Chapter 7 - Predation, grazing, and disease (SLIDES) Flashcards
What is a predator?
An organism that consumes all or part of another living organism, benefiting itself while often reducing the growth, survival, or fecundity of its prey.
What are true predators?
Organisms that kill prey immediately or shortly after attack and consume multiple prey items throughout their lives.
What are grazers?
Organisms that consume only part of each prey item, do not usually kill them, and attack multiple prey items in their lives.
What are parasites?
Organisms that consume only part of a host, typically do not kill them, and attack one or very few prey items while forming a close association.
What are parasitoids?
Organisms that attack and kill a single prey item (host) in their lifetime and form a close association with it.
How do grazers and parasites impact prey survival?
They may weaken prey, making them more vulnerable to other forms of mortality.
What does increased parasite load indicate in red grouse?
Grouse with higher parasite loads are more likely to be killed by predators.
How does grazing affect competition in plants?
Grazing can weaken competitive species, reducing their interference ability and fecundity.
How can predators promote coexistence between species?
By keeping prey populations low, preventing resource limitation.
What is an example of predator-mediated coexistence?
Intermediate levels of grazing increase biodiversity in the savanna plant community.
How do plants compensate for grazing?
By reducing shading on other leaves and mobilizing nutrient reserves.
How do plants defend themselves against grazers?
By producing toxic chemicals or physical barriers like thorns.
What are the two types of plant defenses?
Constitutive defenses (always present) and inducible defenses (produced in response to damage).
Give an example of a constitutive plant defense.
Bark prevents pathogens and insects from reaching living cells.
Give an example of an inducible plant defense.
Bladderwrack seaweed produces phlorotannins when grazed upon.
What are secondary compounds?
Chemicals that negatively impact herbivores and pathogens, often increasing in production when under attack.
Name some examples of secondary compounds and their uses.
Menthol – Anesthetic
Carotene – Antioxidant and orange coloring
Scopolamine – Motion sickness treatment
Sennoside – Laxative
How does predation impact prey populations?
It may have no effect if individuals killed would have died anyway.
Give an example where predation does not reduce prey population size.
Starfish predation on young mussels does not reduce total mussel bed productivity.
What is the optimal foraging approach?
Predators evolve behaviors that maximize their net energy intake.
What are some strategic decisions predators must make?
Where to forage?
How long to stay in a location?
What to eat (optimal diet width)?
What are generalist predators?
Predators that consume a wide variety of prey due to long search times relative to handling times.
What are specialist predators?
Predators that focus on specific prey because handling time is long relative to search time.
How does prey abundance affect diet width?
When prey is abundant, predators tend to specialize.
Give an example of diet specialization.
Brown bears become selective when salmon is abundant, eating mostly unspawned fish.
What factors dampen predator-prey oscillations?
Crowding of predators or prey
Population subdivision into metapopulations
Predators and prey being part of larger food webs
How does crowding impact predator-prey interactions?
It reduces individual predator consumption rates due to competition or prey defenses.
What is a metapopulation?
A group of subpopulations linked by dispersal.
How does migration affect predator-prey cycles?
It stabilizes interactions and dampens population fluctuations.
What is the basic reproductive number (R0) in disease ecology?
The average number of new infections from a single infected host.
When does a disease spread in a population?
If R0 > 1.
What is the threshold population size (ST)?
The minimum population size needed for an infection to persist. (R0 = 1 (i believe))
