CH 19

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According to fossil evidence how far back in time did life on Earth exist?
A) About 2.0 billion years.
B) About 65 million years.
C) About 545 million years.
D) About 3.5 billion years or more.
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Terms in this set (35)
Why do scientists say that evolution is a "theory"?
A) Because they are not very confident that it really happened.
B) Because it is supported by only a small amount of evidence.
C) Because it's really just a guess about how life developed on Earth.
D) Because it explains a great deal about life and is supported by an enormous body of evidence.
Which of the following best describes what we mean by a habitable world?
A) a planet or moon that lies within its star's habitable zone
B) a planet or moon that could support life, if any life happened to be on it
C) a planet or moon with life
D) a planet or moon on which humans could survive if we happened to go there
The Sun's habitable zone
A) extends from just beyond the orbit of Mercury to just beyond Earth's orbit.
B) extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars.
C) consists only of Earth, since Earth is the only planet known to be inhabited.
D) extends from the orbit of Earth to the orbit of Jupiter.
Why don't we expect to find life on planets orbiting high-mass stars? A) They emit too much ultraviolet radiation. B) Planets cannot have stable orbits around high-mass stars. C) They are too hot to allow for life. D) Their lifetimes are too short.DLooking for an Earth-size planet around a nearby star (besides the Sun) is like looking for a pinhead located A) across the length of a football field. B) across the street. C) thousands of kilometers away. D) a few hundred kilometers away.CThe "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? A) 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. B) It is no longer discussed, because as part of its broad cover-up of UFOs, the United States government has classified all the material relating to this debate as Top Secret. C) The debate raged for a while, but is now settled. We are now quite certain that Earth-like planets are rare. D) The debate raged for a while, but is now settled. We are now quite certain that Earth-like planets are common.AAt present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out? A) by using radio telescopes to search for signals from extraterrestrial civilizations B) by seeking access to the secret records and alien corpses kept at the military's Area 51 in Nevada C) by using X-ray telescopes to search for exhaust from interstellar spacecraft D) by analyzing high-resolution images of nearby stars in search of evidence for structures that could not have developed naturally E) by searching for planets around distant starsAIn the equation Number of Civilizations = NHP × flife × fciv × f now, what do we mean by fnow? A) We mean the fraction of planets in the galaxy on which a civilization could theoretically develop right now. B) We mean the fraction of civilizations in the universe that currently are sending messages to us. C) We mean the fraction of all species ever to exist that we currently are aware of. D) We mean the fraction of planets with civilizations at the present time (as opposed to only in the past or future).DWe 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? A) Several decades. B) Never, because they will rust and fall apart. C) Hundreds of years. D) Tens of thousands of years.DEinstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will A) age less than people who stay behind on Earth. B) have more fun than people who stay behind on Earth. C) never be able to make the trip within their lifetimes. D) age more than people who stay behind on Earth.AIf there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true? A) They are far more technologically advanced than we are. B) For fun, they enjoy "buzzing" to Earth and temporarily abducting people, showing a clear preference for people located in less-developed rural areas. C) They are anatomically much like us, with two arms, two legs, two eyes, and two ears. D) They have social structures that are completely different from our own—for example, different types of "family" units, and so on.AWhy are fossils of early life on Earth more rare than fossils of plants and animals from the past few hundred million years? A) We find fossils in sedimentary layers, and no sediments were deposited until just a few hundred million years ago. B) Fossils could not form before there was oxygen in the atmosphere. C) Early organisms lacked skeletons and other hard structures that are most likely to be fossilized. D) Life was far less abundant prior to a few hundred million years ago.CWhich of the following best describes natural selection? A) It is a guess made by scientists about how life develops, but it has no hard evidence to support it. B) It is the idea that organisms with genetic traits that improve their ability to reproduce are more likely to pass those traits on to future generations. C) It is the idea that organisms naturally increase in complexity and intelligence with time. D) It is the idea that the strong survive and the weak die off.BWhich of the following is NOT key evidence in support of the idea that all life today shares a common ancestor? A) Mapping of gene sequences shows how life is all related. B) All life builds proteins from the same amino acids and uses ATP to store energy in cells. C) We have identified fossils of the first life forms that ever existed on Earth. D) All life uses DNA and the same genetic code.CWhich of the following best describes the predominant scientific view of the origin of life on Earth? A) We can describe with great certainty the precise steps by which life arose on Earth. B) Life arose through a series of extremely unlikely chemical coincidences, making it seem almost miraculous that life ever came to exist at all. C) Life probably migrated to Earth from some other world. D) We may never know precisely how life arose on