CYCLES OF THE CYCLES OF THE ENVIRONMENTENVIRONMENT

4 CYCLES THAT MAINTAIN 4 CYCLES THAT MAINTAIN HOMEOSTASIS IN THE ENVIRONMENTHOMEOSTASIS IN THE ENVIRONMENT

Our Environment’s Our Environment’s HomeostasisHomeostasis

Atoms of carbon, hydrogen, nitrogen, Atoms of carbon, hydrogen, nitrogen, oxygen and phosphorous make up living oxygen and phosphorous make up living

organisms (CHNOPS)organisms (CHNOPS)

This matter AND energy recycles This matter AND energy recycles through ecosystems.through ecosystems.

Matter & Energy Matter & Energy Transfer through Transfer through EnvironmentEnvironmentFood ChainFood Chain Food WebFood Web

Cycling Maintains Cycling Maintains HomeostasisHomeostasis

Food chains, food webs and energy pyramids Food chains, food webs and energy pyramids → → energy gained or used in one direction in energy gained or used in one direction in ecosystem.ecosystem.

Matter, in form of nutrients, moves through Matter, in form of nutrients, moves through org. at each org. at each trophic trophic level.level.

Trophic Levels Trophic Levels include: producer, lst order include: producer, lst order consumer, 2consumer, 2ndnd order consumer… order consumer…

Food Chain & Energy Food Chain & Energy PyramidPyramid

Food ChainFood Chain Energy PyramidEnergy Pyramid

Producer

Primary-1st

Secondary-2nd

Tertiary-3rd

Quaternary-4th

Energy Flow in an EcosystemEnergy Flow in an Ecosystem

Each step in a food Each step in a food

chain represents a chain represents a transfer of energy & transfer of energy & materials.materials.

•Energy is lost at each Energy is lost at each level = only 10% is level = only 10% is transferred to next transferred to next trophic level.trophic level.

Energy Loss at Trophic LevelsEnergy Loss at Trophic Levels

90% of Energy is used 90% of Energy is used by the organism for:by the organism for:

Breathing /RespiratonBreathing /Respiraton ReproductionReproduction HomeostasisHomeostasis Movement/Interaction Movement/Interaction

with other orgs.with other orgs.

4 Cycles of an 4 Cycles of an EnvironmentEnvironment

They include:They include:

1.1. Water CycleWater Cycle

2.2. Carbon CycleCarbon Cycle

3.3. Nitrogen CycleNitrogen Cycle

4.4. Phosphorous CyclePhosphorous Cycle

Water Cycle Water Cycle 3 states of Matter3 states of Matter

1. liquid (water or 1. liquid (water or precipitation),precipitation),

2. solid (ice, snow)2. solid (ice, snow)

3. Gas (atmosphere) 3. Gas (atmosphere)

WATER CYCLEWATER CYCLE

Water Cycle FlowWater Cycle Flow

1.1. Water begins cycle through ecosystem Water begins cycle through ecosystem when plants absorb water through when plants absorb water through roots. roots.

2.2. Animals drink water or get it indirectly Animals drink water or get it indirectly w/food they consume.w/food they consume.

3.3. Animals and plants respire giving off Animals and plants respire giving off water vapor (Transpiration).water vapor (Transpiration).

Water cycle (continued)Water cycle (continued)

4.4. Organisms lose water through Organisms lose water through excretion.excretion.

5.5. Water (liquid, solid or gas) recycles into Water (liquid, solid or gas) recycles into lakes, streams, rivers, oceans via thelakes, streams, rivers, oceans via the

groundwater.groundwater.

Carbon cycleCarbon cycle

1. Carbon found in environment as a gas1. Carbon found in environment as a gas

(CO(CO22) in atmosphere and oceans.) in atmosphere and oceans.

2. CO2. CO2 2 moves to water and plants.moves to water and plants.

3.3. Photosynthesis is major player in CC.Photosynthesis is major player in CC. a. P.S. combines carbon dioxide and water.a. P.S. combines carbon dioxide and water.

b. P.S. changes molecules fr low energy to b. P.S. changes molecules fr low energy to high energy.high energy.

CARBON CYCLECARBON CYCLE

4.4. Org. obtain carbon when they consume Org. obtain carbon when they consume producers or other consumers.producers or other consumers.

5.5. Respiration and decay return carbon to Respiration and decay return carbon to the atmosphere (gas).the atmosphere (gas).

6.6. Carbon also returns to atmosphere in Carbon also returns to atmosphere in large amounts as COlarge amounts as CO2 2 when fossil fuels when fossil fuels

are burned.are burned.

Carbon CycleCarbon Cycle

Nitrogen Cycle - LandNitrogen Cycle - Land

1.1. N2 makes up 78% N2 makes up 78% of air.of air.

2.2. Living things cannot Living things cannot use Nitrogen in use Nitrogen in

atmospheric form.atmospheric form.

