1. What Shapes an Ecosystem?
Chapter 4.2
What Shapes an Ecosystem?

2. Biotic and Abiotic Factors
Biotic factors – are living organisms that another organism might interact with.
For example: to a cat biotic factors would be people, dogs, other cats, birds, insects
Abiotic factors – are nonliving factors that affect an ecosystem.
Examples: temperature, precipitation, wind, soil, sunlight.
Biotic and abiotic factors determine the survival and growth of an organism and the productivity of an ecosystem.
Habitat – the area where an organism lives.

3. The Niche
Niche – the full range of physical and biological conditions that an organism lives and the way the organism uses those conditions.
Part of an organisms niche is the food web it is involved in and range of temperatures that it needs.
No two species live in the same niche, similar but not the same.

4. Community Interactions
Community interactions, like competition, predation, and symbiosis can affect an ecosystem.

5. Competition
This occurs when organisms need the same resource at the same place and time.
Resource – any necessity of life, like water, nutrients, light, food, or space.
Direct competition usually has a winner (gets the resources) and a loser (dies).
Competitive exclusion principle – no two species can occupy the same niche in the same habitat at the same time.

6. Predation
Predation – when one organism captures and feeds on another organism.
Predator – the organism that does the killing and eating
Prey – the organism that gets eaten

7. Symbiosis Symbiosis – when two species live close together.
There are 3 types of symbiotic relationships: mutualism, commensalism, and parasitism.

8. Mutualism Mutualism – both species benefit from the relationship.
Example: flowers and pollinators

9. Commensalism
Commensalism – one member of the association benefits and the other is neither helped nor harmed.
Example: barnacles on a whale’s skin. The barnacles filter feed and the whale provides a current for it to feed. The whale is not affected in any way by the barnacle.

10. Parasitism
Parasitism – one organism lives on or inside another organism and harms it.
Example: tapeworms – live in the intestines of mammals and take nutrients from its host.

11. Ecological Succession
Ecosystems are always changing because of natural or human disturbances. As an ecosystem changes, older inhabitants die out and new ones move in, further changing the community.
Ecological succession are changes that are predictable and take place in a community.

12. Primary Succession Primary succession – on land where no soil exists.
This would be in places like after a volcano erupts, or on bare rock, sometimes after forest fires.
The first species to populate this area would be a pioneer species. For example a lichen (fungus and algae) is a pioneer species. They help form soil.

13. Secondary Succession
Secondary succession restores an ecosystem from a disaster like fire or farming.

14. Succession in Marine Ecosystems
When a large whale dies succession begins. It will sink to the ocean floor. There it is consumed by scavengers and decomposers. After the whale’s tissues are eaten, the decomposition gives the sea floor nutrients and provides a place for marine worms to live. When the whale’s skeleton remains heterotrophic bacteria will decompose oil in the bones and release chemical compounds into the water that chemosynthetic autotrophs use.