BIOLOGY 2402
GENERAL ZOOLOGY
LABORATORY TERMINOLOGY
AND
ACCESSORY MATERIAL
A GUIDE TO WHAT IS REQUIRED FROM LAB MANUAL EXERCISES
Revised August 2009
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EXERCISE 1 – THE MICROSCOPE
Exercise 1A – COMPOUND LIGHT MICROSCOPE
base
in-base illuminator
iris diaphragm lever
stage
coarse adjustment knob
fine adjustment knob
transformer control knob
objectives:
scanning-power (4X)
low-power (10X)
high-power (40X)
oil immersion (100X)
parfocal lens
nosepiece
ocular (10X)
interocular distance scale
*Note: Never use the coarse adjustment knob while looking at an object with a high-powered lens.
**Omit: “How to Use the Oil-Immersion Objective” & “How to Measure Size of Microscopic Objects.”
Exercise 1B – STEREOSCOPIC DISSECTING MICROSCOPE
base
in-base illuminator
stage
zoom objective
substage mirror control
reflected vs. transmitted light
reflected light mirror
ocular
focus control knob
transformer
Exercise 1C – ELECTRON MICROSCOPE
Be able to distinguish between micrographs taken through a transmission electron microscope and a
scanning electron microscope. How does an electron microscope relate (in terms of magnification) to the
other two types of microscopes you have used today?
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EXERCISE 2 – CELL STRUCTURE AND DIVISION
Exercise 2A – THE CELL—UNIT OF PROTOPLASMIC ORGANIZATION
Squamous Epithelial Cell
plasma membrane (or cell membrane)
cytoplasm
nucleus
Organelles
Electron Micrograph
endoplasmic reticulum
ribosomes
mitochondria (look for the cristae)
Golgi complex
nucleus
nucleolus
Egg Cell of Sea Star
plasma membrane
cytoplasm
nuclear envelope
nucleus
nucleolus
Cell Model
cytoplasmic organelles (cont.)
nucleus
endoplasmic reticulum (ER)
nuclear membrane
rough ER
chromatin
smooth ER
nucleolus
ribosomes
cytoplasmic organelles centrioles
mitochondria
cytosol
Golgi complex
cell membrane
Exercise 2B – CELL DIVISION—MITOSIS AND CYTOKINESIS
Know the cell cycle:
interphase
mitosis (PMAT)
-prophase
aster
spindle fibers
centromere
chromosome
-metaphase
metaphase plate
-anaphase
daughter chromosome
-telophase
cytokinesis
cleavage furrow
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EXERCISE 3 – EMBRYOLOGY
Exercise 3B – CLEAVAGE PATTERNS—SPIRAL AND RADIAL CLEAVAGE [BEGINS ON PAGE 37]
Spiral Cleavage: Early Embryology of the Ribbon Worm, Cerebratulus
Protostomia (protostomes are animals in which the embryonic blastopore forms the mouth)
Cerebratulus (a ribbon worm)
distinguish between unfertilized ovum vs. fertilized, undivided ovum (=zygote)
morula stage
gastrula stage
blastula stage
-archenteron
-blastocoel
-blastopore
In “Early embryology of Cerebratulus, a nemeterean worm,” (Fig. 3-8), omit figure J.
Radial Cleavage: Early Embryology of the Sea Star, Asterias
Deuterostomia (deuterostomes are animals in which a secondary embryonic opening forms the mouth.)
Asterias (the sea star) – on photos “Embryology of a sea star,” (Fig. 3-9), figures A-I only; omit J-L.
distinguish between unfertilized ovum vs. fertilized, undivided ovum (figures A and B)
morula stage
gastrula stage
blastula stage
-archenteron
-blastocoel
-blastopore
-blastocoel
Exercise 3C – FROG DEVELOPMENT
fertilized egg (zygote)
gastrula stage
vegetal pole/hemisphere
-blastopore
animal pole/hemisphere
-yolk plug
morula stage
-germ layers:
blastula stage
endoderm1
-blastocoel
ectoderm2
mesoderm3
-archenteron4
-
blastocoel
-neural plate
-notochord
“Early embryology of a frog to a tadpole stage”, (Fig. 3-10), figures A-H only; omit I-L.
1
All yellow on models represents endoderm.
2
All pink/orange to reddish color on models represents mesoderm.
3
Ectoderm is the dark brown to black layer on the outer surface of the models.
4
Space (or cavity) represented by the blue color on models is the archenteron.
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EXERCISE 4 – TISSUE STRUCTURE AND FUNCTION
*Read the introductory paragraphs. Know the terms in bold print.
General Description of Basic Tissue Types
Epithelial Tissue (simple):
simple squamous epithelium
simple cuboidal epithelium
simple columnar epithelium
pseudostratified epithelium
Epithelial Tissue (stratified):
stratified squamous epithelium, keratinized
stratified squamous epithelium, nonkeratinized
Connective Tissue:
areolar connective tissue
adipose connective tissue
hyaline cartilage (contains lacunae)
bone
-osteocyte
-osteon
-osteon canal
-lamellae
-lacuna
-canaliculi
blood -- (erythrocytes, leukocytes, platelets)
Muscle Tissue:
smooth muscle
skeletal muscle
-striations
cardiac muscle
-striations
-intercalated disk
Nervous Tissue:
neuron
*Note: There are only four basic types of tissue—epithelial, connective, muscle, and nervous. All types
within each of the four categories will be referred to as specific tissue types.
Exercise 4A – TISSUES COMBINED INTO ORGANS
Cross-section through the Trachea (pg. 63)
hyaline cartilage
pseudostratified epithelium
loose connective tissue
smooth muscle
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SOME IMPORTANT CONCEPTS IN ZOOLOGY
The purpose of this exercise is to demonstrate the concepts of homology and primitive vs.
derived characters and the use of these concepts in the classification of organisms. These ideas provide
an important framework for the study of relationships among organisms in that they demonstrate first,
the similarity of structure among closely related organisms and second, the modifications of basic
structural plans that distinguish specific organisms. Such studies of relationships among organisms are
known as the subdiscipline in biology called systematics. In addition, you will examine the similarities and
differences among serially homologous structures; that is, structures that are repeated within an
individual organism.
Today's exercise uses mammalian structures to illustrate these principles.
HOMOLOGY AND CONVERGENCE
Homology is defined as equivalence of structure that results from inheritance from a common
ancestor. That is, structures in different organisms are homologous if each has been derived (in
evolutionary time) from the same structure in the common ancestor of those organisms.
Consider structure S in organism A. Suppose that two subpopulations of A become geographically
isolated from one another for a long period of evolutionary time and are subjected to different selection
pressures, mutation rates and/or genetic drift in isolation. Individuals of the descendent populations A'
and A" may now possess the modified structures S' and S", respectively. These structures (S' and S")
are homologous, no matter how similar or different they appear because they were both derived from the
ancestral structure, S.
S'A'
SA
=Homologous Structures
S"A"
Similarity due to convergence occurs when the organisms B' and C' having similar structures S'
and S", respectively, did not share a common ancestor with structure S that gave rise to both S' and S".
Rather, structures of different origin, say Q (in B) and R (in C), became modified, presumably under
similar selection pressures, to resemble one another in their respective descendents, B' and C'.
