Community Ecology Flashcards
What is a resource?
A thing/factor that causes population growth and is reduced by its use
Is oxygen a resource for humans? Why or why not?
No; the available amount of oxygen is not reduced by human use
When can oxygen be considered a resource for humans?
If they’re underwater or in outer space
Limiting resources are. . .
resources that are reduced the most by use and thus limit population growth
What is a niche?
The full range of resources that a species can use combined with range of conditions a species can tolerate
What are the two types of niches?
1) Fundamental niche
2) Realized niche
A fundamental niche is _______________
the full resource axis that species are theoretically able to use
A realized niche is _______________
the part of the fundamental niche that is actually used
What type of competition occurs when niches overlap?
Strong competition
What can happen when niches overlap?
Species may use realized niche smaller than fundamental niche
Communities inhabiting many similar species can lead to. . .
resource partitioning
Resource partitioning occurs when _______________
realized niches pack together for several similar species
How does resource partitioning help species avoid competition?
By dividing the resources
What happens to specific traits when there is strong competition or selection pressure?
The traits being used to collect resources can adapt over generations to distinctly new character state called character displacement
What is character displacement?
The shift in trait value; evolutionary adaptation in heritable trait
Character displacement is caused by. . .
resource partitioning
If a trait lacks enough heritable variation for character displacement to occur, it can lead to. . .
competitive exclusion
What is competitive exclusion?
The idea that more successful species will out-compete other species to the point of extinction (from the habitat)
The three main types of interactions are _______________
1) win-win
2) win-lose
3) lose-lose
What is a lose-lose interaction?
Interspecific competition: occurs when competition for resources drive reductions in niche overlap
Why do individuals of each species have more success in the absence of the other species when in competition?
Species require less energy to gain more resource access which leads to greater growth, survival, and reproduction
A competitive interaction results in positive/negative effects on one/both/neither species
negative; both
What are the three types of win-lose interactions?
1) predation
2) parasitism
3) herbivory
What type of effects come about as a result of win-lose interactions?
Negative effects on one species while benefitting the other
Predation is _______________
one species consumption of another
Parasitism is _______________
one species inhabitation of another species that is eventually harmed over time
Herbivory is _______________
a grazers consumption of a plant
How can herbivory be beneficial?
Grazer can promote the growth of new material by consuming excess or dead plants
Mutualism is _______________
when both species benefit from the interaction
How is the interaction between plant and root-inhabiting fungi mutualistic?
Fungi gains access to sugars like glucose and sucrose; plant gains access to phosphorous and nitrogen that fungi “recovers” from decaying organic matter
What is mutualism vulnerable to?
Cheating
Cheating is _______________
when one species steals the benefits of mutualism without providing anything in return
A bee that bites open a flower stem to gain nectar is cheating the interaction because _______________
it is not actually pollenating the flower
Are interspecific interactions static or dynamic? Why?
Dynamic because they can shift from one type of interaction to another
What happens in a community when two species directly compete for a limited resource?
A) Coexistence
B) The superior competitor wins
C) The inferior competitor wins
D) Both species die off
B) The superior competitor wins
How might a mutualistic relationship between species evolve into a parasitic one?
When one of the species stops receiving a benefit and also begins to incur a cost
The barnacle Chthamalus stellatus is capable of growing at depths much lower than those at which it is actually found in nature. Experimental studies have determined that the lower limit of Chthamalus is determined by another barnacle, Balanus balanoides. The rapidly growing Balanus is able to smother, crush, or undercut the slower-growing Chthamalus. Because of this, Chthamalus cannot survive in the lower depths where Balanus is found. The interaction between these two barnacles is an example of
A) predator–prey interaction.
B) mutualism.
C) commensalism.
D) amensalism.
E) competition.
E) competition.
Commensalism is _______________
the interaction between two species when one is always benefitted and the other is neither harmed nor benefited (neutral)
Amensalism is _______________
the interaction between two species when one is always harmed and the other is neither harmed nor benefitted (neutral)
G. F. Gause claimed it is not possible for species with the same niche to coexist. If the niches of two species are similar but do not completely overlap, the species can coexist _____.
A) if one of the two species reduces its fundamental niche
B) if each of the species lives in its fundamental niche
C) if each species lives in its realized niche, which is the portion of resources or areas used or conditions tolerated when competition occurs
D) The species will not be able to coexist because one of the species inevitably will be a better competitor
C) if each species lives in its realized niche, which is the portion of resources or areas used or conditions tolerated when competition occurs
Strong predation on a species of prey can ______ the prey population which also _______ the predator population. Why is that?
Reduce; reduce.
Predation causes a reduction in prey population because they are killing them in order to gain energy and nutrients to survive. As a result, the predator population diminishes when there are not enough prey/resources to provide for every single predator.
What can strong predation result in?
Continual co-evolution of traits that increase fitness
Which population is greater: prey or predator? Why?
The prey population is always greater than the predator population because of the energy inefficiency as the food chain goes up
What are the two metrics of species diversity in a community assemblage?
