Name the form by which energy enters living system and leaves the system.

Explanation

**Step-by-Step Solution:**

1. **Identify the Energy Source for Living Systems:**
- Energy enters living systems primarily in the form of solar energy. This is the energy that plants capture through photosynthesis.

2. **Explain the Energy Transfer in the Ecosystem:**
- In an ecosystem, energy flows from one organism to another. For example, plants (producers) convert solar energy into chemical energy through photosynthesis. Herbivores (like deer) obtain energy by consuming plants, and carnivores (like lions) obtain energy by consuming herbivores.

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