Phylum Mollusca - Mrs. Skakal's BVW...
Transcript of Phylum Mollusca - Mrs. Skakal's BVW...
Phylum Mollusca
● molluscus means “soft”● soft-bodied animals that have an internal or
external shell● include: snails, slugs, squid, octopi● share similar developmental stages
What is a Mollusk?
Has 4 parts:● foot- muscular (can be: flat, spade-shaped,
tentacles)● mantle- layer of tissue that covers most of the
body● shell- secreted by the mantle ; has been lost or
reduced in some mollusks● visceral mass- consists of internal organs
Body Plan
Varies● herbivores● carnivores● filter feeders● detrivores● parasites
Feeding
Snail & Slugs use a radula for feeding:● flexible tongue-like structure covered with hundreds of teeth● scrape algae; drill holes in shells
Octopi use sharp jaws to eat prey:● some produce poisons
Clams, oysters & scallops filter feed:● use a siphon to move water in and out of body
Feeding
● aquatic mollusks breathe using gills inside mantle cavity
● land snails/slugs respire with mantle cavity that has large surface area○ oxygen diffuses across the surface of the
mantle
Respiration
Can be an open or a closed circulatory system:● open circulatory system- blood is pumped through a
simple heart into cavities called sinuses○ works well for slow-moving mollusks (snails,
clams)● closed circulatory system- blood pumped through
heart and blood vessels○ works for fast-moving mollusks (squid, octopi)
Circulation
How does a closed circulatory system benefit a mollusk who moves quickly?
● cells release nitrogen-containing waste in blood in form of ammonia
● nephridia remove ammonia from blood and release from the body
Excretion
Varies:● Bivalves (clams, oysters) have simple nervous system
○ ganglia○ nerve cords○ sense organs○ eyespots
● Octopi have highly developed nervous system:○ can remember things○ can perform complex tasks
Response
http://www.youtube.com/watch?v=ocWF6d0nelY
http://www.youtube.com/watch?v=SCAIedFgdY0
Many different ways:● snails- secrete mucus & use their foot● octopi- jet propulsion
Movement
Varies:● sexual
○ external fertilization (bivalves)○ internal fertilization (octopi, squid, some
snails)○ hermaphrodites (do not fertilize themselves)
Reproduction
Gastropods (Gastropoda: stomach- foot)● without a shell or have a single shell● move by using a muscular foot● include
○ snails○ nudibranchs○ slugs
Groups of Mollusks
Bivalves (Bivalvia: 2 hinged-shells)● 2 shells held together by 2 muscles● stationary most of the time● Include:
○ clams○ oysters○ mussels
Cephalopods (Cephalopoda: head-foot)● soft-bodied● head attached to foot● foot divided into tentacles/arms● Include
○ octopi○ squid○ cuttlefish
Write a response to the video: “Kings of Camouflage”● What did you find the most interesting about cuttlefish?● What surprised you?● What did you learn?
Write a paragraph (5-8 sentences)