What Is an Animal?
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general WHAT IS AN ANIMAL? dinosaurs and they all developed spines independently, an example of convergent evolution. Another example is prehensile tails. A number of diverse and unrelated species have developed tails that can be used as another limb, such as New World monkeys, kinkajous, porcupines, tree-anteaters, marsupial opossums, pangolins, skinks and chameleons. TAXONOMY peacock jumping spider Taxonomy is the science of the classification of organisms. It is estimated that around nine or 10 million species of It’s been called “the world’s oldest profession,” and naming animals inhabit the earth, although the exact number is not and classifying our surroundings has likely been taking place known and estimates are rough. All members of the animal as long as mankind has been able to communicate. It would kingdom are multi-cellular and all are heterotrophs, which have been important to know the names of poisonous versus means they rely on other organisms for nourishment. They edible plants and medicinal plant illustrations show up in are the eaters of the earth and most animals ingest and digest Egyptian wall paintings from c.1500 BCE. Historical records food in an internal cavity. Most animals reproduce sexually as show that informally classifying organisms took place at least well, by means of eggs and sperm. Animals range in size from back to the days of Aristotle (Greece, 384–322 B.C.), who microscopic to many tons (blue whales, the largest animals was the first to begin to classify all living things and to this potter park zoo docent manual 2017 manual docent park zoo potter ever known to have lived on Earth, have hearts that weigh as day we still use some of those definitions (i.e., invertebrate, much as a car.) vertebrate). The Swedish botanist Carolus Linnaeus is regarded as the father of taxonomy; he developed the The group with the most species by far is the insects, with system known as Linnaean classification for categorization groups such as mollusks, crustaceans, and nematodes also being of organisms and “binomial nomenclature” for naming especially diverse. Only about one out of a hundred animals is organisms. Binomial nomenclature is the formal system of a vertebrate (has a backbone); 99 percent of the earth’s animals naming all living things by giving each separate species a are invertebrates. name composed of two parts, Genus and species. EVOLUTION WHY IS CLASSIFICATION IMPORTANT? Evolution is change in the inherited physical or behavioral Animals are classified based on shared characteristics. This traits of biological populations over successive generations. classification starts with broad, general traits (kingdom) Changes that allow an organism to better adapt to its and narrows to more specific characteristics (species). These environment will help it survive and have more offspring. The groupings usually show the evolutionary relationship between theory of evolution by natural selection was first formulated in species. Animal taxonomy ranks are: kingdom, phylum, class, Charles Darwin’s book “On the Origin of Species” in 1859. order, family, genus, species. (There are also sub phylas, super orders, infra orders, sub families, etc., and scientists often debate Evolution by natural selection is one of the best substantiated how different groups should best be organized. Groups can also theories in the history of science, supported by evidence from seem rather fluid, especially with new DNA discoveries and a wide variety of scientific disciplines including paleontology, genome mapping. For our purposes, however, the major groupings geology, genetics and developmental biology. All life on Earth should be sufficient.) is connected and related to each other and this diversity of life is a product of modifications of populations by natural For example, let’s look at tigers. Most broadly, all tigers are selection, where some traits were favored in an environment in the phylum Chordata (or vertebrates, which means they over others. have a backbone). They are in the class Mammalia, which means they have hair and nurse their young with mammary In evolutionary biology, convergent evolution is the process glands. Mammals are divided into about 29 orders, and tigers whereby organisms not closely related independently are in the order Carnivora (meat eaters). The carnivores are evolve similar traits as a result of having to adapt to similar divided into about 13 families, one of which is the cat family environments or ecological niches. For example, several (Felidae). The felines are further divided into about 18 genera, mammal groups have independently evolved spines: echidnas one of which is Panthera, aka the big cats. Tigers are classified (monotremes), hedgehogs, and some tenrecs (a diverse group as Panthera tigris, and Potter Park Zoo exhibits Amur tigers of shrew-like Madagascan mammals). The last common (Panthera tigris altaica), which are a tiger subspecies. ancestor of all of these groups was a contemporary of the general WHAT IS AN ANIMAL? When we discuss animals