Molluscs: General Lesson Plan
Bourquin and Robynn Honeychurch
things first! Printout and use the lesson
plan checklist to assist you in making the most out of your lesson plan
Length of Lesson:
Approximately 3 hours for the general lesson plan.
This however, can be any length depending on the plan you choose to use or make
up from the materials presented here. Their is more than enough information
and additional resources presented here, that it can quite easily be split into
many different lesson plans formats.
*Please note that this is
an extensive lesson plan containing a lot of information and ideas. You, as
the teacher should take the time to read through the following pages and determine
which format and which activities will work best for you and your students.
TEACHERS:By no means try to present
all the information in one lesson plan. Scan this lesson plan, then decide which
lesson plan format and materials you wish to use for your class.
Plans presented in this package
|| K through 12
|| 3 hours plus
|| 1-2 hours
||2 hours plus
lesson plans that can be created from the information found in this general
- Snails, Bivalves
and Octopus: decide which grade level and materials are most appropriate
for you. A lot of information and activities have been placed here so
that you may easily personalize a lesson plan best suited for you and
your class and time available for this subject.
- Gastropods (Marine
Gastropods lesson plan information is coded brown)
(Bivalve lesson plan information is Coded Green)
(Cephalopod information is coded Navy Blue)
To provide students with an introduction to the invertebrate phylum, mollusca
and to help them gain a basic understanding of molluscs in general.
In most of these lesson plans, three main classes will be discussed in general.
Those classes are; the gastropods, bivalves and cephalopods. The main emphasis
in the K to 8 lesson plans will be on the terrestrial (land snail) gastropods
mainly. The 8 - 12 lesson plan will also include a discussion on the other classes.
Those of the Polyplacophora, Scaphopoda, Monoplacophora and Aplacophora.
Discussions and materials
presented will cover such things as anatomy of the mollusc, needs of the mollusc
and procreation of the molluscs. Your students will also learn how and why molluscs
are important to humans and the environment. They will also be presented with
the habitat and environmental problems involved around and with molllusc.
Students will create a report, including drawings and notes based on the information
presented to them and the observations they make of their molluscs, shells,
habitats and work sheets presented in this lesson plan.
Students should be encouraged
to participate in discussions about molluscs, their value to humans and the
environment and a bit on "Molluscs: Friend or foes?".
Students should also help
out in making a molluscan habitat and other classroom projects (e.g. posters)
based on molluscs.
Molluscs are an integral part of our environment. In studying this life form,
students will observe the way these animals are a very important member of our
world today. The mollusc's reliance upon the environment in which they live,
and the way in which we humans rely on them, exemplifies the interconnectedness
of all the ecosystems of the earth.
- Students will be presented
information, visual, and written plus worksheet projects on the main classes
of molluscs: gastropods (ex.: snails), bivalves (ex.: oysters and clams),
and cephalopods (ex.: octopuses). Senior levels will also include the the
other four classes of molluscs.
- discuss what molluscs
require to live and stay healthy
- hear (younger students)
or read the educational story about snails "Sammy's Adventure"
- observe molluscs
in a simulated natural environment (terrarium, aquarium, etc.)
- discuss how humans
now use and have used molluscs in the past
- discuss the importance
of a healthy environment to molluscs and thus to humans,
- study, label and
draw collected shells and help to create a classroom display
- colour pictures and
complete worksheets which are passed out and which are available on the
- draw a mollusc/s
they have seen and record facts they've learned about molluscs. This can
be in report form.
- continue with other
suggested projects to further explore the subject of molluscs.
The following steps should be taken well in advance of teaching this lesson:
Print out a copy of
this lesson plan for yourself to follow. Decide what printed materials will
be used for your lesson and have the appropriate pages photocopied. (See
the enclosed in the the lesson plan
Research your locality
for available resources such as, museums with shell collections, local aquariums,
local shell clubs and or shell collectors in your vicinity. Often you can
find someone willing to come into your classroom to present and display
their shell collection. Field trips may also be planned as part of your
- Teachers should also
collect some shells to share with their students. Do this a few weeks before
you first lesson. Check your local museums, ask friends, look for shell clubs
in your area. Many people collect shells and may have some to lend you.
- To find local shell
clubs: go to: Man and Mollusc International Shell clubs at: /links_mala.html
- For museums and aquariums,
go to: /links_museum.html
- Often there are shells
to be found on lake shores, by creeks and rivers and always near the seashore,
should you have access. Live clams, oysters, mussels and many other shells
can be collected. To preserve in an intact mollusc, place the entire specimen
in rubbing alcohol or you may take out the inside mollusc and just preserve
it in rubbing alcohol or formaldehyde to show your students. Shells can
be cleaned as well and shared with the class. Be aware of collecting bans
or bag limits for your area as many molluscs are on the endangered or
protected species list. (Smelly shells are easily cleaned in a few hour
or overnight by placing them in a strong bleach solution. However, if
a shell has a skin covering it (Called a periostracum) just clean the
inside of the shell with a soft tooth brush and mild soapy dish detergent
then place the shell in rubbing alcohol for a few hours then coat the
skin with baby oil or mineral oil. This will help to preserve the shell's
- Several weeks before
your first Mollusc lesson, encourage your students to look for shells of all
kinds. Perhaps their relatives or friends will have shells which they are
willing to lend out. Place each student's contribution in their own labeled
bag, so that shells can be returned to the rightful owner after the completion
of the lesson.
If you live by the seashore,
lakes, rivers or other bountiful snail and slug areas,encourage students
to bring in their own shells to class. Make sure these shells are clean
and not inhabited or filled with decaying matter (soaking shells in a bleach
and water solution used under strict adult supervision, cleans up most shells).
Unshelled molluscs such as slugs should be placed in an air tight jar filled
with rubbing alcohol. These shells should also be placed in bags and labeled
with the students name. You should also encourage the student to place a
paper with their find as to where the shell was found the date it was found
and if it was alive or dead when collected. Have them write down as many
details as they can in regards to their finds. If they become a shell collector,
collection data slips help to increase the educational and economical value
of their collection.
*** Be sure to heed
this, and share this with students: if shells are brought from far away,
make sure there is nothing living in them! Clean out the shells before they
leave their place of origin. The propagation of misplaced molluscs can cause
serious environmental and ecological damage!
