Lewis/Life - Answers to End-of-Chapter Questions

Chapter 26 - Answers to End-of-Chapter Questions

TO REVIEW

1 a. Cell wall
b. Cleavage patterns; Oral or aboral end forming first
c. Mammary glands, hair
d. More erect posture, reduced eyebrow ridges, lighter jaws, smaller front teeth, increased thumb use, shorter arms, complex speech, and greater intelligence (?!).

2 a. Radial -- symmetrical in any direction
Bilateral -- two mirror images
Pentaradial -- five identical "pie slices"
b. Direct development -- young look like adults
Metamorphosis -- maturation includes change in form.
c. Spiral cleavage -- In cell division, cells stack in the form of a spiral.
Radial cleavage -- In cell division, cells stack directly on top of one another.
d. Determinate -- The fate of the cells is determined. If the cell is missing, abnormality or death occurs.
Indeterminate -- The fate of the cells is not determined. A missing cell can be replaced.
e. Biramous -- two lobes; uniramous -- one lobe
f. Diploblastic -- two germ layers
Triploblastic -- three germ layers
g. Deposit feeding -- taking in soil or sediment with nutrients
Suspension feeding -- taking food particles from a suspension (as water)
h. Coelomate -- having a fluid-filled cavity surrounding the gut
Acoelomate -- lacking a coelom
Pseudocoelomate -- have a body cavity that is not lined with mesoderm
i. Vertebrate -- having a vertebral column
Invertebrate -- not having a vertebral column

3 a. Any cnidarian
b. Any platyhelminth
c. Any poriferan

4 a. Any sponge
b. Any nematode
c. Any arthropods

5. Check the text.

6. Platyhelminthes

7. Answers will vary.

8. Cephalization is the formation of the central brain. Metamerism is the formation of segments.

9. Answers will vary.

10. Coelom

11. Organisms given here. Check text for description of structure's function.
a. Tape worm
b. Sponge
c. Echinoderm
d. Platyhelminth
e. Portuguese man-of-war
f. Mollusk
g. Echinoderm (though some observant student might argue that ossicles are also inner ear bones for the vertebrata)
h. Tunicate
i. Annelid
j. Lancelet
k. Mollusk
l. Annelid
m. Arthropod
n. Fluke
o. Tapeworm

12. All are mammals.
Monotremes lay eggs.
Marsupials are pouched.
Placentals nourish unborn through a placenta.

TO THINK ABOUT

1. Biologically, humans are animals.

2. Deuterostome. Indeterminate cleavage.

3. The baby would die or be born abnormal.

4. Answers will vary.

5. Echinodermata. Embryological studies (Molecular studies would also be correct.)

6. Body plan. Platyhelminthes are flat. Nematodes are round and unsegmented. Annelids are round and segmented.

7. The clams and squid are mollusks. The swordfish is a chordate. (The question asks for phylum here; vertebrate would be incorrect for swordfish because vertebrata is a subphylum.)

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