Download - Friday Meet in the Computer Lab
Chapter 53 Population Ecology
# of Toads per acre
Time
Measuring Density
1. Indirect
2. Direct
3. Mark - Recapture
dN = rmaxN
dt
Factors influencing the rmax
(Biotic Potential)
1. # of Offspring
2. Generation time
3. Reproductive age
4. Sex ratio
Exponential Growth “J” curve
K (carrying capacity)
dN = rmaxN (K-N)
dt KLogistic Growth
Factors Influencing Carrying Capacity (negative feedback)Density Dependent Factors
1. Food
2. Predation
3. Territoriality
4. Disease
5. Waste & Intrinsic Factors
Density Independent Factors
1. Weather
2. Habitat disruption
r – Opportunistic vs. K- Equilibrial
Life Span Short Long
Maturation Short Long
Death Rate High Low
Offspring Many Few
Parental Care None Extensive
Reproductive Age Early Late
Survival Curve Type III Type I
Examples:
Most population are influenced by both factors
Are Humans r’s or K’s ?
Signs left by organisms (nests, tracks, droppings)Counting actual animals
# Area
Do cane toads have high Biotic Potential?
Cane toad Dolphin / Elephant
What is the Earth’s Carrying Capacity?
Data on Human Population Growth
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r or K?
Annual percent increase in the global human population (data as of 2011)
Population Density and Number of Offspring
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Soay Sheep on the Island of Hirta
Lynx and Snowshoe Rabbit Populations
Which do you vote for…. lynx or rabbit?
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Typical Survival Curves
Slide 1Activity: Survivalship Curves
Experimental Evidence of Carrying Capacity
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If this population was harvested for food, what population number would be the most sustainable to maintain the population and provide the greatest amount of food.?
2. Harvest no more then 13 every year
Answer: 1. Harvest only up to a population # 500
Requires 2 capture events:
1. All members of the first capture are marked
2. The marked members of the second capture will give a percentage of how many are in the total group
Calculations
# of total population = # marked in first capture (X) total # in second capture
# of recaptures in second capture
Do Activity: Guano Island
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Clumped
Uniform
Random
Density Types
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Elephant Population Growth of Kruger National Park, South Africa
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All organisms can demonstrate exponential grow in favorable conditions.
Population Dynamics
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Density-dependent regulation by predation
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