ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Review Questions and Answers		AP BIOLOGY: Chapter Twenty-Eight Outline HUMANITY VERSUS THE EARTH Effects of Human Population Visible at Great Distance fig 28.1 Population Impacts the Environment Total population of the earth in 1995 reached 5.7 billion More people consume more food, water, energy and raw materials More people create greater amount of waste A GROWING POPULATION Historical Perspective Earliest fossils from Europe are 500,000 years old Humans spread to North America 12,000 years ago Population 10,000 years ago was only 5 million With agriculture, populations rapidly expanded More dependable sources of food fig 28.2 Development of towns and cities Bubonic plague in 1348 killed nearly four-fifths of population fig 28.3 Recovery and increase to 500 million by 1650 Seventeenth century Renaissance renewed interest in science Scientific developments led to Industrial Revolution The Present Situation Global birth rate for last 300 years: 30 per year per 1000 people Present rate decreased slightly to 25 per 1000 Decreased death rate to 9 per 1000 people per year Net increase in annual population rate Population increasing at rate of 1.6% per year Will double population in 43 years Annual increase of 90 million per year Increase per minute of 170 people United Nation estimates population of 6 billion by 2000 AD Expected stabilization at 8.5 to 18 billion by 2090 Must stabilize population due to limited resources The Future Situation Localization of human populations in year 2000 60% in tropical or subtropical regions 20% in China 20% in developed or industrialized nations People in industrialized areas control 85% of wealth and materials Standard of living 20 times higher Lower infant mortality rate Higher life expectancy Variable world age structure affects population growth Industrialized nations: 20% of population under 15 years Developing countries have nearly twice as many fig 28.4 Populations of developing countries will continue to grow faster Industrialized nations will constitute smaller portion of the global population Quality of life dependent on stabilizing world`s population THE FUTURE OF AGRICULTURE Immediate World Challenge to Produce More Food Food production increased by 2.6 times since 1950 Population expanded at greater rate Most cultivatable land already in use Topsoil lost from agricultural land Consumption in developed countries increasing at greater rate Must Increase Agricultural Productivity Identify new crops, especially in tropics Major crops have been cultivated for thousands of years Few new plants cultivated since 1800 Examples: rubber and oil palms Crops selected for ease of growth Kinds of Agricultural Crops Three primary food crops: corn, wheat, rice 5000 types have ever been used for food, only 150 used regularly Various plants used for medical treatments Reasons for cultivating new plants Altered standards of cultivation Extraction of industrial products, oils, drugs, chemicals The Prospects for More Food Must increase productivity of current crops Improvement needed in tropical and subtropical regions Improvement of strains via Green Revolution: 1950-1970 Ten-fold increase in Mexican wheat production Food production in India outpaced population growth China became self-sufficient in food production Limitations of Green Revolution Agricultural techniques require great energy output Extensive use of costly pesticides and herbicides Commercial prices held low in developing areas Present solutions Improve production of current crops Not likely to bring more land into agricultural use Fully apply traditional means of plant breeding and selection fig 28.6 Include wheat, corn and rice Develop new crops in tropics and subtropics Develop improved strains via genetic engineering Resistance to specific herbicides results in better weed control Tolerance to soil conditions and mineral toxicity Ability to fix nitrogen Use of hydroponic agriculture problematic Resources of oceans are not inexhaustible Reduce over fishing of specific areas Develop new microorganism-based foods: Spirulina OUR IMPACT ON THE ENVIRONMENT Nuclear Power Chernobyl incident One of four reactors exploded in April 1986 Emergency safety systems shut off Power surge precipitated the explosion Released over 100 megatons of radioactivity Millions of times greater than Three Mile Island Significant human exposure to radiation Death due to radiation poisoning The promise of nuclear power Fossil fuels no longer cheap sources of energy Nuclear power could provide new source Undesirable side effects to burning fossil fuels Produces sulfur and carbon dioxide New problems associated with nuclear power Safe operation of power plants Disposal of radioactive wastes Safe decommission of power plants Prevention of terrorism and sabotage Important to develop other alternative energy sources Carbon Dioxide and