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Nasty Cnidarias Book Assignment
1. (pg. 119) Cnidarians have developed tissues (groups of cells that work together to perform
specific functions). The development of tissues makes it possible for these organisms to:
a. swim
b. respond to the environment
c. hunt and eat prey
d. all of the above
2. (pg. 118) The cnidarians phylum used to be called the coeleterate phylum but when scientists
learned that these animals did not have a true coelom (body cavity because they don’t have a
separate anus) they had to change the phylum name to cnidarian (named after their stinging
cells). Fill in all animals belonging to the cnidarian phylum?
a. sea anemone
b. snail
c. jellyfish
d. coral
e. eel
ab. octopus
3. (pg. 119) These organisms all have radial symmetry so that they can sense their surroundings
equally all of the way around (they don’t need to swim so it works perfectly), but they have a
mouth end called the ___________surface and the NON-mouth end called the
________________ surface.
a. aboral and oral b. oral and aboral
4. (fig. 7.6)The basic body form of a cnidarian whose oral surface is pointing up is a
__________ and if the oral surface is pointing down it is called the ____________ body plan.
a. polyp and medusa
b. medusa and polyp
5. (pg. 117) During development the cnidarians may undergo metamorphism between the polyp
or medusa phase. Describe its starting larval form known as a planula:
a. it has numerous leg appendages
b. it has highly folded, thin membranes
c. it forms a ball of ciliated cells
6. (pg. 116) The one opening known as the gastrovascular cavity (or simply called the gut in
your textbook) is surrounded by tentacles. How do they capture small prey and get them into
their gastrovascular cavity?
a. using their zooxanthellae
b. using their nematocysts
c. using their mesenteries
7. (pg. 117) Cnidarians have two cell layers (called diploblastic). These layers include the
________ layer lines the stomach/gastrovascular cavity (sometimes called the endoderm) and
the _________ is the external layer on the outside of the body (sometimes called the ectoderm)
(hint: epi means upper).
a. epidermis and gastrodermis
b. gastrodermis and epidermis
8. (pg. 117) Between these two cell layers is the middle layer made up of a jelly-like substance
called the ___________.
a. ameboid gel b. ganglia c. nucleus d. mesoglea
9. (p117) The Cnidarian phylum is divided into classes. Siphonophores are hydrozoans are
specialized polyps that work together form colonies. The class hydrozoa is made of either
colonized or single polyps. Which of the following is not a job performed by one of the polyp
members belonging to this colony?
a. excretion
b. feeding
c. reproduction
d. defense
e. forming the float
10. (pg. 118) Which class below contains organisms that live most of their lives in the medusa
form (besides cubozoa)?
a. Anthrozoan b. Hydrozoans
c. Scyphozoans
11. What is the top of the medusa jellyfish called?
a. hydra b. mesoglea
c. bell
d. gastrovascular
12. Pg. 119. Cnidarians release enzymes into their gut to digest the food. This is known as
_________digestion. Then the food is absorbed into the cells that line the gut so they can finish
digestion.
a. intracellular
b. extracellular
13. Pg. 119. Describe the nervous system of cnidarians:
a. it uses amebocytes
b. nerve net
c. ganglia bundles of nerves
d. centralized brain and spinal chord
14. Pg. 120. Some medusa formed cnidarians have small, fluid-filled chambers containing
calcareous bodies. These fluid-filled cavities are called statocytsts. What are the statocytsts
used for?
a. hearing b. taste
c. seeing d. balance
15. Pg. 120. Why are comb jellies (phyla ctenophora) classified as belonging to the cnidarian
phylum and are not considered true jellyfish?
a. they lack their own stinging cells b. they lack an anus
c. all of the above
16. Pg. 120. What are the ciliary combs of cilia used for?
a. swim b. sticky to collect food
c. sting predators
19. Pg. 120. What do colloblast cells do?
a. swim b. sticky to collect food
c. sting predators
d. diffusion
20. Pg. 120. Some comb jellies have nematocyst. How did they get them?
a. their food
b. evolution
21. Comb jellies are neat because they can produce a prism (rainbow) of colors by refracting
light when they move their cilia combs in waves. They are native to the Atlantic Coast of
North America, but humans accidentally introduced them to a new location and they are now
invading the new locations where they have no natural predators. Go to pg. 404 and read the
second paragraph of the first column on Invasive Species (species invading new habitats) to
explain how they are desecrating (destroying) those ecosystems they are invading (fill in ALL
that apply):
a. eats all the phytoplankton b. eats a large amount of fish eggs c. eats all the other fish’
zooplankton food
23. Pg. 119: The Case of the Killer Cnidarians Box. Tentacles of the Portuguese Man of War
are 30m long so they can sting you before you even see the danger, but can the tentacles that
wash ashore among beach debris still sting you?
