Question

what characters makes echinoderms as ancestors of chordates ?​

Answer 1

Explanation:

Chordates are eucoelomate deuterostomes, and probably share a common ancestor withechinoderms. Three important characteristics unite the Phylum Chordata. At some point in their life cycle, all chordates have a notochord, a dorsal hollow nerve cord, and pharyngeal gill slits.

Answer 2

Answer:

Explanation:

This is one of the classic hard problems in evolution. How is it possible that a species evolved into animals as different as starfish and people?

Echinoderm is the group containing starfish, sea urchins, sand dollars, sea cucumbers, and, sea lilies.[1]



We are chordates or vertebrates. We are more closely related to starfish than we are to worms, insects, snails, and other groups.[2] Biologists say that we are both Deuterostomes.



That’s surprising because echinoderms are oddly shaped. Starfish, in particular, have a five-sided symmetry while we have two-sided symmetry. How does evolution go from an animal having two sides to one having five?

It turns out that starfish start life as a two-sided animal and then morph into a five-sided one.[3]



The Bipinnaria and Brachiolara stages look a bit like other deuterostomes. It’s hard to guess what the common ancestor of all of these looked like. All deuterostomes have a common embryonic pattern in which a cavity appears in the middle and mouth and anus appear at opposite sides, so that’s a good starting point for thinking about the common ancestor.[4] Beyond that, it’s just guesswork.



Here’s one possible evolutionary scenario.[5] That makes the common ancestor look like the doliolaria stage of some echinoderms.



Here’s another possible evolutionary scenario.[6]



This chart shows a possible route for the evolution of the nervous system in deuterostomes with the diagram in the lower left showing a guess as to the structure in the common ancestor.[7]



Conclusion

People tell me that I am not supposed to say that Ontogeny Recapitulates Phylogeny. So, I won’t claim that you can trace the evolution of animals by looking at their embryos.



Still, thinking about embryos does help us understand how echinoderms came from bilateran ancestors.