Global Warming CO2 in atmosphere maintains world temperature 25% higher than without it Traps heat-producing infrared light Creates greenhouse effect Associated with increased energy use Most gas from burning of fossil fuels Burning of forests also increases atmospheric gas Global warming results from increased CO2 Mean global temperature increased 1% since 1900 Masked by heat-absorbing capacity of oceans Level of CO2 could double by 2035 Warming exacerbated by trace gases Include chlorofluorocarbons Absorb infrared wavelengths better than CO2 Ancillary problems Rising sea levels Altered growth rates in plants Leads to global climate change Pollution Example: Rhine river Fire in chemical warehouse washed chemicals into river Deadly mercury and pesticides killed fish and plants Water became unsafe to drink River slowly cleaned itself The Threat of Pollution Results from industrial byproducts Plastics cannot decompose Efforts being made to develop new microorganisms yet unsuccessful Water pollution Not enough water to dispose of wastes Detergents increase algae, decrease water quality Agricultural pollution Widespread use of pesticides, herbicides, fertilizers fig 28.7 Toxic chemicals remain in ecosystems Chlorinated hydrocarbons banned in U.S. Concentrate in the food chain Must develop responsible attitude toward use of chemicals Acid Precipitation Sulfur compounds produced when coal burned fig 28.8 Mixes with atmospheric water to produce sulfuric acid Acid dispersed by winds high up in atmosphere Effects seen far from where acids are produced Biological consequences Death of thousands of fresh water lakes fig 28.9 Seepage into groundwater Destruction of forests fig 28.10 Expensive to capture and remove emissions The Ozone Hole Visible to electronic equipment over Antarctica fig 28.11 Hole is nearly the size of the U.S. Thinning of ozone layer first appeared in 1975 Presence of hole coincides with Antarctic spring Cause of ozone hole attributed to chlorofluorocarbons (CFC's) Chemicals used in cooling, fire extinguishers and styrofoam CFC`s reduce O3 ozone molecule to O2 gas Global agreements to halt CFC production Problem will get worse because of quantity currently in lower atmosphere that will reach upper atmosphere in later years Biological consequences Increased ultraviolet light penetration Increases incidence of human skin cancers Damage to photosynthetic plankton Destruction in the Tropics Traditional method of shifting agriculture fig 28.12 Crops grow for only a few years in poor soils Require decades without crops to rebuild nutrients High population density does not permit renewal No longer sufficient for even traditional manioc crop Dead materials collected for firewood, not recycled Forests being cleared at too great a rate Equal to the size of Indiana per year At the present rate they will be gone in thirty years Need to change from one-use to continuous agriculture fig 28.13 The Loss of Biodiversity Serious and rapidly accelerating problem Given the loss of species of known plants and animals Given the loss of habitat, especially in tropics Calculate loss of 20% of biodiversity within in next 30 years Loss greater considering we have named only 15% of world's eukaryotic organisms Loss important for several reasons Moral, ethical and aesthetic grounds Organisms necessary to sustain our own existence Opportunity to study them lost Also lose potential benefits of these organisms Upset balance of living communities and their physical environment Effect soils, water regulation, nutrient cycles, atmosphere and climate, absorb pollution Creating conditions of instability and unproductivity Little known about overall ecology of communities and ecosystems Cannot replace with systems that will support humans Damage is currently irreparable ENVIRONMENTAL SCIENCE Attempts to Find Solutions to Environmental Problems Studied by environmental scientists Applied science associated with ecology, geology, meteorology Environmental Problems Can Be Solved fig 28.14 Assessment Gathering information Construct model of situation Use model to predict future events Risk analysis Analyze environmental impact Evaluate potential for solving problem Determine adverse effects of solution Public education Address problem in terms the public can understand Present alternative actions Explain costs and results of various choices Political action Choice made through elected officials Difficult to implement if multinational problems Follow-through Monitor results of environmental actions Evaluate and improve initial analysis and modeling WHAT BIOLOGISTS HAVE TO CONTRIBUTE Environmental Problems Require Applications of Biological Principles All living things need to use energy of the sun Need to understand basic principles and their applications Some areas of world are experiencing the future`s problems now Scientific Education Is Necessary for Informed Decision Making