1. Community Interactions

2. What is a Community?
A group of several different species living together in the same area.

3. Types of Community Interactions
Anytime organisms live together, they have to interact with one another.
They can do this in several different ways:
Predation
Competition
Symbiosis

4. Predation An organism catches and eats another organism.
Predator = the one that eats the other
Prey = the one being eaten

5. Competition
This happens whenever more than one organism needs to use the same resource.
Usually for:
Food
Water
Shelter
Mating rights

6. Competition (Cont.)
Competition doesn’t always mean a physical confrontation.
Ex: If a cat drinks a bowl of milk before other cats arrive, it is still a form of competition.

7. Symbiosis
Any relationship in which two species live together (at least one species always benefits).
3 types
1. Mutualism
2. Commensalism
3. Parasitism

8. 1. Mutualism
Both species benefit.

9. 2. Commensalism
One species benefits; the other is not helped nor hurt.

10. 3. Parasitism One species benefits; the other is harmed.
Parasite = The one that benefits
Host = The one that is harmed

11. Parasites
Parasites get all or part of their nutritional needs from their hosts
Parasites typically weaken, but do not kill their hosts

12. Lecture Review Questions
Why is a balance of autotrophs, heterotrophs, and decomposers important for an ecosystem?
What is the major difference between the energy and biomass pyramids?
Why are community interactions important to understanding the way an ecosystem functions?