COMMUNITY ECOLOGY CH 54 Community: a group of populations of species interacting

I. Community Interactions Classified by whether they help, harm, or have no effect on species involved – Interspecific interactions involve different species – Intraspecific interactions involve one species

1. Interspecies competition (+/-): two different species compete for the same resource. This often results in one species succeeding over the other Results in competitive exclusion

2. Resource partitioning (0/0): when species coexist despite their competition for the same resources because they live in slightly different niches

3. predation (+/-) when one species negatively uses another species for food.

Evolutionary adaptations that allow predator to capture prey – acute sense of smell – speed – claws, fangs, stingers, poisons evolutionary adaptations of prey – defensive adaptations: chemicals to thwart predator – behavioral adaptations: herding/schooling, hiding, fleeing

– morphological adaptations: Camouflage or cryptic coloration allows an animal to blend into its surroundings

– Aposematic or warning colorations of an animal that warns predators that they should be avoided

– Mimicry: when two species resemble each other mullarian: animals with the same mechanism of defense share the same coloration batesian: one animal with no defenses resembles another animal with defenses

4. Symbiosis occurs when two species live in close contact Mutualism (+/+): both species benefit Commensalism (+/0): one species benefits Parasitism (+/-): one species benefits and the other is harmed

species diversity: the variety of different species on a community. Has 2 components: – species richness: the number of different species in the community – relative abundance: the amount of each species in the community II. Species Diversity and Community Structure

communities with high diversity are: – more productive and stable – more likely to recover from environmental stress – more resistant to invasive species

1. Dominant species most abundant species in the community ex: sugar maple is abundant species in northeast forests and provides shade and good quality soil

what might happen if the dominant species declined in number? How did it become a dominant species?

2. Invasive/introduced species Organisms that are introduced to a new community, usually by humans Why are they so successful?

3. Keystone species Affects community structure not by being abundant but by its role in the community Ex: sea otters

III. Ecological Succession and Community Disturbances A. Community Disturbances A change in a community due to the destruction of resources and death of organisms o Natural disturbances  Fire, hurricane, volcanos o Human disturbances  Clearing of land, sinking of ships Community disturbance could be positive or negative

B. Ecological Succession: Colonization of new species into the disturbed area Primary succession: – when a force like a volcano destroys everything in community even soil – moss and lichen grow on hardened lava and make soil – small plants like grasses start growing in soil from blown in seeds – shrubs and trees start to grow

Secondary succession – When a force like a tornado or an abandoned farm destroys everything but leaves soil intact – Grasses start to grow then shrubs and trees