Category Animal World

            Migration is a fascinating phenomenon that Nature repeats every year. It is the seasonal movement of some animals, from one place to another, year after year, usually across vast distances.

            Birds, fishes, mammals, insects and reptiles all migrate. Animals migrate for many reasons. It may be to find food, or to escape harsh weather. Some may travel thousands of miles in the spring, and then, thousands of miles back in the fall.

            Animals also migrate in search of better food supplies, or a safe place to give birth to their young. Such migrations happen on a regular basis. Irregular migrations are sometimes triggered by famine or over-population.

            The Arctic tern, the sea bird, travels from one end of the world to the other end every year! This is the longest migration undertaken by any bird. This bird flies in zigzagging routes between breeding grounds in the Arctic and Antarctica each year, a distance of around 70,900 kilometres. They will spend about four or five months in Antarctica, before heading back to the Arctic. Scientists have extensively studied the evolution of migration. But no single theory has been fully accepted.

            No, not all birds fly. The ostrich, the largest bird on Earth is the best example of a bird that cannot fly. The ostrich is found in the African savannah. Though it cannot fly, it can run very fast, at a speed up to 72 kilometres per hour. An ostrich may be as much as 2.5 metres tall and weigh about 135 kilogrammes. Ostriches produce the largest egg of any living bird. One egg may weigh about 1500 grammes and have the same volume as 25 hen eggs.

            Ostriches, penguins, cassowaries, rheas, emus and liwis are the most well-known flightless birds.

            The penguin, found in Antarctica, has wings modified into flippers to aid it in swimming.

            The cassowary is a large, flightless bird from Australia and New Guinea. It is the biggest bird in Australia, and the second biggest bird in the world, after ostrich. Cassowaries grow to be about 2 metres tall and weigh about 60 kilogrammes. The largest known cassowary was 83 kilogrammes. The cassowary’s life span is about 40 to 50 years.

            Cassowaries have powerful legs and a helmet like crest on the head. They protect themselves by kicking. Cassowaries can run at a speed of upto 50 kilometres per hour.

            Rheas are found only in South America. They are also called South America ostriches. These birds have a height of about 1.5 metres and weigh more than 25 kilogrammes. Rheas are brown in colour.

            Kiwis are small flightless birds. They are the size of a hen, and weigh from 1.5 to 4 kilogrammes. There are three types of kiwis – the common kiwi, spotted kiwi and the little gray kiwi. All are found in New Zealand.

            An important difference between flying and flightless birds is the fact that flightless birds have smaller wing bones. Another distinction is the absent (or greatly reduced, or flat) keel on the breastbone of flightless birds. Flying birds have a keel on their breastbone. The keel anchors the strong muscles that move a bird’s wings during flight. Flightless birds also have more feathers than flying birds. These feathers weigh more.

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            The fastest known bird in level flight is the white throated spine tailed swift. It has been recorded as flying at speeds of over 170 kmph.

            Common eiders, or coastal ducks, can fly nearly 75 kmph. Dunlins (shorebirds) once caught up with, and passed a plane flying at 160 kmph! Swifts, as their name indicates, are among the fastest of all flying birds.

            Peregrine falcons can chase their prey in level flight at 60 kmph, but when stooping or diving to catch it, they reach much higher speeds.

            Other high-speed birds include buzzards, which can glide between 110 and 130 kilometres per hour. Swallows are believed to be able to reach 160 kilometres per hour when migrating, but normally, they do not fly faster than about 50 kilometres per hour.

            The Andean condor, with a wingspan of up to 2.9 metres, is the largest flying bird! This bird lives in the Andes Mountains of South America. Both the Andean condor, and its slightly smaller cousin, the California condor, have unusual wings which allow them to soar only when there is an upward rising air current, and when the weather is dry. When it rains, condors cannot fly, so they must stretch out their wings and allow them to dry before they can once again take to the air. California condors are an endangered species.

            The wandering albatross is also a large flying bird. From one wing tip to another, it’s as long as a family car!

            To escape winter, the whooper swan flies nonstop from Iceland to Scotland – a 1125 km flight. This is the longest flight made by any species of swan. Whoopers are very shy birds, who got their name from the whooping calls they make. They are usually found in fresh water, though at times, they can be seen on sheltered inlets. There are only 1,00,000 Whoopers in the entire world, but their future is very secure, because it is against the law to kill them.

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               Colours in the feather of a bird are formed in two different ways. Pigments, and the physical structure of the feather. Many feathers are coloured by a combination of these features.

               Pigments are chemical compounds that absorb certain wavelengths of light while reflecting others. The colours you see are those reflected back. Feathers coloured by pigments range from crow black to canary Yellow and cardinal red.

               Many colours, such as blue, are a result of feather structure. When light hits these feathers, it hits microscopic structures on the feather that act as prisms to reflect a colour. No blue pigment is known in birds. If you crush a blue scrub jay feather, or dunk it in water it will appear gray.

               Shimmering iridescent colours such as those found in hummingbirds and peacocks are caused by special structures, air bubbles, or films in feather surfaces. These modifications interfere with the bending and scattering of light to strengthen some wavelengths, and cancel out others.

            Bird feathers, which evolved from the scales of reptiles, perform the same function that reptile scales do – they protect a bird in a variety of ways – from the harmful rays of the Sun, from rain, and from injury to their delicate skin.

            They also have the remarkable ability to trap air, thus insulating birds from the cold. There are also feathers on the wings of a bird, which help it to fly. Some birds also use their own feathers to line their nests. Ptarmigans, birds that live in the snow, have feathers on their feet that act like snowshoes!

            These special feathers help the birds from falling through deep snow. This bird changes its feathers three times a year, to help it to camouflage itself as the seasons change.

            The sand grouse, a desert bird, dips its feathers into water and then flies to its chicks, who suck the water off the feathers when they are thirsty!

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                     Yes, indeed! It is not wings, or beaks, or the ability to lay eggs that make a bird a bird. Some mammals lay eggs, and have beaks (like the duck-billed platypus), and some others can fly (like the bat). Reptiles like snakes and crocodiles also lay eggs.

                       However, it is feathers that differentiate a bird from other creatures. Birds are the only creatures that possess feathers.

                    It all started some 200 million years ago, when some smaller dinosaurs made their homes among rocks on high cliff sides. By doing this, they were protecting themselves from larger meat-eating dinosaurs that were too big and heavy to climb over loose rocks. It was here that the pterodactyls (meaning ‘wing finger’) were found. They were flying reptiles, and their ability to fly helped them to escape from the clutches of an enemy, and to swoop down to grab food.

                  During this period, many small reptiles were evolving characteristics, which separated them from the reptile group – their feathers. The Archaeopteryx was the most familiar of these early reptilian avian.

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                    About 9,000 different species of birds exist today in our world. They come in all sizes, forms, and colours. There are brightly coloured parrots and macaws in tropical America, and large cassowaries and emus that cannot fly in Australia. Tiny warblers and sparrows are found in temperate America, and ducks, bustards and cranes in India. Gulls and vultures soar through the skies the world over. Plump chickens and turkeys are found in farmyards everywhere.

