Exam 3: Predation, Parasitism, and Herbivory

parasitsm

-need hot to complete life cycle/adapted to specific hosts

-can be more than one host

-passive vs. active transmission

-direct host to host transmission

-vector to host transmission

passive transmission

parasite does not travel to host (ingestion)

active transmission

parasites travels or penetrates

direct host to host transmission

an intermediate strategy in which parasites do not leave one host until they encounter another

vector to host transmission

Can be carried from one host to another through organisms

Endoparasites

-inside

-stable environment

-many are pathogens

-host immune system

-parasites adjust immune response, camo or hide

Ectoparasites

-outside

-active transmission

-dont need to evade immune system

-exposed to predation

-hosts have mutualistic relationship

Parasitoids

-use host for reproduction

-kills host

-cannot be too effective at finding hosts

Ecological impacts of parasitism

-directly affecting host population

-directly affecting evolution of host species

-indirectly, reduction of host survival and or reproduction can affect another species the host interacts with

Individual impacts of parasitism

-reduction in survival and or reproduction

-change behavior

strats against herbivory

mechanical

chemical

nutritional

mechanical strat

ex. grow spikes

trade-off more energy used

chemical strat

ex. taste bad

Nutritional strat

ex. does not look good to eat

Impacts of herbivory

-reduce individuals in a pop

-change community composition

-especially likely to impact communities when feed on plant that is strong competitor

-evolution of plant species

Predation strats

stalk, ambush, pursuit, random encounter

predation stages

1. encounter

2. detection

3. iD

4. approach (capture)

5. subjunction (gaining control or killing)

6. consumption

Defenses against predation

1. crypsis (camo) ex. stick bug

2. aposematism (warning colors) ex. poison frog

3. chemical warfare ex. skunk

4. physical barriers ex sea urchin

5. mimicry (mullerian and batesian)

6. behavior strats ex. group defense

Mullerian

the type of mimicry in which the mimic and the model are equally dangerous

Batesian

A type of mimicry in which a harmless species looks like a species that is poisonous

Predator-prey cycling and extinction

-high predation efficiency (a) mixed with high prey production (r) most likely to produce extinction (boom bust)

Why not high predatory efficiency and low prey production?

Predators do not wipe out prey pops because large predators can not be supported by small ones

Assumptions of Lotka-Volterra model

A. No density dependent growth- We ignore limits like food, space, disease, prey growth=proportional to pop

B. Predator and prey meet randomly- we assume a well mixed environment

C. Prey is ONLY food source- predator survival depends on prey

D. Prey is the ONLY cause of prey death- we ignore disease, aging

E. No handling time- simplifies interaction, immediate successful predation

F. No immigration or emigration- closed system (easier model), pop changes only from births/deaths

Functional Response

an increase in animal feeding rate, which eventually levels off, that occurs in response to an increase in food availability

I

If the density of prey doubles, each predator (and pop as a whole) eats twice as many prey

II

As prey increase predator increases and predation rate slows

III

Predator ignores prey until a certain density is reached

Maximum Rates of predation

the predator population has grown to a point where it can no longer increase due to the limited availability of prey

Optimal Foraging Theory

Views foraging behavior as a compromise between benefits of nutrition and costs of obtaining food

-waiting time

-handling time

waiting time

average time between aencounters with prey

handling time

average time to consume prey

coevolution

-predator and prey

-parasite and host

-pathogens

-diffuse, specific

-traits under selective pressure from coevolution often involve trade-offs

-some alleles that allow individuals to exploit or avoid exploitation may reduce growth survival or reproduction

diffuse

number of species coevolving with response to each other

specific

two species coevolving

Red Queen hypothesis

each species has to run (evolve) as fast as possible just to stay in place -- because predators, competitors, and parasites also continue to evolve

Sexual Selection

when individuals select mates based on heritable traits/"good genes"