22. Ecological Communities

Question 1

community

Answer 1

an association of potentially interacting species inhabiting some defined area, at some particular scale, over some particular span of time

Question 2

community structure

Answer 2

attributes of a community, such as number of species, and distribution of individuals among species in the community

Question 3

species diversity

Answer 3

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

Question 4

species evenness

Answer 4

the relative abundance of species in a community

Question 5

species richness (s)

Answer 5

the number of species in a community

Question 6

3 types of species diversity

Answer 6

• gamma
• alpha
• beta

Question 7

rank abundance curves

Answer 7

plot of relative abundance of species against their rank in abundance - another way to assess dominance and diversity in community

Question 8

gamma diversity

Answer 8

diversity within a region or landscape

Question 9

alpha diversity

Answer 9

diversity within a locality within a region or landscape

Question 10

beta diversity

Answer 10

the difference between the diversity of a region or landscape, and a locality within the region or landscape

Question 11

guilds

Answer 11

groups of similarly functioning organisms (ex: filter feeders, hunters, and coronal ciliate feeders)

Question 12

species dominance

Answer 12

• More often than not, communities include a “dominant” species, one that is more common than all others.
• Most species in the community will occur in moderate abundances.
• Few species will dominant or rare
• more samples = more accurate

Question 13

measuring species richness and evenness

Answer 13

Shannon-Wiener diversity index (H’)

Question 14

measuring just species evenness

Answer 14

Pielou’s J

• closer to 1 = more even
• closer to 0 = less even

Question 15

Relationship between environmental complexity and species diversity

Answer 15

the more complex or heterogeneous the environment, the greater species diversity

Question 16

complexity

Answer 16

– Vertical structure (trees? no trees?)
– Water movement (current? no current?)
– Nutrient availability
– Light availability
a nearly infinite list

Question 17

simple homogeneous community

Answer 17

• Few factors that influenceorganisms

* Few niches

Question 18

complex heterogeneous community

Answer 18

• Many factors that influence organisms
• Many niches
(lakes are complex)

Question 19

species composition

Answer 19

the species that occur in a given community at a given time - shifts in species composition to non-native species often lead to changes (usually decreases) in species richness and evenness