ecosystems 1.energy flow 2. chemical cycles water, carbon, nitrogen 3. human effects on cycles...

Ecosystems

1.Energy Flow

2. Chemical cycleswater, carbon, nitrogen

3. Human effects on cycleseutrophication, 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


•A terrarium ecosystem / Biosphere II

Figure 36.8

Chemical cycling(C, N, etc.)

Lightenergy

Chemicalenergy

Heatenergy


– Water cycle

- Carbon cycle

– Nitrogen cycle

Chemicals are recycled between organic matter and abiotic reservoirs


Figure 36.14

Solarheat

Precipitationover the sea(283)

Net movementof water vaporby wind (36)

Flow of waterfrom land to sea(36)

Water vaporover the sea

Oceans

Evaporationfrom the sea(319)

Evaporationandtranspiration(59)

Water vaporover the land

Precipitationover the land(95)

Surface waterand groundwater

oceans

salt water = 97.5%

freshwater = 2.5%

ice capsand

glaciers1.97%

ground-water0.5%

lakes,rivers,and soil0.03%

atmosphere0.001%


• Carbon is taken from the atmosphere by photosynthesis

– used to make organic molecules

returned to the atmosphere by cellular respiration, decomposers

Carbon cycle


Figure 36.15

CO2 in atmosphere

Cellular respiration

Higher-levelconsumers

Primaryconsumers

Plants,algae,

cyanobacteria

Photosynthesis

Wood andfossil fuels

Detritivores(soil microbes

and others) Detritus

Decomposition

Burning


• Nitrogen is plentiful in the atmosphere as N2

– But plants and animals cannot use N2

• Some bacteria in soil and legume root nodules convert N2 to compounds that plants can use:

ammonium (NH4+) and nitrate (NO3

–)

The nitrogen cycle relies heavily on bacteria


• 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


Figure 32.13

ATMOSPHERE

N2

N2Nitrogen-fixing

bacteria

Ammonifyingbacteria

Organicmaterial

NH4+

(ammonium) Nitrifyingbacteria

NO3–

(nitrate)

Root

NH4+

Aminoacids

Soil


Nitrogen (N2) in atmosphere

Amino acidsand proteins in

plants and animalsAssimilationby plants

Denitrifyingbacteria

Nitrates(NO3

–)

Nitrifyingbacteria

Detritus

Detritivores

Decomposition

Ammonium (NH4+)

Nitrogenfixation

Nitrogen-fixingbacteria in soil

Nitrogen-fixingbacteria in root

nodules of legumes

Nitrogenfixation

76%naturallyoccurring

24%naturallyoccurring

24%human-caused

58%human-caused

46%available

54%used

AtmosphericCO2concentration

Terrestrialnitrogenfixation

Accessiblesurfacewater

Human impact on chemical cycles


• 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.

eutrophication• Algal bloom can cause a lake to lose its species diversity


– 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


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

ecosystems 1.energy flow 2. chemical cycles water, carbon, nitrogen 3. human effects on cycles...

Documents

pearson education

benjamin cummings nitrogen

soil nitrogen

benjamin cummings figure

nitrogen fixation nitrogen

bacteria figure

benjamin cummings carbon

benjamin cummings legumes