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 individualsthe 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!!