There are no animals that have 4 knees. All quadruped mammals have 2 knees at their back legs and then elbows and wrists at the front.
There is a common misconception that elephants are the only animals that have 4 knees, but elephants are the same as all other quadruped mammals, like horses and dogs, in that they have knees only in the back legs. Skeletal images clearly depict that the front leg joint bends in the same way as human elbows rather than knees. In animals like the horse, the front joint that looks like a knee is more appropriately compared to a human wrist, making the long lower leg more comparable to the third metacarpal of a middle finger. All mammals' skeletal structures are very similar due to the fact that they descend from common ancestors.
In addition, all tetrapods, which are all vertebrates with 4 limbs, and those animals whose ancestors had 4 limbs like snakes are also based on similar structures. These common limbs all share 2 long bones that combine tarsal bones in the back and carpal bones in the front. All of these limbs also have 5 digits. Even in animals that have less than 5 digits, the 5 digits are present in embryonic state.Learn More
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 >
There are many species of animals on Earth that spend the majority of their lives alone, including species of reptiles, amphibians, mammals, fish, insects and arachnids. Solitude is common in the animal world, and it may be only during the mating season that individual members of a species interact with each other.Full Answer >
Animals are an integral part of the Earth's ecosystem. Each organism in the ecosystem plays a role in supporting the ecological community, which means that animals play a vital role as well. Each organism in the ecosystem depends on the other organisms in the system to play its role. Without animals, there would be dysfunction within the system and human life would be disrupted.Full Answer >
Zoos may be good or bad for animals, depending on the cleanliness of the facility, quality of the establishment, knowledge of zoo staff and other factors. Arguments supporting keeping animals in zoos argue zoos save animals from high risks of extinction. Arguments opposing housing animals in zoos cite the lack of replicating true environmental conditions, which jeopardizes the health and happiness of resident animals.Full Answer >