Pyramids Of Numbers Flashcards

1
Q

What is a pyramid of numbers?

A

It represents the number of organisms at each trophic level in a food chain

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2
Q

What are the 2 inferences that can be drawn from a normal shape of a pyramid of numbers?

A
  1. The number of organisms declines as you go up a pyramid of numbers.
  2. The body size of the organisms usually increases as you go up a pyramid of numbers.
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3
Q

Why does the number of organisms decline as you go up a pyramid of numbers?

A

Because of the large energy losses (about 90%) between each trophic level. This means there is less energy available to the organisms higher up the pyramid.

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4
Q

Why does the body size of the organisms usually increase as you go up a pyramid of numbers?

A

This is mainly because bigger animals tend to eat smaller animals, e.g. hawks are bigger than thrushes

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5
Q

What is a limitation of the pyramid of numbers?

A

It does not take into account the size of the organisms.

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6
Q

What are the two main shapes of pyramids of numbers? What is the third?

A

a normal pyramid and an inverted pyramid but there can also be a partially inverted pyramid

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7
Q

What type of pyramid do parasitic food chains normally have?

A

inverted pyramid of numbers

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8
Q

What can sometimes happen with these graphs in terms of their scales?

A

the numbers of organisms can be so great that the pyramid cannot be drawn to scale e.g. hundreds of millions of bacteria could live on a decomposing whale.

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