” Porter says.

At a depth of 1000 meters, the last glimmer of sunlight is gone. But over the past 15 years, researchers have realized that the depths are pervaded by faint bioluminescence from flashing shrimp, octopus, bacteria, and even fish. Most vertebrate eyes could barely detect this subtle shimmer. To learn how fish can see it, a team led by evolutionary biologist Walter Salzburger from the University of Basel in Switzerland studied deep-sea fishes’ opsin proteins. Variation in the opsins’ amino acid sequences changes the wavelength of light detected, so multiple opsins make color vision possible. One opsin, RH1, works well in low light. Found in the eye’s rod cells, it enables humans to see in the dark—but only in black and white.

Salzburger and his colleagues searched for opsin genes in 101 fish species, including seven Atlantic Ocean deep-sea fish whose genomes they fully sequenced. Most fish have one or two RH1 opsins, like many other vertebrates, but four of the deep-se species stood apart, the researchers report this week in Science. Those fish—the lantern-fish, a tube-eye fish, and two spinyfins—all had at least five RH1 genes, and one, the silver spinyfin (Diretmus argenteus), had 38. “This is unheard of in vertebrate vision,” says K. Kristian Donner, a sensory biologist at the University of Helsinki.

To make sure the extra genes weren’t just nonfunctional duplicates, the team measured gene activity in 36 species, including specimens of 11 deep-sea fish. Multiple RH1 genes were active in the deep-sea species, and the total was 14 in an adult silver spinyfin, which thrives down to 2000 meters. “At first it seems paradoxical—this is where there’s the least amount of light,” Salzburger says.

While many fish swim in shoals, eating plankton as they flash through the water, others spend most of their time on the ocean bed. As the fish evolved, their eyes developed on the same side, so that both can see into the water above.

These quick-change artists have eyes on top of their heads, yet marvelously mimic the surfaces they sit on. This prompted Clayton Louis Ferrara to ask Weird Animal. Flatfish have eyes on the top of their heads, how do they see what’s going on the ocean floor?”

Flatfish, found all over the world, range from the angler fin whiff which is about three inches (eight centimeters) to the Pacific halibut, which can get up to around nine feet (three meters) long. This fish group includes species familiar to seafood lovers—not only halibut, but flounder, sole, and turbot.

All flatfish have eyes on the end of stalks, so they pop out of the head “kind of like the eyes we saw in cartoons—ba-boing!” 

Flatfish eyes can also move independently, widening their field of vision. Once flatfish eyes get the lay of the land, they message the brain, which in turn sends signals back to the skin. This organ contains color-changing cells such as melanophores, which either expand or contract according to the background the fish is trying to match.

For instance, expanding their cells would make their color darker. All this neurological relaying is “a pretty sophisticated thing to do,” Burgess says—not to mention it takes flatfish between two and eight minutes to blend in.

Even more impressive than how the eyes work is how they get on top of the head in the first place. Flatfishes don’t start out flat. They start out looking like regular fish, kind of diamond shaped, and “as larvae, the eyes are in regular position on each side,” As they develop “the eye begins to migrate, moving over the top of the head, eventually settling on one side or the other”. This also requires the bones in their heads to move.

The flatfish’s bones are pretty pliable at this point, like the soft spot on an infant’s skull, so “as the eye moves, the bones in the head warp in that direction,” An additional bone, found only in flatfish, develops right under the migrating eye, giving them that goofy asymmetrical look.

          The cheetah (Acinonyx jubatus) can reach 105km/h (68mph) when sprinting over a short distance. For animals, fast speed often means survival. It means outrunning predators or catching prey. In order to be fast, every physiological characteristic is important. The ratio of height and weight, flexibility, and respiratory functioning are all things that affect speed. This article identifies the fastest mammals in the world and what makes them so fast.

          The cheetah is the fastest mammal on earth and can reach speeds of 68 to 75 miles per hour (mph). Though not the best for endurance, they run in short burst of 60 seconds or so. This feline is built for speed. They have large nasal passages that lead to large lungs, even the heart is enlarged to allow for maximum oxygen in the blood. Cheetahs use their tail for balance and spend more time with their paws in the air than on the ground while running.

          The second fastest mammal on earth never runs on the ground. The Free-tailed bat soars through the nighttime air at 60 mph and it is their “free” or unattached tail that allows them to reach such speeds. They inhabit every continent except Antarctica.

          After the Free-tailed bat is the Pronghorn, a graceful antelope that reaches speeds of up to 55 mph. While this antelope cannot outrun a cheetah in a head to head race, it can run for longer periods of time. That makes this mammal the fastest over long distances and the fastest in the Western Hemisphere. They are native to North America and live in wide, open grasslands. Scientists believe the Pronghorn evolved such high speeds to outrun predators. They share some of the same physical features as the cheetah: enlarged nasal passages, lungs, and heart.

          Sharing the number 3 spot on the list of the fastest mammals is the Springbok, an African antelope. This animal reaches the same speeds as the Pronghorn, 55 mph, though it cannot sustain over long distances.

          Number 4 on the list is the Wildebeest, another species of antelope. These mammals run up to speeds of 50 mph which allows them to escape lions, hyenas, cheetahs and leopards. Although more than their speed, it is their herding behavior that helps protect them from predators. Every year, wildebeests make a long migration following the pattern of rainy and dry seasons.

          Most mammal babies develop inside their mothers until they are ready to be born. The exceptions are the monotremes, a small group of mammals found in Australia. Like most reptiles, they lay eggs rather than giving birth to live young. Perhaps the best known of these is the duck-billed platypus.

          Of course, the platypus isn’t really a mixture of these other creatures. It just looks like it! The platypus is a semi-aquatic mammal native to Australia (including Tasmania) and Papua New Guinea.

          Along with four species of echidna (a mammal that looks a bit like a porcupine), the platypus is one of only five species of monotremes in the world. Monotremes are mammals that lay eggs instead of giving birth to live young.

          The platypus has a bill like a duck, a tail like a beaver, the skin and feet of an otter, and venom like a snake. These features truly make the platypus one of the most unique creatures on Earth. In fact, when the platypus was first discovered hundreds of years ago, scientists at the time thought it was an elaborate hoax.

          The name “platypus” comes from the Greek word for “flat-footed.” The male platypus has special spurs on its hind feet that it can use to defend itself by injecting painful venom into a predator. Although the venom isn’t deadly to humans, it can cause severe pain.

          The platypus can walk and run on land, but it moves awkwardly. Its webbed feet and waterproof skin help it to live much of the time in the water, where it feeds on insects, shellfish, worms, and other small creatures at the bottom of bodies of water.

          The platypus is mostly nocturnal and can spend up to 10 hours at a time in the water, searching for food. When it’s done swimming, the platypus likes to live in a burrow dug into the bank of a nearby body of water.

          The female platypus lays one or two eggs each season. When a baby platypus emerges from its shell, it’s about the size of a lima bean. Its mother will take care of it for three months or so until it’s ready to head out into the world on its own.

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          Almost all mammal babies grow inside their mother until they are able to breathe and feed outside, but mammal babies differ very much in the kind of help they need after birth. Human babies, for example, need the attention of their parents for many years before they are able to fend for themselves completely. Most grazing animals, on the other hand, have adapted to life on wide, open grasslands, where they are constantly at risk from attack by predators. It is important that these animals give birth to young that can stand on their own feet and run from danger almost immediately.

          Spring is the perfect time for baby animals to be born! Many animals have babies in the spring since the warmer weather makes it is easier for them to find food to feed them. Warmer weather also makes it easier for small babies to survive. Polar bears, which live in climates that are always very cold, actually have their babies during the winter while they are hibernating. When spring comes and warms things up a little, a mother bear will bring her cubs out of their cozy den for the first time and teach them how to find food for themselves. Other kinds of bears and some other large mammals also have babies during the winter, since they can nurse their babies and not have to leave their den to find food.

          There are lots of different kinds of animals living on earth. That means that there lots of very different kinds of baby animals! Even though we usually think of babies as being small and helpless when they are first born, that isn’t true for all animals. Some animals are very large even when they’re first born. Sometimes even the smallest ones are able to live on their own without any help from their parents when they are born. Keep reading to learn about some different kinds of animals and different ways that their babies are born and cared for.

          Mammals are animals that have hair or fur, are warm-blooded, and feed their babies with milk. Mammals give live birth, meaning that their babies are born from the mother’s body instead of hatching from an egg. However, there are two animals that lay eggs but are still considered mammals! They are echidnas and platypuses. Humans, elephants, cats, mice, pigs, rhinoceroses, gorillas, and many other animals are all mammals. Some are huge and some are tiny.

          Marsupials such as kangaroos, koalas, wombats, and opossums are mammals, too! When baby marsupials are born, they are very tiny and not as well developed as other mammal babies. They live in a fur-lined pouch on the outside of their mother’s belly where they nurse (drink milk) and stay safe and warm until they are big enough to come out. Even after the babies can come out of their mother’s pouch, they will still ride around on her back while they grow and learn how to survive on their own. Marsupial babies are called joeys. Almost all marsupials are nocturnal, which means they are awake at night and sleep during the day. Australia is home to most kinds of marsupials, but opossums do live in other parts of the world. In fact, the only marsupial that lives in North America is the Virginia Opossum, which can have up to 13 babies at once!

          Reptiles are cold-blooded, have backbones, have skin covered with scales, have claws on their feet, and baby reptiles’ hatch from eggs. A few kinds of snakes and lizards give live birth to their babies, but most lay eggs. Reptiles are born looking like smaller versions of their parents and are on their own almost as soon as they hatch. Their parents do not stay around to take care of them, because they aren’t really needed.

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          Warm-blooded animals are able to control their internal temperature to a greater degree than cold-blooded animals, so that they are less dependent on the temperature of their surroundings. While reptiles slow down when the weather is cold, mammals are able to lead an active life. Mammals have adapted to life in all parts of the world where there is food for them to eat.

          Warm-blooded creatures, like mammals and birds, try to keep the inside of their bodies at a constant temperature. They do this by generating their own heat when they are in a cooler environment, and by cooling themselves when they are in a hotter environment. To generate heat, warm-blooded animals convert the food that they eat into energy. They have to eat a lot of food, compared with cold-blooded animals, to maintain a constant body temperature. Only a small amount of the food that a warm-blooded animal eats is converted into body mass. The rest is used to fuel a constant body temperature.

          Cold-blooded creatures take on the temperature of their surroundings. They are hot when their environment is hot and cold when their environment is cold. In hot environments, cold-blooded animals can have blood that is much warmer than warm-blooded animals. Cold-blooded animals are much more active in warm environments and are very sluggish in cold environments. This is because their muscle activity depends on chemical reactions which run quickly when it is hot and slowly when it is cold. A cold-blooded animal can convert much more of its food into body mass compared with a warm-blooded animal.

          To stay cool, warm-blooded animals sweat or pant to loose heat by water evaporation. They can also cool off by moving into a shaded area or by getting wet. Only mammals can sweat. Primates, such as humans, apes and monkey, have sweat glands all over their bodies. Dogs and cats have sweat glands only on their feet. Whales are mammals that have no sweat glands, but then since they live in the water, they don’t really need them. Large mammals can have difficulty cooling down if they get overheated. This is why elephants, for example, have large, thin ears which loose heat quickly. Mammals have hair, fur or blubber, and birds have feathers to help keep them warm. Many mammals have thick coats of fur which keep them warm in winter. They shed much of this fur in the summer to help them cool off and maintain their body temperature. Warm-blooded animals can also shiver to generate more heat when they get too cold. Some warm-blooded animals, especially birds, migrate from colder to warmer regions in the winter.

