Eggs or female reproductive cells are formed well before birth in a huge number (primordial oocytes). But, the number of oocyte decreases after birth constantly (there are 2 million oocytes at birth and 40,000 of them in puberty). At menopause, no egg cells are left.
On the other hand, the first sperms are formed only from puberty, but the production of those cells never stops.
The reason why cells is the basic unit of structure and function in all living things is because the cells form parts for the organism and it carries out all of the organism's processes or it's functions.
<span>The phase of mitosis during which the mitotic spindle begins to form is PROPHASE.
</span>At prophase, the nuclear envelope is broken down; the chromosomes disperse into the cytoplasm, condenses and become visible; and more importantly, the mitotic spindle fibers form.
