As of 2015, scientists are still pondering the advantages of bilateral symmetry for animals. Top among the possibilities is how this type of symmetry enables effective movement in purposeful and intentional directions for the animal, such as towards food sources or better environments, or away from danger.Know More
A feature of vertebrates and some non-vertebrates, bilaterally symmetrical body structures might also favor the development of complex central nervous systems, such as the human spinal cord and its vast network of nerves funneling into the brain. Scientists also believe bilateralism might foster the development of improved sensory organs, such as eyes and ears, that help to support the intentional and focused movements of which these types of symmetrical bodies are capable.
The other main type of symmetry found in the animal kingdom is radial symmetry. Unlike a bilaterally symmetrical body, which has only one axis about which it can be equally divided, a radially symmetrical animal can be divided into equal halves along one of several axes, so long as that axis passes through the body's center. A starfish is a good example of this type.
Bilateral symmetry first appeared in the fossil record some 550 million years ago, exhibited by a creature called an acoel. Only a few animals have body structures that exhibit no symmetry, the main example being sea sponges.Learn more about Zoology
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 >
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 >