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Transcript
Ecology of Populations
Chapter 46
Mader: Biology 8th Ed.
Outline
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Scope of Ecology
Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
– Environmental Impact
Mader: Biology 8th Ed.
Scope of Ecology
•
Ecology - Study of the interactions of
organisms with other organisms and the
physical environment.
– Habitat - Place where an organism lives.
– Population - All the organisms within an
area belonging to the same species.
– Community - All various populations
interacting at same locale.
– Ecosystem - Community of populations.
Mader: Biology 8th Ed.
Ecological Levels
Mader: Biology 8th Ed.
Density and Distribution of Populations
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Population Density - Number of individuals
per unit area or volume.
Population Distribution - Pattern of dispersal
of individuals within the area of interest.
– Ecologists want to analyze and discover
what causes the spatial and temporal
“patchiness” of organisms.
 Limiting Factors are factors that
particularly determine whether an
organism lives in an area.
Mader: Biology 8th Ed.
Uniform Distribution
Mader: Biology 8th Ed.
Random Distribution
Mader: Biology 8th Ed.
Clumped Distribution
Mader: Biology 8th Ed.
Characteristics of Populations
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Intrinsic Rate of Natural Increase (r)
– If immigration (+) and emigration (-)
cancel each other out, then population
growth can simply be modeled by birth
rate minus the death rate.
Mader: Biology 8th Ed.
Population Growth Models
•
Exponential Growth
– Number of individuals added each
generation increases as the total number
of females increases.
 Biotic Potential - Maximum population
growth that can possibly occur under
ideal circumstances.
 Environmental Resistance - All
environmental conditions that prevent
populations from achieving biotic
potential.
Mader: Biology 8th Ed.
Exponential Growth Curve
Mader: Biology 8th Ed.
Exponential Growth Equation
Mader: Biology 8th Ed.
Logistic Growth
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Logistic growth occurs when environmental
resistance comes into play and retards
exponential growth.
– Living populations must eventually come
under the control of environmental
resistance.
Mader: Biology 8th Ed.
Logistic Growth
Mader: Biology 8th Ed.
Logistic Growth
Mader: Biology 8th Ed.
Carrying Capacity
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Carrying Capacity is the maximum number
of individuals of a given species the
environment can support.
– The closer the population to the carrying
capacity, the greater the environmental
resistance.
 Biotic potential is having full effect and
birthrate is a maximum during
exponential growth.
Mader: Biology 8th Ed.
Mortality Patterns
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A cohort is composed of all the members of
a population born at the same time.
– Survivorship is the probability of newborn
individuals of a cohort surviving to
particular ages.
 Survivorship Curves
Mader: Biology 8th Ed.
Survivorship Curves
Mader: Biology 8th Ed.
Survivorship Curves
Mader: Biology 8th Ed.
Age Distributions
•
Populations differ according to what
proportion of the population falls in each age
category.
– At least three structures possible.
 Increasing
 Stable
 Decreasing
Mader: Biology 8th Ed.
U.S. Age Distributions
Mader: Biology 8th Ed.
Regulation of Population Size
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•
Density - Dependent Factors
– Number of organisms present influences
the effect of the factor.
 Competition
 Predation
Density - Independent Factors
– Number of organisms present does not
influence the effect of the factor.
 Natural Disasters
Mader: Biology 8th Ed.
Life History Patterns
•
r - Strategists (Opportunistic)
– Produce large numbers of offspring.
– Small body size.
– Early maturity
– No parental care.
– Density independent controls.
– Good dispersers and colonizers.
Mader: Biology 8th Ed.
Life History Patterns
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k - Strategists (Equilibrium)
– Produce small numbers of offspring.
– Large body size.
– Late maturity
– Significant parental care.
– Density dependent controls.
– Specialists
Mader: Biology 8th Ed.
Human Population Growth
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Human population has an exponential
growth pattern.
– Doubling time currently estimated at 53
years.
Population Size
– 1800
1 Billion
– 1930
2 Billion
– 1960
3 Billion
– 2000
6 Billion
Mader: Biology 8th Ed.
World Population Growth
Mader: Biology 8th Ed.
Country Development
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More-Developed Countries (MDCs)
– Slow population growth.
– High standard of living.
– Completed Demographic Transition.
 North America and Europe
Less-Developed Countries (LDCs)
– Rapid population growth.
– Low standard of living.
 Latin America
 Africa and Asia
Mader: Biology 8th Ed.
Age Distributions
•
Age Structure Diagrams divide populations
into three age groups.
– Pre-Reproductive
– Reproductive
– Post-Reproductive
Mader: Biology 8th Ed.
More-Developed Countries
Mader: Biology 8th Ed.
Less-Developed Countries
Mader: Biology 8th Ed.
Environmental Impact
•
Environmental impact of a population is
measured in terms of:
– Population Size
– Resource Consumption Per Capita
– Resultant Pollution
Mader: Biology 8th Ed.
Environmental Impact
Mader: Biology 8th Ed.
Review
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Scope of Ecology
Population Density and Distribution
Population Growth Models
Survivorship Curves
Age Distributions
Regulation of Population Size
Life History Patterns
Human Population Growth
– Environmental Impact
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.