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Energy and Ecosystems
Food chains and food webs

All living organisms rely on a source of energy to carry out every activity. The ultimate source of energy is the
sun, which is converted to chemical energy by photosynthesising organisms and is the passed as food between
other organisms. Organisms are…

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Energy transfer between trophic levels

Energy loss in food chains- Producers
Plants convert between 1 and 3% of the suns energy
available to them into organic matter. Most of the suns
energy is not converted into organic matter by
photosynthesis because;
·Over 90% of the suns energy is reflected back…

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Ecological pyramids
Pyramids are used to show quantative data at each trophic level. They can show number, mass or amount of
energy stored by organisms at each trophic level.

Pyramids of number- Usually the number of
organisms at a lower trophic level is greater than the
ones further up. This…

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Agricultural Ecosystems
What is an agricultural ecosystem?- Agricultural ecosystems are largely made up of domesticated animals and
plants to used to feed humans. Humans are the 3rd or 4th trophic level therefore they only take in a tiny amount
of the energy available from the sun in their food. Agriculture…

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Chemical and biological control of agricultural pests
What are pests and pesticides? A pest is an organism that competes with humans for
food or space, or it could be a danger to health. Pesticides are poisons chemicals that kill
pests. They are named after the pest that they destroy. An…

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Intensive rearing of domestic livestock
Intensive rearing and energy conservation
Intensive rearing of domestic livestock is about converting the
smallest possible amount of food energy into the greatest quantity
of animal mass. This can be done by minimising the energy that is
lost from the animals during their lifetime. This…


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