Predation, Parasitism & Mutualism

Predation

Consumption of one living organism by another

herbivores

type of predation

grazers and browsers - consume only part of an individual plant

can harm but not always kill

True predation

results in the death of prey, whether that be an animal or plant

parasites

feed on the live host organism

often an intimate relationship, with the parasite living on or in the host at least part of its life cycle

activity harmful but generally not lethal, at least in short term

parasitoids

attacks the prey indirectly by laying eggs on the host's body

an intimate association with a single host

Predation Distribution of both species

predation pressures shape the spatial patterns and habitats of both species (great migration in Africa)

Predation Abundance of both species

predator-prey dynamics regulate population sizes and keep ecosystems balanced

predation adaptions of predators and prey

each species adapts in response to the other's strategies

predation food web and community structure

predators influence which prey species dominate a community

(sea otters control sea urchins, preserving kelp forest)

Predation energy flow in ecosystems

Predator-prey interactions drive the movement of energy through ecosystems

real ecosystems remain stable because of

habitat heterogeneity

refuges

immigration

functional response

increased consumption of prey species by predator when prey population size is large

zooplankton density rises --> fish feeding rate increases

Numerical response

Increased consumption of prey results in an increase in predator reproduction

owl populations increase when vole populations rise

aggregative response

movement or concentration of predators in areas of high prey density

bottlenose dolphins rapidly concentrate where baitfish schools form

developmental response

intake of prey varies as predator matures

as birds mature, they become capable of capturing and consuming larger, more mobile prey on their own

Predator search image

when new prey species appears, predators often don't recognize it as food right away. after predator catches one, it learns what that prey looks, smells, and moves like

prey switching

A predator may strongly prefer a certain prey but may switch to a more abundant species it can hunt more profitably

herons like eating small fish but will eat lizards

foraging behavior of predators are also influenced by time needed for what other activities

defense

finding mates

reproduction

care of young

predator avoidance

optimal foraging theory

Identifies "best" foraging strategy to maximize total energy or energy per unit time for an organism. Predators need to balance costs and benefits

cost

time and energy expended for foraging

benifit

increased fitness as measured in terms of energy or nutrient gain

energy content foraging considerations

size and type of prey

lower vs higher quality prey

search time foraging considerations

time to remain in patch

high vs low quality patches

vulnerabilities while searching

handling time foraging considerations

capture

subdue

consume

how does coevolution occur between predator and prey?

Predators exert a selective pressure on prey species (a characteristic that helps a prey avoid detection or capture by a predator increases the prey's fitness)

As characteristics evolve in prey that reduce their chance of being caught and eaten, this exerts selective pressures on predators (Failure to capture prey reduces predator fitness through reduced reproduction and increased mortality. More effective means of capturing prey evolve in the predator)

Prey's predatory defenses

behavioral defenses (mobbing, alarm calls, group living)

protective armor (quills, thick shells)

chemical defenses (poisons, alarm pheromones)

cryptic coloration

a prey's predatory defense

body colors and patterns allow prey (or predators) to blend into surroundings

object resemblance

a prey's predatory defense

animals ability to look like something else completely

common in insects

flashing coloration

a prey's predatory defense

exhibit color patches when disturbed by a predator

distracts or disorients predators

eyespot markings

a prey's predatory defense

orients the predator to a less vulnerable body part

warning coloration

a prey's predatory defense

bright colors, distinct patterns warn predator about prey

poisonous, bad taste, etc.

batesian mimicry

a prey's predatory defense

animals evolve coloration that mimics the warning colors of toxic species (coral snake, scarlet snake)

mullerian mimicry

a prey's predatory defense

Unpalatable or venomous species share similar color patterns

Predators learn to avoid all species with similar patterns

Ambush

predators hunting tactic

lie in wait for prey

stalking

predators hunting tactic

high search time

pursuit

predators hunting tactic

high handling time

parasites increase their fitness by using the host in a close, prolonged association for what purpose?

food

habitat

dispersal

how is host fitness is often decreased by the parasite?

stunted growth

emaciation

behavioral modification

sterility

(host may die from a secondary disease or infection)

ectoparasites

live on outside of the host

endoparasites

live within the host

commensalism

one species benefits while the other is largely unaffected