According to fossil evidence how far back in time did life on Earth exist?
answer
About 3.5 billion years or more.
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Why do scientists say that evolution is a "theory"?
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Because it explains a great deal about life and is supported by an enormous body of evidence.
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What is a mutation?
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A change in a living cell's DNA
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Based on DNA studies, it seems that all life on Earth _________.
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shares a common ancestor
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Which of the following is considered by biologists to be a likely place where life first arose on Earth?
answer
In hot water near undersea volcanoes
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How did oxygen (O2) get into Earth's atmosphere?
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It was released by life through the process of photosynthesis
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Which of the following is NOT considered crucial for life to exist on some world?
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Liquid water
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Which of the following best describes what we mean by a habitable world?
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A planet or moon that could support life, if any life happened to be on it
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Which of the following places is NOT generally considered a potential home for life in our solar system?
answer
Jupiter's atmosphere
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The Sun's habitable zone _________.
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extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars
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Why don't we expect to find life on planets orbiting high-mass stars?
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The lifetime of a high-mass star is too short.
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Looking for an Earth-size planet around a nearby star (besides the Sun) is like looking for a pinhead located _________.
answer
thousands of kilometers away
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The "rare Earth hypothesis" holds that Earth-like planets are probably quite rare. Which of the following statements best sums up the current status of the debate over this hypothesis?
answer
We do not have enough data to settle the debate, because counterarguments can be made for each argument suggesting Earth-like planets may be rare.
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At present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?
answer
By using radio telescopes to search for signals from extraterrestrial civilizations
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In the equation Number of Civilizations = NHP x flife x fciv x fnow, what do we mean by fnow?
answer
We mean the fraction of planets with civilizations at the present time (as opposed to only in the past or future).
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We have sent four spacecraft on trajectories that will take them into interstellar space (Pioneer 10 and 11 and Voyage 1 and 2). How long will it take these spacecraft to travel as far as the nearest stars?
answer
Tens of thousands of years
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Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will _________.
answer
age less than people who stay behind on Earth
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If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?
answer
They are far more technologically advanced than we are
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The idea that life evolves through time was first suggested in ancient Greece, and it was favored by at least some scientists of the 18th and 19th centuries even before Charles Darwin proposed the theory of evolution. What is the key observational evidence that supports the idea that life on Earth has evolved through time
answer
The fossil record, revealed in geological layers of different ages, shows that life on Earth has become more complex over time.
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Given that the fossil record provides the key evidence for evolution, what is the importance of Darwin's theory of evolution?
answer
It represents our understanding of the process by which evolution occurs.
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Which of the following statements represent successful tests of the theory of evolution by natural selection?
answer
Species often show unique adaptations that are suited to the specific environment in which they live and might be detrimental in other environments, genetic comparisions show that the dna of closely related species is more similar than that of more distantlly related species, over time baceteria tend to resist antibiotic drugs.
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Earth was born about 4.5 billion years ago. According to current estimates, approximately how long after Earth's formation did the Moon form?
answer
a few tens of millions of years later.
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The oldest fossil evidence of life dates to about __________ ago.
answer
3.5 to 4 billion years
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Dinosaurs went extinct, probably because of an impact, about __________ ago.
answer
65 million years
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Fossil evidence suggests that life on Earth arose
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within a few hundred million years after Earth formed.
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Plants and animals are
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just two small branches of the diverse "tree of life" on Earth.
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Which of the following is a reason why early living organisms on Earth could not have survived on the surface?
answer
the lack of an ozone layer
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Which of the following worlds is not considered a candidate for harboring life?
answer
the Moon
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Rank the stars based on the distances to their habitable zones (from the central star), from shortest to longest.
answer
barnards star, 61 cygni, Alpha centauri, sirius, spica. (larger M the largest distance) also same order for width of habitable zones and surface temp.
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As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________.
answer
increases / increases
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Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case?
answer
Only Mercury would be in the Sun's habitable zone
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Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?
answer
The expected lifetime of a massive star is too short to allow for the evolution of complex life
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How does the habitable zone around a star of spectral type G compare to that around a star of spectral type M?
answer
It is larger.
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highmass main sequence stars have amore distant and wider ___ than low mass
answer
habitable zone
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sky surverys looking for radio signals are part of
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search for extraterrestrial intelligence
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the ____ is designed as a way of estimatting the number of intelligen civilizations
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drake equation
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the notion that living organisms with advantages that give them greater reproductive success will survice while others perish
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natural selection
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living organisms are able to produce far more offspring than their environment can support
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theory of evolution
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the different time perios of the ___ are defined by changes in fossils found from those time periods
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geological time scale
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In the Drake equation, suppose that the term f life =1 2 . What would this mean?
answer
Half of the habitable worlds in the galaxy actually have life, while the other half don't.
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