Nutrient Cycles In this presentation you will: Identify the stages of the carbon and nitrogen cycles...

Nutrient Cycles

In this presentation you will: Identify the stages of the carbon and nitrogen cycles Investigate the causes of rising carbon dioxide levels Explore the impact of the over-use of nitrogen based fertilizers

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Nutrient Cycles

Nutrient cycles summarize the movement of certain elements through ecosystems.

In this presentation you will study the carbon and nitrogen cycles. You will identify the different stages of these cycles and investigate their importance. You will also investigate how human activity can disturb the natural balance of these cycles and cause pollution.

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Nutrient Cycles

Nutrient cycles summarize the movement of certain elements through ecosystems.

Elements may be combined to form complex organic molecules. These later decompose to form simpler organic and inorganic molecules.

Nutrient Cycles

These simpler molecules can be used again to become incorporated into living things. This is called the cycling pool.

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Nutrient Cycles

Upsetting the Balance

As well as the cycling pool of an element, all cycles have a larger reservoir pool. This is usually abiotic, that is, not made up of living things.

Exchanges between the reservoir and the biotic cycling pools usually happen slowly.

Human activity often speeds up the movement of molecules through the cycles. This may upset the natural balance, cause build up of substances at one point and cause pollution.

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Nutrient Cycles

1

Which part of a nutrient cycle involves living organisms?

Question

A) The cycling pool

B) The reservoir pool

C) Both the cycling and the reservoir pool

D) Neither the cycling nor the reservoir pool

Nutrient Cycles

The Carbon Cycle – An Overview

CO2 in atmospherePhotosynthesis

Photosynthesis

Respiration

Death

C in detritus

Detrivores,Decomposers

C in humus

Animals

Combustion

CO2 in water (HCO3

- ions)

C in algae

Death

Respiration by detrivores and decomposers

Respiration Animals

Death,Excretion

Death,Excretion

Diffusion

C in detritusFossil fuels eg coal, oil

Flow of carbon in thousands of Tg/year

Tg = Terragram1 Tg = 1 million metric tons

1 metric ton = 1000kg

Rocks in the Earth

C = Carbon HCO3- = Hydrogen Carbonate

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Nutrient Cycles

There are 4 large reservoirs of carbon:the atmosphere, the oceans, limestone rocks and fossil fuels.

Photosynthesis

Photosynthesis

Respiration

Death

C in detritus


C in humus

Animals

Combustion

CO2 in water (HCO3 - ions)

C in algae

Death


Respiration Animals

Death,Excretion

Death,Excretion

Diffusion





Rocks in the Earth

CO2 in atmosphere

CO2 in water (HCO3

- ions)

Rocks in the Earth

Fossil fuels eg coal, oil Next >

Nutrient Cycles

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The processes that put carbon dioxide into the atmosphere are:respiration, combustion and diffusion.


Photosynthesis

Respiration

Death

C in detritus


C in humus

Animals

Combustion

CO2 in water (HCO3

- ions)

C in algae

Death


Respiration Animals

Death,Excretion

Death,Excretion

Diffusion





Rocks in the Earth

Respiration

Combustion

Diffusion

RespirationRespiration

Nutrient Cycles

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The processes that remove carbon dioxide from the atmosphere are:photosynthesis and diffusion.


Photosynthesis

Respiration

Death

C in detritus


C in humus

Animals

Combustion

CO2 in water (HCO3

- ions)

C in algae

Death


Respiration Animals

Death,Excretion

Death,Excretion

Diffusion



TG = Terra Ton1 Tg = 1 million metric tons


Rocks in the Earth

Photosynthesis

Diffusion

Nutrient Cycles

2

Which of the following processes does not put carbon dioxide back into the atmosphere?

Question

A) Photosynthesis

B) Combustion

C) Respiration

D) Decomposition

Nutrient Cycles

There is a balance between the carbon (in carbon dioxide) stored in the atmosphere and the amount of carbon (in hydrogen carbonate ions) stored in the sea.

