Download UWL BIO 307 Exam 3 Review: Competition and Coexistence in Ecology and more Exams Microbiology in PDF only on Docsity!
UWL BIO 307 EXAM 3 REVIEW QUESTIONS AND ANSWERS 2024/
What is the difference between intraspecific competition and interspecific competition? - ANS-✔✔ Interspecific: Diff species fighting for resources etc. eg: venus fly trap. carnivorous plants formed in low nutrient environments. Competition can restrict species to certain conditions.
Intraspecific: between individuals of the same species.
What is interference competition? - ANS-✔✔Competition that involves limiting access to space, making areas unusable (allelopathy)
Involves direct interaction between competitors such that the actions of one species inhibits the actions of another. Eg: allelopathy toxin production in competing plants
Restricts a species from reaching its full realized niche
What is resource (exploitation) competition? - ANS-✔✔Indirect inhibitory effects.
Eg: those arising from reduced availability of a resource
What do α and β represent in the Lotka-Volterra equations? - ANS-✔✔They represent the competition coefficients, aka scaling/conversion factors
What does it mean when α is greater than 1? - ANS-✔✔the competitive effect of an individual of species 2 on the population growth rate of species 1 is greater than that of an individual of species 1
If a > 1, competitive effect of an individual of species 2 on the pop growth rate of species 1 is greater than that of an individual of species 1. Slide 32 analogy ..?
What do the L-V zero growth curves for species 1 and 2 represent and how are they determined? - ANS- ✔✔populations to the left of the diagonal increase towards equilibrium by adding N1 + N
pop. to the right will decrease until they reach the diagonal
What happens to the population of species 1 inside of the zero growth curve? Outside of the curve? - ANS-✔✔populations to the left of the diagonal increase towards equilibrium by adding N1 + N
pop. to the right will decrease until they reach the diagonal
What happens to the population of species 2 below the zero growth curve? Above the curve? - ANS-✔ ✔populations to the left of the diagonal increase towards equilibrium by adding N1 + N
pop. to the right will decrease until they reach the diagonal
How are the joint population trajectories of species 1 and 2 determined when both graphs are superimposed? - ANS-✔✔vector addition
diagonals must cross for there to be an equilibrium (can be stable or unstable)
Given a Lotka-Volterra graph showing the zero growth curves for two species, be able to determine the outcome of competition between the species. - ANS-✔✔**** me bro idk
Provide a biological interpretation of each of the four possible outcomes of the L-V graphs. - ANS-✔✔1) Species 1 might always win
Species 2 might always win
Outcome might be determined by initial numbers
Both species might coexist in a stable equilibrium over time
What was the outcome of Gause's competition experiment with protozoans? - ANS-✔✔the first prey species went extinct, leading to the predators starving and also going extinct
there was one relationship where the species reached a point of coexistence but both had a low carrying capacity
What type of competition was shown by the experiment? - ANS-✔✔Interference competition
Why was Chthamalus restricted to a realized niche higher up the shoreline? - ANS-✔✔Chthamalus has a fundamental niche reaching up farther than its competing species
How does niche differentiation promote coexistence between two species? - ANS-✔✔Allows two species with a similar or same fundamental niche to live within that fundamental niche together and not have one outcompete another fully.
- ANS-✔✔Can produce or prevent interspecies competition by concentrating competitive effects more within species rather than between them
What is resource partitioning? - ANS-✔✔Eg birds feeding in different parts of the tree. Occupying different specific areas of a niche in order to avoid competition. Can be temporal or physical. 93
Species use a limited resource in different ways 109.
Provide an example of coexistence due to resource cyanobacteria partitioning in nature. - ANS-✔✔if predators force competing species into spatially segregated portions of the available habitat by their activities. This may lead to resource partitioning.
