In a tree ecosystem,the pyramid of number is

Which of the following representations shows the pyramid of numbers in a grassland ecosystem?

Consider the following statements about ecological pyramids:
$I.$ Charles Elton developed the concept of ecological pyramid.
$II.$ After his name,these pyramids are also called as Eltonian pyramids.
$III.$ It is a graphical representation or pyramid-shaped diagram which depicts the number of organisms,biomass,and energy at each trophic level.
Which of the statements given above are correct?

Explain various types of ecological pyramids.

Which of the following is not considered an ecological pyramid?

The pyramid of energy is always upright for any ecosystem. This situation indicates the fact that . . . . . .