predation & comp effects

ecology

guild

grp of species that exploit a common resource base in a similar function

apex predator

highest trophic level, no other predators in food chain

keystone species

their activities determine community structure, have low biomass

• can reverse outcome of competition interactions

• common in aquatic env

• ex. starfish pisaster, sea otters in north pacific, af elephants

dominant species

control over occurance of other species

comp exclusion

dominance in plant comm changed by addition of butrients

theories of community organization

classical comp theory

comp-predation

comp-spatial patching

classical comp theory

• comp major biological process controlling community structure

• predicts n limiting resources are required for co-existence of n species

• n species competing for k limiting resources can stably coexist

comp-predation theory

• adds predation

• new equilibrium model that allows n species to coexist on fewer than n resources

comp-spatial patching theory

• env sub divided into patches

• diff species favored in diff patches

• allow multiple species to coexist on single resource

trophic levels

• green plants- producers

• herbivores- primary consumers

• carnivores, insects- secondary consumers

• higher carnivores- tertiary consumers

most common food chain length

5

longer chain> slower recovery from catastrophes

energetic hyp vs dynamic stability hyp

• length of food chain limited by inefficiency of engy transfer along food chain

• longer food chains not stable, fluctuations at lower levels are magnified at higher levels causing predators to go extinct

guilds and functional roles

• functional roles- decomposers, producers

• clarifies concept of niches

• allow to compare communities by concentrating on specific groups

• represent basic building blocks of communities

stable isotope for food chain analysis

changes in isotopic ratio of N2 in aquatic orgs in relation to their trophic status

community stability

• comm conservation: an eq comm will show no tendency to lose species over time

• comm recovery: eq comm can recover from events that drive of its constituent species to low density

• comm composition: eq comm can be built up by immigration of species from outside system

• independence of history: past events have no effect on community structure

restoration ecology

relationship betw spatial scale of natural & artificial disaster & approx expected time to recovery