Chapter 27
Population
Growth
Some Vocabulary
Ecology: The
study of organisms interactions with each other and the non-living part of the
environment
Population: All members of a species that live in a
particular area
Community: All interacting populations of different
species in an area
Ecosystem: All communities in an area plus the
non-living environment
Biosphere: All life on Earth
How Are Populations Distributed in Space and
Time?
Clumped
social
environmental
Uniform
Territoriality
Chemical defense
Random
rare
How Do Populations Grow?
Births, Deaths,
and Migration Determine Population Growth
Change
in population size =
(Births
Deaths) + (Immigration Emigration)
Population Growth
Can Be Expressed As a Rate
Per
capita growth rate (r) is b - d per person per year
How Do Populations Grow?
A Constant Growth
Rate Increases Population Size Rapidly
Population
growth = rN
Where
r= per capita growth rate, N= the original number of individuals
This is exponential growth
How Is Population Growth Regulated?
Rapid Growth
Cannot Continue Indefinitely
How Do Populations Grow?
In Most Cases,
Environmental Resistance Limits Population Growth
Eventually
resources get scarce, waste builds up
Birth rates slow
and death rates increase
The number the environment can support is
the carrying capacity, K
The equation:
Population Growth =
The S-curve of population growth
Patterns of Reproduction
Speed of
potential growth varies depending on:
Age at first
reproduction*
Frequency of
reproduction
Average number of
offspring per birth
Length of
reproductive life span
Death rate under
ideal conditions
Lets practice
How Do Populations Grow?
A Populations
Growth Rate Depends on Patterns of Reproduction
Some Species
Produce Large Numbers of Offspring Quickly (r selected)
Other Species
Produce Fewer But Longer-Lived Offspring (K selected)
How Do Populations Grow?
Delayed Onset of
Reproduction Slows Population Growth
Death Rate Also
Influences Growth Rate
J-shaped exponential growth curves
How Is Population Growth Regulated?
Density-Independent
Factors Limit Population Size
Weather
Natural disasters
Density-Dependent
Factors Have Greater Effect As Population Density
Increases
Predation
Parasitism
Disease
Competition
Lemming population cycles
Competition for Resources Helps Curb
Population Size
Competition May
Be Indirect (scramble) or Direct (contest)
Intraspecific
competition is usually more intense than interspecific competition
Human population growth
How Is the Human Population Changing?
Technological
Advances Have Increased Earths Carrying Capacity for Humans
Early Tools
Allowed Human Populations to Spread and Prosper
Agriculture
Fostered Population Growth
Explosive Growth
Began with the Industrial Revolution
Population Growth
Continues Today But
Is Unevenly Distributed
developing vs. developed countries
How Is the Human Population Changing?
The Age Structure
of a Population Predicts Its Future Growth
The U.S. Population Is Growing Rapidly
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