                   There are two main bird groups- paleaeognathae and neognathae. The paleaeognathae, includes birds that first evolved during the Cenozoic Era, after the dinosaurs became extinct-mostly ratites such as ostriches, emus and kiwis. The neognathae can trace their roots much farther back into the Mesozoic Era, and includes all other types of birds.

               The number of fish species runs to more than 20, 000 in the entire world! They can be classified into three broad categories: bony, cartilaginous and jawless. These species are spread across various biospheres. Around 10,000 species are found in freshwater; whereas, around 20,000 live in saltwater. There are also fish species that can live both in fresh and salt Water.

               The most commonly found fishes fall in the category of bony fishes. Tiny bones make up the skeleton of these fishes. They also have scales all over their body. They breathe through gills that appear at both sides of their head.

                On the other hand, cartilaginous fish have skeletons made out of cartilage. Cartilage is a kind of flexible tissue, and it is less brittle than bone. Sharks and rays have cartilages instead of brittle bones. As you may have observed, sharks have several gill slits on either side of their heads. They do not have scales like fishes. However, they have little interlocking teeth that make up its tough skin.

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               If you carefully analyse the fish in your aquarium, you would see a skeleton inside its body. The parts of the skeleton are a skull, backbone and fin supports. The skull of a fish has a cranium, and visceral arches. The bony cover that surrounds, and protects the brain is called the cranium. The visceral arches in the body of a fish support of its gills. These arches are also called the gill arches.

               The backbone of a fish is series of disc like bones. The backbone protects the spinal cord of the animal. There are thin, needle-like ribs that extend from the backbone toward the belly. This structure supports the entire body of a fish.

               Many fins are found in the body of a fish. Each fin has a large support at its base. They have two sets of fins, which are paired. One pair is called the pectoral fins, which lie just behind the head, one on both sides; and the other pair is called the pelvic fins, which may be far back on the body or under the head. The pelvic fins are smaller than the pectoral fins and are always on the belly side of the fish. Other fins of the fish are generally un-paired. It means that there is only one of each. The dorsal fin is found at the centre of the back of the fish. Fishes have an anal fin on the belly side too, just in front of the tail. The tail of the fish is called the caudal fin.

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          Can you imagine rivers, lakes or great oceans without fishes? These animals make grand water bodies livelier. However, millions of years ago, there were no fishes in waters!

          Scientists who study fossils to place various prehistoric organisms say that the first fish probably came into existence about 500,000,000 years ago, in the Ordovician Period.

          The ancient fishes did not have the kind of mouth fishes have now. They were jawless. They just had a small opening as their mouths, with which they ate only tiny organisms found hidden in the mud. These fishes gradually evolved and spread in number to other bodies of water later. During the Devonian Period, fishes were the most common animals in the planet. Therefore, the period is also known as the age of fishes.

          Jawless fishes and fishes with jaws became abundant during this time. Ostracoderms were a group of jawless fishes. However, they soon became extinct.

          The jawless fishes died out because fishes with jaws were evolving. Early fishes with jaws are called Placoderms. Do you know that the sharks and bony fishes of the present day come from Devonian Placoderms?

                  Vertebrates represent the majority of life in the phylum Chordata. There are more than 65,000 species among vertebrates. Of these, the fishes constitute the majority. There are thousands of fish species across the globe. The fish diversity is spread across lakes, rivers, streams, seas, bays and oceans. They are found in the cold Arctic, in the hot tropics and in other temperate zones. When it comes to the number of species or individuals, fishes outnumber all other vertebrates.

                   Do you know that a scientist who studies fishes is called and an ichthyologist? The word comes from two Greek words: ‘ichthyos’, meaning fish, and ‘logos’, meaning study.

               Have you ever gone fishing in a lake or river? From time immemorial, fish has been close to Man either as food or pet.

               Like human beings, fishes have backbones. There is a general misconception among common people that all animals that live in water are fish. That is manifest in addressing certain animas such as shellfish, starfish and cuttlefish as fish. However, that is incorrect because they are evidently different from true fish. The previously mentioned animals are invertebrates-animals without backbones.

               There are mammals too. Whales and porpoises cannot be categorized as fish as they are mammals that have adapted to life in the sea. These animals cannot breathe underwater like fishes, as they have to come up to the surface to breathe.

               Fishes, therefore, are aquatic animals with vertebra that live and breathe in the water. They have special anatomical features that help them in water such as gills, fins and scales. These animals possess basic vertebrate features, such as a brain, eyes, ears, blood, muscles and bones.

            Snakes in India are treated with not only fear but also prayerful worship. However, many a species is in grave danger because of several reasons.

            The most important of them is deforestation. The felling of trees is a big blow to reptiles. Most reptiles live in forests.

            As India’s population grows rapidly, forests are disappearing and reptiles face the danger of being wiped out. Highways that cut through forests are deadly for these hapless animals. Many meet their end under wheels of vehicles as they try to cross these roads. Although many snakes eat rats and thus help farmers, all snakes mistakenly believed to be dangerous, and are killed in every encounter. Crocodiles are also killed for the same reason. Many species of turtles were used as food and medicine.

            However, there is improvement in these matters today, thanks to the efforts of wildlife officers, and the rising publicity about the threatened status of these turtles. The illegal pet trade is another threat to turtles.

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               Our Earth is a sanctuary of biodiversity and there are creatures with the strangest characteristics. One such animal is the tuatara.

               The tuatara is a strange reptile. It looks like a lizard; however, it is not a lizard. It is not a snake or turtle or crocodilian either. These creatures have remained beyond evolution as well. Tuataras have remained unchanged over millions of years. The tuataras in the age of the dinosaurs were the same as the tuataras of today. The tuatara is slow by nature. They grow slowly. Male tuataras grow to a length of 60 centimetres, but females are slightly shorter. The female tuatara lays 10 to 10 eggs in a shallow burrow. The eggs take long 15 months to hatch. This is the longest time for any reptile. Tuataras can live for over 120 years.

               Although snakes frighten us in several ways, it generally does not do so by flying! Snakes do not usually fly, because they do not have wings. However, if you ever go to Southeast Asia, you might see a snake flying over your head! If snakes do not have wings, how do they manage to fly?

               These snakes, in fact, are not really flying like a bird. They are merely gliding from one tree to another. A flying snake launches itself at high speed from a perch on a tree, raises its limbs, and flattens its body to form a kind of parachute. A flying snake cannot take an upward flight. They glide only downwards. It may even swish and contort itself in flight so that it can control where it lands.

               Flying snakes can hunt their prey in the air too, crushing small animals with their powerful jaws. A flying snake can glide as much as 24 metres in the air!

               There is a group of is islands 965 kilometres off the coast of Ecuador in South America. They were discovered in 1535, and are called Galapagos Islands. The islands were famous for the huge tortoises that lived there. The name of the islands derives from these reptiles. ‘Galapago’ in Spanish means saddle, and refer to the tortoise shell. It is believed that long, long ago these giant turtles must have arrived in the island from South America, on pieces of driftwood.

               Galapagos tortoises are the largest tortoises in the world. One of the most amazing facts about the Galapagos Giant Tortoise is that they keep growing for 30 to 40 years, reaching almost 1.5 metres. They also weigh about 227 kilogrammes. They are also the longest living of all vertebrates – that is, animals with backbones. Do you know these animals outlive humans? The oldest on record lived for 152 years!

