Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Explain the differences in animal body plans that support basic animal classification
Compare and contrast the embryonic development of protostomes and deuterostomes

You're probably familiar with starfish and sand dollars. They are both echinoderms. Sea urchins and sea cucumbers are also echinoderms. What's similar between these three organisms? They all have radial symmetry. This means that the body is arranged around a central point. Learn more about echinoderms in this learning module produced by CK-12.

A free CK-12 account is required to view all materials.

An explanation from Teachers Network of what rotational symmetry is along with some examples that show this.