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Population Biology
Unit 2
Chapter 4
Population: group of same species
living in a specific area
This is a population of
bacteria that can be
studied easily in a
laboratory setting.
Exponential growth: as population
gets larger, the growth rate
becomes faster
Population Growth of Houseflies
Populations will
continue to grow
exponentially until
they run out of food or
space.
Growth starts off
slowly because there
are few in the
population that can
reproduce.
Carrying capacity
The total
number of
organisms of
one species
that an
environment
can support
indefinitely
Click on image to start video.
Stopping population growth
When a population becomes larger than
the carrying capacity, limiting factors can
stop population growth.
What can limit the growth of a
population?
Population
Carrying
capacity
J curve
S curve
0
Time
FOOD
PREDATORS
DISEASE
Exponential
growth
SPACE
Characteristics of Population Growth
Predation can affect populations.
What else can affect populations?
What is the relationship between
predator and prey populations?
Lynx and Hare Pelts Sold to the Hudson’s Bay Company
Number of organisms(in thousands)
Lynx
Hare
Times (in years)
Different growth rates
Some populations grow very rapidly.
Why?
– Ex: bacteria
Different growth rates
Some populations
grow slowly. Why?
– Ex: elephants,
bears
Demography
study of human population size, density
and distribution, movement, and its birth
and death rates
Birth rate is the number of live births per
1000 population in a given year.
Death rate is the number of deaths per
1000 population in a given year.
Calculating how fast populations
grow
Birthrate – Death rate = Population Growth
Rate (PGR)
If PGR > 0, then the population is growing.
If PGR < 0, then the population is
declining.