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Slide 1

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Grace Roe…read more

Slide 2

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Food chains
Food chains show where the energy goes and
what eats what for example:…read more

Slide 3

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Pyramids of numbers
Pyramids of numbers are just another way of
showing food chains:
100 rabbits
A field of grass
Each stage of food chain is called a Trophic
Level ­ in this one the rabbits are the second
Trophic Level.. Each bar on a pyramid of
numbers shows the total number of organisms
at that level of the food chain.…read more

Slide 4

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The grass goes at the bottom of the pyramid
because it is at the bottom of the food chain.
Grass is the producer- it convert light into energy
which they use for growth.
In a typical pyramid of numbers every time you go
up a trophic level the number of organisms go
down. This is because the big organism will
usually eat lots of smaller organisms to stay alive.
Pyramids of numbers have the advantage of
being easy to produce ­ you just count the
organisms at each level. They can be misleading
though the pyramids shape can be messed up by
the presence of small numbers of big organisms
(like trees) or large numbers or small organisms
(like fleas)…read more

Slide 5

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Pyramids of Biomass
Pyramids of biomass give a more accurate
Each bar on a pyramid of biomass shows the
mass of living material at that stage of the
food chain- basically how much all the
organisms at each level would weigh if you put
them all together. So one tree would have a
big biomass and hundreds of fleas would have
a small biomass.
The advantage of pyramids of biomass is that
they give a fairly accurate indication of the
amount of energy at each level in the food…read more

Slide 6

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Pyramid of biomass
Pear tree…read more

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