Biogeochemical Cycles

• Biochemists are scientists who study the type of chemical compounds that are found in living things.

• The work of biochemists has lead to the realization that living organisms are composed of some of the same elements that are found in the air, water and soil.

• There are 92 elements know to occur naturally on Earth, however fewer than 20 elements occur in the tissues of living things.

• Only 6 elements make up 99.2% of human or pumpkin tissues.

• Table in notes: compares the relative abundance (% by weight) of a few selected elements found in the Earth's crust, human, and pumpkin.

• oxygen, carbon, hydrogen and nitrogen make up the vast majority of living tissue.

• These four elements are recycled between living organisms and the soil, water and atmosphere of the Earth.

• These elements are first taken up by plants– some oxygen is released to the atmosphere as a

product of photosynthesis, but the rest is converted into food,and passed through the food web.

– as they pass through plants, consumers, and finally decomposers, and then returned to the environment in a continuous recycling of materials.

– If recycling of these materials did not occur, life could not exist.

• Some of these elements (carbon, oxygen, sulfur, nitrogen) are found in gaseous forms and their cycles involve the atmosphere. As a result they have a global nature.

• elements may have a short term cycle such as when carbon is transferred from animals to plants in the form of carbon dioxide • and a long term cycle such as the transfer of carbon from

a fossil fuel to a plant following combustion.

• The elements are cycled between the living organisms and the environment in a combination of biological and geological processes that drives chemical recycling.

• Biological processes include:– ·         respiration, – ·         decomposition, – ·         excretion, – ·         photosynthesis, – ·         and assimilation.

• Geological processes involve» fossilization» Erosion» combustion of fossil fuels (peat, oil, coal),» weathering» formation of sedimentary rock.

Carbon Cycle

• Plants take carbon dioxide and water from their environment.

• They use the energy they capture from the sun to carry on a process known as photosynthesis which converts the atoms in the carbon dioxide and water into sugar (glucose) and oxygen.

• 6CO2 + 6H2O + energy → C6H12O6 + 6O2

 

Photosynthesis

• The oxygen, released as a byproduct of photosynthesis, generally passes into the atmosphere.

• The sugar (known as glucose) serves a • food for all consumers in the ecosystem. • The consumers carry on a metabolic process known

as cellular respiration. where oxygen is taken in from the atmosphere and used to break down the sugar resulting in a release of energy and the molecular products, carbon dioxide and water.

• Respiration chemical equation

• C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

• Notice: photosynthesis and respiration are opposite reactions.

• What is made in photosynthesis is used in respiration and what is made in respiration is used in photosynthesis…

Carbon is the center to life..

• All living things contain carbon.

• Carbon is the link that allow plants to transform sunlight into chemical energy.

• The sugar (glucose) produced during photosynthesis forms the basic substance that is transferred along food chains.

• Carbon dioxide in the atmosphere is very small, 0.03%

• However, without the carbon cycle we would quickly run out of carbon dioxide, plants could not trap

sunlight, and life on earth

would cease.

Organic and inorganic

• Organic substances always contain carbon and hydrogen, and often contain oxygen and nitrogen.

• Important chemicals that make up your body such as proteins, sugar and fats are considered organic.

• Inorganic matter doesn’t contain a combination of carbon and hydrogen.

• For example: carbon dioxide (CO2), water (H2O) and ammonia (NH3) are inorganic.

Inorganic carbon storage

• 1. Atmosphere: a small amount in the carbon dioxide in the air we breathe and is available for photosynthesis.

• 2.Ocean: a large amount is found in the oceans. This is available to algae and other water plants for phototypesets.

• 3. Earths crust: the largest storage of inorganic carbon is in the sedimentary rocks, such as limestone, that have formed from the remains of living things.

Organic Carbon Storage

• In the bodies of living organisms.

• When living things die, their bodies decompose and the carbon is returned to the cycle in inorganic form.

• Because there is limited oxygen in bogs, decomposition takes thousands of years.

• Carbon may remain locked away for many year in organic form.

• Carbon locked away in dead plants is know as peat.

