Ecosystems 1.Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles eutrophication, acid rain

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ecosystem = community plus abiotic factors - Conditions (temp, light) Resources (water, nutrients) Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat Chemicals are recycled between air, water, soil, and organisms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A terrarium ecosystem / Biosphere II Figure 36.8 Chemical cycling (C, N, etc.) Light energy Chemical energy Heat energy

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Tertiary and secondary consumers Secondary and primary consumers Primary consumers Producers (Plants, algae, phytoplankton) Detritivores (Prokaryotes, fungi, certain animals) Wastes and dead organisms Food webs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chemicals are concentrated in food chains by biological magnification Figure 38.3B DDT in water ppm DDT in zooplankton 0.04 ppm DDT in small fish 0.5 ppm DDT in large fish 2 ppm DDT in fish-eating birds 25 ppm DDT concentration: increase of 10 million times

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Food chains/webs reveal the flow of energy 170 billion tons of biomass per year Figure Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal 1,000,000 kcal of sunlight Energy supply limits the length of food chains Avg. 10% conversion of biomass to next level Endothermic animals convert only 2% Plants convert 30-85%

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Consequences: Low density of large carnivores a field of corn can support more vegetarians than carnivores. Figure Secondary consumers Primary consumers Producers Human vegetarians Corn Human meat-eaters Cattle Corn TROPHIC LEVEL

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Water cycle - Carbon cycle –Nitrogen cycle Chemicals are recycled between organic matter and abiotic reservoirs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure Solar heat Precipitation over the sea (283) Net movement of water vapor by wind (36) Flow of water from land to sea (36) Water vapor over the sea Oceans Evaporation from the sea (319) Evaporation and transpiration (59) Water vapor over the land Precipitation over the land (95) Surface water and groundwater

oceans salt water = 97.5% freshwater = 2.5% ice caps and glaciers 1.97% ground- water 0.5% lakes, rivers, and soil 0.03% atmosphere 0.001%

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbon is taken from the atmosphere by photosynthesis –used to make organic molecules returned to the atmosphere by cellular respiration, decomposers Carbon cycle

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure CO 2 in atmosphere Cellular respiration Higher-level consumers Primary consumers Plants, algae, cyanobacteria Photosynthesis Wood and fossil fuels Detritivores (soil microbes and others) Detritus Decomposition Burning

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen is plentiful in the atmosphere as N 2 –But plants and animals cannot use N 2 Some bacteria in soil and legume root nodules convert N 2 to compounds that plants can use: ammonium (NH 4 + ) and nitrate (NO 3 – ) The nitrogen cycle relies heavily on bacteria

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen (N 2 ) in atmosphere Amino acids and proteins in plants and animals Assimilation by plants Denitrifying bacteria Nitrates (NO 3 – ) Nitrifying bacteria Detritus Detritivores Decomposition Ammonium (NH 4 + ) Nitrogen fixation Nitrogen-fixing bacteria in soil Nitrogen-fixing bacteria in root nodules of legumes Nitrogen fixation

76% naturally occurring 24% naturally occurring 24% human- caused 58% human- caused 46% available 54% used Atmospheric CO 2 concentration Terrestrial nitrogen fixation Accessible surface water Human impact on chemical cycles

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Environmental changes caused by humans can unbalance nutrient cycling over the long term –Example: acid rain –Sulfur dioxide, nitrogen oxides create strong acids when dissolved in rain water. –Low pH kills aquatic life, leaches nutrients from soil –Calcium deficiency affects everything in food chain: plants, insects, birds. Weak egg shells.

eutrophicationAlgal bloom can cause a lake to lose its species diversity

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s Figure 36.19B –classic experiments on eutrophication led to the ban on phosphates in detergents

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings What are the limits to human alteration of chemical cycles and habitats? What should the limits be? How do we set priorities for what we value in the natural world? Aesthetic, economic, conservation, humans