topic 9 - Lotka Volterra predator prey models

Question 1

know yellowstone wolf ex

Answer 1

ok

Question 2

what is predation? what taxa?

Answer 2

• Consumption & killing of one living organism by another

* Taxa: animals, plants, fungi, bacteria, protists

Question 3

predation is usually ____ vs ____? example of when this isnt the case

Answer 3

Usually: big vs. small

• Not always the case: e.g., golden orb-weaver vs. bird prey

Question 4

describe cannibalism

Answer 4

• Cannibalism: killing and eating an individual of the same species - relatively uncommon
○ More common when resources are scarce ie polar bears
○ Sexual cannibalism in the preying mantis

Question 5

when is herbivory predation

Answer 5

• Herbivory: could be considered predation if
herbivores kill the plant they are feeding on
– Seed predation - herbivore is consuming and killing the plant
• Broadly includes parasitoidism

Question 6

describe parasitoidism vs parasites

Answer 6

parasitoidism 
		-Small vs. big
		• Parasitoid insects lay eggs in/on
		host
		• Larvae feed on & kill host
		– Ecto vs. endoparasitoids
		• Same effect as traditional
		predation
	•  Parasites (sub-lethal): harm, but do not kill hosts

Question 7

Cycles of abundance in snow shoe hares and their predators: hypotheses (3)

Answer 7

a) Abundance cycles driven by plants; variation in solar radiation altered plant
growth causing variation in hare population size.
b) Overpopulation theories:
-Decimation by disease and parasitism.
-Physiological stress at high density.
-Starvation due to reduced food at high density.
c) Role of predators:
-Predation can account for 60–90% of mortality during peak hare
densities.

Question 8

what is the LV predator prey model? two equations?

Answer 8

• Mathematical model to express the relationship between predator & prey populations
Two equations:
1. Prey population growth (influenced by predation - mortality)
2. Predator population growth (influenced by # prey – essential
resource that influences birth rate (numerical response))

Question 9

• LV POP GROWTH FOR PREY - look at equation and graphs

Answer 9

1. Term for births of prey (# births): exponential population growth eq. - (rNprey)
   
   2. Mortality term (# deaths): removal of prey from population by predation - c(NpreyNpred)

Question 10

assumptions of LV pp model for prey

Answer 10

• Assumes per capita predation rate increases
linearly with # prey due to more encounters
(see fig.)
• c = predation efficiency, defined by the slope of
line (constant)
• Total predation = product of per capita
predation rate, # predators, # prey
Lv pop growth FOR PREDATORS

Question 11

terms for LV for predators

Answer 11

1. Term for births of predators (# births): influenced by # prey consumed - b(cNpreyNpred)
   
   2. Predator mortality (# deaths): not influenced by # prey (assumption) - (dNpred)

Question 12

assumptions of LV model of pp for predators

Answer 12

• Assumes # predator births increases linearly with amount
of prey consumed (see fig)
• Slope of the line (b) represents efficiency with which
food (prey) is converted into reproduction for predators
• # predator births = product of (b) & total predation
(cN preyN pred)
• Predator mortality rate is assumed to be a constant (i.e.,
not influenced by # prey)
• d = per capita death rate
• N pred = # predators

Question 13

is lv pp model density dependent?

Answer 13

Equations explicitly link the 2 populations
– Each function as a density-dependent regulator of the other
• Predators regulate prey populations
– Source of density-dependent mortality
•
• Prey regulate predator populations
– Density-dependent effect on predator births

Question 14

look at lv pp model graphs, equations, and lags

Answer 14

ok

Question 15

V PP model assumptions (4)

Answer 15

1. Prey have unlimited resources (no intraspecific regulation). In the
   absence of predators, prey grow exponentially
   
   2. Prey are removed from the population at a constant rate,
      proportional to prey population size (functional response)
   3. Predators are dependent on a single prey species for food & predator
      births are proportional (linearly related) to prey density (no satiation)
   4. Over time, the environment does not change in favour of one species
      & genetic adaptation is sufficiently slow.

Question 16

lv pp model doesnt account for:

Answer 16

• Population growth of many prey species is at least partially
determined by food supplies, not just predators
– Prey will not grow exponentially in predator absence
• Many prey species respond to entire communities of
predators, not just 1 species
• Predator populations are often affected by factors other than
prey density (competition, emigration, >1 prey species)