Lecture 17: Predator Prey Cycles Flashcards
Competition
-/-
interaction hurts both species
Predation
+/-
interaction benefits one species but hurts the other
Herbivory
+/-
interaction benefits one species but hurts the other
Parasitism
+/-
interaction benefits one species but hurts the other
Disease
+/-
interaction benefits one species but hurts the other
Mutualism
+/+
each species benefits the other
Commensalism
+/0
one species benefits while the other is unaffected
Some adaptations in +/- interactions for carnivores and herbivores
jaws and teeth
beaks
Some adaptations in +/- interactions for prey and plants
Hiding, including crypsis (hiding through blending into environment)
Mobile escape
Physical protection
Chemical protection
Adaptations for +/- interactions for hosts (against disease)
immune system
secondary compounds
defensive symbionts
tough outer layer
Some adaptations for escaping from predators
distastefulness and/or toxicity (chemical protection)
Unpalatable (toxic)
Secondary compounds (nicotine, mint, capasicin, alkaoids)
Ex. Ash Juniper, Poison dart frog, milkweed plant
Secondary compounds
adaptation used to escape from predators
may be constitutive (always there) or induced (by defoliation or other wounding)
Other factors also affect levels of secondary compounds (ex. tobacco has nicotine when it is grown in poor soil)
Adaptations to defend organisms from pathogens (escape from predator)
-immune system (vertebrates)
-secondary compounds (plants)
- defensive, mutualistic symbionts
- tough outer layer (plant, animal)
Abiotic selective pressure
Nonliving factor in environment that affect survival of organisms, used for physiological ecology
The stress can lessen with adaptation or acclimation of an organism
Drought –> plants strengthening xylem
Low nitrogen levels –> plants holding onto leaves for longer
Saltiness –> fish drinking more water
Biotic selective pressures
Refers to the influence that living organisms have on the survival and reproduction of other organisms in an ecosystem
Can lead to an evolutionary race
Adaptation in one species changes the pressure on the other
Adaptation in the other species changes the pressure on the first etc.
The selective pressure can itself evolve
Leads to Coevolution
Ex. Predation
Co-evolution
From biotic selective pressures
Process by which two or more species evolve in response to each other’s selective pressures
Ex. Co-evolution Pronghorn Antelope Speed
Speed For mobile escape from predators
Antelopes prey for predators (cougars, wolves, coyotes, bobcats) who are fast for selective pressure on antelopes that can run faster to escape predators
In response to predation pressure, antelopes evolve to become faster and predators become faster to catch prey
Ex. Co-evolution for Milkweed and monarch
For every defense that the plant mounts, monarch mounts a counter defense
Plant: dense hairs before leaf (defense themselves against being eaten by insects)
Caterpillar (monarch in larval stage): shaves the hairs (evolved behavior to eat
Plant: toxic latex inside the leaf
Caterpillar: detoxifies it
Co-evolution among prey
Warning signals from prey to predator
Can be useful to look like other bad tasting organisms
Mullerian mimicry
Example of co-evolution among prey
Unpalatable (toxic) species look like each other
Resemblance benefit species to reinforce avoidance behavior of predators
Batesian mimicry
Palatable species (nontoxic) mimics an unpalatable species (toxic)
Able to avoid predation
Predator/Prey population dynamics
+/- interaction
Dynamics over years or decades, no/little evolution
Can lead to extinctions of both
Predator/prey or parasite/host
Can cause populations to cycle
Lotka Volterra Predator-Prey Model
Prey population (N) grows exponentially (r) in the absence of predators, but decrease through predation that is proportional (a) to the multiplication of their population size (N) and the population size of the predators (P)
Predator population size declines exponentially (m) in the absence of prey, but increases in proportion (b) to the prey consumed
Phase plane
A plot of all combinations of P and N with arrows showing the direction of change in P and N over time from each combination of P and N
Isoclines
Helpful in making phase plane
Isoclines are the conditions under which one of the population sizes will not change (dN/dt=0 and dP/dt=0, separately)
Prey switching
when abundance of prey gets low, predators eat other species
dependence of prey population on plant communities of their prey (trophic cascades)
Other reasons predators do not drive prey to extinction
Habitat complexity and limited dispersal
Prey switching by the predator
Spatial refuges
Evolutionary changes in the prey populations
Stochastic
randomly determined; having a random probability distribution or pattern that may be analyzed statistically but may not be predicted precisly
Ex. Rainfall
Anthropogenic
Originating from human activity
Ex. carbon emissions from humans
