Our Nutrient Cycles

SNC1PMr. MacMillan

THE WATER CYCLE

THE NITROGEN CYCLE

Nitrogen• Nitrogen (N) is an

essential component of DNA, RNA, and proteins, the building blocks of life.

• All organisms require nitrogen to live and grow.

• The majority (78%) of the Earth’s atmosphere is N2.

Have you ever started a fishtank?

Why must you wait to add a bunch of fish?

Like all living creatures, fish give off waste products (pee and poo). These nitrogenous waste products break down into ammonia (NH3), which is highly toxic to most fishes.

Human Impact of Nitrogen

• FERTILIZERS!

• Extra nitrogen fertilizer can runoff, where it contaminates surface water or infiltrates into ground water.

• In drinking water, excess nitrogen can lead to cancer in humans and respiratory distress in infants.

Human Impact• In surface waters, extra nitrogen can lead to nutrient over-

enrichment.

• This leads to – fish-kills, – harmful algal blooms, – and species shifts in

aquatic and land ecosystems.

Human ImpactSome forms of nitrogen (like

NO3- and NH4

+) can also enter the atmosphere to become:

1. smog- nitric oxide (NO)

2. Greenhouse gas- nitrous oxide (N2O)

3. Acid Rain- (nitrogen oxides)

Nitrogen Cycle PicturesGood pictures of the nitrogen cycle have these processes:

– Nitrogen fixation (N2 bonds are broken)– Nitrification (oxygen is added to form nitrogen oxides)– Denitrification (N2 is put back into the air)

It is also helpful to have– Ammonification (mineralization/waste conversion by

decomposers)– Assimilation (intake by producers)

• Yellow arrows indicate human sources of nitrogen to the environment. Red arrows indicate bacterial transformations of nitrogen. Blue arrows indicate physical forces acting on nitrogen. And green arrows indicate natural, non-microbial processes affecting the form and fate of nitrogen.

THE CARBON CYCLE

What Is Carbon?

• An element

• The basis of life of earth

• Found in rocks, oceans, atmosphere

Carbon Cycle

• The same carbon atoms are used repeatedly on earth. They cycle between the earth and the atmosphere.

Plants Use Carbon Dioxide

• Plants pull carbon dioxide from the atmosphere and use it to make food –— photosynthesis.

• The carbon becomes part of the plant (stored food).

Animals Eat Plants

• When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies.

Plants and Animal Die

• When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere.

• Some are not decomposed fully and end up in deposits underground (oil, coal, etc.).

Carbon Slowly Returns to Atmosphere

• Carbon in rocks and underground deposits is released very slowly into the atmosphere.

• This process takes many years.

The Carbon Cycle

Human Impact

• Fossil fuels release carbon stores very slowly• Burning anything releases more carbon into

atmosphere — especially fossil fuels• Increased carbon dioxide in atmosphere

increases global warming• Fewer plants mean less CO2 removed from

atmosphere

What We Need to Do

• Burn less, especially fossil fuels

• Promote plant life, especially trees

THE PHOSPHOROUS CYCLE

Phosphorus Cycle• The phosphorus cycle may also be referred to as the

mineral cycle.• The phosphorus cycle is the movement of

phosphorus from the environment to organisms and then back to the environment.

• Phosphorus is mainly found in water, soil, and rock.• Phosphorus is essential for life.– Component of DNA– Building block of our bones and teeth.

Phosphorus Cycle• Unlike the other cycles, phosphorus cannot be found

in air in the gaseous state. • The phosphorus cycle is the SLOWEST cycle.• Phosphorus is most commonly found in rock

formations and ocean sediments as phosphate salts.

Phosphorus Cycle

• Animals absorb phosphates by eating plants or plant-eating animals.

• When animals and plants die, phosphates will return to the soils or oceans again during decomposition.

Human Impacts on the Phosphorus Cycle

• Like nitrogen, increased use of fertilizers increases phosphorus runoff into our waterways and contributes to eutrophication.

REMEMBER THIS!!!• Most phosphorus is found in rocks and soil.

• The phosphorus cycle is the slowest cycle.

• Excess phosphorus contributes to eutrophication.

Reflection Questions

Take a few minutes to answer these questions:

1. Name three stages of the water cycle.2. Where is Nitrogen stored?3. Why is the carbon cycle important? How is it

cycled?4. The phosphorous cycle is also known as the

__________ cycle and is considered the ___________ cycle.