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BIOL 111 Study Guide - Final Guide: Pneumostome, Love Dart, Mollusca

Biology (Sci)
Course Code
BIOL 111
Suzanne Gray
Study Guide

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Phylum Mollusca Terrestrial Snail
Phylum Mollusca is 2nd in number and diversity, after arthropods
Snails are hermaphrodites, therefore the can reproduce asexual and sexually.
Sexual Reproduction:
Snails secrete a chemical attractant called pheromones, which attract
other snails
Undergo ritualized courtship, which involves the touching of tentacles and
feet for several hours
Sperm is stored, until the egg is ready to be fertilized
Polygamous relationships occur, therefore there is a competition when it
comes to which sperm will fertilize the egg
Love dart: snails produce a love dart which is a layer of mucus coating
surrounding the sperm to ensure the survival of the sperm
Shell: composed of calcium carbonate secreted from the epidermis,
some mollusca’s contain an operculum (hard disk on the foot) however
snails do not have one of theses
Foot: strong foot, assists in locomotion, secretes a sticky mucus
substance that allows the snail to grip and slide along the surface, the
mucus also assists in reduction of water loss, as there is a strong
adhesion between the snail and the substrate
Tentacles: two pairs of tentacles that are used for olfaction (small/taste)
1. Inferior tentacle: shorter tentacle, detects chemicals on the grounds
2. Superior tentacle: longer tentacle, detects airborne chemicals,
contains photoreceptors in the tips, eyes are located here
4 different types of locomotion:
1. Monotaxic: wave of contractions along the width of the foot
2. Ditaxic: wave of contractions alternate between right and left
3. Direct waves: involves the lifting of the posterior edge, and placing it
forward forward wave of contraction
4. Retrograde waves: involves the lifting of the anterior edge, stretches and
attaches forwardly backwards wave of contractions
Snails have direct and monotaxic types of locomotion.
Aquatic mollusks: breathe through their gills
Terrestrial mollusks: gas exchange occurs across their mantle (moist
surface) rhythmic opening and closing of a pore called the
pneumostome which allows gas to enter into the “lungs” during
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