chapter 1 bio answers - Biological Science, 3e Answers to...

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Sheet1 Page 1 Biological Science, 3e Answers to Questions Chapter 1: Biology and the Tree of Life 1.1 The Cell Theory PracticeIt (page 4) If you understand this concept, you should be able to identify problems that would have arisen if he had put different types of broth in the two treatments, heated them for different lengths of time, or used a ceramic flask for one treatment and a glass flask for the other. ANSWER: If Pasteur had done any of the things listed above, he would have had more than one variable in his experiment. His main variable was the shape of the flask neck: a straight neck, which allowed entry of preexisting cells, such as bacteria and fungi, from the air, versus a swan neck, which limited the entry of preexisting cells. If he had used different types of broth, heated them for different amounts of time, or used ceramic for one flask and glass for the other, he would not have been able to conclude that any observed differences in growth were due to the fact that one flask prevented bacteria from falling into the broth. Using different types of broths might have limited bacterial growth in one flask simply because of differences in nutrient availability. Heating the flasks for different lengths of time might have sterilized one flask, but not the other. Using ceramic for one flask might have allowed bacteria to enter the flask through the porous ceramic material. 1.2 The Theory of Evolution by Natural Selection PracticeIt (page 5) If you understand this concept, you should be able to graph how average stem height will change over time in a population that occupies a windy environment versus a non-windy environment, where tall plants have an advantage due to better access to light. ANSWER: Chapter 1 Answers pg. 1 Check Your Understanding (page 6) If you understand that . . . h Natural selection occurs when heritable variation in certain traits leads to improved success in reproduction. Because individuals with these traits produce many offspring with the same traits, these traits increase in frequency and evolution occurs. h Evolution is simply a change in the characteristics of a population over time. You should be able to . . . Explain why each of the following common misconceptions about evolution by natural selection are incorrect, using the example of selection on the height of wheat stalks. 1) evolution is progressive, meaning that species always get larger, more complex, or better in some
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Sheet1 Page 2 sense 2) individuals as well as populations change when natural selection occurs 3) individuals with high levels of fitness are stronger or bigger or more dominant. ANSWER: 1) In a windy location, the percentage of short plants in a wheat population will increase over time because short plant are more likely than tall plants to survive wind damage and to reproduce more often. However, short plants are in no way more complex or
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chapter 1 bio answers - Biological Science, 3e Answers to...

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