               Throughout the 19th century, giant tortoises were valued by sailors as food supply. Thousands of these tortoises were killed and the species died out. The last surviving tortoise called Lone-some George died in 2012 at the Galapagos national park in Ecuador.

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            Some reptiles are excellent hunters. Crocodiles and alligators, in particular, are very clever at stalking, capturing and killing their prey. The gharial crocodile, which has a long narrow snout, eats mostly fish, and it captures its prey by a rapid sideways snap of its tooth-lined jaw. Alligators and crocodiles with broader snouts also eat fish, but their diets vary according to  their age.

            The young reptiles feed mainly on insects, spiders, crabs and small frogs. They will circle their prey with their bodies and with a sudden sideways movement of their jaws, trap them and eat them.

            Adult crocodiles and alligators eat small mammals, birds, turtles and other reptiles. They will approach their prey stealthily with their bodies submerged under water and only their eyes and tip of their snout above the water. When they are near the prey, they submerge themselves completely. With the help of their powerful tails, they reach up to the prey and capture them. Their vice-like, tooth-lined jaws snap shut with an enormous force and kills the smaller prey immediately. Larger animals are dragged underwater, drowned and then killed and eaten, sometimes over the span of several days.

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               We all have seen dragons in movies. These huge and fearsome animals can fly and spit fire. Have such animals ever existed in the past? Scientists say that, if we forget the fire-spitting part, these animals resembled a flying reptile that lived a long time ago!

               The Archaeopteryx was a part reptile and part bird that lived 150 million years ago. This animal is a wonderful example of an in-between creature, which is neither a bird nor a reptile fully. Several fossils of this reptile-bird have been found in fine-grained stone. The skeleton look like that of a dinosaur but it shows the presence of feathers. Feathers are the most important feature of birds and they have evolved from the scales of reptiles. The archaeopteryx had a toothed jaw, a long tail and a weak breastbone. Unlike the bones of birds, all the bones of birds, all the bones of the archaeopteryx were solid.

               Do you know there is an uncanny connection between the cuckoo and the crocodile? The feathers of the archaeopteryx tell us that the crocodile, in fact, is related to the cuckoo.

What do we know about the archaeopteryx?

               The first bird to inhabit the Earth is believed to be the archaeopteryx (meaning ‘ancient wing’). It was a cat-sized bird, with several reptilian features. It had a beak containing sharp teeth, claws on its wings, and a long tail with bones in the middle. They had wings, feathers and a furcula. The furcula, or wish bone in birds, is a forked bone that joins the right and left shoulder joints. Not much is known about this bird’s direct ancestors or descendants.

                  Have you noticed the long thin teeth of squirrels and mice? In their representations in comics and cartoons, their incisors are portrayed as their distinctive feature. Remember the squirrel of the movie, Ice World!

                  Squirrels and mice belong to the family of rodents. Rodents are the largest family of mammals. They are also known as ‘gnawing animals’ because of their large incisor teeth and the way they eat. The two long pairs of incisors are used like chisels to gnaw on hard food items like nuts and wood. These incisors grow continuously since they are worn down by gnawing.

                  There are three major types of rodents. They are squirrels, mice and porcupines. Squirrel-like rodents such as the squirrel and gopher have bushy long tails and large eyes. They live in trees or underground in tunnels. Mouse-like rodents include the mouse, the rat and the hamster. Rats and mice often live near humans, sometimes in their buildings, so they can live off human food and garbage. Porcupines differ from other mammals because they have long, sharp quills on their backs for protection. The smallest rodent is the northern pygmy mouse, which is only 2.5 centimetres long, while the biggest is the capybara of South and Central America, which measures up to 1.2 metres in length.

                  The animals that we know have certain distinct features that help us identify them. The erect ears of a rabbit, the trunk of an elephant, the tail of a monkey or the shining eyes of a cat are such features that separate them from other animals. What would we call it if an odd animal gets some of the distinctive features of other animals?

                  The aardvark is a mammal found on the African continent. The name ‘aardvark’ means “earth pig” in Afrikaans as it refers to its resemblance to a pig and to its habit of digging the earth. The aardvark is very strange looking animal indeed. Though it has the body of a pig, it has the ears of a rabbit and a tail of a kangaroo! The animal hunts at night for termites and ants. It uses its long, sticky tongue to gather the insects from their nests, as anteaters do. Therefore, the mammal is really like a jigsaw of different animal parts put together!

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                  We know that teeth are essential to eat food. Not all the teeth in our mouth have the same function, though. We use the teeth in front of our mouth for shredding and cutting hard substances such as meat. Those at the back are generally used for chewing food.

                  Some mammals, however, have no teeth at all. Some, on the other hand, have very weak teeth. These are called ‘toothless mammals’. Sloths, anteaters and armadillos belong to this group. Some toothless mammals have small ‘pegs’ at the back of their mouths, which they use for chewing. They do not have frontal teeth to bite into things.

                  In fact, these mammals do not need frontal teeth, since they either lap up their food or slowly chew leaves. Anteaters lap up and chew soft-bodied insects like ants and termites, while sloths eat leaves and fruits, which require only gentle chewing. Though armadillos are ‘toothless’ they manage to eat earthworms, insects, small reptiles as well as the flesh of dead animals.

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                  Human beings generally stay in a place for a long time. However, many animals live in the same place for a short period of time and move on to another place.

                  Some animals, including mammals, migrate or travel long distances in search of warmer climates and food or for reproduction. Some travel from one part of the world to another, past oceans, over plains or through the sky on a definite route. There are species that travel thousands of miles every year, while others make the trip just once in their lifetime.

                  Many mammals spend spring and summer in the cool northern hemisphere. During autumn and winter, when food becomes scarce, they move south in search of a warmer climate and more abundant supply of food.

                  Mammals also move from one place to another for the purposes of mating, gestation, birth and raising their young. Many ocean mammals travel thousands of miles to reach their traditional breeding grounds. For example, grey whales spend their winter in sheltered lagoons off the coast of California, where their young are born. One of the largest caribou herds in North America, on the other hand, travels up to 5,000 kilometres each year in a journey to reach its ancient calving grounds and then it goes back south to its winter range.

                  Marine biologists have now found that the mammal that has the longest migration is the humpback whale. The humpback whale is known to travel from Central America to its feeding grounds in Antarctica – a whooping distance of over 8000 kilometres!

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                  We all know that the primary purpose of our clothes is to protect our bodies from cold or warm climates. However, what do animals do, since they do not wear clothes? The thick fur coat on their body helps them keep their body warm.

                  Mammals are the only animals with hair. A mammal’s hair, also called fur, protects it from wind, rain, sun, cold, insects, and other dangers. Most mammals have a fur coat with two distinct layers-an undercoat of shorter dense hair and an outer coat of longer stiffer hairs.

                  Hair helps mammals in many other ways too. The hair colour of many mammals blends with the animals’ surroundings; and therefore, helps them hide from their enemies or prey. The coat keeps out the cold and helps to keep the animal warm. It also serves to protect the skin. Hair can take on several different forms including fur, whiskers, spines, or horns. It can be kinky or straight, soft or bristly, stiff or smooth.

                  Do you know that the polar bear has fur on the pads of its feet, both to keep its feet warm and to help it get a good grip on icy surfaces? The hairs of its thick waterproof coat are hollow, which means that air is trapped inside each strand of hair. The trapped air holds in body heat and helps the bear float when it swims too.

