Which phylum is an example of protostomes with mouths forming from the blastopore?

Which phylum is an example of protostomes with mouths forming from the blastopore?

• A. Echinodermata
• B. Annelida
• C. Porifera
• D. Chordata

Answer: (B)

Annelida is the group that shows protostome development, where the mouth forms from the blastopore during early development. In protostomes, the cleavage is typically spiral and determinate, and the coelom forms by schizocoely, with the initial opening (the blastopore) becoming the mouth. Segmented worms like earthworms and leeches are classic examples of this pattern, so their mouth originates from the blastopore. Echinoderms are deuterostomes, meaning their blastopore usually becomes the anus and the mouth forms later or differently. Porifera are simple, non-gastrulating animals without this embryo pattern, and Chordata are also deuterostomes. Therefore, the phylum that fits protostomes with mouths forming from the blastopore is Annelida.

Annelida is the group that shows protostome development, where the mouth forms from the blastopore during early development. In protostomes, the cleavage is typically spiral and determinate, and the coelom forms by schizocoely, with the initial opening (the blastopore) becoming the mouth. Segmented worms like earthworms and leeches are classic examples of this pattern, so their mouth originates from the blastopore.

Echinoderms are deuterostomes, meaning their blastopore usually becomes the anus and the mouth forms later or differently. Porifera are simple, non-gastrulating animals without this embryo pattern, and Chordata are also deuterostomes. Therefore, the phylum that fits protostomes with mouths forming from the blastopore is Annelida.