What type of organisms are producers?

There are generally a greater number of individuals at the lower trophic levels of an ecosystem.

$(a)$ What is an ecosystem? List its two main components.
$(b)$ We do not clean ponds or lakes,but an aquarium needs to be cleaned regularly. Explain.

$(i)$ What is the height of the ozone layer from the equator?
$(ii)$ Name the rays against which the ozone layer provides protection.
$(iii)$ Name one effect of the depletion of the ozone layer.

Which chemical is used in fire extinguishers? How is it harmful?

Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the