Bio 108 Topic 25

Which two phyla are in Deuterostomia?

Echinodermata and Chordata.

What unites deuterostomes?

Deuterostome embryonic development and molecular similarities.

What kinds of animals are echinoderms?

Marine species like starfish, brittle stars, sea urchins, sea cucumbers, sea lilies.

What symmetry do echinoderms have?

Adults = (usually) pentaradial symmetry; larvae = bilateral symmetry.

What is their skeleton made of?

Endoskeleton of calcareous ossicles, sometimes forming spines.

Describe their nervous system.

Diffusion with no central brain

How do echinoderms reproduce?

Separate sexes, external fertilization by broadcast spawning; larvae are planktonic.

What is the water vascular system?

A hydraulic system derived from the coelom used for movement and feeding.

Components of the water vascular system?

Ring canal, radial canals, tube feet (ampulla + podium), madreporite (entry point for water).

Asteroidea (Starfish):

• Predators (often on molluscs).

• Use tube feet to pry open prey.

• Evert stomach to digest prey externally.

Echinoidea (Sea Urchins):

• No arms, but 5 rows of tube feet.

• Use spines (ossicles) to move.

• Herbivores (graze algae).

Holothuroidea (Sea Cucumbers):

• Elongated body (2° bilateral symmetry).

• Deposit/filter feeders.

• Lack spines; reduced skeleton (scattered ossicles).