QB
S'B'
RC
S"C'
=Convergent Structures
The problem arises: How do we distinguish homologous from convergent structures? We certainly
have very little chance of discovering the common ancestor of divergent organisms, and even if we did,
the processes that led to modification of structure took place over long periods of time and would be
impossible to follow through all descendent populations. We therefore must look for some other types of
evidence to distinguish homologous similarity from convergent similarity. One approach is to examine the
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structures in question in detail. Because homologous structures were (by definition) from the same
ancestral structure and because the processes of replication of structure from generation to generation
via DNA replication are basically conservative, then homologous structures should resemble one another in
many details, such as shape, composition, relationships to other structures, and developmental processes.
Convergent structures, on the other hand, may resemble one another in ways that only reflect functional
similarity.
The problem of distinguishing homologous from convergent structures can be quite complex,
however. On the one hand, convergence can lead to remarkable similarities among distantly related
organisms. Perhaps the most striking examples of convergence in the mammals are those between some
of the marsupials and the placentals that exploit similar ecological habitats on different continents. Note
the overall resemblance in the following placental/marsupial pairs:
Placentals
Marsupials
Large
Predators
Gliders
Large
Rodent
Habits
Small
Rodent
Habits
Despite the superficial resemblances, the differences in internal structure and reproductive
biology between marsupials and placentals suggest very early divergence between these two subgroups
and consequently, very distant relationships between members of these pairs.
Conversely, homologous structures may appear quite dissimilar at first glance due to major
modifications of the ancestral structure in one or all lines of descendent. As a further complication,
modifications may even be associated with functional changes. For example, the wing of a bat and the
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human hand are homologous structures because both were derived from the manus (hand or forefoot) of a
primitive mammalian ancestor. The ancestral structure probably resembled the following diagram:
Dorsal View: Right Manus
Careful inspection of the bat wing and the human hand will reveal the same arrangement of bones,
although the relative sizes of bones are different. Examine skeletons of the bat wing, human hand, and
forefoot of a cat. Identify the homologous bones among these structures (you do need to know the
names of these bones). Note the modifications that have evolved in these different organisms. How are
these modifications related to changes in function? (A diagram of the vertebrate forelimb is at the end
of this section)
Now consider another type of wing: that of a bird. Note the arrangement of bones that
contribute to the wing skeleton. Is it the same as that supporting the bat wing? In birds the number
forelimb digits have been reduced and the carpals and metacarpals are fused as the carpometacarpus.
Wings of birds and bats are convergent structures. Each type of wing was derived independently;
that is, birds and bats never shared a winged ancestor. If we examine these structures at another level
however, we find that they are homologous. Wings of birds and bats, although not homologous as wings,
are homologous as forelimbs. Birds and bats did share a common ancestor (one that we would probably
classify as a reptile) that had an arrangement of bones in the forelimb that was probably very similar to
that illustrated above for our primitive mammalian ancestor.
CLASSIFICATION
The goal of evolutionary classification is to construct groupings of organisms which reflect the
phylogenetic relationships among them. For example, in the Linnaean hierarchy of classification (kingdom,
phylum, class, order, family, genus, species), if two species are placed in the same genus, those two
species are presumed to be more closely related to one another than either is to a third species placed in
another genus. That is, those two congeneric species shared a more common ancestor with one another
than either did with the third species. The following diagram illustrates the relationships among six taxa,
A-F. (A taxon is any grouping of organisms in the hierarchical classification.) In this diagram we see that
taxa B and C are more closely related to one another than either is to A or D, as indicated by their
sharing a common ancestor (which shall remain nameless) at node I. Now consider taxon A. Taxon A is
more closely related to the lineage containing taxa B and C than it is to taxon D, by virtue of the common
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ancestor which A and (B+C) share at node II. Taxon A is said to be the sister group of (B+C). (And, for
that matter, at another level, B is the sister group of C.) Now consider taxon D. What is D's sister
group? That is, with which taxon or taxa did it share the most recent common ancestor?
A
B
C
D
E
F
I
II
III
In theory, evolutionary classification is very straightforward, but in practice, the determination
of phylogenetic relationships is not always easy. The characteristics one should use to construct an
evolutionary classification are those which reflect the common ancestry of the organisms in question.
Certainly this means that the characters for study should be homologous (by now you should have an
appreciation for the potential difficulties in determining those homologies). Additionally, the
characteristics chosen should reflect modifications of ancestral structure that are unique to lineages of
organisms. The criterion for evolutionary classification, then, is the use of shared, derived (specialized)
characteristics rather than primitive characteristics.
Consider the genealogy illustrated on the next page. Although it is contrived, it demonstrates
some important concepts in evolutionary classification.
In this example, characteristics are listed for each of the taxa, A-F. 1, 2, 3, and 4 are the
ancestral or primitive states of the characters in question. 1', 1", 2', 3', 3", and 4' represent derived
character states.
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A
B
C
D
(1', 2, 3', 4)
(1', 2', 3', 4)
(1', 2', 3', 4')
(1, 2, 3', 4)
E
(1, 2, 3", 4)
F
(1", 2, 3", 4)
Which characteristics distinguish the following groups from one another?
B from C _________________________________________________
A from (B+C) ______________________________________________
(A+B+C) from D ____________________________________________
E from F _________________________________________________
(E+F) from (A+B+C) _________________________________________
Note that characteristic 4 is shared by most taxa in this diagram. Also notice that it carries
almost no information as to the relationships among organisms except to distinguish B from C. Remember,
4 is a primitive characteristic; one that has not been modified in most lineages but has been inherited,
unaltered, from the common ancestor shared by all the taxa in this example. Also note that each taxon
has a unique mixture of primitive features retained from its ancestors and new, evolved or derived traits.
In the example above you were given information on the relationships of the taxa in question. In
most instances, however, the true genealogy of a group of organisms is not known, and we infer
relationships based on shared, derived characteristics. It becomes important to distinguish primitive
from derived characteristics. This task is complicated by the fact that the ancestor of a lineage is very
unlikely to be available for examination. What other characteristics might be used to decide if a
characteristic is likely to be primitive? (By the way, this question has occupied many evolutionary
biologists for a long time, and continues to do so.)
Now, try your hand at discovering characteristics that serve to define groups. On one of the
tables, you will find a variety of mammal skulls. Your task is to examine these skulls and decide which
characteristics serve to define groups (such as rabbits, rodents, carnivores, etc.) and distinguish them
from other groups. Compare notes with the other students in the class. We will compile a list of
distinguishing characteristics on the board.
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SERIAL HOMOLOGY
The homology between structures in different organisms that we have just been discussing is
phylogenetic homology: similarity due to common ancestry. In addition, there can be similarity among
repetitive structures within the same organism due to common embryonic origin. Such similarity is called
serial homology. For example, individual vertebrae along the human vertebral column are serially
homologous.
Use the figure below to find the basic regions of a lumbar vertebra. Then examine the vertebrae
along the length of the vertebral column and determine the serial homology (noting both similarities and
differences) of the following parts:
spinous process
transverse process
(rib, in the thoracic region)
inferior articular process
superior articular process
body
Examine the vertebral column on the human skeleton. It is divided into five regions, as follows:
Cervical--vertebrae 1-7
Thoracic--vertebrae 8-19
Lumbar--vertebrae 20-24
Sacral--vertebrae 25-29 (fused)
Coccygeal--vertebrae 30-34 (fused and variable in number in humans); vertebrae in the tail of
other vertebrates are called Caudal vertebrae
Now, examine the vertebral columns on some other mammal skeletons in the lab and compare them
to the disarticulated vertebrae and ribs from a giraffe. Arrange the giraffe vertebrae in order along the
length of the table and notice the differences (some subtle, some quite obvious) between adjoining
vertebrae.
