Animals

Lab 10
Invertebrates & Vertebrates
113

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Lab 10: Invertebrates & Vertebrates

Concepts to explore:
x
x
x
x
x

Characteris?cs of animals
Heterotrophs
Symmetry
Invertebrates
Vertebrates

Introduc?on
The kingdom Animalia comprises millions of species, ranging from the snail to the hippopotamus, the
ant to the elephant, the cen?pede to the human. Though there are notable di?erences in body shape
and func?on, almost are mo?le, mul?cellular eukaryotes, with dis?nct ?ssue structures that perform
specialized func?ons (i.e., heart, stomach) and almost all par?cipate in sexual reproduc?on. Unlike
plants, animals cannot produce energy from sunlight and, as heterotrophs, acquire energy by consum?
ing organic material (other plants and animals).
Useful characteris?c for classify animals is symmetry, or the balanced division of their form. Radial
Symmetry, as is seen in star?sh, is a division origina?ng in the center and protruding outwards that
produces even and balanced sec?ons. 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 en?re object. Asymmetry occurs when there can
be no even division, as is seen in a sponge.
Animals are classi?ed into two categories based on structure.

x

Invertebrates are organisms that lack an endoskeleton, such as the jelly?sh, 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 signi?cant adap?ve advantage that enables vertebrates
to occupy di?erent 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 sta?onary ?lters, sponges play an important role in aqua?c systems, feeding on par?cles

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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 asymmet?
ric body is a loose assembly of cells (no ?ssues) that support a
skeleton of collagen ?bers and spicules. Sponges reproduce
both sexually and asexually.

Figure 1: Porifera

x

The phylum Cnidaria includes jelly?sh,
corals, sea anemones, and hydras (Figure 2).
They were the ?rst to develop nerves and muscles and typically alternate
between two body forms: the free?swimming medusa and the sta?onary
polyp. Both body types consist of three layers of ?ssue surrounded by ten?
tacles with s?nging cells containing ?ny, toxic harpoons that can be used in
either defense or o?ense. 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, para?
si?c tapeworms and ?ukes. They are some of the simplest bilaterally symmetrical organ?
isms with a de?ned 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 diges?ve system. Clusters of light?sensi?ve cells
make up their eyespots. They are hermaphrodi?c, capable of both sexual and asexual re?
produc?on.

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

x

es (Figure 3). They are bilaterally symmetric with a segmented body cavity
o?en represented by a tube within a tube design. Each segment has ?ny
hairs called setae which help the organism to move. Segmenta?on was
an important development that provides dis?nct regions to specialize in
di?erent tasks. A one?way diges?ve tract, closed?circulatory system, and
central nervous system also di?eren?ate this invertebrate. Annelids play
a signi?cant ecological role by reworking soil and sediments.

The phylum Arthropoda, the most diverse and numerous of
the Animal Kingdom, includes insects, crustacean, spiders, mil?
lipedes, and cen?pedes (Figure 4). All arthropods have seg?
mented bodies and are covered in a hard, ?exible exoskeleton.
Their muscles from their jointed appendages a?ach to the in?
side of this protec?ve cover. Many species, such as dragon?ies
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 collec?vely
may ingest and excrete 3 metric
tons of sand per year!

mul?ple life cycles. Their open body cavity which contains ?s?
sues, organs and a complete diges?ve tract.

xThe phylum Mollusca includes clams, snails, slugs and the octo?

pus (Figure 5). Though
there is a great deal of di?
versity within this phylum,
all mollusks have so? bodies, many of which are cov?
ered by a hard calci?ed shell. The shell is secreted by
a layer of ?ssue called the mantle. A muscular foot
provides locomo?on and grasping. A coarse, ?le?like
organ (the radula) allows most mollusks to drill into
Figure 5: Mollusca
their prey or snag ?sh. Many hunt by propelling water
through a siphon either for locomo?on or to capture food. A mantle cavity houses gills and
one?way diges?ve system.

x

The phylum Echinodermata includes sea stars, sea lilies,
sea urchins, sea cucumbers, and over 6,000 other salt wa?
ter species (Figure 6). Instead of bilateral or radial sym?
metry, echinoderms exhibit ?ve part symmetry in their
bodies. Their hard, ?exible bodies are composed of small
calcium plates that are o?en spiny and covered by a thin
skin. Inside is a complete diges?ve system and a special
Figure 6: Echinodermata
?uid??lled system that operates tube feet (which some?
?mes 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 cle?s (the structures located behind
the mouth and in front of the esophagus), bilateral symmetry, segmented muscles,
and a protec?ve layer (feathers, scales, hair, fur, etc.,).

x Two main groups of the subphylum vertebrata include ?shes and tetrapods (amphibians,
rep?les, birds, and mammals).

