Which of the following is necessary to evolve a pureline in any animal?

Options

A. interspecific hybridization
B. Out-crossing
C. Cross-breeding
D. In-breeding

Answer

To determine which of the following is necessary to evolve a pure line in any animal, we need to analyze the options provided: interspecific hybridization, outcrossing, crossbreeding, and inbreeding.

### Step-by-Step Solution:

1. **Understanding Pure Line**: A pure line refers to a group of organisms that are genetically uniform, meaning they have the same alleles for a particular trait. This results in no genetic variation within that line.

2. **Identifying the Breeding Methods**:
- **Interspecific Hybridization**: This involves breeding between different species, which introduces new genetic material and variations. This does not help in creating a pure line.
- **Outcrossing**: This is the practice of breeding individuals from different genetic backgrounds within the same species. This also introduces new genes and variations, making it unsuitable for developing a pure line.
- **Crossbreeding**: Similar to outcrossing, crossbreeding involves mixing different breeds or varieties, which again leads to genetic variation.
- **Inbreeding**: This is the breeding of individuals from the same breed or genetic line over several generations (typically 4 to 6 generations). Inbreeding reduces genetic variation and helps in establishing a pure line.

3. **Conclusion**: Based on the definitions and implications of each breeding method, inbreeding is the only method that can lead to the evolution of a pure line in animals. Therefore, the correct answer is **inbreeding**.

### Final Answer:
The necessary method to evolve a pure line in any animal is **inbreeding**.

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