Transcript Chapter 44 Ecology of Populations Notes

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
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Scope of Ecology
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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.
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Ecological Levels
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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.
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Uniform Distribution
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Random Distribution
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Clumped Distribution
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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.
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Population Growth Models
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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.
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Exponential Growth Curve
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Exponential Growth Equation
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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.
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Logistic Growth
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Logistic Growth
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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.
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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
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Survivorship Curves
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Survivorship Curves
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Age Distributions
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Populations differ according to what
proportion of the population falls in each age
category.
– At least three structures possible.
 Increasing
 Stable
 Decreasing
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U.S. Age Distributions
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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
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Life History Patterns
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r - Strategists (Opportunistic)
– Produce large numbers of offspring.
– Small body size.
– Early maturity
– No parental care.
– Density independent controls.
– Good dispersers and colonizers.
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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
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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
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World Population Growth
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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
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Age Distributions
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Age Structure Diagrams divide populations
into three age groups.
– Pre-Reproductive
– Reproductive
– Post-Reproductive
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More-Developed Countries
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Less-Developed Countries
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Environmental Impact
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Environmental impact of a population is
measured in terms of:
– Population Size
– Resource Consumption Per Capita
– Resultant Pollution
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Environmental Impact
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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.