Group Deuterostomia / phylum echinodermata

Question 1

What kind of classification is this group based on?

Answer 1

DNA evidence

Question 2

What are 2 common traits within this group?

Answer 2

• they are all triploblastic with 3 germ layers

- they all have a radial, indeterminate cleavage (you don’t know what each cell is going to be)

Question 3

What are the two phylum in this group?

Answer 3

Echinodermata and chordata [sister taxa with the same common ancestor] DID NOT evolve from one another

Question 4

What species are in phylum echinodermata?

Answer 4

sea stars, sea urchins, sea lilies, and sea cucumbers

Question 5

What are kind of exoskeleton do echinodermata have? and what is it good for?

Answer 5

• they have calcareous (calcium-carbonate) exoskeleton that is well suited for fossilization

Question 6

What are 5 basic characteristics?

Answer 6

1. slow, sessile and marine
2. adults have pentatlaterial symmetry (5 sided radial symmetry)
3. Larvae have bilateral symmetry
4. Mouth is located at the centre of arms and faces downwards
5. Contain a thin epidermis that covers the endoskeleton (muscles)

Question 7

What is the only species of echinodermata that is bilateral?

Answer 7

sea cucumber

Question 8

What is the water vascular system and how does it relate to tube feet?

Answer 8

the water vascular system is a network of hydraulic canals that branch into extensions called tube feet

• the water gets in through the mad reporite and then pumped from podium into the ampulla (suction cups at the tips) and then flows back out the mad reporite
• this creates a water pressure that allows the creature to stick via adhesion to a surface, and tube feet allow it to move

Question 9

What are the functions of the tube feet?

Answer 9

• used for locomotion, feeding and gas exchange

Question 10

Do echinodermata have a brain? if not, what do they have?

Answer 10

1. they have a nervous system but no central brain

Question 11

What are the reproductive qualities of echinodermata?

Answer 11

1. usually separate sexes
2. both sexes engage in broadcast spawning which is releasing the eggs and sperm into the water and fertilization occurs in open water
3. larva is planktonic (small and weak)

Question 12

What is the name of the 3 out of 5 classes of echinodermata? How do they differ?

Answer 12

1. Class Asteroidea
2. Class Echinoidea
3. Class Holothuroidea

• they differ by morphology and activity

Question 13

Describe the general characteristics of Class Asteroidea?

Answer 13

1. Sea stars and star fish
2. they have 5 or more arms (radial symmetry)
3. Active non-sessile and walk via tube feet
4. predatory
5. use tube feet to open bivalves (clams)
6. Adhesion due to glue NOT suction

Question 14

Describe class Echinoidea?

Answer 14

1. incl. sea urchins, sand dollars
2. no arms
3. five rows of tube feet
4. slow moving
5. spines that are used for locomotion and protection
6. eat seaweed (herbivores)

Question 15

Describe Class Holothuroidea?

Answer 15

1. incl. sea cucumbers
2. bilateral symmetry
3. Elongated –> 5 rows of tube feet and the tube feet around the mouth serve as feeding tentacles
4. deposit or suspension feeders (walk on group and eat things off of ocean ground floor)
5. shoot out their internal organs if they’re disturbed

Question 16

What is the ecology of echinodermata species?

Answer 16

• sea starts are important intertidal predators and they have a large impact on intertidal species because they keep lower species in check
• their larvae serve as food (bc they are planktonic) for many marine animals
• sea cucumbers are food for humans
• important models for deuterostome style development because they are simple structures