Chapter 23 Notes


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Chapter 23 Notes

  1. 1. Chapter 23 Humans and the Environment The Biodiversity Crisis
  2. 2. A Global Connection <ul><li>Convection cell- patterns of rising and falling air </li></ul><ul><li>Groups of convection cells form the system of global air circulation that helps determine climate </li></ul>
  3. 3. Upwelling <ul><li>In the southern Pacific Ocean, the usual pattern of convection cells creates a wind that blows from east to west and pushes warm surface water from South America toward Australia. </li></ul><ul><li>Along the South American coast, cold water rises from deeper in the ocean and replaces the warm water. </li></ul><ul><li>This rising current is called an upwelling and it brings with it organic material and nutrients that support an abundance of plankton. </li></ul><ul><li>The plankton in turn supports an abundance of fish. </li></ul>
  4. 4. El Nino <ul><li>The Peruvian economy along with sea birds depends on normal atmospheric conditions. </li></ul><ul><li>But sometimes, usually in December, the normal east-to-west winds do not form over the Pacific Ocean. </li></ul><ul><li>Instead, winds push warm water eastwards toward the coast of South America. </li></ul><ul><li>When these conditions occur, the warm surface water cuts off the upwelling of nutrients. </li></ul><ul><li>The event is called El Nino. </li></ul>
  5. 5. Consequences of El Nino <ul><li>The fish populations decline and Peruvian anchovy exports decrease because of the halted upwelling. </li></ul><ul><li>Fewer anchovies mean fewer birds and reduced guano population. </li></ul><ul><li>Peruvians need guano for fertilizer. </li></ul><ul><li>Northeastern Australia can suffer summer drought leading to reduced grain production there. </li></ul><ul><li>The southeastern United States gets higher rainfall in El Nino years, boosting agriculture while also decreasing forest fires. </li></ul>
  6. 7. Declining Ozone <ul><li>Ozone is a naturally occurring gas in the upper atmosphere that is vital to life on Earth. </li></ul><ul><li>Ozone protects life from deadly ultraviolet rays. </li></ul><ul><li>Humans if exposed to UV light can suffer skin cancer and cataracts. </li></ul><ul><li>Several kinds of human-made chemicals are diminishing the ozone shield. </li></ul><ul><li>A major chemical that destroys the ozone is chlorofluorocarbons or CFC’s. </li></ul><ul><li>CFC’s are used in coolants in fridges, air conditioners and in aerosol cans. </li></ul>
  7. 10. Consequences of Ozone Depletion <ul><li>Due to the ozone depletion, UV rays are negatively affected life on Earth. </li></ul><ul><li>Plants and algae are also damaged by UV rays. </li></ul><ul><li>The rise in skin cancer indicates the ozone layer is still thinning. </li></ul><ul><li>A global agreement has been reached that has cut CFC’s by 75%. </li></ul><ul><li>Hopefully, the ozone will recover within 50-100 years. </li></ul>
  8. 13. Increasing Carbon Dioxide <ul><li>Carbon dioxide or CO 2 , is a naturally occurring gas that is the raw material of photosynthesis and a byproduct of respiration. </li></ul><ul><li>It is released when fossil fuels are burned. </li></ul><ul><li>This includes, natural gas, coal and petroleum. </li></ul><ul><li>Around the middle of the 19 th century, humans began to use fossil fuels more frequently. </li></ul><ul><li>Carbon dioxide levels and global temperatures have risen as a result of the increased use of fossil fuels. </li></ul>
  9. 14. Effects of Rising CO 2 Levels <ul><li>There is a correlation or cause and effect relationship exists between global temperatures and carbon dioxide levels. </li></ul><ul><li>As carbon dioxide levels increase due to increased use of fossil fuels, global temperatures will rise causing drastic changes to our environment. </li></ul>
  10. 17. Future Population Growth <ul><li>The human population is currently just above 6 billion and growing at a rate of about 90 million per year. </li></ul><ul><li>The United Nations estimates that by the year 2050 the world’s population could be more than double. </li></ul><ul><li>How would the doubling of the human population affect the environment? </li></ul>
  11. 18. The Biodiversity Crisis <ul><li>Biodiversity- the variety of organisms in a given area; can be measured different ways </li></ul><ul><li>Evenness- the number of individuals belonging to particular species </li></ul><ul><li>Genetic diversity- amount of genetic variation </li></ul><ul><li>Genetic diversity is an important measure of biodiversity </li></ul><ul><li>Species richness is the number of different types of species. </li></ul>
  12. 19. Measuring Earth’s Biodiversity <ul><li>Biologists estimate that there are at least 10 million species on Earth and possibly as much as 30 million. </li></ul><ul><li>Mammals are actually a small portion of the Earth’s biodiversity. </li></ul><ul><li>Most species are insects, plants and crustaceans. </li></ul>
  13. 20. Reducing Biodiversity <ul><li>Biologists estimate that up to 20% of existing species may become extinct by the year 2030. </li></ul><ul><li>There have been 5 major extinctions in the past and the 6 th is currently happening. </li></ul><ul><li>The 6 th extinction is different in that it is being caused by humans instead of natural causes. </li></ul><ul><li>The greatest threat to biodiversity is destruction of habitats. </li></ul><ul><li>Since the discovery of agriculture 10,000 years ago, more than ½ of the world’s tropical rainforests have been destroyed. </li></ul><ul><li>Rainforests contain the most biodiversity so their destruction is especially damaging to the world. </li></ul>
  14. 23. Ways to Save Biodiversity <ul><li>Many countries that have tropical rainforests are some of the economically poorest nations on Earth. </li></ul><ul><li>In a process called debt-for-nature swap, richer countries or private conservation organizations pay off some of the debts of a developing country in exchange for the country to protect their biodiversity. </li></ul><ul><li>This could be setting up a preserve, launching educational programs, or promoting ecotourism. </li></ul>
  15. 24. Importance of Biodiversity <ul><li>Utilitarian value- thinking of economic benefits that biodiversity provides humans </li></ul><ul><li>Some species are valuable as sources of medicines. </li></ul><ul><li>Nonutilitarian value- life-forms have value simply because they exist apart from any human uses. </li></ul><ul><li>Many people have both reasons to preserve biodiversity. </li></ul>
  16. 25. Essential Questions <ul><li>Why is the upwelling on the coast of Peru important to that country? </li></ul><ul><li>Describe the consequences of El Nino? </li></ul><ul><li>How have CFC’s affected the atmosphere? How might this change affect humans? </li></ul><ul><li>Describe some possible effect of a continued increase in the human population. </li></ul><ul><li>Explain how species richness and evenness differ. </li></ul><ul><li>What is genetic diversity? </li></ul>