(a)
In the above pyramid the population of insects is more than the tree; therefore, the size of pyramid increases, but the number of small birds is lesser than the insects. The pyramid size becomes narrow. Further, big birds are lesser than small birds. So the size of pyramid becomes narrower.
(b) Actually, the pyramids of numbers do not give a true picture of the food chain, as they are not very functional. They do not indicate the relative effect of the geometric food chain and size. Here, the size of the pyramid becomes variable. The pyramid of biomass of the given situation will be :
The pyramid of biomass in this ecosystem is upright because the biomass decreases at each trophic level.
