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Chapter 14 - Ecosystems 14.1 What is an Ecosystem 14.2 Cycles Within Ecosystems 14.3 Kinds of Ecosystems 14.1 What is an Ecosystem? • Ecology – means “study of the house” or the place where one lives. It is the study of the interactions of organisms with one another and with their physical environment. • Community – the organisms that live in a particular place, such as a forest. • Habitat – the physical location of a community. Example: the habitat is the neighborhood and the community is the residents of the neighborhood. • Ecosystem – the sum of the community and the habitat. It is a self-sustaining collection of organisms and their physical environment. • Diversity – the measure of the number of species living there. The tropical rain forests are the most diverse terrestrial ecosystem having as many as 100 species of trees in the size of two football fields. • Ecology is studied to help prevent pollution, conserve resources and preserve the world for your children. • Ecosystems are very complex and normally function with interference by humans. Now some ecosystems require our help because we have caused them great damage. • It is difficult to determine how an ecosystem works because it can contain thousands of interacting species. • Two basic questions: – Where does the energy come from that is needed by particular animals and plants? – How do organisms in the ecosystem acquire adequate amounts of minerals and other inorganic substances they need? • Answering these two questions will give a good idea of how an ecosystem normally works. Then you can ask how an ecosystem might be expected to respond to a disturbance. Scientists make ecological models to predict how different changes would affect the whole system. • Every ecosystem requires energy. How many and what kinds of organisms live in an ecosystem is determined by the amount of energy available to the system. • Producers – organisms in energy from their surroundings and store it in complex molecules. Nearly all producers are photosynthetic. Producers are plants, some bacteria and algae. • Consumers – all other organisms. They capture their energy by consuming other organisms. Animals, most protists and bacteria, and fungi are all consumers. • Each ecosystem contains consumers called decomposers. Decomposers obtain energy by consuming organic wastes and dead bodies. These include fungi (mushrooms) and some species of bacteria. t • Energy flows from producers to consumers. • Every organism is assigned to a trophic level. All members of a trophic level are the same number of energy-transferring steps away from the sun. • Producers (plants) are the first trophic level. Plants and other organisms that make their own food are called autotrophs. • Plant eaters (herbivores) are in the second trophic level. This includes cows, caterpillars, elephants and ducks. • Animals that feed on the plant eaters are in the third trophic level. All organisms in the third trophic level or above are carnivores (flesh eaters). Carnivores at the third level feed on herbivores, and carnivores above the third trophic level feed on other carnivores. Tigers, hawks, weasels, pelicans and killer whales are all carnivores. • Omnivores (bears and humans) eat both plants and animals. • Because they cannot make their own food, organisms in trophic levels above the first trophic level are heterotrophs.