| A | B |
|---|
| zygote | fertilized egg containing the diploid number of chromosomes |
| internal fertilization | union of egg and sperm in the moist tract inside a female |
| external fertilization | union of egg and sperm outside the body of a female |
| gastrulation | the indenting of the blastula |
| cleavage | rapid series of mitotic divisions in a developing zygote |
| blastula | a hollow ball made up of a single layer of cells |
| yolk | the embryo's source of food |
| amnion | a sac that surrounds the embryo |
| allantois | a storage site for nitrogeneous waste (uric acid) |
| chorion | a membrane that lines the inside of a shell that functions with the allantois in the exchange of respiratory gases |
| placenta | a temp. organ that forms from maternal and fetal material |
| umbilical cord | connects the embryo to the placenta |
| marsupial | pouched mammals |
