Which of the following are known as the 'pioneer species' in primary succession?

Distinguish between:
$(a)$ Upright and inverted pyramid
$(b)$ Food chain and Food web

An ecosystem creates:

Which group of living organisms given below is a link in the food chain between green plants and a hawk?

Which of the following statements are correct regarding a food chain?
$(a)$ If $80\%$ of tigers are removed from an area,the growth of vegetation in that area increases.
$(b)$ If carnivores are removed from an area,the population growth of deer increases.
$(c)$ The length of a food chain is limited to $3$ to $4$ trophic levels because the amount of energy decreases in the ecosystem.
$(d)$ The length of a food chain is usually $2$ to $8$ trophic levels.

If all the plants of the world die,all the animals will also die due to the shortage of: