Pyramids Of Numbers Flashcards
What is a pyramid of numbers?
It represents the number of organisms at each trophic level in a food chain
What are the 2 inferences that can be drawn from a normal shape of a pyramid of numbers?
- The number of organisms declines as you go up a pyramid of numbers.
- The body size of the organisms usually increases as you go up a pyramid of numbers.
Why does the number of organisms decline as you go up a pyramid of numbers?
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.
Why does the body size of the organisms usually increase as you go up a pyramid of numbers?
This is mainly because bigger animals tend to eat smaller animals, e.g. hawks are bigger than thrushes
What is a limitation of the pyramid of numbers?
It does not take into account the size of the organisms.
What are the two main shapes of pyramids of numbers? What is the third?
a normal pyramid and an inverted pyramid but there can also be a partially inverted pyramid
What type of pyramid do parasitic food chains normally have?
inverted pyramid of numbers
What can sometimes happen with these graphs in terms of their scales?
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.