Transcript zz Sept 20 day nine

POPULATIONS
POPULATIONS

Population: all the members of one species
that occupy a certain area during a certain
time.


Ex. The population of bass in Lake Ontario in
September of 2010
Biodiversity: the number of different types
of species living in an ecosystem.
 Ex.
A tropical rainforest is biodiverse.
 Ex A ______________ is not biodiverse.
DID YOU KNOW???

As of Sept 22nd, 2010, Earth’s population
is estimated to be about
6,872,897,353 !!!!!

By 2040, the population of Earth is
estimated to reach about 9 billion people!
POPULATION GROWTH PATTERNS

Four factors affect the size of a population:
1.
Natality is the number of offspring of a
species born in one year.
2.
Immigration refers to the number of
individuals of a species moving into an
existing population.
(these increase the population)
POPULATION GROWTH PATTERNS
3.
Mortality is the number of individuals of a
species that die in one year.
4.
Emigration refers to the number of
individuals of a species moving out of an
existing population.
(these decrease the population size)
CARRYING CAPACITY
The maximum size of a population that an
ecosystem can sustain is called its carrying
capacity.
Carrying capacity is determined by four factors.
1) Amount of available energy and materials
2) Predation
3) Competition
4) Amount of available space
1. Amount of Available Energy and Materials
If a population grows too large, it will eventually crash
when resources (nutrients, water, or energy) runs
out.
Ex.
2. Predation
If a population grows too large, predation will increase,
reducing the size of the population. (i.e. predators
limit the size of the prey population)
Ex.
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. There
are two types of competition:
TYPES OF COMPETITION
 Intraspecific Competition – competition among
members of the same species
Ex.
 Interspecific Competition – competition between
members of different species
Ex.
4. Space
If a population grows too large, space will run
out. Competition for space will reduce the
population. If the density is too high, stress,
disease, or parasites will reduce the population
size
Ex.
Density-Dependent Factors
These are factors that affect a population
due to its size.
Ex. a food shortage,
Density-Independent Factors
These are factors that affect a population
regardless of its size.
Ex. a flood,