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| Dallas Zoological Society Partnership : Animal Classes Mollusks, Worms, Arthropods, Echinoderms |
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Topic Overview
Quick Facts
Mollusk
evolution began more than 500 million years ago, during the Cambrian period.
A deep-sea clam found in the North
Atlantic takes up to 100 years to grow to a length of one
centimeter.
Oysters can change their sex from male to female
to male and so on, throughout their lives.
Cone shells, a gastropod, carry fast-acting
neurotoxic venom. There are several species of mollusk that are capable of
killing humans.
Because they are unable to move and feed by filtering
particles from the water, mussels and oysters can accumulate certain types of
chemicals. In several countries samples of mussels and oysters are regularly
collected to monitor ocean pollution.
Charles Darwin spent 39 years studying
earthworms more than 100 years ago.
The
Australian Gippsland Earthworm grows to 12 feet long and can weigh 1-1/2
pounds.
Some earthworms can live over 10 years.
Worms
can eat their own weight in a single day.
Because of their appetite for shell fish, sea
stars are perceived as a threat by commercial fisheries, particularly those
that harvest clams, mussels, and oysters. Sea stars are known to get into
these commercial shellfish beds and devour them entirely.
A seastar can asexually reproduce to become TWO
seastars; they can do this in two ways: autotomy or fission.
Begin the Lesson
Whole Class Introduction to the Lesson
You will need at least one computer with Internet connectivity
and a projection device, a classroom with more than one computer, or access to
a computer lab.
For this introduction and activity you will need approximately
10 minutes.
Introduce students to the mollusk and echinoderm phylum by
showing the video, “Abalone Escape Response When Presented with the Sea Star” http://www.racerocks.com/racerock/archives/vidabescape2a.htm
Sample Questions
Describe the physical features of the abalone.
Describe the physical features of the sun star.
How does the abalone know that the sun star is
present?
Why does the sun star have an advantage over the
abalone?
What did the abalone do to defend itself?
As part of the introduction, you may want to review some of the
glossary terms in advance of students going online. At this point you can launch
the WebLesson as whole-class activity using a projection device, or you can
assign students to work individually or in teams in a computer lab.
WebLesson Sites
Introduction The world of Animals ranges from very basic, single-celled organisms such as protests and amoebae to the complex mammal, the human being. Within that range, you will find a massive array of fascinating creatures. With every body type, behavior pattern, and living style imaginable, there is a plethora of animals just waiting for discovery.
While biologists continue to hunt for new species, we can study those exceptional creatures that we have already discovered. Mollusks, which are soft-bodied gelatinous animals of the sea and land, are one such group. They come in every shape and color and many even include a shell. Cephalopods are remarkable creatures of the sea that use a variety of unique methods to move, eat, and protect themselves. They are relatively smart animals and have proven to be quite resourceful in many situations. The spiny sea creatures with appendages that extend from their center are the echinoderms. While they cannot move quickly, they have developed strong water vascular and muscular systems that aid in ingestion and defense. These, like the cephalopods and mollusks, are fascinating organisms that you will enjoy learning more about. Scenario You will join an underwater discovery team to explore and better understand the invertebrates of the sea. You will don your scuba gear and underwater camera to record your undersea observations. You will need to be very observant in this role, so be prepared to encounter strange and exciting animals.
Lesson Pages
The Cephalopod Page
http://video.google.com/videoplay?docid=4007016107763801953&q=octopus
In Search of the Giant Squid: The Inside Story
http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/squid_inside_story.html
The World of Worms
http://yucky.discovery.com/flash/worm/pg000101.html
Maggots and Leeches: Good Medicine
http://www.usatoday.com/news/health/2004-07-07-leeches-maggots_x.htm
Echinoderms – The Spiny Animals!
http://www.oceanicresearch.org/education/wonders/echinoderm.html
The Escape Response
http://www.racerocks.com/racerock/archives/archives_16a2.htm Conclusion & Project
Conclusion Mollusks, Cephalopods, and Echinoderms are truly remarkable living organisms. Within each phylum are thousands of intricately designed animals that never fail to astound scientists. Using physical and chemical assets, these animals have learned to live with and protect themselves from one another. Through shells, spines, ink, slime and enzyme secretions, enhanced brain systems, segmented bodies, regenerative abilities, and other such amazing characters, they have truly set themselves apart from the other members of the Animal Kingdom.
