Deuterostomes: Echinoderms and Chordates

Deuterostomes

• Deuterostomes include Echinoderms and Chordates.
• Characterized by radial cleavage and formation of the anus from the blastopore.

Echinoderms

• Echinoderms have spiny skin and are all marine.
• They are slow-moving or sessile with a thin epidermis over calcareous plates.
• Possess a hydrovascular system and move via tube feet.
• Examples: sea stars, brittle stars, sea urchins, sea lilies/feather stars, and sea cucumbers.

Hemichordates

• Include acorn worms.

Chordates

• Chordates possess a notochord, a dorsal hollow nerve cord, pharyngeal slits or clefts, and a post-anal tail.
• Chordates first evolved in the Cambrian explosion about 530 million years ago.

Major Chordate Groups

• Vertebrates: Defined by having vertebrae.
• Urochordates: (Tunicates) possess a notochord, dorsal hollow nerve cord, and tail in their larval stage.
• Cephalochordata: (Lancets) have a notochord and dorsal nerve cord.