If in your lesson plan you are
going to include living snails in a terrarium or aquarium; be
sure you have the appropriate food, water and
other necessities such as a calcium source available for feeding the snails
that you will collect and house.. Have your snail's terrarium or aquarium
created BEFORE you collect or purchase your snails. (See the habitat preparations
in the next section).
If you plan to use garden
snails for your students to observe, plan to collect them well before you
want to use them in the classroom. Sudden changes in the weather can send
an apparently plentiful supply into hiding so that none will be available.
This is also good advise if using live freshwater snails.
Often live terrarium or aquarium snails can be purchased at pet stores.
See details of collecting and looking after snails. (See the habitat preparations
in the next section).
If teaching younger
children, be sure to print out "Sammy's Adventure" story, and
any additional worksheets , colouring sheets, etc. that you plan to use
(see the lesson plan checklist).
All materials found on this lesson plan are the property of Man and
Mollusc and are not copyrighted for educational use and can be freely used
for all educational needs. The exception is "Sammy's Adventure".
This story is copyrighted but may be used freely for all classroom lessons.
An illustrated "Sammy's Adventure" story book will be published
within the next year (2002). To learn where and when this book will be available,
check with the owner, Avril Bourquin: email@example.com
A few weeks before you teach this lesson, check through some of the sites
listed on the Additional Resources section at the end of this lesson plan.
There are extra more games, puzzles, pictures and much more information
about molluscs that you may wish to use.
- A few days before your
first class, search out books at your school or community library on molluscs
to bring into your classroom and share with your students. Bring as many of
your School Library books on molluscs to your class as possible. This way
students will know what to look for in their own school library.
Optional Ideas that take some preplanning
Escargot (canned) can
usually be bought ahead of time at most grocery stores and can be brought
in to class to show students an example of edible terrestrial snails. For
class use; open a container of escargot, wash and place them in a clean
container filled with rubbing alcohol. Replace alcohol, as needed, when
it begins to go brown.
Oysters, clams, scallops
and mussels can usually be bought ahead of time at most grocery stores or
fish markets to be preserved for class as well in alcohol or formaldehyde.
Living marine molluscs
can also be purchased or found nearby if you live at the ocean and these
may be kept in a saltwater aquarium and kept alive for the classroom (see
habitat info in next section) . Use local beach water for these specimens
unless you are used to maintaining a salt water aquarium. This water must
be replaced regularity and an aeration stone is a must. I would only encourage
you to keep such living specimens for one day only unless you are proficient
at salt water aquarium keeping. Plan to return these to their original home.
If you are a really
ambitious and creative teacher you may even decide to cook up a seafood
meal for your students as an introduction to this mollusc unit. Parents
may be of help in preparing a seafood or molluscan feast . Notes sent home
with a student well in advance of this lesson may help you to present the
idea and help you locate volunteers.
A field trip could be
planned to search out molluscs and to observe them in their natural habitat.
Seashore rock pool or tide pools, lake shores creeks, and rivers make an
excellent field trips.
A word of advise: visit these areas well in advance of taking your students
so that you know for sure where to locate snails. If going to a beach, be
sure to know what the tide status will before this day as well. Tide and
rock pools may totally disappear if you have a high tide. Also be sure to
have adequate supervision for all students if undergoing such a field trip.
Once again, check whether or not you have a local shell club which might
be of help to you on such a trip and if their are collecting bans or bag
Museums or aquariums
with a focus on sea life or molluscs can also make a good field trip destination
for this unit. Often if you speak to the curators of such facilities, special
arrangements can be made to have a special displays and onsite talks for
your class. Give these people as much time as you can for arranging such
Materials and Aids
- Make sure to have a
copy of the lesson plan checklist
- Copy of the general
lesson plan and if using one of the other plans, copy that out as well
- Rubbing alcohol and or
formaldehyde and jars with tight fitting lids for preserving any living tissues
to be used for the classroom
- You may want to bring
a jug of strong bleach water to class to clean any shells requiring extra
- Bags (Zip locks work
great!) and a labeling pen for storing the students' shell contributions
- Collected shells (found
by students or teacher or both). Make sure they are well contained and labeled
as well so they can be returned to the rightful owner on completion of this
- For younger children: "Sammy's
Adventure" story (see the the
lesson plan checklist)
- Colouring pictures (see
lesson plan checklist)
- Printed handouts on
molluscs for students (see
lesson plan checklist)
- Miscellaneous sheets
of coloured paper
- Blank paper, pencils
and erasers for drawing snails and recording facts
- Crayons and or pencil
crayons for colouring pictures and drawing snails and shells
- Scissors for children's
- Glue or glue sticks
- Large Bristol board for
making a class poster
- A piece of glass or Plexiglas
about 6 by 12 inches with well taped edges for safety.
- Terrarium, aquarium
or other habitat containers
- Snails, plus their correct
food and water source. Keeping a living exhibit is discussed in the next section
of this plan
- Library books
Making a terrarium habitat:
This can be kept as simple as a jar or as complex and imaginative as you and
your students wish. These are just guidelines.
Active snails can be kept
for classroom viewing in a terrarium made from an aquarium, a large, wide-mouth
jar turned on its side, plastic tubs, fish bowls,etc. The top should be securely
covered with a fine meshed nylon screen or part of a nylon stocking. Lids which
have holes punched in them do not allow for adequate ventilation and the sharp
edges on the interior are a safety risk to both snails and students.
To collect terrestrial snails,
you will need a shovel and a container (to put your snails in). Make sure your
container is not airtight so that the snails can breathe by making tiny holes
in the lid. Use a plastic container to avoid sharp edges. (You need a lid to
cover your container because snails can crawl on any texture or surface.)
To find the snails; choose
a damp spot such as, under leaf litter or near a pond. Use your shovel to loosen
the ground and you should find many snails just beneath the surface. Be sure
to collect some of the soil or leaf litter for use in your terrarium.
Terrestrial snails may be
collected around gardens and in trees in your own area. Be sure to locate these
snails well in advance so you know where to find them for your classroom. Looking
for them at night time is best as most are nocturnal and or like to like in
dark damp places so that they don't dry out so fast. Be sure to know what they
eat and collect as much food from their natural environment as possible to include
in your terrarium. Non-clohorinated or natural (Rain, lake or stream) water
is also a must, so collect enough for the entire time you plan to keep your
snails. Herbivores also will generally enjoy lettuce broccoli, fruits etc.
