Here's why:
* Sex chromosomes: Females usually have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The X chromosome carries genes related to egg production.
* Reproductive organs: Females have ovaries, which produce eggs. Males have testes, which produce sperm.
While some species might exhibit unusual mating behaviors, such as seahorses where the male carries the eggs, the eggs themselves are still produced by the female.