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BIOL 111 Study Guide - Final Guide: Sperm Donation, Phototaxis, Chemotaxis

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

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Lab 6 Invertebrates II
Phylum Mollusca
Second only to arthropods in terms of number and diversity
Example: terrestrial gastropod (brown garden snail) Cantareus aspersus
Herbivorous, feeding on terrestrial vegetation
External Anatomy: very strong foot, therefore difficult to pick up when attached
to a surface
Shell: composed of CaCO3 and proteins secreted from the mantle
o Many species have a hard dark disk, called an operculum,
on the dorsal surface of their foot; when retracted, this
structure acts like a lid, sealing the snail within its shell
Foot: controls locomotion; specialized glands produce and secrete
mucus along which the snail grips and slides
o Mucus produced by the foot can be used to reduce water
loss, lo allow strong adhesion to a substrate and to form
egg cases produced after fertilization
Tentacles: two pairs of tentacles on their head; used for olfaction
(smell/taste). Chemoreceptors are located within the tentacles
o The shorter the inferior tentacles are used to detect
chemicals on the ground
o The longer superior tentacles are used to detect airborne
chemicals (possess photoreceptors at their tips)
Does a snail have an operculum? No
On which pair of tentacles are the eyes located? Superior tentacles
Locomotion: four different ways locomotion may be achieved
1. Monotaxic: the wave of contractions can extend across the width of
the foot
2. Ditaxic: can alternate between the right and left sides
3. Direct waves: involves the lifting of the posterior edge of the foot and
forward placement, followed by a forward wave of contractions
4. Retrograde waves: involves the lifting of the anterior edge of the
foot, the stretching and attachment of it in a more forward location and
a backward wave of contractions
What type of locomotion does the snail use? Monotaxic; direct
Taxis: used to refer to movement in a particular direction, either towards
(positive taxis) or away from (negative taxis) a particular stimulus
Phototaxis: movement due to light
Geotaxis: movement due to obstacles
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