• When peat is covered in sediment for a long time it will become coal, a carbon containing fossile fuel.

• Other fossil flues such as oil and gas contain organic carbon that has been trapped in the earth’s crust for millions of years.

•

Human Activity

• People have discovered these fossil fuel deposits and have used them to supply our energy needs.

• Humans have also affected the carbon cycle by cutting down forests.  As a result of human activity, the amount of carbon dioxide is being produced at a faster rate than nature can recycle it.

– As a result of this imbalance, the amount of carbon dioxide in the atmosphere is increasing. As a result the earth is presently undergoing an enhanced greenhouse effect in which the

atmosphere is gradually heating up. • If the rise in temperature occurs too fast for organisms to

adapt, widespread extinction of plants and animals may be the result.

What are the impacts of deforestation on the carbon cycle

• Removing large amounts of trees will reduce the amount of carbon dioxide that is taken out of the atmosphere due to a decreases in photosynthesis.

• If threes are burned there will be an increase of carbon dioxide released into the atmosphere.

• The forest acts as a carbon sink retaining carbon for long periods of time.

• Complete the Carbon cycle.

• Read P. 62 –64

• P. 65 Q:2, 3, 4, 5

• http://www.youtube.com/watch?v=U3SZKJVKRxQ&feature=related

• http://www.youtube.com/watch?v=1o4ODWMZq5U&feature=related

Nitrogen Cycle

Nitrogen

• Nitrogen is essential to living things for the production of proteins and DNA which are used to pass on the hereditary information from parent to offspring.

• Even though the atmosphere is about 78% nitrogen gas, plants and animals are unable to use nitrogen gas directly as a source of nitrogen to make organic nitrogen compounds.

•

• The nitrogen cycle can occur in both terrestrial and aquatic ecosystems.

Step 1: Plants change Nitrogen into….

Path 1: Nitrogen Fixation by Lightning• The electrical energy of lighting causes nitrogen

gas (N2) to react with oxygen (O2) in the atmosphere to produce nitrate ions (NO3-) which reach the soil dissolved in precipitation.

Path 2: Nitrogen Fixation by Bacteria• Bacteria in the soil can change nitrogen gas (N2)

into ammonia (NH3) which dissolves in water to form ammonium ions (NH4+)

2.Nitrification

• It is a bacterial process in which ammonium (NH4) ions are converted into nitrate ions. – They are first changed into nitrites

(NO2-) by bacteria, and then converted to Nitrates (NO3-) by a different group of bacteria.

3: Assimilation: The making of proteins for

consumer use • Assimilation is the process by

which plants use the nitrate ions (NO3-) to make amino acids, proteins, and DNA.

• Only plants and bacteria can carry out the process, all other living organisms receive their nitrogen compounds from the food they eat.

4. Ammonification • Consumers generally produce wastes

throughout their lives. When consumers die their body contain nitrogen compounds such as protein and DNA.

• Ammonification is when bacteria and some fungi break down these nitrogen compounds to make ammonia. The ammonia immediately dissolves in soil water to form ammonium ions.(NH4+)

5.Denitrification

• During this step, nitrites are changes to Nitrogen gas (N2) which returns to the atmosphere.

• It is basically the reverse of nitrogen fixation and nitrification.

• Done by bacteria!

•

Human Impact• As a result of human activities

most ecosystems have been either totally destroyed or have components such as tropic structure, energy flow and chemical cycling disrupted.

• Most effects are local or regional such as agriculture effects on nutrient cycling and introduction of toxic compounds in food chain.

http://www.youtube.com/watch?v=ronvj5ClD3Q

How may a gardener add nitrogen to the soil?

• Addition of fertilizer: manure, fish meal, crushed shells, or store purchased.

