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AST 111 Chapter 24 Exam 3 Summer 2017

Terms in this set (44)

Why are fossils of early life on Earth more rare than fossils of plants and animals from the past few hundred million years?
Early organisms lacked skeletons and other hard structures that are most likely to be fossilized.
Which of the following best describes natural selection?
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.
Which of the following is not key evidence in support of the idea that all life today shares a common ancestor?
We have identified fossils of the first life forms that ever existed on Earth.
Which of the following best describes the predominant scientific view of the origin of life on Earth?
We may never know precisely how life arose, but current evidence suggests that life probably can arise naturally under the conditions that prevailed on the early Earth.
According to current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?
Oxygen was removed from the atmosphere by chemical reactions with surface rocks as quickly as it was released by life.
When we analyze whether a world is a possible home to life, the key thing we look for is _________.
the past or present existence of liquid water
Which of the following best describes the current status of the debate over evidence for life in the Martian meteorite ALH84001?
Most scientists find the evidence intriguing but suspect that it can be explained without requiring past life on Mars.
Why is Europa considered a good candidate for the possible existence of life?
Strong evidence suggests that it has a deep, subsurface ocean of liquid water.
In general, how does the size and location of a star's habitable zone depend on the star's mass?
The smaller (less massive) the star, the smaller and the closer-in the habitable zone.
We 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 _________.
examining spectral lines from the atmospheres of distant planets
Suppose that Jupiter had never existed, and there was no planet in our solar system between Mars and Saturn. How would we expect this to have affected Earth?
Earth would have been hit by many more comet impacts.
Which of the following best describes how the Drake equation is useful?
It helps us understand what we need to know in order to determine the likelihood of finding other civilizations.
In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), we expect the term fciv to be small if _______.
primitive life is common but intelligent life is rare
Suppose it turns out that one 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 _________.
100,000
Which of the following describes a major danger of interstellar travel at near-light speed?
Atoms and ions in interstellar space will hit a fast-moving spacecraft like a flood of dangerous cosmic rays.
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