Nitrogen moves through Nitrogen moves through the food web.the food web.

Nitrogen cycles as Nitrogen cycles as matter and energy matter and energy transfer through the transfer through the food web.food web.

Nitrogen Fixation Nitrogen Fixation MethodsMethodsConversion of atmospheric N2 into reactive Conversion of atmospheric N2 into reactive compounds such as:compounds such as:

1.1.Biological FixationBiological Fixation

2.2.Abiotic FixationAbiotic Fixation

3.3.DenitrificationDenitrification

4.4.AssimilationAssimilation

5.5.NitrificationNitrification

6.6.AmmonificationAmmonification

Nitrogen Forms =

BADANA

Nitrogen CompoundsNitrogen Compounds

N2 – NitrogenN2 – Nitrogen NO2 – nitrogen oxide or nitriteNO2 – nitrogen oxide or nitrite NO3-Nitrous oxide or nitrateNO3-Nitrous oxide or nitrate NH3 – AmmoniaNH3 – Ammonia NH4 - AmmoniumNH4 - Ammonium

Nitrogen CyclesNitrogen Cycles

1. Abiotic Fixation1. Abiotic Fixation

a.a. High energy fixation w/ lightning & High energy fixation w/ lightning & cosmic radiation. Accounts for 10% of cosmic radiation. Accounts for 10% of nitrate in N2 cycle. Occurs when…nitrate in N2 cycle. Occurs when…

1. N2 combines w/O2 to form nitrogen 1. N2 combines w/O2 to form nitrogen oxides such as NO and NO2oxides such as NO and NO2

2. Carried to Earth’s surface in rainfall as2. Carried to Earth’s surface in rainfall as

nitric acid (HNO3 or acid rain).nitric acid (HNO3 or acid rain).

Legumes…you say?Legumes…you say?

A legume is any of the thousands of plant A legume is any of the thousands of plant species in the legume family, species in the legume family, Leguminosae.Leguminosae.

Legumes have seed pods that, when Legumes have seed pods that, when ripe, split along both sides. ripe, split along both sides.

2. Biological Fixation2. Biological Fixation

a.a. Completed by living orgs such asCompleted by living orgs such as

soil aerobic bacteria (needs O2) and soil aerobic bacteria (needs O2) and anaerobic bacteria (chemosynthesis w/o anaerobic bacteria (chemosynthesis w/o O2).O2).

b. Symbiotic bacteria (Rhizobium) found in b. Symbiotic bacteria (Rhizobium) found in roots of legumes such as clover, alfalfa, roots of legumes such as clover, alfalfa, soy beans and chick peas assists in bio soy beans and chick peas assists in bio fix.fix.

Soybeans and ChickpeasSoybeans and Chickpeas

Chick PeasChick Peas Soy BeansSoy Beans

2. Biological Fixation 2. Biological Fixation (cont)(cont)

c.c. How does this happen?How does this happen?

c1. Roots of legumes, bacteria split the c1. Roots of legumes, bacteria split the nitrogen atoms into two free nitrogen nitrogen atoms into two free nitrogen atoms which combine with hydrogen to atoms which combine with hydrogen to form ammonia, NH3. form ammonia, NH3.

c2. Any excess nitrogen leftover from c2. Any excess nitrogen leftover from ammonification (NH3) not used by the ammonification (NH3) not used by the plant are returned to the soil. plant are returned to the soil.

2. Biological Fixation 2. Biological Fixation (Cont)(Cont)

d.d. Some bacteria freely fix nitrogen, without Some bacteria freely fix nitrogen, without splitting the N2 atom, in soil such as:splitting the N2 atom, in soil such as:

1. Aerobic bacteria, 1. Aerobic bacteria, Azotobacter Azotobacter

2. 2. Anaerobic bacteria, Anaerobic bacteria, ClostridiumClostridium

3. 3. PhotosyntheticPhotosynthetic Cyanobacterium Cyanobacterium fix fix

nitrogen in aquatic environments.nitrogen in aquatic environments.

Major agricultural crops produced in the United States in 2000 (excluding root crops, citrus, vegetable, etc).

