How do lower organisms like yeast respire?

Explanation

### Step-by-Step Solution:

1. **Understanding Yeast Respiration**: Yeast, a lower organism, can respire in two ways: aerobic respiration and anaerobic respiration.

2. **Aerobic Respiration**: When oxygen is available, yeast performs aerobic respiration. This process occurs in the mitochondria of the yeast cells. During aerobic respiration, glucose is broken down with the help of oxygen to produce energy, carbon dioxide, and water.

3. **Anaerobic Respiration**: In the absence of oxygen, yeast resorts to anaerobic respiration. This process occurs in the cytoplasm of the yeast cells. Instead of using oxygen, yeast breaks down glucose through fermentation, resulting in the production of energy, ethanol, and carbon dioxide.

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