Matter is not createdor

destroyedLaw of Conservation of Matter

• Matter is passed from one organism to another and from one part of the Earth to another through biogeochemical cycles

• Matter is recycled because biological organisms do not use up matter, they just transform or re-organize it

• Matter is assembled into living things or passed out of the body as waste

Matter is recycled

Nutrient Cycles

We need to recognise that certain compounds are required for the survival of living things.

For organisms to grow, reproduce and maintain life they need a supply of elements (atoms) of which their tissues are made.

Nutrient cycles describe how particular elements cycle through a system. They have two parts: a biological component showing how the element cycles through living organisms and a geochemical component showing how the element cycles through non-living components such as soil, rocks, water and the atmosphere.

Nutrient cycles are also known as biogeochemical cycles.

Carbon Cycle

The Carbon Cycle

• All living things need carbon. It forms the basis of all organic material- carbohydrates, fats, proteins and nucleic acids.

The Carbon Cycle• Carbon cycles through the organic compounds

of living things and their non-living surrounds in a number of ways.

CO2 in Atmosphere

Photosynthesis

feeding

feeding

Respiration

Deposition

Carbonate Rocks

Deposition

Decomposition

Fossil fuel

Volcanic activity

Uplift

Erosion

Respiration

Human activity

CO2 in Ocean

Photosynthesis

The Carbon Cycle

Carbon is unique in that it can cycle without the aid of decomposers.

Sometimes dead material does not decay because it exists in an anaerobic (no oxygen) or highly acidic environment. In such situations the organic material may accumulate to form fossil fuels such as peat, coal, oil and gases.

The amount of carbon in the atmosphere is maintained largely by a balance between photosynthesis, which withdraws carbon dioxide from the atmosphere, and respiration and combustion, which add carbon dioxide to the atmosphere.

Oxygen Cycle

The Oxygen Cycle

Oxygen is a waste product of photosynthesis but is required as in input in cellular respiration.

In this way, oxygen cycles from plants, to the atmosphere, and then to animals.

In a balanced system the amount of oxygen required for cellular respiration equals the amount produced by photosynthetic organisms.

The Nitrogen Cycle

The Nitrogen CycleNitrogen, just like carbon and oxygen, is an essential element

needed by living organisms. Proteins are involved in cell control and the growth of new cells.

Nitrogen (N2) makes up about 80% of the atmosphere but plants are unable to take in nitrogen from the atmosphere. Most plants can only absorb nitrogen in the form of nitrates from the soil. Animals rely on plants for their source of nitrogen.

The nitrogen cycle is more complicated than the carbon and oxygen cycle and relies on three types of bacteria: the fixers, the nitrifiers and the denitrifiers.

Nitrogen can only be removed from the atmosphere in two ways: by lightening or by nitrogen fixation.

Nitrogen Fixation In order for nitrogen to be usable by plants

it needs to be “fixed”- free nitrogen is combined with hydrogen or oxygen to form ammonium (NH4) or nitrate (NO3).

The process of nitrogen fixation is carried out by certain types of bacteria in the soil. The bacteria absorb nitrogen gas from air spaces within the soil.

Some bacteria enter the roots of plants such as casuarinas, acacias and legumes (clover, peas, beans) causing the plant to form swellings called nodules. It is in these nodules that the bacteria fix nitrogen.

Nitrogen Fixation

Ammonia (NH3) is released in urine and decay of faeces, dead plants and animals. Nitrifying bacteria in the soil convert this ammonia to nitrites (NO2

-). Other bacteria then convert the nitrites to nitrates (NO3

-) which can be taken up by plants.

Animals obtain nitrogen by eating plants.

Returning Nitrogen to the Atmosphere

Converting nitrates back to nitrites releases oxygen. This the reverse of the nitrification needed by plants to be able to absorb nitrogen. Bacteria in waterlogged soils denitrify nitrates to produce much needed oxygen. While the oxygen is used by the bacteria, the nitrites are released back into the atmosphere and the nitrogen cycle starts again.

Water Cycle

The Water Cycle

Water is essential for the proper functioning of cells.

The water cycle describes how water circulates through an ecosystem.

The water cycle is driven by two energy sources: solar energy and gravity.

This cycle involves the processes precipitation, infiltration, percolation, evaporation, transpiration, and condensation.

Water Cycle: water cycles between the ocean, atmosphere, and land