Caecilians

Caecilian (sēsĭl`ēən), any of the legless, tailless tropical amphibians belonging to the order Gymnophiona (or Apoda). Most adult caecilians resemble earthworms superficially but have vertebrate characteristics such as jaws and teeth.

Caecilians range in size from 7 in. to 4.5 ft (18 cm–140 cm); most are about 1 ft (30 cm) long. Their bodies are ringed with grooves, which in some species contain small scales imbedded in the skin; possession of scales is a primitive amphibian trait. There is a groove on either side of the head, each containing a retractable sensory tentacle. The eyes of caecilians are nearly functionless, and some species are eyeless.

Caecilians are found in swampy places in most tropical parts of the world, but are seldom seen because of their burrowing behavior. They eat small invertebrates such as termites and earthworms. A few species remain aquatic as adults and resemble eels.

There are more than 180 species of caecilians, divided into 10 families. They are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Gymnophiona (or Apoda).

Source: http://encyclopedia2.thefreedictionary.com/caecilians

Chimpanzee

Chimpanzee, an ape, genus Pan, of the equatorial forests of central and W Africa. The common chimpanzee, Pan troglodytes, lives N of the Congo River. Full-grown animals of this species are up to 5 ft (1.5 m) tall and weigh about 150 lb (68 kg); they have an arm spread of up to 9 ft (2.7 m) and are much stronger than humans. They are covered with long, black hair over most of the body and have naked faces ranging in color from nearly white to nearly black. The pygmy chimpanzee, P. paniscus, now usually called the bonobo, lives south of the Congo. It is a bit smaller and more slenderly built, with a black face.

Chimpanzees spend much time on the ground, where they walk on all fours, using the soles of the feet and the knuckles of the hands; they can also stand on two legs and sometimes walk this way for short distances. They climb trees in pursuit of food and for nesting and can swing by their hands from branch to branch. Their diet consists largely of fruit and other plant matter, but they also hunt and eat small animals, including monkeys. They use and even make primitive tools; for example, they collect termites using twigs and crack nuts using stones. Many primatologists now attribute culture to chimpanzees, noting learned variations in such skills and habits among different groups.

Chimpanzees move about the forest in bands of varying composition, usually numbering six to ten individuals. The males of a group engage in dominance contests involving much screaming and stamping. Family groups consist of mothers and offspring; females mate with many males during their fertile periods. A single infant is born every three to eight years; young chimpanzees ride about on their mothers' backs. Under ideal circumstances chimpanzees may live 50 years.

Although incapable of speech beyond their own simple vocalizations, captive chimpanzees have been taught to communicate in a language using visual rather than verbal symbols. Because of their close evolutionary relationship to humans they are often used for medical and behavioral experimentation, but the degree to which chimpanzees and humans are genetically close is a subject of dispute, with estimates of the amount of DNA the species share ranging from 94.6% to 99.4%. Chimpanzees, especially bonobos, are considered endangered species because of hunting and loss of habitat.

Chimpanzees are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Primates, family Pongidae.

Insect

Insect, invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates.

The body of the typical adult insect is divided into three distinct parts, the head, thorax, and abdomen. The head bears three pairs of mouthparts, one pair of compound eyes, three simple eyes (ocelli), and one pair of jointed sensory antennae. The thorax is divided into three segments, each with a pair of jointed legs, and bears two pairs of wings. The abdomen has posterior appendages associated with reproduction. The exoskeleton is composed of a horny substance called chitin.

Insects breathe through a complex network of air tubes (tracheae) that open to the outside through a series of small valved apertures (spiracles) along the sides of the body. In chewing insects the digestive system includes a muscular gizzard that is lacking in sucking insects. The simple circulatory system is composed of a tubular heart that pumps blood forward into the head, from which it diffuses through the tissues and back into the heart. The aquatic larvae of many insects breathe by means of external gills; some very primitive species breathe directly through the body wall.

Insect Species

There are about 900,000 known insect species, three times as many as all other animal species together, and thousands of new ones are described each year. They are commonly grouped in 27 to 32 orders, depending upon the classification used. The largest order is that of the beetles (Coleoptera). Next, in order of size, are the moths and butterflies (Lepidoptera); the wasps, ants, and bees (Hymenoptera); and the flies and mosquitoes (Diptera). Other major orders are the true bugs (Hemiptera); the cicadas, aphids, and scale insects (Homoptera); the grasshoppers and crickets (Orthoptera); the cockroaches (Blattodea); and the mantids (Mantodea).

Insects are found throughout the world except near the poles and pervade every habitat except the sea (although there is one marine species of water strider). Fossil records indicate that many species exist today in much the same form as they did 200 million years ago. Their enormous biological success is attributed to their small size, their high reproductive rate, and the remarkable adaptive abilities of the group as a whole, shown by the enormous variety in body structure and way of life. The mouthparts may be adapted to chewing, sucking, piercing, or lapping and the legs for walking, running, jumping, burrowing, or swimming. Insects may feed on plants or decaying matter or prey upon other small animals (especially other insects) or parasitize larger ones; they may be omnivorous or highly specialized in their diets. They display a remarkable variety of adaptive shapes and colors that may serve either as camouflage or as warning (see mimicry). Some have stinging spines or hairs and blistering or noxious secretions, used for defense.

Reproduction

A few species, notably the fireflies, produce light, used as a signal in courtship, by a chemical reaction. The sexes are separate in insects, and reproduction is usually sexual, although in many insect groups eggs sometimes develop without fertilization by sperm (see parthenogenesis). In some insects, such as bees, unfertilized eggs become males and fertilized eggs females. In others, such as aphids, all-female generations are produced by parthenogenesis. Eggs are usually laid in a sheltered place; in a few insects they are retained and hatched internally. After hatching, the insect must molt periodically as it grows, since the rigid exoskeleton does not allow much expansion. A new, soft exoskeleton forms beneath the old one, and after each molt the insect undergoes a rapid expansion before its new covering hardens. The stages between molts are called instars; the final instar is the adult.

Trilobite

Trilobite (trī`ləbīt'), subphylum of the phylum Arthropoda that includes a large group of extinct marine animals that were abundant in the Paleozoic era. They represent more than half of the known fossils from the Cambrian period. The trilobite body was generally oval and flat and was divided into three roughly equal sections: the head, thorax, and tail. The name trilobite refers to a pair of furrows along the length of the animal that divided the body into three longitudinal regions. The body was covered by a mineralized shell. Because the dorsal, or upper, shell was thicker than the under shell, it has been the part best preserved in fossil form. Trilobites were abundant inhabitants of the Cambrian and Ordovician geological periods. They declined thereafter, possibly because they became food for cephalopods and later for fish, and became extinct in the Permian period. Trilobites are most closely related to the chelicerates, which include the horseshoe crabs and spiders.

Mastodon

Mastodon (măs`tədŏn'), name for a number of prehistoric mammals of the extinct genus Mammut, from which modern elephants are believed to have developed. The earliest known forms lived in the Oligocene epoch in Africa. These were long-jawed mastodons about 4 1-2 ft (137 cm) high, with four tusks and a greatly elongated face. Their descendants in the Miocene epoch were the size of large elephants, the latest forms having long, flexible trunks, like those of elephants, and only two tusks. During Miocene times they spread over Europe, Asia, and North America. The mastodons were forest dwellers; they obtained their food by browsing and their teeth were more numerous and of a simpler form than those of the elephant. They were apparently extinct in the Old World by the early Pleistocene epoch but survived in North America until late Pleistocene times. They are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Proboscidae, family Mammutidae.