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Introduction to the Animal Kingdom
SURVEY OF THE ANIMAL KINGDOM LABORATORY
Instructions for Students fall 2008
Read and understand pages G1- G5 in the lab manual
(Skip pages G6 & G7)
Read and understand pages G8- G17 in the lab manual
(Skip pages G18 & G19)
In lab, answer the questions for Part II, on pages G20-G23
(Skip pages G24 & G25)
In lab, you will be dissecting and examining specimens of four phyla. This is a brand new
part of this lab and it is not described in the lab manual. There are separate instructions
for this section that are included below. Before lab, you should carefully study the
instructions and the diagrams of these specimens.
Redesign of the front cover of the lab manual.
The front cover diagram is out of date because of new DNA information that indicates
that the relationships of some of the groups shown on the old cover are wrong. For
example, the pseudocoelom is no longer considered “primitive,” and the annelids are no
longer seen to be ancestors of the arthropods. Using the information that is depicted on
Figure 33.5 in your text and copied below, redesign a new cover for the manual.
For your new cover, use only the phyla that we have used on the old cover. And you do
not have to draw pictures of the animals only the names of the taxa are needed.
Introduction to the Animal Kingdom
PART II – FOUR SIMPLE PHYLA
There are four stations that you will visit in this part of the lab. Each station has
representatives of a different phylum: Porifera, Cnidaria, Platyhelminthes, and Nematoda.
You will be assigned one phylum and it is your job to learn about the group and teach the
other members of your team the key characteristics of the taxon. This is the most
important part of your job; it is NOT to spend all of your time answering the questions.
~PHYLUM PORIFERA – THE SPONGES~
Sponges are the simplest of all multicellular animals. They are placed into a separate
subkingdom because of their unique nature. They have no distinct organ systems—no
glands, no digestive tract, no muscles, no nervous system, no sense organs, no excretory
system. Their body wall is perforated by small pores through which water enters. Water
moves into the sponge because tiny collar cells in the body wall (choanocytes) have
flagella drawing the water inside. Tiny food particles in the water are engulphed by these
collar cells and amoebocytes lining the pathway and are digested in their food vacuoles.
The sponges have an internal skeletal support system of microscopic needles (spicules)
composed of calcium carbonate, silicon, or as in bath sponges, a fibrous protein network
called spongin. These skeletal differences are used to classify sponges.
1) Examination of Grantia, a simple sponge. Remove a Grantia from the dish at the
station using your forceps. Be gentle so as to not crush the center of the sponge. Try to
grab it at one end and lay it flat in the dissection pan. Observe the outer characteristics of
the animal under the microscope. The body has several pores perforating the body called
incurrent pores. Water flows in through these pores and into the radial canals, which
empty into the central cavity, the spongocoel and exits though the osculum
.
Introduction to the Animal Kingdom
Using your scissors and forceps, CAREFULLY lift the Grantia and make a horizontal cut
through the midsection. If you did not add water to float your specimen before, now
would be a good time to do so. Observe the spongocoel by using your fine point probe
and forceps to open the center cavity in the water. Notice that it is hollow, and that the
incurrent pores do indeed penetrate through the body. When you are finished, be
prepared to show your teammates what you have learned.
2) Now look at the small bottle holding the tiny sponge colony called Leucosolenia
under the microscope. You will see clusters of the same type of sponge as Grantia
living together . Can you see the oscula of the separate individuals?
Introduction to the Animal Kingdom
3) Now look at the slides showing cross and longitudinal sections of Grantia where
you should be able to see the cells lining the canals. Be sure and look at slides of
spicules and spongin.
4) Lastly, go see the posters and larger examples of sponges.
QUESTIONS:
1. What are the three types of skeletal material in sponges?
2. What is name of the subkingdom that includes the sponges? What is the logic behind
separating this group out from all of the other multicellular animals?
3. Sponges seem to be the earliest of all of the multicellular organisms to evolve. Setting
the fossil and DNA evidence aside, what is the logic behind this prediction?
4. How do sponges gain their energy and nutrients?
5. Trace the path of water flowing through Grantia.
In ____________-->_______________-->______________-->______________--> Out
6. Name the cells that create the water currents.
7. How do you imagine that sponges get rid of waste products since they have no
digestive tract or kidney?
8. Sponges are capable of reproduction. Since sponges don’t move around, how do you
imagine that they accomplish this?
Introduction to the Animal Kingdom
~PHYLUM CNIDARIA – JELLYFISH, SEA ANEMONES, & CORAL~
The phylum Cnidaria is one of the earliest multicellular groups to evolve. They exist as
solitary individuals or in colonies. Their basic anatomy consists of a sac-like body with a
single opening that serves as both a mouth and an anus (incomplete digestive tract); a
body wall consisting of two embryonic tissue layers, an external ectodermis and an
internal endodermis with a jelly-like substance (mesoglea) between them; radial
symmetry; stinging cells called cnidocytes or cnidoblasts that eject tiny dart-like
harpoons (nematocysts) for attack and defense; and simple organ systems including a
nerve network, muscles, and simple sense organs like light receptors and balance organs.
