BIOL 3410 Exam 4 Review

Predation & Herbivory

  • Objectives:

    • Contrast species interactions related to predation and herbivory.

    • Understand how predators and herbivores can limit the abundance of population.

    • Understand and apply the Lotka-Volterra model of predator-prey cycles.

    • Interpret predator-prey graphs.

    • Understand adaptations to minimize predation and herbivory:

      • physical defense

      • crypsis

      • behavior

      • chemical defense (constitutive versus inducible)

Types of Interactions Between Species:

Type of Interaction

Species 1

Species 2

Predation/Parasitoidism

+

-

Parasitism

+

-

Herbivory

+

-

Competition

-

-

Mutualism

+

+

Commenalism

+

0

  • Predation - heterotropic organisms that consume tissue (plants, animals, or cells) as a source of energy

    • Typically distinguished from scavengers and decomposers because they feed on living organisms.

    • True predators eat other animals or insects (i.e. praying mantis, lions, etc.)

Exponential Growth:

ΔNΔt=rN\frac{\Delta N}{\Delta t}=rN

  • Lotka (1925) and Volterra (1926) developed mathematical models of population dynamics that take into consideration predator-prey interactions.

Prey (NN)

Predator (PP)

ΔNΔt=rN−cNP\frac{\Delta N}{\Delta t}=rN-cNP

PP → number of predators

NPNP → number of encounters

cc → efficiency of catching prey

ΔPΔt=a(cNP)−mP\frac{\Delta P}{\Delta t}=a\left(cNP\right)-mP

aa → efficiency of converting captured prey into predators (~10%)

acac → efficiency of catching and converting prey into predator growth

mm → predator mortality rate

  • For stability, both ΔNΔt\frac{\Delta N}{\Delta t} and ΔPΔt\frac{\Delta P}{\Delta t} must equal 0.

    • When ΔNΔt=0\frac{\Delta N}{\Delta t}=0 , then rN=cNPrN=cNP ,