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 GROWTH FACTORS 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

A factor that causes the population growth to decrease Affects may vary depending on the population and the limiting factor

LIMITING FACTORS 1.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-DEPENDENT 1. 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 CO 2, increase CO 2 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 CO 2 ) (-) 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 (-)

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Population Growth can be represented bycharacterized by represented by which cause a Falling growth rate S-shaped curve Limits on growth No limits on growth J-shaped curve Constant growth rate Unlimited resources Go to Section: Exponential growth Logistic growth