Реферат: Flora and Fauna of the USA

We should not also forget that USA has a very big coastal line. That means that we must eximine the marine life also, because it is one of the part with a ll American life consist of. So…One of the most famous animals is sea otter. Lolling on a kelp bed along the Pacific Coast, shielded from frigid water by luxurious fur, the sea otter seems to lead an easy life. Its ancestors once lived on land. After taking to the sea eons ago, they did not develop a blubbery layer beneath the skin, as whales did. The otter depends for protection from the cold on the blanket of air trapped in its densely packed fur, a fur so fine is almost doomed the species. Said Captain James Cook after acquiring some pelts from Nootka Indians in 1778: "The fur of these animals . . . is certainly softer and finer than that of any other we know of ." Sea otters were already being killed for their pelts by Europeans, Asians, and North Americans. Cook, China-bound, took furs with him. The demand and the slaughter grew. The fur trade nearly wiped out the species. In 1911 the United States, Great Britain, Russia, and Japan agreed to stop the killing. The near-shore animal has made a substantial comeback in the Aleutian Islands and off the California coast south of Monterey. It shows promise where it has been transplanted. The sea otter, 4 to 6 feet long (122 to 183 cm), usually weighs 33 to 66 pounds (15 to 30 kg), but may reach 100 pounds (45 kg). The male is the largest North American mustelid. Females are about 20 percent smaller. Adults first breed at about four years, courting and mating in the water. A single pup - rarely two - is born six to eight months later. With no margin for error in a litter of one, the newborn is better developed than most mustelid pups, arriving eyes-open with a mouthful of milk teeth. For a year the pup will nurse, nap, and be groomed. Its mother will carry it on her chest while she swims on her back. Males usually live apart. Grooming is not a mere nicety. If the otter’s coat - containing some 800,000,000 fibers - gets soiled or matted, the trapped air is lost and with it buoyancy and insulation. Oil spills and other pollution - and competition with commercial fishermen for some of its favorite foods - are among the problems that still menace the otter.

Surprisingly it exist not only sea otter in America , but also river otter. The engaging river otter cavorts in and out of water through most of the United States and Canada, appearing to enjoy life thoroughly. It can live near people and seems to like showing off for an audience. The otters sleek, streamlined body, with short legs and webbed feet, enables it to swim at speeds reaching seven miles an hour. Adults are as long as 511 inches (130 cm), including the fleshy, tapered tail that serves as a prop on land, a rudder or oar in water. Otters mate in the water, usually in winter or early spring. Male and female then go their separate ways. One to five pups are born nearly a year later in a riverbank den the female prepares - perhaps after evicting a muskrat or beaver. At about 12 weeks, the young venture out of the den. Soon they are swimming and expertly hunting their favorite foods - fish, crayfish, frogs, insects, and small mammals. This adept aquanaut can easily dive to 35 feet. Flaps of skin close its nose and ears and its pulse rate slows, allowing it two minutes underwater before it must pop up for air.

It must be dangerous but North America is also the home of Scorpions. Scorpion poison is usually used in capturing food. With their claws, scorpions capture insects and immobilize them with their venom. Sadly, sometimes people get stung when scorpions defend themselves, or when disturbed or annoyed. Similar to the spider's venom, scorpion venom injures the soft body parts or nervous system of the prey. Many people think that a scorpion sting causes death, but in truth, few species produce this reaction. As a matter of fact, many people have been stung by scorpions and survived to relate their story. In the US only Centruroides sculpturatus causes death, though other sings may be compared to that of a bee sting. Number of deaths caused by scorpions increase rapidly in countries of India, Pakistan, or other dry areas. Because they weigh less than adults, most fatalities are that of young children. Media exaggeration of this causes fear from the public. According to fossils, the scorpions' appearance have changed little over 350 million years. A fossil found in Scotland suggests that scorpions were twice as large then as they are today. Gigantoscorpio (the fossil) is 16 inches long while the largest alive today is 8 inches. Maybe the fossil is a remainder of an extinct scorpion species. There are more than 700 different kinds of scorpions. Five families of scorpions live in the United States. Buthidae makes up the largest of these families, consisting of over 300 species. It also makes up many of the species which are dangerous to man. Vejovidae is the most common family of scorpions found in the US. An exoskeleton makes up the hard outer surface of the scorpion, and sensitive hairs on this exoskeleton detect vibrations (just like spiders). Molting occurs so that the scorpion may grow to its full size. Furst, a new exoskeleton is produced underneath the old one, and the outer shell splits off. Then, the new soft exoskeleton bends and stretches into the new size before hardening. Like the spider, scorpions possess two main body parts; the cephalothorax which is basically the thicker part connecting to six pairs of appendages, and the abdomen which includes a tail with the sting protruding from the end. Most species range from one half to eight inches. The first pair of appendages include insignificant pincers. Large claws on the second pair seize and crush prey while legs make up the last four pairs. Their head consists of six to twelve eyes usually, and a breathing hole commonly located on the abdomen. Reproduction differs between spiders and scorpions. Rather than laying eggs, scorpions bear live young which cling to the mother for an amount of days. In courting, scorpions start with a dance of "holding hands" and walking around, every once in a while bringing mouth parts close for a "kiss." Next, the two jerk their bodies without leg movement. After this, the two tails curve over their backs to touch and even entwine with the other's. This now resembles a fight. Here's what is actually happening. In 1956 a scientist discovered this process to be the male fertilizing the eggs. Spermatophore, the small sperm packet, is glued to the ground by the male. He then leads the female to it, and they walk back and forth till she finds it with her genital opening. Often after this ritual the female will eat the unlucky male. Scorpion eggs stay inside their mother from four months to a year. When they come out, they are surrounded by a thin white sac, soon breaking open to soft shelled babies which cling to their mother. She doesn't feed them, but they take care or themselves after the first molt, several weeks later. When stinging prey, the scorpion curves its tail over its head and thrusts it into the victim in a whip like fashon. The sting wound causes a burning sensation, and closes up directly after the stab to prevent any poison loss. Area will become swollen and discolored resulting with a blister. Effects worsen without treatment which is why receiving medical attention is important. Hunting at night, spiders and insects make up their main diet. Also, being exposed to ultra-violet, these are fluorescent, and easy to spot by night with use of black light. On the end of the tail, the sting organ is made up of two glands which hold the poison.

