PBS
Nova: How Is Sex Determined?
The sex of an egg cell is set as soon as it is fertilized, but what happens to that cell and the cells it divides into to make a baby boy or a baby girl? In this interactive, see how gonads-which look identical in early-stage...
CK-12 Foundation
Ck 12: Life Science: 10.17 Bird Reproduction
Learn about the reproduction of birds.