The more obvious structural differences between vertebrae of each group are characteristics
useful in distinguishing regions. For example, note the number of foramina (=passages) in the cervical
vertebrae.
Despite these variations, serial homologies can be established along the vertebral column.
Embryologically, each vertebra is formed by a series of components that are essentially identical from
one vertebra to the next in early development. The differences among vertebrae are due to variations in
the relative growth and fusion of these elements. These elements include precursors to the spinous
process, the body, and the transverse processes (which become ribs in the thoracic region of the
column).
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Generalized Vertebra (amniote)
Generalized Vertebrate Forelimb
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EXERCISE 6 – PROTOZOAN GROUPS
Read the introductory paragraphs. For the classification, you are required to know only the taxa as listed
below (**note: there are taxa in the lab manual that you are not required to identify). Note also that you
must be able to (correctly) identify, name, and classify the genera (in italics) and informally named groups
as given in the following list.
Kingdom Protista (the protozoa)
“amebas” – (relationship unresolved) Amoeba, Difflugia, radiolarians, foraminiferans
Phylum Euglenozoa – Euglena, Trypanosoma, Trichonympha
Phylum Chlorophyta - Volvox
Phylum Apicomplexa – Plasmodium
Phylum Ciliophora – Paramecium, Stentor, Vorticella
As a beginning to this lab, you will receive a lab talk on scientific names and nomenclature. Students are
expected to be able to use nomenclature correctly from this point on. Review the information on p. 67.
Exercise 6A —AMOEBA AND OTHERS
Read carefully the introductory paragraph on “Where Found”.
Study of Live Specimens—Examine living material of Pelomyxa (a naked ameba) and Difflugia (an ameba
with a test, or shell).
General Features—For exam purposes, identify all genera examined (Amoeba, Pelomyxa, Chaos) as
Amoeba.
plasmalemma
food vacuole
ectoplasm
contractile vacuole
endoplasm
nucleus
pseudopodium
Other Sarcodines—Be able to identify on prepared slides. Know what a “test” is.
Difflugia
foraminiferans
radiolarians
Exercise 6B – PHYLUM EUGLENOZOA—EUGLENA, TRYPANOSOMA, TRICHONYMPHA; PHYLUM CHLOROPHYTAVOLVOX;
Read carefully the introductory paragraphs.
Euglena
Read “Where Found”.
Study of Live Specimens – Examine living material of Euglena.
Stained Slide of Euglena
flagellum (there may be a specially labeled slide)
chloroplasts
pellicle
contractile vacuole
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Trypanosoma
Read the introductory paragraphs. The trypanosomes in this lab will be found on a demonstration slide in
which an oil immersion objective is used to magnify the blood sample sufficiently for you to identify the
organism. The trypanosome shown is the cause of African Sleeping Sickness. The only feature you are to
identify is the undulating membrane.
Demonstration Flagellates
On demonstration scopes are specimens of the following:
Trichonympha (from termite gut; “Termite Flagellates”)
PHYLUM CHLOROPHYTA-VOLVOX
Volvox
Read “Where Found”.
If available, examine living colonies of Volvox.
General Features
zooids
flagella
daughter colonies
Exercise 6C – PHYLUM APICOMPLEXA—PLASMODIUM
Read the introductory paragraphs. Examine the life cycle diagram in the lab manual. You are to examine a
prepared slide of a blood sample infected with Plasmodium, the cause of the disease Malaria. The life
stage of the organism seen in this slide should be the trophozoite stage (often called the signet-ring for
its shape). Know trophozoite.
Exercise 6D – PHYLUM CILIOPHORA—PARAMECIUM AND OTHER CILIATES
Read “Where Found”.
Study of Live Specimens – Examine living Paramecium.
General Structure and Function
oral groove
cytopharynx
cilia
pellicle
food vacuole
contractile vacuole
macronucleus
micronucleus
binary fission
conjugation
Other Ciliates
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Vorticella: be able to identify: stalk, body, cilia, and nucleus
Stentor: be able to identify: macronucleus and cilia
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EXERCISE 7 – THE SPONGES
Read the introductory paragraphs. You are required to know only the taxa given on this handout. (Note:
there are taxa given in the lab manual that you are not required to identify.) Genus names are in italics.
Those names not in italics are common names which you also are required to know. You must be able to
place each organism examined within the correct classification scheme—i.e. kingdom, phylum, class (if
given), genus, and common name. You also must know the general characteristics of each group (as given in
the lab manual).
Kingdom Animalia
Phylum Porifera – Grantia (=Sycon), glass sponge
Exercise 7A – GRANTIA
We will be using Grantia for this exercise. (Grantia is the same as Sycon, a syconoid sponge.) Read
“Where Found” to become familiar with the typical habitat of these organisms. You may omit “Cellular
Structure”, “Reproduction”, and “Skeleton”. Omit “Asconoid Type of Canal System” and “Projects and
Demonstrations”.
Gross Structure
Syconoid
External Structure
osculum
spicules
spongocoel
dermal ostia
Prepared Slide
spongocoel
radial canals
incurrent canals
Examine a prepared slide of Commercial Sponge
spongin fiber
*Note: spicules may be a characteristic used in the classification of sponges.
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EXERCISE 8 – THE RADIATE ANIMALS
Read the introductory section. Be able to distinguish between a polyp and a medusa on sight.
Classification (as you are to know it) is directly below. Under “Classification” in the lab manual, you need
to be familiar with the general characters of each of the three classes—Hydrozoa, Scyphozoa, and
Anthozoa. Know the meaning of the terms monoecious and dioecious.
Kingdom Animalia
Phylum Cnidaria
Class Hydrozoa – Hydra, Obelia, Gonionemus, Physalia
Class Scyphozoa – Aurelia
Class Anthozoa – Metridium, corals
Exercise 8A – CLASS HYDROZOA—HYDRA, OBELIA, AND GONIONEMUS
Read the introductory paragraph and the section entitled “Where Found”. You may omit the section on
“Feeding and Digestion” except for the last paragraph.
Hydra , a solitary hydroid
Live specimens are for observation only. Find and identify all the following structures on the
prepared slides.
basal disc
epidermis
hypostome
gastrodermis
mouth
buds/budding
tentacles
gonads
gastrovascular cavity
cnidocytes
nematocysts
Obelia, a colonial hydroid
Find and identify all the following structures on the prepared slides.
hydranth
cnidocytes
perisarc
gonangium
coenosarc
blastostyle
hydrotheca
medusa buds/medusa
hypostome
gonotheca
mouth
gonopore
tentacles
Gonionemus, a hydromedusa
exumbrella
subumbrella
tentacles
cnidocytes
adhesive pad
velum
manubrium
mouth
gastrovascular cavity
radial canals
ring canal
gonads
epidermis
gastrodermis
mesoglea
Physalia (Portuguese man-of-war): understand “polymorphism”; know the “pneumatophore”
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Exercise 8B – CLASS SCYPHOZOA—AURELIA, A”TRUE” JELLYFISH
Read the third paragraph under “Where Found”.
General Structure
rhopalium
tentacles
oral arms
mouth
gastric pouches
gonads
nematocysts
ring canal
Developmental Stages
planula larva
scyphistoma
strobila
ephyra
Exercise 8C – CLASS ANTHOZOA—METRIDIUM, A SEA ANEMONE, AND ASTRANGIA, A STONY CORAL
External Structure
body
oral disc
tentacles
mouth
column
basal disc
siphonoglyph
peristome
epidermis
Internal Structure
pharynx
gastrovascular cavity
radial chambers
primary septa
septal perforations
incomplete septa
acontia
gonads
Corals
Read carefully the introduction under “Astrangia, a stony coral”.
