UNIT 3 Chp 5.1 and 5.2
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Transcript UNIT 3 Chp 5.1 and 5.2
UNIT 3
Chp 5.1 and 5.2
Population Growth
5.1 How populations
grow
Population – a group of organisms of a
single species that lives in a given area.
Researchers study populations’ geographic
range, density and distribution, growth
rate, and age structure.
Geographic Range
The area inhabited by a
population.
Can vary greatly in size
Geographic range of the
American Chestnut
Population Density
Number of individuals per unit area.
Random
Uniform
Clumped
Population Growth
Factors that affect population size are the
birthrate, death rate, and the rate at which
individuals enter or leave the population.
Populations can grow if more
individuals are born than die in any
period of time.
Population Growth
Immigration- when a population grows if individuals
move into a given area.
Emigration- when a population decreases in size due
to individuals leaving the area.
Exponential Growth- under ideal conditions with
unlimited resources, a population will grow
exponentially.
Logistical Growth- occurs when a population’s
growth slows and then stops, following a period of
exponential growth.
Exponential Growth
Logistic Growth
K is the
Carrying
Capacitymax # of
individuals
of a species
that an
environment
can support.
5.2 Limits to Growth
Limiting factors determine the carrying
capacity of an environment for a species.
Density-Dependent Factors-include
competition, predation, herbivory, parasitism,
disease, and stress from overcrowding. They
only act on dense populations, not small
scattered ones.
Density-Independent
Limiting Factors
Unusual weather, hurricanes, droughts,
wildfires, floods, can cause a population
to “crash” and then slowly build back up
over time.
Invasive Species
A non-native species introduced into an
area (usually be humans).
Many invasive species will overpopulate
an area a take up resources from native
species.
Purple Loosestrife
Asian Longhorn Beetle