Because since their ancestors came before them then they inherit certain beneficial traits that help them survive. Those traits are in the DNA and the animals are evolving to be more fit for the environment that they are in. (hope this helps)
Punnett squares are used to find out the possible genotypes of the next generation after a cross and thus find the phenotype too according to the predicted genotypes.
For example, parents with genotypes of Rr and rr cross together, we can use the punnett square to list out the possible genotypes of their children which are Rr and rr.
You can never predict the exact genotypes of the next child but you can find out the possibility if they carry a certain trait. All the genotypes of the child are in random but you at least know what phenotypes they'll have.
Answer:
The result of mitosis is two identical daughter cells, genetically identical to the original cell, all having 2N chromosomes. ... A chromatid, then, is a single chromosomal DNA molecule.