Question

Embryos of protostomes are called:

• A. Regulative embryos
• B. Positive embryos
• C. Mosaic embryos
• D. Radial embryos

Hint:

Protostomes = mosaic embryos (early cell fate fixed); Deuterostomes = regulative embryos (early cell fate flexible).

Answer 1

The Correct Option is C

- In protostomes, embryonic development is determinant and spiral.
- Their embryos are called mosaic embryos because each cell’s fate is determined early; removing a cell will result in an incomplete organism.
- In contrast, deuterostomes (like chordates) form regulative embryos, where the early embryo can compensate for cell loss.

Answer 2

Embryos of protostomes are called:

Protostomes are a group of animals characterized by their pattern of embryonic development. One key feature is the type of cleavage during early embryogenesis, which is typically spiral and determinate. Because of this determinate cleavage, the fate of each embryonic cell is fixed early on, meaning that if a cell is removed, the embryo cannot compensate by replacing that cell.

Due to this, protostome embryos are called mosaic embryos. This term refers to the idea that the embryo is like a mosaic artwork, where each piece (cell) has a specific role and contributes to a fixed part of the organism’s body plan. Damage or removal of any one cell can result in loss of that part.

This contrasts with deuterostomes, whose embryos show indeterminate cleavage and are called regulative embryos because cells have the ability to adjust their developmental fate.

Correct Answer: Mosaic embryos