Each higher trophic level in a food chain can utilize only ............of energy.

Explanation

**Step-by-Step Solution:**

1. **Understanding Trophic Levels**: In an ecosystem, organisms are arranged in a hierarchy known as trophic levels. The first level consists of producers (like plants), followed by primary consumers (herbivores), secondary consumers (carnivores), and so on.

2. **Energy Transfer in Food Chains**: Energy transfer occurs as one trophic level consumes another. However, not all the energy from one level is passed on to the next.

3. **The 10% Rule**: According to the 10% rule, only a small fraction of energy (approximately 10%) from one trophic level is transferred to the next level. This means that when energy is passed from producers to primary consumers, only about 10% of the energy is utilized by the primary consumers.

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