Define sibling species. Give one example.

Explanation

**Step-by-Step Solution:**

1. **Definition of Sibling Species:**
Sibling species are defined as species that are morphologically similar, meaning they look almost identical to each other, but are reproductively isolated. This means that even though they may appear the same, they cannot interbreed and produce viable offspring.

2. **Reproductive Isolation:**
The reproductive isolation between sibling species can occur due to various factors, including geographical isolation (where species are separated by physical barriers like mountains or rivers) or habitat isolation (where species occupy different habitats within the same area). These isolating mechanisms prevent gene flow between the species.

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