1. Community Interactions
Ecology Notes 4-2
Community Interactions

2. Biotic vs. Abiotic
Biotic factors – living factors in an environment. Ex. Trees, birds, bacteria, etc.
Abiotic factors – non living factors in an environment. Ex. Temp., rainfall, humidity, soil.

3. Niche
Niche – full range of conditions in which an organism lives (biotic and abiotic). It is like your “occupation”.

4. Competition
Competition – occurs when organisms attempt to use a resource (water, nutrients, light, food or space) at the same time.
We call this a +/- relationship.
Competitive Exclusion Principle – no two organisms can occupy exactly the same niche in the same habitat at the same time.

5. Predation One organism captures and feeds on another organism.
This is a +/- relationship.

6. Symbiosis – any relationship where two organisms live closely together.
3 types of Symbiosis
1. Mutualism +/+ both organisms benefit. Ex. Flowers/insects.

7. 2. Commensalism +/0 one organism benefits and the other is neither helped nor harmed. Ex. Whales/barnacles

8. 3. Parasitism +/- One organism lives on or in another organism. Ex
3. Parasitism +/- One organism lives on or in another organism. Ex. Dog/flea