Download Study of populations

Climate Change
The Study of Populations
Population
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In ecology, a population includes all living
species
group of individuals of a single species
inhabiting a specific area
share the same environment, they benefit from
the same resources, like water, food and
sunlight
probabilities that they interact together are very
high (ex. at time of the reproduction)
Size of Population
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the number of individuals in the group
Over time, size of a population can
increase, remain stable, or decrease.
Four factors explain variations in the size
of a population: birth rate, death rate,
immigration, and emigration.
Factors affecting size of
population
Factor
Birth rate
Death rate
Immigration
Emigration
Description
Birth of individuals within
a population
Death of individuals
within a population
Arrival of individuals
from other regions
Departure of individuals
to other regions
Methods of Measuring the Size of
Populations
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Counting Individuals
Use of quadrants
Capture-recapture
Counting Individuals
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When possible, the
number of individuals
within a region are
counted
May use aerial
photographs to count
large mammals in
open areas
Quadrats
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Rectangular piece of
land separated by
rope or tape which
divides the piece of
land
Count all individuals
in the quadrant
Average Number of individuals per quadrat = Size of Population
Area of quadrat
Total Area
Size of Population= Average number of individuals per quadrat * Total Area
Area of quadrat
Capture-Recapture
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Used to estimate size of upwardly mobile
animals such as birds, fish, seals, whales
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Install cages or nets in the region that the
population occupies
Counting captured animals and mark with tags,
bands, or paint
Release animals to mix with other unmarked
animals
Replace cages or nets
Count captured animals and recaptured animals
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Estimated Population Size
Number of animals marked and recaptured = number of animals marked
Number of animals captured second time
size of population
Size of population = number of animals marked * number of animals captured second time
number of animals marked and recaptured
Example
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100 geese are captured, marked, and
released
200 geese are captured the second time
and 50 are already marked
Size of population= 100 * 200
50
= 400 individuals
Density of a Population
Number of individuals per unit of area or unit
of volume
 Density of a population=
# individuals / space(area or volume) occupied
 For the same species, the density of the
population may vary depending upon the
habitat
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Density of a Population
Density of population= number of individuals
space occupied (area or volume)
Example: A 100 L aquarium has 5 goldfish in it.
Density of population= 5 individuals
100 L of water
= 0.05 individuals per liter of water
Distribution of a Population
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Way in which the individuals are spread
out within the space that the population
occupies
Clumped distribution, regular distribution,
random distribution
Clumped Distribution
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Most frequent type of
distribution in which
individuals form
groups
Attraction between
individuals or
attraction to a
common resource
Ex. fish living in
schools
Uniform Distribution
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Individuals are
uniformly spaced
throughout the
environment
Antagonistic
interactions between
individuals or local
depletion of
resources
Random Distribution
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An individual has an
equal probability of
occurring anywhere in
an area
Neutral interactions
between individuals,
and between
individuals and local
environment
Ecological Factor
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An element in an environment which can
have an effect on the other living species
which live there
Abiotic- (nonliving) physical or chemical
elements ex. pH
Biotic- (living) linked to actions of living
organisms ex. predation
Abiotic and Biotic Factors
Abiotic Factors
Biotic Factors
Quantity of light
Birth
pH of soil or water
Sickness
Terrain
Amount of food
Thickness of snow
Predation
Temperature
competition
Humidity of the air
Human activities
Limiting Factors
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Ecological factor which reduces the
density of a population
An ecological factor can be limiting if it is
absent in an environment, if there is an
insufficient amount, or if it is in excess
Ex. light, water, prey
Biological Cycles
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Includes periods
during which the
population increases
in size and decreases
in size. These periods
are of fixed duration
and repeat
continuously.
Notes
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See word document