Topic 23/24 -Community Structure

Question 1

physical structure reflects abiotic and biotic characteristics, the range of environmental conditions or resources…

Answer 1

set a limit on the number of species and their relative abundance in a community

Question 2

the number of fundamental niche represents

Answer 2

the primary constraint on the biological structure of a community
general pattern: the more fundamental niches the higher the number of species

Question 3

Biological structure reflects the diversity of species in the community and their interactions with each other

defined by:

Answer 3

Species richness (S) =number of species 
Relative abundance of each species 
Species composition =the types of species that make up the community 

a larger number of species does not necessarily mean a higher diversity

Question 4

Evenness

Answer 4

equitable relative abundance of species in a community

Question 5

Dominance

Answer 5

inequitable relative abundance of species in a community

Question 6

where individuals vary in size -abundance alone may not be a sufficient indicator of dominance, define dominance based on

Answer 6

a combination of abundance and size (biomass of all living individuals)
high dominance means low diversity (high evenness =high diversity)

Question 7

Biodiversity

Answer 7

the biological structure of the community
from the reference point of ecological study (genetic diversity, species diversity)

can be measured by rank abundance plots

Question 8

Rank abundance plots

Answer 8

can see:
species richness
slope of the line(log scale) tells us about the evenness
straight horizontal line indicating high evenness
steep slope indicates lower evenness

Question 9

Many scientists argue that all communities have one typical pattern in abundance:

Answer 9

few abundant species, few rare species, most species of moderate abundance (“log normal”)
different curves reflect different sampling efforts

Question 10

A community is characterized by many direct and indirect interactions

Answer 10

difficult to study the interactions between two species in nature without considering their interactions with other species

Question 11

Interaction strength

Answer 11

number of direct connections of a species

Question 12

weak interactors

Answer 12

functionally not significant -low relative influence on biological structure

Question 13

strong interactors

Answer 13

functionally dominant -a species that influences the biological structure of a community more relative to other species

Question 14

foundation species

Answer 14

species that has a dominant number or mass of individuals relative to other species

Question 15

keystone species

Answer 15

species that influence the biological structure of a community disproportionately to their numerical abundance

Question 16

ecosystem engineers

Answer 16

species that create/ eliminate habitat (keystone species)

Question 17

foundation species are essentially the

Answer 17

habitat for the whole community (forests and reefs)

Question 18

keystone species may create the

Answer 18

habitat that other (often more abundant species) can exploit
ex beavers -many canadian forest communities by increasing habitat diversity due to dams
-formation of Ox-bows

Question 19

The nature of species interactions is an important descriptor of biological structure, describe species interactions by

Answer 19

feeding relationships

or how species interact in the process of acquiring food/energy to describe biological structure of communities

Question 20

Food chain

Answer 20

pathway of food/energy transfer between species

descriptive diagram of feeding relationships

Question 21

numerous food chains interconnect to form a

Answer 21

Food web

Question 22

trophic levels

Answer 22

groups of species that derive food energy from a similar source

Question 23

guilds

Answer 23

groups of species within each trophic level that exploit a common resource in a similar manner

Question 24

Basal species

Answer 24

feed on no other species but are fed upon by others

primary producers -plants

Question 25

intermediate species

Answer 25

feed on other species and are prey for other species
Primary consumers -herbivores
Secondary consumers -carnivores

Question 26

Top predators

Answer 26

feed on other species but are not prey for other species
omnivores -feed on more than one trophic level
cannibals -feed on itself

Question 27

If species interactions are altered ->cascading impacts throughout food webs ______and_____Trophic cascades

Answer 27

bottom up and top down

Question 28

phase shifts

Answer 28

transition in species relative abundance and community composition