Ch14/15 Part 1

predation

consumption of one living organism by another

true predation

results in the death of the prey, predators function as agents of mortality

parasites

feed on live host organism, usually with the parasite living on or in the host for part of its life cycle, activity is harmful but usually not lethal in the short term

herbivores

consume only part of an individual plant, can harm but usually doesn’t kill the plant, but seed predation is a form of true predation since it kills the organism

parasitoids

attack the prey indirectly by laying eggs on the host’s body, larva hatch inside host and feed on it until it dies

Pred/Prey Relationships Influence: Distribution

predation pressures shape the spatial patterns and habitats of both species (ex: prey goes to where food is abundant and the predators follow)

Pred/Prey Relationships Influence: Abundance

regulate population sizes and keep ecosystems balances; top-down is predators controlling prey pop. while bottom-up is prey availability controlling predator pop

Pred/Prey Relationships Influence: Adaptations

the species adapt to the other’s strategies (prey gets better at defense and predator gets better at offense)

Pred/Prey Relationships Influence: Food Web and Community Structure

predators influence which species dominate a community (ex: sea otters controlling sea urchin populations preserve kelp forests)

Pred/Prey Relationships Influence: Energy Flow

drive the movement of energy through ecosystems (between trophic levels, 10% of energy move up each level and the rest is lost as heat).

Population cycles

Predator and prey populations directly depend on each other (prey decreasing leads to a decrease in predators, a decrease in predators leads to an increase in prey, and increase in prey leads to an increase in predators which leads to a decrease in prey)

`Real ecosystems remain stable due to: (3 pts)

• habitat heterogeneity (diversities in environment)

• refuges

• immigration

Responses that relate prey consumed to prey density: Functional Responce

increased consumption of prey species by predator when prey pop is larger (eat more food when more is available)

Responses that relate prey consumed to prey density: Numerical Response

increased consumption of prey results in increased predator reproduction (more food means healthier predators)

Responses that relate prey consumed to prey density: Aggregative response

movement or concentration of predators in areas of high prey density (dolphins concentrate where baitfish schools form)

Responses that relate prey consumed to prey density: Developmental Response

intake of prey varies as predator matures (change in diet amount, size, or type through life cycle)

Predator search image:

when a new prey species appears, predators may not recognize it as food right away, a predator may catch one and learn it is prey and then form a search image which helps it get better at finding and killing that prey

prey switching

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

The foraging behaviors of predators are influenced by the time it takes for these other activities to be done: (5 pts)

1. defense

2. finding mates

3. reproduction'

4. care for young

5. predator avoidance

optimal foraging theory

identifies “best” foraging strategy to maximize total energy or energy per unit time for an organism; must balance costs (time/energy expended) and benefit (increased fitness, energy, and nutrient gain)

Foraging considerations: (4 pts)

1. Energy Content: (size and type/quality of prey)

2. Search time: time to remain in patch (quality of patches) and vulnerability while searching

3. Handling Time (capturing, subduing, consuming)

4. Time for other Activities (breeding, etc)