Wize High School Grade 11 Biology Textbook > Invertebrates: Part 1 - Non-Molting [Under construction]
Mollusca (Snails, Clams and Squid)
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Phylum Mollusca (Snails, Clams, and Squids)
This is an incredibly diverse group, some of which are incredibly intelligent. Octopus can learn how to solve puzzles by watching other individuals!
- Includes snails, clams, squids, etc.
- Mostly marine, some freshwater and terrestrial
- Have calcareous shells for protection
- Many have lost these shells secondarily
Characteristics
- Mantle: secretes shell
- Ventral foot: large muscular foot used for movement
- Organs: jumbled visceral mass above foot
- Radula: mouthparts used for scraping
- Gills: used for gas exchange or feeding Example: bivalves (clams) use gills to filter water for food
- Open circulatory system
- Reduced Coelom
- Lack segmentation
- Trochophores (free swimming larvae)
Class Gastropoda
- Snails
- Movement
- Glide along with muscular contractions of the large foot
- Most have single, coiled, tubular shell
- Except slugs which have no shell
- Those with shells undergo torsion
- Anus is twisted to the front (above the head)
- Mostly marine but many freshwater and terrestrial
- Trochophore larvae
- Gas exchange via lungs
- Grazers
- Nudibranchs: marine gastropods with no shell
- Lots of color
- Defense using nematocysts stolen from cnidarian prey
Class Bivalvia
- Clams, oysters, scallops
- Humans use them for
- Food
- Jewelry
- Pearls
- Some are invasive pests
- Mostly marine
- Two hinged shells ("bivalve")
- Feeding
- Filter water through gills
- Lack radula
- Lack head
- Some are sessile others are sedentary Example: Scallops can move by "clapping" their shells
Class Cephalopoda
- Squids, cuttlefish, octopuses
- Large bodies
- Low diversity
- Have long tentacles around mouth
- Tentacles have suckers and hooks
- All are predatory
- Radula is modified into a biting beak
- Some have poison
- Lack external shell
- Except nautiluses and extinct ammonites
- Some have Internal shell remnants Example: Cuttlefish bone
- Siphon
- Made from a tube of mantle
- Used for jet propulsion
- Closed circulatory system
- Only mulloscs with it
- Support active lifestyle
- Reproduction
- Attach egg cases to substrates
- Maternal Care
- Lack trochophore larvae
- Direct-developing juveniles
- Excellent vision
- Complex behavior
- Communicate with color and posture
- Very intelligent!
Practice: Mollusca
Which of the following structures do mollusks have? (select all that apply)
Practice: Mollusca
What type of mollusk has the following features?
1.) Jet propulsion
2.) Tentacles
3.) Maternal Care
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