1.
A scientific theory is a set of propositions that defines and explains some aspect of the world. This definition contrasts sharply with the everyday English usage of the word theory, which often carries meanings like "speculation" or "guess." Explain the difference in the two definitions, using the cell theory and the theory of evolution by natural selection as examples.
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2.
Turn back to the tree of life shown in Figure 1.8. Note that Bacteria and Archaea are prokaryotes, while Eukarya are eukaryotes. Draw an arrow on the tree that points to the branch where the structure called the nucleus originated. Explain your reasoning.
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3.
The proponents of the cell theory could not "prove" that it was correct in the sense of providing incontrovertible evidence that all organisms are made up of cells. They could only state that all organisms examined to date were made of cells. Why was it reasonable for them to conclude that the theory was valid?
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4.
How do the tree of life and the taxonomic categories created by Linnaeus (kingdom, phylum, class, order, family, genus, and species) relate to one another?
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5.
Review Pasteur’s experiment. Suppose a proponent of the spontaneous generation hypothesis criticized the results by claiming that life would appear in the swan-necked flask eventually. According to this view, Pasteur did not allow enough time to pass before reaching the conclusion that life does not originate spontaneously. Respond to this critic.
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6.
Suppose a friend takes issue with the section of the chapter on why giraffes have long necks. This friend claims that the food competition hypothesis and the sexual selection hypothesis are not mutually exclusive—that both could be true. Comment.
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7.
Erick Greene is still doing research on the behavior of Zonosemata flies. Write down three questions about their courtship or anti-predator behavior that you would like to see answered.
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