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Lab 10: Invertebrates & Vertebrates
x

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

x

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

x

Rep?les live almost en?rely 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 long?lived. Though there are obvious
di?erences between human beings and other mammals,
there are also many similari?es. 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 ?ssue 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 bo?le with curled straw

4. Top of a liquid bo?le

5. Balloon

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Lab 10: Invertebrates & Vertebrates
Experiment 2: Crea?ng a Phylum Key
1. The phylum characteris?c table contains all of the main features of the eight main phyla. Your job is
to organize and iden?fy which characteris?cs belong to which phyla in the key. The number of lines
in the key represents the number of characteris?cs that fall into each phylum.

Table 1: Phylum Characteris?c Table

1

2

3

4

5

A

Bilateral phy?
lum with seg?

Most have a
calcium con?

Five part sym?
metry

Specialized
cell, but no

Mantle of ?s?
sue covering

B

Hollow body
cavity for food

Setae used for
movement

Jaws and skulls
part of evolu?
?on

Complete di?
ges?ve tract

The ?rst to
have jointed
legs

The ?rst phy?
lum to ?y

Some have
s?nging cells

Tube feet

First muscle
and nerves

Internal skele?
ton

Three ?ssue
layers, no
body cavity
Water ?ows
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 diges?

All have verte?
bral column

Champions of
varia?ons in
appendages

F

Has the most
species

Have spines
covered with a
thin skin

Some sta?on?
ary polyps

Some are mo?
bile medusa

Some propel
using their
siphon

G

Muscular foot
used to move

Sta?onary ani?
mal

Tubular mouth
at the mid?
body

Humans

Hard but ?exi?
ble bodies
with small

H

Spicules are
the skeleton

Radula used to
feed

No symmetry

Exoskeleton

Their burrow?
ing has a?ect?
ed the global

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

Porifera

Cnidaria

Platyhel?
minthes

Annelida

Arthropoda

Mollusca

Echinodermata

Chordata

Experiment 3: Taxonomy
Iden?fy which phylum each of the following organisms belongs in. Next to each, list the criteria
used in your determina?on.
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 add?on for the Invertebrate Lab. Unless your teacher
has speci?cally requested that dissec?on materials be included within your kit, you will NOT have the
supplies to perform the next two experiments.

Experiment 4: Invertebrate Dissec?on
The star?sh is not a ?sh at all, rather an invertebrate that possesses no internal skeleton. Members of
the phylum Echinodermata, star?sh are unique in that they are deuterostomes (instead of proto?

Materials
Preserved star?sh
Dissec?ng tray
Dissec?ng tools
Magnifying lens

Note: When performing a dissec?on, remember these important safety notes:

x
x

Dissect with the scalpel or scissor blade cu?ng away from you (and your lab partner).
If you develop an allergic reac?on to the preserving ?uid, contact your healthcare
provider. Also, inform your instructor and inform him/her of your situa?on.

x

Contact your local waste management company for instruc?ons for the proper dis?
posal of your specimen.

x

Wash your hands, dissec?on tools, and all work surfaces with soap and water when
?nished with the dissec?on.

stomes like earthworms, grasshoppers, clams, etc.). Deuterostomes exhibit incomplete segmenta?on,
and a brain and spinal cord above the gut, among of other di?erences with protostomes. Star?sh have
no front or back, and can move in any direc?on without turning.

Procedure
1. Examine the external anatomy of the star?sh. 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 (le?) and oral (right) surfaces of the star?sh.

2. Run your gloved ?nger over the surface and note the texture. Use the magnifying glass to ex?
amine the spiny skin in detail.
3. Along with the s?? spines, you may also see small, hair?like gills used by the star?sh to take in
oxygen.
4. Pedicellaria are ?ny pincers that look like pliers that are used to grip small objects.
5. Place the star?sh ventral side up and note the tube feet that run down the arms, or rays, of the
star?sh. They will be located on either side of the groove that runs from the ?p of each ray to
the center.
6. Find the mouth in the center of the star?sh.
7. On the oral surface of each arm are open ambulacral grooves extending from the mouth to the
?p 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 star?sh so the dorsal side is facing up.
10. Note the eyespots at the ?p of each arm, which allows the star?sh to sense and respond to
light. To see the eyespots, and spread the tube feet at the ?p of the ray and examine it closely
with the magnifying lens.
11. The ?at central disk is at the center, and ?ny, hollow, ?nger?like gills cover the body of the star?
?sh.
12. The opening of the water?vascular system is called the madreporite. It is a large, bu?on?like

