Cleavage and Blastula Formation
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Cleavage divides a fertilized egg rapidly through mitosis without overall growth, producing a solid ball of smaller cells that hollows into a blastula past roughly a hundred cells.
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Cleavage divisions occur so fast the embryo's total size barely changes despite the rising cell count.
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Cleavage divides cell number without growing total mass, unlike ordinary mitotic growth elsewhere in development.