Earth, but current knowledge suggests that life likely arose easily under the conditions that prevailed on the early Earth.DWhy didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth? A) Early forms of animal life consumed the oxygen released by plants during the first billion years of life on Earth. B) Oxygen released by life was removed from the atmosphere by chemical reactions with surface rocks until the surface rock could absorb no more. C) Oxygen released by life was removed from the atmosphere by dissolving in the ocean until the oceans could dissolve no more. D) Early life did not release oxygen, and oxygen releasing organisms didn't evolve for a billion years after the earliest life.BWhen we analyze whether a world is a possible home to life, the key thing we look for is A) evidence of atmospheric oxygen. B) the past or present existence of liquid water. C) surface coloration changes that could indicate vegetative growth. D) the presence of organic molecules such as amino acids.BWhich of the following best describes the current status of the debate over evidence for life in the Martian meteorite ALH84001? A) Most scientists find the evidence intriguing but suspect that it can be explained without requiring past life on Mars. B) All scientists now agree that the meteorite shows clear evidence of past life on Mars. C) Most scientists agree that the evidence would support life if the meteorite truly comes from Mars, but very few scientists accept that the meteorite is from Mars and instead think it may be an ordinary Earth rock. D) All scientists now agree that the meteorite shows no evidence for past life on Mars.AWhy is Europa considered a good candidate for the possible existence of life? A) Strong evidence suggests that it has a deep, subsurface ocean of liquid water. B) It has a thick atmosphere with a surface pressure greater than that on Earth. C) It is located within our Sun's habitable zone. D) The Galileo spacecraft found strange seasonal changes on its surface that look like they could be due to life.AIn general, how does the size and location of a star's habitable zone depend on the star's mass? A) The smaller (less massive) the star, the larger and the closer-in the habitable zone. B) The smaller (less massive) the star, the larger and the farther-out the habitable zone. C) The habitable zone is always about the same size, but its location moves inward for smaller stars. D) The smaller (less massive) the star, the smaller and the closer-in the habitable zone.DWe are not yet capable of detecting life on planets around other stars. But as our technology develops, our first real chance of detecting such life will probably come from A) examining spectral lines from the atmospheres of distant planets. B) sending spacecraft to study the planets up close. C) determining the orbital properties of the planets. D) examining high-resolution images of the planets made by orbiting telescopes.ASuppose that Jupiter had never existed, and there was no planet in our solar system A) between Mars and Saturn. How would we expect this to have affected Earth? B) There would not have been any effect, since Jupiter is in the outer solar system and Earth is in the inner solar system. C) Earth would have been hit by many more comet impacts. D) There would be no water on Earth. E) Earth's orbit would have been unstable, and our planet would have spiraled into the Sun.BWhich of the following best describes how the Drake equation is useful? A) The Drake equation tells us what wavelengths of light will be most useful to examine in the search for extraterrestrial intelligence. B) The Drake equation allows us to calculate the masses of planets orbiting other stars. C) The Drake equation has allowed us to determine the number of civilizations in the Milky Way Galaxy. D) The Drake equation helps us understand what we need to know in order to determine the likelihood of finding other civilizations.DIn the equation Number of Civilizations = NHP × flife × f civ × f now, we expect the term f civ to be small if: A) most of the civilizations that have ever existed are still out and about in the galaxy. B) most civilizations destroy themselves within just a few hundred years of arising. C) most habitable planets never actually get life on them. D) primitive life is common but intelligent life is rare.DSuppose it turns out that 1 in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to A) 400,000. B) 40,000. C) 4,000. D) 400. E) 40.AWhich of the following describes a major danger of interstellar travel at near-light speed? A) Time dilation will slow the heart beats of the crew to a dangerously low rate. B) Asteroid fields floating in interstellar space will present a navigational challenge. C) Any interstellar journey will take much longer than the lives of the crew members. D) Atoms and ions in interstellar space will hit a fast-moving spacecraft like a flood of dangerous cosmic rays.DWhich of the following statements about matter-antimatter engines is not true? A) Matter-antimatter reactions represent the most efficient possible reactions in terms of energy release. B) One of the major challenges to developing matter-antimatter engines is finding a way to store antimatter after it is produced. C) Matter-antimatter engines would be great in theory, but to date we have no evidence that antimatter even exists. D) Spacecraft powered by matter-antimatter engines could probably reach speeds of more than half the speed of light.CWhich of the following is not considered a potential solution to the question of why we lack any evidence of a galactic civilization? A) The galactic civilization is deliberately avoiding contact with us. B) There is no galactic civilization because all civilizations destroy themselves before they achieve the ability to colonize the galaxy. C) The galactic civilization probably is undetectable because they operate under different laws of physics from the ones we know. D) There is no galactic civilization because we are the first species ever to achieve the ability to study the universe.C