Mrs. Yanac
Biology 1B
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DENSITY – The number of individuals in
particular area
GROWTH RATE – The rate at which the
population increases
GEOGRAPHIC DISTRIBUTION – The
area inhabited by the population
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# of BIRTHS (Birth rate)
# of DEATHS (Death rate)
# of individuals that ENTER
(Immigration) a population
# of individuals that LEAVE
(Emigration) a population
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Under IDEAL
conditions with
UNLIMITED
resources, a
population will grow
& grow
(exponentially)
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As resources become
LESS available, the
growth of a
population SLOWS
or STOPS
Leveling off is
known as carrying
capacity (total # of
individuals a
population can
support)
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EX: White-Tailed Deer Habitat
Food Source = 10 deer
Carrying Capacity = 10 deer
Although the water, cover &
space are sufficient for more
deer, the limiting factor of the
food supply determines what
this habitat will support.
Carrying capacity does not
exceed the number that the
most limiting factor will allow
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Any factor that
causes the
population to
decrease
Younger or weaker animals die
(-) There may be fewer animals born
(-) Takes more energy just to survive
Animals could get burned
(-) Food & cover burned
(-) Water source may
evaporate
(+) Re-growth of nutritional
vegetation
(+) Encourages grass cover
(+) Cleans out debris
(-) Movement is difficult,
requires more energy
(-) Food is difficult, often
impossible, to find
(-) Thermal cover is
difficult to reach & often
ineffective
(+) Insulates plants &
animals from extreme cold
(-) Vegetation withers,
food disappears
(-) Water sources dry up
(-) Cover thins
(-) Habitat & wildlife
washed away or
inundated.
(-) Vegetation drowns
(+) Disperse seeds &
soil
(-) Crowding and
trampling of
vegetation
(-) Disease spreads
easily
(-) Vegetation is
stripped
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Factors that depend on the
size of a population
Examples:
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Competition
Predation
Parasitism
Disease
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Affect all populations
regardless of size.
Examples
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Natural disasters
Weather
Human activities
RECAP:
1. What are 4 factors that affect
population growth?
2. What are 3 characteristics of a
population?
3. What type of growth goes
through a period of rapid
growth, then slows down or
stops?
4. What is the term for the largest
# of individuals a population
can hold?
5. What type of growth grows at a
constant rate?
6. What are some densitydependent limiting factors?
7. What are some densityindependent limiting factors?