Chapter 15: Predation

Question 1

Predation?

Answer 1

consumption of all or part of one living organism by another

Question 2

What is predation important for?

Answer 2

important for transfer of energy between trophic levels, species interaction and controlling abundance

Question 3

Defences against predation can be?

Answer 3

• morphological, physiological or behavioural (behavioural is the easiest to adjust)

Question 4

What are the types of predation?

Answer 4

1. Predator : animal killing and eating another animal
2. Herbivore
3. Parasite
4. parasitoid

Question 5

Herbivore?

Answer 5

prey on autotrophs (impact plant proportion by grazing - the most vulnerable plats are the juveniles that haven’t reached their reproductive ability yet)

• some species benefit form grazing (grasses)
• Plants have evolved defences against herbivory:
• Structural defences
• Secondary compounds
• Toxic substances
• plant-herbivore-carnivore interaction

Question 6

Parasite

Answer 6

lives on/in a host for at least part of life cycle, feeding on the host while still alive (doesnt kill it)

Question 7

parasitoid?

Answer 7

lay larvae on host which feed on host and eventually kill it.

Question 8

Predator ?

Answer 8

• animal killing and eating another animal

Question 9

Math model of predation (lotka-volterra)?

- Equation for prey explained and assumptions

Answer 9

dNprey/dt = rNprey - cNpreyNpredator

• c= average per capita capture rate of prey by predators
  Assumptions:
• assumes all predators are equally efficient (not the case) also that the rate of prey consumption would increase with prey density (easier to find)

Question 10

Math model of predation (lotka-volterra)
- Equation for predator?

dNpredator = b(cNpreyNpredator)-dNpredator

Answer 10

b= efficiency of covering prey consumed to reproduction
d= predator death rate
cNprey would be number of prey consumer multiplied by number of predators minus those that alive.
- Assumptions:
- birth rate (predator) increases with prey density (more for you to feed on/feed your young - more energy can be put into reproduction

Question 11

Low predator density means what with prey population?

Answer 11

• will grow exponentially and as Npredator increases, prey mortality will increase until no more population growth (extinction)
  cNpreyNprey= rNprey
  cNprey= r

Question 12

Predator population growth will stop when the number being born is?

Answer 12

• is equal to the number dying off
  -b(cNpredNprey)= dNpred
  bbNprey= d
  Nprey= d/bc

Question 13

When do we see zero isoclines with predators and prey?

Answer 13

• when prey/predator populations growth are 0 (break point)

Question 14

Predator population does what with prey?(cycle)

Answer 14

• tracks
• time delay (reproduction)
• amplitude of oscillations depends on starting densities
• period of cycle depends on parameter values
• result is neutral stable cycles: populations cycle until environment changes

Question 15

Population regulation:

- assumption?

Answer 15

• growth of predators depends on rate of prey captured which assumes:
  1. Predator consumption increases with prey population (functional response)

Question 16

Explain the three types of predators!

Answer 16

A) Type I: linear increase(lokta) e.g. filter feeders, least common model
B) Type II: number of prey killed levels off (predators satiated or limited by handling time) ex fox and a rabbit
C) Type III: number of prey killed is a lot less to begin with (S shaped)
** Type III can regulate population: preys refuge availability, search image (easier to find the second time around), predator switches to alternate prey, positively density dependent (stabilizing)

Question 17

Population regulation:

- numerical response?

Answer 17

increased consumption of prey results in more predator reproduction

Question 18

Population regulation:

• numerical response
• aggregative response?

Answer 18

• movement of predators into an area because of prey abundance
• quicker and more likely to regulate density

Question 19

Lotka-Volterra was criticized for what?

Answer 19

• being too simplistic (single predator-prey interaction) when there are other factors influencing the control of prey population by predators. Also, predators have an effect on prey in that they are going to evolve different mechanisms to help them survive

Question 20

Prey defences against predation?

Answer 20

• chemical defence
• cryptic/flashing/warning coloration(mimicry)
• object resemblance
• protective armour
• behavioural adaptation (social)

Question 21

Predators might not have a big effect on population size because?

Answer 21

• predators often kill less fit individuals

- death decrease infraspecific competition (within the pre sp.)

Question 22

Foraging decisions

- two theories?

Answer 22

• habitats are patchy, predators often concentrate their foraging
  1. Optimal foraging theory
  2. marignal value theorem

Question 23

Foraging decisions:

1. Optimal foraging theory

Answer 23

predicts decisions that predators make to max gain/minimize cost

Question 24

Foraging decisions:

2.marignal value theorem

Answer 24

• concentrate on most productive patches; stay until no longer as productive and falls to average

Question 25

Coevolution of predator and prey:

- result of?

Answer 25

natural selection: predators get better at catching prey while prey get better at escaping /avoiding.

Question 26

Coevolution of predator and prey:

- Red Queen Hypothesis(Van Valen)?

Answer 26

• as one gets better(predator/prey) , the other is going to get better (catch up) and so they keep evolving together (it takes all the running you can do to keep in the same place)