Animals Lab 10: Invertebrates & Vertebrates

13 Jun Animals Lab 10: Invertebrates & Vertebrates

Question
Animals

Lab 10
Invertebrates & Vertebrates
113

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Lab 10: Invertebrates & Vertebrates

Concepts to explore:
x
x
x
x
x

CharacterisƟcs of animals
Heterotrophs
Symmetry
Invertebrates
Vertebrates

IntroducƟon
The kingdom Animalia comprises millions of species, ranging from the snail to the hippopotamus, the
ant to the elephant, the cenƟpede to the human. Though there are notable diīerences in body shape
and funcƟon, almost are moƟle, mulƟcellular eukaryotes, with disƟnct Ɵssue structures that perform
specialized funcƟons (i.e., heart, stomach) and almost all parƟcipate in sexual reproducƟon. Unlike
plants, animals cannot produce energy from sunlight and, as heterotrophs, acquire energy by consumͲ
ing organic material (other plants and animals).
Useful characterisƟc for classify animals is symmetry, or the balanced division of their form. Radial
Symmetry, as is seen in starĮsh, is a division originaƟng in the center and protruding outwards that
produces even and balanced secƟons. This is similar to the divisions that are made when a pie is cut
into many even pieces. In Bilateral Symmetry, as is seen in a beetle, the object can be divided into two
mirror images by a center line that runs through the enƟre object. Asymmetry occurs when there can
be no even division, as is seen in a sponge.
Animals are classiĮed into two categories based on structure.

x

Invertebrates are organisms that lack an endoskeleton, such as the jellyĮsh, insects, or worms.
They make up over 98% of all animal species.

x

Vertebrates possess an endoskeleton (an internal skeletal structure) and spinal column, like
you or your dog. An endoskeleton is a signiĮcant adapƟve advantage that enables vertebrates
to occupy diīerent ecological niches (roles).

There are over 35 phyla in the Animal Kingdom. The vast majority fall within the following eight, seven
of which are invertebrates.

x

Phylum Porifera consists of sponges, considered to be the oldest of the animal phyla (Figure 1).
As staƟonary Įlters, sponges play an important role in aquaƟc systems, feeding on parƟcles

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Lab 10: Invertebrates & Vertebrates
and bacteria in the water. Water enters the sponge through
several large canals and millions of small pores. Their asymmetͲ
ric body is a loose assembly of cells (no Ɵssues) that support a
skeleton of collagen Įbers and spicules. Sponges reproduce
both sexually and asexually.

Figure 1: Porifera

x

The phylum Cnidaria includes jellyĮsh,
corals, sea anemones, and hydras (Figure 2).
They were the Įrst to develop nerves and muscles and typically alternate
between two body forms: the freeͲswimming medusa and the staƟonary
polyp. Both body types consist of three layers of Ɵssue surrounded by tenͲ
tacles with sƟnging cells containing Ɵny, toxic harpoons that can be used in
either defense or oīense. They have radial symmetry (if you cut it in half,
each half will look like the other), with a hollow body cavity to digest food.
Figure 2:Cnidaria

x

The phylum Platyhelminthes includes freshwater planaria, colorful marine polycads, paraͲ
siƟc tapeworms and Ňukes. They are some of the simplest bilaterally symmetrical organͲ
isms with a deĮned head and tail, and a centralized nervous system containing a brain and
nerves. They lack both a body cavity and circulatory system, but do have a tubular mouth,
an excretory system and a highly branched digesƟve system. Clusters of lightͲsensiƟve cells
make up their eyespots. They are hermaphrodiƟc, capable of both sexual and asexual reͲ
producƟon.

x The phylum Annelida is represented by marine worms (polychaetes), earthworms and leechͲ
Figure 3: Annelida

x

es (Figure 3). They are bilaterally symmetric with a segmented body cavity
oŌen represented by a tube within a tube design. Each segment has Ɵny
hairs called setae which help the organism to move. SegmentaƟon was
an important development that provides disƟnct regions to specialize in
diīerent tasks. A oneͲway digesƟve tract, closedͲcirculatory system, and
central nervous system also diīerenƟate this invertebrate. Annelids play
a signiĮcant ecological role by reworking soil and sediments.