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          Most birds can fly, but there are also some flightless species. These all have other ways of escaping from predators. The larger flightless birds, such as ostriches and emus, can run very fast. Penguins cannot fly but can swim and dive at great speed, using their wings as flippers to power them through the water.

          Most birds fly. They are only incapable of flight during short periods while they molt, or naturally shed their old feathers for new ones. There are, however, several birds that do not fly, including the African ostrich, the South American rhea, and the emu, kiwi, and cassowary of Australia. The penguins of the Southern Hemisphere are also incapable of air flight. They have feathers and insulation for breeding purposes, but use a different form of motion: their sleek bodies “fly” through the ocean using flipper-like wings. All of these flightless birds have wings, but over millions of years of evolution they have lost the ability to fly, even though they probably descended from flying birds. These species may have lost their ability to fly through the gradual disuse of their wings. Perhaps they became isolated on oceanic islands and had no predators; therefore, they had no need to fly and escape danger. Another possibility is that food became plentiful, eliminating the need to fly long distances in search of food.

          No list of flightless birds would be complete without the penguin. All 18 species of penguin are unable to fly, and are in fact better built for swimming and diving, which they spend the majority of their time doing. Their short legs and stocky build give them a distinctive waddling walk. While people tend to associate penguins with Antarctica, most species live in higher latitudes. A few even live in temperate climates, and the Galapagos penguin actually lives at the Equator. These birds are also remarkably romantic—penguins are largely monogamous and seek out the same mates each season, even among the hundreds or even thousands of birds that might live in their colony.

          Three out of four species of steamer duck are flightless, but four out of four species should not be messed with. Even within the flighted species, some males are too heavy to actually achieve liftoff. These South American ducks earned their name by running across water and thrashing their wings like the wheels on a steamboat. They use them for other forms of thrashing, too. Famously aggressive, steamer ducks are known to engage in epic, bloody battles with each other over territory disputes. They have even been known to kill waterbirds several times their size.

          The Weka is another bird of New Zealand. This brown, chicken-sized bird was an important resource for native New Zealanders and European settlers, but is now decreasing in number. While they may look unremarkable, weka have a loud call that males and females sing as a duet. They’re also known as clever thieves and will steal food and small objects to their liking and make off with them. Weka are skilled swimmers, too.

          The kakapo, also known as an “owl parrot” is also a native of New Zealand. This nocturnal parrot has an owl’s face, penguin’s stance, and duck’s gait. It is truly a strange bird—but also a beautiful one, with bright green-brown feathers. It can grow up to 2 feet in length, and is the world’s heaviest parrot. The males make a distinctive booming call that sounds like a one-bird jug band, which can be heard up to half a mile away!

          The cassowary is a bird you don’t want to mess with. This giant bird, a native of Australia and the surrounding islands, is in the heavyweight class. The only bird heavier is the ostrich. As if that isn’t enough, the cassowary sports a wicked daggerlike claw that can grow up to 4 inches long on the middle toe of each foot —and they’ve been known to kill humans. If deadly power isn’t your thing, though, you can still admire the cassowary’s style. These birds sport colorful helmets, or casques, made of keratin (like human fingernails). And their plush back feathers kind of look like glamorous fur capes.

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          The ostrich, running in herds in southern Africa, is the largest bird in the world. As well as being able to run at enormous speed from danger, the ostrich has powerful legs and sharp claws, which can deliver a kick hard enough to kill many predators.

          The largest extant bird species, a member of the struthioniformes, is the ostrich (Struthio camelus), from the plains of Africa and Arabia. A large male ostrich can reach a height of 2.8 metres (9.2 feet) and weigh over 156 kilograms (344 pounds). A mass of 200 kg (440 lb.) has been cited for the ostrich but no wild ostriches of this massive weight have been verified. Eggs laid by the ostrich can weigh 1.4 kg (3.1 lb.) and are the largest eggs in the world today.

          The largest extant bird by wingspan is the Wandering Albatross of the sub-Antarctic oceans. The maximum dimensions in this species are a length of 1.44 m (4.7 ft.) and a wingspan of 3.65 m (12.0 ft.).

          The largest bird in the fossil record may be the extinct elephant birds of Madagascar, whose closest living relative is the kiwi. They exceeded 3 m (9.8 ft.) in height and 500 kg (1,100 lb.). The last of the elephant birds became extinct about 300 years ago. Of almost exactly the same upper proportions as the largest elephant birds was Dromornis stirtoni of Australia, part of a 26,000-year-old group called mihirungs of the family Dromornithidae. The largest carnivorous bird was Brontornis, an extinct flightless bird from South America which reached a weight of 350 to 400 kg (770 to 880 lb.) and a height of about 2.8 m (9 ft 2 in). The tallest bird ever however was the giant moa (Dinornis maximus), part of the moa family of New Zealand that went extinct around 1500 CE. This particular species of moa stood up to 3.7 m (12 ft) tall, but weighed about half as much as a large elephant bird or mihirung due to its comparatively slender frame.

          The heaviest bird ever capable of flight was Argentavis magnificens, the largest member of the now extinct family teratornithidae, found in Miocene-aged fossil beds of Argentina, with a wingspan up to 5–6 m (16–20 ft.), a length of up to 1.26 m (4.1 ft), a height on the ground of up to 1.5–2 m (4.9–6.6 ft.) and a body weight of at least 71 kg (157 lb.). Rivaling Argentavis in wingspan if not in bulk and mass, another contender for the largest known flying bird ever is Harpagornis moorei, which had a wingspan of up to 7.3 m (24 ft.).

          There are around 4000 species of mammal. Some spend their whole lives swimming in the ocean, while others never venture into the water. Most have fur or hair on their bodies at some time in their lives. Some walk on two legs and some on four. What all mammals have in common, however, is that they are warming blooded and breathe air. Mammal mothers feed their young on milk from their mammary glands. Mammals also have lungs, a heart with four chambers and well-developed brains.

Mammal, (class Mammalia), any member of the group of vertebrate animals in which the young are nourished with milk from special mammary glands of the mother. In addition to these characteristic milk glands, mammals are distinguished by several other unique features. Hair is a typical mammalian feature, although in many whales it has disappeared except in the fetal stage. The mammalian lower jaw is hinged directly to the skull, instead of through a separate bone (the quadrate) as in all other vertebrates. A chain of three tiny bones transmits sound waves across the middle ear. A muscular diaphragm separates the heart and the lungs from the abdominal cavity. Only the left aortic arch persists. (In birds the right aortic arch persists; in reptiles, amphibians, and fishes both arches are retained.) Mature red blood cells (erythrocytes) in all mammals lack a nucleus; all other vertebrates have nucleated red blood cells.

          Except for the monotremes (an egg-laying order of mammals comprising echidnas and the duck-billed platypus), all mammals are viviparous—they bear live young. In the placental mammals (which have a placenta to facilitate nutrient and waste exchange between the mother and the developing fetus), the young are carried within the mother’s womb, reaching a relatively advanced stage of development before birth. In the marsupials (e.g., kangaroos, opossums, and wallabies), the newborns are incompletely developed at birth and continue to develop outside the womb, attaching themselves to the female’s body in the area of her mammary glands. Some marsupials have a pouchlike structure or fold, the marsupial that shelters the suckling young.

          The class Mammalia is worldwide in distribution. It has been said that mammals have a wider distribution and are more adaptable than any other single class of animals, with the exception of certain less-complex forms such as arachnids and insects. This versatility in exploiting Earth is attributed in large part to the ability of mammals to regulate their body temperatures and internal environment both in excessive heat and aridity and in severe cold.

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          Birds show extraordinary variety and ingenuity in the nests they build. An untidy mound of sticks, simply dropped on top of one another, is all that a mute swan requires. House martins, on the other hand, literally build their homes. They skim over puddles and ponds, picking up little pieces of mud, which are built up into round-walled structures on the sides of buildings. Cuckoos, of course, are renowned for the fact that they use other birds’ nests in which to lay their eggs. They are able to mimic the size, shape and colour of the host-bird’s eggs to some extent, so that the additional egg is not immediately obvious.

          It should come as no surprise that hummingbirds, our smallest birds, make the smallest nests. Hummingbirds build on top of tree branches, using plants, soft materials and spider webs. Ruby-throats decorate theirs with flakes of lichen. Anna’s hummingbirds may lay eggs before a nest is completed, continuing to build the sidewalls during incubation. Most impressive is how these nests stretch. Hummingbirds usually lay a pair of eggs the size of black beans inside a nest about the diameter of a quarter. As the babies grow, the nest expands, keeping things tight and cozy.

          Orioles are the seamstresses of the bird world. Their iconic pendant nests dangle from outermost tree branches. The nests are impossible to miss among the barren winter branches and nearly as impossible to spot, surrounded by leaves, during the breeding season. Orioles use whatever material is available to stitch their bag nests: long grasses, twine, even horsehair. The nests are lined with soft materials such as plant fibers, feathers or animal wool. The Altamira oriole of extreme south Texas and Central America constructs one of the longest dangling nests, which can hang down more than 2 feet.

          It’s the exception rather than the rule, but a few species of birds get away with building hardly any nest at all! This doesn’t mean they are haphazard in their approach to laying eggs, though. Beach nesting birds (including black skimmers, many species of terns, and piping, Wilson’s and other plovers) lay eggs in shallow depressions scraped out in the sand. The remarkable thing about the eggs of these species is their cryptic camouflage coloration. Eggs are often speckles and match the sandy granules of the makeshift nests. Sometimes these birds will line the shallow scrape with shells or sand to add to the camouflage. As beaches get more developed, some of these beach nests have adapted to laying eggs on nearby rooftops.

          Huge colonies of murres and guillemots nest on rocky coastal cliffs. Most lack any structural nests, instead laying eggs that are extra pointy on one end. This shape helps the eggs pivot around the point instead of rolling over the edge. These ledge nesting sites are also more protected from predators. Cliff nesters aren’t found only on coasts. Lots of species, including condors, ravens and falcons, use cliffs, but they build stick nests in the crevices.

         Some waterbirds, including many ducks, nest in upland grasslands far from water. Others, such as loons, grebes, coots and gallinules, nest directly on top of the water. Eggs will sink, so the birds build floating platform nests out of cattails, reeds, other aquatic vegetation, or mud. They anchor the nests to emergent vegetation to conceal them and to keep them from drifting away.

          Holes in trees and cacti are nest cavities; underground nests are burrows. Burrowing owls in Florida will sometimes dig their own burrow, while the burrowing owls in the west usually rely on spots excavated by prairie dogs, badgers, tortoises or other diggers. Other underground nesters include bank swallows, belted kingfishers and Atlantic puffins.

          It is hard to say officially whoop lays the first eggs each year, but my pick for favorite nest is the great horned owls. Sure, many species can begin nesting in January in southern states, but it is still winter in the nothern states when great horned owls start incubating their eggs in nests made of sticks, often in trees. It’s essential that these owls get an early state on nesting, because the species is slow to hatch and fledge. It is remarkable to think of the owls sitting on eggs as snow piles up during frigid nights.

          The grand champion nest-builder is… the bald eagle! In 1963, an eagle’s nest near St. Petersburg, Florida, was declared the largest at nearly 10 feet wide, 20 feet deep and over 4,400 pounds. That nest was extreme; most bald eagle nests are 5 to 6 feet in diameter and 2 to 4 feet tall. Nest construction can take three months. Eagles typically use the same nest year after year, adding to it each season.

