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Material Cycles

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Objectives

Identify different material cycles that occur in

nature and the key process involved

Illustrate that water, carbon, and nitrogen

cycles

Evaluate the importance of material cycles to

ecosystem stability

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What are material cycles and why are

they important? Material cycles (Biogeochemical cycles): the movement (or cycling)

of matter through a system

By matter we mean: elements (carbon, nitrogen, oxygen) ormolecules (water)

These elements are essential to the biochemical processes that arecarried out in living cells.

All mattercycles, it is neither created nor destroyed

As the Earth is essentially a closed system with respect to matter,we can say that all matter on Earth cycles

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Material cycles

If an ecosystem is to be self-sustaining,

materials must be cycledamong the

organisms and the abiotic environment

The same materials needed to carry out life's

processes can be reused by different livingorganisms

In an ecosystem energy flows and materialscycle

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Material Cycles

Three essential material cycles to ecosystem

stability:

Water cycle

Carbon-oxygen cycle

Nitrogen cycle

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The Water Cycle

Water is the source of hydrogen, one of the

elements for the making of carbohydrate

molecules by green plants

Water is necessary as the dissolving medium

for substances that cross cell membranes

Without water, there can be no life

The suns energy drives the movement ofwater through the environment

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Water cycle

There are 3 ways in which water vapor enters theatmosphere

1. Waterevaporates from land surfaces and frombodies of water

2. Water vapor enters the air as a waste product ofrespiration of plants and animals Every time you exhale water vapor is released into

the air

3. Water is lost from plants through the openings in

leaves, through a process called transpiration

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Water Cycle

Water vapor in the air is carried to highaltitudes where it is cooled and forms cloudsby condensation

Water vapor returns to Earth in the form ofprecipitation: rain, snow, sleet

80% of precipitation falls over the oceans

Part of the remaining 20% evaporates from

the mainland and is returned back to theatmosphere

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Water Cycle

Water that does not evaporate enters the soiland becomes available to plant roots and soilorganism

Soil water that is not absorbed by plantsseeps into the ground, this water isgroundwater

Groundwater moves along layers of rock until

it reaches an outlet into a large body of watersuch as a lake or ocean

The water cycle then repeats

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Water cycle

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Carbon-Oxygen Cycle

Carbon dioxide and oxygen cycle through the

abiotic and biotic components of ecosystems

This process involves:

Photosynthesis

Respiration

Decomposition

Combustion

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Carbon-Oxygen Cycle

Green plants convert the suns energy into

nutrients by a photosynthesis

In photosynthesis carbon dioxide (CO2 ) and

water (H2O )combined to form sugars

(CH2O) and oxygen (O2 )

CO2 + H2O +light energy CH2O + O2

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Carbon-oxygen Cycle

Respiration- animals take in simple sugars

and oxygen and release carbon dioxide,

water, and energy (break bonds in simple

sugars) CH2O + O2 CO2 + H2O + energy

Animals eat simple sugars from plants and

take in oxygen from the atmosphere to

produce carbon dioxide, water, and energy

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Carbon-oxygen cycle

Decomposition- when plants or animals die

all the carbon, oxygen, nitrogen, calcium, etc

return to the soil and atmosphere

Decomposers such as fungi, bacteria,

insects, etc break down dead organic matter

and recycle materials such back to the soil

and atmosphere

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Carbon-oxygen cycle

Combustion- (the process of burning) when

combustion occurs CO2 is released into the

atmosphere

Natural combustion occurs by way of volcaniceruptions, however most pollution problems

occur because cars and factories release

CO2 into the atmosphere by burning fossil

fuels (coal, gas, oil)

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Carbon-Oxygen cycle

Photosynthesis-returns oxygen tothe atmosphere

Respiration- returnsCO

2

to theatmosphere

Decomposition-returns CO2 andOxygen toatmosphere and soil

Combustion- returns

CO2 to theatmosphere

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Nitrogen Cycle

About 80% of the air is elemental nitrogen

(N2)

Nitrogen is needed for the production of

proteins, which is essential to all living things

Nitrogen must be in a combined form before

it can be used by the cells of living things

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Nitrogen cycle

Nitrogen becomes available to plants through

the action ofnitrogen-fixing bacteria

Nitrogen-fixing bacteria converts atmospheric

nitrogen into nitrates

Plants use nitrates for protein synthesis

Animals eat plants and convert the plant

protein into animal protein

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Nitrogen cycle

Nitrogenous wastes and the bodies of dead

plants and animals are broken down by

decomposers (bacteria of

decomposition/decay) and ammonia (NH3) isreleased

Ammonia may be converted into nitrates by

nitrifying bacteria

Nitrogen containing compounds may also bebroken down by denitrifying bacteria, resulting

in the release of nitrogen into the atmosphere

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Nitrogen cycle

3. Bacteria of

decay

4. Denitrifying

bacteria

1.Nitrogen

fixing

bacteria

2.Nitrifying