POPULATIONS

POPULATIONS

What is a population?

A group of organisms belonging to the same species that live in a particular area

POPULATIONS

Described based on:•Size•Density•Distribution

POPULATION DENSITY

Measures the number of individual organisms living in a defined space.

Regulation of a population is affected by limiting factors

POPULATION GROWTHFACTORS THAT AFFECT POPULATION

SIZE:• Birth rate• Death rate• Movement into or out of the

population

CHANGES IN POPULATION

IMMIGRATION• Individuals move into an area• Results: The population grows

EMIGRATION• Individuals move out of an area• Results: The population decreases

EXPONENTIAL GROWTH• Occurs when individuals in a population

reproduce at a constant rate• Under ideal conditions with unlimited

resources• But in the real world resources are

limited…

J-Shaped Curve

LOGISTIC GROWTH• Occurs when a population’s growth

slows or stops following a period of exponential growth

• Population growth slows:• Death rate = birth rate• Immigration = emigration

CARRYING CAPACITY

• The largest number of individuals that the given environment can support

S-Shaped Curve

LIMITING FACTORS

LIMITING FACTORS• A factor that causes the

population growth to decrease• Affects may vary depending on

the population and the limiting factor

LIMITING FACTORS1. DENSITY-DEPENDENT FACTORS

2. DENSITY-INDEPENDENT FACTORS

3. BIOTIC & ABIOTIC FACTORS

DENSITY-DEPENDENT

• Depends on the size of the population

• Operate most strongly when a population is large and dense

DENSITY-DEPENDENT1. Competition

•Food, water, space, sunlight, etc.

2. Predation

3. Parasitism

4. Disease

DENSITY-INDEPENDENT• Occurs regardless of how large

the population is• Reduce the size of all populations

in an area by the same proportion

DENSITY-INDEPENDENT• Unusual weather• Natural disasters

• Fires, Floods, etc.• Human activities

• Pollution, Cutting down forests, damming rivers, etc.

ABIOTIC & BIOTIC FACTORS• A change in an abiotic or biotic

factor may decrease the size of a population if it cannot adapt to or migrate from the change.

HUMAN POPULATIONS

POPULATION GROWTH• Human population world-wide has

grown exponentially.• Based on current trends,

scientists predict the population to continue grow at a rapid rate.

POPULATION GROWTH• Population growth slows as it

nears Earth’s carrying capacity because of:• Food and water shortages• Pollution• Spread of diseases

POPULATION GROWTH• An increasing population can

have an effect on:• The amount of clean water• The amount of waste produced• The amount of available fertile soil

for agriculture (food resources)

FERTILE SOIL / AGRICULTURE

• Worldwide demand for land has led to deforestation• Fewer trees to absorb CO2, increase

CO2 contributes to global warming

• Increases the rate of erosion• Decreases the rate of soil

generation

FERTILE SOIL / AGRICULTURE

• Soil has 4 distinct components:• Inorganic minerals• Organic matter• Water• Air

• Soil erosion and deposition—natural processes that move soil from one location to another

CONSUMPTION OF RESOURCES

• As the population increases, so does the demand for resources.

• There is a limited supply of these resources available to sustain the human population

RESOURCES

• Renewable resources• Can be produced at roughly the

same rate that they are consumed

• Food, clean water, timber

RESOURCES

• Nonrenewable resources• Cannot be produced at the same

rate that they are consumed• Fossil fuels, minerals, metals,

ores

RESOURCES

• Sustainable use of resources can be accomplished by:• Reducing consumption• Reusing products• Recycling waste

WASTE

• An increasing population increases the amount of waste produced.• More waste is being produced than can

be managed effectively• Some waste products require

complicated and costly means for removal once introduced into the environment

TECHNOLOGY• Technology has benefited humankind—

But has contributed to the pollution of air, water and land.• Agricultural• Industrial• Alternative energy

*Advances can have a positive or negative impact on Earth

AGRICULTURAL TECHNOLOGY

• Improved ability to grow crops (+)• Conserve fertile soil and reduce erosion (+)• Farm machinery consumes nonrenewable

resources (-)• Contributes to erosion & air pollution (-)• Fertilizers, pesticides, fungicides, etc. can

alter soil composition and effect water, carbon or nitrogen cycles (+/-)

INDUSTRIAL TECHNOLOGY

• Developments in communication, transportation and industry (+)

• Chemicals (CFC’s) deplete ozone layer (-)• Disposal of outdated/damaged equipment (-)• Increases greenhouse gases (mainly CO2) (-)

• Produces acid rain (-)

ALTERNATIVE ENERGY

• Uses natural renewable resources (wind, water, geothermal, solar energy) (+)

• Decreases burning of fossil fuels (+)• Nuclear energy technology is another

alternative—does not impact the atmosphere, but waste produced is a concern (-)

can be

represented bycharacterized by characterized by represented by

which cause a

Go to Section:

PopulationGrowth

can be

represented bycharacterized by characterized by represented by

which cause a

Fallinggrowth rate

S-shapedcurve

Limits ongrowth

No limits on growth

J-shapedcurve

Constantgrowth rate

Unlimitedresources

Go to Section:

Exponentialgrowth

Logisticgrowth