1. Objectives 4.2 Niches and Community Interactions
-Define niche.
-Describe the role competition plays in shaping communities.
-Describe the role predation and herbivory play in shaping communities.
-Identify the three types of symbiotic relationships in nature.

2. Habitat or Niche???
Habitat ~ the place where an organism lives.
Niche ~ describes not only where it lives, but how it interacts with biotic and abiotic factors in the environment.

3. Resources
A resource is anything necessary for life, such as water, nutrients, light, food, mates or space.

4. Competition
Competition occurs when two or more organisms attempt to use the same limited resource in the same place at the same time.

5. The Competitive Exclusion Principle
The competitive exclusion principle states that no two species can occupy exactly the same niche in exactly the same habitat at exactly the same time.

6. Dividing Resources
Instead of competing for similar resources, species usually divide them.

7. Predator-Prey Relationships
An interaction in which one animal (the predator) captures and feeds on another animal (the prey) is called predation.
Predators can in affect the size of prey populations a community and determine the places prey can live and feed.

8. Keystone Species???
Sometimes changes in the population of a single species, often called a keystone species, can cause dramatic changes in the structure of a community.

9. Symbioses
Any relationship in which two species live closely together is called symbiosis, which means “living together.”
The three main classes of symbiotic relationships in nature are mutualism, parasitism, and commensalism.

10. Mutualism
When both species involved benefit from the relationship, it is called mutualism.

11. Parasitism
When one species benefits and the other one is harmed, the relationship is called parasitism.

12. Commensalism
When one organism benefits and the other one is neither helped nor harmed, the relationship is called commensalism.

13. True or False
An organism’s niche includes the way the organism gets what it needs to survive and reproduce. _________________________
Two kinds of birds eat the same food and nest in the same area. These two species of birds are in symbiosis. _________________________
If too many herbivores live in a community, the predator population will decrease rapidly. _________________________
A symbiotic relationship between organisms in which one species benefits and the other is neither helped nor harmed is mutualism. ______________________________

14. Answers
An organism’s niche includes the way the organism gets what it needs to survive and reproduce. True
Two kinds of birds eat the same food and nest in the same area. These two species of birds are in symbiosis. False, competition
If too many herbivores live in a community, the predator population will decrease rapidly. False, producer
A symbiotic relationship between organisms in which one species benefits and the other is neither helped nor harmed is mutualism. False, commensalism