EG daphnia
How did the study by Stomp et al. (2004) demonstrate resource partitioning in two species of cyanobacteria in the Baltic Sea? - ANS-✔✔
How might temporal separation promote coexistence in nature? Provide an example of temporal separation that might promote coexistence among potentially competing species. - ANS-✔✔eg birds and bats feeding on insects at different times of the day
How might environmental variability promote coexistence among competing species? - ANS-✔✔ differences in both time and space can cause better coexistence among species
What is Hutchinson's "Paradox of the Plankton" and how did he suggest a solution to the paradox? - ANS-✔✔The fact that many plankton species coexist in habitats that seem to offer little opportunity for niche differentiation
How might the formation of unpredictable gaps promote coexistence between two species? - ANS-✔✔ eg fire, waves, landslides
fugitive species (r selected) and highly competitive K selected species can coexist
What are "fugitive species"? - ANS-✔✔an r-selected, colonizing species
How might a predator promote coexistence between two potentially competing species? - ANS-✔✔if predators hold both populations below their carrying capacities, then neither species might reach a level at which it can threaten the other
Brooks and Dodson's work with Daphnia:
(1) How did a predatory fish promote coexistence between the two species? - ANS-✔✔the fish can only see larger prey, so the smallest ones do not face predation from it (slide thru gills)
(2) What did they find in lakes that did not have the predatory fish? Why? - ANS-✔✔only larger daphnia
Give three ways in which observed niche differences in the field might have arisen. - ANS-✔✔
Explain how Tilman's Resource-Ratio Hypothesis might explain coexistence among competing species. - ANS-✔✔the ratios iof those resources must differ
EG 2 phytoplankton species may be able to coexist if one is more limited by N and the other is more limited by Ph
If two species are currently competing in the same habitat, what would you expect to happen to the
realized niche breadth of one of the species if its competitor were removed from the habitat? - ANS-✔ ✔it would increase
In what ways can predation be important to organisms and communities? - ANS-✔✔1) Strict distribution or abundance of prey populations
Second major process that structures natural communities
Selective force in predator-prey coevolution
What effect did Schoener and Spiller's (1996) introduction of Anolis lizards to Bahamian islands have on their spider prey? - ANS-✔✔Out of the 12 island studies, 4 had lizards naturally, 4 introduced lizards, and 4 were control groups with no lizards. The introduction of lizards reduced spider density to the same level as the islands with natural lizard occurrence. On the islands with introduced lizards, 13X more spider species went extinct than on the control islands. The spiders were 6X times on the control islands.
What happened when Arctic foxes were introduced to some Aleutian Islands around 1900 in terms of community structure? - ANS-✔✔The introduction of artic foxes lead to a reduction of seabird density and this in turn reduced the guano responsible for fertilizing the island plants. Guano = N & Phosphorus. Less N & P led to a decrease in grasses and increase in shrubs and herbaceous plants. Grassland became tundra!
How do lesser snow geese affect salt marshes in northern Canada? - ANS-✔✔Lesser snow geese summer in salt marshes, and feed on grasses and sedges, These areas are fertilized and grow rapidly following low to medium levels of grazing. With the increase of crop production came an increase in geese population. The high population of geese can drastically wipe out their food sources.
Distinguish between carnivores, herbivores and omnivores. - ANS-✔✔Carnivores: feed on animals
Herbivores: consume plants
Omnivores: consume both
What are true predators? Provide some examples of true predators. - ANS-✔✔Functional classification: kill prey immediately after attacking them EG: big cats, seed eating rodents, ants, plankton consuming whales
What are grazers? Give some examples of grazers. - ANS-✔✔Grazers: Attack a large number of prey during a lifetime and remove only parts of each prey rather than destroying the whole. Their effect on an individual is more difficult to predict, but typically harmful to a varying degree. EG sheep, cattle, leeches, flies that bite animals
How do parasites differ from grazers? What are parasitoids? - ANS-✔✔Parasites: consume part of host/prey. Usually harmful, but usually concentrate on one or very few individuals during their lifetime.
Parasitoids: hymenopterans or dipterans who lay eggs in or on a host, usually another insect EG botflies and zombie wasps. Young consume and kill host during development. 25% of the world's species are parasitoids!!
What are "sit-and-wait" predators? - ANS-✔✔Remain in one place and attack prey that moves within striking distance EG flounders and door spiders. Contrasts forage actively predation, where animals search out prey eg wolves.
