1. Community Ecology

2. Differences within a Community
Community - an assemblage of species living close enough for the potential of interaction
Species richness - number of species within a community.
Relative abundance - the number of common species as compared to rare species.
Species diversity - species richness+relative abundance

3. Interspecific Interactions between Populations of Different Species
The adaptation of one species to the presence of another may lead to coevolution (a change in one species acts as a selective force on another).
Example
predator/prey
mutualism
commensalism

4. Predation/Parasitism
Predation - a predator eats a prey
Parasitism - parasites live in or on a host, usually killing them outright.
Parasitoidism - small insects such as wasps lay eggs on hosts; the larvae feed within the body of the host, killing it.
Herbivory - animals eat plants

5. Plant Defenses Against Herbivores
Thorns/hooks/spines in or on leaves and stems
chemicals that produce distasteful foliage such as strychnine, morphine, nicotine
production of analogous (same in appearance not function) hormones that causes abnormal insect development when eaten

6. Animal Defenses Against Predators
Hiding, fleeing, alarm calls, distraction displays, escaping, combat tactics.
Cryptic coloration - passive defense that makes potential prey difficult to see (camouflage)
Batesian mimicry - palatable prey resembles the appearance of a harmful or unpalatable species

7. Predation Parasitism - one organisms derives nourishment from another
Endoparasites - live within the host tissue or cavities (tapeworms)
Ectoparasites - attach or briefly feed on external surfaces ( mosquitoes)

8. Interspecific Competitions
Competitive Exclusion Principle - two similar species in the same area with similar resources can not coexist.

9. Ecological Niche What is your niche?
Ecological niche - how an organisms fits in to its environment by using biotic and abiotic resources
Two species can not coexist if they have identical niches.

10. Evidence for Competition
The weaker individual will become extinct.
One of the species will evolve to the point of using a different set of resources.
Resource partitioning

11. Commensalism
Symbiotic relationship where one organism benefits without significantly affecting another; unlike parasitism.
Cattle egrets
Difficult to find a true commensalistic relationship when most relationships will benefit both species to some degree.

12. Mutualism Symbiotic relationship where both organisms benefit.
Nitrogen fixing bacteria and legumes.

13. Community Structure - Food Webs
Secondary Consumers
Primary Consumers
Primary Producers

14. Disturbance and Nonequilibrium
Disturbance - anything that disrupts a community
change in resource availability allowing for disappearance or emergence of new species
natural disasters
human intervention
clear cutting
logging
pollution
grassland destruction

15. Succession Succession - transition of species composition over time
Primary succession - succession of barren areas due to lack of soil formation, rubble, or barren rock (colonization of new lands)
pioneering species - species that will first colonize areas in primary succession (mosses, algae)

16. Succession (con’t)
Secondary succession - occurs when an existing community has been cleared by some disturbance that leaves the soil intact which will be recolonized by a fugitive species (weeds).