a. yes b. no
25. Pg. 119. The Portugese Man of War (Physalia) has very powerful stings. Fill in ALL of the
good ways to treat their sting:
a. wash with freshwater
b. wash with seawater c. vinegar d. alcohol e. urine
26. Pg. 119. Cubomeusae (also called sea wasps, box jellies in Australia, and irukandji in
Indonesia) are small, clear and have 15 ft. long tentacles you can’t see very well. They can kill
you because they inject you with a neurotoxin that stops all of your muscles including your
heart, breathing diaphragm, and swimming muscles. The Portugese Man of War has less
severe symptoms. Fill in ALL that apply:
a. pass out from extreme pain
b. nausea
c. enhanced breathing
d. shock, death, and eye damage
Classify the subgroup (you may use them more than once):
a. cubozoa
b. hydrozoa
c. scyphozoan
d. anthozoan
29. The majority of their life is spent in the polyp form . Most of the organisms’ lives are spent
in colonies of interconnected polyps. Different polyps perform different jobs within the
colony.
30. Small cube shaped deadly medusa.
31. The majority of this organism’s live is spent in the large medusa form with a thick bell.
32. Solitary or colonial polpys that lack a medusa stage and look like sea flowers. Includes
coral and sea anemone.
33. Portuguese Man of War with its floating colony of polyps that float like a medusa as a
whole. They are called siphonophores.
Cnidarian Review - Critical Thinking Questions
Name____________________________
1. Which of the following is something that all cnidarians have in common and is unique to
cnidarians (in notes or pp):
a. they all have stinging cells
b. they lack a separate anus
c. they all have mesoglea
and nerve net
d. all are correct
2. Why is cnidarian a good name for this phylum (think about the names of their unique
characteristics)? They are named after their:
a. jelly-like substance
b. stinging cells
c. lack of anus
d. method of
embryo development
3. Fill in ALL methods used by hard corals and some sea anemone to obtain energy AND circle
the method using LEAST energy:
a. chemosynthesis
b. symbiosis with photosynthetic algae c. hunting with stinging
tentacles
d. absorbing heat
4. How does the cnidocyte spring its nematocyst:
a. osmosis controlling its hydraulic pressure
b. ameobocytes controlling the size of the operculum
c. diffusion of gasses increasing the pressure inside the cavity
5. There are 32 different types of nematocysts. A sea anemone may contain as many as six
different kinds of
nematocysts at one time. Which of the following is a function of nematocyts?
a. sticking to and holding prey
b. injecting paralytic toxins
c. entangling prey
d. all of the above
6. Where you would expect to find these cells (fill in all that apply).
gastrovascular cavity
c. basal disk
a. tentacles b.
7. Compare the oral and aboral surface. How do they differ?
a. oral has the mouth and anus
b. aboral has the mouth and anus
mouth and aboral has the anus
c. oral the
8. How do sea anemones prevent their prey from escaping their gastrovascular cavity (pick only
the best answer)?
a. mesenteries b. cnidocytes
c. basal disk
d. siphonoglyph
9. The gastrovascular cavity and its membrane mesenteries are lined with cilia. How might
they aid digestion?
a. paralyze prey
b. allow for movement on the ocean floor
c. increase
circulation and mixing
10. How did mesenteries within the increase the amount of nematocysts, enzyme secreting
gland cells, and absorptive
cells lining the gastrovascular cavity so that it can digest more efficiently?
a. increases osmotic pressure
b. increases hydraulic pressure c. increases surface area
11. If you remember, members of phyla porifera lacked tissues (groups of cells working
together in order to perform a certain task). Would you consider the gastroderm of cnidarians a
tissue and why?
a. yes, because all the absorptive, stinging, and digestive enzyme secreting cells work
together to digest food in the gut
b. no, their body is made up of all the same type of cell and digestion is intracellular (within
individual cells).
12. The gastrovascular cavity contains long fibers called anocotia. What is the importance of
these structures within the gastrovascular cavity?
a. defense against predators or competitors
b. entangling prey
c. both
13. Sea anemones do not have an anus. Develop a hypothesis for waste removal in sea
anemone.
a. diffusion
b. out the mouth
c. both
14. Cnidarians are diploblastic (only have 2 cell layers). Which is the best advantageous?
a. all of their cells come in contact with the water for diffusion
b. they lack a brain and only have nerve network
15. Which of the following is not a job of amebocytes living within the mesoglea (jelly within
these two layers)?
a. finish digestion
b. transport materials between the two cell layers
c. fight infection d. act as nerve cells
16. Speculate how small, molecular waste such as ammonia is removed from this organism?
a. diffusion
b. cilia
c. rhopalium
17. Why are the cilia in the siphonoglyph and lining of the gastrovascular cavity important?
a. increase surface area
b. circulate water for efficient diffusion
c. used to transport minerals
18. The skeleton of cnidarians is:
of calcium d. made of chiton
d. hold prey
a. made of silica
b. made of water
c. made
19. Speculate the purpose for the holes (called stomata) located near the oral disk.
a. diffusion
b. refill skeleton
c. obtaining nutrients
d. holding stinging
cells
20. How is the skeleton manipulated in order to bend or collapse when in danger (fill in all that
apply)?
