Community Ecology Study Guide

Bio112

Define a community

A group of interacting populations

What are the four properties that community ecologists study?

1 Diversity

2 Species domination

3 Disturbances

4 Trophic structure

What are the two components that comprise diversity – explain what they are and why they are both important to the calculation of diversity.

Richness: Number of different species present in the community, and Eveness: A measure of how evenly the different species are represented within the community

How can species dominance affect community diversity?

Species that dominate a community out-compete other organisms present for resources

How can disturbance affect community diversity?

It can reduce the abundance of competitively dominant species

What is the intermediate disturbance hypothesis.

Levels on intermediate disturbance diversity will be at its highest, at high and low levels of disturbance diversity will be low

Define succession.

The sequential change in the composition of a community over time

What does trophic structure refer to?

Who eats whom in the community

Generally, what is a biotic factor?

Living things that can affect community structure

List the three major biotic factors that can affect communities.

1 Competition

2 Predation

3 Symbiotic relationships

List and define the two kinds of competition.

Intraspecific: competition between individuals of the same species (population), Interspecific: Competition between individuals of different species (community)

Explain the competitive exclusion hypothesis.

When two species use the same resource, one species is a better competitor and this species will exclude the less competitive species

Explain niche partitioning

The breakup of a niche/habitat into smaller pieces, each part used by a different species

How can predation lead to co-evolution

One species drives evolutionary change in another. Slow/weaker prey gets caught more easily, naturally leaving individuals who can get away more quickly.

What is mimicry and why do some organisms use mimicry?

Tricking predators into thinking it is poisonous. Use it to increase chances of survival.

Describe what a keystone predator is and how they may affect communities and diversity.

Predators that exert a strong control on community structure through predation. They prey on the competitively dominant organisms in the community, allowing other species to inhabit the habitat alongside them.

How can symbiotic relationships affect community structure?

They can cause declines or increases in the number of species in the community depending on how symbiosis affects the organism

Mutualism

Both organisms benefit from this interaction

Comensalism

One organism benefits while the host is unaffected

Paratism

The parasite gains while the host is negatively affected