Community Ecology

Community group of populations interacting with one another within the same environment. Example: fallen log with all species that live within it. Species diversity increases the closer you get to the equator. Composition of a community – list of species Diversity of a community – includes number of species and their abundance

Competition Interspecific competition – members of different species try to use a resource that is limited. May result in resource partitioning leading to niche specialization. Competitive exclusion principle – no two species can indefinitely occupy the same niche at the same time

Structure of the community Habitat – place where an organism lives and reproduces Ecological niche – role it plays in its community, including habitat and interactions with organisms Fundamental niche – all conditions under which the organism can potentially survive and reproduce Realized niche – set of conditions under which it exists in nature. Competition forces an organism to occupy its realized niche, which is smaller than fundamental

Predator-prey Predation – when a predator feeds on prey Prey defenses In nature, the presence of predators can decrease prey densities and vice versa Prey defenses Camouflage – ability to blend into a background Walking sticks, katydids Mimicry – when a species resembles another that possesses an antipredator defense Batesian – mimic that lacks the defense Mullerian – mimics that share the same protective defense

Cryptic coloration and aposematic coloration

Mullerian mimicry and Batesian mimicry

Symbiotic relationships 3 types: parasitism, commensalism and mutualism Parasitism: parasite derives nourishment from another, a host. Parasites can weaken or kill host, +, - Commensalism – between two species in which one species is benefited and the other is neither benefited nor harmed, +, 0 Mutualism – both members of association benefit, +,+ Mycorrhizae

Parasitism, Mutualism

Commensalism

Community Development Ecological succession – change involving a series of species replacements in a community following a disturbance. End result can not be predicted Pioneer species – first species to begin secondary succession

Ecological Succession

Community Biodiversity Intermediate disturbance hypothesis – moderate amounts of disturbances at moderate frequency are required for a high degree of community diversity. Ex. Fire Keystone species – organisms that play a great role in maintaining the function and diversity of an ecosystem than would be predicted by their abundance.

Keystone species