Cycling of Matter

Oxygen

Carbon

Nitrogen

Change & Recovery in Ecosystems

What happens to the

materials that make up

a truck when it begins

to rust?

What happens to the

tree after it dies?

Cycling of Matter in Ecosystems Organic substances

Contain atoms of Carbon and Hydrogen

Are broken down into simpler forms in living things

Ex. Sugar, carbohydrates, proteins, amino acids

Inorganic substances Do not contain combination of

carbon and hydrogen Ex. Water (H2O), ammonia

(NH3), Carbon dioxide (CO2)

Biological Processes Involved in Nutrient

Cycling

1. Photosynthesis

Plants convert CO2 and H2O into O2 and sugar

6CO2 + 6H2O + energy → C6H12O6 + 6O2

2. Respiration

Animals AND plants use O2 and sugar,

converting it to CO2 and H2O

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

More Processes 3. Decomposition

• Remains of dead organisms are broken down by bacteria and fungi

• All molecules are released into soil

4. Excretion

• Waste material from animals is broken down and returned to the soil

5. Assimilation

• Conversion of molecules into a useable form by bacteria

• Nitrification, denitrification

Cycling of Organic Matter The atoms and molecules

available to make up organisms on earth is limited

All the atoms MUST be recycled in order for new organisms to form.

It is very likely that at least one of the carbon atoms in your body was also in a 70 million year old dinosaur

Recycling of Matter by Micro-organisms

The Matter Cycle

Soil

Grass

Cow Person

Decomposers

1. Dead plants and animals are broken down

by decomposers – their atoms / molecules

are released into the system to be re-used

2. Atoms, molecules accumulate in the soil

3. Nutrients are taken up by grasses

4. Cows eat the grass – nutrients and atoms

are passed on to the cow

5. Person eats cow – nutrients and atoms are

passed on to person

6. Each of these things can die, the atoms are

broken down by decomposers and

recycled for the next living things

The Oxygen Cycle

Respiration:

C6H12O6 + O2 CO2 + H2O + energy

Photosynthesis:

CO2 + H2O + light C6H12O6 + O2

What do you notice about these two chemical

reactions?

The Oxygen Cycle

Oxygen

(in atmosphere)

RESPIRATION by plants, animals and decomposers

Carbon Dioxide

(in atmosphere)

PHOTOSYNTHESIS

by green plants Combustion

(burning stuff)

The Carbon Cycle CO2 in the atmosphere

volcanic

eruption

CO2

dissolved in

water

Ocean

sediment

combustion

Fossil fuels Conversion to fossil fuels

Decomposition

Glucose

Photosynthesis - carbon

is stored in the biomass

Aerobic

respiration

Weathering

The Carbon Cycle

Two groups of carbon sources in the

carbon cycle 1. Biotic - Aerobic respiration (in the presence of

O2), and decomposition

The organic reservoirs (storage areas) for

carbon are the bodies of living things

2. Abiotic - Combustion and geological activity

The inorganic reservoirs for carbon are

the atmosphere, the oceans, and the

Earth’s crust

The Nitrogen Cycle

The movement of nitrogen through ecosystems, soil, and

the atmosphere is called the nitrogen cycle.

Nitrogen is a component of many organic molecules.

forms an essential part of amino acids (the building

blocks of proteins) and DNA.

is essential for all living cells.

in gas form (N2) makes up about 78% of atmosphere.

The Nitrogen Cycle

Most organisms cannot use nitrogen in the gaseous

form found in the air we breathe, so it must be in

“fixed” forms that plants can absorb.

“Fixed” nitrogen compounds that plants CAN use:

nitrate ions (NO3−)

ammonia (NH3)

urea (NH2)2CO

The Nitrogen Cycle ~ 4 Processes Process #1 ~ NITROGEN FIXATION

To “fix” the nitrogen in the air, it must have its bonds broken so

it can combine with other atoms to enter the food chain. This

takes substantial amounts of ENERGY.

Three ways N2 bonds can be broken:

Atmospheric fixation - lightening breaks

nitrogen molecules and enables their atoms to

combine with oxygen in the air forming

nitrogen oxides. These dissolve in rain,

forming nitrates that are carried to the earth.

only a small amount is fixed this way ~ about 10%

Nitrogen Fixation (cont.)

Biological fixation – Bacteria are the only

organisms able to take N2 and combine it with

hydrogen to make ammonia.

Most are free-living in soil.

Some have developed an association with

certain plants. In return for sugars from the

plant, these bacteria fix nitrogen which can

be used by the plant for growth.

bacteria fix 60% of nitrogen gas

Nitrogen Fixation (cont.)

Industrial fixation – In the manufacturing

process, N2 is converted together with

hydrogen gas (H2) into ammonia (NH3).

Ammonia can be used directly as fertilizer, but

most of it is further processed to urea and

ammonium nitrate (NH4NO3).

Today, about 30% of the total fixed nitrogen is manufactured in ammonia chemical plants.

The Nitrogen Cycle ~ 4 Processes

a process by which nitrogen-fixing bacteria oxidize

ammonia first into nitrites (NO2 –) and then into nitrates

(NO3–).

Two different bacteria are involved. One transforms

ammonia to nitrites, the other transforms the nitrites to

nitrates.

plants can easily absorb nitrates and use them to form

proteins (to then be used in food chains).

Process #2 ~ NITRIFICATION

The Nitrogen Cycle ~ 4 Processes

decomposers break down the molecules in excretions and

dead organisms into ammonia.

most of the ammonia produced by decay is converted into

nitrates by nitrifying bacteria (nitrification process).

Process #3 ~ DECAY

The Nitrogen Cycle ~ 4 Processes

The only process that puts nitrogen back into the

atmosphere by reducing nitrates into nitrogen gas (N2).

Bacteria that live deep in the soil and in aquatic sediments

where there is no oxygen use the oxygen atom in the

nitrate (NO3−) for their respiration, thus closing the cycle.

Process #4 ~ DENITRIFICATION

Schematic representation

of the flow of nitrogen

through the environment.

The importance of

bacteria in the cycle is

immediately recognized

as being a key element in

the cycle, providing

different forms of

nitrogen compounds

taken on by higher

organisms.

Nitrogen Cycle ~ review

Nitrogen Cycle ~ review

The Nitrogen Cycle

The Nitrogen Cycle

Essential to living things for the production of amino acids used to synthesize proteins, and nucleic acids which are used to carry the hereditary or genetic code

Plants and animals are unable to use any of the N2 that is in the atmosphere

The nitrogen cycle can occur in both terrestrial and aquatic ecosystems

Nitrogen Cycle Complex cycle can be simplified as follows

For plants to make use of nitrogen it must first be

converted into ammonia or nitrates (NO3-)

two pathways that produce nitrate ions:

fixation by lightning (produces nitrates directly)

fixation by bacteria (producing ammonia) followed by

nitrification by bacteria (converting the ammonia to

nitrates)