Chapter 14: Predation
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78 Terms
What is predation?
A: The consumption of one living organism (prey) by another (predator).
Q: How can predators and prey regulate each other’s populations?
A: Predators regulate prey through mortality; prey regulate predator populations through predator growth rate.
Q: What are the 3 basic categories of heterotrophic organisms?
A: Carnivores, herbivores, and omnivores.
Q: What are the functional classifications of predators?
A: True predator, grazer/browser, seed predator/planktivore, parasite, parasitoid.
Q: What is a true predator?
A: An organism that kills prey immediately upon capture, consumes multiple prey, and acts as an agent of mortality.
Q: Do grazers and browsers usually kill plants?
A: No, they typically consume only part of the plant and do not kill it.
Q: Which herbivores function as true predators?
A: Seed predators and planktivores.
Q: How do parasites feed compared to predators?
A: Parasites feed on a living host without killing it immediately.
Q: What are parasitoids?
A: Organisms that lay eggs on a host; larvae feed on and eventually kill the host.
Q: What are the two components of the prey growth equation in the Lotka–Volterra model?
A: Exponential population growth and mortality due to predation.
Q: What is the exponential model of population growth?
dN/dt=rN, where r = per capita rate of increase and N = population size.
What does the predation mortality term cNpreyNpred respresents?
A: Removal of prey by predators.
Q: What does the variable c represent in the predation term?
A: Efficiency of predation.
Q: Full prey population equation in the Lotka–Volterra model?
dNprey/dt=rN-cNpreyNpred
Q: What are the components of the predator population growth equation?
Exponential growth, birthrate based on prey consumption, and constant mortality rate.
Q: What is the predator birthrate term in the model?
b(cNpreyNpred), where b increases with prey captured.
Q: What is the predator mortality term?
dNpred,where d is the probability of ,mortality
Q: Full predator population equation?
dNpred/dt=(cNpreyNpred)-dNpred
Q: How do the Lotka–Volterra equations link predator and prey populations?
A: Each population regulates the other through density-dependent effects.
Q: What pattern appears when the equations are solved?
A: Predator and prey populations oscillate over time.
Q: Do predators ever fully eliminate prey in the model?
A: No — prey never fully disappear, and predators also never completely die out.
Q: What does the Lotka–Volterra model assume about predator and prey?
A: Mutual regulation of their populations.
Q: What links predator and prey in the Lotka–Volterra model?
A: The consumption term cNpreyNpred
Q: In this model, how do prey regulate predator populations?
A: Through predator reproduction (numerical response).
Q: In this model, how do predators regulate prey populations?
A: Through mortality.
Q: What is a predator’s functional response?
A: The relationship between the per capita consumption rate and the number of prey.
Q: What happens to predator reproduction when prey consumption increases?
A: Predator reproduction increases — numerical response.
Q: What is an aggregative response?
A: Movement of predators into areas with high prey density.
Q: Why is the Lotka–Volterra model criticized?
A: It overemphasizes mutual population regulation and ignores factors like cover, prey scarcity, and choice among prey.
Q: Name some additional factors influencing predator–prey interactions.
A: Prey refuges, difficulty finding scarce prey, multiple prey choices, coevolution.
Q: Do predator populations usually grow faster or slower than prey populations?
A: Slower.
Q: What did W. Jedrzejewski observe about weasels and rodent prey?
A: Rodent irruption (300/ha) caused a major increase in weasel population.
Q: What does optimal foraging theory predict?
A: Natural selection favors efficient foragers that maximize net energy gained per unit effort.
Q: What are foraging costs measured in?
A: Time and energy spent searching and handling food.
Q: What is prey profitability?
A: Net energy gained per unit time.
Q: What did N.B. Davies discover about pied wagtails?
A: They prefer medium-sized prey — the optimal size for energy gain.
Q: When might a predator eat a less profitable prey (P2)?
A: When encountered while searching for the more profitable prey (P1).
Q: What does the marginal value theorem predict?
A: How long a predator should stay in a food patch before leaving.
Q: According to the theorem, when should a predator leave a patch?
