$A$ pond can be classified under which type of ecosystem?

An ecosystem involves:

Which of the following is a characteristic feature of an agro-ecosystem?

Consider the following statements about the carbon cycle and choose how many statements are correct?
$(a)$ The atmosphere contains $71\;\%$ of the total global carbon.
$(b)$ Decomposers contribute substantially to the $CO_2$ pool by processing waste materials and dead organic matter from land or oceans.
$(c)$ $4 \times 10^{13}\; kg$ of carbon is fixed through photosynthesis annually.
$(d)$ There is no respiratory input into the atmosphere.
$(e)$ Carbon constitutes $49\;\%$ of the dry weight of organisms.

The correct sequence of hydrarch succession is:

The movement of nutrients from non-living components to living components and back to non-living components in a cyclic manner is known as: