What is Pair production?

What is meant by pair production ? Explain with the help of an example and a balanced equation.

What is primary productivity? In what units would you express productivity?

What is primary productivity? Give the range of primary productivity in different ecosystems of the world.

What is primary productivity ? Giv a brief description of factors that affect primary productivity .

What is primary productivity? Give brief description of factors that affect primary productivity

What is the product B?