There are two basic body types in this phylum: the medusa form, a free-swimming
jellyfish and the polyp or tubular shaped form (hydroid) , looking like a sea anemone.
Some species have both stages in their life cycle and the generations alternate
(alternation of generations), and other species have only one. Obelia is an example.
1) Observe the two different body forms on the slides of Obelia now
Both of the life stages of this animal’s life cycle are microscopic and are hardly likely to
be seen in nature because of their diminutive size. Be sure and show these slides to your
teammates with an explanation of the cycle. In the hydoid stage identify the feeding
polyps and the reproductive polyps (with the medusa buds inside). Did you see the small
gonads (darkly stained dots) in the medusae? There are separate male and female
medusae that form sperm and eggs.
Introduction to the Animal Kingdom
2) Sea anemone dissection. Obtain a sea anemone from the jar in front of you and
observe the external features. There is no medusa stage in this species’ life cycle. This
polyp stage is the only stage. Your job is to identify the major organs and teach your
teammates about the organism.
Note first that the animal has radial symmetry. Then starting at the top of the organism,
there are tentacles surrounding a slit-like mouth. At ends of the mouth there is a ciliated
groove called a siponoglyph. This groove acts as a channel for the circulation of water.
The tentacles have stinging cells (cnidoblasts or cnidocytes) which fire dart-like
nematocysts that inject a toxin into predators or prey which are then stuffed into the
mouth and digested within. At the base of the sea anemone is the muscular basal disk,
which grips onto rocks.
The cnidoblasts are not under the control of the nervous system. These stinging cells are
formed in the body epidermis and then migrate to the tentacles. Once there, they are only
fired when the correct combination of mechanical and chemical occurs such as when
small prey organisms like crustaceans, fish, worms, and larvae are touched. Clown fish
often live within sea anemones; the mucus on their body doesn’t trigger the firing of the
nematocysts. Interestingly, certain flatworms and slugs that eat Cnidaria also do not
discharge the nematocysts even during digestion, and the nematocysts will migrate to the
flatworm’s or slug’s surface and still be able to fire. Thus, they now act as defensive
projectiles for their new owners.
There are over 30 types of nematocysts found in different cnidarians: only some are the
stinging type with a harpoon-like structure carrying venom, others have a sticky surface
that stick to prey, or lasso-like strings that wrap around prey.
3) Look at a cross-section of a hydra slide and you will see cnidotoblast cells
embedded in the body wall.
Introduction to the Animal Kingdom
The dissection of the sea anemone is simple. Carefully use your scissors to cut down the
middle of the specimen.
• Open your scissors and place one blade inside the mouth while leaving the other
on the outside and cut vertically all the way down through the basal disc. Do not
worry about cutting through anything important, as you will see later there really
is nothing to damage. However, use care to make a clean cut so that the specimen
is preserved enough to be handled and shared.
• Once you have made one cut through your specimen, fold the body back carefully
until it will stay open like a book. Try to avoid damaging the inside. Make minor
additional cuts at the base and head if necessary to the body remains open
Inside the sea anemone, you will again notice the radial symmetry. There are no obvious
organs like a liver, pancreas, or kidney. Like all Cnidaria, the anemone has a net-like
nervous system without a central brain, but you will not see this with this simple
dissection. But you will see that the sea anemone has a long muscular throat, pharynx, or
gullet located in the middle of the specimen leading to the gastrovascular cavity, or
enteron. Partially digested food is often found at the bottom of the enteron.
The digestive tract lacks an anus; waste products are regurgitated out of the mouth and so
are the sperm and eggs. The gastrovascular cavity is partitioned by curtain-like muscular
membranes called mesenteries or septa, the edges of which secrete digestive enzymes.
There are small openings in the septa, ostia, which allow water to pass between the
internal compartments. When the longitudinal muscles of the septa contract, the animal
retracts. When circular muscles around the body contract, the animal elongates. The septa
often end in thin strands called acontial filaments which are loaded with nematocysts.
The acontia can be extended out the mouth when the animal is disturbed.
Introduction to the Animal Kingdom
4) Jellyfish Observation: Examine the large jellyfish in a bowl at the station, a medusa
form of the Cnidaria, which is extremely fragile. There is no polyp stage in this species’
life cycle, only the medusa stage. Your job is to identify the major structures and show
them to your teammates.
