Populations and the Environment

1. Populations and the Environment Chapter 5, 6.2 and 6.3

2. 5.1 How Populations Grow Population Density Population density is a measurement of the number of individuals living in a defined space. Scientists can calculate population density.

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

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

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

6. Most populations are regulated by predators, disease, and the availability of resources. 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. However,

7. 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.

8. 5.2 Limits to Growth • Limiting factors – control the growth of a population • Density-dependent factors • The rate at which they become depleted depends upon the population density of the population that uses them. • Competition • Predation • Disease • Overcrowding • Herbivory

9. Example: Limiting Growth

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

11. During which time period is birth rate higher than death rate? • During which time period are birth rate and death rate equal? • During which time period is death rate higher than birth rate?

12. 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.

13. Improved nutrition, sanitation, medicine, and healthcare, dramatically reduced death rates. • birthrates in most parts of the world remained high. • The combination of lower death rates and high birthrates led to exponential growth.

14. 6.2 Using Resources Wisely • How do we obtain what we need from local and global environments without destroying those environments? Environmental Resources we affect: • Soil • Freshwater • Air

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

16. Desertification Risk

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

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

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

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

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

23. 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. Acid rain causes forest damage, and dead lakes Robl, Ernest H. Acid Rain Damage. Photograph 1990. Web. 21 Oct 2010.

24. Decrease in the amount of ozone (O3) 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. 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.

25. Hole in the ozone layer Rubin, Ken. “Ask an Earth Scientist.” University of Hawaii.Oct 2008. Web. 8 Nov. 2011

26. 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.

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

29. Worldwide Ecological Footprints

30. Determine your ecological footprint • Go to www.footprintnetwork.org/calculator to determine how many planet Earths it would take to support everyone if they lived like you.

31. 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.

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

33. Habitat Fragmentation

34. Hunting and Demand for Products

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

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

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