Community Ecology 2 - Predation and Community

Question 1

Species Diversity in a Community

Answer 1

1. Richness
2. Evenness

Question 2

Species Richness (S)

Answer 2

simply a count of the number of species in a community

Question 3

Species Evenness

Answer 3

the relative abundance of species in a community (how evenly individuals are distributed among species)

Question 4

Community Stability

Answer 4

• communities are not random assemblages of species
• they are non-random because of interspecific interactions

Question 5

Keystone Species

Answer 5

species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically
- serves as an unintentional force for stability of a complex set of community interactions
- usually neither the most numerous nor best competitor for resources in an ecosystem

Question 6

MacArthur + Wilson: Islands

Answer 6

1. more isolated island have lower immigration rates
2. larger islands have lower “extinction” rates (loss of the species to the island). One way that a species can remain on the island is to re-migrate, which is more likely to happen by change on larger islands

Question 7

Equilibrium Number - S-hat

Answer 7

the intersection of immigration and extinction rates for an island predict an equilibrium number of species, S-hat, assuming island size and distance from mainland

Question 8

Predation

Answer 8

fundamentally asymmetric relationship that benefits one participant and harms the other
- predation moves energy and materials through food webs
- some predators feed mainly on “surplus” population leaving healthy, reproductively active adults alone
- some predators feed so efficiently that they can control prey abundance or cause extinction

Question 9

Keystone Species (Lecture)

Answer 9

a species whose influence on a community is much greater than would be expected based on its abundance
- plants act as keystone species in many terrestrial ecosystems
- predators may act as keystone species by altering the outcome of competition among prey species
- microorganisms may be keystone species

Question 10

Island Biogeography Model

Answer 10

species richness on islands determined by the interaction between new colonization and extinction

Question 11

What does the intersection of immigration and extinction rates indicate on graphs of island biogeography?

Answer 11

the equilibrium number of species on an island

Question 12

Keystone Species (Lecture)

Answer 12

a SINGLE SPECIES that serves as the UNINTENTIONAL ANCHOR FOR STABILITY of a complex set of COMMUNITY INTERACTIONS
- is not always the strongest competitor

Question 13

Islands: Immigration Rate

Answer 13

number of species colonizing an island per unit time

Question 14

Islands: Extinction

Answer 14

loss of species from an island

Question 15

Rescue Effect

Answer 15

when islands are near another source (mainland or island), then constant arrival of species can “rescue” or replace it when it goes locally extinct, so near islands have lower extinction rates and therefore lower turnover
- distance affects extinction

Question 16

Target Effect

Answer 16

when islands are small, they present a smaller “target” for colonizing species, so smaller islands have lower immigration rates and therefore lower turnover
- area affects immigration