Chapter 23 Global Ecology and Human Interferences

Points to Ponder What is an ecosystem and what are its biotic components? What are the energy flow and chemical cycling in an ecosystem? What are the two major ecosystems on earth? Describe the 3 types of terrestrial ecosystems and the 2 types of aquatic ecosystems. Compare and contrast food webs and food pyramids. What is a biogeochemical cycle? What is a reservoir and an exchange pool. Explain the water, carbon, nitrogen and phosphorus cycles. What human activities interfere with these cycles? What problems are we creating by altering these pathways? What is ozone depletion and why is this important? What are the pros and cons to drilling in the Arctic National Wildlife refuge?

The nature of ecosystems Biosphere – the regions of the Earth’s waters, crust and atmosphere inhabited by living organisms Ecosystem – a place where organisms interact between each other and their environment Terrestrial: several distinct types based on temperature and waterfall Aquatic: freshwater and marine

Terrestrial ecosystems 23.1 The nature of ecosystems Terrestrial ecosystems Forests – dominated by trees Tropical rain forest Coniferous forests (taiga) Temperate deciduous forests Grasslands – dominated by grass Tropical grasslands Temperate grasslands (prairie) Deserts – characterized by lack of available moisture Tundra Deserts

Terrestrial ecosystems 23.1 The nature of ecosystems Terrestrial ecosystems

Aquatic ecosystems Marine Freshwater Seashores Oceans Coral reefs 23.1 The nature of ecosystems Aquatic ecosystems Marine Seashores Oceans Coral reefs Estuaries Freshwater Lakes Ponds Rivers Streams

23.1 The nature of ecosystems Aquatic ecosystems

Components of an ecosystem 23.1 The nature of ecosystems Components of an ecosystem Abiotic components – nonliving environment Biotic components - living components Autotrophs – producers Heterotrophs – consumers Herbivores – feed on plant and algae Carnivores – feed on other animals Omnivores – eat both plants and animals Detritus feeders – feed on decomposing organic matter Niche – the role an organism plays in an ecosystem such as how it gets its food, what it eats and how it interacts with other organisms

Biotic components of an ecosystem 23.1 The nature of ecosystems Biotic components of an ecosystem

Energy flow and chemical cycling 23.1 The nature of ecosystems Energy flow and chemical cycling Energy flow: Begins and continues when producers absorb solar energy Occurs as nutrients pass from one population to another This energy is converted to heat that dissipates into the environment Only a portion of energy is passed to organisms as they consume one another Chemical cycling: Inorganic nutrients are returned to producers from the atmosphere or soil Chemicals recycle within and between ecosystems

Energy flow and chemical cycling 23.1 The nature of ecosystems Energy flow and chemical cycling

Energy flow Food web – describes who eats whom Grazing food web Detrital food web Trophic levels – composed of all organisms that feed at a particular link in the food chain Producers, primary consumers and secondary consumers Ecological pyramid – reflects the loss of energy from one trophic level to another Only about 10% of the energy of one trophic level is available to the next trophic level

23.2 Energy flow Food webs

An example of a food pyramid 23.2 Energy flow An example of a food pyramid

Biogeochemical cycles 23.3 Global Biogeochemical cycles Biogeochemical cycles Biogeochemical cycles are pathways by which chemicals circulate through an ecosystem including both living and nonliving components Water cycle Carbon cycle Nitrogen cycle Phosphorus cycle Reservoir – fossil fuels, minerals in rocks and sediment in oceans that contain inorganic nutrients that are limited in availability Exchange pools – atmosphere, soil and water that are ready sources of inorganic nutrients

Biogeochemical cycles 23.3 Global Biogeochemical cycles Biogeochemical cycles

23.3 Global Biogeochemical cycles Water cycle Water evaporates from the bodies of water, land and plants and returns when water falls on land to enter the ground, surface waters or aquifers Human activities that interfere: Withdraw water from aquifers Clear vegetation from the land and build structures that prevent percolation and increase runoff Add pollutants to water such as sewage and chemicals

23.3 Global Biogeochemical cycles Water cycle

23.3 Global Biogeochemical cycles Carbon cycle CO2 is exchanged between the atmosphere and living organisms Plants incorporate atmospheric CO2 into nutrients through photosynthesis that can be used by living organisms CO2 is returned to the atmosphere through respiration

23.3 Global Biogeochemical cycles Carbon cycle

Carbon cycle Human activities that interfere: 23.3 Global Biogeochemical cycles Carbon cycle Human activities that interfere: Burning of fossil fuels and the destruction of forests are depositing CO2 to the atmosphere faster than it is being removed CO2 and other gases (N2O and CH4) are being emitted due to human activities These gases are called greenhouse gases because they trap heat that contributes to global warming

Greenhouse gases and global warming 23.3 Global Biogeochemical cycles Greenhouse gases and global warming

23.3 Global Biogeochemical cycles Nitrogen cycle 78% of the atmosphere is nitrogen gas but it is not in a usable form by plants Nitrogen-fixing bacteria convert nitrogen gas to ammonium that can be used by plants Nitrifying bacteria convert ammonium to nitrate Bacteria convert nitrate back to nitrogen gas through a process called dentrification

23.3 Global Biogeochemical cycles Nitrogen cycle

Nitrogen cycle Human activities interfere: 23.3 Global Biogeochemical cycles Nitrogen cycle Human activities interfere: We add nitrogen fertilizers that run off into lakes and streams that causes major fish kills by eutrophication Burning of fossil fuels puts nitrogen oxides and sulfur dioxide into the atmosphere where they combine with water vapor to form acids that return to earth as acid deposition Result in nitrogen oxides and hydrocarbons that react with one another to produce smog

23.3 Global Biogeochemical cycles Nitrogen cycle

23.3 Global Biogeochemical cycles Phosphorus cycle Phosphate ions become available to living organisms by the slow weathering of rocks Phosphate is a limiting nutrient in ecosystems

Phosphorus cycle Human activities interfere: 23.3 Global Biogeochemical cycles Phosphorus cycle Human activities interfere: Runoff of phosphate due to fertilizer and discharge from sewage treatment plants results in eutrophication Sources of pollution: Point source – specific sources Nonpoint sources – runoff from land

23.3 Global Biogeochemical cycles Sources of pollution

Science focus: ozone depletion 23.3 Global Biogeochemical cycles Science focus: ozone depletion Ozone shield – a layer of ozone in the stratosphere that absorbs UV rays preventing them from reaching the earth Causes of depletion: Chlorine atoms primarily from chlorofluorocarbons(CFCs) Freon used as a coolant Cleaning agents Agents used to make Styrofoam Concerns about loss of ozone: Increases mutations leading to skin cancer Adversely affects the immune system Impairs crop and tree growth Can kill off algae and krill that sustain oceanic life

Bioethical focus: Oil drilling in the Arctic 23.3 Global Biogeochemical cycles Bioethical focus: Oil drilling in the Arctic Should we drill for oil in the Arctic National Wildlife refuge to alleviate the dependence of the US on foreign oil? Those for drilling: Yield of a million barrels of oil per day over 20 yrs. Would affect only a small portion of the Arctic National Wildlife Refuge New techniques would limit the damage Increase in Alaskan job and economy Those against drilling: We should focus on reducing our need for oil A modest increase in vehicle fuel efficiency could save more oil than would be gained by drilling Drilling would not alleviate our needs for oil based on our use Drilling sites are scattered so roads and such would disrupt even more land There has been an oil spill from a nearby pipeline so we still have to consider pollution even with newer drilling methods