Final answer:
Reproductive cells such as spermatozoa and ova are called gametes, which are haploid cells with a single set of chromosomes. These unite to form a zygote, a diploid cell, marking the beginning of a new organism's life cycle.
Step-by-step explanation:
The reproductive cells such as spermatozoa and ova are termed gametes. These cells are characterized by having a haploid number of chromosomes, designated as 1n. This means that gametes carry only one set of chromosomes, in contrast to somatic cells, which are diploid (2n) and have two sets of chromosomes. In sexual reproduction, gametes from two parents unite during fertilization to form a zygote, which is a diploid cell containing two sets of chromosomes - one from each parent.
During the process of spermatogenesis in males, primary spermatocytes undergo meiosis to produce haploid sperm cells. Similarly, in females, oogenesis leads to the formation of haploid eggs. Gametes are crucial in the transfer of genetic information and diversity during sexual reproduction. The fusion of gametes results in a zygote that will undergo mitosis to develop into a multicellular organism.