                  While the brain coordinates and controls our body and mind, the heart plays the role being the motor that keeps the working of body steady. When the heart stops, living beings die. Therefore, the heart is one of the most vital organs of our body. A mammal’s heart is designed in a very special way.

                  All mammals have hearts with four chambers. Two of the chambers are on the right side and two are on the left. The two chambers on the right side receive blood, which carries impurities from the body. They pump it to the lungs. In the lungs, the blood passes out waste gases and receives fresh oxygen. The blood is, then, pumped to the two chambers on the left side from where it is carried to various parts of the body. This is how the heart of a mammal generally functions.

                  Since a mammal’s heart has two sides and two chambers on each side, scientists say that mammals have ‘two-in-one’ hearts.

               We know that a mammal is an animal that delivers its children and breast-feeds them. Do all mammals follow these rules? Are there mammals that lay eggs instead of delivering young ones?

                The platypus and echidna are special mammals because they lay eggs! These animals do not give birth to live babies as other mammals do. The platypus is found in burrows near streams in Australia. Its eggs are round and white with wrinkled shells. The mother platypus guards and keeps the eggs warm for 10 days, until they hatch. The babies drink the milk that oozes out of pores on her underside.

                Echidnas, on the other hand, carry their eggs in a pouch that forms on their belly. After mating, a female echidna digs a burrow, curls up her body, and lays one egg directly into her pouch. The egg hatches in about 10 days. Inside the pouch, the baby echidna drinks milk from its mother’s body. When its spines start to grow, the baby leaves the pouch. The female will feed her baby until it is about 6 months old.

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               Have you ever thought of the wonder of how a new life is brought forth in the form of a baby? We all have spent a considerable amount of time in our mother’s womb before seeing the light of this world. Most mammal babies live inside their mothers before they are born, just like us. When the baby is big enough, it comes out of its mother’s body. Baby mammals come out of their mother’s body in some odd ways too: some mammals lay eggs while others have a pouch in which they nurture the immature babies.

               Despite the diversity of the ways in which some baby mammals are born, they all drink milk that comes from their mothers’ bodies. Baby pigs, dolphins, bats and elephants all drink milk! Mother’s milk is essential for the survival of baby mammals. Due to this reason, mammal mothers have to take good care of their young. The length of time varies from a few weeks for mice to many years for humans!

              Mammal mothers nurse their babies, clean them and keep them warm. The mother is responsible for the protection of her baby, and she teaches it to look after itself. With the case of a few exceptions, male mammals do not care for their young. Some may hunt and help to guard the babies; however, the mother mostly takes on the responsibility of bringing up the babies. Therefore, it is no wonder that mammal babies are generally attached more to their mothers than to their fathers.

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               Physical prowess and the intelligence required to use it to one’s advantage for better adaptation practices are what an organism needs for dominance in nature. Mammals were able to become lords of the earth primarily because of the high level of development of their brains. This gave them the capacity to absorb information, to learn and to remember, making them superior to all other animals.

               Mammals also became dominant because of the way their body evolved and adapted. Some developed hooves and became grazers on the grasslands of the world. Others developed hunting skills and became meat eaters. Some mammals developed wings and took to the air while others adapted to life at sea. Land dwellers developed four limbs, which they used for moving about most efficiently. Many mammals developed sharp curved claws and tails that were adapted for living in trees. Others developed thin membranes of fur-covered skin that stretched between their legs, which allowed them to glide.

               Do you know the only mammals that can fly? They are bats. Most mammals can swim while some have special adaptations that make them expert swimmers. Seals, sea lions and walruses spend most of their time in water, while sea cows and whales live in the water from birth to death.

               The hair and teeth of mammals are adapted to suit a wide variety of habitats and different types of food. Mammals have also learnt to protect themselves and many have deadly weapons to attack their enemies.

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            Sometimes, myths and stories are more believable than truth, because it is difficult to digest when one says that we humans have evolved from less complex animals. In fact, science says that the present day mammals come from giant reptiles that ruled the world thousands of years ago.

             About 200,000,000 years ago, reptiles ruled the earth. The age of the reptiles is known as the Mesozoic Era, Remember, dinosaurs were present in that era. Gradually one set of reptiles began to change. They started to grow coats of hair and became warm blooded. Instead of laying eggs like other reptiles, they kept the eggs inside their body. The babies grew inside the mother’s body until they were born as live young ones. In short, these reptiles had evolved into mammals.

                 The first mammals were very tiny and timid creatures. These early mammals were small, nocturnal, hairy, and warm-blooded and ate mainly insects. Later as conditions on Earth changed and dinosaurs disappeared from the face of the earth, mammals began to grow bigger. They also started to spread out until they took over the world!

          How many kinds of mammals can you think of? Even if we start counting the mammals that we encounter every day, the number would be very high. There are about 5,000 species of living mammals.

          Mammals are divided into three sub-classes, and about 26 orders. They display a remarkable array of adaptation abilities. Their intelligence enables them to inhabit a wide range of habitats. They vary in size from the minute bumblebee bat, which measures a mere three centimetres in length, to the magnificent blue whale, which can measure 33 metres from head to tail. The main orders of living mammals are given in the box here.

MONOTREMATA: Mammals that lay eggs. Example: Platypus

MARSUPIALIA: Their young are very immature at birth; females usually have pouches. Example: Kangaroo                        

INSECTIVORA: Small insect-eating mammals. Example: Mole.                                                

DERMOPETRA: Gliding mammals. Example: Flying lemur

CHIROPETRA: Mammals with wings. Example: Bat                                                          

PRIMATES: Mammals with highly developed nervous systems; most have opposable thumbs. Example: Monkey                                                          

EDENTATA: Mammals that usually have simple, peg-like teeth. Example: Anteater                              

PHOLIDOTA: Mammals with coverings of overlapping scales. Example: Pangolin                                     

LAGOMORPHA: Small-to medium-size mammals with clawed toes; tails are either stubby or lacking. Example: Rabbit

RODENTIA: Gnawing mammals. Example: Rat

CETACEA: Water-dwelling mammals with fish like forms. Example: Whale

CARNIVORE: Flesh-eating mammals. Example: Dog

TUBULIDENTATA: Long-snouted, long-clawed, insect-eating mammals. Example: Aardvark

PROBOSCIDEA: Huge mammals with trunks. Example: Elephant

HYRACOIDEA: Small, rodent like mammals with hooves. Example: Hyrax or rock rabbit

SIRENIA: Water-dwelling mammals with flippers, paddle-shaped tails, and no hind legs. Example: Manatee

PERISSODACTYLA: Hoofed mammals with odd numbers of toes on each hind foot. Example: Horse

ARTIODACTYLA: Hoofed mammals with even numbers of toes on each foot. Example: Cow

               How did Man become the most prominent animal in Nature? It is partly due to Man’s intelligence and ability to adapt and adjust. Mammals, in general, are more intelligent and creative than others and have the ability to adapt to adverse environments.

               For these reasons, mammals are considered the most advanced and probably the most popular class of all the classes of animal life. They are the only animals that possess true hair and have the capacity to produce milk.