The umbrella-like shape is maintained strictly by water and body fluid pressure; we say it
has a hydrostatic skeleton. Be very careful in handling the specimen. Carefully, using
your blunt probe and your fingers, find the mouth (located on the underside), gonads,
tentacles, oral arm, and the four gastric pouches that serve as a stomach. Rhopalia
are sensory indentations around the bell with simple eyes (ocelli) and gravity
detectors (statoliths).
5) Look at the poster. Be sure you spend time with the poster and examine different
types of coral. These coral skeletons have been secreted by polyps living within them for
support. You should be able to spot the small holes where the polyps lived.
Introduction to the Animal Kingdom
QUESTIONS
1. What kind of symmetry is characteristic of the Cnidaria?
2) Name the embryonic layers that they have? What is the term that we apply to this sort
of organization when there are only two body layers?
3) What are the specialized cells called that are used to capture prey?
4) How is digestion and solid waste disposal achieved?
5) What do you notice about the fundamental structure of the polyp & the medusa stages?
6) Many corals polyps secrete calcium around themselves protecting themselves in a
solid exoskeleton fortress. But other species such as jellyfish and sea anemones have no
such skeleton. How do they maintain their shape?
7) Jellyfish are able to open and close their umbrella-like shapes and move about. This is
due to muscle-like myofibrils. Sketch how these myofibrils would be oriented in the body
of a jelly fish.
8. Sea anemones are able to elongate and contact, thus getting taller or shorter. Sketch a
sea anemone and show and describe how the muscles would be arranged in the body to
achieve such effects.
9. Why do you think that experts consider the Cnidaria an early stage of multicellular
evolution?
Introduction to the Animal Kingdom
~PHYLUM PLATYHELMINTHES – THE FLATWORMS~
Flatworms and all other major phyla (except the Porifera and Cnidaria) that we will
examine throughout the semester are bilateral; i.e. they have a distinct head with two
sides forming their body. Most Platyhelminthes are parasites. The two major body types
that you will find at this station are the flat elongated leaf shaped species called flukes
and the long segmented shaped species called tapeworms. Your job is to identify the
major organs and show them to your teammates with a clear explanation of their
function.
1) Look at a preserved and stained slide of planaria, Dugesia. It is a free-living form
shown below. Identify as many of the structures you see labeled below as possible, and
certainly don’t miss the eyes. Notice that the mouth is in the middle of the body and the
digestive tract does not end in anus. And there isn’t any circulatory system.
Why do you think that the gut is called a gastrovascular cavity?
Introduction to the Animal Kingdom
2) Parasitic flukes: Look at the stained slide of the Chinese Liver fluke that lives in
humans, Clonorchis. This time you will note that the mouth is at the front end of the
body. Again, see how many structures you can identify, along with the obvious
similarities with the planaria. But no eyes? Presumably their free-living ancestors had
eyes. Why don’t these flukes have eyes? And don’t say it is a question of “need.”
3) Now take a preserved specimen of the sheep liver fluke, Fasicola hepatica, from
the jar in front of you and place it on a slide and slip it under the microscope. Turn on
the light below the specimen and see if you can find similar structures labeled here
below.
Introduction to the Animal Kingdom
4) Tapeworm slides: Finally, look at the composite slide showing various body
segments of a tape worm (Taenia pisiformis) that lives in the intestines of dogs. On
this slide, you will see the head of the worm, the scolex. Can you see the hooks on the
head that allows the worm to hang on to the gut of the dog? (They may be easier to find if
you look at the separate slide of the scolex at this station.) Then note how the segments of
the body get larger as one moves toward the tail end. The segments, called proglotids,
mature as they move toward the tail. They are largely filled with reproductive organs and
eggs. The segments break off of the tail and are eliminated when the dog defecates. If
another dog, wolf, or fox chances to eat an egg, it too will become infected.
Be sure that you can point out all the important structures to your teammates.
5) Poster: Be sure and visit the poster showing the various species of
Platyhelminthes. There will be some additional specimens there for you to see.
Introduction to the Animal Kingdom
QUESTIONS
1What do flukes have in common with the cnidarians when it comes to digestion?
2) Platyhelminthes lack a circulatory system. How is it possible that nutrients can reach
the cells of their bodies without a circulatory system?
3) Tapeworms have specialized segments used for reproduction. What are the segments
called? Briefly describe the reproductive process
4) How do flukes and tapeworms differ by the means they obtain food? Be specific!
5) Why do you imagine that Platyhelminthes are considered one of the earliest bilateral
phyla to evolve?
6) How do you imagine that the parasitic life cycle could have evolved from free-living
species?
7) Platyhelminthes are considered to be acoelomates. What does this mean?
Introduction to the Animal Kingdom
~PHYLUM NEMATODA – ROUNDWORMS
Roundworms were originally considered primitive because even though they were
bilaterally symmetrical, they had a pseudocoelom. Now that DNA evidence is available,
they are seen as a phylum that once had a coelom and then modified the arrangement.
