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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