4-4 population and community ecology

4-4 population and community ecology - POPULATION AND...

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POPULATION AND COMMUNITY ECOLOGY LIFE 55 55.1 What are ecological communities? - species that live and interact in an area constitute an ecological community 55.1.1 Communities are loose assemblages of species - communities are loose assemblages of species , each of which is individually distributed according to its unique interactions with the physical environment 55.1.2 The organisms in a community use diverse sources of energy -The organisms in a community can be divided into trophic levels based on the source of their energy . A trophic level consists of the organisms whose energy source has passed through the same number of steps to reach them. Plants and other photosynthetic organisms ( autotrophs ) get their energy directly from sunlight. Collectively, they constitute a trophic level called photosynthesizers , or primary producers . They produce the energy-rich organic molecules that nearly all other organisms consume. -In most ecological communities , all nonphotosynthetic organisms ( heterotrophs ) consume the energy- rich organic molecules produced by primary producers . Organisms that eat plants constitute a trophic level called herbivores or primary consumers . Organisms that eat herbivores are called secondary consumers . Those that eat secondary consumers are called tertiary consumers , and so on. Organisms that eat the dead bodies of organisms or their waste products are called detritivores or decomposers . Organisms that obtain their food from more than one trophic level are called omnivores -sequence of interactions of who eats what can be diagrammed as a food chain . Food chains are usually interconnected to make a food web because most species in a community eat and are eaten by more than one other species - Detritivores such as bacteria, fungi, worms, mites, and many insects, transform detritus (dead remains
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4-4 population and community ecology - POPULATION AND...

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