Define ecological efficiency.

Explanation

**Step-by-Step Solution:**

1. **Understanding Efficiency**: Begin by understanding the general concept of efficiency. Efficiency refers to how well a system or process converts inputs into outputs, or how capable it is to perform work.

2. **Context of Ecology**: In the context of ecology, we are interested in how ecosystems utilize energy. This involves understanding how energy flows through different trophic levels in an ecosystem.

3. **Definition of Ecological Efficiency**: Ecological efficiency can be defined as the ratio of energy that is assimilated by organisms (energy that is converted into biomass) to the energy that is available to them (the total energy that enters the system).

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