POPULATIONSDefinition: All the members of a species that live in one place at one time.
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POPULATIONS Definition: All the members of a species that live in one place at one time.
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Transcript of POPULATIONSDefinition: All the members of a species that live in one place at one time.
POPULATIONS
Definition:All the members of a species that live in one place at one time.
PROPERTIES of Populations
Population SIZE The number of individuals in a population
Population DENSITY Number of individuals per unit of area
DISPERSION SPATIAL distribution of individuals within the population
Uniform Random Clumped
PROPERTIES of Populations
Population Growth RATE
Definition The amount by which a population’s size
changes over time.
Population Growth RATE
Depends on: Birth Death Emigration: movement of individuals OUT OF a
population Immigration: movement of individuals INTO a
population
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2 Types of Population Growth
1. Exponential2. Logistic
EXPONENTIAL Model of Population Growth
Population increases rapidly with no limit What will a graph look like? Rare in nature. Why?
“J” shaped curve
Limit on the amount of resources (food / space)
LOGISTIC Model of Population Growth
Accounts for influence of limiting factors (like food, space)
What will the graph look like?
Stretched out “S”When population is small,
birth rate is higher
than death rate
As population reaches
carrying capacity,
death rate increases
When at carrying capacity,
birth rate is equal to
death rate
Population Growth
Limited by Carrying Capacity
Definition:
The number of individuals
the environment can support
over a long period of time
Population Size REGULATION
1. Density Independent Factors: reduce population regardless of population sizeExamples: Weather Fires Floods
Population Size REGULATION
2. Density Dependent Factors: triggered by increasing population densityExamples Food shortages Space limitations Waste accumulation
Example of Exponential Growth Phase (J-Shaped Curve)
Ex. Human Population Human population increased
relatively slowly until about 1650. It then doubled in the next two
centuries It doubled again in the next 80
years.
Our population is now about 7 billion. This increases by 80 million/year This in an increase of 220,980/day. It takes 3 years for the world population to add
the population equivalent of another US.
Example of Exponential Growth Phase (J-Shaped Curve)
Example of Exponential Growth Phase (J-Shaped Curve)
How long will it be until we reach our carrying capacity? What will happen then?
What factors increase our carrying capacity? Farming Medicines Better sanitation
Example of Exponential Growth Phase (J-Shaped Curve)
What impact does this stretching our carrying capacity have on other species. Endangers them or
completely wipes them out.
Example of Exponential Growth Phase (J-Shaped Curve)
What are some consequences of human population growth? Global Warming
Caused by the increasing burning of fossil fuels which lead to the greenhouse effect.
Pollution Acid Rain Pile up of Waste
Ozone Depletion
The End!!
