Why do we need 2 sets of a single chromosome?

Haploid sex cells, or cells with only one set of chromosomes, are called gametes.

It is important to note that, from the perspective of natural selection, every new generation should evolve and "improve" with respect to the previous generation. When two gametes fuse (i.e., fertilization), then the maternal set of chromosomes comes together with the paternal set of chromosomes. From there, some dominant genes of the father and some dominant genes of the mother are expressed.

You have two sets of chromosomes for a very important reason. Since your name is Peter, I'll assume that you're a man. The types of your 23rd chromosome determine your sex, or gender.

You can ask yourself, "So why do we not just have a single X chromosome for females and a single Y chromosome for males?" If you have an XX arrangement, you are a female; if you have an XY arrangement, you are a male.

The explanation is that males require the X chromosome to survive, whereas the Y chromosome "modifies" or changes their sex. This is because the Y chromosome is much smaller than the X chromosome and does not carry certain genes that the X chromosome has.

Although there are many more reasons to have two sets of chromosomes, I believe this will suffice for you.

We need two sets of chromosomes for several reasons, including genetic diversity, redundancy, and stability during cell division. This arrangement helps ensure the proper functioning of cells and organisms, and it provides a backup in case of genetic mutations or errors.