* Echinoderm means _______________. All echinoderms have spiny skin.

•There are ______ characteristics of echinoderms.

•All echinoderms have:• Spiny skin• An internal skeleton (endoskeleton)• Five-part radial symmetry• A water vascular system• Tube feet

They live in the ocean!

* All echinoderms have __________. Some of them have small hair-like spines, like the starfish.

* Some echinoderms have long spines, like the sea urchin.

* The internal skeleton of an echinoderm is made of _______________________.

* The water vascular system also helps an echinoderm _____.

* An echinoderm’s water vascular system is _________________________________.

* The system opens to the outside through the sieve like madreporite.

Madreporite •Opening to the outside

•Connects to a ring canal around the mouth

•5 radial canal extend up the arms from the ring canal

* Echinoderms have __________.

* An echinoderm’s tube feet are used for _________________________________.

*Five-part radial symmetry.

* But the bodies are 2-sided. Mouth side is the oral surface & the opposite side is the aboral surface.

*They have no anterior or posterior end and lack ______________.

Plan for the Day

•Review unifying characteristics of Echinoderms

•Examine 5 classes of the Phylum Echinodermata

•Check your understanding activity

•* Mollusc & Echinoderm test - WEDNESDAY

5 Classes of Echinoderms

•Asteroidea

•Echinoidea

•Ophiuroidea

•Holothuroidea

•Crinoidea

* Carnivores: use tube feet to move

and to open bivalves to eat

* A sea star is able to re-grow its arms

Class Echinoidea

Sea urchins & sand dollars* Have solid plates surrounding their

internal organs

*Most are detritivores or grazers.

* Sea urchins have a mouth hidden under its body and they eat sea algae (kelp).

* A sea urchin is not very active. Sometimes, it does move slowly using its __________. When not moving it uses its feet to stick to the ocean floor.

* Sea urchins have longer and sharper ________ that they use to protect themselves.

Class Ophiuroidea

Brittle Stars

* Have slim, flexible arms, and can move quickly. Can detach an arm if being attacked!* Filter feeders and detritivores that come out at night

Class Holothuroidea

Sea cucumbers

* Feed on detritus

* Can expel all their internal organs as a decoy if being attacked!

Class CrinoideaSea

lilies & feather stars

* Oldest echinoderms

* Filter feeders: attach to the seafloor by a stock and use their tube feet to catch prey

Echinoderms: Form & Function

Feeding

Respiration

Circulation

Excretion

Response

Movement

Reproduction

FeedingSea urchins: five-part jaw to eat algae

Sea stars: tube-feet to pry open mollusks shells. Evert their stomach into the mollusk shell and secretes digestive enzymes. Brings stomach and digested food back inside. (digests externally)

Sea cucumbers: eat sand & detritus on the ocean floor or filter feed

Sea lilies: tube-feet to trap plankton

Respiration & Circulation**Water vascular system** - primary system

•Carries oxygen, food and wastes*Tube-feet allow some diffusion through thin walls for respiration (gas exchange)

*Skin gills are present in some echinoderms for gas exchange

*Sea cucumber: pumps water in and out of its anus to provide oxygen to its respiratory trees

Excretion

Nitrogen-containing wastes are excreted through thin-walled tube feet

Digestive wastes (feces) are released through the anus

ResponsePrimitive nervous

system (no brain)

Nerve ring surrounding the mouth connects to radial nerves to the body segmentsSenses: to detect light, gravity and chemicals

Movement

Tube feet ! – All use tube feet to move (water-vascular system) - hydraulics

Sea stars & brittle stars move arms because of flexible joints

Sand dollars & sea urchins move their spines

Sea cucumbers move using muscular wall & tube feet

ReproductionExternal fertilization

•Eggs produced in ovaries & sperm produced in testes

•Gametes released into the water for fertilization

•Larvae are free swimming

ReproductionRegeneration

Sea stars can regenerate: must contain part of the centre ring

Echinoderm EcologyUrchin Barren: created by

overpopulation of urchins

Sea stars are predators and help control the growth of mollusks (mussels) & corals

Echinoderm EcologyThreat to coral reefs: sea star

called crown-of-thorns

Feeds on coral and has destroyed coral reefs in Australia

Review Questions

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