1) species richness
2) species evenness
What is species richness (S)?
The number of species in a community
What is species evenness (H’)?
A skew in how common versus rare different species are
If a community has a large H’, there is _______ evenness and thus _______ diversity
more; more
Which statement about predators is false?
A) Many predators have broad diets.
B) Some predators can switch their foraging to whichever prey is most plentiful.
C) All predators move about in search of prey.
D) All of the above are true; none is false.
C) All predators move about in search of prey.
Two communities that contain the same number of species have the same species diversity if
A) The species are represented in different proportions in each community.
B) the population sizes of each species are different in each community.
C) Different species are rare versus common in each community.
D) Species in one community are represented in similar proportions but at twice the population size as in the other.
E) All of these.
D) Species in one community are represented in similar proportions but at twice the population size as in the other.
How is community stability disproportionally controlled?
By keystone species and dominant predators
What are keystone species?
Species that other species largely depend on and that would disrupt the ecosystem balance if it were removed
True or false?
Keystone species are the most numerous species and best competitor for resources in the ecosystem.
False; Keystone species are NEITHER the most numerous species NOR best competitor for resources in the ecosystem.
What are dominant competitors?
Species with high population size that outcompete other species for resources
Keystone predators can maintain species diversity in a community if they
A) competitively exclude other predators.
B) reduce the number of disruptions in the community.
C) prey on the community’s dominant species.
D) allow immigration of other predators.
E) prey only on the least abundant species in the community.
C) prey on the community’s dominant species.
What is theory of island biography?
MacArthur and Wilson’s theory (1963) that explained why ecologists could predict species richness (population size) but not predict the composition of species
What relationship did MacArthur and Wilson observed?
A positive log-linear relationship between habitat area size (x-axis) and number of similar species (y-axis)
The two assumptions of the theory of island biography are __________
1) more isolated islands have lower immigration rates (distance from the mainland to the island)
2) larger islands have lower extinction rates (loss of species from the island)
Species can remain on an island or avoid extinction by __________
re-migration
The equilibrium of a number of species in a community can be predicted by __________ on the graph of the number of species (x-axis) and rate (y-axis)
the intersection of immigration rate (negative linear slope) and extinction rate (positive linear slope)
What are the outcomes of the theory of island biography?
1) the number of species on an island should eventually become roughly constant and go to equilibrium
2) the number of species on an island is determined by the dynamic balance between immigration and extinction
3) islands have a continual turnover of species with some becoming extinct (from the island) and others immigrating (dynamic, not static)
If an island’s distance from the mainland increased, then Island Biogeography theory predicts that the number of species immigrating would ________ and that the number of species lost from the island would __________.
A) decrease; stay the same or increase
B) both decrease
C) increase; decrease
D) both stay the same
E) none of the above
A) decrease; stay the same or increase
What does the intersection of immigration and extinction rates indicate on graphs of island biogeography?
A) death rates
B) birth rates
C) how many species can live there
D) how many species are living there
C) how many species can live there
If predation increases over time, what immediate direct changes do you expect in b and d?
A) decrease in b, no change in d
B) decrease in b, increase in d
C) no change in b, no change in d
D) no change in b, increase in d
E) no change in b, decrease in d
D) no change in b, increase in d
According to the Shannon Diversity Index, a species composition ratio of 7:1:1 is ____________ a ratio of 3:3:3.
A) more diverse than
B) less diverse than
C) equally as diverse as
D) higher in evenness than
E) None of these.
B) less diverse than
Sea otters are not the most common species in nearshore waters of the West Coast of North America, but their presence or absence has a profound impact on community structure. Which of the following statements about nearshore ecosystems and the role that sea otters play in determining their structure is/are correct?
A) Kelp forests support a very diverse community of fish and invertebrates that aren’t found outside the kelp beds.
B) Otters feed voraciously on sea urchins, which in turn feed on benthic algae, including young kelp.
C) Kelp beds flourish only when otters can keep urchin populations under control.
D) All of the above.
E) None of the above
D) All of the above.
How would the species richness curves on an island be affected if mainland habitats were wiped out by urbanization?
A) It would increase the rate of immigration and increase the rate of extinction.
B) It would lower the rate of immigration and lower the rate of extinction.
C) It would lower the rate of immigration and increase the rate of extinction.
D) It would increase the rate of immigration and lower the rate of extinction.
E) It would have no effect.
C) It would lower the rate of immigration and increase the rate of extinction.
There are more terrestrial species in tropical areas than in places more distant from the equator. This is probably a result of _____ in the tropics.
A) more intense annual solar radiation
B) fewer predators
C) more frequent ecological disturbances
D) fewer agents of disease
E) greater human impact
A) more intense annual solar radiation
What happens when predators feed mainly on “surplus” or dominant species population (relative to size)?
They leave healthy, reproductively active adults alone.
Some predators feed so abundantly that they can control ______________ and even drive prey to ___________
prey abundance; extinction (from the community)