A: When the rate of energy gain reaches its maximum value.
Q: How does patch richness affect staying time?
A: Predators remain longer in richer patches.
Q: How does travel time (t) affect foraging time (T) in same-quality patches?
A: T increases when travel time increases.
Q: Why must predators consider predation risk?
A: Because many predators are also prey.
Q: What did J. Suhonen find about willow and crested tits?
A: When predation threat is high, they forage in inner branches for safety.
Q: What is coevolution in predator–prey interactions?
A: As prey evolve defenses, predators evolve better hunting strategies.
Q: What is the Red Queen hypothesis?
Species must evolve continuously to avoid extinction (“running to stay in the same place”).
Q: What are predator defenses?
A: Traits that help prey avoid detection, selection, or capture.
Q: Give examples of chemical defenses.
A: Alarm pheromones, odorous secretions, toxins, poisons.
Q: What is cryptic coloration?
A: Coloration that helps prey blend into the environment.
Q: What is flashing coloration?
A: Sudden display of bright colors to distract predators or signal group cohesion.
Q: What is warning coloration (aposematism)?
A: Bright patterns used by toxic or dangerous prey to warn predators.
Q: What is Batesian mimicry?
A: A harmless species mimics a harmful one.
Q: What is Müllerian mimicry?
A: Harmful species share similar warning coloration for mutual benefit.
Q: What are examples of protective armor?
A: Shells and quills.
Q: Name some behavioral defenses.
A: Alarm calls, group living, distraction displays, changing foraging behavior.
Q: What is predator satiation?
A: Producing many offspring at once so predators cannot eat them all.
Q: What are constitutive defenses?
A: Permanent defenses (e.g., coloration, armor).
Q: What are induced defenses?
A: Defenses triggered by the presence or action of predators.
Q: What is ambush hunting?
A: Lying in wait for prey; low success rate but minimal energy cost.
Q: What is stalking?
A: A deliberate form of hunting with long search time but short pursuit time.
Q: What is pursuit hunting?
A: Predators know prey location; minimal search time but high pursuit time.
Q: Name some predator tactics besides physical chase.
A: Cryptic coloration, mimicry, chemical poisons, deception.
Q: How do predators influence natural selection?
A: By selecting prey based on size and shape.
Q: How can predator presence alter prey behavior?
A: Prey reduce activity, lowering their foraging and slowing growth and development.
Q: What did R. Relyea study?
A: Induced behavior and morphology changes in gray tree frog tadpoles exposed to predator chemicals.
Q: What morphological changes occurred in tadpoles with predators present?
A: Deeper tails and shorter bodies (better for escaping dragonflies).
Q: Is herbivory considered predation?
A: Yes, but herbivores usually do not kill the individuals they feed on.
Q: Name impacts of grazing on plants.
A: Biomass loss, reduced vigor, energy reallocation, lower growth/reproduction, increased susceptibility to disease.
Q: Why are grasses tolerant to grazing?
A: Their meristems are close to the ground; grazing may stimulate growth.
Q: What are structural defenses in plants?
A: Hairy leaves, thorns, spines.
Q: Why is plant tissue often low-quality food?
A: High cellulose and lignin content.
Q: What are secondary compounds?
A: Plant chemicals that deter herbivory or reduce digestibility.
Q: Name nitrogen-based secondary compounds.
A: Alkaloids (e.g., nicotine, morphine, caffeine).
Q: What are terpenoids?
A: Secondary compounds such as essential oils.
Q: What are phenolics?
A: Aromatic secondary compounds like tannins and lignins.
Q: What are quantitative inhibitors?
A: Secondary compounds produced in large amounts that reduce digestibility (e.g., tannins, resins).
Q: What are qualitative inhibitors?
A: Potent secondary compounds in small amounts, toxic or deterrent (e.g., cyanide, alkaloids).
Q: How do some herbivores overcome plant chemical defenses?
A: Detoxifying/storing toxins or severing leaf veins before feeding.
Q: How are plants, herbivores, and carnivores interconnected?
A: Plants are eaten by herbivores; herbivores are eaten by carnivores, forming linked trophic interactions.