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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 ?p of one of the rays. Study the cross sec?on 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 a?achment for the
tube feet.
Remove the skin from the top of this ray using dissec?ng 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 feathery?looking diges?ve glands called the pyloric caeca. These glands make en?
zymes that help digest food in the stomach, located under the central disk. The thin sac lying
just above the stomach is the intes?ne. From there, the rectal pouches store small amounts of
wastes before leaving through the anus on the dorsal side of the star?sh.
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
un?l 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 a?ached.
In the central disk, the ?ve lateral canals connect to the ring canal.
Note the stone canal connec?ng the ring canal to the madreporite, where water enters. These
canals are di?cult to locate without disrup?ng them, but see if you can iden?fy them.
With a magnifying lens, examine the inside wall of the ray to see the suppor?ng ridges, the
bulb?like ampullae, ?ny sacs that create suc?on of the tube feet. You may also no?ce ?ny
openings in the inner wall. These pores connect with a ?ll tube and are part of the external gills
that help the star?sh to breathe.
As with any biological scraps, it is best to contact your local waste management company for
proper disposal procedure.

Ques?ons
1. What are some common animal traits that a star?sh does not possess?

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Lab 10: Invertebrates & Vertebrates
Experiment 5: Vertebrate Dissec?on
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
Dissec?on tray (Styrofoam)
Dissec?on tools
Dissec?ng 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
?ngers on its foreleg (arm). A male frog typically ex?
hibits thick pads below the thumbs.

Procedure
1. Place the frog dorsal (back) side up in the dissec?ng tray. Observe the external anatomy of the
skin. Don’t forget to use your sense of touch in this observa?on (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 un?
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 ?ashlight, locate the following features:

6.
7.
8.
9.

10.
11.
12.

Eustachian tubes
Opening of the esophagus
Glo?s
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 a?aches to the ?oor of the mouth.
Insert the end of the ?shing 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 dissec?on tray ventral (belly) side?up, and pin the arms and legs to the
tray to stabilize the specimen.
Using forceps and dissec?ng scissors, cut along the midline of the body star?ng at the cloaca
(the urogenital opening) as shown in Figure 15. Make shallow cuts so internal organs are not
damaged when cu?ng through the muscle and breastbone.
Make horizontal cuts near the arms and legs, as shown in Figure 15.
Pin the ?aps to the dissec?ng tray to expose the internal organs. Note: If your specimen is fe?
male, you may need to remove the eggs and enlarged ovary to view the internal organs.
Using a probe and forceps, li? the internal organs around so you can locate the following or?
gans:

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Lab 10: Invertebrates & Vertebrates
x

Peritoneum: Directly under the body wall, this a?ached membrane of thin ?ssue
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 three?lobed organ that sits high in the body cavity. It is the largest organ visi?
ble, and is dark brown in color.

x

Heart: A triangular structure that sits above the liver. Note the thin sac (called the peri?
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 le? side of the liver, this bag?like diges?ve organ is the ?rst site of
chemical diges?on in the frog.

x

Small intes?ne: A long coiled tube that serves as a conduit for food and the place
where nutrient absorp?on into the bloodstream takes place. No?ce the blood vessels
running through this organ.

x

Large intes?ne: A widening of the small intes?ne signals the start of the large intes?
?ne. This may be located underneath the small intes?nes.

x

Spleen: Located in the middle of the body cavity, this dark red, spherical organ stores
blood. You may need to li? the stomach and small intes?nes to see.
13. Using dissec?ng scissors, remove the stomach from the body cavity. Cut it open to inves?gate
any remains from the frog’s last meal.
14. Remove the small intes?nes from the body cavity. Measure the length of the small intes?nes
and record in Table 3.
Table 3: Observa?onal Measurements of Frog (Remember to Assign Units Where Appropriate!)

Length of frog

Length of small intes?nes

Contents of stomach

15. Con?nue to locate the following organs:

x

Kidneys: Dark, bean?shaped organs that ?lter wastes from the blood. You may have to
li? the intes?nes 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 typi?
cally light in color.

x
x

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

Bladder: A bag?like 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

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Lab 10: Invertebrates & Vertebrates
proper disposal procedure.

Ques?ons
1. Classify the specimen you just dissected, star?ng with Kingdom and ending with Species.

2. Describe the appearance of ?ve organs you found in the frog.

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