Phylum Echinodermata

Question 0

Sea urchins & sand dollars

Answer 0

• long solid plates around internal organs
• sand $ burrow for protection
• sea urchins protected by spines

Question 1

7 characteristics

Answer 1

• 5-part radial symmetry
• internal skeleton
• water vascular system
• tube feet
• marine
• complete digestive tract
• coelomates

Question 2

Sea stars

Answer 2

• creep slowly on ocean floor
• mostly carnivorous (prey on bivalves)
• can regenerate body parts (if central disc is included)

Question 3

Brittle stars

Answer 3

• slender, flexible arms
• move rapidly to escape predators
• can shed arms when attacked
• can regenerate
• nocturnal

Question 4

Sea lillies and feather stars

Answer 4

• aka crinoids (ancient class)

- perch on reefs & capture plankton with tube feet

Question 5

Sea cucumber

Answer 5

• detritus feeders (suck organic matter)

- 5 rows of tube feet along body display radial symmetry

Question 6

Movement

Answer 6

• sand $ and sea urchins have protective spines on their fused exoskeletons
• sea stars and brittle stars have flexible arm joints
• sea cucumber has plates reduced to ossicles/spicules in body wall

Question 7

Describe how water vascular system aids movement

Answer 7

• water enters through maldreporite
• goes through stone canal
• enters ring canal
• enters radial canals
• enters tube feet
• muscles pull tube feet upwards and suction cup pressure is created

Question 8

Respiration

Answer 8

• diffusion across thin tube feet tissue (lots of surface area)

Question 9

Feeding

Answer 9

• herbivores (sea urchin) use 5-part jaw-like structure to scrape algae from rocks
• carnivores (sea star, brittle star) pry apart bivalve shell externally & absorbs partially digested food
• scavengers (sea cukes) vacuums ocean floor taking in sand & detritus
• filter-feeders (sea lillies) wave tube feet to capture floating phytoplankton

Question 10

Reproduction

Answer 10

• most are separate sexes
• external fertilization
• bilateral free-swimming larvae

Question 11

Internal circulation

Answer 11

• nutrients and wastes removed from body by water vascular system

Question 12

Excretion

Answer 12

• feces removed through anus

- ammonia/nitrogen wastes diffuse through water vascular system & tube feet

Question 13

Response to environment

Answer 13

• no head
• poorly developed nervous system
• has nerve ring around mouth & radial nerves
• scattered sensory cells to detect light, gravity, etc.

Question 14

Pedicillaria

Answer 14

Pincher like structure that keeps surface of organism free of debris

Question 15

Ampulla

Answer 15

Bulb-like sac on tube feet that squeezes to control amount of water

Question 16

Ambulacral groove

Answer 16

Trench along oral surface of sea stars arms- holds tube feet