Predation

Question 1

Define true predators

Answer 1

Individuals who consume prey for their own survival and reproduction

Question 2

Define parasitoids

Answer 2

mostly hymenopterans and dipterans who larvae live on or in a host that eventually kills it, needing one host to complete its life cycle

Question 3

Define parasites

Answer 3

Individuals that harm their hosts, but do not typically kill them

Question 4

Define herbivoures

Answer 4

Individuals that eat plants, where some act like true predators (killing the whole plant) and others act like parasites (only harming part of the plant)

Question 5

Explain variables of Lokta-Volterra predation models equations:
dH/dt = rH-aHP
dP/dt = cHP-dP

Answer 5

top is for population growth rates of prey, bottom for predators:
H = prey
P = predators
r = intrinsic rate of natural increase of prey
a = attack rate of predators
d = death rate of the predators
c = efficiency of converting prey biomass into predator offspring (because 1 prey consumed doesn’t equal 1 new predator)

Question 6

What are the zero isoclines in both the prey and predator Lokta-Volterra models

Answer 6

Prey: H = 0 and P=r/a (natural increase of prey/attack rate of predators)
Predator: P = 0 and H=d/c (death rate of predators/ efficiency of converting prey biomass)

Question 7

Understand how the L-V model predicts sustained oscillations depending on where they cycle, meaning if they cycle close or large than that causes different oscillation sizes

Answer 7

;0

Question 8

What kind of cycling does the L-V model predict

Answer 8

predicts that predators lag behind prey by 1/4 cycle

Question 9

Explain the conclusions of Gause’s microcosom experiments

Answer 9

that 1/4 cycle oscillations occur when spatial distribution of prey is present as well as dispersal (immigration/emigration) of prey/predators

Question 10

Explain the difference in LV and Rosenweig-MacArtuher model in terms of prey growth in prey and predator model

Answer 10

LV: straight line across predators and prey will increase if below and and decrease if higher
RM: parabola (starting at 0 and ending at karrying kapacity)
assume logistic growth over exponentially
when at top of parabola, prey growth is at zero and begins to decline because predators must consume all growth the keep prey population “in check”.

Question 11

Explain the difference in LV and Rosenweig-MacArtuher model in terms of predator growth in prey and predator model

Answer 11

straight up but curves and levels off at predators Karrying Kapacity.
It doesn’t start at 0 because needs a limited prey number to sustain predators
as predators increase they also need more prey to increase to sustain them
then predators are limited at their carrying capacity by something other than prey availability (ex. space)

Question 12

The wide variety of possible predator-prey behaviours is depends on what

Answer 12

where the isoclines cross

Question 13

If isoclines cross at high prey density…

Answer 13

result in dampened oscillations

Question 14

If isoclines cross at intermediate prey density…

Answer 14

sustained oscillations

Question 15

If isoclines cross at low prey density…

Answer 15

mutual extinction

Question 16

What is type 1 functional response to changes in prey

Answer 16

number of prey increases at constant rate then abruptly levels off
(straight line up then straight across)
ex. filter feeders that filter at constant rate

Question 17

What is the second functional response of predators

Answer 17

responds to changes in predator density and relates predator’s prey consumption rate to the predator population density (meaning more predators then less prey/food to share between all predators)
ex. water bug attacking tadpole larvae

Question 18

What is type 3 function response to changes in prey density

Answer 18

number of prey eaten accelerates at low prey density and decelerates at high, attributed to predator behaviours
ex. at deceleration = if predators switch from one prey to another

Question 19

Type 4 function response to changes in prey density

Answer 19

number of prey eaten decreases at very high prey density
ex. prey can defend themselves in larger groups

Question 20

What could cause function response changes in predator density

Answer 20

normally just declines curve
but could have initial increase of consumed prey when predator density slightly increases due to pack predators = cooperative feeding behaviours leading to lower predator density having a higher prey consumption

Question 21

Examples of how evolution has resulted in prey characteristics that reduce the risk of predation

Answer 21

crypsis (camouflage), body size/structure (horns, scales, spikes), behavioural changes (migration, social), mimicry (batesian = parasitic mimicry or mullerian = mutualistic mimicry), toxicity, poisonousness, aposematism = advertising being toxic/poisonous).