Lecture 24: Introduction to Community Ecology

Question 1

Define guilds

Answer 1

Species living in a similar way

Ex: zooplankton

Question 2

Define life form

Answer 2

Species that have a similar growth from

Ex: algae

Question 3

Define functional group

Answer 3

Species with similar ecological function or attribute

Ex: trees in a forest

Question 4

Define keystone species

Answer 4

• species that have a disproportionate impact on the community structure relative to the abundance of other species
• if removed, there is a dramatic change in structure

Question 5

What does a community structure include?

Answer 5

• relative abundance of species within the community
• number of species and diversity
• species composition

Question 6

Define community diversity

Answer 6

A combination of the total number of species there are as well as their relative abundance

Question 7

Define species richness

Answer 7

The number of species in a community

Question 8

Define species evenness

Answer 8

The relative population size of each species

Ex: an ecosystem dominated by one species will have low evenness

Question 9

Define species diversity

Answer 9

A measure of diversity that increases with species evenness and species richness

Question 10

Explain species abundance

Answer 10

A measure of how common or rare a species is. It can be measured by number of individuals, species cover, or species biomass

Question 11

Explain species dominance

Answer 11

• Communities that have a dominant species over others
• It can be measured by biomass, area occupied, and number of individuals
• Few species are dominant or rare

Question 12

What is the insurance hypothesis?

Answer 12

The more diverse a community is, the more stable it is.

Question 13

What are some variables that measure species diversity?

Answer 13

Gamma: overall diversity within a region

Alpha: diversity within a particular area within a region (subset of gamma)

Beta: a measure of diversity among location within a region

Question 14

Explain rank abundant curves

Answer 14

To assess evenness of a new graph, we plot relative abundance against their rank in abundance. It allows scientists to visually portray species dominance

• the flatter the curve is, the more even a community is

Question 15

What are the factors that increase/decrease biodiversity?

Answer 15

1. time: more uninterrupted time to evolve, more biodiversity
   2: global change: pollution, habitat destruction, landscape homogenization, invasive species
2. complexity: the more complex, the more biodiversity
   4: exploitation and limitation: predators, herbivores, and nutrient limitation

Question 16

How does a more complex structure increase biodiversity?

Answer 16

Heterogenous and has more niches and factors to influence organisms

Ex: a lake is complex because it has spatial and temporal variation

Question 17

Define species composition

Answer 17

The species that occur in a given community at a given time.

Even with the same richness, diversity, and evenness, 2 communities can 0% identical because they are comprised of different species

Question 18

How does species diversity influence ecological function?

Answer 18

1. Complementarity: an ecological service is at its greatest when all resources are being occupied in a community
2. Facilitation: species enhance the growth of others
3. Species selection/sampling effect: species differ when it comes to rate of delivery of ecological services