Examine various hard coral skeletons on display in the lab.
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EXERCISE 9 – THE FLATWORMS
Read carefully the introductory paragraphs. Be prepared to explain how acoelomates are advanced over
the radiate animals. Under “Classification” in the lab manual, omit “Class Monogenea”, but know the
general characters of the three remaining classes.
Kingdom Animalia
Phylum Platyhelminthes
Class Trematoda – Clonorchis (liver fluke), Schistosoma (blood fluke)
Class Cestoda – Taenia (tapeworm)
Class Turbellaria – Dugesia (planarian)
Exercise 9A – CLASS TURBELLARIA—THE PLANARIANS
Read “Where Found”. Observe live planarians. Omit the regeneration experiment.
Dugesia
Prepared Slide
(whole mount and cross section)
auricle
gastrovascular cavity
pharynx
eyespot
epidermis
dorsoventral muscle fibers
parenchyma
Model
ovary
ovovitelline duct
testis
vas deferens
sperm duct
penis bulb
common genital antrum
seminal receptacle
excretory canals
protonephridium
nerve cord
cerebral ganglion
eyespot
Exercise 9B – CLASS TREMATODA—THE DIGENETIC FLUKES
Read “Where Found”. Read about Schistosoma, the human blood fluke. Omit “Observations of the Living
Flukes”.
Clonorchis (prepared slide, whole mount)
oral sucker
ventral sucker
mouth
pharynx
intestine
excretory pore
bladder
testes
genital pore
seminal receptacle
ovary
yolk glands
uterus
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Exercise 9C – CLASS CESTODA—THE TAPEWORMS
Read carefully the introductory section.
Taenia
(model)
scolex
suckers
neck
rostellum
proglottid
genital pore
excretory canal
testes
vagina
ovaries
uterus
eggs
yolk gland (or vitelline gland)
vas deferens
nerve cord
(prepared slide)
scolex
suckers
rostellum
neck
proglottid
genital pore
testes
vagina
ovaries
uterus
vas deferens
nerve cord
eggs
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EXERCISE 10 – FIVE SMALL PROTOSTOME PHYLA (PSEUDOCOELOMATES)
Read the introductory section. Understand the differences between acoelomate, pseudocoelomate, and
eucoelomate animals.
Kingdom Animalia
Phylum Nematoda - Ascaris, vinegar eel, hook worm, Trichinella
Phylum Rotifera - rotifers
Phylum Nematomorpha - horsehair worms
Exercise 10A - ASCARIS, THE INTESTINAL ROUNDWORM.
Read carefully the introductory paragraph concerning nematodes. Know the general characteristics of
the group. Read "Where Found".
Preserved specimen
spicules
mouth
lips
anus
cuticle
lateral lines
pseudocoel
intestine
vagina
uteri
oviducts
ovaries
testis
vas deferens
seminal vesicle
Prepared slide, x-section
cuticle
epidermis
pseudocoel
uterus
oviducts
ovaries
intestine
testes
seminal vesicle
vas deferens
***TAKE CARE TO WASH YOUR HANDS THOROUGHLY AFTER HANDLING THE PRESERVED ASCARIS. IT IS
POSSIBLE FOR THE EGGS TO REMAIN VIABLE EVEN AFTER SEVERAL YEARS OF BEING SUBMERGED IN
PRESERVATIVES.
Other Nematodes: The following are to be seen on prepared slides. Identify and classify.
vinegar eels (free-living)
hook worms (parasitic)
Trichinella (parasitic)
Exercise 10B - OTHER PSEUDOCOELOMATE
Phylum Rotifera (=rotifers)
corona
foot
Phylum Nematomorpha (horsehair worm)
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EXERCISE 11 - THE MOLLUSCS
Read the introductory paragraphs. Under "Classification" in the lab manual, know the general
characteristics of each group included in the classification section below. Note: omit the classes
Monoplacophora, Caudofoveata, and Solenogastres.
Kingdom Animalia
Phylum Mollusca
Class Scaphopoda - tusk shell
Class Bivalvia - freshwater clam, Glochidia
Class Gastropoda - land snail, freshwater snail, slug
Class Polyplacophora - chiton
Class Cephalopoda - squid, octopus, Nautilus, ammonite
Exercise 11A - CLASS BIVALVIA—THE FRESHWATER CLAM.
Read "Where Found".
External structure (The Shell)
valves (left and right)
hinge ligament
umbo/umbones
lines of growth
adductor muscle scar
foot retractor muscle scar
foot protractor scar
pallial line
pseudocardinal teeth
lateral teeth
nacreous layer
Internal structures
incurrent aperature (or siphon)
excurrent aperature (or siphon)
gills
mantle cavity
visceral mass
foot
labial palps
mouth
gill lamellae
suprabranchial chamber
heart
intestine
coelomic cavity
open system of circulation
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Slides
Glochidia
Model
hinge ligament
umbo/umbones
adductor muscle scar
foot retractor muscle scar
foot
labial palps
heart
intestine
digestive gland
coelomic cavity
stomach
anus
kidney
incurrent aperature (or siphon)
excurrent aperature (or siphon)
gills
mantle cavity
Exercise 11B - CLASS GASTROPODA—THE PULMONATE LAND SNAIL
Read "Where Found".
foot
head
tentacles
eyes
radula (prepared slide)
Exercise 11C - CLASS POLYPLACOPHORA—THE CHITON.
Read "Where Found".
head
foot
mantle
mantle cavity
gill
Exercise 11D - CLASS CEPHALOPODA—THE SQUID.
Read "Where Found" and "Behavior". Note: examine the fossil ammonite on the side table.
head
arms
lateral fins
mantle
collar
eyes
tentacles
mouth
jaws
funnel (=siphon)
mantle cavity
pallial cartilages
23
funnel retractor muscles
anus
ink sac
gills
branchial heart
systemic heart
kidney
radula
liver
stomach
stellate ganglia
pen
rectum
24
EXERCISE 12 – THE ANNELIDS
Read the introductory paragraphs. Be sure to understand the concepts of segmentation and metamerism.
Also understand the method of locomotion utilized by the annelids.
Kingdom Animalia
Phylum Annelida
Class Polychaeta - clamworm
Class Oligochaeta – Lumbricus (earthworm)
Class Hirudinida – Hirudo (medicinal leech)
Exercise 12A – CLASS POLYCHAETA—THE CLAMWORM
Read “Where Found” and “Behavior” (see living specimens if available.)
External Features
head
prostomium
metamere
peristomial tentacles
parapodia
pharynx
anus
mouth
cirri
jaws
Exercise 12B – CLASS OLIGOCHAETA—THE EARTHWORMS
Read “Where Found” and “Behavior”.
External Structure
Internal Structure (Earthworm)
peristomium
pharynx
mouth
esophagus
prostomium
crop
metamere
gizzard
anus
intestine
clitellum
calciferous glands
setae
chloragogue cells
male pores
typhlosole
seminal grooves
dorsal vessel
females pores
dorsal pore
notopodium
neuropodium
setae
ventral cirrus
dorsal cirrus
aortic arches
seminal vesicles
seminal receptacles
nephridia
cerebral ganglion
ventral nerve cord
Pay particular attention to the paragraph on “Earthworm Copulation”.
