Sea urchins and sand dollars are echinoderms that have a rounded body covered in sharp spines for protection. They have radial symmetry and can move their spines in response to stimuli like shadows or touch. They reproduce sexually through external fertilization. While they have a poorly developed respiratory system, they can take in oxygen through spines and have a water vascular system for movement and feeding without gills. Echinoderms are found along the sea floor where they eat algae and debris and are an important part of the marine food chain, though they try to avoid predators.

1. Sand dollars and sea urchins
ECHINODERMATA
Alissa Vite
Adaptations
If a sharp object were to hit a sea urchin then they
will point all their spines toward the area that was poked.
They are also light sensitive which means they can move
their spines in reaction to shadows. So they will not get
PLACE PHOTO HERE,
pulled away with the current they burry themselves in a
OTHERWISE DELET E BOX hole or crevasse.
General Structure
These creatures have a rounded or oval shape
Sea urchin flickr user poplinre body in most species they have long sharp spines that
protect them from predators. Also the underside of the
creature is flat and featureless.
Reproduction
Echinoderms reproduce sexually they are
either male or female, they relapse their eggs or sperm
into the water which will then be fertilized and that
causes larvae to develop that later settles to the
PLACE PHOTO HERE, bottom.
OTHERWISE DELETE BOX Respiration
They use bumps or spines on the surface of
their exoskeleton to take in oxygen. But they have a
poorly developed respiratory system.
Sand dollar by flickr user wildcat dunny
Type of Symmetry
Echinoderms have radial symmetry which
Some extinct animals in this group are means components are arranged around a central axis
carpoids they had their mouth on the side
of their bodies. Also another creature in a symmetrical manner.
that is extinct is cystoids. An endangered
is some sand dollars. Some oddballs are Responses to stimuli
star fish because of their shape and They can tell when there is a predator near them
feather stars because of their texture. through chemical signals stimuli responses include prey
Also sea cucumbers.
detection and predator avoidance but nature of stimuli
involved is not known.
This group is a phylum and the Regulation
kingdom it belongs to is Animala and the They are warm blooded and they live under water
domain of this group is Eukarya But they cannot live in fresh water. Most have hard outer
skeleton.

2. Continued
Echinodermata
Fickr user Eric Kilby
Place in food chain
Enchinoderms try to avoid their predators as
much as possible because they are easy prey to many OTHERWISE DELETE BOX
creatures. Mostly because most of their predators are
larger and faster than they are. But they are still a big
part of the food chain, they eat algae and detritus.
Transport
Echinoderms have a water vascular
system which is a network of fluid filled canals.
This system allows them to function without gills
or slits. They also have tube feet that suction to Additional Facts
things to help them move and catch prey.
• They are nocturnal
Nutrition
• Echinoderm means “spiny skin”
Sea urchins eat by gazing on the surface
of rocks and scraping algae off it these toothless • can regenerate parts
breeds may also eat smaller organisms that they
catch with their tube feet.
• can’t live in fresh water or on land
• 6,000 living species known in this phylum
Importance to us
• Most advanced group of invertebrates
When most people think of echinoderms
they think about the bad things like when walking • Range from a few mm to a few decimeters
in the sea to make sure you don’t step on one
because that would hurt them. But they have
some value to us they are a source of food not a • Sea stars are also in this group
popular food where we live but in other places it
is. They taste like a fruit and a sea food mixed • Sea cucumbers are also in this group
together.
• Brittle stars are also in this group
Background
The first universally accepted
echinoderms appear in the Lower Cambrian.
They left behind a distinct fossil and were said to S SOURCES
be short living. They appeared on earth five
http://en:wikipedia.org/wiki/Enchinoderm
million years ago. Yet there are many questions
that still remain about this group of animals. http://tolweb.org/treehouses/?treehouse_id=4881
www.biobull.org/cgi/content/full/20/12/175#SEC1
http://www.coolschool.ca/10r/BI11/unit14/U14Lo1.htm

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SOURCES
http://science.jrank.org/pages/6020/Sea-Urchins.html
http://www.starfish.ch/reef/echinoderms.html