Which of the following types of organisms occupies more than one trophic level in an aquatic ecosystem?

Read the following statements carefully and answer the question:
$(1)$ Pyramids of number and biomass can be upright or inverted in an ecosystem.
$(2)$ Phosphorus and sulfur are sedimentary cycles.
$(3)$ The largest reservoir of carbon on Earth is found in the oceans.
$(4)$ The structural and functional unit of ecology is the ecosystem.
Which of the above statements are correct?

Identify the mismatched pair.

Which of the following statements is incorrect regarding the phosphorus cycle?

The exchange pool in the carbon cycle is:

Arrange the stages of hydrarch succession in the correct sequence.