Histology of Cross Section (see Fig. 12-5)
cuticle
epidermis
circular muscle layer
longitudinal muscle layer
parietal peritoneum
visceral peritoneum
chloragogue tissue
lumen of intestine
typhlosole
ventral nerve cord
dorsal vessel
Exercise 12C – CLASS HIRUDINIDA—THE LEECH
Read “Where Found” and “Behavior” (although there are no live specimens for observation.)
External Features
annuli
anus
oral sucker
male genital pore
mouth
female pore
caudal sucker
25
EXERCISE 13 – THE CHELICERATE ARTHROPODS
Read the introductory paragraphs.
Kingdom Animalia
Phylum Arthropoda
Subphylum Trilobita
Subphylum Chelicerata
Class Merostomata – Limulus (horseshoe crab)
Class Arachnida – spiders, scorpions, ticks, mites,
Exercise 13A: THE CHELICERATE ARTHROPODS—HORSESHOE CRAB & GARDEN SPIDER
HORSESHOE CRAB
Read “Where Found”. (See live specimen if available.) This and all other members of the Arthropoda
periodically shed their exoskeleton in a process called ecdysis
External Features
exoskeleton
cephalothorax (=prosoma)
carapace
compound eyes
simple eyes
mouth
chelicerae
pedipalps
walking legs
chelae
gnathobases
chilaria
abdomen
genital operculum
genital pores
gills/book gills
lamellae
telson
anus
Pay particular attention to the section on “Reproduction”.
Class Arachnida: Note the diversity demonstration of arachnids on the side table (ticks, mites, scorpion,
and daddy-long-legs).
GARDEN SPIDER
Read “Where Found” and “Behavior” (although we have no living specimens to observe.)
External Features (refer to Fig. 13-4)
exoskeleton
lung slit
epigynum
spinnerets
anus
fang
abdomen
cephalothorax
pedicel
walking legs
chelicerae
26
EXERCISE 14– THE CRUSTACEAN ARTHROPODS
Kingdom Animalia
Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca – Cambarus (crayfish), lobster, crab, isopods
Class Branchiopoda – Daphnia
Class Maxillopoda – ostracods, copepods, barnacles
Exercise 14A – SUBPHYLUM CRUSTACEA – THE CRAYFISH & OTHER CRUSTACEANS
Read the introductory paragraphs. Pay particular attention to the bold terms: mandibles, antennae (two
pairs), maxillae (two pairs), gill-breathing arthropods, and biramous. Read “Where Found” and note that
the lobster is a marine form whereas the crayfish is found in freshwater.
External Features
exoskeleton
cephalothorax
carapace
branchiostegites
gill chamber
gills
rostrum
compound eye
antennae
maxillipeds
abdomen
swimmerets
telson
anus
uropods
seminal receptacle
Dissection of the Appendages
serial homology
uropods
swimmerets
copulatory organs
walking legs
chelipeds
chelae
biramous
uniramous
oviduct opening
maxillipeds
maxillae
mandibles
antennae
renal opening
antennules
gills
Internal Structure
heart
hepatopancreas/liver
gastric muscles
mandibular muscles
extensor muscles
flexor muscles
ostia
gonads
stomach
-cardiac chamber
-pyloric chamber
intestine
esophagus
gastric mill
antennal (or green) glands
supraesophageal ganglia
Other Crustaceans – Be able to Identify and Classify from Prepared Slides
CLASS BRANCHIOPODA
Daphnia
CLASS MAXILLOPODA
ostracods
copepods
barnacles
27
EXERCISE 15 – THE ARTHROPODS: MYRIAPODS AND INSECTS
Read the introductory paragraph. Be able to distinguish uniramous and biramous.
Kingdom Animalia
Phylum Arthropoda
Subphylum Myriapoda
Class Chilopoda – centipedes
Class Diplopoda – millipedes
Subphylum Hexapoda
Class Insecta – Romalea
Exercise 15A – THE MYRIAPODS – CENTIPEDES AND MILLIPEDES
Read the introductory paragraph.
CLASS CHILOPODA – THE CENTIPEDES
ocelli
second maxillae
antennae
maxillipeds
labrum
poison fangs
mandibles
anus
first maxillae
spiracles
CLASS DIPLOPODA – THE MILLIPEDES
ocelli
antennae
labrum
mandibles
labium
spiracles
EXERCISE 15B – THE INSECTS
Read the introductory paragraphs. The study of insects is entomology. Note the group’s chief
characteristics: walking legs (three pairs), antennae (one pair), head, thorax, abdomen, tracheal tubes,
and wings. The dissection is described on the following pages.
Class Insecta – Romalea
External Structure
exoskeleton
compound eyes
antennae
ocelli
labrum
mandibles
labium
maxillae
prothorax
mesothorax
metathorax
spiracles
wings
femur
tibia
tarsus
claws
tympanum
ovipositor
Internal Structre (on handout)
hemocoel
ovarian tubules
rectum
hindgut
Malpighian tubules
gastric caeca
esophagus
crop
proventriculus
trachea
ventral nerve cord
subesophageal ganglion
28
ROMALEA
The internal anatomy of grasshoppers is often poorly preserved because the exoskeleton prevents
penetration of preservative. However, it is often possible to see the major features. Unlike crayfish, an
insect’s viscera are distributed throughout the body.
Cut off the wings and legs. To open the grasshopper, insert a pair of fine scissors under the lateral
pleural membrane of the ninth abdominal segment above the spiracle and cut forward to the thorax. Keep
the tips of the scissors up against the inside of the exoskeleton, or you may destroy internal organs that
lie close to the dorsal surface. Repeat the cut on the other side. Now extend the cuts forward through
the exoskeleton of the thorax to just behind the head. Make a third cut to one side of the dorsal midline
of the thorax, then carefully lift the exoskeleton and gently tease away any adhering tissue. Cut the
large flight muscles that attach near the bases of the wings. Trim off large pieces of the cuticle as they
are freed. Once the animal is opened, pin it down securely in the tray, and flood the tray with water to
float the internal organs.
The organs of an insect sit in a large cavity, the hemocoel. It is not a true coelom because there are no
mesenteries and it is not lined with peritoneum. If your animal was well-fed prior to preservation, large
yellowish fat bodies may fill the cavity. If it was collected during the breeding season, the gonads will be
large.
Reproductive System. The gonads are located in the abdomen beneath the heart. Gently probe the
gonadal tissue to separate the organs. The paired ovaries of females are composed of many ovarian
tubules that connect to oviducts passing posteriorly to the vagina. Dorsal to the vagina is a small
diverticulum of the reproductive tract, the seminal receptacle, where sperm are stored following
copulation. As each egg passes through the oviduct, a few sperm are released to fertilize the egg as it is
laid. In the fall, grasshoppers deposit their eggs in the soil. In the spring, nymphs that look similar to
adults hatch and begin to feed. They molt five times before reaching adult size.
In males, the testes lie dorsal to the intestine. Sperm ducts from each testis pass ventrally to unite into
a single ejaculatory duct, which passes into a terminal copulatory organ.
Digestive and Excretory Systems. Once the gonads have been teased aside, you should see the hindgut
of the digestive system in the abdomen. If you extend your cut posteriorly, you should reveal where the
intestinal portion of the hindgut enlarges into the rectum. When water is scarce, the rectum reclaims
moisture from the fecal material before it is voided.
