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