B2b: Energy flow

All living things need energy to live. Ultimately this energy comes from the Sun. This item explains how energy from the Sun flows through ecosystems and how humans can harness it. The work on energy transfer provides the opportunity to examine the ethical issues raised by decisions on plant use and the environmental effects of such decisions. 

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What is meant by the term trophic level?
A trophic level is a feeding level. The amount of energy, biomass and usually the number of organisms decrease as you move up a trophic level.
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Are there organisms other than green plants that are producers?
Yes.
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Why are some organisms primary and secondary consumers?
They feed on both animals and plants.
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How may changes in the population of one organism may affect the other organisms in a food web.
Some animals can just eat more of another organism if food is in short supply, while others may starve and die. This in turn can affect the populations of other organisms in the food web.
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Explain how energy from the Sun flows through food webs.
No artificial fertiliser and no pesticides.
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What do pyramids of biomass show?
They show the dry mass of living material at each stage of a food chain.
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Explain why pyramids of numbers and pyramids of biomass for the same food chains can be different shapes.
A pyramid of numbers shows the amount of organisms at each tropic scale, whereas pyramids of biomass show (living material in each organism x number)
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What are the difficulties when constructing pyramids?(2)
Problem with measuring dry biomass, and organisms may belong to more than one trophic level.
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Is energy transferred to more or less useful forms at each trophic scale?
Less.
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What three things is energy transferred into at each trophic scale?
Excretion, egestion and heat from respiration.
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How can excretory products, faeces and uneaten parts be used as the starting point for other food chains?
The waste is used by decomposers that can start another food chain.
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How does the efficiency of energy transfer explain the shape of pyramids of biomass?
The efficiency of energy transfer explains the shape of pyramids of biomass as some energy is used for growth and at each trophic level, energy is transferred into less useful forms.
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Explain how the efficiency of energy transfer explains the limited length of food chains.
Each trophic level 'loses' up to 90% energy, which means not a lot of food for animals at the end of a food chain.
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How do you calculate the efficiency of energy transfer?
Energy used for growth divided by energy input.
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Other cards in this set

Card 2

Front

Are there organisms other than green plants that are producers?

Back

Yes.

Card 3

Front

Why are some organisms primary and secondary consumers?

Back

Preview of the front of card 3

Card 4

Front

How may changes in the population of one organism may affect the other organisms in a food web.

Back

Preview of the front of card 4

Card 5

Front

Explain how energy from the Sun flows through food webs.

Back

Preview of the front of card 5
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