No animal on Earth has four knees, only two. All animal skeletons consist of essentially the same bones and joints, just expressed in different shapes or forms.Know More
All creatures that exist with four limbs, comprising the legs and arms, fall in the category of tetrapods. This word comes from Greece and means "four legs." The animals in this group all share the same basic skeletal structure, which consists of two arms, two legs, a torso and a head. Since all animals belong to this group, all animals have only two "real" legs and two "real" arms. So, although evolution may have shaped some species' arms into shapes that appear to be legs, they are still essentially arms.
Take a horse for instance. The two front legs are actually arms, just shaped that way over millions of years of evolutionary pressure. Because of this, there are no physiological knees within the front two legs of a horse. They are actually elbows that have been shaped to serve a similar purpose to the kneecap on the hind legs. In fact, horses have specialized their arm shape so drastically over the years that their hooves are actually nothing but their middle fingers.
It should be pointed out that not every tetrapod is equipped with four limbs in modern times. Whales have partially lost some of their limbs, with fragments still being visible in skeletons. Additionally, snakes have completely lost all four of theirs.Learn more about Zoology
The peregrine falcon, or Falco peregrinus, is the fastest bird and the fastest member of the animal kingdom. When swooping or diving, it reaches speeds of up to 200 miles per hour. It is native to North America and historically known as the duck hawk.Full Answer >
Given the timescales involved in animal evolution and the difficulty of identifying new species as their first members emerge, there is no single species that could be said to have evolved most recently. Some animals, however, have populations that do not breed together and could be regarded as emergent species.Full Answer >
An animal that hunts other animals for food is called a carnivore or predator. These animals must kill other smaller animals to feed. Since carnivores must hunt to survive, they use large amounts of energy to obtain their food, and thus they require many calories to stay healthy.Full Answer >
Bears, deer and wolves are examples of omnivores, herbivores and carnivores respectively. Many animals that are considered carnivores, such as foxes, actually eat plants as well. Not only do red foxes eat fruit, but they sometimes eat carrion.Full Answer >