1. “Spiny skin”

2. Introduction to Phylum Echinodermata Phylum Echinodermata is a group of invertebrates that includes sea stars, sea urchins, sea cucumbers, and sand dollars. Sea starSea urchinSea cucumber Sand dollar

3. Introduction to Phylum Echinodermata The members of this phylum are called echinoderms They inhabit marine environments ranging from shallow coastal waters to deep ocean trenches. They vary in diameter from 1cm to 1m and are often brilliantly colored Crown of thorns Starfish Patrick Patiria miniata (Bat Star)

4. Why is this phylum placed above the bilateral derived characteristic when they are obviously radially symmetrical?

5. Introduction to Phylum Echinodermata They start off life as bilaterally symmetrical larvae and develop into radially symmetrical adults. This feature of development indicates that echinoderms almost certainly evolved from bilaterally symmetrical ancestors. Step 1: Fertilization occurs Step 2: Each fertilized egg divides into bipinnaria Step 3: Free swimming and eats small plankton Step 4: It has arms and a suction. Star attaches to bottom of ocean and metamorphosis begins developing into pentaradially symmetrical adult

6. Introduction to Phylum Echinodermata The fossil record of echinoderms dates back to the cambrian period, more than 500 million years ago. Early echinoderms from this period appear to have been sessile, and biologists believe these animals evolved radial symmetry as an adaptation to a sessile existence. Echinoderms later evolved the ability to move from place to place. Today the vast majority of the 7,000 or so species can move by crawling slowly along the ocean bottom.

7. Introduction to Phylum Echinodermata Echinoderms are deuterostomes (radial cleavage; anus first). This means that they are animals in which embryonic development is controlled by genes and the 2 nd opening in the gastrula (embryo) becomes the mouth. In protostomes (spiral cleavage; first mouth; mollusks, annelids, arthropods), the 2 nd opening becomes the anus.

8. Why do Echinoderms and Chordates share a common ancester?

9. Introduction to Phylum Echinodermata Because both echinoderms and chordates are deuterostomes, it is likely that they have a common ancestor. Most echinoderms have a type of radial symmetry called pentaradial symmetry, in which the body parts extend from the center along five spokes.

10. Introduction to Phylum Echinodermata In addition to their pentaradial symmetry, echinoderms have three other major characteristics that are not shared by any other phylum: 1. They have endoskeleton composed of calcium carbonate plates know as ossicles. The ossicles may be attached to spines or spicules that protrude through th skin. In fact, the name echinoderm actually means “spiny skin”. 2. They have a water vascular system, which is a network of water-filled canals inside their body

11. Introduction to Phylum Echinodermata 3. They have many small, movable extensions of the water-vascular system called tube feet, which aid in movement, feeding, respiration and excretion. Phylum Echinodermata