What is predator switching behavior? - ANS-✔✔While many food preferences are fixed, sometimes a species can switch their diet when food is common or low. Eg foxes and bears
What is a predator search image? - ANS-✔✔Predator search image: a consumer might develop a specific search image for an abundant prey while ignoring uncommon items. Learning enables them to become increasingly efficient at capturing that most common prey or area of high prey concentration.
Why might herbivores eat different parts of plants? - ANS-✔✔Large herbivores eat above ground parts, or specialized parts. Leaves are commonly eaten because the hold the most nutrition (except for the seeds).
Plant fluids (sap, xylem and phloem) can be sought after for high nutrients.
Many herbivores feed on a narrow range of plants (exceptions = grasshoppers, deer, golden apple snail)
How might herbivores reduce the growth, survival, or reproduction of plants? - ANS-✔✔Below ground herbivores can cause a 40% reduction in growth of bush lupines after 3 months of herbivory by ghost
Give three predictions of the Marginal Value Theorem. - ANS-✔✔(1) optimal stay times should be greater in productive patches, and zero if the extraction rate is below average
(2) stay times should be longer if the travel time was longer
(3) patches should be left faster if the productivity is low
What is the "ideal free distribution" for patch-using consumers? - ANS-✔✔Aggregation: consumers aggregate in profitable patches w high food consumption rate
Interference: competition and interference reduces the per capita rate of consumption
These factors lead consumers to redistribute themselves to get realized profitability from all patches equally (ideal free dist)
What does a predator's functional response describe? - ANS-✔✔The relationship between individual predator food consumption rate and prey density
Give two reasons why a predator's rate of food consumption must eventually reach a plateau in spite of rising prey density. - ANS-✔✔1) Increase in successful hunts = increase in time spent handling prey = decrease in searching time
- Predators cannot feed faster than they can digest, assimilate, and move food through gut
What is a Type 1 functional response? Give an example of organism that might show is a Type 1 functional response. Slide 55 - ANS-✔✔Type 1- # of prey eaten per predator increases linearly to a max and then plateaus. Eg water fleas and baleen whales
What is a Type 2 functional response? Why does the curve in a Type 2 functional response gradually decelerate as the plateau is reached? - ANS-✔✔Most frequent. Consumption rises with prey density, gradually decelelrates then plateaus
Due to consumer having to devote time to handling each prey item. While finding prey may get easier, it still takes time and energy to catch and consume them. Low search time high handling time
What is a Type 3 functional response? How might you account for the first portion of the curve in a Type 3 functional response? - ANS-✔✔At high food density, follows type 2 pattern. At low food density, consumption is less than expected. Always involves alternate prey types, eg there must be another prey which is abundant, profitable and accessible. Once the prey increases enough, predators switch to that prey type. Exists below security threshold, providing a psychological refuge for prey due to:
Few prey having access to most safety
Low abundance means a search image isn't formed for the species
According to Leopold (1933), what are buffer species? - ANS-✔✔Buffer species: stand the ground between predator and prey. EG rodents buffer foxes and rabbits if the rabbit population drops too much
What is a predator numerical response? - ANS-✔✔Increased food leads to changes in consumer population size
Give two possible reasons for a positive predator numerical response. - ANS-✔✔1) Immigration
- Population growth
Negative response associated with interference - ANS-✔✔
What are the assumptions of the Lotka-Volterra (L-V) predation model? (76-88) - ANS-✔✔(1) absence of predators will cause prey population to go into density independent increase exponentially
(2) for predators, assume pop will decrease exponentially in the absence of prey
(3) predators move at random among prey populations that are distributed randomly
(4) predator density doesn't effect the probability of catching prey (no interference)
(5) all responses are instantaneous, no lag for digestion or handling times
(6) number of prey taken increases linearly with the increasing prey density
What does this indicate about the population sizes of both predator and prey? - ANS-✔✔the size of the predator population relies on the size of the prey population, which is limited by the size of the predator population
What would happen if the reproductive rate of the prey (r) increased and/or the hunting efficiency of predators (c1) decreased? - ANS-✔✔the prey population isocline would jump right as the population increases
What does this mean in terms of the prey population? - ANS-✔✔increase
What would happen if the predator death rate (d) increased or the predation efficiency (c1) or reproductive efficiency (c2) decreased? - ANS-✔✔the predator isocline would jump down if the predator population decreased
What does this mean in terms of the prey population? - ANS-✔✔a decrease in the predator population would lead to an increase in prey (right shift in prey isocline)
What would happen if the predator hunting efficiency (c1) increased? What effect would this have on the predator population? - ANS-✔✔prey population would decrease (isocline pulled left) Q4 --> 3
What effect would this have on the prey population? - ANS-✔✔drop in prey population
C1 - predator hunting efficiency - ANS-✔✔increase in C1 leads to drop in both isoclines
neutral stability - ANS-✔✔oscillations between prey/predators is determined by starting conditions
State the Volterra Principle. - ANS-✔✔If two species are destroyed at the same rate by some outside agency (such as the indiscriminate use of pesticides) the prey will increase proportionally and the predators will decrease proportionally!