Really very famous and very special for America is alligator. Alligators are an ancient group of reptiles consisting of only two species of the thirty in the order crocodylia. They differ from crocodiles by their teeth in pattern and arrangement, and also somewhat in the shape of their snouts. The alligators lower teeth point upward into pockets in the upper jaw so when they close their mouth only the upper teeth are left showing. The crocodile has both the upper and lower teeth showing, intermeshed. Their fourth tooth back is enlarged so that it may even end up above the upper jaw. The alligator is found only in the area of the upper Yangtse of China and in south eastern United States. It is believed that it may have once have ranged worldwide but was eventually forced out by the crocodile who are more aggressive. The alligators actually live longer than crocodiles but the crocs eat more which may have added to the problem. Alligators withstand cold better than crocodiles. In 65¡F water an alligator will still surface to breathe but a crocodile will sink and drown. For this reason the crocodiles live only in the most extreme south portion of Florida in the United States, while alligators extend their habitat north to the Carolinas, and west to Texas. Crocodiles are the most numerous of all the crocodilians. They take up space in most tropical regions, but the alligator family has a cousin that might help the alligator clan take back its former territory: the caiman. Caimans are even smaller than crocodiles and quite a few live in South America. These buggers have an apatite and temperment similar to the crocodile, and they are slowly taking the place of the crocodile. Unfortunately, the population of all in the crocodilian order has been majorly depleted by man. From 1880 to 1894 two and a quarter million alligators were slaughtered for their skins. Most states in which the alligator resides have laws protecting them but poachers continue to kill them and sell the hides to northern stats at an alarming rate. The Chinese alligator is protected by the government of China, but whether the population is increasing is unknown. Baby alligators were gathered by the thousands and sold in pet stores all over the Unites States so states had to begin controlling their export. Though baby alligator selling has been halted, their cousin the caiman has been sold in even greater numbers, forcing South American countries to place these species under protection and control. Crocodilians of all kinds make bad pets. Regular house hold temperatures are too low for their guts to work properly. This causes the babies' jaws to be deformed, have a humped back, or die after a few months. Even zoo's have a hard time raising the little critters on the right diet. Grown, the beasties are unpredictable. Alligators will eat anything that moves close enough to get grabbed and will get fit in their mouth. These carnivores prefer to swallow smaller things whole. They will eat large things if they have to, and shake them to dismember them.

And of course well known salamander. Salamanders are timid amphibians that look somewhat like lizards without scales. Most salamanders are small, half a foot or less, but the giant salamander of china and Japan can get 5 feet long, and the hellbender of the United States reaches 3 feet. Most salamanders lay their eggs in water but then live on land in rotten logs, caves, or under rocks. Mudpuppies and some other species are the exception to the rule and live their entire life in the water. On the other end, a few species never enter the water at all. Most salamanders have slimy dark skin and are difficult to see in their natural surroundings, but some species are brightly colored. Some brightly colored species let out a milky white fluid that is poisonous to some animals through their skin if they are handled roughly. Salamanders have long tails to help them swim. Most have four legs, but some that live in the water have only the two front ones. A good sense of smell and a long sticky tongue helps salamanders to catch worms and insects. After young salamanders have hatched they are called larvae. They look a little like frog tadpoles, but they have feathery gills on their head. It may take them anywhere from 42 days to 5 years to become adults. Just before they become adults they lose their gills. As adults the salamanders will breathe with lungs through the mouth and skin.

It is really impossible to describe all the divercity of wildlife in America in few pages. There are a lot of encyclopedias, monographies and researches about them and there is still remain a lot of unexplored. The best way to see and study flora and fauna of USA is to come there, join a group of the best friends, take a tent, a bicycal and enough food and go to the unexplored, remoted places in order to see with your own eyes all the diversity and beauty of animals and plants of North American continent.

Список литературы

Climate and Physiography of North America, Luc Brouillet R. David Whetstone , N.Y, 1995

Botany for the next mellenium, Christine Miot , Harward, 1998

Wildlife of the USA and its territories, John K. Francis, New Orleans, LA, 1987

Descriptive fauna of USA and ajacent islands, Lioger H.A., Harward University, 1994