1. Community Interactions

2. Organisms not only live together in ecological communities, but they also constantly interact with one another. These interactions, which include predation and competition, help shape the ecosystem in which they live.
1. Based on your own experiences, define predation. Give one example of predation.
2. Based on your own experiences, define competition. Give one example of competition.

3. Living and Non-living Factors
Living things
ECOSYSTEM
Non-living things

4. Biotic and Abiotic Factors
Living things =
BIOTIC FACTORS
ECOSYSTEM
Non-living things =
ABIOTIC FACTORS

5. Biotic and Abiotic Factors
The living (biotic) and nonliving (abiotic) parts of an ecosystem are always interacting.
The biotic and abiotic factors of an ecosystem shape that ecosystem.

6. Community Interactions
Not only do the biotic and abiotic parts of an ecosystem always interact, the living things are always interacting with each other.
When organisms live together in an ecological community, they constantly interact.
A community is a collection of different populations that live together in a certain area.

7. Community interactions can powerfully affect an ecosystem.
Three main types of interactions between the living (biotic) things in an ecosystem:
Competition
Predation
Symbiosis

8. Competition
Competition occurs when organisms try to use the same resources in the same place at the same time.
A resource is any necessity of life, such as water, nutrients, light, food, or space.

9. Competition
In a forest, for example, trees with large leaves may compete for sunlight by growing tall, spreading out their leaves, and blocking the sunlight from shorter trees.
Direct competition in nature often results in a winner and a loser. The loser then fails to survive and dies.
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10. Competitive Exclusion Principle
Two species cannot occupy the same niche in the same habitat at the same time.
Habitat – the place where an organism lives that provides all of its needs
Niche – the job of a living thing in its community

11. Competitive Exclusion Principle
Figure 4-5 Three Species of Warblers and Their Niches
Competitive Exclusion Principle
Section 4-2
Cape May Warbler
Feeds at the tips of branches
near the top of the tree
Bay-Breasted Warbler
Feeds in the middle
part of the tree
Yellow-Rumped Warbler
Feeds in the lower part of the tree and
at the bases of the middle branches
Spruce tree
Each of these warblers has a different niche in its spruce tree habitat. By feeding in different areas of the tree, the birds avoid competing with one another for food.
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12. Predation
Predation is a community interaction in which one organism captures and feeds on another organism.
The predator is the organism that does the killing and eating
The prey is the food
necsi.org/.../ co-evolution_predator.html

13. Symbiosis
Symbiosis is a relationship between two species that live close together.
Three classes of symbiosis in nature
1. Mutualism
2. Commensalism
3. Parasitism

14. Mutualism In mutualism, the relationship benefits both species.

15. Commensalism
In commensalism, one organism benefits from the relationship and the other is neither helped nor harmed.

16. Parasitism
In parasitism, one organism lives on or inside another organism and harms it.