How might you account for the results predicted by the Volterra Principle? - ANS-✔✔
How does the Volterra Principle relate to the problem of controlling insect pests with broad spectrum insecticides? - ANS-✔✔selective measures are better than indiscriminate insecticides
Give three predictions of the L-V predation model with respect to the predator and prey populations. - ANS-✔✔1) Great fluctuations in populations of both predator and prey
Peaks and lows that alternate regularly
Cycles that are slightly out of phase with one another, with the predator lagging behind
What happened when Gause tested the L-V Model with a protozoan predator and prey? Why? - ANS-✔ ✔the introduction of new prey was necessary for the survival of both predators and prey
Do the well-documented Arctic predator-prey cycles occur because of the predator-prey interactions predicted by the L-V model (that is, are they predator controlled)? - ANS-✔✔they are not only controlled by predators, often the prey population is what determines the predator population
Give two ways in which predators and prey might be limited by their own numbers. - ANS-✔✔ intraspecific competition or mutual interference
How can environmental heterogeneity help to stabilize predator/prey interactions? - ANS-✔✔provide better refuge for small prey populations, dampen oscillations
How can a predator aggregative response help to stabilize predator/prey interactions? - ANS-✔✔ predators congregate in patches of high prey density, predators with aggregative responses avoid areas of low prey density, leaving those small prey populations with refuge!
How might plants compensate for the loss of tissue due to herbivory? - ANS-✔✔Some plants release compounds to attract the predators of their predators
Provide some examples of chemical defenses used by animals against predators. - ANS-✔✔Poison ivy, skunks, poison dart frogs
Provide some examples of mechanical defenses used by animals against predators. - ANS-✔✔ Blepharida beetle larvae slowly chew so as to not disturb the resin in plants
Quills, spines, spikes,
Give three ways in which animals may achieve crypsis. - ANS-✔✔(1) background matching
(2) disruptive patterns (eg zebra, snakes, no clear outline of animal)
(3) countershading (eg sharks!)
How might aposematic colors protect animals from predators? - ANS-✔✔Prey species who have chemical defenses may advertise this fact with bright colors arranged in bold patterns. Thus, a predator who has an unpleasant time can remember to avoid it in the future
What is Batesian mimicry? - ANS-✔✔Batesian: a harmless animal mimics a dangerous one for protection
What is Müllerian mimicry? - ANS-✔✔Mullerian: two dangerous species converge in appearance so that they both gain protection from predators avoiding both
What is aggressive mimicry? - ANS-✔✔Predators use mimicry to resemble their prey
What is "startle coloration" and how might it help protect a potential prey species from its predator? - ANS-✔✔Some prey evolves to reveal a startle coloration when stressed or in danger!
Behavioral defenses: social audible warnings, herd lifestyles, predator satiation (cicadas) - ANS-✔✔
Distinguish between endoparasites and ectoparasites and provide examples of each. - ANS-✔✔ Endoparasite: found within an organism
Ectoparasite: found outside of an organism
Provide examples of microparasites and macroparasites and give two ways in which each can be transmitted. - ANS-✔✔Microparasites: small and multiply within the host. Intracellular, connected with the host cell metabolism and antibody reactions. Transmitted directly from host to host, or through a vector eg mosquitos.
