by	Keanan Fox

Ecology Ecology is the branch of science that deals with the relationships living things have to each other and to their environment. Every animal cannot survive without some other non-living or living organisms in its surroundings. For example, if you took away the certain plants that a horse eats it would most probably die of starvation. All the animals in the world depend on plants, even humans if there were no plants there would be no oxygen and if there were no animals there would be no carbon dioxide. Animals breath in oxygen and then they breath out carbon dioxide. Then the plants take in this carbon dioxide and release oxygen and then the cycle keeps repeating. Animals also rely on non living thins to survive as well like take the worm it lives in the dirt. The worm also gets his energy from eating the dirt.

Ecosystem In simplest terms an ecosystem is an ecological community together with is environment, functioning as a unit. An ecosystem is the most complex level of organization in all of nature.  Ecosystems are made up of a community of living organisms and all the  abiotic material around them. This includes climate, soil, water, air, nutrients, and energy. Ecosystems come in lots of different sizes. Some ecosystems are as big as a rain forest and some are the size of a small puddle. Ecosystems are made up of abiotic and biotic factors.

To have a healthy ecosystem you must have predators and prey to keep each others populations down. Keeping the population down and at the right levels is what makes an ecosystem healthy. Take the rabbit, for example.  If there were no predators around the keep the population down the rabbit population would get out of control. The rabbits would start competing against each other for food, water and shelter. It would start to get to the point where the rabbits would start to die because they had no food or water. It is very important to have diversity of animals in ecosystems. Think of an ecosystem as a play and each animal has a different role. That's what it is kind of like in the real ecosystem. Each animal helps the ecosystem in some way. So the more different kinds of animals the more healthy the ecosystem is. Some animals can't survive with out another animal. this is called a symbiotic relationship. There are three kinds of symbiotic relationships; mutualism, commensalism, and parasitism. Mutualism is when both animals benefit, commensalism is when one animal benefits and the other nothing happens, parasitism is when one animal benefits and the other animal is harmed. An example of mutualism is the sea anemones and the clown fish. The clown fish live in the anemone for protection, and in return the clown fish cleans the  anemone.

An example of commensalism is the shark and the remora. The remora has a sucker and it attaches its self to the shark and eats the scraps and leftovers from the sharks meal. The shark doesn't care.

An example of parisitism is the tapeworm. The tapeworm goes into the stomachs of living things and then eats all the food that the animal eats. Eventually the animal starves and dies.

Foodwebs Muskrat

Bibliography http://www.answers.com/topic/ecosystem World Book