Download POPULATIONS

SC STANDARD B-6. 2: Students will demonstrate an understanding of the way
populations are affected by density-dependent factors & density-independent
factors.
POPULATIONS
 CN page
 Topic: Populations
 EQ: What factors affect population size?
How do Populations Grow?
 3 important characteristics of a
population are its :
 geographic distribution
 density
 growth rate
Geographic Distribution
 is the range or area
where the organism is
found
Hooker’s Manzanita
 found in maritime
chaparrel
(threatened habitat
due to development)
 Central California
(Monterrey County)
Franklin’s Bumble Bee
 Most restricted
geographic distribution
of any known bee
 Between Pacific coast &
Sierra Nevada in
Oregon & northern
California
Density
 population density:
the # of individuals
per unit area
 Density is one of the
main characteristics
that describes a
natural population.
Growth Rate
 3 factors affect
 Immigration:
population growth:
 1. # of births
 2. # of deaths
 3. # of individuals
that immigrate or
emmigrate
movement of
individuals into an
area
 Emmigration:
movement of
individuals out of an
area
EXPONENTIAL GROWTH
 growth pattern in
which the individuals
in a population
reproduce at a
constant rate
 Under ideal
conditions with
unlimited resources, a
population will grow
exponentially
LOGISITIC GROWTH
 growth pattern in
which a population’s
growth rate slows or
stops following a
period of exponential
growth
 carrying capacity:
largest # of
individuals of a
population that a
given environment
can support
Carrying Capacity Graph
Limiting Factors to Growth
 In respect to
populations a limiting
factor is anything
that causes
population growth to
decrease.
 Limiting factors are
either:
 Density-Dependent
 Density-Independent
Density-Dependent Limiting Factors
 limiting factor that
 Include:
depends on
population size
 become limiting only
when population
density reaches a
certain level
 1. competition
 2. predation
 3. parasitism &
disease
1. Competition
When populations
become crowded
members of same
or different species
compete for food,
shelter, mates,
space, sunlight
2. Predation
 Predator-Prey
relationships
mechanism of
population control
3. Parasitism & Disease
 Parasites take
nourishment from
their host  host
weakens  does not
usually die
Density-Independent Factors
 affect all the
populations in similar
ways, regardless of
#’s
 Forest fires
 Floods
 Seasonal cycles
 Human interference
(clear-cutting,
damming river)
Human Population Growth
 Population of
humans on Earth
increases with time
Patterns of Population Growth
 Birth rates, death
rates, & the age
structure of a
population help
predict why some
countries have high
growth rates while
other countries grow
slowly.
The Demographic Transition
 the change in a
population from high
birth & death rates to
low birth & death
rates
 Complete concept map from page 134 of
book on page of notebook (landscape)