objectives - chapter 14
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Objectives - Chapter 14. 1. What is an exploitative interaction? 2. Define Functional response Define Numerical response Describing predator/prey interactions mathmatically (Lotka Volterra models). Exploitation (Predation, etc.). - PowerPoint PPT PresentationTRANSCRIPT
Objectives - Chapter 14
1. What is an exploitative interaction?
2. Define Functional response
3. Define Numerical response
4. Describing predator/prey interactions mathmatically (Lotka Volterra models)
Exploitation (Predation, etc.)
• Most important biological interactions - Consumption of one organism (or part thereof) by another
Parasites
• Eat only one or two different organisms during a lifetime--- as opposed to other types of predators (e.g., grazers that eat a large number of plants)
• Host and habitat are the same!!!
• Leopold - “parasites kill far more organisms than we know” - selection pressure
Exploitation
Many relationships not clear cut
E.g., Competition between two organisms where one eats the other.
Exploitation (Predation, etc.)
Definitions of each are problematic----
Common to all interactions:
One organism living at the expense of another.
Responses of Consumer Species to Variation In the Abundance of Their Food Species
As the density of the food species increases, the consumer species responds by:
1. Increasing the rate at which they eat the food species.
“Functional Response”
Theoretical Functional Response Curves
In Type 1 exploitation interactions, time required to find prey (search time) is the only factor limiting consumption rate.
Satiation
Increasing abundance of food organism proportionally reduces searching time, increasing rate of prey consumption.
Consumption rate increases until consumers cannot eat any faster (Satiation)
Lo Prey Density Hi
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ate
Theoretical Functional Response Curves
In Type 2 exploitation interactions, consumption rate is influenced by two separate processes:
Searching“Handling”
Satiation
At low prey density, searching time limits consumption rate.
At moderate prey density, handling time limits consumption rate.
Lo Prey Density HiLo Prey Density Hi C
on
sum
pti
on
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e
At high prey density, predator At high prey density, predator consumption rate limited by consumption rate limited by satiation.satiation.
Theoretical Functional Response Curves
In Type 3 exploitation interactions, the consumer eats multiple food species.
When a food species is rare, the consumer may ignore it and focus on consuming more common species.
As a food species becomes more abundant, the consumer switches to eating more of that species.
Prey Switching and Learning Curve Limit Prey Consumption Here
Responses of Consumer Species to Variation In the Abundance of Their Food Species
As the density of the food species increases, the consumer species responds by:
2. Increasing population size due to increased survivorship and reproduction AND immigration from surrounding areas.
“Numerical Response”
Numerical Response:
1. Effect of prey on predator reproduction:
• Increased food (prey)
• Increased growth rate, survivorship
• Earlier reproduction, increased offspring/female, increased females
• Increased R and r, increased # predators
Predator Responses
Numerical Response:
2. Effect of prey density on predator migration
Predator Responses
Increased food
Increased # predators
Predators attractedResidents remain
1951 1952 1953
Brown Lemming 1-5 15-20 70-80
Pomarine Jaeger uncommon breeding breeding
no breeding 4/mi2 18/mi2
Numerical Response-Field Examples
1951 1952 1953Brown Lemming 1-5 15-20 70-80
Pomarine jaeger uncommon breeding breeding
no breeding 4/mi2 18/mi2
Short-eared Owl Absent one record breeding3-4/mi2
Numerical Response-Field Examples
1951 1952 1953Brown Lemming 1-5 15-20 70-80
Pomarine jaeger uncommon breeding breeding
no breeding 4/mi2 18/mi2
Short-eared Owl Absent one record breeding3-4/mi2
Snowy Owl Scarce breeding breedingno breeding .2-.5/mi2 .2-.5/mi2
many non few non
Numerical Response-Field Examples
Responses of Consumer Species to Variation In the Abundance of Their Food Species
As the density of the food species increases, the consumer species responds by:
3. Combination of #1 and #2.
“Combined Response”
Mini Summary:To regulate the food species population, the
consumer population must be able to eat food organisms faster than they can reproduce, as
determined by:
1. Consumption rate: (Functional Response).
2. Consumer Species Rate of Increase: (Numerical Response)
3. Combined Response of Consumer Species
4. Consumer Efficiency: Number of food organisms required to produce a new consumer organism.
Prey Model - Figure 14.16
dNh/dt = rhNh - pNhNp
dNh/dt = Rate of prey population change
rh = intrinsic growth rate of prey
p = ingestion efficiency
Nh = density of prey
Np = density of predators
Lotka Volterra Predator-Prey Model
Predator Model – Fig. 14.16
dNp/dt = cpNhNp - dpNp
dNp/dt = rate of predator change
c = production efficiency of predator
p = ingestion efficiency
Nh = density of prey
dp = death rate of predator
Np = density of predators
Lotka Volterra Predator-Prey Model
Lotka Volterra Predator-Prey Model
Prey population
Predatorpopulation Predator
increasingPredator
decreasing
Lotka Volterra Predator-Prey Model
Prey population
Predatorpopulation
Predator isocline
Predatorincreasing
Predatordecreasing
Lotka Volterra Predator-Prey Model
Prey population
Predatorpopulation
Prey isoclinePrey
increasing
Preydecreasing
Prey population
Predatorpopulation
Preyincreasing
Preydecreasing
Preyincreasing
Preydecreasing
Predatorsincreasing
Predatorsdecreasing
Predatorsincreasing
Predatorsdecreasing
Lotka Volterra Predator-Prey Model
Question:
1. Are prey species populations being regulated by density dependent or density independent controls?
2. What about the predator species?
Predator-Prey Model
• Types of exploiters
• Functional response
• Numerical response
predator reproduction
predator migration
Lotka Volterra predator-prey model
Summary for Today