Phylum Mollusca
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Transcript of Phylum Mollusca
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Phylum MolluscaPhylum MolluscaChapter 13: Phylum Molluscapp. 329-334
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Biology fun facts of the day:
Experts claim that about 1,000
oysters must be opened in order to
find one usable pearl!
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Biology fun facts of the day:
The common garden snail, Helix aspersa, can travel about
2 feet in 3 minutes. At that rate, it would travel 1 mile in
5.5 days.
(Now you know where the term ‘snail mail’ comes from!)
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Biology fun facts of the day:
When we hold a large seashell up to our ear, you can hear what
sounds like waves because the shell echoes all the sounds
around you.
If you could listen to a shell in a completely soundproof room, you
would hear nothing at all!
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Biology fun facts of the day:
Many land snails can lift 10 times their own weight up a vertical
surface. (If you were this strong, and you weighed 30 kg (about 70
lb), you could carry 300 kg (almost 700 pounds!!!) straight
up a wall!
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Introduction to MolluscsIntroduction to MolluscsMolluscs represent the second largest animal phylum, following the arthropods
= Old Phylum (500 million years, approx.)
80,000 – 100,000 existing species (estimate)
Most species are free-living
Inhabit a variety of marine, aquatic & terrestrial habitats
Important ecological roles with regards to nutrient recycling; bivalves clean and recycle sediments
Empty shells provide habitat for other invertebrates
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Where do Molluscs fit in?Where do Molluscs fit in?
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Introduction to MolluscsIntroduction to MolluscsPhylum Mollusca – Latin molluscus = “soft”ProtostomesBilateral symmetry; eucoelomates3 cell layers (ectoderm, endoderm,
mesoderm)Have a coelom (but often reduced to a
cavity that surrounds only the heart)Have trochophore larvae (free-swimming
ciliated larva)• Similar larvae in annelids
likely share a common ancestor
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Introduction to MolluscsIntroduction to MolluscsMolluscs all share similar developmental patterns and a common body plan:Foot (muscle; function varies)Shell (protection; made of CaCO3)Mantle (produces the shell)Visceral mass (contains internal organs)
Diagrams of snail, clam, and squid p.
300
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Classes of MolluscsClasses of Molluscs1) Class Bivalvia
• 2 hinged shells• No head or eyes• Gills; live in water
Example members: clams, oysters, scallops
2) Class Gastropoda• One shell• Some are terrestrial
Example members: snails, slugs, nudibranchs
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Classes of MolluscsClasses of Molluscs3) Class Cephalopoda Fast-moving predators Foot is modified into tentacles Well-developed nervous system Some can use camouflage and jet
propulsion (e.g. octopus) when they feel threatenedExample members: octopus, squid, nautilus, cuttlefish
Octopus
Nautilus
Squid
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Squid are the largest Squid are the largest CephalopodsCephalopods
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Colour and Morphology Colour and Morphology Changes = CamouflageChanges = Camouflage
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Form and Function of Form and Function of MolluscsMolluscsMolluscs vary a lot clam = representative molluskDigestive system: •Complete digestive tract (mouth anus)
• Mouth, esophagus, stomach, intestine, anus•Have a radula (scraping/drilling organ) or a beak (cephalopods)•Bivalves trap food in their gills – no radula
e.g. Gastropod
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Form and Function of Form and Function of MolluscsMolluscsRespiratory system: • Aquatic mollusks have gills• Terrestrial mollusks have a highly folded
mantle for O2/CO2 exchange (must stay moist)
*A clam has incurrent and excurrent siphons sea water passes through; location of gas exchange
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Circulatory system:• Open circulatory system – the heart
pumps blood through open spaces called sinuses instead of through blood vessels
Excretory system: • Nephridia (primitive kidneys) remove
metabolic waste (nitrogen-containing wastes like NH3)
• Digestive wastes go out anus
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Nervous system:• Bivalves – reduced nervous system; no
head• Gastropods – fairly basic• Cephalopods – very well developed
• Good vision, small ganglia near mouth, statocysts (balance), simple chemical and touch receptors
• Good dexterity and memory – they can learn!
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Musculoskeletal system:• Muscular foot for movement• Bivalves – “two shell”; foot pulls animal
forward, and can be sucked back in (for protection)
• Gastropods – “stomach foot”; they slide forward on broad ventral foot (use muscus)
• Cephalopods – “head foot”; foot has been modified into many tentacles with suction cups
e.g. Gastropod
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Reproduction:•Some Monoecious (have both sex organs, capable of producing both sperm and eggs)•Others are Dioecious (either male or female gonads, can produce one type of gamete only)
•Separate sexes (usually)
•External fertilization (broadcast method) in bivalves/marine gastropods) the female traps sperm
•Internal fertilization in cephalopods/terrestrial gastropods
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Ecology of MolluscsEcology of MolluscsBivalves used to check pollution levels –
“environmental monitors”Range of lifestyles: predators, scavengers, filter
feeders, etc.Crop damage – slugs, snails on landShip damage – shipworms in waterFood source for humans: clams, oysters,
mussels, etc.• Humans can get poisoned by eating mollusks contaminated with toxic protists cause “red tide”
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Molluscs Movie!Molluscs Movie!
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Mollusc (5-7-5) Haiku:Mollusc (5-7-5) Haiku:Slow, slick, sliding slugTerrestrial explorerNo protective shield
Create your own mollusc haiku in 5-7-5 format!
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Works CitedWorks CitedImages taken from the following
sources:http://other95.blogspot.com/2007/10/circus-of-
spineless-26-like-being-home.htmlhttp://offthemark.com/search-results/key/mollusk/http://kevinmainjewelry.blogspot.com/2010/06/pearl-fun-facts-and-care-tips.htmlhttp://seashellvilla.com/advertise_here.htmlhttp://www.zazzle.com/snail_mail_postcard-239469706654312651http://bio1151b.nicerweb.com/Locked/media/ch32/trochophore.htmlhttp://www.education.com/study-help/article/biology-help-mollusks-clam-up-would-ya/
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Works CitedWorks Citedhttp://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCESearchMedia&Params=A1&MediaId=385http://perfectgardeningtips.com/category/plants/pest-control/http://www.apartmenttherapy.com/sf/insects-pests/slugs-082896http://birdhouse.org/blog/2008/05/16/nudibranchs/http://www.zazzle.com/i_squid_cephalopods_tshirt-235319078835508111https://www.mentalfloss.com/blogs/archives/58856http://radio-weblogs.com/0105910/2004/01/10.htmlhttp://ihatetheocean.blogspot.com/2010/08/august-6-2010-nautilus.htmlhttp://zollberg.co.cc/bivalve.html
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Works CitedWorks Citedhttp://js082.k12.sd.us/My_Classes/Advanced_Biology/
Ch_25/Clam%20Dissection/Clam_Dissection.htmhttp://www.sciencewithme.com/learn-about-mollusks/http://www.bio.miami.edu/dana/106/106F06_12.htmlhttp://nashzoology.ning.com/forum/topics/mollusk-
classification-choose?commentId=2223964%3AComment%3A10692&xg_source=activity
http://sharon-taxonomy2009-p3.wikispaces.com/Mollusca
http://www.lifeinfreshwater.org.uk/Web%20pages/ponds/Pollution.htm
http://www.nero.noaa.gov/nero/hotnews/redtide/http://www.sheppardsoftware.com/content/animals/
profile_mollusks.htm