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          When they first hatch from the egg, baby birds are called nestlings. At this stage, many of them have no feathers. Blind and helpless, they are completely dependent on their parents for food and protection. As their feathers grow, they become fledglings, with open eyes and hearty appetites. When the fledglings have all their feathers and are strong enough, they are ready to learn to fly and begin to be independent.

          Fledging is the stage in a flying bird’s life between hatching or birth and becoming capable of flight. This term is most frequently applied to birds, but is also used for bats. For antiracial birds, those that spend more time in vulnerable condition in the nest, the nestling and fledging stage can be the same. For precocial birds, those that develop and leave the nest quickly, a short nestling stage precedes a longer fledging stage.

          All birds are considered to have fledged when the feathers and wing muscles are sufficiently developed for flight. A young bird that has recently fledged but is still dependent upon parental care and feeding is called a fledgling. People often want to help fledglings, as they appear vulnerable, but it is best to leave them alone. The USA National Phenology Network defines the phenophase (or life cycle stage) of fledged young for birds as “One or more young are seen recently departed from the nest. This includes young incapable of sustained flight and young which are still dependent on adults.”

          In many species, parents continue to care for their fledged young, either by leading them to food sources, or feeding them. Birds are vulnerable after they have left the nest, but before they can fly, though once fledged their chances of survival increase dramatically.

          One species, the ancient murrelet, fledges two days after hatching, running from its burrow to the ocean and its calling parents. Once it reaches the ocean, its parents care for it for several weeks. Other species, such as guillemots and terns, leave the nesting site while they are still unable to fly. The fledging behavior of the guillemot is spectacular; the adult leads the chick to the edge of the cliff, where the colony is located, and the chick will then launch itself off, attempting to fly as far as possible, before crash landing on the ocean.

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          Birds are specially adapted for flight, whether skimming short distances between branches or flying for weeks at a time above the oceans. The shape of their wings gives a clue to the kinds of flight they make. Birds’ bodies need to be light enough for flight. The large surface area of their wings pushes air downwards as they flap to lift the bird. At the same time, birds need immensely powerful chest muscles to move their wings. Feathers are the ideal covering —they are light but strong and flexible. In flight, they can lie flat against the bird’s body to reduce wind resistance.

          Flying is possible for birds because of their strength, speed, weight and the way their bodies are created with parts such as wings. These are adaptations, or special and different features, that are designed to help birds fly. There are many different birds with different ways of flying.

          When you look outside, you probably see lots of different birds flying and soaring from place to place. Their wings flap and help them to fly high in the air. Then, their wings spread out in a strong, straight line to continue soaring.

          Birds’ bodies are usually lighter in weight than other animals. This is a necessary adaptation that helps them fly. Gravity is an invisible force that pulls heavier objects down toward Earth more than lighter objects. Therefore, the light weight of birds makes it easier for them to move up into the air since less gravity is working against them.

          Birds’ weight is also focused toward the center of their bodies. They don’t have too much weight on the sides, front and back of their bodies. This gives them the balance they need to fly.

          Your bones are thick and heavy. However, birds’ bones are hollow, or empty, on the inside, which causes less weight. They also have very light feathers. Mother birds lay eggs instead of carrying babies in their bodies, which helps them to stay lighter in weight as well. Additionally, birds have beaks instead of heavy teeth and noses; this also helps to reduce their weight.

          Have you ever walked around with a heavy, full stomach from eating too much? This causes you to feel heavier. Birds, on the other hand, eat lightweight foods such as berries, seeds and light meats that digest very quickly. Their bodies also get rid of wastes quickly so that they’re not too weighed down to fly.

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          Some male and female birds of the same species have very different plumage, with the male usually being more brightly coloured to attract females. Other species show little or no difference between the sexes. As well as having different plumage, birds may make displays to each other during the breeding season. Some dance in elaborate curving patterns, spread their feathers and strut, or sing. Male birds may fight to defend their territories during nesting.

          Once a budgie is a few weeks old, you will be able to tell the sex of the bird by looking at its cere (the nose and nostril area). In normal circumstances, a hen’s is brown, and a cock’s is blue. The hen’s cere becomes enlarged and scaly during the breeding season, and the male’s becomes a darker shade of blue. Simple!

          But there are a few complications. Hens sometimes have a light blue cere, when their breeding hormone levels are low. It will also be this colour, or white with just a hint of blue, if the bird is ill. In the wild the female’s cere is light blue, turning brown during the nesting season. In young hens, the cere is a light blue with white around the nostrils.

          Cock birds, although nearly always sporting a blue cere, may have a brown or brownish-pink one if his breeding hormones dip, or if he is ill. An ill male may develop a yellow-greenish tinge around the nostrils too. In immature cock budgies the cere is a blueish pink or light purple.

          Some budgie types are harder to sex. Albino, Lutino and Mottled birds, for example, have off-white, light pink or bluish pink ceres, and males of some of the pied varieties have light pink, blueish pink or white ones. With hundreds of variations on the basic types mentioned in the Budgie types section , there is always a chance that your bird will have an ‘ambiguous’ cere colour. In 90% of cases, however, the brown-or-blue rule applies.

          In spite of these complications, cere colour is still the easiest way of sexing budgies. There are a few gender-related differences in voice and behaviour, too; but these are not as consistently ‘male’ and ‘female’ as cere colour. If you inherit an adult bird of unknown sex and with an ambiguous cere, watch out for bonding behaviour – any excessive head-bobbing is likely to be a male and any excessive squawking, rather than chirruping and singing, is probably female.

          Many snakes throw themselves along the ground in waves that pass from head to tail. They have hundreds of pairs of ribs and strong muscles to enable them to do this, while their scales grip the ground. North American sidewinders, however, move as their name suggests, by throwing their coils sideways along the ground. Snakes have four ways of moving around.  Since they don’t have legs they use their muscles and their scales to do the “walking”.

Serpentine method:  This motion is what most people think of when they think of snakes.  Snakes will push off of any bump or other surface, rocks, trees, etc., to get going.  They move in a wavy motion.  They would not be able to move over slick surfaces like glass at all.  This movement is also known as lateral undulation.

Concertina method:  This is a more difficult way for the snake to move but is effective in tight spaces.  The snake braces the back portion of their body while pushing and extending the front portion.  Then the snake drops the front portion of their body and straightens a pulls the back portion along.  It is almost like they through themselves forward.

Sidewinding: This is a difficult motion to describe but it is often used by snakes to move on loose or slippery surfaces like sand or mud.  The snake appears to throw its head forward and the rest of its body follows while the head is thrown forward again.  (See picture.) 

Rectilinear Method:  This is a slow, creeping, straight movement.  The snake uses some of the wide scales on its belly to grip the ground while pushing forward with the others.

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          It is likely that birds evolved from reptiles. Like reptiles but unlike most mammals, they lay eggs that hatch outside the mother. All adult birds have feathers, rather than fur or scales, and most can fly. However, birds are similar to mammals in being warsm blooded.

          When one thinks of the differences between mammals and birds, the first thing that comes to mind is that mammals give birth to their young whereas birds lay eggs. Now let us look at other differences between mammals and birds. The birds have feathers whereas mammals have only fur or hair. This feature is one of the main features of birds that differentiate them from mammals. Birds use feathers for controlling body temperature, flying, and attracting the opposite sex.

          As birds need to fly, they have porous or hollow bones. In contrast, mammals have denser bones. Birds have wings although mammals have paws, hands, and hooves. There is also a difference in the feeding of the young. Mammals feed their young milk produced by the mammary glands. On the other hand, young birds are fed by the parents regurgitating partially digested food.

          Birds and mammals have a larynx. The mammals produce sounds using the larynx. In birds, this organ does not produce sounds. Instead of using the larynx for sound, birds have a syrinx which serves as a voice box. The lungs of birds do not expand or contract as that of the lungs of mammals. In mammals, the oxygen and carbon dioxide is exchanged in the alveoli which are microscopic sacs in the lungs. In birds, the exchange happens in air capillaries which are walls of microscopic tubules. While there is only a single respiratory cycle in mammals, there are two cycles in birds.

          Now comparing the blood, birds have a nucleus in the RBS whereas it is not generally seen in mammals. If there is a nucleus in the RBS in mammals, then it is a sign of sickness. The RBS of birds are oval in shape whereas most of the mammals’ RBSs have a round shape.

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          The chameleon is able to change colour to match its surroundings by releasing or tightening special cells on its skin. As well as this remarkable ability, chameleons are amazing in other ways. They are able to grip very strongly with their toes and tails to balance on precarious branches. Their extraordinary tongues, which are able to shoot out as far as the chameleon’s body length, are sticky and able to scoop back prey like a piece of elastic. Finally, the chameleon’s eyes are bulging and can move in any direction, protected by an eyelid that is fused all-round the eye, leaving only a tiny hole in the middle. Even stranger, the chameleon can move each of its eyes in a different direction at the same time!

          Chameleons are famous for their quick color-changing abilities. It’s a common misconception that they do this to camouflage themselves against a background. In fact, chameleons mostly change color to regulate their temperatures or to signal their intentions to other chameleons. Since chameleons can’t generate their own body heat, changing the color of their skin is a way to maintain a favorable body temperature. A cold chameleon may become dark to absorb more heat, whereas a hotter chameleon may turn pale to reflect the sun’s heat.

          Chameleons will also use bold color changes to communicate. Males become bright to signal their dominance and turn dark in aggressive encounters. Females can let males know if they’re willing to mate by changing the color of their skin. Owners of chameleons can learn to read their pet’s mood based on the color of its skin.

          So how do they pull off these colorful changes? The outermost layer of the chameleon’s skin is transparent. Beneath this are several more layers of skin that contain specialized cells called chromatophores. The chromatophores at each level are filled with sacs of different kinds of pigment. The deepest layer contains melanophores, which are filled with brown melanin (the same pigment that gives human skin its many shades). Atop that layer are cells called iridophores, which have a blue pigment that reflects blue and white light. Layered on top of those cells are the xanthophores and erythrophores, which contain yellow and red pigments, respectively.

          Normally, the pigments are locked away inside tiny sacs within the cells. But when a chameleon experiences changes in body temperature or mood, its nervous system tells specific chromatophores to expand or contract. This changes the color of the cell. By varying the activity of the different chromatophores in all the layers of the skin, the chameleon can produce a whole variety of colors and patterns.

          For instance, an excited chameleon might turn red by fully expanding all his erythrophores, blocking out the other colors beneath them. A calm chameleon, on the other hand, might turn green by contracting his erythrophores and allowing some of the blue-reflected light from his iridophores to mix with his layer of somewhat contracted yellow xanthophores.

          With these layers of cells, some chameleons are capable of producing a dazzling array of reds, pinks, yellows, blues, greens, and browns. These bold statements won’t help them blend into the background, but they will allow them to get their message across to other chameleons loud and clear.

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          Both crocodiles and alligators spend most of their lives in swamps and rivers in warm climates, although they breathe air through nostrils on the top of their snouts, closing these off when they dive. Caymans and gavials are relatives of crocodiles and alligators. The simple way of telling them apart is that crocodiles show the fourth tooth in their lower jaw when their mouths are closed, while alligators do not. It is probably not wise to go near enough to a live crocodilian to find out, however, as they have been known to attack humans!

          Coming face to face with a crocodile or an alligator, you’d see a mouth full of serrated teeth that would likely scare the bejeezus out of you. The two reptile groups are close relatives, so their physical similarities are expected. Upon closer inspection, not recommended out in the wild, you’d spot glaring differences:

          Snout shape: Alligators have wider, U-shaped snouts, while crocodile front ends are more pointed and V-shaped. Toothy grin: When their snouts are shut, crocodiles look like they’re flashing a toothy grin, as the fourth tooth on each side of the lower jaw sticks up over the upper lip. For alligators, the upper jaw is wider than the lower one, so when they close their mouths, all their teeth are hidden.

