8 Questions
What is the function of the mantle in Phylum Mollusca?
Secreting the shell
Which class in Phylum Mollusca includes mussels and oysters?
Bivalvia
How does the circulatory system differ in cephalopods compared to other Phylum Mollusca?
They have a closed circulatory system
What is the role of the radula in the mouth cavity of Phylum Mollusca?
Food rasping
Which division of the body in Phylum Mollusca is responsible for locomotion?
Foot
What is the primary economic importance of Phylum Mollusca for humans?
Source of food
Which part of Phylum Mollusca is damaged by Toredo, the shipworm?
Shell
What is the larval stage through which development occurs in Phylum Mollusca?
Trochophore larvae
Study Notes
Phylum Mollusca
- Bilateral, biploblastic, soft-bodied animals
- Body divided into head, ventral muscular foot, and dorsal visceral region
Body Structure
- Covered in glandular epithelial tissue called mantle
- Mantle secretes the shell, which can be internal, external, or absent
- Mouth cavity features a tongue-like structure called radula for rasping food
Circulatory System
- Open circulatory system, except in Cephalopoda
- Shell-less mollusks have a mantle cavity with richly provided blood vessels
Respiratory System
- Features gills, lungs, mantle, and body surface for respiration
- Well-provided with blood vessels for gas exchange
Coelom and Transport
- Coelom divided into haemocoelic channels or sinuses
- Transport occurs through open circulatory system and blood vessels
Nervous System
- Consists of three paired ganglia: cerebral, pleural, and pedal visceral ganglia
- Nerve cords connect the ganglia
Excretory System
- Features one or two metanephridia that open into the pericardial cavity
Economic Importance
- Shells used in button industry, ornaments, and for pearls
- Oysters, mussels, and clams are a food source
- Slugs and snails are pests that damage gardens and crops
- Toredo, a shipworm, damages wooden structures
Classification
- Divided into six classes, with three major classes:
- Gastropoda (e.g., garden snail, slug)
- Pelecypoda (e.g., mussels, oysters, also known as Bivalvia)
- Cephalopoda (e.g., octopus, squid, cuttlefish)
Development
- Takes place through Trochophore Larvae
Test your knowledge on the general features of Phylum Mollusca, including body division, mantle function, shell presence, mouth cavity structure, circulatory system, and respiratory system. Learn about the characteristics of these soft-bodied animals.
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