Asteroidea

Question 1

Body plan

Answer 1

Body designed around plan of 5
Stomach in middle of animal, has digestive glands that process food down each one of the legs
Surface covered in pedicellaria - jaw-like structures that remove waste from body
Calcareous endoskeleton makes skin impervious - gas exchange function in excretion
-pupula are little bits of skin increasing SA for gaseous ex
Ambulacral ridge - where podia found

Question 2

Nervous system

Answer 2

Nerve net allows local control of parts - temporarily acting as a brain
Lead with a particular arm when wanting to move in that direction
Though nerve ring controls which leg leads but acc radial nerves and message via the ring

Question 3

Experiments on NS of Asteroidea

Answer 3

Scientists cut the central nerve ring so that some legs were separated and some still joined on nerve ring
Those not connected went in their own direction
Those still connected followed whichever leg was leading

Question 4

Feeding

Answer 4

If a starfish has short arms (i.e. cushion star) they swallow food whole
Longer limb starfish feed on prey like bivalves
1. Pry open shell using podia
2. Evert their stomachs into shell where digestion occurs
3. Then suck up the resulting products

Question 5

Acanthaster

Answer 5

Crow of Thorns starfish
-causes lots of damage as feeds on coral reefs
Over 27 years half of great barrier reef has been destroyed - ~40% by this starfish
Larval stage success depends on conditions - pop can explode
They are a species complex = different populations are very locally adapted (could be different spp) so difficult for controlling each group