          Home base: Crocodiles tend to live in saltwater habitats, while alligators hang out in freshwater marshes and lakes. They belong to the subgroup Eusuchia, which includes about 22 species divided into three families: the fish-eating gavials or gharials, which belong to the Gavialidae; today’s crocodiles or the Crocodylidae; and the Alligatoridae, or alligators. Eusuchians appeared on the scene during the late Cretaceous some 100 million or so years ago.

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          Reptiles are cold blooded, so must gain warmth from their surroundings. This means that they can be found anywhere except in the very coldest regions of the Earth. Those that live in cooler areas usually spend the winter hibernating. Most reptiles lay eggs with hard or leathery shells. Their young hatch into miniature versions of their parents, but as reptiles can continue to grow after they are mature, some reach an enormous size.

          The term “reptile” is derived from a Latin word meaning “creeping animals.” These animals include snakes, lizards, crocodiles, caimans, alligators, turtles, geckos, and chameleons, with lizards and snakes species making up the majority of all reptiles. Reptiles are cold-blooded animals which mean they are unable to regulate their own body temperature. The first reptiles evolved approximately 320 million years ago from the advanced four-limbed vertebrates known as reptiliomorph. These early reptiles became adapted to life on dry land. Reptiles have diverse ways of defending themselves from danger including biting, hissing, camouflaging, and avoidance. This article focuses on some of the most outstanding characteristics of reptiles.

          Most reptiles reproduce sexually while others are capable of reproducing asexually. The reproduction activities take place through the cloaca located at the base of the tail. Copulatory organs can be seen in most reptiles which are often stored inside their bodies. Male turtles and crocodiles have a penis while lizards and snakes have a pair of hemipenes. Other species like the tuatara do not have copulatory organs hence mating is through the pressing together of the cloaca. After successful copulation, the female reptile lays eggs which are covered with a shell. The eggshell protects and keeps the embryo from drying out and allows for the exchange of gasses. The egg contains chorion which aids in gaseous exchange, the albumen which is a reservoir for protein and water, and the amniotic fluid which protects embryo and aids in osmoregulation. Some reptiles incubate the eggs by laying on them while others bury them in the sand until they hatch.

          Most reptiles are cold-blooded vertebrates. They do not have the psychological means of regulating their body temperatures and have to depend on the external environment. Other species exhibit a mix of ectothermy, poikilothermy, and brandymetabolism. Reptiles often bask in the sun or hibernate during cold seasons to raise their body temperatures. When the sun is too hot, they will retreat to shady areas or inside the water to cool or lower their body temperatures. Because reptiles have unstable body temperature, their metabolism requires enzymes that are capable of maintaining efficiency over a range of temperatures. It is assumed that reptiles cannot produce enough energy required for long-distance chase like the warm-blooded animals. However, it remains unclear as to whether their cold-bloodedness is as a result of their ecology or not.

          Reptiles have either four legs, or some like snakes, are descendants of four-limbed ancestors. In most snakes, all traces of legs including bones for the legs have disappeared. However, they still remain successful predators even without the legs. Snakes have three ways of moving on land; straight crawling, lateral undulating, and sidewinding. Although lizards have four limbs, most lizards have an alternating gait which limits their endurance. The tail of some lizards is prehensile and can assist them in climbing. Some reptiles like crocodiles have claws on their feet. These claws assist in movement and hunting.

          Reptiles exhibit similar characteristics of other vertebrates like mammals, birds, and some amphibians. They have backbones that house the spinal cords that run the length of their bodies. Reptiles also have chains of bony elements from the tail to the head. The bony endoskeleton consists of cranium or skull, appendages, and limb girdles. The endoskeleton protects the inner tissue and also aids in body movement. Skeletons differ from one species to another, with crocodiles having some of the largest body structures in this class.

There are four orders of reptile, by far the largest of which is the order of lizards and snakes. There are nearly 6000 different species of these. The other orders are much smaller. There are about 200 species of turtles, tortoises and terrapins, and only just over 20 species of crocodiles and alligators. Rarest of all is the tuatara, which forms an order all by itself.

Reptiles are tetrapod animals belonging to the class Reptilia, which includes turtles, snakes, crocodilians, tuatara, lizards, and amphisbaenians. Reptiles likely originated more than 312 million years ago, when the first species evolved from the advanced reptiliomorph tetrapods. Today, animals belonging to class reptilian range in size from tiny geckos to huge saltwater crocodiles that measure more than 19 feet in length. There are approximately 10,700 extant reptile species.

The Reptile Database is a database that lists all living reptiles and their classifications. It also contains images for most reptiles on the list. There are more than 10,700 extant species of reptiles recorded in the Reptile Database, making reptiles one of the most diverse types of vertebrates in the world. Compared to other species, only birds and fish have more types of species than reptiles. Additionally, there are approximately 5,000 and 7,000 species of mammals and amphibians, respectively.

Reptiles form part of the domain Eukaryote, which consists of organisms that have a nucleus within membranes. They are also included in the kingdom Animalia, which are organisms that ingest food and are multicellular. Reptiles are further classified as Chordate because of the presence of a spinal cord running the length of their back. As Chordate with backbones, they belong to subphylum Vertebrata and class Reptilian. There are four major groups of reptiles: Crocodilian, Squamata, Sphenodonita, and Testudines.

Crocodilia

The order Crocodilian is a subclass of Archosauria and contains some of the largest reptiles including crocodiles, caimans, alligators, and gavials. Reptiles in this order are mainly carnivores and typically inhabit tropical and subtropical rivers, swamps, and streams. They have strong jaws which facilitate a powerful bite, advanced brains, and greater intelligence than other reptiles.

Squamata

The Squamata order contains terrestrial reptiles such as snakes and lizards. There are approximately 3,750 species of lizards and 3,000 species of snakes. These animals have the ability to crawl or creep using their abdomen. They possess skin covered with horny scales that are periodically shed. Although snakes do not have legs, they evolved from four-legged ancestors.

Sphenodontia

Sphenodotia is the least specialized group of reptiles, with brains similar to those of amphibians. The best-known sphenodontite is the tuatara, which is a species that has a wedge-like skull with primitive eyes and socketless teeth. The lizard-like creature lives primarily in New Zealand.

Testudines

There are approximately 250 species belonging to the order Testudines, which are primarily turtles and tortoises. The species are four-legged and have a hard shell covering most parts of the body. They are mainly aquatic and are the oldest living reptiles in the world.

          Amphibians have a wide range of ways of protecting themselves. Some brightly coloured amphibians produce poisons in glands on their skins. The bright colours warn birds and animals not to attempt to eat them. Others use camouflage, blending with their surroundings, to prevent enemies from spotting them. Some frogs and toads puff themselves up or stand on tiptoes to look larger than they really are!

          Frogs, salamanders, snakes, and other herps are often small and live on the ground or in the water. Because of these characteristics, they are vulnerable to being preyed on by all kinds of carnivorous animals. In order to avoid being eaten, herps use a variety of strategies and protective mechanisms. As a first line of defense, most herps try to avoid being seen by their predators. Many are nocturnal and use the cover of darkness to avoid notice. During the day, most herps tend to remain hidden beneath dead leaves, rocks, and logs, or in underground burrows.

          Herps also avoid confrontation through camouflage. Using a variety of grays, greens, and browns, these animals can blend remarkably well into the background of their natural environment. It is amazing how difficult it is to see a smooth green snake that is moving through the grass!

          Countershading is an interesting form of camouflage for herps that live in the water. Many turtles, frogs, and salamanders have light colors on their bellies and dark colors on their backs. This color pattern makes them less visible to aquatic predators that see them against a light sky. Birds and other predators hunting from above also have a hard time spotting them against the dark water. Even some of the larger predators, such as snapping turtles and alligators, have countershading, perhaps to be less visible when stalking their prey.

          A lot of species use spots, stripes, and blotches to break up the outline of their bodies when viewed against leaves or soil. The distinctive “x” on the back of the spring peeper is an example of a mark that allows this frog to virtually disappear when on the ground or perched on a blade of grass. Unlike animals that use camouflage, the colors of these animals do not necessarily blend with the background. In fact, many times the markings are quite bright and even gaudy. The eyes of the predator, however, are tricked into thinking the shape they are seeing is not an animal.

          Some herps do not avoid or hide from predators, but instead frighten them off by displaying warning signs. For example, toads and newts have glands in their skin that produce toxins. In order for this toxicity to protect an animal from being eaten, the predators must be reminded that they are about to eat something that will make them sick. A common method of alerting a predator is by being very brightly colored. This explains why the young newts, or efts, that we see walking around the forest are bright orange and yellow. Their color is a vivid advertisement of their toxicity. Other common examples of this aposematic, or warning, coloration are the brightly banded, venomous coralsnakes and the very decorative, poison dart frogs of Central America.

          Interestingly, a herp truly may be poisonous or it may be just bluffing. Some harmless herps have adapted their appearance to mimic that of a more poisonous relative. In this way, they take advantage of markings that bring back unpleasant memories for predators. Such mimicry may protect the brightly colored, red-backed salamander from would-be predators, even though it is not toxic like the similarly colored eastern newt. Some snakes also mimic their poisonous relatives as a means of defense. The nonpoisonous scarlet king snake looks remarkably like the venomous coral snake, both of which are found in the same region.

          Finally, many herps scare off potential predators with threatening postures orbehaviors. Snapping turtles, when encountered on land, can be very aggressive, snapping their jaws and lunging. Probably the most notorious warning among herps is the very d a nearby rattlesnake is enough to make most animals halt in their tracks and mistinctive and chilling sound of a rattlesnake’s tail. The mere suggestion of ake a hasty retreat. Some snakes will rise up as if poised to strike an attacker. This act also has the advantage of making them appear larger and perhaps more threatening.

          The hog-nosed snake, a common resident of the coastal plain, uses a complicated set of behaviors when it is attacked. It first elevates its head and spreads out the skin of its neck in an effort to look bigger and more threatening. If this doesn’t scare off a predator, the hog-nosed snake begins to writhe upside down. It then regurgitates a foul smelling liquid and finally becomes rigid. It holds this position for several minutes, until the predator becomes disinterested and moves off.

          The red-eyed tree frog lives in the rain-forests of South America. Although it can swim, it spends much of its life out of water, among the leaves of trees where there are plentiful insects for food. The tree frog’s toes have sticky pads that enable it to grip branches as it climbs.

          Tree frogs are a diverse family of amphibians that includes over 800 species. Not all tree frogs live in trees. Rather, the feature that unites them has to do with their feet—the last bone in their toes (called the terminal phalanx) is shaped like a claw. Tree frogs also have toe pads to help them climb and many have extra skeletal structures in their toes. Tree frogs can be a variety of colors, but most of the species found in the United States are green, gray, or brown. Some of them, like the squirrel tree frog (Hyla squirella), are chameleon-like in their ability to change color.

          Although tree frogs can grow to be a range of sizes, most arboreal species are very small because they rely on leaves and slender branches to hold their weight. At 4 to 5.5 inches (10 to 14 centimeters) long, the white-lipped tree frog (Litoria infrafrenata) from Australia and Oceania is the largest tree frog in the world. The largest tree frog in the United States is the non-native Cuban tree frog, which reaches 1.5 to 5 inches (3.8 to 12.7 centimeters) in length. The world’s smallest tree frogs are less than an inch (2.5 centimeters) long!