Keep the terrarium clean
and food and water supplies fresh and clean. Plan to release these snails back
to their original home upon completion of the lesson. If they are a known pest,
you might well have them properly destroyed and keep the shell for future class
In your terrarium, drinking
water can be supplied in a shallow dish, plastic lid or in a deeper dish containing
a water soaked sponge, or by generously sprinkling lettuce or other fresh, leafy
food with water. Create a sample habitat by including damp soil, or sand, plants,
and rocks preferably from the snail's original habitat.
Food can also be placed into a shallow plastic lid in the terrarium. Most terrestrial
snails are vegetarians and eat many kinds of plant material. Cornmeal, oatmeal,
and fresh green leaves (Lettuce, broccoli, fruit, etc.) are all appropriate
foods. Chalk, a cuttlefish bone from pet store (NOTE: this is a mollusc) or
eggshells should be placed into the terrarium to provide the calcium necessary
for healthy shells. Snails need calcium for healthy strong bones, much as we
need calcium for strong, healthy bones.
Cleaning to remove stale or moldy food, the build up of mucus, and droppings,
should be done on a regular basis. Water should also be kept clean and fresh.
Encourage your students to help with this chore.
Snails which withdraw into
their shells during class can usually be coaxed out by a brief dip in a shallow
container of water.
Overcrowding snails should be avoided. In terrariums, too many snails in too
small a space, or inadequate ventilation can cause the humidity to rise to unacceptable
levels and the snails will die.
If time permits, (are you
keeping the snail for a few weeks or more), the lifecycle of the snail can be
observed in the classroom. Adult snails can be recognized by a small lip that
is added to the open end of their shell when growth is complete.
Most terrestrial snails
are hermaphroditic (each snail had both male and female sex organs), any two
snails can mate. Each fertilizes the eggs of the other. The eggs are usually
laid in a hole that the snail digs in the damp soil or under bark or damp leaf
litter The small, translucent white eggs about the size of small peas.
Upon completion of your
lesson, plan to return all snails to their original home. If they happen to
be a known pest species, they may be disposed of appropriately and their shells
cleaned and kept for future lessons. Soft parts may also be kept in formaldehyde
or rubbing alcohol.
Make a Freshwater Aquarium
Habitat: This can again be kept very simple or as complex
and fancy as you wish to be.
For freshwater snails, search
along the lake shores river or creeks. Be sure to look under wharfs, stones
and on water plants. Use a fine meshed collecting net to retrieve snails. Be
sure to collect a good supply of the water the snail is found in. This is the
best way to make sure the snail remains healthy. Use only this water (you may
add an aeration stone, and filter system to keep the snails healthy and happy.
Rocks covered with mosses and algae found around the snail should also be added
to the aquarium. This aquarium should also have a lid or stocking cover as pond
snails sometime do crawl out of the water.
Aquariums, large glass jars,
fish bowls or any solid water proof container can be used. Just make sure it
has a fine meshed top or stocking top for a lid. Molluscs are great escape artists.
You may have a fully water-filled
aquarium or just a pool of water around such things as rocks and old tree branches
from the area where you found the snail. This allows the snail to crawl on and
up out of the water. An aquarium lid or mesh top to prevent escapes is still
a vital part of this setup.
Be sure to return all living
snails to their place of origin or have them properly disposed of, if they by
chance are a known pest species, at the completion of your lesson.
Unless you are just keeping
a salt water habitat for a few hours, it is best to have a well established
saltwater aquarium or at minimum a lot of replacement water from where you caught
Sometimes salt water molluscs
can be found at a pet stores or if you live by the ocean, they may also be collected
on the seashore around rocks in the inter-tidal zone.
Be sure to collect a good
supply of the water where they live for your aquarium. These molluscs should
be returned back to the ocean ASAP as they will not survive long in a simple
aquarium. You should also collect a few rocks, sea weed and a bit of bottom
sand or detritus to add to your habitat.
If you are going to use
an established salt water aquarium, I would strongly suggest that you understand
the basics of maintaining such an aquarium. Another option would be to have
a knowledge person placed in charge of your aquarium for you. Check at your
local pet shops for such help.
molluscs, be sure to know and observe local collecting bag limits and restrictions.
Usually this can be found out a government offices. Permits to collect may also
Salt Water Tide Pools:
If you live near the ocean,
you may wish to set up a classroom tide pool. Collect molluscs, rocks, algae,
sand, water weeds or whatever else you find in the natural tide pool . Be sure
to check with the authorities on legalities of live collecting and disturbing
a habitat. If you explain that it is a school project, and that everything will
be returned to it's original place after the lesson, there is generally no problem.
Something like a large plastic
Rubbermaid container or baby bath makes for an excellent tide pool.
Make sure you collect lots
of water to keep it fresh and well aerated. You may also use an aeration stone
however, the water still becomes fouled very quickly. Artificial tide pools
should only be kept about 24 to 48 hours unless you are familiar with caring
for such a habitat and know what molluscs you have and what their needs are.
Again, make sure you have
a good mesh cover as these molluscs also love to wonder about especially if
you happen to have picked up a shell inhabited by a hermit crab..
Teachers should encourage
students to share what knowledge they already have about molluscs ahead
of actually starting the lesson.
Have students bring in shells and bag and label them as discussed above.
This may be done any time before the beginning of the actual lesson plan.
Teachers may have the students
help to set up a live habitat or do something like a diorama ahead of the
actual lesson as well.
Teachers should read "Sammy's
Adventure" to younger students (also enclosed in the the
lesson plan checklist), first instructing students to listen for the
facts about snails that are hidden throughout the story.
Teachers should ask
students what they have learned about a snail from this story or about other
molluscs from materials you present
Students will be asked
to carefully observe the molluscs in their habitat (the terrarium or aquarium
or other habitat that the teacher and they have set up). Send students up
in small groups to study the habitat, while the other students remain in
their seats and record, in note form on the same sheet where they will draw
their snails, the facts they've learned about snails from the story they
If there's time and
you're using terrestrial or pond snails, teacher can remove several snails
from the habitat, and place them on moist surface such as a big leaf from
a head of lettuce to also observe then move about and eat.
to gently touch and pick up the snails so that they can closely observe
their colours, shell pattern, body shape, size and texture.
Have the students carefully
place the mollusc onto the piece of prepared glass so they can observe the
snail moving. A small bit of cornmeal or cornstarch can also be placed on
the glass and you might actually see the mollusc feed by using it's radula.
