Chapter 15: Predation Flashcards
Predation?
consumption of all or part of one living organism by another
What is predation important for?
important for transfer of energy between trophic levels, species interaction and controlling abundance
Defences against predation can be?
- morphological, physiological or behavioural (behavioural is the easiest to adjust)
What are the types of predation?
- Predator : animal killing and eating another animal
- Herbivore
- Parasite
- parasitoid
Herbivore?
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
Parasite
lives on/in a host for at least part of life cycle, feeding on the host while still alive (doesnt kill it)
parasitoid?
lay larvae on host which feed on host and eventually kill it.
Predator ?
- animal killing and eating another animal
Math model of predation (lotka-volterra)?
- Equation for prey explained and assumptions
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)
Math model of predation (lotka-volterra)
- Equation for predator?
dNpredator = b(cNpreyNpredator)-dNpredator
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
Low predator density means what with prey population?
- will grow exponentially and as Npredator increases, prey mortality will increase until no more population growth (extinction)
cNpreyNprey= rNprey
cNprey= r
Predator population growth will stop when the number being born is?
- is equal to the number dying off
-b(cNpredNprey)= dNpred
bbNprey= d
Nprey= d/bc
When do we see zero isoclines with predators and prey?
- when prey/predator populations growth are 0 (break point)
Predator population does what with prey?(cycle)
- 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
Population regulation:
- assumption?
- growth of predators depends on rate of prey captured which assumes:
1. Predator consumption increases with prey population (functional response)
Explain the three types of predators!
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)
Population regulation:
- numerical response?
increased consumption of prey results in more predator reproduction
Population regulation:
- numerical response
- aggregative response?
- movement of predators into an area because of prey abundance
- quicker and more likely to regulate density
Lotka-Volterra was criticized for what?
- 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
Prey defences against predation?
- chemical defence
- cryptic/flashing/warning coloration(mimicry)
- object resemblance
- protective armour
- behavioural adaptation (social)
Predators might not have a big effect on population size because?
- predators often kill less fit individuals
- death decrease infraspecific competition (within the pre sp.)
Foraging decisions
- two theories?
- habitats are patchy, predators often concentrate their foraging
1. Optimal foraging theory
2. marignal value theorem
Foraging decisions:
1. Optimal foraging theory
predicts decisions that predators make to max gain/minimize cost
Foraging decisions:
2.marignal value theorem
- concentrate on most productive patches; stay until no longer as productive and falls to average
Coevolution of predator and prey:
- result of?
natural selection: predators get better at catching prey while prey get better at escaping /avoiding.
Coevolution of predator and prey:
- Red Queen Hypothesis(Van Valen)?
- 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)
