Download Describing Populations Population Distribution

What is competitive exclusion?
Give an example.
 Students
will address how
populations are distributed.
 Students will describe how
populations are sustained over
time.


Geographic range- the area inhabited by a
population
Factors that determine population range:
◦ Abiotic- non-living factors in an organism's
environment
 Ie. Climatic factors, edaphic factors, & social factors
◦ Biotic- living factors in an organism's
environment
 Ie. Predators, competitors, parasites
A species may not be able to expand its pop. range
b/c it can’t survive the conditions in another region

Population Density- measurement of the
number of individuals living in a defined
space
◦ Example: 200 deer in 10 square Km; there would
be 20 deer per square Km
◦ Example: 40 people in 20 square units; there
would be 2 people per square unit

Population Distribution: A way in which
populations are spread in an area
◦ Uniform dispersion: Live specific distances from
one another
◦ Random dispersion: spread randomly within an area
◦ Clumped: Individuals live close together in groups
 Facilitate mating, gain protection, food resources
Occurs when there is fierce
competition for resources or territory
Occurs when individuals set up
territories for feeding, breeding,
and nesting
Few pop. live this way in nature
Occurs in areas of the habitat with
favorable conditions for survival
1.
2.
3.
Each species is adapted to a
limited set of ecological
conditions- patchy in a habitat
Many species gather in social
groups for survival and
reproduction
Adult species don’t disperse
young over a large distance
Occurs when habitat conditions are nearly
uniform (steady resources & organisms don’t
attract or avoid one another)
Create a list that explains how a
population may change in size.
Explain the causes that lead to
these effects.
Cause
Effect
 Students
will address how
populations are distributed.
 Students will describe how
populations are sustained over
time.

Increase in Population:
◦ Immigration: movement of individuals INTO a
population
◦ Births: Increase the number of individuals in
population

Decrease in Population:
◦ Emigration: movement of individuals OUT of a
population
◦ Deaths: Decreases population
Population Growth Rate= (birth rate- death rate) (# of
individuals)
 The
maximum rate of increase per
organism under ideal conditions
◦ Rate depends on the age each generation
starts to reproduce, how often an individual
reproduces, & how many offspring are
produced
 Human population biotic potential= 6% each year
 Rats biotic potential= 1.5% each day
 Bacteria biotic potential= 250% an hour

Directly determined by the amount of
resources available
◦ Exponential Growth
◦ Logistic Growth

Rapid growth that
occurs when a
population grows
under ideal
conditions with
“unlimited”
resources
◦ Lag phase= slow growth
period


J-shaped curve
Increased birth
and immigration
Lag phase
+
 Carrying
capacity- maximum # of
individuals of a pop. an
environment can sustain for a
long period of time
◦
in pop.
resources therefore
less individuals are born & more may
die from deficiency
Growth that may
follow a period of
exponential growth
when a population’s
growth slows/levels
off.
◦ Meets carrying
capacity


S- shaped curve
Occurs when
emigration & death
exceed immigration
& birth
Carrying Capacity
Population

Time
 Is
the combined effects of all the
factors that limit pop. growth
◦ This resistance is the force opposing
biotic potential

Limiting factor: this factor has the greatest
effect in keeping down the size of the
population
◦ Density-dependent: factors that are affected by the
number of individuals in an area (competition,
predation, parasitism and disease)
◦ Density-independent: environmental aspects that are
not affected by how many individuals there are
(typically abiotic like weather, natural disasters,
human activity)
Populations
Can be described by
Dispersion
Three Types:
1.
2.
3.
Density
Growth
Rate
Affected by
Limiting
Factors
Which can be:
1.
2.
Which can be
which are usually
which are usually