               Their superior brains, warm blood and the way they care for their young have given them a great advantage over other animals in the struggle for survival.

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               What is the difference between a cow and a caterpillar? The question seems very silly because the difference is very explicit. Mammals are special because they are the most advanced of all the different classes of animal life. They are also the animals that we know best, because most of our pets, from dogs and cats to squirrels and rabbits, are mammals.

               Mammals are one of the commonest animals as they are found almost everywhere, from the Arctic snowfields to burning deserts and from tropical jungles to lofty mountains. Mammals are the ruling animals of the world today.

               Mammals live on land, at sea, in the air, and even underground. All mammals, from bats to whales, share a number of important traits that make them different from other animals. Mammals are warm-blooded, they have fur or hair, and most mammals give birth to live babies—rather than laying eggs. Mammals are superior to all other animals in the care and protection of their young. The female nurses the babies with milk that is produced by special glands called the mammary glands. In fact, they are the only animals that produce milk. Naturally, this makes them truly special!

               Life on earth is sustained by reproduction. There is so much diversity in reproduction too. The way in which a chick comes to life is different from the way a calf is born. Mammals are those animals that deliver young ones, and breast feed them.

               Mammals are one of the six main classes of animals. These classes are categories of animals that scientists consider to be alike in some important ways.

               A mammal is placed at the highest level of vertebrates, animals that have a backbone and a spinal cord. Human beings are mammals too. All female mammals give birth to live babies, with the exception of the platypus duck and the spiny anteater, which reproduce by laying eggs. However, regardless of how their babies are born, all female mammals nurse their young with milk, which they produce from special glands called the mammary glands.

              Another important characteristic of mammals is their lungs. They breathe in air for oxygen supply in their bodies. A mammal is warm-blooded. This means that their bodies are built to maintain just about the same temperature all the time. Warm-blood allows the mammals to be very active and live in a wide variety of places.

               Most mammals are covered either partially or completely with hair or fur. There are about 5000 types of mammals, including chimpanzees, elephants, bears, horses, pigs, bats, camels, mules, dogs and cats.

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            Vertebrates are called so by virtue of their vertebrae, backbone. Therefore, the most special characteristic of vertebrate animal is this spectacular bone system. Vertebrae are the small bones forming the backbone. The vertebrae connect together by joints to form the backbone.

             The backbone not only supports the body, it also protects the spinal cord. All vertebrates have a skeleton, usually made of bones, inside their bodies. The skeleton of a vertebrate grows as the animal grows. The skeleton has three main parts- the skull, backbone and limbs.

                 Another characteristic of vertebrates is their hard skulls. These skulls protect the organs in their head. This may be the reason for the high intelligence of vertebrates. The protection of the skull helps brain development, and a result allows the enhancement of intelligence as a result.

               Most vertebrates have two pairs of limbs. In fish, the limbs take the form of fins, while others they have become legs and arms, or wings or flippers. Vertebrates like snake have no external limbs.

              Most vertebrates have stronger muscles and skeletons. These features help them to perform complex movements. All vertebrates have a fixed body structure.

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               Man’s existence depends on not only the other members of his society, but also on various animals around him. Most big animals that we associate within our daily life are vertebrates. Some common vertebrate animals are cows, dogs, cats, bears, giraffes, rabbits, ducks, alligators, frogs, and turtles. Vertebrates are animals with backbones.

               There are five main groups of vertebrates: mammals, birds, fish, reptiles and amphibians. Mammals are animals that have a covering of hair on the skin. They generally give birth to their young, which are breastfed by their mothers.

               Fish are vertebrates that live in water, breathe through gills, and have fins. They have an elongated body covered with scales. Birds, on the other hand, are egg-laying, feathered vertebrates. Their forelimbs have been modified to form wings in the process of evolution. Reptiles are vertebrates that lay eggs. Some of them are snakes, lizards, crocodiles, turtles and dinosaurs. They have an external covering of scales or horny plates.

               Amphibians, such as frogs or salamanders, are smooth skinned vertebrates, capable of living both on land and in water. They have gills when they are born. However, when they become adults, they develop lungs too.

               Vertebrates can be split further, into warm-blooded and cold-blooded animals. A warm-blooded animal, such as a dog or a man, keeps its body temperature the same, except when it is sick. Cold-blooded animals have fluctuating body temperature. It changes according to the surroundings. So if the weather is hot, the animal is warm, and if the weather is wintery, it turns cold!

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               Life underwater is so diverse and numerous. For Man living on the dry land, animals in the sea with strange forms and colours instill wonder and curiosity. For a long time, all living marine animals were fishes for him. The starfish, although not a fish, is such an animal. Today, scientists are in the process of renaming the animal as the sea star.

               The sea star is an echinoderm. Echinoderms are free swimming marine organisms that are found at all depths of the sea. Starfish, sea urchins, and sea daisies are some common echinoderms.

               Most starfish have five-arms. But some have as many as 45! There are more than 2000 different species of starfish. Their sizes range from less than 25 millimetres to almost 90 centimetres across. They come in a variety of colours ranging from bright red to yellow and orange. Grey and green are also found.

               The most remarkable thing about starfish is their power of regeneration. If you cut a starfish into three pieces, it will grow back as three starfish! Regeneration usually requires that the piece of starfish includes at least one arm and part of the central disc. But in some kinds of starfish, a whole animal can be regenerated from the piece of a single arm.

               There is an eye at the end of each arm, usually marked by a red spot. Star fish have feet that look like tubes. These tube feet help them move. A starfish has hundreds of feet. The mouth of a starfish is at the centre of its underside.

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               Insects are so common that we hardly spend a day without seeing them. Have you noticed the body of an insect?

               Insects have certain common features. Most insects have wings and antennae. The three parts of an insect’s body are the head, thorax and abdomen. The thorax is the middle region and the abdomen is the lower region.

               While insects have many similarities, they also come in all shapes, sizes and colours. Insects are extremely diverse in nature. In fact, there are almost one million different species of insects!

               One of the most common flying insects is the mosquito. Mosquitoes are considered to be the deadliest animal in the world as they have caused the deaths of millions of people.

               Insects are one of the largest groups of animals, with over 7,50,000 species that can be found on Earth. Insects generally have three pairs of walking legs. Some have wings, and some do not. They have a waterproof layer on the outside of their bodies, which helps them to move to environments where other organisms cannot survive.

               Some other common insects that can fly are the ladybug, bee, dragonfly and moth.

               The octopus does not have a backbone. In fact, the octopus has no bones at all. Its body structure allows the animal to hide in a little place and hunt under the sea.

               The octopus is a fascinating creature. It is found in shallow waters in most areas of the world. It has eight long limbs or tentacles, lined with suckers, protruding from a globe shaped head called the mantle. It uses two of its tentacles like legs to walk on the sea floor and to push off when it wants to swim. It also has the ability to grow back a tentacle if it loses one.

               The octopus has no skeleton at all, so it is able to squeeze through the smallest spaces. It has a sharp beak and toothed tongue which it uses to drill into the shells of its prey, or to force the shells open. Once it breaks open the shells, it injects a poison into its prey to paralyze it.

               The octopus is highly intelligent and also has the uncanny ability to change its colour, texture and body posture to blend in with its surroundings. This proves very useful both when it is hunting and when it wants to hide from its enemies. Another way it escapes is by releasing a cloud of purple-black ink so that the enemy can no longer see it.

