How does diploidy help to preserve genetic variation?

By propagating both, Dominant and recessive alleles.

Explanation:

During evolution, only dominant traits transfer up to the next generation due to their better adoption in the environment but diploidy helps in hetrozygous arrangement of allele (A a) that contain both the dominant and recessive alleles. As a result, the genetic variations of both alleles gets preserved.

its the cell wall and the they are unique to plant

common management practices in dairy and poultry farming are: (i) proper shelter facilities and their regular cleaning. (ii) some basic hygienic conditions such as clean water, nutritious food, etc. (iii) animals are kept in spacious, airy, and ventilated place.