What are the species in this group?
sea stars, brittle stars, feather stars, sea urchins, sea cucumbers
how do they breathe?
through their feet
Where are their eyes?
on the end on their arms
are they sessile or motile?
sessile or slow moving
Do they have specialised organs?
no they don’t have any specialised systems for excretion
What are the five main classes?
- Asteroidea
- Ophiruroidea
- Echinoidea
- Holothuroidea
- Crinoidea
what is the species in Asteroidea
starfish
What is the body wall of the Asteroidea ?
- endoskeleton composed of calcareous ossicles- spines are part of this
- pedicellariae: role in defence and predation
- papulae: specialised gills for respiration and waste removal
gas exchange and excretion in Asteroidea
- nitrogenous waste is removed through tube feet and papillae by diffusion which also allow for gas exchange
external features of Asteroidea
- penarmous with 5 tapering arms
- mouth located in centre under oral surface
- anus and madreporite present on aboral surface
what is the locomotion in Asteroidea like?
- water vascular system can be used to power the tube feet
- each hydraulic podium performs a stepping motion
feeding and digestion in Asteroidea
- they are scavengers and carnivorous
- detect pray rom susbstances released into water
what is the nervous system like in asteroidea
they lack a brain so they have a nervous system with the nerve ring that connects to radial nerves
what is regeneration and asexual reproduction like in Asteroidea
- any part can regenerate
- asexual reproduction involves division of central disc
- fertilisation is external
what are the animals in the Ophiuroidea group
brittle/basket stars
give some features of the Ophiuroidea group
- pentaradial symmetry
- distinct cental disc
- tube feet with no suckers
- vertebral ossilies- locomotion
- no pedicellariae or papillae
what animal is part of the Echinoidea group
sea urchins
give some features of the Echinoidea group
- no arms
- pentaradial symmetry
- roughly spherical to flat
- spines tube feet
- graze algae and decomposing animals
- gills
what animal belongs to the Holothuroidea group
sea cucumbers
Holothuroidea facts
- endoskeleton reduced to microscopic ossiles
- deposit/ suspension feeders
uses unique respiratory tree; branching tree inside anus for gas exchange
what animal belongs to the Crinoidea group
sea lilies
Crinoidea facts
- mainly sessile
- u shaped gut with anus next to mouth
- suspension feeders
- pentardial symmetry