The phylum Arthropoda, the most diverse and numerous of
the Animal Kingdom, includes insects, crustacean, spiders, milͲ
lipedes, and cenƟpedes (Figure 4). All arthropods have segͲ
mented bodies and are covered in a hard, Ňexible exoskeleton.
Their muscles from their jointed appendages aƩach to the inͲ
side of this protecƟve cover. Many species, such as dragonŇies
that start as larvae and develop into winged adults, exhibit
Figure 4: Arthropoda

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Lab 10: Invertebrates & Vertebrates

Some sandy beaches may harbor
32,000 burrowing annelids per
square meter, which collecƟvely
may ingest and excrete 3 metric
tons of sand per year!

mulƟple life cycles. Their open body cavity which contains ƟsͲ
sues, organs and a complete digesƟve tract.

xThe phylum Mollusca includes clams, snails, slugs and the octoͲ

pus (Figure 5). Though
there is a great deal of diͲ
versity within this phylum,
all mollusks have soŌ bodies, many of which are covͲ
ered by a hard calciĮed shell. The shell is secreted by
a layer of Ɵssue called the mantle. A muscular foot
provides locomoƟon and grasping. A coarse, ĮleͲlike
organ (the radula) allows most mollusks to drill into
Figure 5: Mollusca
their prey or snag Įsh. Many hunt by propelling water
through a siphon either for locomoƟon or to capture food. A mantle cavity houses gills and
oneͲway digesƟve system.

x

The phylum Echinodermata includes sea stars, sea lilies,
sea urchins, sea cucumbers, and over 6,000 other salt waͲ
ter species (Figure 6). Instead of bilateral or radial symͲ
metry, echinoderms exhibit Įve part symmetry in their
bodies. Their hard, Ňexible bodies are composed of small
calcium plates that are oŌen spiny and covered by a thin
skin. Inside is a complete digesƟve system and a special
Figure 6: Echinodermata
ŇuidͲĮlled system that operates tube feet (which someͲ
Ɵmes grow back if lost) which allow them to move, feed, and respire.

x

Vertebrates (Figure 7), along with tunicates and lancelets, fall into a
subphylum of the phylum Chordata.

x

Tunicates are invertebrates that look like sponges but have
a bony, vertebral column with a dorsal nerve cord which
develops into a spinal cord and brain; a common feature
they share with vertebrates.

x

Their internal skeleton allows them to grow without the
need to molt (as in arthropods).
Figure 7: Vertebrates

x

Chordates have gill cleŌs (the structures located behind
the mouth and in front of the esophagus), bilateral symmetry, segmented muscles,
and a protecƟve layer (feathers, scales, hair, fur, etc.,).

x Two main groups of the subphylum vertebrata include Įshes and tetrapods (amphibians,
repƟles, birds, and mammals).

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Lab 10: Invertebrates & Vertebrates
x

Fish are found in the water, lay soŌ eggs, are cold blooded and use gills to breathe.

x

Amphibians are found in both water and on land, lay soŌ eggs, are cold blooded,
and breathe using, gills, lungs an through their skin.

x

RepƟles live almost enƟrely on land, lay somewhat hard shelled eggs, are cold
blooded and breathe through lungs.

x

Birds are found on land (and in the air), lay hard shelled eggs, are warm blooded,
and breathe through lungs.

x

Mammals are normally found on land, give live birth, are warm blooded and
breathe through lungs. Mammals are also characterized by the presence of hair on
their bodies and their ability to produce milk in sweat glands (mammary glands) for
their young. There are roughly 5,000 species of mammals.

Arguably the most dominant vertebrate is Homo sapien
(you). Humans are thought to be the longest living
mammals, though other species, such as the elephant
and whale are also longͲlived. Though there are obvious
diīerences between human beings and other mammals,
there are also many similariƟes. In the following labs we
will look at human systems as a model for what is found
in many vertebrates.

Many heart valve replacements are actually
porcine valves. The cells are removed but
the architecture of the Ɵssue remains. The
cardiac physiology between man and pig is
so similar that the parts can be made
interchangeable!

Experiment 1: Symmetry in Animals
Look at the objects listed below, which can be found in your lab kit, and decide what type of symmetry
they posses. Explain why you chose the type of symmetry you did.
1. Goggles/Safety Glasses

2. Petri dish

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Lab 10: Invertebrates & Vertebrates

3. Wash boƩle with curled straw

4. Top of a liquid boƩle

5. Balloon

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Lab 10: Invertebrates & Vertebrates
Experiment 2: CreaƟng a Phylum Key
1. The phylum characterisƟc table contains all of the main features of the eight main phyla. Your job is
to organize and idenƟfy which characterisƟcs belong to which phyla in the key. The number of lines
in the key represents the number of characterisƟcs that fall into each phylum.

