In an ecosystem,rats feed on grains. Name the trophic level to which the rats belong.

Omnivores consume $.....$

Mention the role of microorganisms like bacteria and fungi in the ecosystem.

In the given figure,the various trophic levels are shown in the form of a pyramid. At which trophic level is maximum energy available and at which trophic level is the maximum number of organisms present?

Which of the following is not included in a freshwater ecosystem?

Excessive exposure of humans to $UV$-rays results in:
$(i)$ Damage to immune system
$(ii)$ Damage to lungs
$(iii)$ Skin cancer
$(iv)$ Peptic ulcers