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

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Presentation on theme: "Ecosystems 1.Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles eutrophication, acid rain."— Presentation transcript:

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

3 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

4 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

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

6 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

7 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%

8 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

9 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

10 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

11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Legumes and certain other plants have nodules in their roots that contain nitrogen-fixing bacteria Legumes and certain other plants house nitrogen- fixing bacteria Figure 32.14A Shoot Nodules Roots

12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure ATMOSPHERE N2N2 N2N2 Nitrogen-fixing bacteria Ammonifying bacteria Organic material NH 4 + (ammonium) Nitrifying bacteria NO 3 – (nitrate) Root NH 4 + Amino acids Soil

13 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

14 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

15 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.

16 eutrophicationAlgal bloom can cause a lake to lose its species diversity

17 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

18 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


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