Pyramids Of Numbers

Question 1

What is a pyramid of numbers?

Answer 1

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

Question 2

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

Answer 2

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.

Question 3

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

Answer 3

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.

Question 4

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

Answer 4

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

Question 5

What is a limitation of the pyramid of numbers?

Answer 5

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

Question 6

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

Answer 6

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

Question 7

What type of pyramid do parasitic food chains normally have?

Answer 7

inverted pyramid of numbers

Question 8

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

Answer 8

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.