$A$ pond is a.......

Phosphorus cycles in the form of

What is a biogeochemical cycle? What is the role of the reservoir in a biogeochemical cycle? Give an example of a sedimentary cycle with a reservoir located in the Earth's crust.

The food chain which begins with dead organic matter is called

What is an ecosystem service? List any four important ecosystem services provided by the natural ecosystems. Are you in favour or against levying a charge on the service provided by the ecosystem?

$A$ simplified model of phosphorus cycling in a terrestrial ecosystem is given below. Identify $A, B, C$ and $D$.