Populations and the Environment Chapter 5, 6.2 and 6.3

5.1 How Populations Grow Population Density Population density is a measurement of the number of individuals living in a defined space. Population density is a measurement of the number of individuals living in a defined space. Scientists can calculate population density. Scientists can calculate population density.

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

Population Growth The size of a population is always changing. The size of a population is always changing. Four factors affect the size of a population. Four factors affect the size of a population. Immigration Immigration Births rate Births rate Emigration Emigration Death rate Death rate

Population growth is based on available resources. Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources. Exponential growth is a rapid population increase due to an abundance of resources.

Most populations are regulated by predators, disease, and the availability of resources. Most populations are regulated by predators, disease, and the availability of resources. Because of this population will not exceed the environmental carrying capacity Because of this population will not exceed the environmental carrying capacity As a population grows, limited resources become depleted and the growth of the population slows. As a population grows, limited resources become depleted and the growth of the population slows. However,

Logistic growth occurs when a population is facing limited resources. Logistic growth occurs when a population is facing limited resources. Carrying capacity is the maximum number of individuals of a particular species that a particular environment can support. Carrying capacity is the maximum number of individuals of a particular species that a particular environment can support.

5.2 Limits to Growth Limiting factors – control the growth of a population Limiting factors – control the growth of a population Density-dependent factors Density-dependent factors The rate at which they become depleted depends upon the population density of the population that uses them. The rate at which they become depleted depends upon the population density of the population that uses them. Competition Competition Predation Predation Disease Disease Overcrowding Overcrowding Herbivory Herbivory

Example: Limiting Growth

Density-independent limiting factors limit a population’s growth regardless of the size and density. Density-independent limiting factors limit a population’s growth regardless of the size and density. Hurricanes Hurricanes Drought Drought Floods Floods Wildfires Wildfires

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 Growth For most of human existence, the population grew slowly because life was harsh. Food was hard to find. Predators and diseases were common and life-threatening. These limiting factors kept human death rates very high.

Improved nutrition, sanitation, medicine, and healthcare, dramatically reduced death rates. Improved nutrition, sanitation, medicine, and 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 to exponential growth. The combination of lower death rates and high birthrates led to exponential growth.

6.2 Using Resources Wisely How do we obtain what we need from local and global environments without destroying those environments? How do we obtain what we need from local and global environments without destroying those environments? Environmental Resources we affect: Soil Soil Freshwater Freshwater Air Air

Soil Resources Healthy soil supports both agriculture and forestry. Healthy soil supports both agriculture and forestry. Topsoil – rich in organic matter and nutrients Topsoil – rich in organic matter and nutrients Loss of fertile soil can have dire consequences. Loss of fertile soil can have dire consequences. Erosion – removal of soil by water or wind Erosion – removal of soil by water or wind Desertification Desertification Deforestation Deforestation

Desertification Risk

Soil Use and Sustainablility Leaving stems and roots of the previous year’s crops Leaving stems and roots of the previous year’s crops Crop rotation Crop rotation Select Harvesting Select Harvesting

Freshwater Resources drinking water, industry, transportation, energy, and waste disposal. drinking water, industry, transportation, energy, and waste disposal. Some farmland relies heavily on irrigation Some farmland relies heavily on irrigation

Water Pollution Many serious environmental problems occur in our own backyard. Many serious environmental problems occur in our own backyard. Agriculture introduces large amounts of chemicals into the global ecosystem. Agriculture introduces large amounts of chemicals into the global ecosystem. Including: pesticides, herbicides, and fertilizers Including: pesticides, herbicides, and fertilizers Many chemicals, such as DDT, have been banned in the US, but the effects of their use still circulate. Many chemicals, such as DDT, have been banned in the US, but the effects of their use still circulate. Causes biological magnification Causes biological magnification

Water Quality and Sustainability Protecting the water cycle Protecting the water cycle Clean up pollution Clean up pollution Conserve water Conserve water

Atmospheric Resources Air quality has a direct impact on health. Air quality has a direct impact on health. Pollution Pollution Global temperature Global temperature

Coal-burning power plants send smoke, containing sulfur, into the atmosphere through smokestacks. Coal-burning power plants send smoke, containing sulfur, into the atmosphere through smokestacks. Scientists now know that the sulfur can combine with water vapor to produce sulfuric acid, which will fall back to earth as acid rain. Scientists now know that the sulfur can combine with water vapor to produce sulfuric acid, which will fall back to earth as acid rain. Acid rain causes forest damage, and dead lakes Acid rain causes forest damage, and dead lakes Robl, Ernest H. Acid Rain Damage. Photograph Web. 21 Oct 2010.

Decrease in the amount of ozone (O 3 ) in the atmosphere allows more UV radiation to reach the earth’s surface. Decrease in the amount of ozone (O 3 ) in the atmosphere allows more UV radiation to reach the earth’s surface. This can cause an increase in diseases related to UV exposure such as cancer and cataracts. This can cause an increase in diseases related to UV exposure such as cancer and cataracts. The major cause is chlorofluorocarbons (CFCs) commonly used in refrigerators, air conditioners, and in aerosols. The major cause is chlorofluorocarbons (CFCs) commonly 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 layer Rubin, Ken. “Ask an Earth Scientist.” University of Hawaii.Oct Web. 8 Nov. 2011

The earths average global temperature has been steadily increasing for more than a century (Global Warming) The earths average global temperature has been steadily increasing for more than a century (Global Warming) Caused by the greenhouse effect, in which greenhouse gasses trap the suns energy within the atmosphere. Caused by the greenhouse effect, in which greenhouse gasses trap the suns energy within the atmosphere.

Earth’s resources must be used responsibly. Earth’s resources must be used responsibly. Careless use of resources makes them unavailable to future generations. Careless use of resources makes them unavailable to future generations. An ecological footprint is the amount of land needed to support a person. An ecological footprint is the amount of land needed to support a person. The land must produce and maintain enough The land must produce and maintain enough food and water food and water shelter shelter energy energy Room for waste Room for waste

Worldwide Ecological Footprints

Determine your ecological footprint Go to to determine how many planet Earths it would take to support everyone if they lived like you. Go to to determine how many planet Earths it would take to support everyone if they lived like you.

6.3 Biodiversity Biodiversity is one of Earth’s greatest natural resources. When biodiversity is lost, significant value to the biosphere and to humanity may be lost along with it. Biodiversity is one of Earth’s greatest natural resources. When biodiversity is lost, significant value to the biosphere and to humanity may be 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 advances loss of medical and technological advances extinction of species extinction of species loss of ecosystem stability loss of ecosystem stability

Habitat Fragmentation Habitat Fragmentation

Hunting and Demand for Products

Introduced Species Introduced Species Introduced species can disrupt stable relationships in an ecosystem. Introduced species can disrupt stable relationships in an ecosystem. Burmese python in the Florida Everglades Kudzu

Conservation Conservation methods can help protect and restore ecosystems. Conservation methods can help protect and restore ecosystems. Sustainable development meets needs without hurting future generations. Sustainable development meets needs without hurting future generations. resources meet current needs resources meet current needs resources will still be available for future use resources will still be available for future use

Sustainable practices Sustainable practices Timber industry Timber industry Fisheries Fisheries The Endangered Species Act The Endangered Species Act Environmental Protection Agency (EPA) Environmental Protection Agency (EPA) National Park Service National Park Service