Ecology Pyramids

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What are 'pyramids of number'?
A pyramid with bars that have lengths proportional to the numbers (of organisms) present at each trophic level. (usually numbers of organisms at lower trophic levels are higher then those at higher levels.
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Pro's for pyramids of number?
It is simple to use for typical food chains.
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Cons for pyramids of number (1)
No account is taken of the size of the organism (e.g. one big oak tree has the same numerical value as a ladybird, leading to inverted or not pyramid).
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Cons for pyramids of number (2)
A number of organisms can be so big that you can't represent them on a pyramid of number. (e.g. millions of greenfly)
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What is a pyramid of biomass?
A pyramid showing the total mass of organisms in a particular place.
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What are the units of biomass?
gm^2 (grassland, seashore etc) and gm^3 (when measuring volume)
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Pro's for pyramids of biomass? (1)
A more reliable and quantitative description.
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Pro's for pyramids of biomass? (2)
Fresh mass is easy to obtain.
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Cons for pyramids of biomass (1)
Organisms must be killed to achieve the dry mass measurement - so sample is unrepresentative and ethics??
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Cons for pyramids of biomass? (2)
Only organisms at a particular time are shown and seasonal differences not taken into account. (e.g. marine ecosystems)
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What are pyramids of energy?
Pyramids that display the energy stored in organisms in an ecosystem to represent energy flow through a food chain.
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Units of measurements for pyramids of energy?
kJ m-2 year-1
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Pro's of pyramids of energy (1)
Most accurate representation.
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Pro's of pyramids of energy (2)
More reliable then biomass (e.g. species with the same mass may store different amounts of energy e.g. fats and carbs)
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Cons of pyramids of energy (1)
Collecting data can be difficult and complex
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Card 2

Front

Pro's for pyramids of number?

Back

It is simple to use for typical food chains.

Card 3

Front

Cons for pyramids of number (1)

Back

Preview of the front of card 3

Card 4

Front

Cons for pyramids of number (2)

Back

Preview of the front of card 4

Card 5

Front

What is a pyramid of biomass?

Back

Preview of the front of card 5
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