lesson 24.1

CHAPTER 24: Echinoderms and Inveertebrate Chordates

24.1 ECHINODERMS

Introduction to the Echinodermata

Though they don't look alike, sand dollars, sea cucumbers, and sea stars are all echinoderms. Find out what they have in common with each other and with their ancient ancestors at this page from the University of California Museum of Paleontology.

 

Classification of the Extant Echinodermata

The classes, orders, and genera of echinoderms are listed at this California Academy of Sciences page. Several of the genera are represented with color photographs. The academy also features a page of Echinoderm Links to other institutions.

 

Bill Wasserman's Developmental Biology Page: Movies and Pictures

This page from Bill Wasserman, an associate professor of developmental biology at Loyola University in Chicago, links to several movies, including:

• Radial versus Spiral Cleavage: One characteristic that vertebrates share with the echinoderms is a radial cleavage pattern during embryogenesis. Compare it to the spiral cleavage pattern, which is found in flatworms, annelids, and most mollusks.
• Sea Urchin Gastrulation: Vertebrates and echinoderms are both deuterostomes--that is, their mouth develops after their anus. These picture show various stages of sea urchin gastrulation taken with a light microscope.
  

 

The Common Sand Dollar

This short article on the habits and life cycle of the sand dollar comes from the Gulf of Maine Aquarium.

24.2 INVERTEBRATE CHORDATES

Introduction to the Chordata

This page from the University of California Museum of Paleontology describes the characteristics, fossil record, and systematics of chordates. Within the Systematics of the Chordata and Their Allies section are the lancets, tunicates, hemichordata (acorn worms), echinoderms, and vertebrates. Visit this section to see pictures and descriptions of each group.

 

Sea Squirts

Learn more about the habits and features of the tunicates, as well as their role in the tide pool food web. This page and the others connected to it are from a project by the Woods Hole Oceanographic Institution.