Question

Compare three aspects of the early development of a snail (a mollusc) and a human (a chordate).

Short answer

Three main aspects can be used to differentiate snails and humans. The first trait includes symmetry that is snails exhibit spiral determinate cleavage while humans exhibit radial indeterminate cleavage.

The second trait includes the formation of the coelomic cavity by splitting the mesoderm mass while the coelom in humans forms an archenteron. The third trait includes the blastopore in snails forms the mouth, and the blastopore in humans develops into the anus.

Step-by-step solution

Cleavage differences between snails and human embryo

Based on symmetry exhibited by organisms, they can be grouped into different categories. Snails have a spiral determinate cleavage in which division takes place in a spiral manner. Humans have a radial determinate cleavage in which cleavage occurs at right angles from the previous division.

Coelomic cavity

In the early development of snails, the division of the mesoderm gives rise to a coelomic cavity. In the early development of humans, the mesoderm gives rise to an archenteron. The archenteron gives rise to the alimentary canal.

Blastopore

Blastopore is a cavity that is present within the embryo. The blastopore during the early development of snails gives rise to the mouth after the complete development has taken place. The blastopore during the early development of humans develops into the anus later on.