The phylum consists of both parasitic species and free-living forms that are unbelievably
abundant in soil. You will see both at this station. Be sure that you learn about the major
organ systems so that you can teach the important points to your teammates.
1) First, look at the free-living “vinegar eels.” Take a drop of vinegar solution in a
pipette and place it into a slide with a depression in it. Then slip the slide under the
microscope and take a look at the vigorous swimming of the minute nematodes which
thrive in vinegar. It is presumed that parasitic nematodes have evolved from free-living
species like these that live in the soil.
2) Now dissect a preserved specimen of a common parasite (Ascaris) that lives in the
gut of pigs and humans. You will need approximately 20 – 30 dissection pins for this
dissection which needs to be done EXTREMELY CAREFULLY under the dissection
microscope.
Obtain a worm from one of the tubes at the station using your forceps. Be extremely
gentle as to not crush or tear the specimen. Try to grab at one of the ends and lay it as
flat and as straight as possible in the dissection pan. Locate the anterior and posterior
ends. You can determine whether you have a male or female by looking at the posterior
end. If it is a male, it will have a little curl in the tail. Pin your specimen with one pin to
the head and one pin to the tail. Try to avoid the corners of the pan, since these are the
hardest spots to see under the dissection microscope due to poor lighting.
NOTE: For this dissection, you will primarily use your fine point probe and your
forceps. Have your scissors nearby in case you need to make a small cut to prevent
tearing the skin or the specimen. This specimen is FRAGILE and will tear without
notice. USE EXTREME CARE IN THIS DISSECTION! Before you start, look at
the specimen that has been prepared as a demonstration by the TA.
a) Find the middle of the Ascaris and gently poke an extremely shallow hole in the
body. Maintaining your depth, lift the skin away from the digestive tract that should
now be visible. Trace all the way down the middle to one end, and then start back in
the middle and trace to the other gently tearing the skin.
*Note: Stay shallow, steady, and slow while performing this dissection.
b) Using approximately 20-26 dissection pins, pin the skin back by inserting your
pins from the middle outward and turning the pins outward before inserting them into
the pan. The pins should be gently but firmly pulling the skin away from the
digestive tract. Press the pins down at 45° angles. DO EVERYTHING POSSIBLE
TO AVOID PINNING OR TEARING THE INSIDES!!
c) Take your completed dissection to a sink where you will partially fill the dissection
pan. BUT BE CAREFUL HERE. But before you put water into the pan first, turn on
the water to test the outflow. You are looking for a low, smooth, even flow of water
Introduction to the Animal Kingdom
(no spurting or speed) to prevent the specimens insides from tearing. They will tear if
the pressure is too high or if your pan is too far away from the faucet. Fill your
dissection pan half way with cool water. Fill your pan at one of corners most distant
from your specimen for optimal results.
d) Place the specimen under the dissection
microscope. Identify the mouth, pharynx,
and anus.
e) Starting at the mouth, use your fine point
probe and either your forceps or blunt
probe, trace the intestines from head to tail.
When you arrive at where the
entanglement begins you have found the
reproductive organs.
f) In the female, the vagina starts the
reproductive organs. Gently try to pull
them away from the intestines all the way
down until you arrive at what looks like a
clump of string. This is the ovary. Once
you have separated the reproductive organs
from the intestine, follow the reproductive
organs from the vagina along to the paired
uteri, which are full of eggs, to the paired
oviducts and ending at the ovaries.
h) If you have a male, at the tail end you
will find 2 spicules that are used to pry
open the vulva during copulation. The
ejaculatory duct opens into the end of the
gut at the cloaca. The ejaculatory duct
leads forward and swells into the long
seminal vesicle, which stores sperm. From
there, the vesicle narrows to from the vas
deferens which coils around and ends in
the testis.
Note: that you only see a digestive tract and
reproductive organs!
Be sure that you can teach your teammates
about the organism.
3) Slides of Ascaris: Take a look at the cross-section and longitudinal sections of
Ascaris and see if you can identify the structures that you just have seen in the
dissected specimen.
4) Poster: Be sure that you visit the poster to see various species of nematode.
Introduction to the Animal Kingdom
QUESTIONS
1. How is the digestive system of Ascaris different from those of the Cnidaria and
Platyhelminthes?
2. How might you imagine that the parasitic life habit evolved from a free-living
form?
3. Nematodes lack a circulatory system. How do nutrients get distributed from the
digestive tract to the other cells in the body?
4. What type of symmetry do the nematodes possess?
5. What type of skeleton does this phylum possess?
6. Considering the life cycle of Ascaris (p age G5 in the lab manual), what is the best
way of preventing human infection?
7. When we say that an animal has a pseudocoelom, what do we mean?