ch. 54 part 2

Question 1

dominant species

Answer 1

those that are most abundant or have the highest biomass

Question 2

how are invasive species usually introduced to a new environment

Answer 2

humans

Question 3

why do invasive species dominate

Answer 3

they lack natural predators or parasites

Question 4

keystone species

Answer 4

exert strong control on a community by their ecological roles, or niches

Question 5

are keystone or dominant species more abundant in the community

Answer 5

dominant

Question 6

ecosystem engineers (foundation species)

Answer 6

cause physical changes in the environment that affect community structure
- (like beavers and dams)

Question 7

bottom-up model of community organization

Answer 7

proposes unidirectional influence from lower to higher trophic levels
- present/absence of mineral nutrients (N) control plant (V) numbers, which control herbivore (H) numbers, which control predator (P) numbers

Question 8

top-down model (trophic cascade model)

Answer 8

proposes that control comes from the trophic level above
- predators limit herbivores, herbivores limit plants, and plants limit nutrient levels

Question 9

mesopredator release

Answer 9

populations of medium-sized predators rapidly increase in ecosystems after the removal of larger, top carnivores

Question 10

biomanipulation

Answer 10

deliberate alteration of an ecosystem by adding or removing species, especially predators

Question 11

what did most ecologists favor decades ago

Answer 11

view that communities are in a state of equilibrium

Question 12

F. E. Clements

Answer 12

argued that plant communities had only one state of equilibrium, a climax community, controlled by climate
- suggested that biotic interactions caused species in a climax community to function as a superorganism

Question 13

A. G. Tansley

Answer 13

argued that variation in abiotic conditions created many possible stable communities within a region

Question 14

H. A. Gleason

Answer 14

viewed communities as a change assemblages of species w/ similar abiotic requirements

Question 15

disturbance

Answer 15

event that changes a community, removes organisms from it, and alters resource availability

Question 16

nonequilibrium model

Answer 16

describes communities as constantly changing after disturbance

Question 17

how do types of disturbances vary

Answer 17

frequency and severity

Question 18

significant sources of disturbance

Answer 18

storms and fire

Question 19

high level of disturbance

Answer 19

result of frequent/intense disturbance
- exclude many slow-growing species

Question 20

low levels of disturbance

Answer 20

result from low frequency or low intensity of disturbance
- allow dominant species to exclude less competitive species

Question 21

intermediate disturbance hypothesis

Answer 21

moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance

Question 22

ecological succession

Answer 22

sequence of change sin community composition following a disturbance

Question 23

primary succession

Answer 23

occurs where no soil exists when succession begins

Question 24

how may early/later-arriving species be linked?

Answer 24

1. early arrivals my facilitate appearance of later species by making environment favorable
2. may inhibit establishment of later species
3. may have no affect on establishment of later species

Question 25

serial stages on moraines in Glacier Bay, Alaska

Answer 25

1. colonized by pioneering plants
2. Dryas stage
3. Alder stage
4. Spruce stage

Question 26

what is succession the result of

Answer 26

changes induced by vegetation itself

Question 27

what do pioneer plants facilitate

Answer 27

later arrivals by increasing soil nitrogen content

Question 28

secondary succession

Answer 28

begins in an area where soil remains after a disturbance

Question 29

2 biogeographic factors that affect species diversity of biological communities

Answer 29

1. latitude
2. area

Question 30

species richness across globe

Answer 30

• great in tropics
• declines in gradient toward the poles

Question 31

why may there be greater species richness in tropical environments

Answer 31

more time for speciation and migration to occur

Question 32

2 main climatic factors correlated with biodiversity in terrestrial communities

Answer 32

1. sunlight
2. precipitation

Question 33

evapotranspiration

Answer 33

evaporation of water from soil plus transpiration of water from plants

Question 34

what is potential evapotranspiration the measure of

Answer 34

potential water loss, assuming water is available

Question 35

are evapotranspiration and potential evapotranspiration higher in warm/wet conditions or dry/hot conditions

Answer 35

warm and wet conditions of tropics

Question 36

what does species richness correlate with

Answer 36

both evapotranspiration and potential evapotranspiration

Question 37

species-area curve

Answer 37

quantifies idea that, all other factors being equal, a larger geographic area has more species

Question 38

Robert MacArthur and E.O Wilson

Answer 38

developed method for predicting species diversity on islands called island equilibrium model

Question 39

island equilibrium model

Answer 39

• species richness on islands represents a balance between immigration of new species and extinction of established species

Question 40

what are immigration and extinction affected by

Answer 40

island size and distance from the mainland

Question 41

as the number of spices on an island increases…

Answer 41

• immigration decreases
• extinction increases

Question 42

smaller island

Answer 42

• number of species decreases
• immigration decreases
• extinction increases

Question 43

larger island

Answer 43

• number of species increases
• immigration increases
• extinction decreases

Question 44

islands closer to the mainland

Answer 44

• immigration increases
• extinction decreases

Question 45

islands further from the mainland

Answer 45

• immigration decreases
• extinction increases

Question 46

equilibriums

Answer 46

rate of immigration is equal to rate of extinction

Question 47

pathogens

Answer 47

disease-causing microorganisms, viruses, viroids, and prions
- can affect community structure
- can be virulent in new habitat