Name an organism found as a secondary carnivore in an aquatic ecosystem.

Under what conditions would a particular stage in the process of succession revert back to an earlier stage?

Which of the following is not a structural aspect of an ecosystem?

Given below is a list of autotrophs and heterotrophs. With your knowledge about food chain,establish various linkages between the organisms on the principle of 'eating and being eaten'. What is this inter-linkage established known as?
Algae,hydrilla,grasshopper,rat,squirrel,crow,maize plant,deer,rabbit,lizard,wolf,snake,peacock,phytoplankton,crustaceans,whale,tiger,lion,sparrow,duck,crane,cockroach,spider,toad,fish,leopard,elephant,goat,nymphae,spirogyra.

The total quantity of global carbon is distributed such that $1\%$ is carbon in the atmosphere and $71\%$ is carbon dissolved in the oceans.

Define/Explain: Keystone species.