Glossary
univalve - one-shelled animals
bivalve - two-shelled animals
conchology - the study and collection of shells
cephalopod - “head-foot”; fast-moving carnivorous mollusks that use tentacles to aid in capturing food; propel themselves through the water by flushing water through their tube-like organ called the hyponome
aplacophorans - worm-like mollusks
chiton - primitive, elongated, bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates
gastropod - “stomach-foot”; slow-moving mollusks that have a muscular foot to aid in locomotion
cuttlebone - internal shell found in some cuttlefish
pen - smaller internal shell found in some squid
radula - file-like appendage that extends from the squid’s beak that rams food down into the esophagus
mantle - muscular swimming organ that relaxes and contracts to use jet propulsion to move the animal forward
gladius - feather-shaped blade made of chitin that helps to support the body of a squid
paralarva - first free-living, cephalopod life-history stage that is found in the near-surface plankton and that differs in both morphology and vertical distribution from older juveniles
spermatophores - a packet of sperm that is formed by the male and passed to the female during mating
hermaphrodite - an organism that possesses both male and female sex organs during its life
regenerate - to replace (a lost or damaged organ or part) by formation of new tissue
pognophore - wormlike marine invertebrates that grow in upright chitin tubes, usually at depths greater than 100 meters (330 feet), have tentacles attached to the head region, and lack a digestive system
skin graft - a surgical graft of healthy skin from one part of the body to another or from one individual to another in order to replace damaged or lost skin
anticoagulant - any substance that prevents the clotting of blood
dorsal - of, toward, on, in, or near the back or upper surface of an organ, part, or organism
ventral - relating to or situated on or close to the anterior aspect of the human body or the lower surface of the body of an animal; abdominal
setae - a stiff hair, bristle, or bristle-like process or part on an organism
clitellum - a swollen, glandular, saddle-like region in the epidermis of certain annelid worms, such as the earthworm, that secretes a viscous fluid to form a cocoon for their eggs
gizzard - a modified muscular pouch behind the stomach having a thick lining and often containing ingested grit that aids in the breakdown of seeds before digestion
crop - organ at the bottom of the esophagus where food is stored for later digestion
water vascular system - a system of water filled canals and appendages that function primarily in locomotion, reproducing and feeding
podio - tube feet; used for suction, eating and movement
benthic - the collection of organisms living on or in sea or lake bottoms
stelleroid - stemless echinoderms that have a central disc from which five or more arms radiate
aboral - the side of a radially symmetrical animal that does not contain the mouth
madreporite - small red or yellow button-like structure that often looks like a small wart on a sea star\'s central disk; used to filter water into the sea star\'s water-vascular system
echinoids - sea urchins and sand dollars
holothuroids - sea cucumbers
evisceration - to remove the entrails of; disembowel
sessile - organisms which are not able to move about; they are usually permanently attached to a solid substrate of some kind, such as a rock
ambulacral groove - grooves located on the underside of each appendage on the sea star that contain tube feet and are a part of the water vascular system
coelum - cavity within an animal body
cilia - a microscopic hair like process extending from the surface of a cell or unicellular organism; capable of rhythmical motion, it acts in unison with other such structures to bring about the movement of the cell or of the surrounding medium
macroalgae - a biological term used to describe larger forms of algae, such as seaweeds; topshell snails and other gastropods commonly feed on this
Trochus - any one of numerous species of marine univalve shells belonging to Trochus and many allied genera of the family Trochidae; topshells are the most common member
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