Textbook Question
One of the characteristics unique to animals is
a. Gastrulation
b. Multicellularity
c. Sexual reproduction
d. Flagellated sperm
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One of the characteristics unique to animals is
a. Gastrulation
b. Multicellularity
c. Sexual reproduction
d. Flagellated sperm
The distinction between sponges and other animal phyla is based mainly on the absence versus the presence of
a. A body cavity
b. A complete digestive tract
c. Mesoderm
d. Tissues
Which of the following was probably the least important factor in bringing about the Cambrian explosion?
a. The emergence of predator-prey relationships
b. An increase in the concentration of atmospheric oxygen
c. The movement of animals onto land
d. The origin of Hox genes