Name _________________________________________
Period ______
Date _________________
Chapter 32: An Introduction to Animal Diversity
Animals and plants come in a great variety of shapes - but not every shape. We don't see people
with three arms, elephants with one leg, or dogs with two mouths. Such organisms are
biologically possible, but they would be so inefficient (think of the one-legged elephant) that
Mother Nature never evolved them. The morphology (i.e. shape) of an organism has to be tuned
to the environment it lives in. That's where symmetry enters the picture.
Symmetrical objects are said to have a balanced and regular arrangement of parts. In biology,
there are several kinds of symmetry. The kind of symmetry an organism has tells us a great deal
about its life style and ecology.
Radial symmetry – the symmetry of a cylinder. There is a top and bottom, but the sides are
circular. Any cut through the center along the top-bottom axis divides the cylinder
into equal halves. Examples: some sponges, coral animals, jellyfish, and many plants.
These organisms are sessile (can't move), sedentary (don't move much), or float helplessly in the
water. Since they can't move by themselves, they look the same all around their sides. They
have a top and bottom (one of which has the mouth) but no left or right.
Bilateral symmetry – a single plane of symmetry extends from the anterior end (the head) to the
posterior end (the tail), running through the midline of the body. The two sides of the organism
are mirror halves. The great majority of animals have bilateral symmetry – worms, insects,
vertebrates.
1. Identify the kind of symmetry shown:
a) ____________________
b)_____________________
c)____________________
2. Which kind of symmetry do most animals (INCLUDING HUMANS) have? ______________
Mobile animals are nearly all bilaterally symmetrical. Movement – crawling, running,
swimming, or flying – is most efficient when the animal has paired legs, fins, or wings on its
sides. The nerves and muscles are easiest to coordinate in pairs. Bilateral symmetry and
locomotion go together.
What direction should an animal move in? The end that moves first into a new environment is
the head or anterior end. Bringing up the rear is the tail or posterior end. Since the anterior
end is the "exploratory" end, that is where the sense organs are – the organs of touch, sight,
hearing, smell, and taste. To control all that sensory machinery, the brain is also in the head
(if its brain was in its tail, an animal would never figure out what was going on).
Finally, an animal with a head and a tail will have a dorsal surface (the back) and a ventral
surface (the belly). Bilateral symmetry is part of a package. The rest of the package is the
anterior head with sensory structures and brain, a posterior tail, and both a dorsal and a
ventral surface.
3. USE WORDS FROM THE WORD BANK TO LABEL THE DIAGRAM:
ANTERIOR
POSTERIOR
DORSAL
VENTRAL
a)__________________
b)_______________
c)____________________
d) __________________
4. Does this organism show CEPHALIZATION? YES NO Explain your answer.
5. What type of SYMMETRY does this organism have? ________________________
6. Name the 3 germ layers found in most animal embryos.
________________________
________________________
________________________
7. From which of these three germ layers do MUSCLE cells form? ______________________
8. From which of these three germ layers does the skin form? _________________________
9. From which of these three germ layers does the nervous system form? __________________
10. From which of these three germ layers does the stomach & intestines form? _____________
11. Color the 3 kinds of COELOMS labeled below then answer the questions about coeloms.
(Endoderm =Yellow
ACOELOMATE
(NO space)
Mesoderm = red
Ectoderm = blue)
PSEUDOCOELOMATE
COELOM
“true coelom”
MATCH THE KIND OF COELOM ABOVE WITH ITS DESCRIPTION
Use A for ACOELOM
P for PSEUDOCOELOM
C for TRUE COELOM
12. _____ Has a body cavity with mesoderm lining the body wall but not around the gut
13. _____ Has endoderm, mesoderm, and ectoderm, but no body cavity (space)
14. _____ Has a body cavity lined on BOTH sides by mesoderm
15. _____ type of coelom found in flatworms (planaria)
16. _____ type of coelom found in segmented worms (annelids)
17. _____ type of coelom found in all animals higher than worms on the phylogenetic tree
18. _____ type of coelom found in nematodes (roundworms)
19. _____ type of coelom found in all vertebrates
MULTIPLE CHOICE: Circle ALL that are TRUE. There may be more than one right answer.
20. This cleavage pattern in which the future of each cell is decided later after the 4 cell stage and
cells “stack up” as they divide is called __________________ cleavage
A. indeterminate
B. determinate
C. radial
D. spiral
21. The pattern above is seen in _____________________ embryos.
A. protostome
B. deuterostome
22. This cleavage pattern in which the future of each cell is decided very early and cells twist as
they divide during embryonic development is called ___________ cleavage.
A. indeterminate
B. determinate
C. radial
D. spiral
23. The pattern above is seen in _____________________ embryos.
A. protostome
B. deuterostome
24. This hollow ball of cells produced when a zygote divides rapidly is called a _____________
A. blastula
B. blastopore
C. deuterostome
D. cladogram
25. The indented place shown at the right is called the ________________
A. blastula
B. blastopore
C. deuterostome
D. cladogram
26. Which body system will the blastopore become a part of?
A. excretory
B. integumentary
C. digestive
D. reproductive
27. In all protostome embryos, the blastopore will become the __________________.
A. mouth
B. anus
28. In all deuterostome embryos, the blastopore will become the ___________________.
A. mouth
B. anus
29. Whenever an animal's body lacks a specific form
A. Asymmetry
B. Radial symmetry
C. Bilateral symmetry
30. With this there is a center to the animal's body from which limbs or arms come out from
as if from a circle, much like the spokes on a bicycle wheel
A. Asymmetry
B. Radial symmetry
C. Bilateral symmetry
31. This means that an animal has two sides that are almost exactly the same on each side.
Thus if you drew a line down the middle of the animal's body, one side would be a mirror
image of the other side.
A. Asymmetry
B. Radial symmetry
C. Bilateral symmetry
32. If you remove cells from or split the blastula in an early _____________ embryo, the
resulting organism will be missing body parts and will not survive.
A. Protostome
B. Deuterostome
33. Animals in which the embryonic blastopore becomes the ANUS are called
____________________.
34. This organism shows ___________ symmetry.

35. The arrow is pointing to the _____________ surface of this
animal.
A. anterior
B. posterior
C. ventral
D. dorsal