• http://www.youtube.com/watch?v=ZCogeBk92NA&feature=related

• http://www.youtube.com/watch?v=Hghru0O7dDs

1. Which represents a major storage location for organic carbon?

a. atmosphereb. lithospherec. hydrosphered. living things

2. Which process reduces the amount of carbon dioxide in the atmosphere?

a. cellular respirationb. burning of fossil fuelsc. photosynthesisd. acid deposition

3. Which step of the nitrogen cycle returns nitrogen gas to the atmosphere?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

4. Which is the most common element in the atmosphere?

a. carbonb. oxygenc. hydrogend. nitrogen

 

5. Nitrogen compounds in detritus are broken down by which bacterial process?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

6. Some plants have root nodules growing on their roots. What process do the bacteria in these root nodules carry out?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

 7. Which statement is false?

a. The carbon and nitrogen cycles have an atmospheric component.b. The nitrogen cycle depends mainly on bacterial processes.c. All living things depend on the nitrogen and carbon cycles.d. The energy stored in materials is also recycled.

1. Which represents a major storage location for organic carbon?

a. atmosphereb. lithospherec. hydrosphered. living things

2. Which process reduces the amount of carbon dioxide in the atmosphere?

a. cellular respirationb. burning of fossil fuelsc. photosynthesisd. acid deposition

3. Which step of the nitrogen cycle returns nitrogen gas to the atmosphere?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

4. Which is the most common element in the atmosphere?

a. carbonb. oxygenc. hydrogend. nitrogen

 

5. Nitrogen compounds in detritus are broken down by which bacterial process?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

6. Some plants have root nodules growing on their roots. What process do the bacteria in these root nodules carry out?

a. nitrogen fixationb. ammonificationc. denitrificationd. nitrification

 7. Which statement is false?

a. The carbon and nitrogen cycles have an atmospheric component.b. The nitrogen cycle depends mainly on bacterial processes.c. All living things depend on the nitrogen and carbon cycles.d. The energy stored in materials is also recycled.

Phosphorus cycle

Phosphorus cycle

Phosphorus cycle

• Phosphate is important for cell membranes, it helps release energy that makes up DNA and calcium in bones.

• Phosphate in rocks and fossils will weather (break down into tiny pieces).

– The inorganic phosphate dissolves in soil and rivers.

• Plants absorb phosphates and consumers receive phosphate from eating plants.

– Organic phosphate returns to the soil when decomposition occurs.

• Bones, teeth and waste, as well as river runoffs go to the ocean.– Here the Phosphate is store until there is a geological uplift.

Oxygen Cycle

Nutrient Cycles• Inorganic nutrients

(Carbon, Oxygen, Nitrogen) are recycled continually through ecosystems.

• Plants and animals build structures from nutrients and inorganic material.

Energy Flow vs. Nutrient Cycling

• Energy flows through ecosystems: it enters the ecosystem via sunlight, is stored temporarily in complex molecules, and ultimately leaves in the form of heat.

• Nutrients cycle within ecosystems: they are atoms that stay within the ecosystem and are found at different times in different pasrts of the system.

Nutrient Cycles

• Nutrients are recycled in a living system.

• The key nutrients are carbon, hydrogen Oxygen, Nitrogen and Phosphorus. These constitute 95% of all living matter

Hydrogen and Oxygen (water) cycle

Oxygen Cycle

• The complementary process of photosynthesis and respiration ensures that oxygen, carbon and hydrogen are repeatedly cycled.

Oxygen

• The Earth's atmosphere contains about 21% oxygen – As you know from the previous lesson, oxygen gas (O2) is recycled as

part of the carbon, hydrogen, and oxygen cycles. – Oxygen gas is cycled between the atmosphere and the living organisms of

both aquatic and terrestrial ecosystems. – Oxygen gas from the atmosphere is absorbed by the water in aquatic

ecosystems. – Oxygen is also produced as a byproduct of the photosynthetic organisms

that live in the aquatic ecosystems. – Heterotrophs (consumers) living in aquatic ecosystems require oxygen for

cellular respiration but they receive their oxygen from the dissolved oxygen in the water

Oxygen• During winter, ponds and lakes may

freeze.– there is little or no light and

photosynthesis ceases. • As a result, aquatic algae and plants can

no longer produce oxygen. Therefore it is possible that all fish within the lake or pond will die off.

– oxygen may be a limiting factor in aquatic ecosystems

» However Oxygen is rarely, if ever, a limiting factor in terrestrial ecosystems.