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There is also a fine balance between the amount of carbon dioxide removed from the air by photosynthesis and the amount replaced by respiration.

The Carbon Dioxide Balance

Nutrient Cycles

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Despite the fact that these processes maintain a natural balance, the level of carbon dioxide in the atmosphere is still rising.

This is because the burning of fossil fuels and wood releases carbon dioxide into the atmosphere.

Upsetting the CO2 Balance

In addition to this, deforestation removes large areas of trees that would have absorbed large quantities of carbon dioxide for photosynthesis.

Nutrient Cycles

3

Why does deforestation result in increased carbon dioxide levels in the atmosphere?

Question

A) It results in fewer trees taking up nutrients from the soil

B) It results in fewer trees being burnt

C) It results in fewer trees respiring

D) It results in fewer trees photosynthesizing

Nutrient Cycles

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Around 1850, the atmosphere contained about 270ppm (parts per million) of carbon dioxide. In 2004, it contained around 360 ppm, and is rising at a rate of 1 to 2 ppm per year.

The worst possible long term effect of increasing carbon dioxide levels in the atmosphere is the 'greenhouse effect', which in turn leads to global warming.

The Greenhouse Effect and Global Warming

Time (Years)A

tmo

sp

he

ric

CO

2 l

ev

els

(p

pm

)

Nutrient Cycles

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The atmosphere is made up of 79% nitrogen. A shortage of nitrogen based compounds in ecosystems can reduce plant growth, and animal growth.

The Nitrogen Cycle – An Overview

Nutrient Cycles

The abiotic outer cycle consists of nitrogen from the air being 'fixed' by:

NO3- NH4

+

NO2-

Leaching to ground water

Bacteria

Nitrification = oxidation of ammonium to nitrate

toxic

Nitrogen fixation by lightning

Nitrogen in plantse.g. protein

Uptake of nitratesand ammonium

Nitrogen in animalse.g. Protein

Feeding

Nitrogen in detritus and humus

e.g. as protein

Microorganisms:Bacteria and fungi

Invertebrates

Nitrogen gases in atmosphere

Death andexcretion

Fertilizer manufacture(Nitrogen fixation by

Haber-Bosch process)

NO3-, NH4

+

Denitrification: denitrifying bacteria

Free-living bacteria

Bacteria in legume

root nodules

Nitrogen Fixation

lightning


and the Haber-Bosch process.



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Nutrient Cycles

Nitrogen can also be fixed by bacteria in the root nodules of legumes and by bacteria living freely in the soil.

NO3- NH4

+

NO2-


Bacteria


toxic





Feeding

Nitrogen in detritus and humus

e.g. as protein


Invertebrates


Death andexcretion





Bacteria in legume

root nodules

Nitrogen Fixation

NO3-, NH4

+

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Nutrient Cycles

Leguminous Plants

Leguminous plants are plants that produce peas or beans. They contain nodules on their roots that are full of nitrogen fixing bacteria.

Farmers often rotate crop plants with leguminous (pea or bean) plants. This is because crop plants take nitrogen from the soil and leguminous plants put nitrogen back into the soil.

Root nodule

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Nutrient Cycles

Rhizobium

One of the most common bacteria that produce nodules on legumes is Rhizobium. The relationship between the bacterium and the plant is mutualistic, that is, both organisms benefit.

The plant obtains some nitrogen from the bacterium and the bacterium obtains other nutrients, in particular, sugars, made by the plant.

Rhizobium bacterium

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Nutrient Cycles

In the central cycle, plants absorb nitrates or ammonium ions from the soil.

NO3- NH4

+

NO2-


Bacteria


toxic





Feeding

Nitrogen in detritusand humus

e.g. as protein


Invertebrates


Death andexcretion



NO3-, NH4

+



Bacteria in legume

root nodules

Nitrogen Fixation


The nitrogen forms amino acids and proteins.


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Nutrient Cycles

These compounds may or may not be eaten by animals.

