Download Echinoderms and Invertebrate Chordates

Echinoderms and
Invertebrate Chordates
Chapter 38 P760-771
http://www.virted.org/Animals/Starfish.html
http://www.starfish.ch/reef/echinoderms.html
http://research.calacademy.org/research/izg/echinoderm/echilink.htm
http://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
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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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Characteristics
4 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
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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 test
Sea urchins
• Move by tube feet
• Eat algae off surfaces
• Aristotle's lantern- teeth and mouth, complex jaw
• Some spines contain poison
sand dollars
- Live along coast lines, found in sandy areas
- Flat round shape
- Shallow burrowing
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c. Holothuroidea- water polyp
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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
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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. AsteroideaExternal structure•
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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. AsteroideaWater-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. AsteroideaFeeding 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. AsteroideaOther 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. AsteroideaReproduction and development
a. separate sexes
b. each arm has a pair of ovaries or testes
c. 200 million eggs in one year
d. external fertilizatione. fee-swimming larva bipinnaria
f. 2 months metamorphosis
g. regenerate arms, long time
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