          Tree frogs are found on every continent except Antarctica, but they’re most diverse in the tropics of the western hemisphere. About 30 species live in the United States, and over 600 can be found in South and Central America. Not surprisingly, lots of tree frogs are arboreal, meaning they live in trees. Special adaptations like toe pads and long legs aid them in climbing and jumping. Non-arboreal tree frogs find habitats in lakes and ponds or among moist ground cover.

          Tree frogs are consumed by many different carnivorous animals. Mammals, reptiles, birds, and fish all eat tree frogs. Many of the frogs rely on camouflage to protect themselves from predators, and the more arboreal species escape ground-dwelling predators by hiding in trees. Adult tree frogs are insectivores that eat flies, ants, crickets, beetles, moths, and other small invertebrates. However, as tadpoles, most of them are herbivores.

          Almost all male frogs attract mates with advertisement calls. Each frog species has its own call so female frogs can listen for potential suitors of their own species. The frog call that most people are familiar with—“Ribbet!”—belongs to the Baja California tree frog (Pseudacris hypochondriaca). The ribbeting call has been incorporated into outdoor scenes of many Hollywood movies, even outside of the frog’s range.

          Some frogs hatch as miniature adults. More commonly, however, tadpoles emerge from frog eggs. As tadpoles mature, they lose their tail and grow legs until they eventually reach their adult form. The lifespan of tree frogs varies among species. Some of them are long-lived, such as the Australian green tree frog (Litoria caerulea), which is often kept in captivity for upward of 15 years. Species with lifespans of less than three years are considered short-lived. North America’s gray tree frogs (Hyla versicolor and Hyla chrysoscelis) are somewhere in the middle with a lifespan of five to nine years.

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          In ancient times, it was believed that salamanders could live in the middle of fires, as the cold of their bodies extinguished the flames around them. Of course, this is quite untrue, but the story may have come about because salamanders were often seen to run out of logs thrown onto the fire.

          In the first century AD, Roman naturalist Pliny the Elder threw a salamander into a fire. He wanted to see if it could indeed not only survive the flames, but extinguish them, as Aristotle had claimed such creatures could. But the salamander didn’t … uh … make it.

          Yet that didn’t stop the legend of the fire-proof salamander (a name derived from the Persian meaning “fire within”) from persisting for 1,500 more years, from the Ancient Romans to the Middle Ages on up to the alchemists of the Renaissance. Some even believed it was born in fire, like the legendary Phoenix, only slimier and a bit less dramatic. And that its fur (huh?) could be used to weave fire-resistant garments.

          Part of the problem, it seems, is that in addition to disproving the salamander’s powers, Pliny also wrote extensively that it had such powers—and then some. His Natural History, which has survived over the centuries as a towering catalog of everything from mining to zoology, describes the salamander as such: “It is so chilly that it puts out fire by its contact, in the same way as ice does. It vomits from its mouth a milky slaver [saliva], one touch of which on any part of the human body causes all the hair to drop off, and the portion touched changes its color and breaks out in a tetter,” a sort of itchy skin disease.

          Some 500 years later, Saint Isidore of Seville wrote that while other poisonous animals strike their victims individually, the salamander slays “very many at the same time; for if it crawls up a tree, it infects all the fruit with poison and slays those who eat it; nay, even if it falls in a well, the power of the poison slays those who drink it.” He also confirmed that it’s immune to the effects of fire.

          So right away the salamander was mythologized as both a miraculous survivor and a menace. Indeed, later on in the 1200s, an English writer told of one laying waste to Alexander the Great’s army simply by swimming in a river they drank from. All told, 4,000 soldiers and 2,000 horses supposedly perished after consuming the salamander’s dirty bath water. Which would be pretty embarrassing, if only it were true.

          Now, it was likely Europe’s fire salamander, with its vivid yellow-on-black coloration, that served as the inspiration for the legend, according to Nosson Slifkin in his book Sacred Monsters. As you might assume from its conspicuous colors, this species is in fact quite poisonous, secreting a neurotoxin to deter predators. And if it doesn’t feel like waiting to be attacked, it can actually fire this secretion at its approaching enemies. While the toxin can cause skin irritation in humans, it’s far from capable of poisoning 4,000 soldiers. But it’s likely this poisonous nature was simply scaled up for such myths.

          A few centuries later, none other than Leonardo Da Vinci added another curious characteristic to the salamander’s repertoire, claiming it “has no digestive organs, and gets no food but from the fire, in which it constantly renews its scaly skin.” The alchemist Paracelsus later confirmed this as its diet, elevating the salamander to the status of one of the four “elementals” that he substituted for the classical elements earth, fire, air, and water—the salamander of course being fire.

          Most amphibians lay their eggs in water. Frogs’ eggs are called spawn. They are protected from predators by a thick layer of jelly. Inside this a tadpole develops. When it hatches out, it is able to swim, using its long tail, and breathes through gills. As the tadpole grows, first hind legs and then fore legs begin to grow. Lungs develop, and the young frog is able to begin to breathe with its head above water. Gradually, the tail shortens until the young frog resembles its adult parents.

          In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Frogs, toads, and newts all hatch from the eggs as larvae with external gills but it will take some time for the amphibians to interact outside with pulmonary respiration. Afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges.

          Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin, which counteracts its effect. Specific events are dependent on threshold values for different tissues. Because most embryonic development is outside the parental body, development is subject to many adaptations due to specific ecological circumstances. For this reason tadpoles can have horny ridges for teeth, whiskers, and fins. They also make use of the lateral line organ. After metamorphosis, these organs become redundant and will be resorbed by controlled cell death, called apoptosis. The amount of adaptation to specific ecological circumstances is remarkable, with many discoveries still being made.

          Egg Stage: Amphibian eggs are fertilized in a number of ways. External fertilization, employed by most frogs and toads, involves a male gripping a female across her back, almost as if he is squeezing the eggs out of her. The male releases sperm over the female’s eggs as they are laid. Another method is used by salamanders, whereby the male deposits a packet of sperm onto the ground. The female then pulls it into her cloaca, a single opening for her internal organ systems. Therefore, fertilization occurs internally. By contrast, caecilians and tailed frogs use internal fertilization, just like reptiles, birds, and mammals. The male deposits sperm directly into the female’s cloaca.

          Larval stage: When the egg hatches, the organism is legless, lives in water, and breathes with gills, resembling their evolutionary ancestors (Fish). During the larval stage, the amphibian slowly transforms into an adult by losing its gills and growing four legs. Once development is complete, it can live on land.

          Toads and frogs are similar in many ways, although toads usually have rougher, drier skins and may waddle rather than hopping as frogs do. Some toad spawn is produced in strings, like necklaces, rather than the mass of eggs laid by a frog. While these little amphibians might look very similar at first glance, there are actually a plethora of key differences between them. Frogs and toads may seem similar, but they are quite different. There are many physical differences, such as differences in skin, color, and body type. There are also differences in behavior. A frog will need to be in close proximity to a body of water, for instance, while a toad can be further away. Frogs also tend to hop higher than toads.

          If there was ever a tell-tale sign to indicate which amphibian you are looking at, it’s the texture of their skin. Toads are warty-looking, covered in little lumps and bumps, while Frogs are sleek and smooth. Toads also virtually always have dry skin, whereas frogs look wet even when they are out of the water.

          If you’ve spotted an amphibian making its way along a pavement or ambling through some grass, chances are it’s a toad. Toads cope much better with dry conditions than frogs, as their skin is more waterproof. Frogs lose moisture a lot more easily, and so are rarely seen too far away from water, which explains why they always look moist.

          Frogs have long legs, longer than their head and body, which are made for hopping. Toads, on the other hand, have much shorter legs and prefer to crawl around rather than hop. Frogs are lithe and athletic-looking, whereas toads are somewhat squat and dumpy. Their faces are different too; frogs have a pointed nose while toad noses are much broader. Spawn is another key indicator for which species you’re looking at. Frog spawn is laid in gooey clumps, whereas toads spawn floats in stringy lengths. Like their adult counterparts, frog tadpoles are slimmer whereas toad tadpoles are chunky. Frog tadpoles are also covered in gold flecks, while toad tadpoles are plain black in colour.

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          Amphibians have different life cycles. Many live mainly on land, but most of them spend at least some of their lives in water. Frogs, toads, newts and salamanders are all amphibians. Frogs and salamanders are able to breathe through their damp skins to a certain extent, both in the water and on land, but toads must rely largely on their lungs and cannot remain in water for long.

          Amphibians! In order for water-dwelling animals to adapt to life on land, many new adaptations had to take place. First, they needed to be able to breathe air instead of obtaining oxygen from water. And fins don’t work well as legs! They needed to be able to move around well on land.

          What group of animals begins its life in the water, but then spends most of its life on land? Amphibians! Amphibians are a group of vertebrates that has adapted to live in both water and on land. Amphibian larvae are born and live in water, and they breathe using gills. The adults live on land for part of the time and breathe both through their skin and with their lungs as their lungs are not sufficient to provide the necessary amount of oxygen.

          There are approximately 6,000 species of amphibians. They have many different body types, physiologies, and habitats, ranging from tropical to subarctic regions. Frogs, toads, salamanders, newts, and caecilians are all types of amphibians.

          Most amphibians live in fresh water, not salt water. Their habitats can include areas close to springs, streams, rivers, lakes, swamps and ponds. They can be found in moist areas in forests, meadows and marshes. Amphibians can be found almost anywhere there is a source of fresh water. Although there are no true saltwater amphibians, a few can live in brackish (slightly salty) water. Some species do not need any water at all, and several species have also adapted to live in drier environments. Most amphibians still need water to lay their eggs.

          A very few fish give birth to live young, but most lay their eggs in the water, which is called spawning. A fish may lay millions of eggs, only a small proportion of which will grow into adults. A few fish, such as salmon and sticklebacks, build nests underwater to protect their eggs. They lay fewer eggs because more young survive. Dogfish and skates protect their eggs in black capsules. The empty capsules are often washed up on the beach, and it is these that are known as “mermaid’s purses”.

          Perhaps you’ve found a “mermaid’s purse” on the beach. Mermaid’s purses blend really well with seaweed, so you may also have walked right by one. Upon further investigation, you can learn more about what they are. The enchantingly named structures are the egg cases of skates and some sharks. This is why they are also known as skate cases.

          While some sharks bear live young, some sharks (and all skates) release their embryos in leathery egg cases that have horns and sometimes long tendrils at each corner. The tendrils allow them to anchor to seaweeds or other substrates. Each egg case contains one embryo. The case is made up of a material that is a combination of collagen and keratin, so a dried egg case feels similar to a fingernail. 

          In some areas, such as in the Bering Sea, skates seem to lay these eggs in nursery areas. Depending on the species and sea conditions, the embryo may take weeks, months or even years to fully develop. When they hatch out of one end, the baby animals look like miniature versions of their skate or shark parents. 

          If you find a mermaid’s purse on the beach or are lucky enough to see a “live” one in the wild or in an aquarium, look closely — if the developing skate or shark is still alive, you may be able to see it wiggling around. You also may be able to see it if you shine a light through one side. The egg cases on the beach are often light and already opened which means the animal inside has already hatched and left the egg case. 

          Mermaid’s purses usually get washed or blown to the high tide line of the beach, and they often get wrapped up in (and blend in well with) seaweeds and shells. As you’re walking along the beach, walk in the area where shells and ocean debris seems to have washed up, and you might be lucky enough to find a mermaid’s purse. You may be more likely to find one after a storm. 

          All sharks are carnivorous (meat-eaters), and a few species, such as the white shark, which can grow to 9m (30ft), have been known to attack humans or even boats. But 90% of all shark species are not dangerous to humans at all.

