Transcript POPULATIONS

POPULATIONS
POPULATIONS
All living things require a balance to be attained
in order to survive. This homeostasis in
nature includes cellular respiration and
photosynthesis, predation and prey, the water
cycle, the carbon and nitrogen cycles, and
even populations!
POPULATIONS
Population can be defined as all the members
of one species that occupy a certain area
during a certain time.
Ex. The population of sharks in the Pacific Ocean
DID YOU KNOW???
As of May 22nd, 2009, Earth’s population is
estimated to be 6,781,521,494!
By 2040, the population of Earth is estimated to
reach ~ 9 billion people!
POPULATION GROWTH PATTERNS
Changes in population size occur when
individuals are added or removed from a
population. There are four factors that affect
the size of a population:
POPULATION GROWTH PATTERNS
Increases are the result natality (birth-rate)
increases as well as immigration increases.
Natality is the number of offspring of a
species born in one year. Immigration refers
to the number of individuals of a species
moving into an existing population.
POPULATION GROWTH PATTERNS
Decreases are the result mortality (death-rate)
increases as well as emigration increases.
Mortality is the number of individuals of a
species that die in one year. Emigration
refers to the number of individuals of a
species moving out of an existing population.
POPULATION GROWTH PATTERNS
The four factors can be expressed
mathematically:
Population Growth =
(births + immigration) – (deaths + emigration)
CARRYING CAPACITY
The maximum size of a population that an
ecosystem can sustain is called its carrying
capacity. It is determined by the availability
of resources, like food and water.
Carrying capacity can be affected by the
following things:
CARRYING CAPACITY
1. Amount of Available Water and Energy
If the population grows too large, it will
eventually crash when resources run out.
Ex. The availability of frogs limits the
population of garter snakes
CARRYING CAPACITY
2. Predation
If the population grows too large, predation
will increase, reducing the size of the
population of the prey.
CARRYING CAPACITY
3. Competition
If resources become more scarce, members
of a population must fight for their survival.
This competition reduces the population by
weaning out the weak or vulnerable
members.
CARRYING CAPACITY
3. Competition
Male lions have been known to kill the
cubs of another lion to reduce the threat of
competition.
http://www.youtube.com/watch?v=NvoyMq84G
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TYPES OF COMPETITION
Intraspecific Competition – competition among
members of the same species
Interspecific Competition – competition
between members of different species
CARRYING CAPACITY
4. Space
If a population grows too large, space will run
out. Competition for space will reduce the
population.
Ex. Moose require a large area to forage.
CARRYING CAPACITY
5. Density-Dependent Factors
These can be anything that affects the
population due to its size
Ex. a food shortage
CARRYING CAPACITY
6. Density-Independent Factors
These can be anything that affects the
population regardless of its size
Ex. a flood