Modelling Predation Flashcards
What is Constitutive Defences?
Structure on its body are always present
What is Induced Defences?
Only develops when it detects a threat
What are the Structural Defences of Plants?
Thorns, Spines and Trichomes
Thorns
modified branches
Spines
modified leaves
Trichomes
- little hairs that grow on a plant
- deter small herbivores
- depending upon stiffness, large herbivores
Chemical Defence: Aposematism
warning colouration to warm off a predator
Chemical Defence: Batesian Mimicry
- organisms evolve similar markings to Unrelated unpalatable/poisonous species
Chemical Defence: Mullerian Mimicry
- co-occurring species evolve similar warning colours
- All unpalatable/poisonous
What are the consequences to reduced activity in the presence of predators?
low food = can’t produce much colour red to warn off predators
High food = produces red (bright) so it warns off predators
Co-evolutionary Arms Race
constant evolution of new defences by prey = ability to overcome defences by predators
Do predators also evolve?
when a prey evolve to less predation but predator would evolve again by overcoming that evolution produced by the prey and this goes in circle
Learned Delayed Density Dependence causes population cycling to
- overshoot carrying capacity
- Delayed response to changing resource availability
Prey Population (N): (dN/dt) = rN - cNP
- (dN/dt) : change in prey population
- rN: growth of prey pop’n
- c: capture efficiency
- NP: encounter rate b/w predator and prey
Predator Population (P): (dP/dt) = acNP - mP
- (dP/dt): change in predator population
- a: efficiency of converting food/prey into offspring
- cNP: # of prey consumed
- mP: mortality rate of predators
Prey Population will be stable when rN - cNP =
0 (zero)
Stability occurs when growth rate =
predation rate
P = r/c represents
number of predators = prey growth/ predator capture efficiency
P < r/c means Prey population
increases
P>r/c means Prey population
decreases
Predators population: N = m/ac represents
- number of prey
N = m/ac would only represents stability when
when prey is sufficient to support predator mortality / addition of new predators
N > m/ac means Predators population
increases
N < m/ac means predators population
decreases
graph in Horizontal direction: Top box is
more predators = prey decline
graph in Horizontal direction: bottom box is
less predators - prey increase
Equilibrium/zero growth isocline
how many predators needs to be present in an area for the prey population to be stable
graph in Vertical direction: Left box is
less prey = predators decreases
graph in Vertical direction: Right box is
more prey = predators increase
Joint Population Trajectory
how a change in one population affects the other
Yellow zone (bottom left box)
predator and prey populations are both Increasing;
an increase in the prey population allows an increase in the predator population
Green zone (top right box)
predators still have enough prey to feed on, but prey population decreases; an increase in the predator population causes a decline in the prey population
Blue zone (Top left box)
not enough prey to support predator population; a decrease in the prey population causes a decrease in the predator population
Green zone (Bottom left box)
a decrease in the predator population allows an increase in the prey population
Lotka-Volteraa Models of Predator-Prey Interactions does not
- account for density-dependent factors or any effects of delayed density dependence
- account for often complex foraging strategies of predators
What is Functional Responses?
How a predator rate of food changes depending how their food consumption changes
- Prey density vs rate of food consumption
TYPE I Functional responses
- linear consumption until satiation
- rare
TYPE II Functional responses
- consumption slows as satiation approaches, as they consume more, handling time increases
TYPE III Functional responses
- consumption greatest at moderate prey densities, slows as satiation approaches
Why is consumption also slow at low prey densities?
- prey hide in refuge ( small population, so its easier for them to hide from predators)
- predators are not well practiced at catching prey when density is low
- prey switching to what is more abundant
