Question

The closest invertebrate relatives of chordates belong to the phylum:

• A. Mollusca
• B. Echinodermata
• C. Coelenterata
• D. Arthropoda

Hint:

Chordates and echinoderms are both deuterostomes—making echinoderms their closest invertebrate relatives.

Answer 1

The Correct Option is B

Chordates and echinoderms both belong to the group Deuterostomia, characterized by:
- Radial, indeterminate cleavage
- Development of the anus from the blastopore
- Similarities in embryonic development
This shared ancestry makes Echinodermata (e.g., starfish, sea urchins) the closest invertebrate relatives of chordates.
Other phyla:
- Mollusca and Arthropoda are protostomes.
- Coelenterata (Cnidaria) are more primitive and not closely related developmentally.

Answer 2

The closest invertebrate relatives of chordates belong to the phylum Echinodermata.

Echinoderms, such as starfish, sea urchins, and sea cucumbers, share several important features with chordates, which is why they are considered the closest invertebrate relatives. Both phyla are deuterostomes, meaning during embryonic development, the anus forms before the mouth.

Additionally, echinoderms and chordates share similarities in their larval stages, which are bilaterally symmetrical, unlike the radial symmetry of adult echinoderms. This bilateral symmetry during the larval phase indicates a common evolutionary ancestor.

Chordates are characterized by features such as a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail, which are not present in echinoderms, but their developmental and genetic relationships suggest they diverged from a common deuterostome ancestor.

Hence, among invertebrates, echinoderms are the closest relatives of chordates based on embryological development and evolutionary lineage.