CropHarvested Area (million acres)

Cash Receipts from Sales ($ billion)

Corn (grain)

72.7 15.1

Soy-beans

72.7 12.5

Hay 59.9 3.4

Wheat 53.0 5.5

Cotton 13.1 4.6

Sorghum (grain)

7.7 0.82

Rice 3.0 1.2

2. FYI: Benefits of N2 2. FYI: Benefits of N2 FixFix

Since its introduction into Nigeria in 1908, Since its introduction into Nigeria in 1908, soybean (soybean (Glycine maxGlycine max. (L) Merrill) has . (L) Merrill) has been grown primarily as a sole crop been grown primarily as a sole crop (Ogunwolu, 1991) yet it has been shown (Ogunwolu, 1991) yet it has been shown to be able to fix atmospheric nitrogen up to be able to fix atmospheric nitrogen up to 417 kg N ha-1to 417 kg N ha-1

(LaRue and Patterson, 1981)(LaRue and Patterson, 1981)

2. Biological Fixation 2. Biological Fixation (cont)(cont)

d.d. To promote sustainable soil fertility, it is To promote sustainable soil fertility, it is beneficial to use these legume crops beneficial to use these legume crops w/other plants such as corn. w/other plants such as corn.

e.e. Corn depletes the available N2 in soil Corn depletes the available N2 in soil quicklyquickly. .

3. Nitrification3. Nitrification

Nitrification is a process of nitrogen compound oxidation (effectively, loss of electrons from the nitrogen atom to the oxygen atoms)…see next 2 slides—caused by Bacteria.

Nitrifying BacteriaNitrifying Bacteria

3. Nitrification3. Nitrification

NH3 is oxidized to nitrite ions (NO2¯) and NH3 is oxidized to nitrite ions (NO2¯) and then to nitrate ions (NO3¯).then to nitrate ions (NO3¯).

Bacteria, Bacteria, Nitrosomas. Nitrosomas. oxidizes NH3 to oxidizes NH3 to NO2. NO2.

((NH3 + 1.5 O2 + Nitrosomonas → NO2- +

H2O + H)

NO2- + 0.5 O2 + Nitrobacter → NO3

-

3. Nitrification3. Nitrification

Bacteria, Bacteria, Nitrobacter,Nitrobacter, oxidizes NH3 to oxidizes NH3 to NO3. NO3.

NH3 + O2 → NO2− + 3H+ + 2e−

NO2− + H2O → NO3

− + 2H+ + 2e−

4. Assimilation-Plants4. Assimilation-Plants

a.a. Nitrates (NO3¯) are Nitrates (NO3¯) are commonly commonly assimilated (taken assimilated (taken in/absorbed) by in/absorbed) by plants through their plants through their root hairs. root hairs.

4. Assimilation-4. Assimilation-HeterotrophsHeterotrophs

b. Heterotrophicb. Heterotrophic organisms cannot organisms cannot readily absorb N2 as readily absorb N2 as plants do, so N2 is plants do, so N2 is acquired through acquired through foods they/we eat. foods they/we eat.

4. Assimilation (cont)4. Assimilation (cont)

c. Plants are base of c. Plants are base of food chain.food chain.

d. N2 is already d. N2 is already assimilated into their assimilated into their tissue & will continue to tissue & will continue to pass from one pass from one organism to another. organism to another.

Food Chain

5. Ammonification5. Ammonification

a. Host of decomposing a. Host of decomposing microorganisms such as microorganisms such as bacteria & fungi breaks bacteria & fungi breaks down nitrogenous wastes & down nitrogenous wastes & organic matter found in organic matter found in animals and dead plants.animals and dead plants.

b. It is converted to b. It is converted to inorganic NH3 for inorganic NH3 for absorption by plants as absorption by plants as ammonium ions (NH4).ammonium ions (NH4).

c. Decomposition rates c. Decomposition rates affect the level of affect the level of nutrients available to nutrients available to primary producers.primary producers.

5. Ammonification 5. Ammonification

6. Denitrification6. Denitrification

a.a. Nitrates (NO3¯) are Nitrates (NO3¯) are reduced to N2 and reduced to N2 and are lost / returned to are lost / returned to the atmosphere. the atmosphere.

b.b. Facultative Facultative anaerobes in anaerobes in anaerobic anaerobic conditions break conditions break down the NO3’s.down the NO3’s.

c. Ex: Farmers c. Ex: Farmers w/waterlogged fields w/waterlogged fields and high-clay content and high-clay content are vulnerable to losing are vulnerable to losing the available nitrogen the available nitrogen for their crops.for their crops.

Phosphorous cyclePhosphorous cycle

Phosphorous CyclePhosphorous Cycle

2 ways: Short-term and Long Term2 ways: Short-term and Long Term

A. Short-termA. Short-term

1.1. Plants use P from soil in body tissues.Plants use P from soil in body tissues.

2.2. Animals get phosphorous fr eating Animals get phosphorous fr eating plants.plants.

3.3. When animals die, they return the When animals die, they return the

P to the environment.P to the environment.

Phosphorous CyclePhosphorous Cycle

Long Term Phosphorous CycleLong Term Phosphorous Cycle

1.1. Phosphates washed into the oceans b/c Phosphates washed into the oceans b/c part of rock compounds.part of rock compounds.

2.2. After millions of years, rock layers wash After millions of years, rock layers wash off and P b/c part of the environment.off and P b/c part of the environment.