The amount of energy reaching an upper trophic level is determined by

Options

A. net primary production.
B. net primary production and the efficiencies with which food energy is converte
C. gross primary production
D. gross primary production and the efficiencies with which food energy is converted to biomass.

Answer

**Step-by-Step Solution:**

1. **Understanding Trophic Levels**: Trophic levels refer to the different levels in an ecosystem where organisms obtain their energy. The primary producers (like plants) are at the first trophic level, followed by primary consumers (herbivores), secondary consumers (carnivores that eat herbivores), and so on.

2. **Energy Flow in Ecosystems**: Energy flows from one trophic level to another. The sun is the primary source of energy for most ecosystems. Plants (primary producers) convert sunlight into chemical energy through photosynthesis.

3. **Energy Transfer Efficiency**: Not all energy from one trophic level is transferred to the next. Typically, only about 10% of the energy is passed from one level to the next due to energy loss through metabolic processes, heat, and waste.

4. **Factors Affecting Energy Transfer**: The amount of energy reaching an upper trophic level is influenced by:
- The efficiency of energy transfer between trophic levels.
- The total energy captured by primary producers.
- The number of organisms at each trophic level.

5. **Conclusion**: Therefore, the amount of energy reaching an upper trophic level is determined by the total energy captured by primary producers and the efficiency of energy transfer through the food chain.

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