Allows us to compare number of organisms present in each trophic level > at particular time
How is it Constructed
Consider food chain:
graph LR grass --> rabbit rabbit --> snake snake --> eagle
Suppose that:
- Ten eagles in given area → each eagle needs to find 1 snake every day.
- Month → 10 eagles need 300 snakes to keep them alive
- Snake → eats 2 rabbits a day. 300 snakes → need 18 000 rabbits in month
- Each rabbit eats 15 grass plants daily. 18000 rabbits → need about 8 100 000 grass plants in month
Number of organisms in Each trophic level → can be used to construct pyramid of numbers.
- Length of bar in pyramid → represents number of organisms present at that time
Limitations Of Using Pyramid of Numbers to Represent Food Chain
- Does not consider size and mass of organisms
- Does not consider whether organism is adult or juvenile