               The mimic octopus can change its skin colour and texture to mimic not just one, but many other sea creatures! This fascinating creature was first discovered in 1998 off the coast of Indonesia.

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               It is unlikely that you are familiar with the name ‘mollusc’. However, you may be surprised when you learn that they are some common animals that we come across in our day-to-day life. A snail is a mollusc.

               Molluscs are a large and diverse group of invertebrates, belonging to the Gastropods species. They include a variety of familiar animals well-known for their decorative shells or as sea food. Tiny snails, clams, and squid, cuttle fish and octopuses are just some animals that belong to this group.

              Molluscs have soft bodies, and get their name from the Latin word ‘mollis’ which means ‘soft’. Some of these animals have very beautiful shells. Snails have twisted shells, while others have shells that are pearly or iridescent.

               Molluscs have a body part called a foot. Their foot is much like our foot, because it helps them move about.

               Molluscs also have a special feature called radula. The radula is a sharp tongue-like body part that is used to scrape food off hard surfaces and push it into their mouths.

              The giant calm is the largest mollusc. A giant calm can weigh upto 340 kilogrammes. They are beautifully coloured. Their mantle is usually a mixture of yellow, red, green, blue, pink and brown colour and each of them has a unique combination of colours. They have thick, bony zigzag shaped shells that cannot be closed completely.

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               Although the jellyfish has ‘fish’ in its name, it is not a fish. It is not made of jelly either.

               Unlike a fish, it is an animal without a backbone found in oceans and seas around the world. The name jellyfish derives from the jelly-like bodies of these animals.

               Jellyfish are found in oceans and seas all over the world, in the deepest as well as in shallow water. Some species thrive in salt water, others in fresh water. Jellyfish are possibly the oldest multi organ animal on this planet. Some scientists believe that they existed as far back as 700 million years ago.

               Jellyfish can be large or small, brightly coloured, transparent or translucent. They look like little umbrellas, with a gelatinous bell shaped body and trailing tentacles. Inside their bell-shaped body is an opening that is its mouth. They feed on fish, shrimp, crabs and tiny plants. They eat and discard waste from their mouths.

               As a jellyfish squirts water from its mouth, it is propelled forward. Jellyfish use their tentacles to sting. Most are harmless to humans but stings from some species, such as the box jellyfish, can be very painful and sometimes kill. They do not have any brains!

               The lion’s mane jellyfish, the largest jellyfish on the planet, has a mass of thin tentacles that resemble a lion’s mane. These jellyfish are found in the Arctic, North Atlantic and North Pacific Oceans.

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              Have you seen pictures of colourful coral beds under the sea? Some coral reefs are tourist attractions as visitors can go scuba diving there, and enjoy the biodiversity under water.

              Coral polyps are hard working little animals, no bigger than a match’s head, which together, build enormous coral reefs. They are invertebrates that live in colonies. Since they are small, and stay in one place, they are in danger of being attacked by larger animals.

              So, they construct hard chalky skeletons around their bodies. It is these skeletons that form the frame work of coral reefs. Corals are attached to the sea floor. Even through corals look like plants, they are animals. They stay in one place and live in groups.

              Coral reefs may look like rocks. They are made up of tiny little animals called polyps. As polyps die, they become hard and new polyps grow on top of them. This process continues until a colony is formed.

              As colonies grow over hundreds and thousands of years, they join with other colonies and become reefs. Some of the coral reefs on the planet today began growing over 50 million years ago. Corals live in tropical waters throughout the world.

              The largest coral reef is the Great Barrier Reef located off Queensland, Australia. The Great Barrier Reef stretches for 2600 kilometres.

              Coral reefs teem with life. Though they cover less than one percent of the ocean floor, they support 25 percent of all marine creatures. Coral reels are very important because they are home to some of the most strange and interesting creatures on this planet.

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               When we hear the word sponge, what comes to our mind first may be the sponge that we use to mop a wet surface or absorb water.

               The sea sponge is a type of invertebrate animal that lives in the world’s oceans. Sea sponges can be of many different colours, sizes, and shapes.

               They are the simplest multi cellular animals. They do not move around much but stay in one place. The surface of a sponge has many small pores or tiny holes.

               Water that is laden with food particles passes into its body through these pores. There are over 5,000 known species of sponges. They can be found attached to surfaces anywhere, from the shallow water near a beach to the depths of the ocean. Some types of sponges have been found to live over 300 years! Sponges can live in both warm and cold water as well as in both deep and shallow water. Sea sponges can only survive in saltwater, so if we put them in freshwater, they will quickly die. They are also very sensitive to air.

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               Invertebrates, as the name suggests have no vertebra; and therefore, most of them do not have the ability to stand erect or walk on legs. They are multi-cellular too. Their cells are working together for the survival of the organism. All of the cells have specific duties and responsibilities.

               Invertebrates do not have cell walls, whereas plants have them. One of the most important characteristics of animals is that they have no cell walls. Even though no insect looks like an animal, this quality makes it an animal.

               Most of them have tissues that are specific organizations of cells. Most invertebrates can move. Even sponges move when they are very young and very small. Once they settle down, they do not move anymore. Other invertebrates like lobsters and insects move around their whole lives. Most invertebrates are organized in a symmetrical way. Symmetrical organization means when you can draw a line down the middle of the organism and the two sides look like mirror images. If you draw a line down the middle of an octopus, you would find two sides with equal parts. However, sponges and some coral are not symmetrical.

               Invertebrates cannot make their own food; and are, therefore, heterotrophic. Heterotrophs feed off other things to get their energy. Plants are autotrophic. They make their own food. Being heterotrophic is one of the main characteristics of being an animal.

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               There is so much diversity among invertebrates. This diversity prevents classifying them under a single over-arching category. Scientists have identified more than 30 phyla of invertebrates. Since vertebrates have a single identifying factor called vertebra, it is not difficult to classify them. However, invertebrates are any other animals classified outside of that class. Let us look at some of them in detail.

               A wide variety of interesting ocean animals that are invertebrates includes sponges, corals, jellyfish, anemones, and starfish.

               Molluscs, another category of invertebrates, have a soft body that is covered by an outer layer called a mantle. Many molluscs live inside a shell, but not all of them. Some examples of molluscs include squid, snails, slugs, octopuses, and oysters.

               Crustaceans are a type of arthropod. Arthropods are characterized by jointed legs. They also have an exoskeleton, meaning that their bones are on the outside like a shell. Some examples of crustaceans are crabs, lobster, shrimp, and barnacles.

              Worms are invertebrate animals that do not have legs. Worms may live in the soil, in the water, or even inside other animals as parasites. Some examples include the tapeworm, the leech, and the earthworm.

              Insects are part of the earth’s largest animal phylum, the arthropods. There are over 1 million species of insects including the grasshopper, dragonfly, yellow jacket, butterfly and praying mantis.

              Spiders, centipedes and scorpions are all part of the arthropod phylum. Spiders and scorpions are arachnids because they have eight legs. Centipedes and millipedes are myriapods and have many legs. Some myriapods have as many as 750 legs. Some example species include the tarantula and black widow, which are both spiders.