Small scratch marks will be left visible if they do feed. Remind students
that they will be returning to their seats to do a detailed drawing of the
snails they've observed. Have students also observe the contents of the
habitat as well , so that they can draw these in as well.
Upon returning to their
seats, students should draw the molluscs in its habitat from memory, and
write any additional facts or observations that they have made from observing
the snails. Encourage students to draw in as many details as they can: including
the foot, tentacles, eyes, body and shell of the mollusc, plus whatever
else is in their habitat to keep the snail alive and happy.
Handout the snail diagrams,
other work sheets stories or quizzes that you plan to use for students to
study and label.
Be sure to cover such facts with
your students such as:
Teachers should encourage
students to brainstorm:
(If desired and have them prepared, hand out the pages on Introduction to
Molluscs, Cephalopoda, Bivalves, and Gastropoda. These pages are from Man
and Molluscs Beginner's (and are also enclosed in the the
lesson plan checklist)
Discuss what other
sea creatures and land beasties can your students think of that might be
molluscs? (be sure not to get mixed up with such things as starfish, sea
biscuits and sand dollars etc., which are echinoderms) (Ex: slugs, nudibranchs,
sea butterflies, nudibranchs, etc.)
What do your students
think molluscs eat? ( you may want to talk about herbivores, carnivores.
Omnivores and parasites if the age group lends to this. Filter feeding bivalves
to the hunting carnivores such as fish-eating cone shells may be touched
upon here as well.)
What do molluscs need
to live? (food, moisture, and a clean oxygen supply)
Can students think
of ways in which humans use molluscs? And their shells?
What do your students
think happens when the environment (ocean) where molluscs live becomes polluted:
like with an oil spill or when sewage from homes or industrial pollutants
and garbage gets dumped into the earth's water systems?
Ballast water from ocean liners is also another danger to ports. This is
how such things as the zebra mussel got into the Great Lakes where they
have created massive damage.
Snails moved from one habitat to another may become bad pests and devastate
crops and other vegetation.
Discuss with your students
what happens when the environment is disrupted due to lack of molluscs that
were once present or when new introduced species overruns an area.
Age level and time permitting,
you may even want to touch upon some ways in which the medical world is presently
studying molluscs. Such things as pain killers, cancer cures, skin adhesives
for operations and materials for healing broken bones are just a few medical
objectives being developed from molluscs.
Animals and man that feed upon this mollusc are losing a food supply. Where
invasive molluscs go, food supplies that other rely on are jeprodised and
or crops may also be destroyed. How does all this affect man?
What happens to terrestrial snails when their habitats are destroyed? Tree
snails in areas of deforestation, or freshwater molluscs when their marshlands
are drained, or chaparral areas that are torched, or beaches that are restored
by dredging sand where molluscs normally live(both where the sand is collected
and where the sand is dumped).
There are many great environmental ramifications that can be studied about
and discussed with your class in this area.
Ancient and traditional
medicine use many molluscs for their curative powers.
Medically, molluscs are also responsible for spreading many illnesses such
as schistosomiasis. More information on Molluscs and Medicine can be found
on the Man and Mollusc site at: /links_medicine.html
NOTE: Students can
write down additional facts on the report they are creating about snails, as
the discussion progresses. Teacher should prompt for this by writing key words
and ideas on the board.
Mollusc Information That Should Be Covered:
This is a more comprehensive
list of molluscan facts to cover is in the next section on" Snail Facts
to Refer to When Discussing and Marking Projects":
- Molluscs have been around
for over 500 million years.
- To live, all molluscs
must have: food, oxygen and moisture. Most molluscs live in the ocean or,
if on land, in moist places such as in lakes, rives, marshes or under leaves
or in soil. All molluscs require moisture to stay alive. Even the desert dwelling
snails are no exception and they maintain their own moisture inside their
shell by means of a trap doors and or a or creating a mucus cocoon and a mucus
- Many molluscs eat: plants
(herbivores) or plant cell material in the water. Terrestrial snails like
to eat fresh leaves and decomposing material. This can be beneficial because
they break down decomposable materials, but snails can also become pests when
they turn their attention to garden greens. Many water molluscs eats mosses,
algae and such other microscopic plants.
- Other molluscs are carnivores
(eating such things as fish and other molluscs) and some are even parasites
(living within another living host)
- Most aquatic molluscs
filter oxygen from the water to "breathe" by means of gills . Terrestrial
and some pond snails breathe using lungs (Pulmonary sacs) just as we do. Some
pond snails have both gills and modified lungs. Deep ocean trenches do have
molluscs that do not utilize oxygen.
- Polluted waters lack
oxygen and food for molluscs and other water creatures to eat and "breathe".
This makes them sick and they die and their babies don't hatch or don't live
long. When molluscs disappear, the fish and birds and mammals (like otters)
that eat them have less food and some of these animals begin to die. Then
there is less fish and molluscs for us to eat, too. If the water they live
in is really polluted, the molluscs and fish that survive won't be safe to
eat. All the parts of our environment are connected and so you can see how
important molluscs are, and how important a clean environment for them to
live in is.
- Most molluscs can be
eaten by humans. Some of our favorites are scallops, oysters, clams and escargot
(land snails - Helix aspersa L.) To give you an idea of the extent of this
food source, you may want to visit the Data Base of Edible Molluscs on the
Man and Mollusc web site. The URL for this is: molluscan_food_mp.html
- Today as in the years
past, many people love to collect shells for their beauty and interesting
shapes. People who study the shells are called Conchologists. Those scientists
that study the molluscan animal are called Malacologists
- Shells have long been
used by man as tools, meidicone, trade goods, buttons, jewelry (pearls and
cameos), etc. See the Man and Mollusc Article: Uses of Shell-Bearing Molluscs
- Past, Present & Future located at: man_and_molluscs_a.html
- Dyes from some molluscs
(mostly murex) can be produced from shells for use in colouring cloth. This
is not so important today as we have much cheaper synthetic dyes. The Royal
Purple garbs of monarchs and priests of old were made from molluscan dyes.
This is discussed further in The Man's Uses of Molluscs article (man_and_mollusc.html)in
the section: Personal Adornment (8); personal_adornment.html
Facts to Refer to When Discussing and Marking Projects:
detailed anatomy and physiology facts both for beginners ( A Beginner's Guide
to the Molluscs ) and seniors (The Phylum Mollusc) can be found on the Man
and Mollusc Lesson Plan-Checklist for Printouts
Molluscs (Mollusks; both
spellings are correct)
- Molluscs can be found
in gardens, in ponds, deserts and oceans. Some live in the tops of trees and
others high in the mountains-and there are probably some in your back yard!