a. muscles
b. cilia speed and direction
c. amount of hydraulic pressure
d. amebocytes
21. Which of the following is not a method of movement in sea anemone:
a. inflating and floating
b. sliding on basal disk c. jointed appendages
d. riding animals
22. What would cnidarians have to modify to live on land?
a. their skeleton
b. their method of breathing
c. their method of urinating
d. method of transport
e. all of the above
23. How might the simple nerve net of sea anemones be used in obtaining food (fill in all that
apply)?
a. coordinate movement towards the prey
b. distinguish which type of food should be selected
c. determine where the prey is
24. How is a nerve net advantageous (beneficial) if you have radial symmetry opposed to
bilateral symmetry)?
a. because they protect their head/brain region and move it in the forward direction they are
sensing
b. because you can sense and move in all directions equally
25. How do moon jellies capture food (unlike sea anemone)?
a. sticks to the mucus on their underside and the jelly
b. stimulation of zooplankton activate the osmotic reaction triggering the stinging cells to
sting the prey
26. Explain the process used by moon jellyfish to transport the food to their mouth (oral cavity)?
a. muscle contractions produce a wave to move food and mucus to the mouth
b. feeding arms and cilia direct food through groves to the mouth
27. What do the rhopalium (which are located on the edges of the moon jelly) do (fill in all that
apply)?
a. taste and smell chemicals in the water
b. balance c. sound vibrations d. light
28. If you were scuba diving with magnifying goggles you might see an organism called an
entoprocta. This specimen “A”, has a stalk that is attached to the surface with a pedal disk with
adhesive gland. This organism also has a body shaped like a cup with ciliated tentacles. It is a
filter feeder, with a mouth and an anus, but contains no blood. The entire organism is contained
within an exoskeleton of chitin. Analyze this organism and state your reasons for whether or
not it would belong to the cnidarian phylum. What additional information is not needed to
determine if it belongs to the cnidarian phyla:
a. does it have an anus
b. does it have stinging cells
c. does it use diffusion
29. One day while you were snorkeling in your neighbor’s saltwater aquarium you observed a
baby, organism. You lovingly name the organism “B”. You thoroughly study the organism
with a pocket dissecting kit and waterproof stereomicroscope that you never leave home
without. You observe that the organism is a free-floating, circular mass with tentacles. It is
mostly composed of water. You also notice that it contains mesoglea, comb rows, sticky
colloblast cells on its tentacles, and a gastrovascular cavity with an extremely small anus in
addition to the mouth. Would you classify this organism as a cnidarian? Why or why not?
a. yes, it has cilia
b. yes, it has mesoglea
c. no, it lacks stinging cells
d. no, it has an anus and so do you 
30. Once you began swimming again you ran into another organism. You decide to name this
organism “C” and begin studying its features. You learn that this organism is diploblastic,
round, free floating, and contains a gastrovascular cavity. Between the two cell-layers is a
considerable amount of water and mesoglea. When you observe its tentacles under
magnification you are able to identify thousands of tiny nematocysts heading towards your
finger. In addition to these structures you observe tiny zooxanthellae living within its cells.
Next, you look for an anus, but you can only find a large mouth on its underside this is covered
with mucous and cilia. Is organism “B” a cnidarian? Why or why not?
a. yes, it has stinging cells
b. yes, it has no anus
c. no, it has zooxanthellae
d. no, it is diploblastic
31. For some strange reason you start to feel a little ill, so you decide to stand on the reef below.
Within seconds you discover a stinging sensation coming from your feet. You dive down for a
closer look and find thousands of tiny polyps attached to a calcium carbonate skeleton. These
polyps have tentacles lined with nematocysts and a gastrovascular cavity. This organism is also
diploblastic and contains mesenteries lined with cnidocytes. In addition to the microscopic
cnidocytes you observe some zooxanthellae living within the epidermis. It is safe to assume
that there is only one opening to this little creature? Does this organism, which you named “D”,
belong to the cnidarian phylum? Why or why not?
a. yes, stinging cells
b. yes, they have a polyp form
c. no, they live as a colony
d. no, their skeleton is calcium carbonate
32. When you finish examining organism “D” you see another organism attached to the calcium
reef. You name this newer organism “E”. This organism is also in the polyp form. It has a cup
shaped body. Around the mouth of the cup are tiny cilia, covered tentacles. The tentacles
collect particles in the water and the cilia direct the food to the mouth. The food enters into a
small stomach and a tiny anus. Is organism E a cnidarian? Why or why not?
a. yes, it has
cilia
b. no, it lacks stinging cells
33. Evaluate organisms “A-D” by analyzing the similarities and differences among their
characteristics of organisms “A-D”. Rank the organisms in order from left to right starting with
the organism that is most closely related to the sea anemone. Defend your reasoning.
a. organisms C and D are the same phyla and then B, E, and then A
a. organisms B, C, D, and E are all the same phyla, but A is not