Community Ecology

1. Community Ecology

2. Species Interactions • Communities are interacting populations of many species. • There are five types of close interactions (symbioses) that help to determine the nature of communities: • Predation • Parasitism • Competition • Mutualism • Commensalism

3. Predation • The predator captures, kills, and consumes the prey. • Influences where and how species live by determining relationships in the food web (more to come!) • Effective regulator of population size • Natural Selection • For the Predator: favors adaptations that improve the efficiency of finding, capturing, and consuming prey • Examples? • For the Prey: Favored adaptations for the prey to avoid, escape, or otherwise ward off predators. • Examples?

4. Mimicry as an Anti-predator Defense • Type I (Batesian): A harmless species resembles a poisonous or distasteful species. • Type II (Mullerian): Two or more dangerous or distasteful species look similar.

5. Other Types of Defensive Coloration • Cryptic coloration: An organism blends into it’s surroundings and is less likely to be found by the predator. • Aposematic coloration: Poisonous organisms have bright coloration- predators seem to be cautious when dealing with brightly colored organisms.

6. Plant-Herbivore Interactions • Plants have evolved adaptations to prevent them from being eaten: • Examples: • Spines • Thorns • Sticky Hairs • Chemical defenses • Secondary Compounds: Products of metabolism that are poisonous, irritating, or bad tasting • Poison Ivy and Oak • Nicotine

7. Parasitism • The parasite feeds on another individual, called the host. Does not result in the immediate death of the host. • Examples? • Two General Groups: • Ectoparasites: External parasites • Endoparasites: Internal parasites

8. Evolution of the Parasite and the Host • Parasites have a negative impact on the health of the host. • Parasitism has stimulated the evolution of a variety of defenses: • Examples? • Skin- prevents entry • Chemicals on surfaces where they could enter • Immune system attack!

9. Adaptations of Parasites • Natural selection favors adaptations that allow a parasite to efficiently feed off it’s host. • Usually specialized in both anatomy and physiology

10. Competition • Results from a fundamental niche overlap: the use of the same limited resources by two or more species. • Principal of Competitive Exclusion: describes situations in which one species is eliminated from a community because of competition for the same limited resource • One species uses the resources more efficiently and has a reproductive advantage that eventually eliminated the other species.

12. Competition and Community Structure • Composition of communities change due to competitive exclusion. Natural selection favors differences between potential competitors. • Character Displacement: Evolution of anatomical differences that reduce competition between similar species. • Resources Partitioning: When similar species coexist, each species uses only part of the available resources.

13. Character Displacement

14. Resource Partitioning

15. Mutualism and Commensalism • Mutualism: A cooperative relationship in which both species derive some benefit. • Commensalism: One species benefits and the other is not affected. • May be mutualisms in which the benefit to the second organism has not yet been identified.

16. Questions • Explain how predators differ from parasites. Give an example of each kind of organism. • Some harmless flies resemble bees and wasps. What is this mechanism called? Evaluate its importance as a defense mechanism. • Describe two chemical defenses of plants. • Explain the advantage of character displacement and give an example. • Explain how two similar species of birds are able to inhabit the same area and even nest in the same tree without occupying the same niche,