Total gain in Biomass by an animal is known as

The correct option is Gross Secondary Productivity.

To understand why this is the correct answer, let us break down the concepts of ecological productivity step-by-step:

1. Primary vs. Secondary Productivity:
- Primary productivity refers to the rate at which solar energy is captured and converted into organic compounds (biomass) by producers, such as green plants and algae, through photosynthesis.
- Secondary productivity refers to the rate of biomass accumulation by consumers (animals, fungi, and decomposers) who obtain their energy by feeding on producers or other consumers.

2. Gross vs. Net Productivity:
- Gross refers to the total amount of energy or biomass captured/assimilated before any losses are accounted for.
- Net refers to the remaining energy or biomass after accounting for metabolic losses (mainly respiration). For instance, Net Secondary Productivity is the chemical energy in consumer biomass that is actually available to the next trophic level after respiration losses are subtracted from the gross intake.

3. Conclusion:
Since the question asks for the total gain in biomass by an animal (which is a consumer), we look at secondary productivity. Because it refers to the total gain (or ingestion/assimilation) before accounting for respiration losses, it is defined as Gross Secondary Productivity.