Chapter 24 Life in the Universe – Flashcards
Unlock all answers in this set
Unlock answersquestion
The earliest evidence for life on Earth dates to
answer
about 3.8 billion years ago
question
Which living organisms most resemble the common ancestor of all life according to genetic testing?
answer
organisms living deep in the oceans around seafloor volcanic vents and in hot springs
question
When did oxygen begin to accumulate in the atmosphere?
answer
about 2 billion years ago
question
Which of the following statements about ozone (in Earth's stratosphere) is not true?
answer
The presence of ozone was crucial to the origin of life.
question
Why didn't oxygen begin to accumulate in the atmosphere until approximately 1.5 billion years after life appeared on Earth?
answer
Oxygen produced by life was removed from the atmosphere by oxidation reactions with surface rocks
question
Which of the following causes mutations in living organisms?
answer
ultraviolet light and toxic chemicals
question
What was the Cambrian explosion?
answer
a dramatic diversification of life that began about 540 million years ago
question
When did the extinction of the dinosaurs occur
answer
65 million years ago
question
What is absolutely necessary for living organisms to survive?
answer
energy
question
Where have scientists begun a concerted search for life outside of Earth?
answer
Mars
question
The only place outside of Earth where there is irrefutable evidence for (ancient, microbial) life is
answer
None of the above-there is no irrefutable evidence for life beyond Earth.
question
After Mars, the next most likely candidates for life in the solar system are
answer
the large moons of the jovian planets.
question
How does the Kepler mission plan to detect Earth-like planets around other stars?
answer
by observing the slight dip in brightness of the central star as the planet transits
question
Which of the following gases, which we might be able to detect in infrared spectra, would be a strong indicator of life on another planet?
answer
Ozone
question
Why do some scientists think that Jupiter's existence may have been critical for life to evolve on Earth?
answer
It kicked out many comets from the inner solar system through gravitational encounters, thus limiting the number of objects that could potentially hit the inner planets.
question
Which of the following is the most important for maintaining a stable climate on Earth over the time it took for large organisms to evolve?
answer
plate tectonics
question
Why do some scientists say that the Moon may have been important for the evolution of human life?
answer
It stabilized Earth's axis tilt and prevented large climate changes.
question
What defines the habitable zone around a star?
answer
the region around a star where liquid water can potentially exist on planetary surfaces
question
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
question
In 1974, a radio message was sent out from the Arecibo observatory in Puerto Rico. How far has it gotten, approximately?
answer
just a miniscule fraction of the distance across the Milky Way
question
At about what fraction of the speed of light do today's spacecraft travel?
answer
1/10,000
question
The Voyager I and II spacecraft visited the jovian planets in the 1980s. When will they reach the distance of the nearest stars?
answer
about a hundred thousand years from now
question
Which of the following describes a major danger of interstellar travel at near light speed?
answer
Atoms and ions in interstellar space will hit a fast-moving spacecraft like a flood of dangerous cosmic rays.
question
What type of rocket engine is used by the Space Shuttle?
answer
chemical rocket
question
Which of the following statements about matter-antimatter engines is not true?
answer
Matter-antimatter engines would be great in theory, but to date we have no evidence that antimatter even exists.
question
Which of the following best explains why an interstellar ramjet could, in theory, achieve continuous acceleration?
answer
It collects its fuel as it goes, rather than having to carry the weight of fuel along with it.
question
If we develop spacecraft that can take humans to nearby solar systems at a few percent of the speed of light, how long would it be before we could conceivably populate all habitable planets in the entire Milky Way?
answer
a few million years
question
Which of the following is not considered a likely solution to the question of why we are not currently aware of a galactic civilization?
answer
The galactic civilization probably is undetectable to us because it makes use of technologies that do not obey the known laws of physics.
