Community Structure and Diversity

Question 1

Community

Answer 1

group of cooccurring, interacting species

Question 2

Species Richness

Answer 2

the number of different species in a community

Question 3

Species Evenness

Answer 3

relative abundances of species compared with one another

Question 4

What does the Shannon index do?

Answer 4

quantifies the diversity of a community

Question 5

What is the range of the Shannon Index?

Answer 5

0-4

Question 6

What is refraction analysis used for?

Answer 6

used to make species accumulation curves, helps determine when most of the species in a community have been observed

Question 7

What is the purpose of a Rank Abundance Curve?

Answer 7

give a snapshot of overall diversity in a community and can suggest what species interactions might be occurring within the community

Question 8

Direct Interactions

Answer 8

A directly interacts with B (i.e. species A eats species B, species A allows species B to grow more abundantly…etc)

Question 9

Indirect Interactions

Answer 9

A directly interacts with B which indirectly effects C (i.e. a plant (A) encourages plant (B) to grow. An insect (C) eats plant (B), so plant (A) has indirect interactions with the insect (C))

Question 10

interaction webs

Answer 10

non trophic interactions, i.e. commensalism, competition

Question 11

trophic webs

Answer 11

energy (trophic) interactions, i.e. food webs

Question 12

what are keystone species?

Answer 12

Species with low abundance or a small size, but a large impact (ex: starfish)

Question 13

How do you differentiate between a keystone species and a dominant species?

Answer 13

A dominant species in an ecosystem is the most abundant species present. It makes up the highest percentage of the total biomass in the system. A keystone species is one that has the greatest effect on all of the other species in an ecosystem.

Question 14

are top predators always keystone species?

Answer 14

No- if the prey isn’t abundant, the predator isn’t a keystone species

Question 15

What are ecosystem engineers?

What is their impact?

Answer 15

Any organism that creates, significantly modifies, maintains, or destroys a habitat. They can have a large impact on the species richness and the kinds of landscapes that are available to a community. (ex: beavers, worms, trees)

Question 16

what is ecosystem redundancy?

Answer 16

When the functional contribution of additional species reaches a threshold because as more species are added to the community, there is overlap in their function

Question 17

What is biogeography?

Answer 17

the study of patterns of species composition and diversity across geographic locations

Question 18

What is the Cradle Hypothesis?

Answer 18

everything originated from low latitude ecosystems then moved North and South when disturbances were low enough

Question 19

What is the typical pattern for species richness and latitude?

Answer 19

Low latitude = greater species richness

High latitude = less species richness

Question 20

What hypotheses explain the pattern of species richness and latitude? (3)

Answer 20

1. Species diversification rate is higher in the tropics
2. Diversification rates are similar, but evolutionary time is greater in the tropics
3. Higher productivity results in more abundant resources in the tropics

Question 21

What different interactions among species can affect species richness in communities?

Answer 21

Resource partitioning is theorized to reduce competition and increase species diversity.
Disturbance, stress, predation, and positive interactions can mediate resource availability, thus promoting species diversity

Question 22

What kinds of ‘filters’ determine which species are found in a community?

Answer 22

Regional species pool, dispersal ability, environmental conditions

Question 23

What does the Regional Species Pool limit?

Answer 23

Regional species pool provides an upper limit on the number and types of species that can be present in a community