Questions and Answers
What is the general character trait which distinguished Mollusks?
They are soft-bodied animals that have an internal or external calcium carbonate shell
How diverse is the phylum Mollusca?
They are the second most diverse phylum of animals after the arthropods
Many Mollusca species serve as food for humans.
True
Are most mollusks slow or fast?
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What is the symmetry of Mollusks?
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Are Mollusks diploblastic?
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Do Mollusks have a true coelom?
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Mollusks have larger coelom than annelids.
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Do Mollusks have complete digestive systems?
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What is a protostome?
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What is a deuterostome?
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Is a Mollusk a protostome?
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What other systems do Mollusks have besides a complex digestive system?
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Are Mollusks similar to annelids in their development?
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How are mollusks different from annelids from a developmental point of view?
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What three body regions do all mollusks have?
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What is the function of the foot in a mollusk?
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What is the function of the visceral mass in a mollusk?
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What is the function of the mantle in a mollusk?
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What is the function of the mantle cavity?
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The continual flow of water or air throughout the mantle cavity along with the physical and physiological organization of the mantle, mantle cavity, and gills allows the mollusk to __________________________ and __________________________.
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Many Mollusks feed by using a strap-like organ called a ______________.
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What process has resulted in lots of morphological variety within this phylum?
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How many classes of mollusks are we studying and what are their names?
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How do organisms amongst the different classes of mollusks differ from one another?
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What is the basic anatomy of an organism belonging to class Polyplacophora?
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What kind of organisms are chitons?
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Describe the foot of chitons.
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Where can chitons be found?
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Study Notes
General Characteristics of Phylum Mollusca
- Mollusks are soft-bodied animals, often possessing an internal or external calcium carbonate shell.
- They rank as the second most diverse phylum in the animal kingdom, following arthropods.
Importance and Locomotion
- Many mollusk species serve as a food source for humans.
- Most mollusks are slow, although some, such as squids, are capable of rapid movement.
Body Structure and Symmetry
- Mollusks exhibit bilateral symmetry.
- They are triploblastic, developing from three germ layers.
Body Cavity and Digestive System
- Mollusks have a true coelom, which is a body cavity entirely surrounded by mesoderm.
- They possess complete digestive systems, allowing for efficient processing of food.
Developmental Classification
- Mollusks are classified as protostomes, where the mouth develops from the blastopore.
- In contrast, deuterostomes develop the anus first from the blastopore.
Physiological Systems
- Mollusks have elaborate respiratory, excretory, and circulatory systems, including a heart.
Morphological Differences from Annelids
- Unlike annelids, mollusks lack segmentation.
- Both groups share a trochophore larval phase but differ significantly in development.
Body Regions of Mollusks
- Mollusks are comprised of three main body regions: foot, visceral mass, and mantle.
Functions of Body Structures
- The muscular foot serves primarily for locomotion.
- The visceral mass houses internal organs.
- The mantle is a tissue layer that surrounds the mantle cavity, responsible for shell production.
Mantle Cavity Functions
- The mantle cavity allows for continual water or air circulation, facilitating gas exchange and food gathering.
- Gills are located within the mantle cavity.
Feeding Mechanism
- Many mollusks utilize a radula, a strap-like organ, for feeding.
Evolutionary Adaptations
- Diversification in mollusks is attributed to evolution by natural selection, leading to diverse morphologies adapted to various environments.
Classes of Mollusks
- The five classes studied are:
- Polyplacophora (chitons)
- Bivalvia (clams)
- Gastropoda (snails)
- Cephalopoda (squids)
- Scaphopoda (tusk shells)
Class Differences and Anatomy
- Each class of mollusks exhibits variations in the shapes and arrangements of the three main body parts, leading to functional differences.
- Polyplacophora features an elliptical body covered by a shell made of eight plates, though some species may lack these.
Chitons
- Chitons are marine herbivores that graze on algae from rocks.
- Their broad, flat muscular foot occupies a significant portion of the ventral surface and enhances their ability to cling to surfaces.
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Description
Test your knowledge on the characteristics and diversity of Mollusca in this Biology 112 quiz. Explore key traits that make Mollusks unique and their significance in ecosystems and human nutrition. Ideal for students seeking to reinforce their understanding of this fascinating phylum.
