Matter is not
created
or
destroyed
Law of Conservation of Matter
Matter is recycled
• 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
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
Volcanic
activity
Respiration
Decomposition
Human
activity
Erosion
CO2 in Ocean
Respiration
Uplift
Deposition
Photosynthesis
Fossil fuel
feeding
Deposition
Carbonate
Rocks
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 Cycle
 Nitrogen, 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