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Answers to Text Questions
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Inquiry Questions
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Self Test

1). Which of the following is necessary and sufficient for life?
    a). complexity
    b). heredity
    c). growth
    d). all of these
Answer: b

2). Which of the following most accurately describes the origins of life on earth?
    a). Special creation: Life-forms were put on earth by supernatural or divine forces.
    b). Extraterrestrial origin: The earth may have been infected by life from another planet.
    c). Spontaneous origin: Life evolved from inanimate matter to increasing levels of complexity.
    d). None of these are accurate.
Answer: d

3). Which of the following proposals assumes that the earth had a reducing atmosphere low in oxygen?
    a). Life evolved deep in the earth's crust.
    b). Life evolved under frozen oceans.
    c). Life evolved at the ocean's edge.
    d). Life evolved at deep-sea vents.
Answer: c

4). Scientists have created synthetic nucleotide-like molecules in the laboratory that are able to replicate. This seems to support which hypothesis of chemical evolution?
    a). an RNA-first hypothesis
    b). a protein-first hypothesis
    c). a peptide-nucleic acid first hypothesis
    d). All of the hypotheses are supported by these results.
Answer: a

5). A key link needed between bubbles and cells is
    a). that they needed a hereditary molecule.
    b). that they needed to grow and bud off new bubbles.
    c). that they needed to incorporate enzymes.
    d). that they needed to form spontaneously.
Answer: a

6). Prokaryotes were the only life-form on the earth
    a). for about 1.5 billion years.
    b). for about 1 billion years.
    c). for about 2.5 billion years.
    d). for more than 2.5 billion years.
Answer: b

7). The first organisms may have been a type of archaebacteria similar to present day organisms called
    a). extreme halophiles.
    b). prokaryotes.
    c). extreme thermophiles.
    d). eubacteria.
Answer: c

8). The infolding of outer membrane seen in prokaryotes is believed to have given rise to which of the following?
    a). mitochondrion
    b). chloroplast
    c). endoplasmic reticulum
    d). all of these structures
Answer: c

9). All organisms fall into one of ________ domains that include _____ kingdoms.
    a). six/three
    b). six/six
    c). three/three
    d). three/six
Answer: d

10). Which of the following statements is false.
    a). Life may have evolved on Mars.
    b). In order for life to evolve anywhere, carbon is required.
    c). A large ocean exists under the icy surface of Europa.
    d). It is possible that life may have evolved on some other planet.
Answer: b


Test Your Visual Understanding

1). Match the following descriptions with the appropriate numbered step in the figure that explains a bubble hypothesis.

a). Bombarded by the sun's ultraviolet radiation, lightning, and other energy sources, the simple organic molecules released from the bubbles reacted to form more complex organic molecules.
b). Volcanoes erupted under the sea, releasing gases enclosed in bubbles.
c). The more complex organic molecules fell back into the sea in raindrops. There, they could be enclosed in bubbles and begin the process again.
d). When the bubbles persisted long enough to rise to the surface, they popped, releasing their contents to the air.
e). The gases, concentrated inside the bubbles, reacted to produce simple organic molecules.
Answer:
1–b
2–e
3–d
4–a
5–c

Apply Your Knowledge

1). In Fred Hoyle's science fiction novel, The Black Cloud, the earth is approached by a large interstellar cloud of gas that orients itself around the sun. Scientists soon discover that the cloud is feeding on the sun, absorbing the sun's energy through the excitation of electrons in the outer energy levels of cloud molecules, in a process similar to the photosynthesis that occurs on earth. Different portions of the cloud are isolated from each other by associations of ions created by this excitation. Electron currents pass between these portions, much as they do on the surface of the human brain, endowing the cloud with self-awareness, memory, and the ability to think. Using electrical discharges, the cloud is able to communicate with humans and describe its history. It tells scientists that it originated as a small extrusion from an ancestral cloud, and that since then it has grown by the absorption of molecules and energy from stars like our sun, on which it has been feeding. Soon the cloud moves off in search of other stars. Is it alive?

Answer:
1). The cloud appears alive possessing several fundamental properties of life including internal organization (such as cellular organization), sensitivity, growth, regulation, and homeostasis. However, a key property of life that the cloud does not seem to possess is that of heredity. Although the cloud grows, it does not seem capable of reproducing offspring that carry characteristics passed on from the parent. Without this key characteristic, the cloud would not be considered alive.







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