Chapter 28, Problem 20STP

Summary Introduction

To hypothesize:

Echinoderms have continued living in the ocean while other invertebrate groups have migrated to fresh water and land.

Introduction:

Echinoderms are the group of marine animals that contains spiny skin. There are found on the sea depths with a wide variety of colours. They got star−like appearance and are their skeleton is made up of calcium carbonate. Example: Starfish, Sand dollars.

Explanation of Solution

Echinoderms are the group of marine organisms that live in the ocean. Echinoderms like sand dollars, sea urchins, etc. are sometimes visible on the seashore. They are found in ocean depth from intertidal to abyssal zone as this depth provide them all the conditions required for their survival like food, temperature and shelter.

Conclusion

Echinoderms have continued living in the ocean while other invertebrate groups have migrated to fresh water and land as echinoderms need a certain environmental condition to live in. hence they are mostly found in in ocean depth from intertidal to abyssal zone.