Chapter 7 - Predation, grazing, and disease (CHAPTER) Flashcards
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Predator
any organism that consumes all or part of another living organism (its prey or host) thereby, benefiting itself, but reducing the growth, fecundity, or survival of the prey.
True predators
invariably kill their prey and do so more or less immediately after attacking them
Consume several or many prey items in the course of their lives
Grazers
Attack several or many prey items in the course of their life
Consume only part of each prey item
Do not usually kill their prey, especially in the short term
Parasites
Consume only part of each prey item, usually called their host.
Do not usually kill their prey, especially in the short term.
Attack one or very few prey items in the course of their life, with which they therefore often form a relatively intimate association.
Parasitoids
Flies and wasps whose larvae consume their insect larva host from within, laid their ass eggs by their mother.
Ultimately kill their prey, so between parasites and true predators.
Attack one pray item in the course of their lives
Close association.
How do predators impact the fecundity and survival of their prey?
Predators reduce the fecundity and survival of individual prey.
How do grazers and parasites affect their hosts even if they don’t kill them immediately?
They make the prey more vulnerable to other forms of mortality and decrease their competitive abilities.
How do plants respond to predation
By producing more defensive chemicals or structures.
How can predation relieve competitive pressures among prey?
By reducing the number of individuals competing for limited food, allowing some that would have died to survive.
Why do predators sometimes have a limited impact on prey populations?
Because they often target old, young, or weak individuals, leaving fertile individuals to reproduce. What type of prey do predators typically attack?
What type of prey do predators typically attack?
The weakest and most vulnerable individuals.
How can predators indirectly reduce prey abundance?
By causing food shortages for other predators.
How can grazing and infection impact an organism even if they don’t kill it?
They can drastically decrease the organism’s competitive abilities and make it more susceptible to predation.
How do plants respond to grazing?
They can have compensatory responses like shedding leaves or defensive responses such as developing defensive structures and chemicals.
How do some surviving prey compensate after predation?
They may have compensatory reactions that help them survive despite environmental pressures.
How can predation sometimes relieve competitive pressures?
When food is scarce and competition is intense, predation can reduce the number of competitors, allowing some individuals to survive that normally wouldn’t.
What types of individuals do predators usually target?
: The weakest and most vulnerable individuals.
Do predators usually wipe out prey populations?
No, predators often do not wipe out prey populations, as compensatory effects help maintain population stability.
How do predators influence prey abundance?
They can reduce prey abundance, but compensatory effects prevent complete population collapse or significant decline.
Why is the pattern of contact between predators and prey important?
It determines the predator’s consumption rate and its impact on prey populations.
How do true predators and grazers typically find prey?
They forage by moving within their habitat to locate prey.
What determines the contact pattern between predators and prey?
The predator’s foraging behavior and, sometimes, the prey’s evasive behavior.
How do web-spinning spiders and sessile organisms establish contact with prey?
They rely on prey coming to them or settling in suitable locations.
Why is transmission more relevant than foraging for parasites and pathogens?
They spread through direct transmission between infected and uninfected hosts or through free-living stages of the parasite.
What affects the rate of direct transmission of parasites?
The density of both susceptible and infected hosts.
How do free-living parasite stages contribute to transmission?
They are released by infected hosts, and their density, along with that of susceptible hosts, determines the transmission rate.
What does optimal foraging theory seek to explain?
Why certain foraging behaviors have been favored by natural selection.
How is foraging effectiveness typically measured?
By the net rate of energy intake (energy gained per unit time minus energy expended).
According to optimal foraging theory, when should a predator leave a patch?
When they would gain more energy by moving to a new patch.
What does the ideal free distribution suggest about predator behavior?
Predators distribute themselves in proportion to resource availability.
How do predators balance energy intake with the risk of predation?
They make trade-offs between energy gain and the danger of being preyed upon.
What determines a predator’s diet width?
The profitability of prey and whether adding new prey increases the average energy intake.
What type of diet should predators with short handling times have?
They should be generalists with broad diets.
What type of diet should predators with long handling times have?
They should be specialists, focusing on more profitable prey.
When should predators have broader diets?
In unproductive environments where search time is high.
When should predators have narrower diets?
In productive environments where search time is low.
Why do predator and prey populations exhibit coupled oscillations in abundance?
Due to time delays in their responses to each other’s population size.
What is the Lotka-Volterra model?
A mathematical model that captures the tendency for predator-prey populations to exhibit coupled cycles.
Where are predator-prey cycles observed?
In nature, though clear examples are rare, and in laboratory populations of predators and prey.
In what type of organisms are population cycles particularly apparent?
Many parasites, especially microparasites.
What is the basic reproductive number (R0) of a parasite?
The average number of new infections caused by a single infected host in a susceptible population.
What happens when R0 > 1?
A disease will spread.
What happens when R0 < 1?
The disease fails to spread.
What does R0 = 1 represent?
The transmission threshold.
How does crowding affect predator-prey cycles?
It dampens cycles by reducing population growth rates.
What happens when predator density is too high?
Mutual interference occurs, reducing the predator population rate.
How can density-dependent immune responses impact parasite populations?
They can regulate parasite abundance in host populations.
How does prey crowding affect predator abundance?
It limits prey abundance, which in turn limits predator abundance.
How does predator crowding affect prey populations?
It limits predator abundance, reducing their impact on prey.
What are metapopulations?
Predator and prey populations divided into subpopulations but linked by dispersal.
How do differences between patches stabilize predator-prey interactions?
They create asynchrony in fluctuations, dampening cycles.
How can dispersal impact metapopulations?
It can rescue extinct subpopulations, increasing overall persistence.
How does predation act as a disturbance in ecosystems?
It can open up gaps for colonization and interact with other forces like competition.
What is predator-mediated coexistence?
When predation promotes the coexistence of species that might otherwise exclude one another.
How can predators influence competition among species?
By holding down the densities of strong competitors, allowing less competitive species to persist.
At what level of predation is species richness typically greatest?
At intermediate levels of predation.
How does high grazing affect plant diversity?
It reduces diversity because it favors grazing-tolerant plants.