Table 1: Phylum CharacterisƟc Table

1

2

3

4

5

A

Bilateral phyͲ
lum with segͲ

Most have a
calcium conͲ

Five part symͲ
metry

Specialized
cell, but no

Mantle of ƟsͲ
sue covering

B

Hollow body
cavity for food

Setae used for
movement

Jaws and skulls
part of evoluͲ
Ɵon

Complete diͲ
gesƟve tract

The Įrst to
have jointed
legs

The Įrst phyͲ
lum to Ňy

Some have
sƟnging cells

Tube feet

First muscle
and nerves

Internal skeleͲ
ton

Three Ɵssue
layers, no
body cavity
Water Ňows
through canals
of body
Body design is
a tube within a
tube

C

Parasites

D

More complex
because of
more DNA

E

All live in the
sea

Simple animals
with bilateral
symmetry

Entrance and
exit the same
in the digesͲ

All have verteͲ
bral column

Champions of
variaƟons in
appendages

F

Has the most
species

Have spines
covered with a
thin skin

Some staƟonͲ
ary polyps

Some are moͲ
bile medusa

Some propel
using their
siphon

G

Muscular foot
used to move

StaƟonary aniͲ
mal

Tubular mouth
at the midͲ
body

Humans

Hard but ŇexiͲ
ble bodies
with small

H

Spicules are
the skeleton

Radula used to
feed

No symmetry

Exoskeleton

Their burrowͲ
ing has aīectͲ
ed the global

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Lab 10: Invertebrates & Vertebrates
Table 2: Phylum Taxonomic Key

Porifera

Cnidaria

PlatyhelͲ
minthes

Annelida

Arthropoda

Mollusca

Echinodermata

Chordata

Experiment 3: Taxonomy
IdenƟfy which phylum each of the following organisms belongs in. Next to each, list the criteria
used in your determinaƟon.
1.

Figure 8

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Lab 10: Invertebrates & Vertebrates
2.
Figure 9

3.

Figure 10

4.
Figure 11

5.
Figure 12

6.

Figure 13

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Lab 10: Invertebrates & Vertebrates
The following lab exercise is intended to be an addͲon for the Invertebrate Lab. Unless your teacher
has speciĮcally requested that dissecƟon materials be included within your kit, you will NOT have the
supplies to perform the next two experiments.

Experiment 4: Invertebrate DissecƟon
The starĮsh is not a Įsh at all, rather an invertebrate that possesses no internal skeleton. Members of
the phylum Echinodermata, starĮsh are unique in that they are deuterostomes (instead of protoͲ

Materials
Preserved starĮsh
DissecƟng tray
DissecƟng tools
Magnifying lens

Note: When performing a dissecƟon, remember these important safety notes:

x
x

Dissect with the scalpel or scissor blade cuƫng away from you (and your lab partner).
If you develop an allergic reacƟon to the preserving Ňuid, contact your healthcare
provider. Also, inform your instructor and inform him/her of your situaƟon.

x

Contact your local waste management company for instrucƟons for the proper disͲ
posal of your specimen.

x

Wash your hands, dissecƟon tools, and all work surfaces with soap and water when
Įnished with the dissecƟon.

stomes like earthworms, grasshoppers, clams, etc.). Deuterostomes exhibit incomplete segmentaƟon,
and a brain and spinal cord above the gut, among of other diīerences with protostomes. StarĮsh have
no front or back, and can move in any direcƟon without turning.

Procedure
1. Examine the external anatomy of the starĮsh. The side in which the mouth is located is called
the oral surface (ventral side). The opposite side is called the aboral surface (dorsal side). See
Figure 14 for reference.

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Lab 10: Invertebrates & Vertebrates

Figure 14: The aboral (leŌ) and oral (right) surfaces of the starĮsh.

