Chapter 38 Echinoderms and invertebrate chordates 1 Echinoderms and Invertebrate Chordates Chapter 38 P760-771

Chapter 38 Echinoderms and invertebrate chordates

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Echinoderms and Invertebrate Chordates

Chapter 38 P760-771

http://www.virted.org/Animals/Starfish.htmlhttp://www.starfish.ch/reef/echinoderms.html

http://research.calacademy.org/research/izg/echinoderm/echilink.htmhttp://www.youtube.com/watch?v=wjcjnXwSBJM


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Objective 38.1

• Discuss four distinguishing characteristics of echinoderms.

• Describe representative species from each of the five classes of echinoderms

• Describe the water-vascular system and other major body systems of echinoderms

• Compare sexual and asexual reproduction in sea stars


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P. Echinodermata – spiny skin

• Is a group of invertebrates that includes sea stars, sand dollars, sea urchins, and sea cucumbers. The members of this phylum, call echinoderms, inhabit marine environments ranging from shallow coastal waters to ocean trenches more than 10,000 m deep. They vary in diameter from 1cm to 1m and are brilliantly colored


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Characteristics

• Radially symmetrical • Have no head or cephalization• Larvae (bilaterally symmetrical)• Fossil records- Cambrian period (500 million

years ago• Early were sessile as evolved motile (crawling),

80speices still sessile• Deuterostomes• Coelomates


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Characteristics4 major not shared by any other phylm

1. Pentaradial symmetry (center with spokes)

2. Endoskeleton composed of calcium carbonate plates known as ossicles

3. Water-vascular system- canals

4. Tube feet- aide in motion, feeding, respiration and excretion


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Classification

7000 species into 6 classes

1. Crinoidea

2. Ophiuroidea

3. Echinoidea

4. Holothuroidea

5. Asteroidea

6. (we wont talk about)


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C. Crinoidea – lily-like

• Crinoids• Sea lilies, feather stars• Sessile as adults (sea lilies)• Swim crawl as adults (feather stars)• 5 arm extension, branch to form many arms- up

to 200 in some• Mucus covered tube feet (gas exchange and

feeding)• Mouth faces up (most other it is down)


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C. Ophiuroidea- snake tail

• 2000 species of basket stars and brittle stars

• Largest class

• Long narrow arms, ability to move quickly

• Arms can break easy- regenerate

• Bottom of ocean


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C. Echinoidea- spine like• 900 species• Sea urchins and sand dollars• Internal organs are enclosed w/in a fused, rigid

endoskeleton called a testSea urchins• Move by tube feet• Eat algae off surfaces • Aristotle's lantern- teeth and mouth, complex jaw• Some spines contain poisonsand dollars- Live along coast lines, found in sandy areas- Flat round shape - Shallow burrowing


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c. Holothuroidea- water polyp

• Sea cucumbers

• Armless echinoderms

• Live on bottom of sea

• crawl or burrow with tube feet

• Ossicles make up endoskeleton

• Soft bodies


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C. Asteroidea- star like

• Sea star, starfish

• Live in coastal waters

• Variety of colors and shapes

• economically important because they feed on oysters, clams (human food)


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C. Asteroidea-External structure-

• composed of several arms (5- 24)• Two rows of tube feet under each arm• Body is flattened• Oral surface- mouth side, under side• Aboral surface – opposite to mouth side• Covered with short spines• Tiny pincers called pedicellariae, keep it

free from of foreign objects


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C. Asteroidea-Water-Vascular System-

• Net work of water-filled canals that are connected to the tube feet

• Water enters through pores in the madreporite (sieve-like plate on aboral surface)

• Water passes down the stone canal- tube that connects the madreporite to the ring canal (encircles the mouth)

• Radial canal carries water to the tube feet (valves keep it from flowing back up)

• Ampulla- sacs on feet contract forcing water into the feet


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C. Asteroidea-Feeding and digestion

a. mouth short esophagus cardiac stomach ( can turn inside out through its mouth when it feeds) pyloric stomach (connects to a pair of digestive glands in each arm) nutrients are absorbed into the coelom by walls of digestive cavity and excess is excreted by anus on aboral surface

b. they are carnivores, mollusks, worms


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C. Asteroidea-Other body systems

a. no circulatory, excretory or respiratory organs

b. gas exchange and waste excretion by diffusion in walls of tube feet and skin gills

c. no head and no brain

d. have a nerve ring and radial nerves

e. nerve net and touch-sensitive cells


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C. Asteroidea-Reproduction and development

a. separate sexes

b. each arm has a pair of ovaries or testes

c. 200 million eggs in one year

d. external fertilization-

e. fee-swimming larva bipinnaria

f. 2 months metamorphosis

g. regenerate arms, long time


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Chapter 38 Echinoderms and invertebrate chordates 1 Echinoderms and Invertebrate Chordates Chapter 38 P760-771