Which one of the following is not a functional unit of an 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?

Transfer of material and energy from one ecosystem to another ecosystem is best exemplified by:

Which of the following characteristics of an ecosystem is naturally provided to human society?

Which of the following processes occurs at a faster rate?

Which of the following animals occupies more than one trophic level in the same ecosystem at the same time?