2. Run your gloved Įnger over the surface and note the texture. Use the magnifying glass to exͲ
amine the spiny skin in detail.
3. Along with the sƟī spines, you may also see small, hairͲlike gills used by the starĮsh to take in
oxygen.
4. Pedicellaria are Ɵny pincers that look like pliers that are used to grip small objects.
5. Place the starĮsh ventral side up and note the tube feet that run down the arms, or rays, of the
starĮsh. They will be located on either side of the groove that runs from the Ɵp of each ray to
the center.
6. Find the mouth in the center of the starĮsh.
7. On the oral surface of each arm are open ambulacral grooves extending from the mouth to the
Ɵp of each arm. Locate the abulacral groove running from the center down each ray.
8. Using the magnifying lens, examine the tube feet with protruding suckers on either side of the
abulacral groove.
9. Flip the starĮsh so the dorsal side is facing up.
10. Note the eyespots at the Ɵp of each arm, which allows the starĮsh to sense and respond to
light. To see the eyespots, and spread the tube feet at the Ɵp of the ray and examine it closely
with the magnifying lens.
11. The Ňat central disk is at the center, and Ɵny, hollow, ĮngerͲlike gills cover the body of the starͲ
Įsh.
12. The opening of the waterͲvascular system is called the madreporite. It is a large, buƩonͲlike

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Lab 10: Invertebrates & Vertebrates

13.
14.
15.

16.

17.

18.
19.

20.
21.
22.
23.

24.

structure on the central disk.
The anus is in the center of the disk.
Using a scalpel, cut one inch from the Ɵp of one of the rays. Study the cross secƟon of the
stump.
Note the ossicles (part of the endoskeleton) on the dorsal surface, the largest of which called
the ambulacral ossicles, which support the ambulacral groove and provide aƩachment for the
tube feet.
Remove the skin from the top of this ray using dissecƟng scissors or scalpel. Do the same for
another ray, and also cut a circular lap of skin from the central disk being careful to keep it as
shallow of an incision as possible.
Note the featheryͲlooking digesƟve glands called the pyloric caeca. These glands make enͲ
zymes that help digest food in the stomach, located under the central disk. The thin sac lying
just above the stomach is the intesƟne. From there, the rectal pouches store small amounts of
wastes before leaving through the anus on the dorsal side of the starĮsh.
Remove the pyloric caeca from one ray, and observe the gonads underneath.
Remove the gonads to visualize the water vascular system. This is an internal water pressure
system. Water enters the system through the madreporite, passes through a series of canals
unƟl it reaches the tube feet. When the ampulla contracts, water is forced into the tube foot,
extending it and allowing it to grab on to a surface.
Running the length of each ray is a lateral canal, to which tube feet are aƩached.
In the central disk, the Įve lateral canals connect to the ring canal.
Note the stone canal connecƟng the ring canal to the madreporite, where water enters. These
canals are diĸcult to locate without disrupƟng them, but see if you can idenƟfy them.
With a magnifying lens, examine the inside wall of the ray to see the supporƟng ridges, the
bulbͲlike ampullae, Ɵny sacs that create sucƟon of the tube feet. You may also noƟce Ɵny
openings in the inner wall. These pores connect with a Įll tube and are part of the external gills
that help the starĮsh to breathe.
As with any biological scraps, it is best to contact your local waste management company for
proper disposal procedure.

QuesƟons
1. What are some common animal traits that a starĮsh does not possess?

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Lab 10: Invertebrates & Vertebrates
Experiment 5: Vertebrate DissecƟon
Frogs are a member of the Amphibia class of vertebrates. In many respects, the anatomy of the frog is
similar to human anatomy. Thus, the study of frog anatomy is a useful tool for science students.
As amphibians, frogs may live some of their adult life on land, but return to water to reproduce.

Materials
Preserved Grassfrog
Flashlight
DissecƟon tray (Styrofoam)
DissecƟon tools
DissecƟng pins
Toothpick
3 in. Fishing line

Figure 15: The dorsal (above) and ventral (below) sides of the frog. Cut lines are shown
on the picture below (green).

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Lab 10: Invertebrates & Vertebrates

Note: To determine the sex of your frog, examine the
Įngers on its foreleg (arm). A male frog typically exͲ
hibits thick pads below the thumbs.