- They belong to the group
(phylum) of invertebrate animals with a soft bodies known as molluscs Characteristically
they have soft, unsegmented bodies. Often, their soft bodies are protected
by a hard shell.
- A gastropod in Latin
means, gastro for stomach and pod for foot.
- A cephalopod in Latin
means head - foot
- Bivalves or Pelecypoda
in Latin are called hatchet - foot
or Garden Snail Facts :
Achitina fulica (Giant African Land Snail)
- Terrestrial gastropods
often have a shell to protect their soft body. Some like slugs have no shells.
- The body of the snail
is usually moist and often slimy.
- Snails have tentacles.
They have a very developed sense of smell, but do not feel much sensation/touch-wise.
They do not hear or taste food like we do and their behavior is instinctive.
- Eyes are usually on the
tip of the tentacles. The snail has two pairs of tentacles on its head. One
pair is longer than the other pair. The eyes are on the longer pair. The shorter
pair is used for smelling and feeling its way around. The tentacles are very
important to a snail.
- Many gastropods are
autonomous, meaning they can regrow lost body parts.
- When the snail is disturbed,
it simply withdraws or pulls its body back into its shell. The snail then
seals the entrance with a mucus plug or a trap door, called an operculum.
Many snails also use this trap door, to hold in valuable moisture during dry
spells. This door is located on the top of their foot and when danger is around
or they are required to maintain moisture, this operculum closes them into
- When land snails are
threatened and want to hide, they go beneath leaves, stones or logs and if
possible pull into their shells and hide.
- The majority of snails
are most active at night and on cloudy days. They do not like the sunshine
very much as it dries them out too fast.
- Snails do not like hot
and dry conditions. They like it moist or humid and not too bright.
- During very cold weather
or winter, they hibernate in the ground. During dry periods (droughts) molluscs
pull into their shells or create a mucus cocoon to keep in valuable moisture.
This kind of hibernation is called aestivation.
- Snails have different
shaped shells. It can be a single shell that is rounded or a pointed spiral
or flat. They are often brightly coloured and some even have spines and ridges
- A snail has fingernail
file like tongue called a radula in its mouth for scraping food particles
off. This radula is like a rough tongue-like ribbon, something like a file
with rows of tiny teeth, which it uses to scrape off bits of leaves and flowers
- Snails eat mostly living
plants as well as decaying plants. They also chew on fruits and young succulent
- The snail moves by creeping
or gliding along on a flat "foot" underneath it's body. The band
of muscles in the foot contracts and expands and this creates a kind of rippling
movement that pushes the snail forward. The "foot" has a special
gland that produces slimy mucus to make a slippery track. You can often see
these silvery tracks in the garden. The slime comes out from the front and
hardens when it comes into contact with air. The snail is able to move on
very sharp pointed needles, knife, razors and vines without being injured
because the mucus-like secretion helps to protect its body.
- The garden snail travels
about 70 cm every 3 minutes-that's 1 km every three and a half days.
- Many snails are both
male and female. Therefore, it can produce sperms and eggs at the same time!
However, to fertilize the eggs, the snails need to exchange sperms with each
other. An animal that is both a male and a female is called a hermaphrodite.
This method of reproduction comes in very handy as these snails are very slow
moving and dont like moving around too much. If they had to go looking
for a boyfriend or girlfriend, it could take them a very, very long time to
- The brown garden snail
(Escargot: Helicidae family) lays about 80 spherical shaped white or yellowish
coloured eggs at a time into the topsoil of the ground. It can lay eggs up
to six times a year. Snails take about 2 years to become adults.
- After mating, each snail
will go search for soft ground to dig and lay its eggs in.
- The snail lays its eggs
in a nest, 2.5 to 4 cm deep in the soil or under tree bark o4 ground leaf
litter. Each snail can lay an average of 85 eggs and they hatch in 2 to 4
weeks, depending on the temperature and moisture of the soil.
- The first thing that
a newly hatched snail does is to find food. It will eat whatever is left of
its eggshell too. As the snail grows, its shell grows too, in a spiral shape.
The new shell is added at the opening of the shell. The part of the shell
the baby snail was born with, ends up in the middle of the spiral.
- Snails have many natural
enemies. They include ground beetles, snakes, toads, turtles, and birds, including
chickens, ducks and geese.
- The largest known land
snail is the Giant African Land Snail. It can weight up to 2lb (900g) and
measure up to 15.5 inches (39.3cm) from snout to tail.
- Many land snails are
very strong: they can lift 10 times their own weight, even moving up the side
of something-like a tree.
- Snails can live up to
10 years depending on which species you look at. Some have been known to live
up to 15 years or longer.
- Many people get upset
and farmers get angry when snails eat their plants and crops. Snails can cause
serious damage to crops.
- Terrestrial snails are
the food humans eat as escargot. The flesh of the snail is very delicious.
The French people, especially, love to eat these snails.
- Some people keep snails
in aquariums together with their fish. However, they must make sure that they
control the number because snails reproduce rapidly !!
- Many types of terrestrial
snails such as the helicidae or escargot snails are actually farmed today.
This farming method is called Heliciculture.
Gastropods: Aquatic (Pond
or other Freshwater) SNAIL Facts:
Pomacea bridgesi (Golden apple snail)
- The pond snail is, in
many ways, like the garden snail.
- Pond snails are usually
tan or dark brown in colour, but some are very brightly coloured as is the
golden apple snail seen above.
- Some pond snails have
gills to breathe in water. Those with gills will live at the bottom of the
pond. Those that do not have gills will come up to the surface to breathe
and have pulmonary sacs which act like our lungs. These snails will live on
the surface so that they can come up to breathe easily.
- You can often buy pond
snails from a pet or aquarium stores. One common pond snail often sold is
called "Apple" snail or golden snail.
- The pond snail feeds
mainly on plants like algae and microscopic creatures that are found on the
surface of waterweeds. They eat by scraping bits off with their rough, sandpaper-like
tongue, just like the garden snails.
- When pond snails are
threatened and want to hide, they bury in the sand, or hide beneath rocks
or logs on the bottom of the pond. In the ocean, snails will hide in caves,
or on rock ledges.
