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BIO 2135 Study Guide - Midterm Guide: Soltyrei, Ejaculatory Duct, Clypeus

Course Code
BIO 2135
Jon Houseman
Study Guide

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Animal Form and Function
Midterm #2 Keywords
Abductor muscle: a muscle that moves any part of the body away from the central midline -in
brachiopods, it opens the bivalve shell; it is complementary to the adductor muscle in most muscular
systems; it is absent in clams
Adaptive radiation: evolution of a variety of different species from a single common ancestor; each is
adapted for a particular niche; the appearance of the descendants may vary considerably from each other
and the ancestor; molluscs are an example of adaptive radiation
Adductor muscle: a muscle that moves part of the body toward the central midline; in brachiopods and
bivalves, it closes the bivalve shell; clams only have an adductor muscle; it is complementary to the
abductor muscle in most muscle systems
Albumin gland: part of the snail reproductive system (gastropods in general) -produces the yolk that
nourishes the snail embryo -compound tubular gland located near the top of the sperm duct/oviduct
underneath the top of the visceral mass
Atrium: a chamber that affords entrance to another structure or organ -usually refers to an atrium
(chamber) of the heart -in gastropods, there is only 1 atrium to the heart, compared to 2 that is normally
Bioluminescence: how living organisms produce light -many organisms that live in the deep dark depths
of the ocean or in other environments at
Branchial heart: modification of the circulatory system to form secondary hearts that pump blood into the
gills (cephalopods) - it is located underneath the systemic heart in squids -part of the closed circulatory
system in squids -function under predominantly anaerobic conditions; only circulate venous blood
Cecum: part of the digestive system of cephalopods, also found in bryozoans -in cephalopods, it is in
between the stomach and the intestine --it receives undigested food material -the main function is to
absorb fluid & salts that remain after initial digestion in the stomachs
Ciliated sorting field: part of the aggregate mollusc digestive system -lines the intestines of the mollusc -
increases the surface to volume ratio for absorption of nutrients -sorts small organic matter after digestive
enzymes have been secreted from the crystalline style & sweeps small particles into the digestive gland
for further digestion
Ciliated ventral foot: a series of contractions on either side of the snail that help propel the mollusc -used
in combination with mucus -used in locomotion; uses the metachronal wave action of the cilia
Crystalline style: a rod-like structure in some mollusc stomachs made of enzymatic proteins required for
digestion -cilia lining the stomach rotate the crystalline style, which grinds against the gastric shield to
release the digestive enzymes -located beneath the gastric shield and above the style sac
Ctenidium: molluscan gills that often have additional functions other than respiration -the ctenidia are
used in respiration - molluscs have ctenidia inside a space that is covered with cilia which creates a
unidirectional flow through the mantle cavity -this moves water over the surface of the ctenidia; the cilia
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propel water through & as the water leaves the space, it takes away the wastes from the
digestive/excretory system
Dart sac: contains a special dart that is used in mating -the dart is rammed into the partner in mating
battles -it used to be thought of as a stimulant, but we now know that whoever gets the dart will be the
receiver of the sperm -it is a mechanism to ensure that one individual is more likely to transfer sperm than
the other
Digestive gland: many invertebrates, including molluscs, arthropods and echinoderms have pockets or
invaginations from the main alimentary tract where specialized digestive events occur -they are
specialized to break down nutrients in the body -in the aggregate mollusc, they are located just beneath
the esophagus
Elastic capsule chromatophore: specialized pigmented cell on the surface of cephalopods that, b y
changing its shape exposes differing amounts of pigment changing the colour and appearance of the
cephalopods -helps in camouflage & bioluminescence -work along with iridiocytes (mirror cells that
reflect light); it will absorb certain wavelengths & reflect others back depending on the amount that it has
contracted or expanded
Excurrent siphon: tube-like structures in which water flows (or more rarely in which air flows) -used for
locomotion, feeding, respiration and reproduction -part of the mantle of the mollusc & the water is
directed away from the mantle cavity