Follow the hindgut forward to an area where serveral tubules branch from the digestive tract. This
marks the junction of the midgut with the hindgut. The tubules are the Malpighian tubules of the
insect’s excretory system. Hemolymph bathes the tubules as they extend out into the hemocoel. Small
molecules in the hemolymph diffuse across the tubules. As fluids travel through the tubules toward the
gut, nutrients and ions are reabsorbed, leaving waste materials and water that pass on to the rectum and
are voided. Some insects reclaim so much fluid from the tubes and hindgut that the fecal pellets are
often as dry as dust.
The anterior junction of the midgut with the foregut is marked by several fingerlike projections, the
gastric caeca. Food passes into the caeca where it is digested and absorbed. The foregut is subdivided
into two regions. An esophagus conveys food from the pharynx into the crop, a storage area. From the
29
crop, food enters the proventriculus (gizzard), where it is ground into fine particles by hardened cuticular
plates in the wall of the proventriculus.
Gas-Exchange System. On the sides of the abdominal segments, find spiracles, openings into the gasexchange system. Connected to the inside of each spiracle is a trachea. Air enters through the spiracles
in the body wall and diffuses through the tracheae that ramify throughout the body. In the tissues, the
tracheae branch into small tracheoles that press into cells, supplying their oxygen needs and removing
carbon dioxide. In large insects, such as the grasshopper, large balloon-like air sacs are located in the
body cavity. Muscle movements compress them, promoting air flow.
Nervous System. Remove the digestive and reproductive systems by cutting through the esophagus and
stripping the posteriorly located organs. Look at the floor of the body cavity. You should see the ventral
nerve cord beneath some covering membranes. Gently tease away the tissues to expose the nerve cord.
Note the paired ganglia. Are they all the same size? If not, how would you explain the difference?
Follow the nerve cord forward to the esophageal region and find the supraesophageal ganglion above the
esophagus and the subesophageal ganglion beneath. They are connected by the circumesophageal
connectives that pass around the esophagus.
30
EXERCISE 16 – THE ECHINODERMS
Read the introductory paragraphs. Be familiar with the distinguishing characters of the phylum: dermal
endoskeleton, water-vascular system, pedicellariae, dermal branchiae, and pentaradiate symmetry.
Phylum Echinodermata
Class Crinoidea – sea lilies, feather stars
Class Asteroidea – Asterias (sea star)
Class Ophiuroidea – brittle stars
Class Echinoidea – sea urchins, sea biscuits, sand dollars
Class Holothuroidea – Cucumaria (sea cucumber)
Exercise 16A – CLASS ASTEROIDEA—THE SEA STARS
Read “Where Found” and “Behavior”. Be prepared to define/describe the following: pentaradial
symmetry, rays (or arms), oral-aboral flattening, ampullae, spines, dermal branchiae, pedicellariae, and
eyespot.
External Structure
ABORAL SURFACE
central disc
rays (bivium & trivium)
madreporite plate
anus
ORAL SURFACE
ambulacral groove
tube feet (=podia)
ambulacral spines
epidermis
spines
pedicellariae
dermal branchiae (=skin gills)
mouth
peristomial membrane
stomach
Endoskeleton
ossicles
epidermis
dermis
peritoneum
ambulacral ossicles
ampullae
ambulacral pores
ambulacral ridge
Internal Structure
coelomic cavity
pyloric stomach
pyloric duct
pyloric ceca
intestine
rectal ceca
cardiac stomach
gastric ligaments
gonads
stone canal
ring canal
radial canal
Exercise 16B – CLASS OPHIUROIDEA—THE BRITTLE STARS
Read “Where Found”. Examine the brittle star on display on the side table. Also observe the live
specimen (in the aquarium) if available.
31
Exercise 16C – CLASS ECHINOIDEA—THE SEA URCHIN
Read “Where Found”. Observe live sea urchins if available.
External Structure
spines
ambulacral regions
mouth
teeth
Aristotle’s lantern
ambulacral plates
anus
anal plate
genital plates
Exercise 16D – CLASS HOLOTHUROIDEA—THE SEA CUCUMBER
Read “Where Found”. Observe the live specimen if available.
External Structure
mouth
tentacles
anus
water-vascular system
podia
Internal Structure
coelomic cavity
pharynx
stomach
intestine
cloaca
respiratory trees
retractile muscles
longitudinal muscle bands
ring canal
ampullae
gonad
endoskeleton
Exercise 16E – CLASS CRINOIDEA—THE FEATHER STARS AND SEA LILIES
Although extant, we have only fossil crinoids on display.
32
EXERCISE 17 – PHYLUM CHORDATA: A DEUTEROSTOME GROUP
Read the introductory paragraphs. Be familiar with the distinguishing characters of the phylum:
notochord, pharyngeal gill slits, dorsal tubular nerve cord, postanal tail, endostyle or thyroid gland.
Kingdom Animalia
Phylum Chordata
Subphylum Urochordata – tunicates, sea squirts
Subphylum Cephalochordata – Branchiostoma, Amphioxus, lancelet
Exercise 17A—SUBPHYLUM UROCHORDATA (TUNICATES, SEA SQUIRTS)
Read “Where Found”.
External Features (we will not learn internal features of the adult tunicate)
Adult tunicate (whole specimen)
incurrent siphon
excurrent siphon
tunic or test
Tadpole larva (whole mount on prepared slide)
adhesive papillae
notochord
incurrent aperture
excurrent aperture
branchial basket
Exercise 17B—SUBPHYLUM CEPHALOCHORDATA (BRANCHIOSTOMA, AMPHIOXUS, LANCELET)
Read “Where Found”.
External Structure—Adult Amphioxus (=Branchiostoma) (whole mount slide)
dorsal fin
gonads
gill slits
caudal fin
myotomes
hepatic cecum
ventral fin
fin rays
endostyle
rostrum
velum
notochord
oral hood
pharynx
dorsal nerve cord
atriopore
wheel organ
photoreceptor cells
atrium
intestine
anus
gill bars
Cross-section Slide
dorsal fin
fin ray
metapleural folds
myotomes
nerve cord
notochord
pharynx
gill bars
gill slits
atrium
endostyle
hepatic cecum
intestine
33
EXERCISE 18 - THE FISHES—LAMPREYS, SHARKS, AND BONY FISHES
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata - vertebrates
Superclass Agnatha - jawless vertebrates; agnathans
Class Petromyzontida - lampreys
Class Myxini - hagfishes, slime hags
Superclass Gnathostomata
Class Chondrichthyes - Squalus
EXERCISE 18A - CLASS PETROMYZONTIDA—THE LAMPREYS
Read the introductory paragraphs.
Ammocoete Larva (whole mount slide)
myotomes
pharynx
oral hood
gill pouches
oral papillae
gill bars
gill slits
endostyle
cloacal opening
esophagus
caudal fin
intestine
dorsal fin
anus
nerve cord
liver
brain
heart
notochord
eyes
velum
Adult Lamprey - external structure
dorsal fins
pineal organ
caudal fin
eyes
buccal funnel
external gill slits
mouth
lateral line system
tongue
urogenital sinus
nostril
Adult Lamprey - internal structure, longitudinal section
dorsal aorta
mouth
notochord
horny teeth
spinal cord
pharynx
brain
respiratory tube
olfactory sac
ventral aorta
nostril
internal gill slits
tongue
liver
cranial cartilage
heart
papillae
espophagus
buccal funnel
34
Exercise 18B - The Cartilaginous Fishes—Squalus
Read "Where Found".
