Essay by chrissaJunior High, 9th grade April 2004

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Ecology= the study of interactions among organisms and their environment.

Biosphere= the portion of earth that supports life.

Abiotic factors= non-living parts of the environment

Biotic factors= living parts of the environment

Levels of Organization in Ecology:

1. organism (one thing)

2. population (many things of the same species)

3. communities (a mix of different species)

4. ecosystem (living things and the environment)

5. biosphere (contains all ecosystems)

habitat= place where an organism lives

niche= the role and position a species has in its environment

symbiosis= "living together"; a relationship between two organisms

1. commensalism= one organism benefits, the other is

neither benefitted or harmed.

2. mutualism= both organisms benefit

3. parasitism= one organism benefits, the other is harmed

*energy flow= 10% is passed on, 90% is wasted

autotrophs= producers; make food; plants

heterotrophs= consumers; cannot make their own food

Three types of heterotrophs

1. herbivores= only eat autotrophs (plants)

2. carnivores= eat other heterotrophs (meat)

3. omnivores= eat both autotrophs and heterotrophs

scavengers= eat dead stuff; vultures, buzzards

*decomposer= break down the complex compounds of dead and decaying plants and animals into things that can be absorbed and used by organisms.

food chain


**arrow shows direction of ENERGY FLOW**


trophic level= each step in a food chain