using their scientific name, it The correct answer is Buteo buteo, or common buzzard, a bird might seem like it makes things unnecessarily confusing and of prey whose range covers most of Europe and extends into difficult. But scientific names serve a distinct purpose: when Asia. Cathartes aura, or turkey vulture, is commonly refered using a scientific name, one can be sure that we’re all talking to as a buzzard in North America, but is distantly related to about the same animal. For example: which one of these actual buzzards. birds is a buzzard? Cathartes aura Buteo buteo EXAMPLES OF TAXONOMIC CLASSIFICATION kingdom Animalia phylum Chordata Chordata Chordata Chordata Arthropoda Arthropoda class Mammalia Mammalia Aves Repitila Arachnida Insecta order Carnivora Artiodactyla Falconiformes Testudines Araneae Blattodea family Mustelidae Suidae Cathartidae Emydidae Theraphosidae Blaberidae genus Lontra Sus Sarcoramphus Chrysemys Grammostola Gromphadorhina species L. canadensis S. scrofa S. papa C. picta G. rosea G. portentosa common North American Chilean rose-haired Madagascar Guinea hog King vulture Painted turtle name river otter tarantula hissing cockroach general WHAT IS AN ARTHROPOD? Class Arachnida Class Chilopoda Class Crustacea spiders, mites, scorpions centipedes shrimps, crabs, lobsters An arthropod (from Greek arthro-, joint + podos, foot) is CLASS INSECTA (insects) an invertebrate (no backbone) animal having an exoskeleton With around one million named species and perhaps several (external skeleton), a segmented body, and jointed times that number unnamed, insects account for a great appendages. Arthropods form the phylum Arthropoda and majority of the species of animals on earth. They are a include insects, arachnids, and crustaceans. There are far tremendously successful group and are found in almost all more species of arthropods than all other animal species terrestrial and freshwater habitats, from the driest deserts to combined, and the number of undescribed species in the freshwater ponds, from the canopy of a tropical rainforest potter park zoo docent manual 2017 manual docent park zoo potter largest class of arthropods, the insects, probably numbers in (where their diversity is unbelievably great) to the arctic wastes. the tens of millions. For example, there are 20,000 bee species Their feeding habits are similarly varied; almost any substance worldwide, 200 of which are found in Central Park, NYC, an that has nutritive value is eaten by some group of insects. area of just 1.3 square miles. Another example is moquitoes: there are more than 3,500 species of mosquitoes worldwide, Insects also show huge variety in shape and form. Almost about 175 of which are found in the United States, and about the only condition their group does not attain is very large 60 species are found in Michigan. body size. A number of features, however, are shared by most kinds of living insects, including a body composed of three Arthropods’ bodies comprise of segments: the head, thorax segments (head, thorax, and abodmen); a pair of relatively large and abdomen, which themselves can be fused or segmented compound eyes; a pair of antennae; two pairs of wings; and even further. Arthropods generally grow by molting their three pairs of legs. exoskeletons in a process called ecdysis. The exoskeleton is primarily made of chitin. Most arthropods have a pair of The manner in which growth is accomplished is an especially compound eyes and one to several simple (“median”) eyes; important characteristic of insects. In almost 90 percent of either or both kinds of eyes may be reduced or absent in some insect species, newly hatched young are completely different groups. Fertilization, with with paired reproductive organs in appearance from adults. These larval forms usually live (ovaries, testes), is internal in most but not all groups. Most in different habitats, eat different foods, and assume a body arthropods lay eggs and development often proceeds with form completely different from that of their parents. The larva some form of metamorphosis (larval stage, for example). feeds and grows, molting its skin periodically. At some point Order Diplopoda Class Insecta Class Merostomata millipedes insects horseshoe crabs general WHAT IS AN ARTHROPOD? CLASS CRUSTACEA The coconut crab is the largest land-living (crabs, lobsters, shrimp, krill, barnacles) arthropod in the world with a weight of There are approximately 30,000 species of crustaceans, the up to 9 pounds (4 kg)and a length from majority of which are marine. All have two pairs of antennae, leg to leg of up to 3 feet (1 m). a pair of mandibles (jaws), and a pair of compound eyes (usually on stalks). Their bodies have three segments: head, A spider eats about 2,000 insects a year. thorax, abdomen, although the head and thorax may be fused together to form a cephalothorax, which may be covered by a The most dangerous animal in the world? single large carapace. Probably the blood-sucking female mosquito, responsible for more than In many groups of crustaceans, the fertilised eggs are simply one million human deaths every year.