Which is the primary colonizer in primary succession on rock?

Transfer of material and energy from one ecosystem to another ecosystem is best exemplified by:

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

What will happen to an ecosystem if:
$(a)$ All producers are removed;
$(b)$ All organisms of herbivore level are eliminated; and
$(c)$ All top carnivore population is removed?

Match the trophic levels with their correct species examples in a grassland ecosystem.

$(a)$ Fourth trophic level	$(i)$ Crow
$(b)$ Second trophic level	$(ii)$ Vulture
$(c)$ First trophic level	$(iii)$ Rabbit
$(d)$ Third trophic level	$(iv)$ Grass

Select the correct option:

In a food chain, which of the following is produced in the largest amount?