Define external fertilization. Mention its disadvantages.

Explanation

### Step-by-Step Text Solution

1. **Definition of External Fertilization**:
- External fertilization is the process where fertilization occurs outside the female's body. This typically involves the release of gametes (sperm and eggs) into the external environment, usually water, where they can meet and fuse to form a zygote.

2. **Medium Required**:
- For external fertilization to occur, a medium is required for the sperm and egg to meet. In most cases, this medium is water, which facilitates the movement of gametes.

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