- Most pond snails reproduce
just like the garden snail. It is a hermaphrodite. The only difference is
that, unlike the garden snail, the pond snail carries its fertilized eggs
with it or stick them onto or under foliage or stones. If carried around on
their mother's shell, the baby snails will only leave their mother when they
- Some pond snails can
swim and others can bury themselves in the sand very quickly.
Gastropods Facts (these are the conchs (Strombidae), whelks
(Buccinidae), limpets (Lotiidae), periwinkles (Littorinidae), cones (Conidae),
volutes (Volutidae), and cowries (Cypraeidae) that we mostly know)
Cypraea moneta (Money cowrie)
seashells that people recognize and pick up along our beaches fit into this
group of molluscs
have a coiled shell. Their soft bodies have a head usually complete with two
snails have pointy spines on their shells to keep their enemies from eating
them; some have very heavy shells that discourage their prey. Some snails
have a body that comes over their shells to camouflage them from those that
would eat them, and some are poisonous to fend off prey.
have a big flat foot, which they use for locomotion and on the back end of
this foot is a structure called an operculum, which acts as a trap door
breathe through gills; however, some absorb oxygen from the water directly
through a specialized membrane (something like the thin skin lining the insides
of your cheeks) lining their mantle cavity.
of these molluscs have very colorful bodies. Some members in this class only
have a very small, fragile shell (such as bubble shells ) and it is often
contained right inside their soft bodies or they may not have a shell at all.
We know some of the Opisthobranches as: sea hares, sea butterflies (Thecostoma),
sea slugs (saccoglossans and nudibranchs), and canoe shells (Scaphandridae).
- All cone
shells possess a poisonous dart (a modified radula) with which they harpoon,
inject venom and thus killing their prey. Most are herbivores. Some cone shell
possess venom is so toxic that if stung, it can severely harm or even be fatal
members of the Carrier shell family collect seashells. These shells scientists
call Xenophoridae attach other shells or stones to their own shell for protection
and camouflage. Sometimes they even use man-made objects such as glass and
- The largest
snail (univalve) known attained a length of 78 cm (two and one half feet)
with a girth of nearly forty inches. This trumpet conch, Syrinx aruanus (Linneus,
1758), weighed in at nearly forty pounds.
- The smallest
known snail shell is the Ammonicera rota and measures only 0.02 inches in
diameter. Fifty of them laid end to end would measure one inch!
gastropods live their entire life without ever touching bottom or shore! They
float and travel on the ocean's currents. The violet snail, the Janthina,
can travel hundreds of miles in its lifetime as it floats around on the ocean's
currents. Its delicate shell only touches land when it gets washed up onto
beaches during storms.
cowries were the first item used by man for trade and a monetary system. Other
examples of this is the wampum trade beads used by the North American Indian.
dead, vacant gastropod shells become mobile homes for hermit crabs. As the
crab grows larger, it discards it's shell and moves into a larger vacant shell.
(Giant Bittersweet Clam)
their soft body is a thin membrane called the mantle (like a thick piece of
skin). The mantle takes lime and calcium out of the water and turns it into
a two-piece shell
all have this two-part shell which is hinged together. These two shell parts
are called valves. They open and close these valves by using strong adductor
muscles and ligaments much like you bend your elbow or knee.
bivalves anchor themself to hard rocks, or other objects by very fine yet
very strong byssal threads which they produce.
have an input siphon (like a short, fat drinking straw that feels like rubber)
which they use to pull in water and tiny animals that live in the water. They
extract both oxygen and their nutrients from this inflow of water. Oxygen
is filtered out in the gill then the food particles are coated with mucous
like substance and then fine hair like cilia sweep this food into their digestive
systems where they are digested. A second siphon the output syphon then returns
the filtered water back out.
- If a
foreign object such as a piece of sand gets into their soft mantle, it HURTS,
so they take the same smooth shelly material that we put on the inside of
their shell and cover the offending object up and guess what! They just made
bivalves reproduce by laying millions of eggs into the water surrounding us.
The male bivalves then release their sperm into the same water. If the eggs
and sperm meet, a new baby bivalve is born. However, some species hold their
eggs in a space called the mantle cavity in their body. The males still spurt
their sperm into the water and when she pulls this water in through her siphon,
the eggs are fertilized. These are then brooded inside her body until she
knows they are big enough to live in the water. She then releases them into
the water. All baby bivalves start life as tiny specks, (larval stage of growth)
swimming in the water. When these larva become big enough, they start to settle
onto their new homes. When they are still young, yet settled, they are called
molluscs, such as the oysters, change sex. Some like oysters even alternate
their gender. Male one year, female the next!
bivalves like to live attached to hard objects such as rocks or manmade objects.
Some live all their lives buried beneath the sandy or muddy ocean, lake or
stream bottoms. Some actually live inside wood. These bivalves (known as ship
worms) have caused man a lot of trouble when he used to sail in wooden ships.
HE ATE HOLES IN THE SHIP and it often SANK. They still attack wharfs and other
wooden man made structures causing a lot of damage. Some of my other species
are parasites, meaning that they live inside a living host, such as a fish,
and survive by eating part of the host.
bivalves swim as well. They do this by flapping their shell valves together
rapidly forces water out. This sort of like a bit of jet propulsion!valves
can be very long-lived. The ocean quahog (Arctica islandica Linne,1758), can
live to be 220 years old.
- The largest
known bivalve harvested was a Tridacna gigas(Linne, 1758), which weighed 330kg
(734 pounds), and was 1.4m (nearly four feet) in length!
are a very important food source today. Many are actually farmed for their
meat and some for their valuable pearls. Marine snail farming is called Aquaculture
Giant Pacific Octopus
reach the largest size of any invertebrate. The giant squid, Architeuthis,
which lives in the North Atlantic, may reach 17 m (56 ft) in length and weigh
three tons. This length includes the tentacles, which may measure 6 m (2 0
ft). In an animal this size, the eye is 30 cm (1 ft) across.
- All cephalopods
are all carnivorous predators (catch live food) eating such things as other
molluscs, fish and other marine invertebrates. They crush their food in a
hard beak (looks very much like a parrot's beak). Once the beak has pierced
the prey, a poison glad will inject a nasty substance into its body. The poison
paralyzes the prey and softens the meat so that the octopus can suck all of
the e flesh into its small mouth. In this way, it devours everything but the
shell. Often, a diver can locate an octopus den by looking for a pile of empty
shells that have been tossed out after feeding.