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            Most invertebrates that we are familiar with are very small. We often associate the smallness of an ant, a caterpillar, or a grass-hopper with insignificance. Therefore, we have no remorse when such small insects die. However, invertebrates play a very important role in the eco-system.

            As invertebrates are generally small, they can hide in places where larger animals cannot catch them. Therefore, their size is an advantage when it comes to protecting themselves. In spite of their small size, these animals play a key role in maintaining the balance of nature.

            Invertebrates play various roles in nature. Those that are herbivores keep plants and trees in check. Some invertebrates are carnivores, eating other invertebrates as well as larger animals, to prevent the overpopulation of some species. Others are parasites, keeping the number of a certain type of plant or animal under control. Perhaps most important of all, some invertebrates eat dead animal and plant matter. This releases important nutrients back into the environment so that other plants and animals can use them again.

            Most invertebrates also provide food for other species of animals, and even for carnivorous plants like the sundew. Therefore, though most invertebrates are small, they are far more important to the ecosystem than all the mammals, birds, reptiles, amphibians and fish put together.

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              Which is more intelligent: a dog or a mosquito? You will not think twice to answer the question. Bigger animals tend to be smarter and more intelligent. However, does their skeletal system have anything to do with their intelligence?

              It is not wise to generalize about smartness and intelligence when it comes to invertebrates. They are diverse in size and form. There are hardly any similarities among species as different as enormous moths, ethereal medusas, skittering scorpions, or stationary sponges. However, there is no need for any debate on this: the lack of a backbone may mean they are ‘spineless’, however, that does not mean that all of them are mindless!

              Cephalopods, squid and octopus in particular, are some of the most intelligent invertebrates. They are capable of learning quickly and retaining information. Spiders learn to weave better webs through trial and error. Honeybees learn to recognize their hives. At the same time, curiously enough, starfish and sponges do very well with no brains at all!

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               Can you observe some of the animals around you? It would be interesting note that most big animals such as a cow, a dog or a cat have strong internal skeletal structure. Now look at some small organisms such as a butterfly, a beetle or an earthworm. They do not possess an internal bone system. Does size have anything to do with such differences?

               Most invertebrates are small because they lack internal skeletons. An external skeleton is an inhibitor and makes it difficult for an animal to grow further. If it grows too big, it will not fit inside the skeleton. If the skeleton grew bigger to accommodate the animal’s increasing size, it would become too heavy for the animal to carry.

               However, it would be wrong to assume that all invertebrates are small. Invertebrates that live in the sea can grow quite big. There are giant clams in the South Pacific that are 1.2 metres across, and weigh a quarter of a tonne! Giant squids can reach a length of 17 metres, and weigh a tonne!

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            Those animals with backbones have a much more developed skeletal structure and tend to be stronger than invertebrates. Therefore, invertebrates have to look for other means to protect themselves from danger.

           Many invertebrates have strong shells that substitute for a backbone. These external structures play an important role in their survival. The shells protect the invertebrates from predators. They also prevent their bodies from drying up when they are out of water.

          Other invertebrates have developed various ways to defend themselves. Some brightly coloured sea slugs taste so terrible that other animals do not want to eat them. Sea anemones possess numerous stinging tentacles, and sharp spines shield the sea urchins body. These are just some of the ways by which invertebrates survive.

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              What, do you think, would happen if we had no backbone? Our backbone not only supports our body, but also enables us to walk erectly. Without a backbone, vertebrates in general would not be able to survive in nature.

              However, as we have already seen, not all animals have backbones. Then, how do they survive? Internal and external skeletons help an animal to survive without a backbone. Some invertebrates have internal skeletons that support and protect their internal tissues. These skeletons are made up of different materials. Sponges have a framework of silica or other substances that stiffen their bodies. Others have external skeletons in the form of shells. Invertebrates belonging to the molluscs group have shells made of calcium carbonate, while those that are anthropods have external skeletons made up of a substance called chitin.

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              Have you seen the picture of the skeleton of a man? A strong backbone system supports our body. Man is able to stand erect or walk because of his backbone. Invertebrates are animals without a backbone. Of the millions of species of animals on the planet, 97 per cent are invertebrates. Common examples of invertebrates include snails, clams, insects, spiders, worms and molluscs.

              Do you think that all animals on Earth have the same body structure? Do insects such as caterpillars and bees have backbones like mammals such as bears and sloths? Even though they are all animals, insects and mammals have very different body structures! Caterpillars and bees are invertebrates.

              In the animal kingdom, invertebrates are actually the largest group. They make up 97 per cent of all animals on the planet. The total number of invertebrate species could be over 30 million. This number is much higher than that of the vertebrates, which is about 60,000. Invertebrates are also very diverse. They include animals living on the land and those living in the sea. Some examples are earthworms, centipedes, flies, sea stars, jellyfish and crawfish!

             Invertebrates have a long history of existence on Earth. Fossil records show that invertebrates even existed 600 million years ago. Invertebrates also have a big impact on other animals’ lives. They are a major food source for other animal species such as birds and fish. In agricultural production, some of them act as pests and parasites. This includes bugs like grasshoppers and ladybugs.

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              Classifying animals into groups was based entirely on observation initially. Our observation has a limited scope because we rely exclusively on our senses, which can sometimes deceive us. However, today, with modern equipment with more precision and accuracy, Man is able to do this job better.

              Animal classification now uses sophisticated scientific methods to identify relationships among species. Since the methods used to classify animals are continuously changing, there is the probability that the groups in which species are placed may change too. Occasionally, new species are identified!

               For example, until recently, elephants were classified into two species: African and Asian elephants. But DNA studies conducted in 2010 revealed that African elephants actually are of two distinct species- African bush elephants and African forest elephants. This, there are three species of elephants in the world now!

              Do you know that all the animals that we know have separate scientific names? Sometimes, it is very difficult to recall these names too. However knowledge of their scientific names would help us categorize animals according to their similarities and differences.

              The system of naming that we follow today is called the binomial system. It is the formal method of naming different species. Under the binomial system, each species is given a scientific name that is formed by the combination of two terms: the genus name and the specific descriptor.

              The genus is the major subdivision into which organisms are classified. The descriptor is the category into which the organism falls. For example, the scientific name for man is ‘Homo Sapiens’. ‘Homo’ is the genus name for animals that have large brains and use tools. ‘Sapiens’ is the category that pertains to modern humans.

              Here is a list of the binomial name of some common animals: Dog – Canis lupus, Cat – Felis catus, Horse – Equus caballus, Goat – Capra aegagrus hircus, Donkey – Equus asinus, Cow- Bos Taurus, Tiger-Panthera Tigris, Lion – Felis Leo, Indian Elephant- Elephas maximus indicus.

                 From the time language originated, Man starter naming animals. His scientific temper prompted him to order and categorize all living and non-living things for easier understanding. Man observed, named and compared animals and plants.

                 Aristotle, an ancient Greek philosopher, was the first known man to introduce the classification of animals. He classified species according to various characteristics, including whether they gave birth or laid eggs, or whether they were warm or cold-blooded.

                 The Roman naturalist Pliny the Elder wrote Naturalis Historia, a large work in which many plants were described. Naturalis Historia is also considered the first encyclopedia.

                 Over the years, animal classification became more scientific. The 16th century Italian philosopher Andrea Cesalpino classified plants according to their fruits and seeds.

