Populations and the Populations and the EnvironmentEnvironment

Chapter 5, 6.2 and 6.3Chapter 5, 6.2 and 6.3

5.1 How Populations Grow5.1 How Populations Grow

Population DensityPopulation DensityPopulation density is a Population density is a measurement of the measurement of the number of individuals number of individuals living in a defined living in a defined space.space.Scientists can Scientists can calculate population calculate population density.density.

Population dispersion Population dispersion refers to how a population refers to how a population is spread in an area.is spread in an area.

Clumpeddispersion

Uniformdispersion

Randomdispersion

Clumped

Uniform

Random

Population GrowthPopulation Growth

The size of a population is The size of a population is always changing.always changing.

Four factors affect the size Four factors affect the size of a population.of a population. Immigration Immigration Births rateBirths rate Emigration Emigration Death rateDeath rate

Population growth is based on Population growth is based on available resources.available resources.

Exponential growthExponential growth is a rapid is a rapid population increase due to an population increase due to an abundance of resources.abundance of resources.

Most populations are regulated by predators, Most populations are regulated by predators, disease, and the availability of resources.disease, and the availability of resources. Because of this population will not exceed the Because of this population will not exceed the

environmental carrying capacityenvironmental carrying capacity As a population grows, limited resources become As a population grows, limited resources become

depleted and the growth of the population slows.depleted and the growth of the population slows.

However,However,

Logistic growthLogistic growth occurs when a population is occurs when a population is facing limited resources.facing limited resources.

Carrying capacity is the maximum number of Carrying capacity is the maximum number of individuals of a particular species that a individuals of a particular species that a particular environment can support.particular environment can support.

5.2 Limits to Growth5.2 Limits to Growth Limiting factors – control the growth of a Limiting factors – control the growth of a

populationpopulation

Density-dependent factorsDensity-dependent factorsThe rate at which they become depleted depends upon the The rate at which they become depleted depends upon the population density of the population that uses them.population density of the population that uses them.

CompetitionCompetition PredationPredation DiseaseDisease OvercrowdingOvercrowding Herbivory Herbivory

Example: Limiting GrowthExample: Limiting Growth

Density-independent limiting factors limit a Density-independent limiting factors limit a populationpopulation’’s growth regardless of the size and s growth regardless of the size and density.density. HurricanesHurricanes DroughtDrought FloodsFloods WildfiresWildfires

1.During which time period is birth rate higher than death rate?2.During which time period are birth rate and death rate equal?3.During which time period is death rate higher than birth rate?

5.3 Human Population Growth5.3 Human Population Growth For most of human existence, the For most of human existence, the

population grew slowly because life was population grew slowly because life was harsh. harsh. Food was hard to find. Predators and diseases Food was hard to find. Predators and diseases

were common and life-threatening. were common and life-threatening. These limiting factors kept human death rates very These limiting factors kept human death rates very

high. high.

Improved nutrition, sanitation, medicine, and Improved nutrition, sanitation, medicine, and healthcare, dramatically reduced death rates.healthcare, dramatically reduced death rates.

birthrates in most parts of the world remained high. birthrates in most parts of the world remained high.

The combination of lower death rates and high birthrates led The combination of lower death rates and high birthrates led to exponential growth.to exponential growth.

6.2 Using Resources Wisely6.2 Using Resources Wisely

How do we obtain what we need from local and How do we obtain what we need from local and global environments without destroying those global environments without destroying those environments?environments?

Environmental Resources we affect:Environmental Resources we affect: SoilSoil FreshwaterFreshwater AirAir

Soil ResourcesSoil Resources

Healthy soil supports both agriculture and Healthy soil supports both agriculture and forestry.forestry. TopsoilTopsoil – rich in organic matter and nutrients – rich in organic matter and nutrients Loss of fertile soil can have dire consequences.Loss of fertile soil can have dire consequences.

ErosionErosion – removal of soil by water or wind – removal of soil by water or wind DesertificationDesertification DeforestationDeforestation

Desertification RiskDesertification Risk

Soil Use and SustainablilitySoil Use and Sustainablility

Leaving stems and roots of the previous Leaving stems and roots of the previous yearyear’’s cropss crops

Crop rotationCrop rotation Select HarvestingSelect Harvesting

Freshwater ResourcesFreshwater Resources

drinking water, industry, transportation, energy, drinking water, industry, transportation, energy, and waste disposal. and waste disposal.

Some farmland relies heavily on irrigationSome farmland relies heavily on irrigation

Water PollutionWater Pollution

Many serious environmental problems Many serious environmental problems occur in our own backyard.occur in our own backyard.

