A zygote initially develops into a hollow sphere, called a blastula, which undergoes rearrangement and differentiation. In sponges, blastula larvae swim to a new location and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber, and two separate germ layers — an external ectoderm and an internal endoderm. In most cases, a mesoderm also develops between them. These germ layers then differentiate to form tissues and organs.
A zygote initially develops into a hollow sphere , called a blastula , which undergoes rearrangement and differentiation . In sponges , blastula larvae swim to a new location and develop into a new sponge . In most other groups , the blastula undergoes more complicated rearrangement . It first invaginates to form a gastrula with a digestive chamber , and two separate germ layers — an external ectoderm and an internal endoderm . In most cases , a mesoderm also develops between them . These germ layers then differentiate to form tissues and organs .
What are the 2 germ layers formed by most blastula?
What are the 2 germ layers formed by most blastula ?
an external ectoderm and an internal endoderm
an external ectoderm and an internal endoderm