Procedure
1. Place the frog dorsal (back) side up in the dissecƟng tray. Observe the external anatomy of the
skin. Don’t forget to use your sense of touch in this observaƟon (with gloved hands of course)!
2. Locate the following features:

x
x
x

External nares (nostrils)

x
x
x
x
x
x

Internal nares

x

Fat bodies: Located just inside the abdominal wall, these long, thin organs are yellow
or orange in color. You may remove these structures if they obstruct your view of unͲ
derlying organs

Two tympani (eardrums)

Two eyes, each with three lids (the third lid is a transparent covering on the eye)
3. Measure the length of the frog and record this measurement in Table 3.
4. Break a toothpick so that you have a 1in piece. Place this in the frog’s mouth to prop it open so
you can observe the structures of the frog’s mouth.
5. Using the Ňashlight, locate the following features:

6.
7.
8.
9.

10.
11.
12.

Eustachian tubes
Opening of the esophagus
Gloƫs
Tongue

Two kinds of teeth; maxillary teeth help the frog to grip while vornerine teeth point
inward.
Use forceps to grab the tongue and locate where it aƩaches to the Ňoor of the mouth.
Insert the end of the Įshing line into one of the Eustachian tubes and watch the tympanum on
the dorsal side of the frog. This system allows air pressure to be equalized in the frog’s head.
Place the frog in the dissecƟon tray ventral (belly) sideͲup, and pin the arms and legs to the
tray to stabilize the specimen.
Using forceps and dissecƟng scissors, cut along the midline of the body starƟng at the cloaca
(the urogenital opening) as shown in Figure 15. Make shallow cuts so internal organs are not
damaged when cuƫng through the muscle and breastbone.
Make horizontal cuts near the arms and legs, as shown in Figure 15.
Pin the Ňaps to the dissecƟng tray to expose the internal organs. Note: If your specimen is feͲ
male, you may need to remove the eggs and enlarged ovary to view the internal organs.
Using a probe and forceps, liŌ the internal organs around so you can locate the following orͲ
gans:

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Lab 10: Invertebrates & Vertebrates
x

Peritoneum: Directly under the body wall, this aƩached membrane of thin Ɵssue
forms a lining around the internal organs. There are various membranes that hold the
organs in place, called mesenteries, which are also part of the peritoneum.

x

Liver: A threeͲlobed organ that sits high in the body cavity. It is the largest organ visiͲ
ble, and is dark brown in color.

x

Heart: A triangular structure that sits above the liver. Note the thin sac (called the periͲ
cardial sac) that covers this organ and the vessels extending from it. The pericardial sac
can be cut to expose the heart.

x
x

Lungs: Two spongy organs located beneath the liver.
Gall bladder: This bright green organ can be visualized by spreading apart the lobes of
the liver.

x

Esophagus: A tube that transports food from the mouth to the stomach. Insert your
probe into the frog’s mouth and observe where it leads.

x

Stomach: Under the leŌ side of the liver, this bagͲlike digesƟve organ is the Įrst site of
chemical digesƟon in the frog.

x

Small intesƟne: A long coiled tube that serves as a conduit for food and the place
where nutrient absorpƟon into the bloodstream takes place. NoƟce the blood vessels
running through this organ.

x

Large intesƟne: A widening of the small intesƟne signals the start of the large intesͲ
Ɵne. This may be located underneath the small intesƟnes.

x

Spleen: Located in the middle of the body cavity, this dark red, spherical organ stores
blood. You may need to liŌ the stomach and small intesƟnes to see.
13. Using dissecƟng scissors, remove the stomach from the body cavity. Cut it open to invesƟgate
any remains from the frog’s last meal.
14. Remove the small intesƟnes from the body cavity. Measure the length of the small intesƟnes
and record in Table 3.
Table 3: ObservaƟonal Measurements of Frog (Remember to Assign Units Where Appropriate!)

Length of frog

Length of small intesƟnes

Contents of stomach

15. ConƟnue to locate the following organs:

x

Kidneys: Dark, beanͲshaped organs that Įlter wastes from the blood. You may have to
liŌ the intesƟnes to see them, as they are towards the back of the body cavity.

x

Testes (for male specimens): Located above the kidneys, these round organs are typiͲ
cally light in color.

x
x

Oviducts (for female specimens): Curly tubes around the kidneys.

Bladder: A bagͲlike organs that stores urine. Try to trace the tubes from the kidneys to
the bladder.
16. As with any biological scraps, it is best to contact your local waste management company for

128

Lab 10: Invertebrates & Vertebrates
proper disposal procedure.

QuesƟons
1. Classify the specimen you just dissected, starƟng with Kingdom and ending with Species.

2. Describe the appearance of Įve organs you found in the frog.

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