The male and female reproductive systems are extremely different. Comparing and contrasting them in relation to one another shows these differences.
Inside Versus Outside
One major point of comparison is that a large amount of the male reproductive system is on the outside of the body, whereas the female reproductive system is mostly on the inside.
Sperm Versus Eggs
The male reproductive system produces sperm, which carry DNA information to the female eggs. Sperm are produced on a constant basis within the testicles. The female reproductive system, on the other hand, has thousands of eggs, which also carry genetic information. However, these are not produced on a constant basis. Rather, a woman is born with all the eggs she will ever need, and these are released into the uterus at the rate of approximately one per month.
When a male is sexually excited, his penis becomes larger and firmer by filling with blood. The same thing happens to women, except the clitoris becomes larger and firmer. The vagina also enlarges in order to accommodate the engorged penis.