- The cephalopods
are unusual invertebrates because most lack a hard shell. The chambered nautilus
is the only type that has a complete shell. The squid and cuttlefish have
small shells that are located inside of the body, rather than outside. The
octopus, on the other hand, has lost its shell completely.
can see images, an ability that is not found in other mollusks or any other
invertebrates. They have two large complex eyes and use them to see almost
as we humans do. The eye of the giant squid may measure up to 30 cm (1 ft)
have cells in their skin, called chromataphores, which enable them to rapidly
change skin color and pattern whenever they want to. They can to change the
color of their skin so that it blends in with the surroundings or when registering
emotions such as; fear, pain, sorrow, etc.
- All cephalopods
breath through gills
cephalopods are fast swimmers. They are also known for their ability to squirt
a potential predator with "ink" and escape backwards by forcing
water from a siphon near the head. This is called jet propulsion!
threatened, cephalopod may use three deferent escape maneuvers to escape:
cephalopods have separate sexes and fertilization is internal. The males produce
a "sperm packet" which he places inside the females body using
one of his tentacles. Sometime later, the female then lays eggs. Many cephalopods
are good mothers and stay with their eggs until they hatch. They keep clean,
fresh water flowing over the eggs and caress them to keep them clean of derbies.
The young hatch out as perfect small copies of their parents.
are eaten by man.
We have also used
their ink (called sepia) in our art. This is not used as much today as since
natural sepia fades in time and man has developed superior and much less expensive
inks and dyes.
- It can sink
to the bottom, rapidly pump water out through the siphon and then bury itself
in the disturbed sand.
- It can pump
water out of the siphon and propel itself backwards.
- It can pump
a protein-based sepia ink out of the siphon and escape during the confusion.
The sepia ink may be produced as a mucus-bound blob or as a large cloud.
are very intelligent and can even learn to solve complex problems such as
seeking out food in a maze
range in size from a few inches to 3.5 m (12 ft).
have three hearts
have 8 tentacles or legs. The arms may have as many as 240 suction cups on
the underside, in two rows. These suckers make it almost impossible to remove
an octopus once it has attached to an object. If an arm is bitten off by a
predator, it will grow back over time.
- Octopus usually
remains inside of its lair unless it is searching for food.
such as octopus are highly intelligent as compared to other molluscs and have
large heads and very complex brains
- After mating,
a female octopus may lay as many as 45,000 eggs, which she attaches to the
roof of her den. She will take care of the eggs during the development period
which lasts 1-2 months. She uses her arms to remove any particles that might
settle down on the eggs and even squirts water from a siphon if necessary.
This is known as brood care. She never leaves the eggs, not even to look for
food. Unfortunately, soon after the eggs hatch and release hundreds of tiny
octopuses, the mother will die.
can squeeze their bodies through remarkably small openings. A large octopus
could easily crawl through a pop can that had been opened at both ends.
- While octopuses
are known for their intelligence, squids are known for their speed and agility.
They swim, usually backwards, using water jets. They have been known to move
as fast as 20 knots (23 mph).
- Unlike the octopus
who is solitary creature, squid swim in schools and will frequently follow
the schools of fish on which they feed.
have ten arms, two of which are called tentacles. The tentacles are longer
than the arms and have flattened ends like a spatula. Suckers are on the underside
of all the arms and only on the flattened ends of the tentacles. The tentacles
are used for feeding. The suckers, which may have hooks, help capture small
fish and shrimp, which are quickly torn apart by the beak. .
have an internal shell, called a pen, gives support to the muscular mantle.
Some squid do have a small, fragile, coiled shell inside of their body. These
tiny white coils often wash up on beaches.
do have a shell, but they do have a shelly nursery in which they deposit their
eggs and where they are incubated. This is not a true shell.
- Squids can cruise
along at constant speeds or dart about in quick jerky movements. Some have
been know to jet 3 1/2 m (12 ft) out of the water and land on boat decks.
- For protection
against predators, squid use the same methods as other cephalopods: camouflage
coloring, ink clouds and speed.
squid have special light organs which not only frighten away predators but
also help to attract food or a mate in the permanent darkness of the deep
sea. They are luminous
- Large specimens
may reach 60 cm (2 ft), while the common cuttlefish has a maximum size of
30 cm (12 in). Cuttlefish remain hidden during the day, like the octopus,
and move about to feed at night. Most only live about 18 months.
- Cuttlefish eyes
have a "W" shaped pupil and are set far apart on the face. These
animals probably have the same image forming ability as the other cephalopods.
- In front of the
eyes are eight arms and two tentacles, as in the squid. However, the cuttlefish
keeps its tentacles withdrawn in a pouch beneath the eyes. When extended,
they are long and thin with suckers on the flattened end only. The arms have
suckers all along the underside.
- Some cuttlefish
feed by hiding in the sand or seaweed with its tentacles extended, wiggling
like fat little worms. It is so well camouflaged that other animals will not
notice it. When a small fish comes closer to investigate the "worms,"
the cuttle will jet forward and grab the fish with its arms. Other cuttlefish
simply swim along, using their fins, until they see a crab or shrimp. Then
it will sneak up from behind and nab the crustacean with its suckered tentacles.
The prey is quickly carried to the arms and directed to the hard beak.
- Besides its beak,
the cuttle has another hard body structure. Like the squid, it has a shell
inside its mantle. This is the cuttlebone. When cuttlefish die, the cuttlebones
rise to the surface and wash up on beaches. These shells, sometimes called
"sea biscuits," have been used as a source of calcium and as beak
sharpeners for pet birds. Cuttlebone has also been used to relieve earaches,
stomach acid and skin diseases, among other things.
- Cuttlefish do
not produce as many eggs as the octopus and squid. Females produce about 500
tiny eggs which look like grains of rice. The eggs are laid one at a time
and attached to corals or seaweed. The females do not care for the eggs and
die soon after they spawn.
- Nautilus are the
only cephalopod which produces and external shell
- The nautilus
possess approximately 94 tentacles that arise from lobes that are arranged
in both the inner and outer circle around their head. These tentacles lack
sucker or adhesive discs. They are instead annulated and can be drawn into
a sheath. Located above the head and tentacles is a leathery hood which can
be pulled over the vulnerable soft body parts, which the animal pulls into
its shell when, threatened.