Macroparasites: grow but do not multiply, produce infective stages that are released to infect new hosts. Live on or in body cavities, intercellular in plants. It is possible to estimate a number present in a host. Transmitted via direct contact or lice/fleas/fungi.
Distinguish between a definitive host and an intermediate host. - ANS-✔✔Definitive hosts: the host which a parasite reaches maturity/adulthood in.
Intermediate hosts: multiple hosts the parasite goes through during developmental phases.
List some possible responses of plant and animal hosts to their parasites. - ANS-✔✔The presence of a parasite can induce an immune response, forcing a defense against the foreign entity. The host may die or suffer damage, and the growth pattern can change. Some parasites cause behavior changes to help ensure the spread of transmission EG rabies.
List some of the possible effects of parasites on their host populations. - ANS-✔✔Ant parasite forces it to get eaten by sheep. Tadpole parasite that causes dangerous deformities.
Give some examples of enslaver parasites. - ANS-✔✔Horsehair worms lifecycle: aquatic larvae ingested by crickets, grow inside cricket, eating it from the inside out, parasite forces the crickets to jump into the water, drown, and parasites reproduce.
Give two factors that determine the transmission rate (β) of a disease. - ANS-✔✔1) Probability of transmission (infectiousness)
- Pattern of host behavior as it affects the likelihood of coming in contact with infected individuals
In what way is Rp host-density dependent? - ANS-✔✔It is host dependent because the greater the density of susceptible hosts, the higher the basic reproductive rate of the parasite.
What is the relationship between the critical threshold density (ST) and rate of transmission (β) and length of infectiousness (L)? - ANS-✔✔St decreases as transmission (B) and length of infectiousness (L) increase.
Give two reasons that the number of susceptible hosts (ST) might decline when a disease spreads through a population? - ANS-✔✔When a disease spreads, the number of St declines due to deaths or immunity
What is the relationship between the epidemic and endemic phases of a disease and Rp? - ANS-✔✔ Epidemic: rapid increase of disease incidents bc Rp >>> 1
Endemeic: Rp stays close to 1
Explain why diseases usually show cyclic phases within a population. - ANS-✔✔As disease increases, the amount of susceptible hosts decreases. This cuts down the spread of disease and this allows susceptible host populations to rise, allowing the cycle to continue.
What is herd immunity and how is it achieved? - ANS-✔✔Hold the number of susceptible hosts below St so that Rp is below 1.
On what does the transmission threshold of a vector-transmitted microparasite depend? - ANS-✔✔The transmission threshold is dependent on the ratio of vector to host densities
Give two things that influence Rp for directly transmitted macroparasites. - ANS-✔✔1) Length of reproductive periods
2)Rate of reproduction
On what does the threshold density for indirectly transmitted macroparasites depend? - ANS-✔✔ Depends on the density of both humans and intermediate hosts, aka PRODUCT of the two densities. NOT A RATIO
What is the most common result of coevolution between a parasite and its host over time? - ANS-✔✔ Parasite and host respond to reciprocating selection pressures over evolutionary time. The rest of such pressure may be a tendency for parasites to evolve towards becoming more benign to hosts, and cause them less damage.
What is brood parasitism and in what animals is it most common? - ANS-✔✔Social parasitism, when individuals of one species uses individuals of another to feed and feed its young. Most common in birds that lay eggs in the nests of other birds.
What is kleptoparasitism? - ANS-✔✔Parasites obtain a substantial portion of their food by stealing it from the host. Eg bald eagles and seagulls.
How do life histories of most mutualists differ from those of parasites? - ANS-✔✔The life histories of mutualists are simpler compared to parasites
How does the expression of sexuality of most endosymbionts differ from that of parasites? - ANS-✔✔ Sexuality appears to be suppressed in endosymbiotic mutualists, esp in comparison to parasites/free living organisms
Compare the importance of a dispersal phase between mutualists and parasites. - ANS-✔✔There is a rarely conspicuous dispersal phase in endosymbionts. Parasites rely heavily on dispersal patterns
