Category Zoology

          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.