Nutrient CyclesUNIT FIVE, LESSON 5.6BY MARGIELENE D. JUDAN

LESSON OUTLINERecycling NutrientsCarbon Cycle (Oxygen to Carbon Dioxide Cycle)Nitrogen CycleWater Cycle

Nutrients are important components of living organisms. These nutrients take various forms: Water (H2O), oxygen (O2), carbon dioxide (CO2), nitrogen (N2), phosphorus (P)

But in order for them to be used again, they need to be recycled. In order to be recycled, organisms must return these nutrients to the Earth (soil).

Recycling Nutrients

1. Decomposition2. Excretion3. Perspiration and Evapotranspiration4. Respiration

1. DecompositionAs organisms die, decomposers return their nutrients to the soil to be recycled.

2. ExcretionH2O and N2 are returned to the soil through urine.P is returned to the earth in the form of feces.

3. Perspiration and EvapotranspirationWhen animals perspire, their sweat evaporates and becomes vapor.Plants release water through evapotranspiration (evaporation in plants)Vapor goes to the atmosphere (not to the soil)

4. RespirationAnimals respire by taking O2 from the environment and release CO2. (O2 CO2)Plants respire by taking CO2 to release O2. (CO2 O2)

CARBON CYCLE (O2 to CO2 Cycle) The element carbon is the present in all living organisms.

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.

3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide formed during respiration. The animals and plants eventually die.

4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.

CO2

exhale

CO2

2. Carbon dioxide is absorbed by producers to make food and oxygen via photosynthesis. Oxygen is inhaled.

O2

Via photosynthesis

3. Animals feed on the plant, passing the carbon compounds along the food chain.

4. Most of the carbon they consume is exhaled as carbon dioxide formed during respiration.

CO2

exhale

5. The animals and plants eventually die.

6. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide.

CO2

7. The cycle repeats. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

CO2

Another activity that contributes to the release of CO2 is deforestation. When trees are cut, the CO2 stored in them are released into the atmosphere. Burning of fossil fuels and deforestation are two human activities that have increased the carbon dioxide content of the atmosphere in the past hundred years.

This results in rise of atmospheric pressure. The greater the pressure, the greater the temperature. Thus, a phenomenon called global warming.

NITROGEN CYCLE Abundant in air (78% of the volume of Earth’s atmosphere). Because N2 is unreactive, it cannot be used directly by plants to make protein. Only nitrates are useful to plants, so we are dependent on other processes to convert nitrogen to nitrates in the soil.

NITROGEN CYCLE These processes are: 1. action of nitrogen-fixing bacteria 2. action lightning

NITROGEN CYCLE TERMSNitrogen fixation – process by which free nitrogen (N) in air is converted to other chemical forms usable to plantsNitrification – process of converting ammonia to nitrite, then nitrite to nitrateDenitrification – process of converting nitrate to nitrogen gas

1. Nitrogen gas is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules. Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil.

NITROGEN CYCLE Some nitrogen-fixing bacteria live free in soil and water. The most important is a bacterium called rhizobium, which inhabits the root nodules of leguminous plants – a group of soybeans, peanuts, and peas. This is a form of mutualism.

NITROGEN CYCLE The nitrogen then becomes ammonia (NH3). But still, NH3 is still unusable to most plants, so it still needs to be converted. Nitrifying bacteria do this in a process called nitrification (process of converting ammonia to nitrite, then nitrite to nitrate). Nitrogen > ammonia > nitrite > nitrate

2. Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.

3. Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia.

4. Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.

5. Higher only: In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile.

NITROGEN CYCLE The ammonia (NH3) is converted back to nitrogen by denitrifiers or denitrifying bacteria in a process called denitrification (process of converting nitrate to nitrogen gas). Lightning and other forms of combustion also play a vital role in nitrogen fixation to form nitrates. The cycle repeats.

Ammonia/nitrite/nitrate > nitrogen

NITROGEN CYCLE

Nitrogen > Ammonia > Nitrite > Nitrate >

Ammonia/Nitrite/Nitrate > Nitrogen

Nitrogen fixation Nitrification

(usable form)

(released back into the soil when an organism dies) Denitrification

Decomposition

THE WATER CYCLE Constitutes 60-96% of the weight of living things. Differs from the other cycle because here, water remains unchanged unlike in other cycles (ex. In carbon cycle, carbon takes the form of CO2)

Water Cycle Steps

1. Evaporation – liquid to gas2. Condensation – gas to liquid 3. Precipitation – water falls back to the ground either

as rain, snow, or hail

These three are the main processes of the water cycle

Water Cycle Steps

4. Surface Runoff – much of the water that return to Earth as precipitation runs off the surface of the land, and flows down hill into streams, rivers, ponds, and lakes. Small streams flow into larger streams, then into rivers, and eventually the water flows into the ocean.

Surface runoff is an important part of the water cycle because, through surface runoff, much of the water returns again to the oceans, where a great deal of evaporation occurs 

Water Cycle Steps

5. Infiltration – process where rain water soaks into the ground, through the soil and underlying rock layers, Some of this water ultimately returns to the surface at springs or in low spots downhill. Some of the water remains underground and is called groundwater. As the water infiltrates through the soil and rock layers, many of the impurities in the water are filtered out. This filtering process helps clean the water. 

Water Cycle Steps

6. Transpiration – process where plants remove water through its stomata in the leaves. This is the process of evaporation in plants (also called evapotranspiration).

THE WATER CYCLE The next slide is a picture summary of the water cycle. Try to trace the processes mentioned.

Quiz tomorrow (20 items = 25 pts)Carbon Cycle, Nitrogen Cycle, and Water Cycle; pp. 165-167Memorize especially the forms of nutrients, ways of recycling nutrients, and the 4 main steps of the Carbon Cycle.In the nitrogen cycle, understand esp. the different conversion processes (nitrogen fixation, nitrification, denitrification)Memorize esp. the 6 steps in the water cycle.

Sources:Science Links 7http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/greenworld/recyclingrev1.shtmlhttp://www.mbgnet.net/fresh/cycle/concepts.htm