Squalus - external structure
head
trunk
tail
pectoral fins
pelvic fins
dorsal fins
caudal fin (heterocercal)
mouth
teeth
nostrils
eyes
rostrum
spiracles
gill slits
lateral line
cloacal opening
placoid scales
Squalus - internal structure
liver
gallbladder
bile duct
stomach
duodenum
pancreas
spleen
ileum
spiral valve
rectal gland
colon
rugae
testes
epididymis
sperm duct
kidneys
cloaca
seminal vesicles
sperm sacs
claspers
urogenital papilla
ovaries
oviduct
yolk sac (if embryos are present)
ostium tubae
atrium
ventricle
conus arteriosus
dorsal aorta
external gill slits
internal gill slits
gill chambers
gill arches
gill rakers
gill rays
primary lamellae
secondary lamellae
demibranchs
holobranch
35
DIVERSITY LAB RULES
MAMMALS
DO NOT PICK UP ANY OF THE SKULLS.
BIRDS
DO NOT PICK UP ANY BIRD SPECIMENS EXCEPT SKULLS, WHICH YOU MAY CAREFULLY
HANDLE.
HERPS (=AMPHIBIANS & REPTILES)
DO NOT SHAKE OR REMOVE SPECIMENS FROM JARS. DO NOT HANDLE THE SKULLS.
WHAT YOU NEED TO KNOW
I.
BE ABLE TO PLACE EVERY ORGANISM INTO THE CORRECT CLASSIFICATION.
II.
BE ABLE TO GIVE THE COMMON NAME OF EACH GROUP OF ORGANISMS: HAGFISH,
LAMPREY, SHARK, SKATE, RAY, RATFISH, LOBE-FINNED FISH, LUNGFISH, COELACANTH,
RAY-FINNED FISH, FROG, TOAD, SALAMANDER, CAECILIAN, LIZARD, SNAKE, TURTLE,
CROCODILIAN, RATITE BIRD, CARINATE BIRD, MONOTREME, MARSUPIAL MAMMAL,
PLACENTAL MAMMAL.
III.
KNOW THE BASIC FEATURES OF EACH SUPERCLASS AND CLASS.
IV.
IF THERE IS A PARTICULAR THEME PRESENT IN A CLASS ON DISPLAY, UNDERSTAND THE
THEME. FOR EXAMPLE, YOU MIGHT BE EXPECTED TO UNDERSTAND THE DIET OF A
PARTICULAR BAT BASED ON TOOTH CHARACTERISTICS OR TO UNDERSTAND PROBABLE
FOOD CAPTURE FUNCTION OF A PARTICULAR BIRD BASED ON BILL SHAPE.
36
OVERVIEW OF VERTEBRATE DIVERSITY
Kingdom Animalia (animals)
Phylum Chordata (chordates)
Subphylum Vertebrata (vertebrates)
Superclass Agnatha (jawless vertebrates)
Class Myxini (hagfishes)
Class Petromyzontida (lampreys)
Superclass Gnathostomata (jawed vertebrates)
Class Chondrichthyes (cartilaginous fishes)
Class Actinopterygii (ray-finned fishes)
Class Sarcopterygii: (lobe-finned fishes—includes the coelacanth and
lungfishes)
Class Amphibia (anurans, caecilians, salamanders)
Class Reptilia (snakes, lizards, turtles, crocodilians)
Class Aves (birds)
Class Mammalia (mammals)
[Two subclasses: 1) monotremes, 2) marsupials & placental mammals]
SUPERCLASS AGNATHA - jawless vertebrates. These animals do not have a lower jaw hinged to the
cranium and supported by an internal skeletal element. (Note: your lab book lumps the two agnathan
classes listed below into a single Class Agnatha.)
CLASS MYXINI - hagfish. Hagfishes are marine forms and are the only vertebrates with body
fluids isotonic to seawater. They are scavengers and feed on dead and dying fishes. They secrete
large amounts of mucus (“myxini” means “slime” in Greek) that is used as a defense against predators.
Hagfishes are also characterized by rudimentary eyes and three pairs of barbels around the mouth.
The species on display in the lab has a single opening for water to exit the body after passing through
the pharyngeal gill slits. Other species have separate openings for each individual gill slit.
CLASS PETROMYZONTIDA - lamprey. Lampreys differ from hagfishes in a number of anatomical
and physiological features. Adult lampreys have an oral disc, separate external openings for all gill
slits and a dorsal median nostril. Lampreys also undergo metamorphosis. (There may be an
ammocoetes larva on display.)
SUPERCLASS GNATHOSTOMATA - jawed vertebrates.
CLASS CHONDRICHTHYES - sharks, skates, rays and ratfishes. This class is characterized by the
following features: cartilaginous skeleton, placoid scales (and teeth that are similar in structure to
the scales), oily liver used for buoyancy, ampullae of Lorenzini which are used to detect tiny electrical
fields created by muscular movements. Examine the material that illustrates each of these
characteristics and the specimens that illustrate the diversity within the group.
Characteristics of Chondrichthyes:
Internal cartilaginous skeleton: notice that the upper jaw is not fused to the cranium.
Placoid scales: examine placoid scales under the microscope.
Teeth (similar in structure to scales): examine shark jaw
37
External anatomy of Squalus acanthias: note the following features:
ampullae of Lorenzini
spiracle
separate, lateral gill openings
heterocercal tail
Diversity of Chondrichthyes: There are over 625 species of cartilaginous fishes. You will examine
only a few representatives.
Sharks: note the laterally placed eyes and broad snout.
Skates and Rays: when you examine these specimens, note the spiracle, ventral gill slits and
enlarged pectoral fins fused to the head. (Note dorsal denticles, and on the stingray, the
enlarged “spine” [all are modified placoid scales].)
Ratfishes (also called Chimeras): examine the specimen on demonstration; note the differences
between this and the shark:
operculum
naked body (no placoid scales)
spine (a modified placoid scale)
tooth plates (inside the mouth)
NOTE: THE FOLLOWING TWO CLASSES (Actinopterygii and Sarcopterygii) HAVE
TRADITIONALLY BEEN COMBINED IN ONE CLASS—THE OSTEICHTHYES.
The recent changes in classification are in both your text and lab manual.
CLASS ACTINOPTERYGII - ray-finned fishes. Ray-finned fishes are characterized by the following
features: internal skeleton made of bone (in most), single gill opening covered with an operculum,
paired fins supported by dermal rays [they do not have fleshy lobes at the bases of the fins] , air
bladder used as a lung or for buoyancy (lost in some). The group is very diverse with over 23,000
species in both freshwater and marine environments. Examine the materials that demonstrate the
characteristics of bony fishes and examine examples of diversity. You will not be responsible for the
names of the representatives, but be able to recognize them as ray-finned fishes (Class
Actinopterygii).
Characteristics of Actinopterygii:
Bony skeleton.
Scales: Scales of ray-finned fishes all have bone in them, but some have other layers as well.
Examine the following types of scales:
ganoid scales - have ganoin, an enamel-like substance, overlying the bone. This scale is from
a gar.
cycloid scales - are composed of a thin layer of bone arranged in concentric rings (=annuli)
that reflect the growth pattern of the fish.
ctenoid scales - are like cycloid scales except that they have small tooth-like projections
(ctenii) along the exposed edge. The ctenii are thought to help improve hydrodynamic
efficiency.
Air bladder: examine the dissected specimen and note the air bladder (also called the swim
bladder). In this species the bladder is used for buoyancy.
