EVERYDAY SCIENCE

Detailed explanation-1: -Sea stars are echinoderms, which means that they belong to the animal kingdom, just like chordates do. In addition, sea stars and chordates are both bilaterally symmetrical deuterostomes, a grouping of animals that arose about 540 million years ago.

Detailed explanation-2: -Alternatively, in protostomes the first aperture, also known as a blastopore, develops to form the mouth. Both echinoderms and chordates show this characteristic trait. Thus, it is assumed that the two might have a common ancestor and are considered closer than any other phylum.

Detailed explanation-3: -Echinoderms are considered closer to chordates because, like chordates, they are deuterostomes i.e., the anal region develops earlier than the mouth region. Their larvae are also closer to protochordate.

Detailed explanation-4: -Sea stars are invertebrates related to sea urchins, sea cucumbers and sand dollars, which are all echinoderms. Echinoderm means spiny skin-a reference to their hard, calcified skin, which helps to protect them from predators. Sea stars have rows of tiny tube feet extending from the grooved surface on their underside.