Final answer:
An ovum carries 23 chromosomes, which is half the number of chromosomes found in somatic cells. This haploid number is due to oogenesis, which divides original diploid cells into haploid gametes in preparation for fertilization.
Step-by-step explanation:
In human oogenesis, an ovum carries 23 chromosomes. During this reproductive process, oogonia, which are diploid cells, undergo mitosis and meiosis to eventually form the ovum, a haploid gamete. The primary oocyte begins meiosis I early in life but pauses this process until puberty. Once the primary oocyte completes meiosis I, it divides into a secondary oocyte and a polar body, with the secondary oocyte containing most of the cytoplasm. Afterward, a secondary oocyte halts in metaphase II and only completes meiosis II if fertilization occurs, resulting in an ovum and another polar body.
The unequal distribution of the cytoplasm during oogenesis is specifically to provide the resulting zygote with the necessary resources as it only receives cytoplasm from the egg. The process ensures that only one cell, the ovum, is equipped with the abundant cytoplasm and organelles required to support the early stages of embryonic development.