1. 2.2 Nutrient Cycles in Ecosystems p.68-91
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. 2.2 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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3. Nutrient Cycle Diagram
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4. Nutrient Cycles: The 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 Stores
living 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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5. How Carbon Changes Form
1. Photosynthesis (in plants, algae and cyanobacteria)
CO2 + H2O + 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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6. Ocean mixing moves CO2 around the world
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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7. Combustion: (burning, engines, volcanoes, forest fires)
fossil fuels + O2  CO2 + H2O + ENERGY
(oil, gas, natural gas, coal)
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8. CARBON CYCLE DIAGRAM
See page 76
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9. Nutrient Cycles: The Carbon Cycle (continued)
Human Activities Have Increased CO2 in the atmosphere.
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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10. Crops that replace the trees don’t remove as much CO2
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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11. Nutrient Cycles: The Nitrogen Cycle
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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12. 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)
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 water
change 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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13. Nutrient Cycles: The Nitrogen Cycle (continued)
Nitrification
NH4+ (ammonium)  NO2- (nitrite)  NO3- (nitrate)
This is done by nitrifying bacteria.
Uptake
NO3- is sucked into plants and used for growth.
Herbivores eat the plants and use the Nitrogen for making proteins and DNA.
Denitrification
NO3-  N2 done by denitrifying bacteria
N2 is also returned to the atmosphere through volcanic eruptions.
See pages
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14. Nitrogen Cycle
See page 81
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15. Nutrient Cycles: The Nitrogen Cycle (continued)
Human activities affect the nitrogen cycle.
The amount of nitrogen in the ecosystem has doubled in the last 50 years due to:
Burning fossil fuels and sewage treatment.
NO and NO2 are byproducts
Land-clearing by burning.
acid rain is formed which contains nitric acid (HNO3).
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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16. Nutrient Cycles: The Phosphorous Cycle
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:
Not in atmosphere, but in phosphate rocks (PO43–, HPO42–, H2PO4) and sediments on the ocean floor.
See pages
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17. 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.
Uptake
plants suck up PO43- for growth, then are eaten by animals.
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18. 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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19. The Phosphorous Cycle
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20. 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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21. 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.
Carbon cycle changes  climate change and global warming.
Too much nitrogen can allow certain plant species to out-compete other species.
Decreased levels of phosphorous  slow
growth of algae (important producers).
Take the Section 2.2 Quiz
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