          The United States averages just 16 shark attacks each year and slightly less than one shark-attack fatality every two years. Meanwhile, in the coastal U.S. states alone, lightning strikes and kills more than 41 people each year.

          Each year there are about 50 to 70 confirmed shark attacks and 5 to 15 shark-attack fatalities around the world. The numbers have risen over the past several decades but not because sharks are more aggressive: Humans have simply taken to coastal waters in increasing numbers.

          Over 375 shark species have been identified, but only about a dozen are considered particularly dangerous. Three species are responsible for most human attacks: great white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and bull (Carcharhinus leucas) sharks.

          While sharks kill fewer than 20 people a year, their own numbers suffer greatly at human hands. Between 20 and 100 million sharks die each year due to fishing activity, according to data from the Florida Museum of Natural History’s International Shark Attack File. The organization estimates that some shark populations have plummeted 30 to 50 percent.

          The shortfin mako (Isurus oxyrinchus) is often recognized as the world’s speediest shark. It has been clocked at speeds of up to 20 miles an hour (32 kilometers an hour) and can probably swim even faster than that. Makos are fast enough to catch even the fleetest fish, such as tuna and swordfish.

Picture Credit : Google

          Of course, it is the female seahorse that is the real mother, producing and laying eggs. The difference is that she lays the eggs in a special pouch on the male seahorse’s body. The babies develop inside the pouch and emerge when they are fully developed. As they emerge, it looks as though they are being born from the male seahorse.

          Seahorses and their close relatives the pipefish and the seadragons are very unusual, because it is the males that get pregnant and give birth to the babies. Instead of growing the baby seahorses inside their belly in a uterus, like human mums do, the seahorse dads will carry the babies in a pouch, a bit like a kangaroo’s pouch.

          To produce babies, seahorses have to mate first. Seahorse mating is really beautiful. Males and females dance around one another and flutter their fins, and they may dance together over several days before they actually mate.

          When they’ve decided they like each other, the seahorse females swim towards the surface of the water, and the males follow. The females then put their bright orange eggs into the pouch of the males through the hole at the top of the pouch. Once the eggs are safely inside, the males will add their sperm and shut the opening. The eggs are fertilized by the sperm, and then start developing into baby seahorses.

          With that, the job of the seahorse mum is done! She swims off, and leaves the father to take care of the growing babies. Inside the pouch, the babies grow eyes, tiny snouts, and little tails. It takes about 20 days for the babies to develop, safely tucked away from other animals that might want to eat them.

Picture Credit : Google

          The salmon hatches in freshwater streams and rivers but then begins an incredible journey of up to 5000km (3000 miles), first to the open sea and then to return to the same river in which it was spawned in order to breed. The salmon only makes the journey once —after spawning, it dies. The European eel makes the reverse journey. It spawns in the Sargasso Sea, in the western Atlantic, and its tiny larvae swim to the shores of Europe and North America, becoming lever’s (small eels) on the journey. They then spend several years in freshwater rivers and lakes before returning to the Sargasso Sea to breed. Whales also travel huge distances, this time in search of food. The tiny plankton that they eat is found more abundantly in certain areas during the year.

          Salmon mostly spend their early life in rivers, and then swim out to sea where they live their adult lives and gain most of their body mass. When they have matured, they return to the rivers to spawn. Usually they return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetoreception to locate the general position of their natal river, and once close to the river, that they use their sense of smell to home in on the river entrance and even their natal spawning ground.

          A whale shark has made the longest migration journey ever recorded travelling 12,000 miles across the Pacific Ocean. The large fish, named Anne by scientists, was tracked making the mammoth migration from near Panama in the south eastern Pacific, to an area close to the Philippines in the Indo-Pacific. Experts at the Smithsonian Tropical Research Institute followed her signal from Panamanian waters, past Clipperton Island and Costa Rica’s Cocos Island, en-route to Darwin Island in the Galapagos, a site known to attract groups of sharks. The trip was the first recorded evidence of a trans-Pacific migration route for the species of the largest living fish.

          Marine biologist Dr Héctor Guzmán, who first tagged Anne near Coiba Island in Panama, said: “We have very little information about why whale sharks migrate. “Are they searching for food, seeking breeding opportunities or driven by some other impulse?” Genetic studies show that whale sharks across the globe are closely related, suggesting they must travel long distances to mate. An adult female can travel around 40 miles per day and can dive more than 1,900 metres.

          The largest groups of fish are bony fish. Most of these, making up 95% of fish species, are known as teleosts. They have skeletons made of bone and are usually covered with small overlapping bony plates called scales. They also have swim bladders, filled with gas, to help them remain buoyant. Cartilaginous fish include sharks, skates and rays. Their skeletons are made of flexible cartilage but, as they do not have swim bladders, they must keep moving all the time to keep their position in the water. They usually have tough, leathery skins and fleshy fins.

          Bony fish, also known as Osteichthyes, is a group of fish that is characterized by the presence of bone tissue. The majority of the fish in the world belong to this taxonomic order, which consists of 45 orders, 435 families, and around 28,000 species. This class of fish is divided into two subgroups: Actinopterygii (ray-finned) and Sarcopterygii (lobe-finned).

          Cartilaginous fish, also known as Chondrichthyes, is a group of fish that is characterized by the presence of cartilage tissue rather than bone tissue. This class of fish is divided into two subgroups: Elasmobranchii and Holocephali. Common names of cartilaginous fish include sharks, skates, sawfish, rays, and chimaeras.

          The principal difference between bony fish and cartilaginous fish is in the skeleton makeup. As previously mentioned, bony fish have a bone skeleton whereas cartilaginous fish have a skeleton made of cartilage. There are, however, several other differences between these two classes of fish. These differences are listed below.

          The vast majority of cartilaginous fish survive in marine, or saltwater, habitats. These fish can be found throughout the world’s seas and oceans. Bony fish, in contrast, are found in both saltwater and freshwater habitats.

          Fish gills are tissues located on the either side of the throat. These tissues ions and water into the fish’s system, where oxygen from the water and carbon dioxide from the fish are exchanged. In other words, fish gills act as lungs. In bony fish, the gills are covered by an external flap of skin, known as the operculum. In cartilaginous fish, the gills are exposed and not protected by any external skin. The majority of fish, whether bony or cartilaginous, have five pairs of gills.

          Bony and cartilaginous fish are also different in their reproductive behaviors. Bony fish reproduce in what is considered a primitive form of reproduction. These fish produce a large number of small eggs with very little yolk. These eggs are released into the open waters, among rocks on the river or seabed. Male fish then swim over the laid eggs, fertilizing them with sperm which may or may not reach all of the eggs. The eggs hatch into larvae, which are essentially defenseless. The larvae must then develop in the wild, where they are vulnerable to external threats. In this method, the survival rate is low.

          In cartilaginous fish, reproduction occurs internally. The sperm is deposited inside of the female in order to fertilize a small number of large sized eggs with a significant amount of yolk. Cartilaginous fish embryo may develop in one of two manners. In one, the embryo develops within a laid egg, relying on the large yolk for nutrients. In the second, more advanced manner, the embryo are able to develop in the secure and protected environment of the mother’s uterus. These fish are born as fully functional organisms, rather than as developing larvae. After delivery or hatching, baby cartilaginous fish are able to hunt and hide from predators. This development process ensures a higher rate of survival.

          In both classes of fish, the heart is divided into 4 chambers. In the hearts of cartilaginous fish, one of these chambers is known as the conus arteriosus, a special contracting heart muscle. In place of this chamber, bony fish have a bulbous arteriosus, a non-contracting muscle.

          Another difference between the bony and cartilaginous fish is in how each class produces red blood cells. In bony fish, the red blood cells are produced in the bone marrow, the central part of the bone. This process is known as hemopoiesis. Cartilaginous fish lack bone marrow for hemopoiesis. Instead, these fish produce red blood cells in the spleen and thymus organs.

          Fish are the oldest vertebrates on Earth. They are cold blooded and spend all their lives in water. They breathe by taking in oxygen dissolved in the water. Most fish breathe by using gills. They gulp in water through their mouths and pass it out through the gills, which are rich in blood and extract oxygen from the water as it passes through them.

          Despite living in water, fishes need oxygen to live. Unlike land-dwellers, though, they must extract this vital oxygen from water, which is over 800 times as dense as air. This requires very efficient mechanisms for extraction and the passage of large volumes of water (which contains only about 5% as much oxygen as air) over the absorption surfaces.

          To achieve this, fishes use a combination of the mouth (buccal cavity) and the gill covers and openings (opercula). Working together, this form a sort of low-power, efficient pump that keeps water moving over the gas absorption surfaces of the gills. The efficiency of this system is improved by having a lot of surface area and very thin membranes (skin) on the gills. However, these two features also increase problems with osmoregulation, as they also encourage water loss or intake. Consequently, every species must trade off some respiratory efficiency as a compromise for proper osmoregulation.

          Blood passing through the gills is pumped in the opposite direction to the water flowing over these structures to increase oxygen absorption efficiency. This also ensures that the blood oxygen level is always less than the surrounding water, to encourage diffusion. The oxygen itself enters the blood because there is less concentration in the blood than in the water: it passes through the thin membranes and is picked up by hemoglobin in red blood cells, then transported throughout the fish’s body.

          As the oxygen is carried through the body, it diffuses into the appropriate areas because they have a higher concentration of carbon dioxide. It is absorbed by the tissues and used in essential cell functions. The carbon dioxide is produced as a by-product of metabolism. Since it is soluble, it diffuses into the passing blood and is carried away to eventually be diffused through the gill walls. Some of the carbon dioxide may be carried in the blood as bicarbonate ions, which are used as part of osmoregulation by trading the ions for chloride salts at the gills.

          Insects’ extraordinary compound eyes are made up of hundreds of tiny lenses. The images from all the lenses are made sense of by the insect’s brain. Like us, insects can see colour, although in a different way. Flowers that seem dull to us may seem very bright to an insect. As well as having good vision, many insects have sensitive hearing and an acute sense of smell. A female moth, for example, gives off a smell that can be detected by male moths several kilometres away.

          Scientists have long believed insects would not see fine images. This is because their compound eyes typically consist of thousands of tiny lens-capped ‘eye-units’, which together should capture a low-resolution pixelated image of the surrounding world.

          In contrast, the human eye has a single lens, which slims and bulges as it focuses objects of interests on a retinal light-sensor (photoreceptor) array; the megapixel “camera chip” inside the eye. By actively changing the lens shape, or accommodating, an object can be kept in sharp focus, whether close or far away. As the lens in the human eye is quite large and the retinal photoreceptor array underneath it is densely-packed, the eye captures high-resolution images.

          However, researchers from the University of Sheffield’s Department of Biomedical Science with their Beijing, Cambridge and Lisbon collaborators have now discovered that insect compound eyes can also generate surprisingly high-resolution images, and that this has much to do with how the photoreceptor cells inside the compound eyes react to image motion.

          Unlike in the human eye, the thousands of tiny lenses, which make the compound eye’s characteristic net-like surface, do not move, or cannot accommodate. But the University of Sheffield researchers found that photoreceptor cells underneath the lenses, instead, move rapidly and automatically in and out of focus, as they sample an image of the world around them. This microscopic light-sensor “twitching” is so fast that we cannot see it with our naked eye. To record these movements inside intact insect eyes during light stimulation, the researcher had to build a bespoke microscope with a high-speed camera system.