                 The English naturalist John Ray published works on botany and zoology in the 17th century. He classified species according to the similarities that he observed, and was the first person to offer a scientific definition of the word species.

                 The Swedish botanist Carl Linnaeus of 18th century is known as the father of modern taxonomy. He popularized the binomial naming system, and introduced the use of kingdoms, classes, orders, genera and species. The Linnaean system is still in use today.

            When you are going to appear for an important examination, how would you prepare? If you try to read everything that comes your way, you would not be able to secure the best results. Studying something in a structured and orderly fashion makes it easier for comprehension. Ordering and classifying animals makes it easier to study them. Animal classification is the process of identifying, naming and organizing animal species into groups. The branch of science that deals with animal classification is known as taxonomy.

            Animals can be classified into two main groups: vertebrates and invertebrates. Vertebrates have backbones, while invertebrates do not. In all, there are more than 8 million animal species in the Kingdom Animalia and most of them are invertebrates.

            Each living organism is classified into Kingdom, Phylum, Class, Order, Family, Genus, and Species. There are five kingdoms. The two main kingdoms are animals and plants. Animalia includes animals and plantae, plants. The other kingdoms are Protista that includes single-celled organisms, Fungi that includes yeast, moulds, mushrooms etc., and Monera that include Bacteria.

            Some scientists say that there are five kingdoms, while for some others there are six. Other than Animalia, Plantae, Fungi, and Protista, they consider Archaea and Bacteria as other different kingdoms. For some other scientists, Monera is the fifth one, which includes Archaea and Bacteria.

          How many kinds of animals do you know? If you start writing down the names of the animals that you know, the list would be very long. There are innumerable animals in the world. However, we have found ways to classify them too.

          There are a million different kinds of animals, belonging to different species. Scientists have divided them into two main groups – those that have a backbone or vertebrates, and those that do not have a backbone or invertebrates. Some vertebrates are cats, dogs, horses and humans. Jellyfish, sponges, octopuses and squids are some examples of invertebrates.

          Within the vertebrate group, there are five different classifications. These classifications are mammals, fishes, amphibians, birds and reptiles.

          Of the millions of species of animals on Earth, 97 percent are invertebrates. Common invertebrates are insects, spiders and worms. Some of the major invertebrate groups are Porifera, Cnidaria, Platyhelminthes, Nematoda, Mollusca, Annelida, Echinodermata and Anthropoda.

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Science was never satisfied with the creation myths of various religions that explained the origin and development of life on Earth. Charles Darwin, an English naturalist, provided a solution in the form of a theory called the Evolution Theory in 1859.

            According to Darwin, the living things we see today have evolved gradually over millions of years. This theory also says that different species may show some similarities because they have evolved from a common ancestor. Charles Darwin explained that different species evolve by a process known as natural selection.

            The characteristics of each individual are determined by extremely small pieces of genetic material called genes. Genes are present in the nuclei of the body’s cells. Sometimes, certain changes, known as mutations take place in the genes. These mutations cause the formation of new characteristics in individuals. Some mutations are harmful, and make it difficult for the babies to survive. Animals that possess these harmful mutations may not be able to compete with other animals for food and space to live. Therefore, they will gradually die. Other mutations make animals more fit and able to survive in new conditions. These animals will gradually increase in number. In this way, Nature selects those animals and individuals who are best suited to survive in a changing environment. This is called natural selection.

            The giraffe is an excellent example of natural selection. Animals that had longer necks than others were able to reach up higher and get more food. They survived, while those with shorter necks could not compete with them and, therefore, died.

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          While the oceans provided the most conducive atmosphere for the occurrence of life, the dry lands offered further opportunities for growth and development. In the process of evolution, the movement of animals from the oceans to land was an important milestone.

          In the earliest stages of life on earth, organisms lived only in the sea. Single-celled organisms gradually developed into multi-celled organisms. The first forms of plant life were algae, lichens and mosses. These plants provided food for the early forms of animal life in the sea.

          In the course of time, in fact, millions of years, new forms of plant life developed. These new plants were more complex. They had some new features such as roots, stems and leaves, which made it possible for them to survive on land as well. Giant horse-tail plants and tree ferns started growing on land, mostly in wet, swampy areas on land.

         When there was food available on land as well, animal life gradually began to evolve in order to survive on land. The availability of food was an important factor in the movement of animals to land. The first animals to move to land were probably worms and other soft-bodied invertebrates. They were followed by certain fishes that developed limbs to crawl and lungs for breathing. Reptiles that could live on both land and water came next. Such animals, as you know, are called amphibians.

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            We cannot travel to the past to see how life began on Earth. All we can do is to speculate and hypothesize. Some scientists tried to recreate the prehistoric past when life was non-existent and the earth had just started cooling down. Stanley Miller, an American chemist, conducted many experiments in this regard and tried to prove how life came into existence.

             Miller conducted an experiment in 1953, which shed light on the sprouting of life on Earth. He filled a laboratory flask with a mixture of gases.

            These gases were similar to those that made up the atmosphere of the earth billions of years ago. He then fired electrical sparks through the gases for a week. The electrical sparks had the same effect on the gases in the flask that bolts of lightning had on the earth’s atmosphere before the appearance of life.

            The results were revelatory. Miller discovered that a variety of substances had formed in the flask, including amino acids and sugars, which are necessary for life to occur. From Miller’s experiment, scientists concluded that the fierce flashes of lightning  that were common during the early days of the earth reacted with the gases in the atmosphere to produce the substances necessary for introducing life on Earth.

              Have you tried to stay underwater holding your breath? We cannot live in a sea or river like a fish, because our body cannot take oxygen from water. However, there are innumerable organisms in oceans. In fact, life began in water.

              Two-thirds of the surface of the earth is covered with water. Oceans and seas were formed very long ago, long before there were any plants, animals or people on Earth. The earth was made up of red-hot rocks then. When they cooled, they gave off steam. This steam became rain, which fell and filled up the hollows and deep holes in the earth’s surface to become oceans.

              The first life was not as complex and developed as it is found now. It probably was one-celled organisms. The first plants that appeared on this planet were microscopic, single-celled organisms floating in the world’s oceans, billions of years ago. That is why we say that life began in water, and not on land.

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            Life is what makes our planet different from the rest of the known universe. There are diverse forms of life on our planet. Living beings such as ants, beetles, fishes, sparrows, cats, dogs and cows have always fascinated us in several ways. Green plants like grass, shrubs, bushes and tall trees have also caught our imagination. While trees and plants are stationary, animals can move around.

            The word animal comes from the Latin word ‘anima’. It means ‘life’ or ‘breath’. Animals are living organisms, often belonging to a family or herd. They eat food, move about, and are capable of taking care of themselves. However, the simplest animals are very much like the simplest plants. Sometimes it is difficult to differentiate between the two.

            There are some telling differences between plants and animals. These are very clear when you look at the more highly developed animals. Plants have the ability to prepare their own food. However, animals eat plants or hunt down other animals. This characteristic of animals means that they have to be able to move about.

            On the other hand, things are not so clear-cut when you look at organisms that are made of only one cell. Sometimes, it is hard to tell if they are animals or plants. Bacteria, for example, can have characteristics of both animals and plants.

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