| A | B |
|---|
| development | the series of events that gives rise to a fully developed organism |
| embryo | the early stages of development of an organism are referred to as this |
| cleavage | after fertilization, the series of cell divisions. During this set of divisions, there is no growth of cells and each division decreases cell size |
| morula | embryo stage when a solid ball of cells exist |
| blastula | embryo stage when cells rearrange to form a hollow sphere |
| blastocoel | fluid filled cavity in blastula |
| gastrulation | the process in which the cells on one side of a blastula move inward to form a two layered gastrula |
| gastrula | in animals, embryo stage when second germ layer is formed |
| blastopore | the opening in the gastrula created by the gastrulation process; become an opening to the digestive system |
| ectoderm | outer layer of gastrula |
| endoderm | inner layer of gastrula |
| primitive gut | cavity in gastrula that eventually becomes digestive system |
| mesoderm | third germ layer of embryo that gives rise to bones, musc, blood, etc. |
| germ layers | ectoderm, endoderm, mesoderm-layers that give rise to all the tissues & organs of multicellular organisms |
| differentiation | the changing of uspecialized cells into specialized cells, tissues, and organs |
| embryonic induction | the process by which one group of cells(the organizer) induces another group of cells to differentiate |
| extraembryonic membranes | in shelled eggs of reptiles and birds, any one of four membranes outside the embryo but inside the shell |
| chorion | lines inside of shell and surrounds embryo and other extraembryonic membranes |
| allantois | saclike structure that grows from digestive tract of embryo; through its blood vessels gases are exchanged |
| anmion | membrane that surrounds embryo; fluid filled; cushions embryo & protects it from shock |
| yolk sac | contains source of food for embryo |
