ECHINODERMATA

By: Laura Hein, Jaeyoung Kim

Period 3

Rall

http://www.palaeos.org/images/thumb/5/5a/Acanthaster_planci.jpg/340px-Acanthaster_planci.jpg

Phylum: Echinodermata• Classes:

– Ophiuroidea: brittle stars

– Asteroidea: Sea stars

– Echinoidea:– sea urchins– sand dollars

http://people.hws.edu/mitchell/cards01/LEI2.html

• Classes: cont.

– Crinoidea: sea lillies

– Holothuroidea: sea cucumbers

http://people.hws.edu/mitchell/cards01/LEI2.html

Body cavity (coelom) -Echinoderms form their coeloms as outpocketings from the archenteron (embryonic gut), -process=enterocoely. -In most species, the coeloms are trimerous, and initially bilaterally symmetrical. -some coelom departments are similar and may reflect a common evolutionary ancestor within the phylum:- left mesocoel gives rise to most or all of the water vascular system, and one or both somatocoels form the lining of the body cavity.

Laura Hein

Body Symmetry

• Radial (pentameral)

http://webs.lander.edu/rsfox/rsfoximages3/lab1_x550_x_595x.gif Jaeyoung Kim

Nervous System

• Decentralized nervous system

– Radial nerves run under the ambulacra (legs)

– Central nerve ring surrounds the gut

– Eyespots that can detect light

– No specialized sensory organs

– and no definitive brain

http://www.brocku.ca/MeadProject/Angell/Angell_1906/images/ang01_06.gifJaeyoung Kim

Circulatory Structures

-A Echinoderm has water pumped through its body as part of its very simple circulation system

-no specific structures for the circulatory system

http://tolweb.org/Echinodermata

Laura Hein

Digestive/Excretory System

• Tubes grab onto food -> invert their stomach -> secrete/squirt juices (enzymes) that digest -> reabsorb digested food through mouth under the center -> wastes out the aboral anus

http://image.tutorvista.com/content/animal-kingdom/starfish-anatomy.jpeg

Jaeyoung Kim

Locomotion

• Vascular system consist of a network of hydraulic canals branching into extensions called papullae (tube feet), which provides: – slow movement

– feeding

– and gas exchange

Tube feet uses hydraulics to create negative pressure which acts as a suction force.

Jaeyoung Kim

Skeletal type

-Biomineral matrix composed of calcium carbonate and several proteins-calcite is composed of numerous tiny crystals lie on same crystal axis within an ossicle-because of this, ossicles are sponge-like microstructures called stereom that is unique to that phylum-Embryologically, echinoderm ossicles are a true endoskeleton, since they are produced by mesenchymal cells and are usually covered by epidermis-However, they act more like an exoskeleton, lying just under the epidermis and enclosing most other tissues in a flexible but tough covering.

http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_ossicle_diagr.jpg

Laura Hein

Sensory Structures/Features

-rudimentary senses including:

-light sensitive eyespots

-sensory tentacles (modified tube feet) at the tips of the arms

-small patches of cells sensitive to chemicals or touch.

Starfish Tube Feet

http://www.sfdj.com/learn/13.jpg

Laura Hein

Reproductive System

• Most are dioecious, with separate male and female individuals, but some are hermaphrodites.

• Each arm contains two gonads, which release gametes through openings called gonoducts, located on the central body between the arms.

http://egate.mcgehee.k12.la.us/faculty/jenniferz/biology/starfish%20B/STARFISH%20project/rep.%20diagram%20pic.gif

Jaeyoung Kim

Unique Features

http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_diagr_water_vasc.jpg

• Can regenerate lost limbs

Jaeyoung Kim

1.Which of the following is not a sensory structure of the echinodermata

A) Light sensitive eyespots b) Sensory tentacles (modified tube feet) at the tips of the armsc) Small patches of cells sensitive to chemicals or touch.d) Taste Buds

2. Which of these do not belong to the echinodermata phyla?

a) Starfish

b) Brittle Stars

c) Jelly Fish

d) Sea Cucumbers

3. What kind of circulatory system does the echinodermata possess?

a) No specific structures for the circulatory system

b) A system of capillaries running throughout the body

c) A heart with arteries, blood vessels, veins, and capillaries

d) A simple heart-like organ with no separate ventricles

4. Free Response: What are the steps to the digestive/excretory system of an echinodermata?

Quiz

Answers

• 1. A

• 2. C

• 3. A

• 4. See slide 8.