Hello, @Janine.

Both refer to the process of formation (derived from Greek: genesis) of gametes. "Oo" refers to the female gametes, the process from oogonia to eggs or ovules. "Spermato" refers to male gametes, the process from spermatogonia to spermatozoa.

The differences are very obvious at the histological level. In practical terms the female gametes become larger through the maturation process, while in males the process is reversed and the gametes become smaller. Example small female gonia (oogonia), but large male gonia (spermatogonia). In contrast, the mature gamete is large in females (ovum or egg) but in males the mature gamete is small (sperm).

You could see some of my invertebrate work.

Cheers,

Omar

oogenesis is the terminal differentiation of a ovarian germ cell (called oogonium) to a cell called oocyte. This is the dead end. This oocyte is a female germ cell. It must die unless it gets fertilized by a sperm in oviduct or in a dish (in vitro fertilization).

Spermatogenesis starts in testis, where, cells called spermatogonium differentiate to terminal cell called sperm. Sperm will die in several hours unless it can enter Oocyte and fertilize oocyte

you can see many diagrammatic sketches in Google on this topic