Which of the following represents the largest man-made ecosystem?

Plankton, nekton and benthos are not the components of:

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

The species of plants that play a vital role in controlling the relative abundance of other species in a community are called

The gradual and predictable changes in the species composition of a given area are called $..........$.

Out of the total cost of various ecosystem services, the soil formation accounts for $P$, while contributions of other services like recreation and nutrient cycling are less than $Q$ each. The value of climate regulation and habitat for wildlife is about $R$ each. Identify $P, Q,$ and $R$.