Ecosystems

biosphere

Ecosystem inputs

constant inputof energyenergy flowsthrough

nutrients cycle

nutrients can only cycle

inputs energy nutrients

inputs energy nutrients

• Matter is recycled and reused between the living and nonliving worlds through biogeochemical cycles• Water• Carbon• Nitrogen• Phosphorus

Biogeochemical Cycles

Lakes

Runoff

Percolation in soil

Evaporation

Transpiration

Precipitation

Oceans

Solar energy

AquiferGroundwater

Water cycle

Water vapor

Birds

Herbivores

Plants

amino acids

CarnivoresAtmosphericnitrogen

loss to deep sediments

Fish

Plankton withnitrogen-fixingbacteria

Nitrogen-fixingbacteria(plant roots)

Nitrogen-fixingbacteria (soil)

Denitrifyingbacteria

Death, excretion, feces

Nitrifying bacteria

soil nitrates

excretion

Decomposing bacteria

Ammonifying bacteria

Nitrogen cycle

All organisms need nitrogen to make proteins and nucleic acids

Nitrogen gas makes up 78% of the Earths atmosphere

Most plants only use nitrates (NO3)

Nitrogen Cycle

Nitrogen fixationThe process bacteria use to convert nitrogen gas (N2) to

ammonia (NH3)

The bacteria are known as nitrogen-fixing bacteria

They live in the soil and inside swellings on the roots of some plants (beans, clover, etc)

The plants supply the carbohydrates for the bacteria and the bacteria provide usable nitrogen

The bodies of dead organisms contain nitrogen (proteins & nucleic acids)

Urine and dung also contain nitrogen

Decomposers break down these materials and release the nitrogen as ammonia (NH3), which becomes ammonium (NH4

+) in the soil

Processes known as ammonification, and makes nitrogen available to other organisms again.

Recycling Nitrogen

Soil bacteria take up NH4 + and

oxidize it into nitrites (NO2 -)

and nitrates (NO3 -) through the

nitrification process

Plants use nitrates to form amino acids

Recycling Nitrogen

When anaerobic bacteria break down nitrates and release nitrogen gas into the atmosphere

How nitrogen gas returns to the atmosphere

Animals must obtain nitrogen by eating plants and other organisms

Denitrification

Phosphorus cycle

Loss to deep sediment

Rocks andminerals

Soluble soilphosphate

Plants andalgae

Plants Urine

Land animals

Precipitates

Aquaticanimals

Animal tissueand feces

Animal tissueand feces

Decomposers(bacteria andfungi)

Decomposers(bacteria & fungi)

Phosphatesin solution

Loss indrainage

Phosphorous CycleThe movement of phosphorous from the environment to the

organisms and back again

Phosphorous is essential to animals for bones, teeth, and DNA/RNA

Plants get it from the soil; Animals get it from other organisms

Extremely slow cycle and doesn’t normally occur in atmosphere

When rocks erode, small amounts of phosphorous dissolve as phosphate (PO3

-)

Plants absorb phosphates through their roots

Also added when wastes and organisms decompose

Some comes from fertilizer

Phosphorous Cycle

Carbon cycleCO2 inatmosphere

Diffusion RespirationPhotosynthesis

Photosynthesis

Plants and algae

PlantsAnimals

Industry and home

Combustion of fuels

Animals

Carbonates in sediment

Bicarbonates

Deposition ofdead material

Depositionof deadmaterial

Fossil fuels(oil, gas, coal)

Dissolved CO2

• Photosynthesis and cellular respiration form the basis of this cycle

• In photosynthesis, plants and other autotrophs use CO2, water, and solar energy to make carbohydrates

• Autotrophs and heterotrophs break down carbohydrates during cellular respiration

Carbon Cycle

The byproducts of cellular respiration are carbon dioxide and water

Decomposers also release CO2 into the atmosphere when they break down organic molecules

Carbon Cycle

Human Influences on the Carbon Cycle The concentration of

atmospheric carbon has risen more than 30% in the last 150 years

Humans contribute by burning fossil fuels and organic matter to produce energy

The remains of organisms that have been transformed by decay, heat, and pressure into energy rich molecules

Burning releases the energy and CO2

When large areas of land are burned, more CO2 is produced, and less plants are there to absorb it

Fossil Fuels

The Greenhouse Effect and Carbon Dioxide

The mean global temperature has increased about 1 °C since 1900, possibly because of trace gases like methane and CFC’s.

The atmospheric level of methane has more than doubled since 1951. What could have caused this?

Methane is the product of the bacterial decomposition of organic matter in the absence of oxygen. Mainly occurs in rice paddies and digestive tracts of termites (now in greater number because of the forests being destroyed).

GREENHOUSE EFFECT

Breaking the water cycle• Deforestation breaks the water cycle– groundwater is not transpired to the

atmosphere, so precipitation is not created

forest desert

desertification

Effects of deforestationCo

ncen

trati

on o

f nitr

ate

(mg/

l )

1965 1966Year

2

0

4

40

80

1967 1968

Deforestation

nitrate levels in runoff

40% increase in runoff loss of water

40% increase in runoff loss of water

60x loss in nitrogen 10x loss in calcium

60x loss in nitrogen 10x loss in calcium

loss into surface water

loss out of ecosystem!

T or F: The process that returns nitrogen to the atmosphere is called ammonification.

FALSE!

Denitrification!!

How could humans affect the nitrogen cycle at the bacterial level?

The addition of toxic chemicals to the soils; construction and

deforestation can cause soil erosion

Pick 2 and write me an essay about each.

1. The role of bacteria in the carbon, nitrogen, and phosphorous cycles.

2. Explain the statement that nutrients cycle , but energy flows.

3. How do plants influence the various biogeochemical cycles?

4. How do humans influence the various biogeochemical cycles?