Laboratory 9 Zoology 1121
Phylum Mollusca & Evolution and Natural Selection
Quiz
I. Background
1. Large and diverse group
2. Mostly aquatic invertebrates
3. 50K species alive, 50k fossil record
4. Mollis, lat. For soft (cause soft inside a hard shell, usually)
5. you should know most of these species just from general knowledge
6. Bilaterally symmetrical
7. Phylogenetically related to annelids and arthropods
8. That is, 3 diverse phylum from 1 branch
9. Eumetazoa bilaterally symmetrical triploblastic eucoelomates
Protostomes
10. Protostomes mouth develops first before an anus during embryonic
development
11. Mollusca non-segments, unlike annelids and arthropods (insects)
12. Three main body regions woth knowing
1. head-foot: sensory organs
and locomotion
2. visceral mass: houses
the systems (digestive, excretory, reproductive)
3. mantle: covers the visceral
mass like a coat, in some secretes shell
13. Complete digestion
II. Mollusca Evolution
1. Protostomes new term to know
2. All Protostomes and Deuterostomes are eucoelomates, differ in embryological
development
3. Adaptive radiation differences in morphological structures
takes
long, long time for this (e.g.. 500 million yr.
for these)
4. AR the evolution of many distinct species from a common ancestor
after moving into a new environment
(last part about environment
is key phrasing). Read Campbell.
5. Find new niche in new environment (i.e., less competitors)
III. Classification
Phylum
1. Soft, unsegmented bodies (sometimes with a shell)
2. Open Circulatory system
3. Reduced eucoelomate
4. Has three main body regions head-foot, visceral mass, and mantle
Classes
1. Primitive with one-piece shell, marine forms only . . . . . . .
. . . . . . . . . . . . . . . . . .C. Monoplacophora
2. Eight plate shell, oval body plan and marine only . . . . . . .
. . . . . . . . . . . . . . . . . . C. Polyplacophora
3. Tubular shell . . . .
. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . ,. . . . . . . . . . . ..C. Scaphopoda
4. Shell usually absent, foot divides into tentacles . . . . . . .
. . . . .. . . . . . . . . . . . . . . C. Cephalopoda
5. Two-piece shell . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . .C. Bivalvia
6. Spiral Shell that encloses only the visceral mass . . . . . . .
. . . . . . . . . . . . . . . . . ...C. Gastropoda
IV. C. Monoplacophora
1. Primitive mollusks
2. only found really recently, no demo of this because hard to find
[i.e., specimens to test you on]
3. One shell dorsal to their soft bodies
V. C. Polyplacophora
1. dorsal shell plates
2. common name is chitons
3. plates are hinges to allow bending [not segmented remember requirement
for phylum is non-segmented]
VI. C. Scaphopoda
1. common name for tooth shells (long and tubular)
2. they are burrowing organisms
3. interesting that they have NO gills, unlike all others
4. respiration through mantle
VII C. Cephalopoda
1. No obvious shell except for chambered nautilus
2. Common name for octopi, squids, cuttlefish, chambered nautilus
3. Elongated head & long foot modified into tentacles
4. Well developed eyes
5. Squids show social hierarchy, social hunting, etc. [very advanced]
6. Gills inside mantle not next to
7. Chambered nautilus have inverted digested tract (bent back around
toward front)
8. Shell filled with gas for buoyant
VIII C. Bivalvia
1. common name for clams, oysters, and scallops
2. Two similar shells that close upon each other
3. Head-foot not well developed
4. External anatomy:
a. umbro slightly enlarged
dorsal point that lies adjacent to attachment of the two valves
b. two adductor muscles
hold shell halves together
c. hinge teeth
d. hinge ligament
e. mantle covers the soft
body attached dorsally to shell but free ventrally
f. siphons one for in-current
(ventrally), one for out-current (dorsally)
g. gills respiration and
site of food gathering
h. labial palps surround
its mouth
i. anus at far end
j. visceral mass
k. mouth esophagus stomach
intestine anus
l. digestive gland surrounds
stomach and esophagus
m. gonads surrounds the
intestines
n. dorsal and posterior
is pericardial membrane which encloses a cavity
o. has long ventricle draped
over the intestines
p. ventricle pump to pump
blood in aorta to mantle and other body organs
q. tubelike nephridia
excretion of wastes, u-shaped and ventral to pericardia
r. Ganglion not a brain,
but nerves for integration of sensory input and motor output
IX. C. Gastropoda
1. common name for snails and slugs
2. marine, terrestrial, freshwater
3. Some have shells, usually spiral
4. Has a twisted visceral mass that forces digestive tract around upon
itself
5. Twisting process called torsion
X. Natural Selection [a mechanism for Evolution]
1. Evolution things change over time
2. Many, many scientists talked about evolutionary theory before Darwin
3. C. Darwin actually first to come up with a cogent mechanism for
how this evolution could actually take place.
4. His mechanism is called Natural Selection
5. More and more examples are found in nature that makes NS still viable
today (over 130 yrs!)
6. NS defined [must memorize this] NS is differential survival
and reproduction rates in a population over time
7. Five Assumptions of NS
a. More animals produced
than can actually survive
b. Natural variation exists
among individuals
c. This variation in form
of traits
d. Better traits mean better
able to survive and pass on these traits
e. Long geologic time for
this to occur
8. read Campbell book for great review not contained in this lab book
*********
IMPORTANT TERMS:
Monoplacophora
Polyplacophora
Cephalopoda
Gastropoda
Bivalvia
Chelicerata
Unirama
Crustacea
Merostomata
Arachnida
Chilopoda
Diplopoda
Hexapoda
Malacostraca
Evolution
Natural Selection
Five assumptions
1.
2.
3.
4.
5.
Adaptive Radiation
(MOLLUSCA)
Umbo
Hinge
Retractor muscle
Ant./Post Adductor muscle
mantle
incurrent/excurrent siphons
gill
visceral mass
foot
digestive gland
labial palps
intestine
stomach
pericardial membrane
ventricle
nephridium
bladder
nephridiopore dont have to know
gonad
(CRAYFISH)
Antennule
Antenna
Mandible
Chiliped,
Walking legs
Swimmerets
Claspers
Uropod
Head
Thorax
Abdomen
Cephalothorax
Flexor muscle
Heart
Pericardium
Ostia
Gonads
Testes
Ovaries
Digestive gland
Mouth
Esophagus
Cardiac stomach
Pyloric stomach
Gastric mill,
Intestine
Anus
Green glands
Brain
Y-organ, x-organ - dont have to know these