Agriculture introduces large amounts of Agriculture introduces large amounts of chemicals into the global ecosystem.chemicals into the global ecosystem.Including: pesticides, herbicides, and Including: pesticides, herbicides, and fertilizersfertilizers

Many chemicals, such as DDT, have been banned in the Many chemicals, such as DDT, have been banned in the US, but the effects of their use still circulate.US, but the effects of their use still circulate.Causes biological magnificationCauses biological magnification

Water Quality and SustainabilityWater Quality and Sustainability

Protecting the water cycleProtecting the water cycle Clean up pollutionClean up pollution Conserve waterConserve water

Atmospheric ResourcesAtmospheric Resources

Air quality has a direct impact on health.Air quality has a direct impact on health. PollutionPollution

Global temperatureGlobal temperature

Coal-burning power plants send smoke, Coal-burning power plants send smoke, containing sulfur, into the atmosphere through containing sulfur, into the atmosphere through smokestacks.smokestacks.

Scientists now know that the sulfur can combine with water Scientists now know that the sulfur can combine with water vapor to produce sulfuric acid, which will fall back to earth as vapor to produce sulfuric acid, which will fall back to earth as acid rain.acid rain.Acid rain causes forest damage, and dead lakesAcid rain causes forest damage, and dead lakes

Robl, Ernest H. Acid Rain Damage. Photograph1990. Web. 21 Oct 2010.

Decrease in the amount of ozone (ODecrease in the amount of ozone (O33) in the ) in the

atmosphere allows more UV radiation to reach atmosphere allows more UV radiation to reach the earththe earth’’s surface.s surface.

This can cause an increase in diseases related to UV This can cause an increase in diseases related to UV exposure such as cancer and cataracts.exposure such as cancer and cataracts.The major cause is chlorofluorocarbons (CFCs) commonly The major cause is chlorofluorocarbons (CFCs) commonly used in refrigerators, air conditioners, and in aerosols.used in refrigerators, air conditioners, and in aerosols.As a result CFCs have been banned in the US.As a result CFCs have been banned in the US.

Hole in the ozone layerHole in the ozone layer

Rubin, Ken. “Ask an Earth Scientist.” University ofHawaii.Oct 2008. Web. 8 Nov. 2011

The earths average global temperature has been The earths average global temperature has been steadily increasing for more than a century steadily increasing for more than a century (Global Warming)(Global Warming)

Caused by the greenhouse effect, in which greenhouse gasses Caused by the greenhouse effect, in which greenhouse gasses trap the suns energy within the atmosphere.trap the suns energy within the atmosphere.

EarthEarth’’s resources must be used responsibly.s resources must be used responsibly. Careless use of resources makes them unavailable to Careless use of resources makes them unavailable to

future generations.future generations. An ecological footprint is the amount of land An ecological footprint is the amount of land

needed to support a person.needed to support a person. The land must produce and maintain The land must produce and maintain

enoughenough food and waterfood and water sheltershelter energyenergy Room for wasteRoom for waste

Worldwide Ecological FootprintsWorldwide Ecological Footprints

Determine your ecological Determine your ecological footprintfootprint

Go to Go to www.footprintnetwork.org/calculatorwww.footprintnetwork.org/calculator to to determine how many planet Earths it would determine how many planet Earths it would take to support everyone if they lived like you.take to support everyone if they lived like you.

6.3 Biodiversity6.3 Biodiversity Biodiversity is one of EarthBiodiversity is one of Earth’’s greatest natural s greatest natural

resources. When biodiversity is lost, significant resources. When biodiversity is lost, significant value to the biosphere and to humanity may be value to the biosphere and to humanity may be lost along with it.lost along with it.

The loss of biodiversity has long-term effects.The loss of biodiversity has long-term effects. loss of medical and technological advancesloss of medical and technological advances extinction of speciesextinction of species loss of ecosystem stabilityloss of ecosystem stability

Habitat FragmentationHabitat Fragmentation

Hunting and Demand for Hunting and Demand for ProductsProducts

Introduced SpeciesIntroduced Species Introduced species can disrupt stable relationships Introduced species can disrupt stable relationships

in an ecosystem. in an ecosystem.

Burmese python in the Florida EvergladesKudzu

ConservationConservation Conservation methods can help protect and Conservation methods can help protect and

restore ecosystems.restore ecosystems. Sustainable development meets needs without Sustainable development meets needs without

hurting future generations.hurting future generations. resources meet current needsresources meet current needs resources will still be available for future useresources will still be available for future use

Sustainable practicesSustainable practices Timber industryTimber industry FisheriesFisheries

The Endangered Species ActThe Endangered Species Act Environmental Protection Agency (EPA)Environmental Protection Agency (EPA) National Park ServiceNational Park Service