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Section 3

III Interactions within Communities

A. Obtaining energy

The energy that fuels most life on Earth comes from the Sun. Energy is stored in the chemical bonds that hold the atoms of these energy-rich molecules together.

1.Producers are organisms that use an outside energy source like the Sun to make energy-rich molecules.

2. Most producers contain chlorophyll, a chemical that is required for photosynthesis.

3.Consumers are organisms that cannot make their own energy-rich molecules.

4.Consumers obtain energy by eating other organisms.

5.Herbivores are the vegetarians

6.Carnivores are animals that eat other animals

7.Omnivores eat mostly plants and animals

8.Decomposers consume waste and dead organisms

9.Food chains are simple models of the feeding relationships in an ecosystem

B. Symbiotic Relationships

Any close relationship between species

1.Mutualism is a symbiotic relationship in which both species benefit

2.Example of mutualism is a lichen. They are made up of an alga that lives within the tissues of a fungus. The alga supplies energy to itself and the fungus. The fungus supplies protection.

3.Commensalism is a symbiotic relationship in which one organism benefits and the other is not affected

4.Example of commensalism is the sea anemones and clown fish

5.Parasitism is a symbiotic relationship in which one organism benefits but the other is harmed (roundworms in puppies)

C. Niches

1. A niche is an organism’s role in its environment-how it obtains food and shelter, finds a mate, cares for its young, and avoids danger.

2. Special adaptations that improve survival are often part of an organism’s niche.

3. An example would be milkweed plants contain a poison that prevents many insects from feeding on them. (protection)

4. Predator and Prey

a. Predators are consumers that capture and eat other consumers (Lion)

b.Prey is an organism that is captured by the predator. (gazelle)

5.Cooperation – individual organisms often cooperate in ways that improve survival. Examples they alert each other to danger, live in social groups and performs different jobs (bees, ants..)