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Ecology
4
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Population = a group of organisms of the same species who live in the same area at the same
time
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Ecosystem = a community and its abiotic environment
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Heterotrophs:
All species need a supply of organic nutrients
...

Methods of obtaining these carbon compounds can be divided into two types:
• Autotrophic: organisms make their own carbon compounds from carbon dioxide and
other simple substances – they are self-feeding
...

Some unicellular organisms use both methods of nutrition
...


Types of Heterotrophs:
Consumers: Feed on living organisms by ingestion
...
They ingest their food, meaning they take in
undigested material from other organisms
...
Cause decay by releasing enzymes onto the dead
animal or plant
...
Organisms that feed on dead material in this way are called
saprophytes
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This is dead and
decaying material
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(internal digestion)

Ecosystem Sustainability:
If there is enough sunlight to provide energy for autotrophs to photosynthesise, if the
community itself can maintain the recycling of inorganic nutrients within the abiotic
environment and the community isn’t damaged, the ecosystem has the potential to remain
stable and self sustaining for a long period of time
...


Energy enters the ecosystem as light energy and leaves as heat energy
...

A continual supply of energy is important as energy cannot be recycled
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• They are self-sustaining natural systems
...

• They allow a greater number of key variables to be controlled and manipulated to
evaluate how organisms or communities may respond to changing environmental
conditions
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4
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A food chain is a sequence of organisms, each of which feeds on the previous one
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It is rare for there to be more
organisms in the chain
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The subsequent organisms are consumers
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No consumers feed on the last organism
in a food chain
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The arrows in a food chain therefore indicate the direction of energy flow
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Energy Loss:
Not all of the energy taken in by an organism can be assimilated into its body
...
g
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• Some food is eaten and passes through the digestive system of an organism as
undigested waste in faeces
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• Some is used by living organisms as they respire to provide energy for their own
movement and to keep their body temperature constant, this energy will be lost to
the environment as heat
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3: Carbon Cycling
Archaea:
Archaea are a group of microscopic organisms that were discovered in the earl 1970s
...

Archaeans were originally thought to be bacteria until DNA analysis showed that they are
different
...

There is still much about archaeans that isn’t known
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Methanogens:
The gas methane is produced naturally by a group of prokaryotes called methanogenic
archaeans
...
This process happens in swamps, bogs, and other sites where there are
anaerobic conditions, so dead organic matter is not fully decomposed by saprotrophic
bacteria and fungi
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Methane is a relatively stable substance in the atmosphere, but is eventually oxidised to
carbon dioxide, so concentration of methane in the atmosphere have remained low
...

In waterlogged, wetland soil only anaerobic bacteria can survive because there is so little
oxygen
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Over
thousands of years, the organic matter gradually becomes peat
...
These remains become fossil fuels – coal,
gas, and oil
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Carbon Cycle:



Carbon Flux:
Carbon is found in different forms and different places, known as ‘pools’
...
It is the net difference between
carbon removal and carbon addition
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4: Climate Change

Greenhouse Gases:
Greenhouse gases absorb long wave radiation so that heat is retained within the atmosphere
...

Without these gases in the atmosphere, the Earth’s
temperature would be too low to support life
...

A greenhouse is made of glass, which allows shortwave
radiation from the sun to pass through it
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Glass is less
transparent to these long wavelengths and heat is trapped in
the greenhouse, making it warmer inside
...
They trap heat that is radiated from the Earth’s surface and keep the Earth
at a comfortable temperature for life to exist
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Cell respiration by living organisms
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Combustion of biomass and fossil fuels – a growing human population has meant a
great demand for energy and this has resulted in burning of coal, oil and gas for power
stations, vehicles, shipping and aeroplanes
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Removal of Carbon Dioxide:
1
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Humans have
upset this balance by deforesting vast areas of forest for agriculture and timber
production
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2
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Formation of Water Vapour:
1
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2
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Removal of Water Vapour:
1
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Methane:
• Produced by human activity when organic waste decomposes in landfill sites
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• Comes from cattle farming – more cattle are being farmed for meat
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• Each methane molecule is 23 times more effective at trapping heat energy compared
to a molecule of carbon dioxide but has less of an impact on global warming because
it is present in much smaller amounts in the atmosphere
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o This is affected by the rate at which it is released and how long it remains there
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HFCs as Greenhouse Gases:
Chlorofluorocarbons (CFCs) were used in aerosols and as refrigerants but were found to
damage the ozone layer when released into the atmosphere
...
Damage to the ozone layer is not a cause of the greenhouse effect of
increased global temperature
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• A rise in sea levels, causing flooding to low lying areas
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Some parts of the world may experience more
storms and hurricanes
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• Extinction and resultant loss of biodiversity
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• They are some of the most biodiverse but fragile ecosystems in the world
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• Coloured species of algae live within the reef which give them their colourful plantlike appearance
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• Often this results in the death of the coral
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• Also as more carbon dioxide dissolves in sea water, making it more acidic, it affects
the ability of coral to make their skeletons and growth slows down
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• Predicted rises in sea level caused by melting sea ice could also affect reefs by making
the water too deep to allow adequate sunlight to reach them

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