          Remarkably, they also found that the way insect compound eye samples an image (or takes a snapshot) is tuned to its natural visual behaviours. By combining their normal head/eye movements – as they view the world in saccadic bursts – with the resulting light-induced microscopic photoreceptor cell twitching, the insects, such as flies, can resolve the world in much finer detail than was predicted by their compound eye structure, giving them hyperacute vision. The new study, published in the journal e-Life, changes our understanding of insect and human vision and could also be used in industry to improve robotic sensors.

          There are almost, as many different ways in which insects protect themselves from enemies as there are different insects. Some insects, such as wasps and ants, have powerful stings or are able to shower their attackers with poisonous fluid. The hoverfly does not sting, but its colouring is so like that of a wasp or bee that enemies are very wary of it! Other insects, such as stick insects and praying mantises use camouflage. They look like the leaves and twigs among which they feed.

          In the insect community there exist many different methods of hunting and killing. Some of these methods are short and quick, and others seem to be slow and painful. Some insects do not even have to fight by virtue of their spectacular camouflaged bodies. However, other insects are nearly always vulnerable to predators. Many insects sport particular colors that scare predators away and some insects use venom in order to subdue their prey before feasting on it. There are many more methods of attack and defense to be observed in the insect world, and even the few methods named above do not begin to touch upon the great variety of ways that insects attack others and defend themselves.

          Some insects use irritating sprays to subdue their enemies. For example, ladybugs, bombardier beetles, and blister beetles are just a few insects that are capable of deterring predators with unpleasant fluids. The bombardier beetle keeps a caustic substance within its abdomen at all times. When this beetle’s life is threatened by a predator, it will spray the invader with its caustic fluid. While the injured predator is occupied with the caustic substance, the bombardier beetle will make its getaway.

          Another interesting, and largely unheard of defense tactic employed by some arthropods involves the sacrifice of a limb. Many long-legged insects, such as katydids, walkingsticks and craneflies have easily detachable legs, which they are more than happy to give up to a predator if it means getting away alive. These legs have “fracture points” located at certain joints on the legs. When a leg is pulled by a predator, the leg will become detached, leaving the insect alive and the predator with a modest meal.

          This is different than mimicry or camouflage, though it uses the same principle. Some insects “hide in plain sight” by resembling objects in their environment. A thorn could really be a treehopper; a twig might be a walkingstick, an assassin bug, or a caterpillar; and sometimes a dead leaf turns out to be a katydid, a moth, or even a butterfly. Some caterpillars resemble bird droppings, and others have false eyespots on their wings or body to create an imitation of a predator’s head. Often, these guys are the coolest-looking… the details in their appearance astonishing in their accuracy and creativity.

          If there is one thing most of us have in common, it’s distaste for foul smells. And the really bad ones can be enough to make you recoil. Ever been at the epicenter of a skunk attack? It’s like someone is burning tires directly in your NOSE. Stink bugs have special glands that produce a foul-smelling reek. The caterpillar form of some swallowtail butterflies have glands just behind their heads that, when disturbed, will rear up and release a terrible stench. Darkling beetles will raise their big, black butt in warning when they are threatened, and if you don’t pay attention to the warning – will expel acrid, foul-smelling fluid.

          When stink and burning isn’t enough, some bugs will hit their attackers with sticky compounds that harden like glue and incapacitate. Some kinds of cockroaches guard their backsides with a slimy anal secretion (those are three words that are just terrible together) that cripples any ants that launch an attack. And there are types of soldier termites that have nozzle-like heads that can spays sticky, immobilizing toxic fluids at attackers as varied as ants, spiders, centipedes, and other predatory arthropods.

Living things are classified in groups that have certain characteristics in common. The largest groups are called kingdoms. All living things can be classified as belonging to one of the five kingdoms: animals, plants, fungi, protists and monerans. Kingdoms can be divided into phyla (singular: phylum) or divisions and subphyla, which in turn can be separated into classes. Classes are divided into orders and suborders. These are separated into families and then into genera (singular: genus). Finally, each genus contains a number of species.

All living organisms are classified into groups based on very basic, shared characteristics. Organisms within each group are then further divided into smaller groups. These smaller groups are based on more detailed similarities within each larger group. This grouping system makes it easier for scientists to study certain groups of organisms. Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together. These specialized groups are collectively called the classification of living things. The classification of living things includes 7.

levels: Kingdom, phylum, classes, order, families, genus, and species.

Kingdoms

The most basic classification of living things is kingdoms. Currently there are Five kingdoms. Living things are placed into certain kingdoms based on how they obtain their food, the types of cells that make up their body, and the number of cells they contain.
Phylum

The phylum is the next level following kingdom in the classification of living things. It is an attempt to find some kind of physical similarities among organisms within a kingdom. These physical similarities suggest that there is a common ancestry among those organisms in a particular phylum.

Classes

Classes are way to further divide organisms of a phylum. As you could probably guess, organisms of a class have even more in common than those in an entire phylum. Humans belong to the Mammal Class because we drink milk as a baby.
Order

Organisms in each class are further broken down into orders. A taxonomy key is used to determine to which order an organism belongs. A taxonomy key is nothing more than a checklist of characteristics that determines how organisms are grouped together.
Families

Orders are divided into families. Organisms within a family have more in common than with organisms in any classification level above it. Because they share so much in common, organisms of a family are said to be related to each other. Humans are in the Hominidae Family.

Genus

Genus is a way to describe the generic name for an organism. The genus classification is very specific so there are fewer organisms within each one. For this reason there are a lot of different genera among both animals and plants. When using taxonomy to name an organism, the genus is used to determine the first part of its two-part name.

Species

Species are as specific as you can get. It is the lowest and most strict level of classification of living things. The main criterion for an organism to be placed in a particular species is the ability to breed with other organisms of that same species. The species of an organism determines the second part of its two-part name.

One theory is that climate changes gradually led to a drop in dinosaur numbers. Another is that a huge meteorite hit the Earth, throwing up a massive dust cloud. Mammals managed to survive the climate change, but dinosaurs did not.

It was at this time when something happened that caused dinosaurs to become extinct. While there are several ideas, one that many scientists believe is that a huge comet or asteroid 6 to 12 miles wide slammed into the region that is now part of the eastern coast of Mexico, but at that time was under water.

The impact of this object is believed to have caused darkness over the entire earth for many months, due to the huge amounts of dust that were thrown into the atmosphere. A global wildfire would have destroyed over half of all living things. Water would have been poisoned in most places, and the earth would have sunk into a deep freeze while the dust was in the air.

Even through all this, some plants and animals survived, including some insects, fishes, frogs, crocodiles, turtles, birds, and mammoths.

This may have just been part of a series of changes that caused the extinction of the dinosaurs. Before the asteroid/comet hit the earth, massive eruptions of volcanoes had caused earth’s climate to be changed. At about the same time, sea levels dropped dramatically, opening new land bridges, changing ocean currents, and affecting the climate. These changes in climate likely reduced the ability of the dinosaurs to adapt, and the impact from the asteroid/comet was the last straw. The creatures that were able to survive all these changes came to dominate the landscape. Mammals grew larger, and moved into new areas, taking over locations that had previously been the habitat of dinosaurs.

Changes in sea levels, ocean currents, and other events were also bringing in a new climatic cycle to the earth. Huge ice sheets would begin to cover large areas of the earth on a periodic basis. These swings in climate would have a major effect on animal habitats.

Over time, the remains of plants and animals decay. Fossilization is one way in which their forms have survived to give us information about prehistoric times. Since the time of the dinosaurs, however, the climate of parts of the Earth has cooled. In recent years, frozen remains of mammoths and even humans have been found, preserved in the ice of polar or mountainous regions.

Paleoanthropology to hear the preceding term pronounced is the study of early forms of humans and their primate ancestors.  It is similar to paleontology to hear the preceding term pronounced except its focus is documenting and understanding human biological and cultural evolution.  Paleoanthropologists do not look for dinosaurs and other early creatures.  However, like paleontology, the data for paleoanthropology is found mainly in the fossil record.  Before examining this evidence, it is necessary to first learn what fossils are and how they are formed.  In addition, it is important to know how paleoanthropologists date fossils and other evidence of the prehistoric past.

Taphonomy to hear the preceding term pronounced is the study of the conditions under which plants, animals, and other organisms become altered after death and sometimes preserved as fossils.  Research into these matters has shown that fossilization is a rare phenomenon.  In order for a fossil to form, the body must not be eaten or destroyed by erosion and other natural forces.  Preservation would most likely occur if the organism were buried quickly and deeply.  In most environments, soft body parts, such as skin, muscle, fat, and internal organs, deteriorate rapidly and leave no trace.  Only very rarely do we find the casts of such tissues.  Similarly, the totally soft-bodied creatures, like jellyfish, are very uncommon fossils.  Hard body parts, such as dense bones, teeth, and shells, are what most often are preserved.  It is likely that the vast majority of fossils will never be found before they are destroyed by erosion.  That coupled with the fact that extremely few living things are preserved long enough after death to become fossils makes the large collections of fossils in the museums of the world quite remarkable.  It is a testament to the tenacious searching by fossil hunters over the last two centuries.

People often think of fossils as being mineralized bones or shells stored in museums.  However, they can be any remains or traces of ancient organisms.  They even can be footprints, burrows, or casts of bodies with nothing else surviving.  Some of the best preserved fossils were rapidly frozen in permafrost soil or ice, dehydrated in dry desert caves, or encased in tree resin that hardened into amber.  In any of these three environmental conditions, even soft body parts can be remarkably well preserved indefinitely. 

Several wooly mammoths that lived during the last ice age have been excavated from frozen tundra soil in Siberia.  Some were still in such good condition, that parts of their bodies were fed to the dogs of the Russian scientists who found them.  One small mammoth was even transported intact to Moscow where it is kept in a specially made large freezer that allows it to be displayed for the general public.  The oldest frozen human remains were discovered on the edge of a glacier in the Alps of northern Italy in 1991.  It was a well preserved body of a man, along with his clothes and tools, who died about 5,300 years ago.  Even tattoos on his skin were preserved by the extreme cold. 

Dinosaur fossils, even when they show the skin of the animal, cannot show us what colour it was. Dinosaurs may have been green and brown in colour, camouflaging them amongst the leaves and rocks. It is also possible that some of them were very brightly coloured, just as some tropical lizards are today.

While skin impressions have been found — suggesting a pebbly or scaly texture — no real dinosaur skin remains. That means paleontologists don’t know for certain what color any of the dinosaurs were. They do have several theories, though. For example, many believe that dinosaur skin was probably drab shades of gray or green, allowing them to blend into their surrounding environments. This dull coloration would help them escape the detection of predators, enabling some to survive longer. Because large modern-day warm-blooded animals, such as elephants and rhinoceroses, tend to be dully colored, many scientists think that dinosaurs were, too.

But other paleontologists say the opposite is true — that dinosaurs’ skin could have been shades of purple, orange, red, even yellow with pink and blue spots! Rich and varied colors, they argue, might have helped dinosaurs to recognize one another and attract mates. Because research has shown that dinosaurs’closest living relatives — birds — can see in color, it is theorized that dinosaurs could, too. Scientists in this camp believe that color may well have been as important to these ancient creatures as it is to us.

Jack Horner, Curator of Paleontology at the Museum of the Rockies, Denver, Colorado, explains, “Some male dinosaurs may have had brightly colored crests to help them attract mates, but females probably did not. This color differentiation is also found in many modern-day birds.”

During the 150 million years that they lived on Earth, dinosaurs certainly included the largest creatures to live on land and the fiercest hunters. But they were not the only animals to live successfully on Earth by any means. There were many species of insect and the earliest winged animals could be seen in the skies. The seas were teeming with fish and other sea-life. The first mammals were also thriving, ready to become the dominant creatures when the dinosaurs became extinct.