38
CLASS SARCOPTERYGII—lobe-finned fishes. Lobe-finned fishes have some features in common with
the ray-finned fishes, including a bony skeleton and a single gill opening covered with an
operculum; however, their paired fins have a sturdy internal skeleton with muscle within the limb.
Usually have air bladder used as a lung.
Lungfishes: Examine the model of an Australian lungfish on demonstration. Note the fleshy
lobes on the paired fins. Fishes in this group have a lung (that is homologous to the air bladder
you saw earlier) and some species are able to withstand drying of the habitat by encasing
themselves in a mucus and mud cocoon and breathing air through exposed nostrils.
Coelacanth: Examine the model of the coelocanth. Note the fleshy lobes at the bases of all
the fins. This species is closely related to the lineage that is believed to have given rise to the
amphibians.
CLASS AMPHIBIA - This class includes anurans (=frogs and toads), which account for about 85% of the
diversity in the class, salamanders, and an odd “worm-like” form called a caecilian. Amphibians are
anamniotes, meaning that there is no amnion membrane to enclose the embryo and keep it from drying out.
The eggs must therefore develop in water (or a moist environment). The egg hatches into a gill-breathing
larva which, in most species, metamorphoses into a lung-breathing adult. There are species, however, that
never metamorphose but retain larval characteristics even after they mature into reproductive adults.
This is the phenomenon of neoteny.
Amphibians have smooth, moist skin with no scales, although some species have areas of thickened
epidermis (cornified areas) that resemble epidermal scales. The skull is flattened and the vertebral
column shows regional specialization for the attachment of limb girdles (this specialization is not
evident in vertebral columns of fishes).
Examine the diversity of amphibians on display and note the class characteristics shown in the
demonstrations.
CLASS REPTILIA - This class is undoubtedly paraphyletic and newer texts have proposed alternate
classifications of the reptiles, which currently include snakes and lizards, turtles, crocodilians, the New
Zealand tuatara, and the extinct dinosaurs. These organisms are quite different in many respects, but all
were placed in the Class Reptilia based on the presence of epidermal scales, an amniotic egg, direct
development (lack of larval stage) and because none has either feathers (which would make it a bird) or
hair (which would make it a mammal).
Examine the diversity of living reptiles on display. Note the similarity between snakes and lizards. There
are some legless lizards - can you distinguish them from snakes? If so, how? Of the reptilian subgroups,
snakes and lizards are more closely related to one another than either is to any other subgroup. The
turtles and the crocodilians each represent subgroups that are more distantly related to the snakes and
lizards and to each other. In fact, crocodilians are believed to be more closely related to birds than to
any other subgroup of reptiles.
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CLASS AVES - birds. The Class Aves contains approximately 9000 species extant (=living), of which
about 55% belong to one of the 27 orders - the songbirds. All members lay amniotic eggs, usually in a
nest constructed of plant material. They possess thin, dry skin covered with feathers. Feathers are
unique to this class and probably evolved for insulation; all modern birds are endothermic. All birds are
bipedal on their hindlimbs, with the forelimbs modified into wings for flight. Some members of this
class have wings that are reduced and they are flightless, but never in the history of the group has the
wing secondarily assumed some different locomotion function. Even those that use the wing under water
use it in the same way as is done for flight in the atmosphere. As a class, they show far less
morphological diversity than is found in any other tetrapod class.
Skeletal features of the class can be seen on the chicken skeleton displayed in the lab:
Skull features:
1) Toothless jaws - this feature is found in other classes also, but it only within this class that
all members lack teeth.
2) Lower jaw is composed of several bones – birds and all lower classes have jaws made up of
many bones.
3) The jaw in birds is covered with a keratinaceous sheath.
Vertebral column features: there is considerable modification in response to the demands of flight.
The column is highly rigid, with only the neck and base of the tail moveable.
4) Uncinate processes (horizontal bony flaps) overlap individual ribs, adding to rigidity of the
ribcage during downstroke in flight.
5) A large, keeled sternum attached to the ribs supports large flight muscles.
6) Pygostyle—in birds, most of the tail bone is reduced and fused.
7) Synsacrum—in birds, some lumbar, some caudal, and all the sacral vertebrae are fused.
Pectoral girdle: this structure must be stout in birds in order to withstand the stresses of flight.
8) Furcula (“wishbone”)—the clavicles in birds have become fused into a single bone.
7) Corocoid—a powerful bone that acts as a strut between the wings and sternum in birds.
Interestingly enough, monotremes also possess this structure, as do most of the reptiles.
Limbs:
10) The forelimb has been modified into the wing, which has the basic “arm” elements of all
tetrapods, but has been modified.
11) The digits have been reduced to three with only one digit remaining moveable.
12) The hindlimb has also been highly modified, with the tibia elongated and the fibula reduced
to a splint.
CLASS MAMMALIA - Mammals are characterized by two unique characteristics: the presence of hair
and the production of milk from mammary glands. Other mammalian characteristics include endothermy
and (usually) homeothermy, a variety of skin glands (oil, sweat, scent), muscular diaphragm, three middle
ear ossicles, secondary palate, ribs only on thoracic vertebrae, only a single bone in each side of the
lower jaw, and heterodont dentition.
Examine the material available illustrating several of these features and the variations in characteristics
among members of this class. Please use care in handling these specimens. Some are irreplaceable.
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There are about 4500 species of mammals divided into two subclasses:
1) The egg-laying mammals, called monotremes: There are only three living species, and they are
restricted to Australia and New Guinea. One is the duck-billed platypus, a semiaquatic form, and
the other two are spiny anteaters or echidnas. The production of eggs (ovipary), rather than
giving birth (vivipary), is a shared primitive characteristic with reptiles. Although these species
do produce milk, they lack nipples. The milk is taken from tufts of fur associated with the
mammary glands.
2) The second subclass is divided into two major groups, the marsupials and the placental mammals.
Marsupials: This group is known as the pouched mammals. Marsupials get their name from the
presence of an abdominal pouch or marsupium for carrying the young (although not all marsupials
have a pouch). The developing young are nourished with a primitive placenta much different from
other mammals. They are born at an early stage of development, crawl from the vagina to the
pouch where they attach to a nipple, and remain there for several weeks. The only species
occurring in the United States is the opossum. Most other species of marsupials (about 250)
occur in either the Australian region or South America. Look at the specimen of an adult opossum
and the preserved newborn young.
Placental Mammals: All mammals other than monotremes and marsupials have a true placenta for
nourishment of the developing embryo. This group includes the vast majority of mammals, about
3750 species.
The placental mammals occur in every habitat on Earth and include members that fly (bats) and
those that live entirely underground (e.g. pocket gophers and moles), as well as those that are
restricted to aquatic habitats (whales, dolphins, manatees). This group also includes the largest
animal ever to have lived, the great blue whale. The placental mammals are divided into about
eighteen orders. You are familiar with many of these. Examples of some of the major orders of
placental mammals are out for you to examine, including rodents, bats, carnivores, ungulates and
primates. Some of the features that distinguish these groups are explained on the cards
accompanying the specimens.
The evolution of heterodont dentition has allowed mammals to exploit almost every major feeding niche,
including insectivory, frugivory (fruit), granivory (seeds), nectivory (nectar), folivory (leaves), carnivory,
and sanguivory (blood). Although they are toothless, the baleen whales even utilize filter feeding by
means of thousands of thin strands of material called baleen.
As you examine the specimens on display, note the variations in dental morphology and their relationship
to diet.
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