Chapter 23 Notes
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    Chapter 23 Notes Chapter 23 Notes Presentation Transcript

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