Mollusk Basics
What material makes up the hard shells of many mollusks?
Calcium Carbonate (CaCO3)
What is the largest and most diverse class of mollusks?
Gastropoda
What structure forms the internal mass containing a mollusk's digestive, reproductive, and respiratory organs?
Visceral mass
What is the name of the tooth-covered feeding structure used by many mollusks to scrape food?
Radula
What percentage of mollusk species live in the ocean: most or very few?
Most
What type of symmetry do most mollusks have?
Bilateral symmetry (sometimes asymmetry ... some snails)
Which class includes squid, octopuses, cuttlefish, and nautiluses?
Cephalopoda
What structure do clams use to burrow into the ocean floor?
Muscular foot
What type of circulatory system do clams, oysters, and mussels have?
Open circulatory system
What type of relationship do mollusks have with food webs? Are they important or unimportant?
They play important roles as predators, prey, filter feeders, and decomposers in food webs.
Mollusks are triploblastic, protostomes, and what type of animals are they based on their body cavity?
Coelomates
Which class includes clams, oysters, and mussels, and is characterized by having two shells?
Bivalvia
What structure does a squid use to forcefully shoot water out of its body to propel itself forward?
Siphon
What organs do aquatic mollusks typically use for respiration, and what structure do land snails use instead?
Aquatic mollusks use gills; land snails use a simple lung (mantle cavity).
What is a hermaphrodite, and which common mollusk from the gastropod class is an example?
An organism that has both male and female reproductive organs. Slugs are an example.
What are the three major body regions found in the typical mollusk body plan?
Muscular foot, visceral mass, and mantle
What class contains chitons, which have eight overlapping shell plates?
Polyplacophora
What are chromatophores, and how do squid use them?
Pigment-containing cells that allow squid to change color for camouflage and communication.
What is the name of the organs that remove nitrogenous wastes from a clam's body?
Nephridia
How are pearls formed inside certain mollusks?
An organism that has both male and female reproductive organs. Slugs are an example.
Explain how the name "Mollusca," meaning soft-bodied, describes the animals in this phylum. Why do many mollusks have shells?
Mollusks are soft-bodied animals. Many have shells produced by the mantle that protect their soft internal organs and body.
Identify the mollusk class described by each characteristic: captures food with captacula, includes tusk shells, and commonly lives buried in the ocean floor.
Scaphopoda
Explain the difference between the way a clam, a snail, and a squid use their muscular foot for movement.
Clams use their foot to burrow; snails use it to crawl; squid have a modified foot that forms structures including the siphon and arms/tentacles.
Compare the circulatory systems of cephalopods and bivalves. Which has a closed circulatory system, which has an open circulatory system, and what is one advantage of a closed system?
Bivalves have an open circulatory system where hemolymph leaves blood vessels and bathes organs. Cephalopods have a closed circulatory system where blood remains within vessels. A closed system allows more efficient delivery of oxygen and nutrients.
Choose either zebra mussels or giant African snails. Explain how your chosen species became invasive in the United States and describe two negative impacts it has on the environment or humans.
Zebra mussels: Introduced through ballast water from ships. They reproduce rapidly, clog water intake pipes, outcompete native species, and alter aquatic ecosystems. Giant African snails: Introduced through human activities, including the pet trade. They damage crops and native plants and can carry parasites harmful to humans.