Question

How does sexual reproduction occur?

Answer 1

Sexual reproduction is the formation of a new individual following the union of two gametes.

Copulation and Fertilization:
For fertilization to occur, sperm must be deposited in the vagina within a few (5) days before or on the day of ovulation. Sperm transfer is accomplished by copulation. Sexual excitation dilates the arterioles supplying blood to the penis. Blood accumulates in three cylindrical spongy sinuses that run lengthwise through the penis. The resulting pressure causes the penis to enlarge and erect and thus able to penetrate the vagina.
Movement of the penis back and forth within the vagina causes sexual tension to increase to the point of ejaculation. Contraction of the walls of each vas deferens propels the sperm along. Fluid is added to the sperm by the seminal vesicles, Cowper's glands, and the prostate gland.
The mixture of sperm and accessory fluids is called semen. It passes through the urethra and is expelled into the vagina. Once deposited within the vagina, the sperm proceeds on their journey into and through the uterus and on up into the fallopian tubes. It is here that fertilization may occur if an "egg" is present.