Jointed Limbs






Anime image: The cheetah is believed to be the fastest animal on Earth, reaching speeds of more than 97 km/h (60 mph) while chasing prey. Wildebeests, gazelles, impalas, and other hoofed mammals make up much of the cheetah’s diet. Cheetahs generally stalk their prey to within 10 m (33 ft) and then burst into a sprint to close the gap. Studies indicate that approximately half of the chases initiated by the cheetah are successful.

Jointed limbs are found in only two groups of animals: the arthropods and vertebrates. An arthropod's limbs are made of a number of hard tubular segments, which form part of its external skeleton, or exoskeleton. The muscles that operate them are hidden away inside this strong outer framework. In vertebrates, the plan is reversed. The bony skeleton forms an internal framework, with muscles attached around it.


Funny animal: The way a bird flies depends on the shape of its wings. Most small birds flap their wings the entire time they are airborne, while gulls and other large birds with long, pointed wings soar or glide. The fastest fliers have sharply tapered wings.

During the course of evolution, both these kinds of limbs have become modified in many different ways. Aquatic animals often have paddlelike limbs that push against the water, enabling them to speed away from predators or after food, or to maneuver their way around confined spaces. On land, the fastest animals, such as the horse and cheetah, have long legs and a flexible backbone, which helps to increase the length of their stride. Land animals that move by jumping often have highly developed hind legs, with extra-large muscles. In fleas, the muscles squeeze an elastic material called resilin, which flicks the legs back when released. This extremely rapid flick is faster than a jump triggered by muscles alone, and it throws a flea up to 30 cm (12 in) into the air.

Many animals can glide, but only insects, birds, and bats are capable of powered flight. The fastest flying insects are dragonflies, which can reach speeds of about 29 km/h (about 18 mph) in short bursts. However, in terms of speed and endurance, birds are by far the most successful animal aviators. Swans and geese can cruise at 64 km/h (40 mph) for many hours at a time, while peregrine falcons can briefly reach 145 km/h (90 mph) when they swoop down on their prey.

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