Defn: the resources and environmental conditions that a population requires.
- Resources include food and shelter
- Environmental conditions include abiotic factors and biotic factors such as competitors and predators.
- A habitat is specific for a species. Good Douglas squirrel habitat is not the same as good flying squirrel habitat.
- A species presence in a community is due to its tolerance to abiotic factors and biological interactions.
- Defn: a specie's role in the community.
- Often means the species use of resources.
- Fundamental niche is the range of abiotic and biotic conditions where the organism could thrive.
- Realized niche is a smaller range forced by competition or predation.
Examples of specie interactions :
- Defn: interactions between populations of different species.
- Predation, herbivory, parasitism and disease - one species benefits at the cost of the other.
- Mutualism - both species benefit. Example: nitrogen fixing nodules on legume roots. Sometimes called symbiosis.
- Commensalism - One species benefits and the other suffers no harm or benefit.
Predator - Prey Interactions:
- Stable boom-crash cycle of prey and predator can develop.
Interaction among species drives coevolution.
- Predators develop strategies. Example: bats use ultrasound to capture moths.
Prey develop countermeasures.
Plants develop chemical and physical defenses against herbivores.
- Secondary compounds - distasteful chemicals.
- Enlisting aid. Example: acacia housing ants.
Animals develop chemical, physical and behavioral defense methods:
- Chemical: bombardier beetle
- Physical: camouflage:
- Physical: Batesian mimicry - tasty organism looks like a foul tasting organism.
- Physical: Mullerian mimicry - unpalatable species look alike.
- Behavioral: moths take evasive action when they hear bats approaching.
- Communities change over time.
- Succession is the 'repeatable' progression of communities that regrow on a site.
- Climax community probably doesn't exist.
- Species diversity decreases as towards the poles.
- Increased diversity increases ability to resist environmental change.
Factors creating structure in a community:
- vegetation and trophic structures.
- affects of keystone predators
- competitive exclusion
- resource partitioning as evidence of past competition.