Differentiate innate and acquired immunity.

Explanation

### Step-by-Step Solution:

1. **Definition of Innate Immunity**:
- Innate immunity is the first line of defense against pathogens and is present at the time of birth. It consists of physical barriers (like skin), physiological barriers (like pH levels), and cellular components (like phagocytes).

2. **Definition of Acquired Immunity**:
- Acquired immunity, also known as adaptive immunity, develops after birth and is gained through exposure to pathogens. It involves a primary immune response when the body encounters a pathogen for the first time, leading to the formation of memory cells.

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