Ch. 18 Community Ecology (Part 2)

Question 1

species diversity is affected by:

Answer 1

resources, habitat, diversity, keystone species, disturbances

Question 2

5 shapes of graphs for the correlation b/w richness (diversity) and productivity

Answer 2

U-shaped, Negative slope, None (no slope), Positive slope, hump-shaped

Question 3

the most commonly shaped curve for the relationship b/w diversity and productivity (among vertebrates and invertebrates in aquatic and terrestrial systems) is the…

Answer 3

hump-shaped curve

Question 4

added fertility causes…

Answer 4

decline in species richness of producers
- ex: added nitrogen (cultural eutrophication)

Question 5

as habitat fertility increases, species richness…

Answer 5

decreases

Question 6

for plant communities: increased fertility may cause…

Answer 6

dominant plants to cast more shade on competitively inferior plants

Question 7

communities w/ high diversity of habitats should have more…

Answer 7

potential niches and higher diversity of species

Question 8

intermediate disturbances hypothesis

Answer 8

the hypothesis that more species are present in a community that experiences occasional disturbances than a community w/ frequent or rare disturbance (less species)

Question 9

when disturbances are rare, populations grow until…

Answer 9

resources are scarce, and competitively superior species become dominant

Question 10

when disturbances are frequent, habitats typically…

Answer 10

support a small number of species that are adapted to disturbances

Question 11

when disturbances occur at an intermediate frequency…

Answer 11

both types of species can persist

Question 12

food chain

Answer 12

linear representation of how different species in a community feed on each other

Question 13

food web

Answer 13

a complex and realistic representation of how species feed on each other in a community.
- indicate consumption and mvmnt of energy and nutrients

Question 14

trophic levels

Answer 14

a level in a food chain or food web of an ecosystem
- Producers = autotrophs = convert light energy and CO2 into carbohydrates through photosynthesis
- Producers form the first trophic level of a food web

Question 15

producers are…

Answer 15

autotrophs (convert light energy and CO2 into carbohydrates through photosynthesis)
- form first trophic level of food web

Question 16

primary consumer

Answer 16

species that eats producers

Question 17

Secondary consumer

Answer 17

a species that eats primary consumers

Question 18

Tertiary consumer

Answer 18

a species that eats secondary consumers

Question 19

Omnivore

Answer 19

a species that feeds at several trophic levels

Question 20

Guild

Answer 20

within a given trophic level, a group of species that feeds on similar items
- ex: guilds of leaf eaters
- members of the group are not necessarily related

Question 21

Direct effect

Answer 21

an interaction b/w 2 species that does NOT involve other species
- direct effect of 1 species sets off a chain of events that affect other species in the community

Question 22

Indirect effect

Answer 22

an interaction between two species that involves one or more intermediate species
- can occur b/w communities

Question 23

exploitative competition

Answer 23

an indirect effect
- 2 competitors are interacting by feeding on a third species, which is a common resource

Question 24

Trophic cascade

Answer 24

indirect effects in a community that are initiated by a predator

Question 25

Trophic cascade

Answer 25

indirect effects in a community that are initiated by a predator

Question 26

Density-mediated indirect effect

Answer 26

an indirect effect caused by changes in the density of an intermediate species

Question 27

Trait-mediated indirect effect

Answer 27

an indirect effect caused by changes in the traits of an intermediate species
- commonly occur when a predator causes its prey to change its feeding behavior (which alters the amount of food consumed by the prey)

Question 28

Bottom-up control

Answer 28

when the abundances of trophic groups are determined by the amount of energy available from producers

Question 29

Top-down control

Answer 29

when the abundances of trophic groups are determined by the existence of predators at the top of the food web

Question 30

ecosystems Without Top Predators: trophic cascades are often initiated by…

Answer 30

humans persecuting and harvesting top carnivores
- wolves and big cats in terrestrial ecosystems
- sharks, tunas, game fish in aquatic ecosystems

Question 31

If food webs have three trophic levels, top-down control by predators would…

Answer 31

reduce the abundance of herbivores, leading to an increase in vegetation

Question 32

many communities are simultaneously controlled from the…

Answer 32

top down by predators and from the bottom-up by resources

Question 33

Community stability

Answer 33

the ability of a community to maintain a particular structure

Question 34

Community resistance

Answer 34

the amount a community changes when acted upon by a disturbance
- ex: addition or removal of a species

Question 35

Community resilience

Answer 35

the time it takes after a disturbance for a community to return to its original state.

Question 36

diversity may promote…

Answer 36

community stability

Question 37

Alternative stable state

Answer 37

when a community is disturbed so much that species composition and relative abundance change
- the new community structure is resistant to further change

Question 38

Switching to alternative stable states typically requires…

Answer 38

a large disturbance (e.g., removing a keystone species)

Question 39

what does Simpson’s diversity index measuring?

Answer 39

the probability of randomly pulling 2 individuals out of 2 communities (1 from each): how different are they going to be?

Question 40

what does Shannon’s diversity index measuring?

Answer 40

the probability of randomly pulling 2 individuals out of 2 communities (1 from each): how similar are they going to be?