| Type of cleavage |
Asymmetrical |
Symmetrical |
| Orientation of cleavage |
Diagonal or oblique to the animal-vegetal axis |
Perpendicular or parallel to the animal-vegetal axis |
| Cleavage pattern |
Cells divide at an angle to the previous division plane |
Cells divide either directly above or below the previous division plane |
| Development of blastomeres |
Cells of one hemisphere are shifted with respect to the other hemisphere |
Cells are relatively symmetrical in relation to each other |
| Fate of blastomeres |
· Indeterminate
· Different developmental fates for different cells |
· Determinate
· Initially similar developmental fates for all cells |
| Embryonic morphology |
Often leads to a spiral arrangement of cells |
Radial symmetry in the early embryo |
| Regulative development |
Less regulative development; removal of blastomeres may affect the final structure |
More regulative development; removal of blastomeres may not severely affect the final structure |
| Examples |
· Mollusca
· Annelida
· Some other protostomes |
· Echinodermata
· chordates |
| Cleavage type in humans |
Not present in humans |
Present in early stages of human embryonic development |
