The biomass available for consumption to heterotrophs and the rate formation of new organic matter by consumers are defined as
(a) gross primary productivity and net primary productivity respectively
(b) net primary productivity and gross primary productivity respectively
(c) gross primary productivity and secondary productivity respectively
(d) net primary productivity and secondary productivity respectively.

Options

A. gross primary productivity and net primary productivity respectively
B. net primary productivity and gross primary productivity respectively
C. gross primary productivity and secondary productivity respectively
D. net primary productivity and secondary productivity respectively.

Answer

To solve the question, we need to understand the definitions of the terms involved: gross primary productivity (GPP), net primary productivity (NPP), and secondary productivity.

1. **Understanding Gross Primary Productivity (GPP)**:
- GPP refers to the total amount of organic matter (biomass) produced by photosynthesis in a given area over a specific time period. It includes all the energy captured by plants.

**Hint**: Remember that GPP is all about the total production of organic matter during photosynthesis.

2. **Understanding Net Primary Productivity (NPP)**:
- NPP is the amount of organic matter that remains after the plants have used some of the energy for their own respiration. It represents the biomass available for consumption by heterotrophs (organisms that cannot produce their own food).

**Hint**: NPP is what is left for consumers after plants use some energy for themselves.

3. **Understanding Secondary Productivity**:
- Secondary productivity refers to the rate at which consumers (heterotrophs) convert the organic matter they consume into their own biomass. It is essentially the formation of new organic matter by consumers.

**Hint**: Think of secondary productivity as the productivity of consumers, converting what they eat into their own biomass.

4. **Analyzing the Options**:
- Option (a): Gross primary productivity and net primary productivity respectively - Incorrect.
- Option (b): Net primary productivity and gross primary productivity respectively - Incorrect.
- Option (c): Gross primary productivity and secondary productivity respectively - Incorrect.
- Option (d): Net primary productivity and secondary productivity respectively - Correct.

**Hint**: Focus on what each term means and match them with their definitions in the question.

5. **Conclusion**:
- The biomass available for consumption to heterotrophs is defined as net primary productivity (NPP), and the rate of formation of new organic matter by consumers is defined as secondary productivity. Therefore, the correct answer is option (d).

**Final Answer**: (d) net primary productivity and secondary productivity respectively.