The Basics:Echino” – Spiny, “Derm” – SkinMany have spiny skin (i.e. Sea urchins, or the inner skeleton of sea stars) yet many carry out not.Appeared between 541-488 Million Years ago (Cambrian explode – same as chordates)Coelomates v deuterostome development.

You are watching: Liquid that fills an echinoderms vascular system

Most very closely related phylum to chordates!


A. Evolution of human body Plan

1. Deuterostome development

During embryonic breakthrough the blastopore develops into the anus.Largest team of deuterostomes external of Chordates

2. Water Vascular System

Unique system of fluid-filled canals and also tubes that aid with feeding, movement and respiration.Only uncovered in echinoderms.

Major components of the water vascular system:

Tube Feet – have a ampullae a “balloon” that fills v water causing the foot v a suction cup come extend and stick come prey/ground.Sieve Plate – The entrance for water into the water vascular system (also dubbed a madreporite).Ring Canal – main canal whereby all canals branch from.

3. Endoskeleton – constantly covered in a thin layer the skin as such it is a endoskeleton (like us!)

Made that calcium carbonateCan it is in loosely linked for movement (sea stars)Fused to form a rigid skeleton (sea urchins)

4. Radial the contrary – Symmetry approximately a main axis. In echinoderms they have 5 symmetrical part (pentaradial symmetry)

Important Note:

It is crucial to note that echinoderms emerged from a bilateral ancestor and also developed radial the opposite secondary.

We deserve to see this in their larval stages which room all bilaterally symmetrical!

B. Feeding and also Excretion

One-Way cradle system

Typically have actually two stomachs – a cardiac stomach which can be moved exterior of the body start digestion and a pyloric stomach.

Due come this, sea stars can digest food much bigger than your stomach since they begin digestion outside their body.

Powerful enzymes liquify food – digested fully within the stomachs.


Digestive waste exits the anus ~ above opposite next of mouth.No distinctive excretory offal – nitrogenous rubbish is eliminated from the water vascular mechanism via diffusion v tube feet or with digestive waste.C. Respiration and Circulation


Use water vascular system in respiration and circulation.Gas exchange occurs through straightforward gills and diffusion through tube feet.


Reduced circulatory system.All fluids and also “blood” circle transparent the hydraulic-like water vascular system. Blood has no colors (i.e. No colour)No heart!

D. Reproduction

Sexual Reproduction:

Male and female are different individuals.External fertilization through broadcast spawningFemales can release up to 100 million egg at one time.

Sexual Reproduction – brief life cycle:

Fertilized embryo develops into bilateral, planktonic larvae.

The planktonic larvae gradually adjust into radially symmetry adults under the course of two-months and settle ~ above the ocean floor.

Asexual reproduction:

Asexual reproduction with fragmentation or fission (rare)Due to repetition of offal in each area and a nerve disk, echinoderms have the right to regenerate if castle are fragmentised with a piece of their central disk.

E. Significant Groups the Echinoderms

Class Asteroidea (Sea Stars)

PredatoryTwo-stomachs (pyloric and also cardiac)5 or much more arms that are broad near the main disk and gradually obtain thinner.

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Class Opiuroidea (Brittle Stars)

5 or more thin, flexible arms.Many space filter feeders.All organs in central disk – no in arms

Class Echinoidea (Sea Urchins)

Round body covered in spinesHard, fused endoskeleton

Class Holothuroidea (Sea Cucumbers)

Appear bilaterally symmetrical, back they space still radially symmetrical (dorsal-ventrally stretched).Tube shame detritivores.