It is often said that dinosaurs ruled the earth. Movies such as Jurassic Park, the media, and educational books constantly promote the evolutionary claim that dinosaurs dominated planet earth for well over 100 million years. In the evolutionary paradigm, mankind had not yet evolved, and before the 65-million-year-old extinction mark, mammals were small rodents who steered clear of the ruling dinosaurs.

The prevailing evolutionary model argues that the coexistence of dinosaurs, large mammals, and humans is not supported for four reasons. First, dinosaur and human fossils have never been discovered together in the fossil record. Second, large mammals have never been discovered in ‘dinosaur’ rock. Third, dinosaurs could not have existed with larger mammals due to intense competition in similar environments. Fourth, dinosaurs would have overrun human civilization due to their monolithic size and belligerence. However, these arguments do not stand up to closer scrutiny and the weight of the evidence provides far greater support to biblical creation.

The historical narrative of Genesis plainly records that God created all land animals and human beings on the sixth day of creation about 6,000 years ago. According to the Bible, dinosaurs, mammals, and humans have coexisted from the beginning of creation. This is in direct contradiction to the evolutionary model of earth history. And although the idea of dinosaurs and human beings living at the same time is ridiculed as illogical and unscientific, a more open-minded approach reveals a different story. Circumstantial evidence in the fossil record, literary and artistic accounts in human civilization, and observational examples in present-day ecological habitats lend a high degree of credibility to the biblical account.

Ever since human beings first lived on Earth they have been finding fossilized remains. But it was really only in the nineteenth century that scientific study of the fossils took place. Until then, people believed that the fossils came from dragons, giants or even unicorns!

Thanks to modern science, we know a lot about the dinosaurs that used to roam Earth. How do scientists know so much? It’s not like they can observe them in the wild like they do with modern animals. Instead, they rely upon what dinosaurs left behind. No, not their diaries! Scientists study their fossilized bones and, sometimes, other bodily material.

No one knows when the first dinosaur bone was found. Ancient peoples most likely uncovered fossils of dinosaur bones from time to time, but they had no idea what they had found. Ancient Chinese writings from over 2,000 years ago reference “dragon” bones, which many experts today believe had to be dinosaur fossils.

Even early scientists weren’t sure about the fossils they found. For example, in 1676, Reverend Robert Plot, a curator of an English museum, discovered a large thigh bone in England. He believed it belonged to ancient species of human “giants.” Although the specimen disappeared eventually, drawings of it remain. Based upon those drawings, modern scientists believe it was probably from a dinosaur known as “Megalosaurus.”

Megalosaurus is believed to be the first dinosaur ever described scientifically. British fossil hunter William Buckland found some fossils in 1819, and he eventually described them and named them in 1824. Like scientists before him, Buckland thought the fossils belonged to an ancient, larger version of a modern reptile.

As of that time, the word “dinosaur” still had not been invented yet, and dinosaurs hadn’t yet been recognized as distinct creatures that were significantly different than modern reptiles. All that changed when British scientist Richard Owen came along.

In late 1841 or early 1842, Owen viewed the fossil collection of William Devonshire Saul. He was intrigued by a fossilized chunk of spine, which was thought to belong to an ancient reptile similar to an iguana that had been called “Iguanodon.”

Owen began comparing the fossils he saw and, within a few months, came to two critical conclusions: (1) that the fossils were from similar creatures; and (2) these were creatures unlike anything on Earth today. He coined the term “dinosaurs,” which means “terrible lizards.”

          Almost everything that we know about the living things on Earth before humans evolved has been learnt from fossils. Fossils are the remains of dead animals and plants that have been turned to stone over millions of years.

          Because, by definition, there are no written records from prehistoric times, much of the information we know about the time period is informed by the fields of paleontology and archeology—the study of ancient life through fossils and the study of the material left behind by ancient peoples, including the cave painting of Lascaux, and such constructions as Stonehenge in southern England and the huge earthworks at Silbury Hill. There is much that is still unknown about the purpose of these “artifacts,” but the caves show an early ability to create art while Stonehenge demonstrates knowledge of astronomy. It is also possible that religious beliefs and practices were associated with these prehistoric monuments, perhaps involving the winter and spring Equinoxes.

          Human prehistory differs from history not only in terms of chronology but in the way it deals with the activities of archaeological cultures rather than named nations or individuals. Restricted to material remains rather than written records (and indeed only those remains that have survived), prehistory is anonymous. Because of this, the cultural terms used by prehistorians, such as Neanderthal or Iron Age are modern, arbitrary labels, the precise definition of which are often subject to discussion and argument. Prehistory thus ends when we are able to name individual actors in history, such as Snofru, founder of the Fourth Dynasty of Egypt, whose reign began circa 2620 B.C.E.

          The date marking the end of prehistory, that is the date when written historical records become a useful academic resource, varies from region to region. In Egypt it is generally accepted that prehistory ended around 3500 B.C.E. whereas in New Guinea the end of the prehistoric era is set much more recently, at around 1900 C.E. The earliest historical document is said to be the Egyptian Narmer Palette, dated 3200 B.C.E.

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          The surface of the Earth is changing all the time. When living things first began to evolve on Earth, there was just one huge continent. Over millions of years, this continent broke up and moved to become the land masses we recognize today. This is why similar dinosaur fossils have been found in very different parts of the world, although dinosaurs were land creatures and could not cross the oceans.

          The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth’s past, characterized by constant geological change and biological evolution.

          The geological time scale (GTS), as defined by international convention, depicts the large spans of time from the beginning of the Earth to the present, and its divisions chronicle some definitive events of Earth history. (In the graphic: Ga means “billion years ago”; Ma, “million years ago”.) Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean, but the early atmosphere contained almost no oxygen. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. While the Earth was in its earliest stage (Early Earth), a giant impact collision with a planet-sized body named Theia is thought to have formed the Moon. Over time, the Earth cooled, causing the formation of a solid crust, and allowing liquid water on the surface.

          The Hadean eon represents the time before a reliable (fossil) record of life; it began with the formation of the planet and ended 4.0 billion years ago. The following Archean and Proterozoic eons produced the beginning of life on Earth and its earliest evolution. The succeeding eon is the Phanerozoic, divided into three eras: the Palaeozoic, an era of arthropods, fishes, and the first life on land; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which saw the rise of mammals. Recognizable humans emerged at most 2 million years ago, a vanishingly small period on the geological scale.

          The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era, after a geological crust started to solidify following the earlier molten Haden Eon. There are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland as well as “remains of biotic life” found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, “If life arose relatively quickly on Earth … then it could be common in the universe.”

          Photosynthetic organisms appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. Life remained mostly small and microscopic until about 580 million years ago, when complex multicellular life arose, developed over time, and culminated in the Cambrian Explosion about 541 million years ago. This sudden diversification of life forms produced most of the major phyla known today, and divided the Proterozoic Eon from the Cambrian Period of the Paleozoic Era. It is estimated that 99 percent of all species that ever lived on Earth, over five billion, have gone extinct. Estimates on the number of Earth’s current species range from 10 million to 14 million, of which about 1.2 million are documented, but over 86 percent have not been described. However, it was recently claimed that 1 trillion species currently live on Earth, with only one-thousandth of one percent described.

          The Earth’s crust has constantly changed since its formation, as has life since its first appearance. Species continue to evolve, taking on new forms, splitting into daughter species, or going extinct in the face of ever-changing physical environments. The process of plate tectonics continues to shape the Earth’s continents and oceans and the life they harbor. Human activity is now a dominant force affecting global change, harming the biosphere, the Earth’s surface, hydrosphere, and atmosphere with the loss of wild lands, over-exploitation of the oceans, production of greenhouse gases, degradation of the ozone layer, and general degradation of soil, air, and water quality.

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          Although viruses are the simplest living things, they need to live and reproduce themselves inside a larger organism, so they are unlikely to have been the first living things on Earth. The earliest evidence of life that has been found is tiny fossils of primitive bacteria in rocks about 3800 million years old. Later, blue-green algae evolved. They could use energy from the Sun and in so doing gave off oxygen. Modern plants and animals share these simple organisms as ancestors.

          The earliest evidence for life on Earth arises among the oldest rocks still preserved on the planet. Earth is about 4.5 billion years old, but the oldest rocks still in existence date back to just 4 billion years ago. Not long after that rock record begins, tantalizing evidence of life emerges: A set of filament-like fossils from Australia, reported in the journal Astrobiology in 2013, may be the remains of a microbial mat that might have been extracting energy from sunlight some 3.5 billion years ago. Another contender for world’s oldest life is a set of rocks in Greenland that may hold the fossils of 3.7-billion-yer-old colonies of cyanobacteria, which form layered structures called stromatolites.

          Some scientists have claimed to see evidence of life in 3.8-billion-year-old rocks from Akilia Island, Greenland. The researchers first reported in 1996 in the journal Nature that isotopes (forms of an element with different numbers of neutrons) in those rocks might indicate ancient metabolic activity by some mystery microbe. Those findings have been hotly debated ever since — as, in fact, have all claims of early life.

          Most recently, scientists reported in the journal Nature that they had discovered microfossils in Canada that might be between 3.77 billion and 4.29 billion years old, a claim that would push the origins of life to very shortly after Earth first formed oceans. The filament-like fossils contained chemical signals that could herald life, but it’s hard to prove that they do, researchers not involved in the study told Live Science. It’s also hard to prove that fossils found in ancient rocks are necessarily ancient themselves; fluids have penetrated cracks in the rock and might have allowed newer microbes in to older rock. The researchers used samarium-neodymium dating to arrive at the 4.29 billion maximum age for the fossils. This method, which uses the decay of one rare-earth element into another, may measure the age of the magma that formed the rocks rather than the rocks themselves, an issue that has also dogged claims of the Earth’s oldest rocks.   

          Still, the fact that suggestive evidence of life arises right as the rock record begins raises a question, said University of California, Los Angeles, geochemist Elizabeth Bell in a SETI Talk in February 2016: Is the timing a coincidence, or were there earlier forms of life whose remnants disappeared with the planet’s most ancient rocks?

          The period that occurred before the rock record begins is known as the Hadean. It was an extreme time, when asteroids and meteorites pummeled the planet. Bell and her colleagues said they might have evidence that life arose during this very unpleasant time. In 2015, the research team reported discovering graphite, a form of carbon, in 4.1-billion-year-old crystals of zircon. The ratio of isotopes in the graphite suggested a biological origin, Bell and her colleagues wrote in the journal Proceedings of the National Academy of Sciences.

          “There is some skepticism, which is warranted,” Bell told Live Science. Meteorites or chemical processes might have caused the odd carbon ratios, she said, so the isotopes alone aren’t proof of life. Since the publication of the 2015 paper, Bell said, the researchers have found several more of the rare-carbon inclusions, which the scientists hope to analyze soon.

          From what is known of this period, there would have been liquid water on the planet, Bell told Live Science in an interview. There might have been granite, continental-like crust, though that’s controversial, she said. Any life that could have existed would have been a prokaryote (a single-celled organism without membrane-bound nuclei or cell organelles), Bell added. If there was continental crust on Earth at the time, she said, prokaryotes might have had mineral sources of nutrients like phosphorus.

          A different approach to the hunt for Earth’s early life suggests that oceanic hydrothermal vents may have hosted the first living things. In a paper published in July 2016 in the journal Nature Microbiology, researchers analyzed prokaryotes to find the proteins and genes common to all of these organisms, presumably the final remnants of the Last Universal Common Ancestor (LUCA) — the first shared relative from which all life today descends.

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