NO3- NH4+


Bacteria


toxic





Feeding


e.g. as protein


Invertebrates


Death andexcretion





Bacteria in legume

root nodules

Nitrogen Fixation


However, they are all eventually turned into detritus (rotting organic matter).

Death andexcretion


e.g. as protein

NO3-, NH4

+NO2-

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Nutrient Cycles

Detritus is attacked by detrivores and decomposers.

NO3- NH4+

NO2-


Bacteria


toxic





Feeding


e.g. as protein


Invertebrates


Death andexcretion





Bacteria in legume

root nodules

Nitrogen Fixation

NH4+

Invertebrates


NO3-

The nitrogen is released as ammonium ions that are converted to nitrates.

NO3-, NH4

+NO2-

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Nutrient Cycles

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The conversion of ammonium ions to nitrites and then to nitrates is known as nitrification.

The bacteria that carry out nitrification are called nitrifying bacteria. They are chemoautotrophic, that is, they obtain their energy from oxidation of inorganic ions.

Nitrification


NO3- NH4+

Bacteria

NO2-

toxic

Nutrient Cycles

4

Nitrogen fixing bacteria put nitrogen back into the soil.

Answer True or False.

Question

Nutrient Cycles

5

Nitrification is:

Question

A) The conversion of ammonium to nitrite

B) The conversion of nitrate to nitrite

C) The conversion of ammonium to nitrate

D) The conversion of nitrite to nitrate

Nutrient Cycles

Most nitrogen-based fertilizers are made by the Haber-Bosch process. This accounts for about one third of the total nitrogen fixation each year.

Normally, natural nitrogen fixation would be balanced by denitrification. This is the process whereby bacteria take up inorganic nitrogen compounds and release nitrogen gas into the atmosphere.

However, because there is more nitrogen being put into the soil than put back into the atmosphere, by the use of fertilizers, the balance is being disrupted.

Upsetting the Nitrogen Balance

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Nutrient Cycles

6

Which of the following does not put nitrogen back into the ground?

Question

A) Lightning

B) Denitrification

C) Nitrification

D) The Haber-Bosch process

Nutrient Cycles

7

Which of the following is the most harmful way of putting nitrogen back into ecosystems?

Question

A) Lightning

B) The Haber-Bosch process

C) Nitrogen fixing bacteria

D) Death and excretion

Nutrient Cycles

Nitrogen-based fertilizers lead to a type of pollution called eutrophication. The nitrates are washed by rainfall into ground water streams. Water supplies become enriched with nitrates.

As a result of eutrophication, the algae at the water's edge grow rapidly. They prevent light from reaching aquatic plants.

Eutrophication

These plants, and the invertebrates that feed on them, then die. The algae also block water supplies, including drinking water.

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Nutrient Cycles

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When the algae die, plants and invertebrates die and they are decomposed by bacteria. These bacteria deoxygenate, that is, remove oxygen from, the water. This is known as hypoxia.

Hypoxia

The bacteria also produce hydrogen sulphide gas, which is toxic.

The fish and invertebrates that require high levels of oxygen die. This affects food webs and subsequently the entire ecosystem.

Nutrient Cycles

8

Which of the following is likely to be the best long-term solution for the problem of eutrophication?

Question

A) Re-stocking water systems with fish and invertebrates

B) Removing pond weed and algae from water systems

C) Supplying people with free bottled water

D) Reducing the use of artificial fertilizers

Nutrient Cycles

Summary

Identify the stages of the nitrogen cycle

After completing this presentation you should be able to:

Identify the stages of the carbon cycle

Show knowledge of the causes of increasing carbon dioxide levels

Show knowledge and understanding of the consequences of the over-use of nitrogen based fertilizers

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Nutrient Cycles In this presentation you will: Identify the stages of the carbon and nitrogen cycles...

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Transcript of Nutrient Cycles In this presentation you will: Identify the stages of the carbon and nitrogen cycles...