Midterm1 - This examination consists of nine multiple...

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Unformatted text preview: This examination consists of nine multiple choice questions, nine short answer questions, and three short essay questions (from which you are to pick one to answer), and is due at the beginning of class on Monday, 5 October. Once you have completed studying for the exam, you are free to look at the questions at any time, and are encouraged to do so well prior to writing your answers so as to give yourself time to think about them. While thinking about the questions, please do not consult your notes or textbook or talk with others about them. The examination is designed to take an hour to write your answers, and you should gauge the appropriate length of answers accordingly. You may, however, take up to two hours to actually write the answers, to assure that you don't feel pressed for time. Whether you are entirely confident with your answers to any given question or not, be sure to do the best job you can with each question. Answers to multiple choice and short answer questions should be provided on the exam itself and in the space provided. Please be legible and put your name on the top of each page. Your essay may be written legibly in the space provided or may be typed and attached to the exam. In either case, be sure to indicate which question you are responding to and write no more than one page. Multiple choice (2 points each). Put the letter corresponding to the best answer in the space provided to the left (answers in boldface). 1. Characterizing a living organism as a "highly improbable assembly of physical elements (atoms)" means that A) repeated random mixing of the atoms of which an organism is made would rarely yield a living organism; B) there must be something in a living organism other than atoms; C) a blueprint, plan, or set of instructions for that particular assembly must have existed before it did; D) it is very unlikely that life exists elsewhere in the universe. 2. If one equates the history of the earth with a twenty-four hour day, the appearance of life on the earth, of eukaryotic cells, of multicellular organisms, and of a diversity of mammals A) occur at roughly equal intervals of time beginning early in the morning; B) occur at roughly equal intervals of time beginning in the late afternoon; C) occur at progressively shorter intervals of time with a diversity of mammals appearing around noon; D) occur at progressively shorter intervals of time with a diversity of mammals appearing late in the evening. 3. From one end of a human to another corresponds roughly to how many bacteria and how many atoms? A) one million and ten billion; B) one hundred million and one hundred billion; C) one thousand and ten thousand; D) one hundred and one thousand. 4. Fungi are A) prokaryotes; B) heterotrophs; C) autotrophs; D) plants. 5. The cells of multicellular organisms are A) prokaryotic; B) eukaryotic; C) both prokaryotic and eukaryotic; D) neither prokaryotic nor eukaryotic. 6. The oxygen atom has eight protons. How many electrons does it have? A) eight; B) four; C) sixteen; D) the same number as it has neutrons. 7. Which of the following atoms are found exclusively in living organisms? A) helium; B) oxygen; C) carbon; D) none of the preceding. 8. Which of the following most avidly grabs electrons? A) helium; B) oxygen; C) carbon; D) sodium. 9. Which of the following is not a polar molecule? A) methane; B) water; C) ethanol; D) none of the preceding. Short answer (3 points each). Four sentences or fewer. Write legibly in the space provided (sample answers in boldface). 10. Briefly explain why a scientific hypothesis cannot be proven to be true. 11. In what sense is a living organism similar to a scientific hypothesis? Both represent summaries of prior observations and both are subject to further testing by new observations. 12. Briefly describe the major distinction between autotrophs and heterotrophs, giving an example of each. Autotrophs, such as plants, get energy from non-living things while heterotrophs, such as animals, get energy only from other living things 13. Describe at least one additional correlated difference between autotrophs and heterotrophs, and use this to illustrate the "clumpiness" of diversity by specifying some kind of organism that might exist but doesn't. Autotrophs generally have cell walls, while heterotrophs (with the exception of fungi) don't. The absence of conceivable autotrophs lacking cell walls is an example of clumpiness. 14. Bacteria appear earlier in the fossil record than do multicellular organisms. What evidence from the fossil record indicates that bacteria are not in any biological sense "inferior" to multicellular organsims? Bacteria persist to the present day, rather than disappearing with the appearance of multicellular organisms as they should if the latter were "superior". 15. An enormous diversity of forms apparently based on a much smaller number of building blocks is a fundamental characteristic of life. Using as a concrete example either atoms or molecules, explain how one can get a large number of different things from a small number of building blocks. Atoms are made up of only three building blocks: protons, neutrons, and electrons. Because the "assembly rules" specify only that the number of protons equals the number of electrons, they are many more than three possible atoms (atoms containing one of each, two of each, three of each, and so forth). 16. Many things which appear to be unchanging at the time and space scales familiar to humans are in fact undergoing continuous change when observed at other scales of space and time. Give an example of this, illustrating how recognition of not previously suspected change contributes to better understanding some aspect of biological systems. At very small spatial and temporal scales, it is apparent that water molecules are in continuous, random motion. This helps to explain how substances placed in water are mixed so as to contact each other for chemical reactions. 17. Describe a distinctive property of water, how it reflects internal organization of water molecules, and its importance for understanding biological systems. Because oxygen has a higher electron affinity than hydrogen, the water molecule is polar (has an unequal charge distribution). Water molecules therefore attract each other by hydrogen bonds and these weak bonds result in water having a relatively high heat capacity. Because of the latter, organisms are somewhat buffered against temperature changes. 18. Biological macromolecules are in general polymers. Name one class of biological macromolecule and the kind of monomer from which it is constructed, and briefly describe a role the macromolecule plays in biological systems. Proteins are made up of amino acids, and play an essential role as enzymes, catalysts for chemical reactions. Short essay (20 points). Pick one of the following three questions to answer, being sure to indicate which you are writing about. One page or less, written legibly in the space provided or typed and attached. A. Assume that life arose independently on some planet elsewhere in the uinverse. Write a brief essay in which you consider the likelihood that it would be similar or identical to life on earth, and discuss the reasons for your conclusions. B. "Autonomy" was one of a list of fundamental characteristics of living organisms discussed in class, but doesn't appear on a similar list in the textbook. Write a brief essay specifying what is meant by this characteristic and discussing why it ought or ought not to be included in such a list. C. Briefly describe what is meant by "life", in the context of discussing what aspects of life currently seem to you most understandable in terms of atoms and molecules, what aspects seem least understandable, and why. B. --- "Autonomy" is the property of being capable of change even when the surrounding environment is unchanging. A person moving from one place to another even though nothing changed in the surroundings is one example. Another, characteristic of all known organisms, from the simplest to the most complex, is the phenomenon of circadian periodicity, organismal changes of one or another kind on a regular cycle even in the absence of any environmental variation. More generally, autonomy is the property that changes in an organisms processes and behavior depend not only on external factors but on internal organization as well. "Autonomy" is one of the most striking characteristics of living organisms, perhaps so obvious that it is sometimes not included in lists of characteristics. It may also be left out because it is felt to imply that organisms aren't also dependent on one another, and on the environment, which they strikingly are. For this reason, it is best to speak of "semi-autonomy", acknowledging both interdependences and some degree of independence. A third reason why autonomy may not be included on most lists is that scientists (and others) like to be able to specify the "causes" of any changes, and appealing to something "inside" the organism may seem like a cop out, particularly if it can't be readily analyzed. This last point seems like the best reason to include autonomy as an explicit part of any list of characteristics of living organisms. If one fails to mention what is so obvious, people are unlikely to pay adequate attention to internal organization and hence unlikely to develop the experimental approaches and techniques which make internal organization effectively analyzable. ...
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