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Chapter 2

2.2 Nutrient Cycles in Ecosystems p.68-91

Words to Know:

cellular respiration photosynthesis

denitrification sedimentation

nitrification weathering

Nutrients

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2.2 Nutrient Cycles in Ecosystems

• Nutrients - chemicals needed for plant and animal growth.

• Nutrient cycles – the flow of nutrients IN and OUT of the land, ocean, atmosphere and deep rock.

• The health of our ecosystems depends on the balance of:•

Carbon, Nitrogen, Phosphorous, Hydrogen and Oxygen

C N P H O

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Nutrient Cycle Diagram

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Nutrient Cycles:The Carbon Cycle

• CARBON CYCLE• A. Carbon Facts

Carbon is an element found in the molecules of all living and dead things.

It is important for plant growth. Places carbon is found are called stores or sinks.

Short-term Stores Long-term Storesliving things in water and on land underground (oil, gas, natural rotting tissue of plants and animals gas and coal)atmosphere (air) sedimentary rock (limestone)ocean (dissolved in the water) ocean floor (old shells)

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B. How Carbon Changes Form

1. Photosynthesis (in plants, algae and cyanobacteria) CO2 + H2O + sunlight sunlight C6H12O6 + O2

2. Cellular respiration (in cells of all living things) C6H12O6 + O2 CO2 + H2O + ENERGY

(energy is used for growth, repair etc.)

Decomposition (rotting)

cellulose CO2

Only done by bacteria and fungi

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4. Ocean Processes:

Ocean mixing moves CO2 around the world

CO2 sinks in cold ocean waters flows to the warm equator and evaporates into the air.

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5. Combustion: (burning, engines, volcanoes, forest fires)

fossil fuels + O2 CO2 + H2O + ENERGY

(oil, gas, natural gas, coal)

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CARBON CYCLE DIAGRAM

See page 76

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Nutrient Cycles:The Carbon Cycle (continued)

C. Human Activities Have Increased CO2 in the atmosphere.

1. Burning Fossil Fuels. CO2 in atmosphere has increased 30% in past 160

years (since Industrial Revolution began). In the 160,000 years before that, it only increased 1-3%. Carbon is being removed from long-term storage more quickly

than it naturally would as we mine coal and drill for oil and gas.

CO2 is also a greenhouse gas, which traps heat in the atmosphere.

See page 77

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2. Removing Trees.

Large trees and shrubs absorb CO2 from the atmosphere, so when they are cut down, there is more CO2 in the air.

Crops that replace the trees don’t remove as much CO2

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Nutrient Cycles:The Nitrogen Cycle

Nitrogen Cycle

A. Nitrogen Facts Makes up DNA and proteins (muscle function). Help plants grow.

Where Nitrogen is Found: Atmosphere (78% is N2) Oceans Organic matter in soil Lakes, marshes, organisms

See page 78

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B. How Nitrogen Changes Form.N2 is not usable by plants or animals, so it has to be converted to

other forms.Plants can use NO3

- (nitrate) and NH4+ (ammonium)

1. Nitrogen Fixation Lightning changes N2 (nitrogen gas) NO3

- (nitrate). Rain washes nitrate into soil. This only fixes a tiny amount of nitrogen.

Bacteria in soil (rhizobium) and cyanobacteria in waterchange N2 (nitrogen gas) NH4

+ (ammonium).This processes fixes most nitrogen. Rhizobium live on the roots of legumes (peas, alfalfa, beans) and alder trees.

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Nutrient Cycles:The Nitrogen Cycle (continued)

2. Nitrification NH4

+ (ammonium) NO2- (nitrite) NO3

- (nitrate)This is done by nitrifying bacteria.

3. UptakeNO3

- is sucked into plants and used for growth.Herbivores eat the plants and use the Nitrogen for making proteins and DNA.

4. DenitrificationNO3

- N2 done by denitrifying bacteriaN2 is also returned to the atmosphere through volcanic eruptions.

See pages 78 - 79

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Nitrogen Cycle

See page 81

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Nutrient Cycles:The Nitrogen Cycle (continued)

C. Human activities affect the nitrogen cycle.The amount of nitrogen in the ecosystem has doubled in the last 50 years due to:

1. Burning fossil fuels and sewage treatment. NO and NO2 are byproducts

2. Land-clearing by burning. acid rain is formed which contains nitric acid (HNO3).

3. Overfertilization excess NH4

+ and NO3- leach into the soil and waterways.

This promotes huge growth in aquatic algae = eutrophication These algal blooms use up all CO2 and O2 and block sunlight, killing many aquatic

organisms. The algal blooms can also produce neurotoxins that poison animals.

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Nutrient Cycles:The Phosphorous Cycle

Phosphorous Cycle

A. Phosphorous Facts Phosphorous is a part of the molecule that carries energy in cells

(ATP). Phosphorous helps root growth, stem strength and seed production. In animals, phosphorous is important for strong bones.

Where Phosphorous is Found:

A. Not in atmosphere, but in phosphate rocks (PO43–, HPO4

2–, H2PO4) and sediments on the ocean floor.

See pages 83 - 84

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B. How Phosphorous Changes Form.

1. Weathering (breaking down rock into smaller pieces).

a) Chemical weathering

acid rain or lichens releases phosphates (PO43- )

b) Physical weathering

wind, water and freezing release the phosphates.

2. Uptake

plants suck up PO43- for growth, then are eaten by animals.

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3. Decomposition (rotting)

Bacteria break down dead plants and animals and phosphorous is returned to soil.

Geologic Uplift

when rocks under the ground are pushed up mountains weathering.

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The Phosphorous Cycle

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C. Human activities affect the Phosphorous Cycle.

1. Mining

Increases P in ecosystems quickly. Natural stores are not replaced.

2. Slash-and-burn forest practices.

Turns P into ash, which runs into waterways.

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How Changes in Nutrient Cycles Affect Biodiversity

To Review:

Any significant changes to any of these nutrients (C, H, O, N or P) can greatly impact biodiversity.

1. Carbon cycle changes climate change and global warming.

2. Too much nitrogen can allow certain plant species to out-compete other species.

3. Decreased levels of phosphorous slow

growth of algae (important producers).

Take the Section 2.2 Quiz