Gastric shield: located inside the stomach -is hard -wears part of the crystalline style and dissolves mucus
of the aggregate mollusc
Glochidia: free swimming, larval stage of some freshwater, bivalve molluscs -brooded inside the gill
chamber -after release, they parasitize fish until the glochidia's development is omplete
Hectocotylus arm: one of the arms of male cephalopods that is modified and specialized to transfer sperm
to the female in order to fertilize her eggs - the male squid takes the arm, reaches up into the mantle,
transfers the spermatophores to the arm & inserts the arm inside the female, depositing the sperm package
at the opening of the female genital tract
Hermaphrodite duct: part of the gastropod reproductive system -combined sperm duct & oviduct -serves
as both because the snail is hermaphroditic -the dart determines which mating partner will be the receiver
of sperm
Hinge ligament: part of the bivalve shell; join together the two valves at the dorsal edge of the shell (2
valves = 1 half of the shell) -the ligament is made of a strong, flexible and elastic, fibrous, proteinaceous
material -the shell needs to be able to open a little to allow the foot and siphons to protrude & then close
again -the hinge ligament functions as a spring which automatically opens the valves when the adductor
muscles relax (muscles that close the valves)
Incurrent siphon: this time the function is to bring the water towards the mantle cavity
Ink sac: contains ink used as a defense mechanism in cephalopods/ -located just in front of the anus -
blinds the enemy momentarily so that the cephalopod has time to get away if camouflage doesn't work
Iridiocytes: specialized cells that work with chromatophores -mirror cells that reflect light -the reflection
of the light determines the wavelengths of light that will be absorbed and thus change the colour of the
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Labial palp: found in bivalves -secrete a mucus that entangles suspended food & nutrient particles within
the water to produce a ball of food & mucus -afterwards, the cilia on the palp directs the bolus (ball of
food & mucus) into the mouth
Mantle: a thin, sheetlike membranous extension of the visceral mass of molluscs and brachiopods that
forms 2 flaps of skin -mantle secretes the shell on the dorsal side -the space between 2 flaps of skin is
referred to as the mantle cavity
Metanephridium: an excretory-osmoregulatory organ consisting of a ciliated funnel, nephrostome
connected to the external nephridiophore -the nephrostome collects coelomic fluid and all of its contents
to produce the organ -located close to the heart & intestine -paired structure in all molluscs except for
Nacre: also known as mother of pearl, it is an organic-inorganic composite material produced by some
molluscs (bivalves in particular) as an inner shell layer -it makes up the outer coating of pearls how we
end up with pearls; so that dirt doesn't rub up against the epithelial layer and damage it
Nacreous layer: the innermost layer of the 3 layers of a mollusc shell -also referred to as a mother of pearl
-consists of thin layers of calcium carbonate crystals (aragonite) -it is continually produced by the mantle
Nephridiopore: external openings to nephridia (proto & meta) in invertebrate excretory system -
polychaetes (like nereius) typically release their gametes into the water column using nephriodphores -
analogous to nephrons -consists of an opening called the nephrostome, a long convulated tubule &
another opening called the nephriodiopore
Nephrostome: the funnel-like component of metanephridium -always oriented towards the coelom -
covered from the inside with cilia, which push the water, metabolic wastes, unnecessary hormones &
other substances into the metanephridium
Nidemental glands: part of the reproductive system in mollusca -they produce nutrients for the egg -they
are quite large and prominent; located beneath the oviducal glands
Odontophore: on the surface sits the radula -part of the feeding mechanism in molluscs -it is the cartilage
which underlies & supports the radula
Open circulatory system: a circulatory system in which the circulating fluid (blood) flows into vessels or
tubes not connected to each other by small capillaries -instead it enters in into the hemocoel before
returning to the heart -characteristic of bivalves (clams)
Ovotestis: a gonad with both testicular and ovarian aspects -part of the gastropod reproductive system -
they sit at the top of the whorl -are surrounded by the digestive gland & hermaphproditic duct that leads
down to where the eggs are fertilized
Pen: the internal shell of a squid - the remnant of the ancestral shell - a feather shaped internal structure
that supports the squid's mantle & serves as a site for muscle attachment -it is made of a chitin-like
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