- Nautilus can swim
with surprising speed. The process for this action is the same as that in
the squid; however, the ejection of the water is produced when their body
and funnel muscles contract rather than those of the mantle.
- Nautilus often
rest on the bottom with their tentacles forming a stabilizing platform. Whether
swimming or resting, their gas filled chambers keep their shell upright at
all times. Scientists have yet to discover just how the nautilus regulates
this gas production
- Nautilus do not
have chromatophores in their skin as do the other cephalopods
- The Argonauts:
( called paper nautilus) have
arms of the female are greatly expanded at their tip to form a membrane. The
expanded portion of each arm secretes one half of a beautiful calcareous bivalved
shell. She then deposits her eggs directly into this case. The shell acts
as both a brood chamber and a retreat for the female. The posterior of the
female usually remains in this shell. The male, which is much smaller than
the female, does not have such a shell and is often found in cohabitation
within the same shell, more or less as a freeloader!
The following Three Classes
are for the more senior level of students:
for many plates
also called chitons or coat-of-mail shells
range in size from 2 millimeters to 40 centimeters (1/16 inch to 16 inches),
shells are made out of eight separate, but overlapping, plates or valves held
together by a fleshy "girdle" or skirt
- By having
several valves that can be moved separately, they are able to change the shape
of their bodies to fit onto the uneven hard rocky places they live on. Their
broad, fleshy foot holds them to the rocks so tightly that neither the violent
ocean waves nor an enemy can dislodge them easily. You would have to take
a sharp object, like a knife, to pry them off the rock and even if you did
succeed in getting them off, they would curl up into a ball. Their hard plates
would be on the outside of this ball and their soft, vulnerable body parts
are then protected on the inside of the ball.
are only found on the ocean where they generally are found clinging tightly
onto the rocks in the intertidal zone; however, a few live at depths of more
than 5,000 meters
- Most of the chitons
- They breathe in
oxygen from the water through six to eighty-eight pairs of gills.
- In some
species (Most chitons) both the male and females release their eggs and sperm
directly into the water. If these eggs and sperm meet by chance, new baby
monoplacophora are born.
times, when females draw in water to breathe, they also draw in the sperm
and thus fertilize their eggs internally . They then give live birth to their
young, all ready to fend for themselves in the sea!
is a very ancient and quite atypical class of molluscs.
are never seen in large numbers although they are widely distributed in the
oceans depths ( usually over 9,000 meter deep)
- Man scientists
feel that they are a very specialized mollusc
closely resemble an unsegmened worm and are somewhat kidney-bean shaped/
- In some
species the foot is totally absent while in other species this foot is visible
as a ventral fold
- Aplacophoran heads
are very poorly defined
appear to eat only coelenterates (jellyfish, sponge, hydra, sea anemones,
is a predominantly fossil group with only a few living species
- All are
marine species and live at depths exceeding 2,00 meters.
- In 1952,
while on the Danish "Galathea" expedition, scientists discovered
ten living specimens of Neopilina. Until that time this class was considered
possess a single symmetrical shell about 1.0 to 3.5 centimeters long and is
shaped like a cap
crawl around the ocean bottom by means of a large, round, flat foot.
their body, the organs are in pairs almost like those of the earthworm; however,
they are not segmented like a worm. They have several paired gills (one per
section) through which they breathe and one heart and kidney per body section
release their eggs directly into the surrounding water in great clouds. The
males also release their sperm into the same water. If these eggs and sperm
meet by chance, new baby monoplacophora are born.
Have students examine
the shells that have been collected for this lesson plan. With the use of
books or Internet resources (like the visual identification kit) see if
students can identify their finds. Have each student choose a shell to take
back to his or her desk to draw. Encourage them to use colour.
Students should write
up a report on a selected mollusc or molluscs. This should containe both
a drwned picture and written facts. Collect these molluscan reports, dreawings
and worksheets to mark. This will also let you know what points they have
learned and it will also help you to prepare fpr future classes
Students can also make
and cut out drawings once they are completed. Students can arrange these
cut-out shell drawings g;ue them on to the large poster board provided.Shells
can be labeled and poster displayed in class. Sample title for this is "Molluscs
We Have Found."
Provide students with
colouring sheets to colour in class, or to take home, if there's not time
in class. Discuss what colours the molluscs in the pictures would likely
be (camouflage). Continue on with any additional activities that you wish
to add to the unit.
If time and space permits,
keep the snails in their terrarium of aquariums in the classroom for several
weeks. Actually, this could become a very interesting yearly class project.
Have the students help in feeding them and keeping their home clean. Have
them observe the lifecycles of their snails. Further report or notes and
pictures should be encouraged. observations in the form of a small report
about their lifecycle could be a great long-term project
- OPTIONAL: Man and
Mollusc has a children's art and story page set up online where children may
have their works of art, stories, limericks, poems etc. placed. These can
be viewed fro the Children's Zone at: /kid_zone.html.
To have items placed on these pages, contact Avril
Bourquin and arrange for this
- Evaluate what the students
have learned (glean whether or not students are comprehending and absorbing
the information you are presenting). This can be done by discussing
and brainstorming about molluscs with students.
- Mark the snail and shell
drawings, and written reports to see what each student has been able to observe,
learn, and record about snails, and molluscs in general from this lesson.
- Consider the contribution
each student made to the brainstorm/discussion on molluscs, as well.
- Consider the ability
of each student, the accuracy of their observations, and the time they each
spent on these class projects.
- Did your students enjoy
this lesson? If not ask them how or what they would suggest you change. So
much can be learned from children. Never under estimate their contributions!
you have chosen to keep the snails in the classroom and have asked the students
to do a follow-up report on the lifecycle of the snails, make sure to collect
these and mark them based on the accuracy of their observations and the time
they've put into their project.
- Man and Mollusc web site:
by Avril Bourquin
- "Sammy 's Adventure"
story by Robynn Honeychurch, Anna Palumbo and Avril Bourquin
A Visual Identification
Kit put together by Avril Bourquin to accompany this lesson plan and can
be found on the Man and Mollusc Lesson
Plan-Checklist for Printouts
These websites also have
games, pictures and other materials you might use:
- Web pages: Many good
educational pages may be accessed through Man and Molluscs Teacher's Zone
Lesson Plan Inclusions:
Go to the Man and Mollusc Lesson Plan-Checklist
for Printouts to use the printouts you wish to use