(i) Create a terrestrial food chain depicting four trophic levels.
(ii) Why do we not find food chains of more than four trophic levels in nature?
OR
How will you create an artificial aquatic ecosystem, which is self-sustainable?
(i) A terrestrial food chain depicting four trophic levels is as follows- grass (producer), eaten by a mouse (primary consumer), eaten by a snake (secondary consumer), eaten by a hawk (tertiary consumer).
(ii) We do not find food chains of more than four trophic levels in nature because energy and biomass decrease from lower to higher trophic levels so the length of the food chains is restricted.
OR
We can create an artificial aquatic ecosystem by setting up an Aquarium which essentially is a box made of glass filled with water. In this, we can plant some Hydrophytes (Plants that live in water). These will take up CO2 released by the aquatic animals and provide O2 into the ecosystem through Photosynthesis. We may now add some aquatic organisms such as Fishes which will take up the dissolved O2 and eat the plants as a feed. Additionally, we will add some decomposers like Fungi and Bacteria along with scavengers such as Crustaceans and Marine worms to help clean any dead remains. This decomposed organic matter will provide nutrition for the growth of the plants, thus making the whole ecosystem self-sustaining.