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Ecosystems and Habitats
DEFINITIONS
The following common terms can be used to describe living things in their environment:
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environment - all the conditions that surround a living organism
habitat - the place where an organism lives
population - all the members of a single species that live in a habitat
community - all the populations of different organisms that live together in a habitat
ecosystem - a community and the habitat in which it lives

Biodiversity is a measure of the variety of different species living in a habitat
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Food Chains
A food chain shows what eats what in a particular habitat
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The Sun is the ultimate source of energy for most communities of living things
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Producers are organisms that make their own organic nutrients (food) - usually using energy from sunlight
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The other organisms in a food chain are consumers, because they all get
their energy by consuming other organisms
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It shows the energy flow through part of an ecosystem
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Squirrels and earthworms are primary consumers, and the wood mice are
secondary consumers
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Foxes and owls eat the wood mice, and foxes eat wood mice and squirrels
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COMPETITION AND INTERDEPENDENCE
Habitats have limited supplies of the resources needed by plants and animals
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In a food web,changes in the population of one organism have an effect on the populations of other organisms
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TROPHIC LEVELS
The position of an organism in a food chain, food web or pyramid is its trophic level
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This is why there are fewer organisms at each trophic level in the
example above
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It is then passed from one
organism to the next in complex molecules, and
returned to the atmosphere as carbon dioxide again
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Removing CO2 From the atmosphere; Plants use
carbon dioxide from the atmosphere for
photosynthesis
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Passing carbon from one organism to the next; when an animal eats a plant, carbon from the plant becomes part of
the fats and proteins in the animal
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The carbon then becomes part of these organisms
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It is also released by the combustion of wood and fossil fuels (such as coal, oil
and natural gas)
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Decomposition or decay also releases carbon dioxide
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Nitrogen from the air is converted into soluble ions that plant
roots can absorb
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It is returned to the atmosphere as nitrogen gas
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Stage 1- Fixation; About 78 per cent of the air is nitrogen gas
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It must be converted into soluble ions, such as nitrates
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Lightning can also convert nitrogen gas into nitrates
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Stage 2- Absorption in the roots; Plants absorb nitrates from the soil and use these to make proteins
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Nitrogen is also passed from one animal to another by feeding
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This
results in nitrogen being returned to the soil as ammonium ions, which nitrifying bacteria can convert into nitrates
for plants to absorb
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WATER CYCLE
The water cycle is also known as the hydrological cycle
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Water molecules move between various locations - such as rivers, oceans and the atmosphere - by specific
processes
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Evaporation; Energy from the Sun heats the Earth’s surface and water evaporates from oceans, rivers and lakes
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Transpiration; Transpiration from plants releases water vapour into the air
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Water vapour condenses back into liquid water, and this
condensation process produces clouds
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This is called precipitation (it is not the same as precipitation in Chemistry)

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