Chapter 24
Basic Skills/Definitions Quiz
Part A
According to fossil evidence how far back in time did life on Earth exist?
Hint A.1
Study Section 24.1.
ANSWER:

About 3.5 billion years or more. About 65 million years. About 2.0 billion years. About 545 million years.
Part B
Why do scientists say that evolution is a "theory"?
Hint B.1
Study Section 24.1
ANSWER:

Because they are not very confident that it really happened. Because it is supported by only a small amount of evidence. Because it's really just a guess about how life developed on Earth. Because it explains a great deal about life and is supported by an enormous body of evidence.
Part C
What is a mutation?
Hint C.1
Study Section 24.5
ANSWER:

A change in the type of food an organism consumes. A change in a living cell's DNA. A change in an organism that turns it into a different species. A change in the physical appearance of a living organism.
Part D
Based on DNA studies, it seems that all life on Earth _________.
Hint D.1
Study Section 24.1.
ANSWER:

requires oxygen to survive shares a common ancestor arose from one of five distinct ancestors that lived about two billion years ago belongs to one of just two kingdoms: plants and animals
Part E
Which of the following is considered by biologists to be a likely place where life first arose on Earth?
Hint E.1
Study Section 24.1.
ANSWER:

Deep underground In hot water near undersea volcanoes On meteorites that landed on Earth On land surfaces that got moderately heavy rainfall
Part F
How did oxygen (O2) get into Earth's atmosphere?
Hint F.1
Study Section 24.1.
ANSWER:

It was released by life through the process of photosynthesis. It came from chemical reactions with surface rocks. It was outgassed from volcanoes. It was captured from the solar nebula.
Part G
Which of the following is NOT considered crucial for life to exist on some world?
Hint G.1
Study Section 24.1.
ANSWER:

An atmosphere Liquid water A source of energy that can be used by life A source of nutrients
Part H
Which of the following best describes what we mean by a habitable world?
Hint H.1
Study Section 24.2.
ANSWER:

A planet or moon with life A planet or moon that lies within its star's habitable zone A planet or moon that could support life, if any life happened to be on it A planet or moon on which humans could survive if we happened to go there
Part I
Which of the following places is NOT generally considered a potential home for life in our solar system?
Hint I.1
Study Section 24.2.
ANSWER:

Jupiter's atmosphere Europa Mars Ganymede
Part J
The Sun's habitable zone _________.
Hint J.1
Study Section 24.2.
ANSWER:

extends from the orbit of Earth to the orbit of Jupiter consists only of Earth, since Earth is the only planet known to be inhabited extends from just beyond the orbit of Mercury to just beyond Earth's orbit extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars
Part K
Why don't we expect to find life on planets orbiting high-mass stars?
Hint K.1
Study Section 24.3.
ANSWER:

Planets cannot have stable orbits around high-mass stars. The stars are too hot to allow for life. The lifetime of a high-mass star is too short. The high-mass stars emit too much ultraviolet radiation.
Part L
Looking for an Earth-size planet around a nearby star (besides the Sun) is like looking for a pinhead located _________.
Hint L.1
Study Section 24.3 (and review the scale of the solar system in Chapter 1).
ANSWER:

thousands of kilometers away a few hundred kilometers away across the length of a football field across the street
Part M
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?
Hint M.1
Study Section 24.3.
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. The debate raged for a while, but is now settled. We are now quite certain that Earth-like planets are rare. The debate raged for a while, but is now settled. We are now quite certain that Earth-like planets are common. 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.
Part N
At present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?
Hint N.1
Study Section 24.4.
ANSWER:

By using radio telescopes to search for signals from extraterrestrial civilizations By seeking access to the secret records and alien corpses kept at the military's Area 51 in Nevada By analyzing high-resolution images of nearby stars in search of evidence for structures that could not have developed naturally By searching for planets around distant stars By using X-ray telescopes to search for exhaust from interstellar spacecraft
Part O
In the equation Number of Civilizations = N HP ( f life ( f civ ( f now, what do we mean by f now?
Hint O.1
Study Section 24.4.
ANSWER:

We mean the fraction of planets with civilizations at the present time (as opposed to only in the past or future). We mean the fraction of civilizations in the universe that currently are sending messages to us. We mean the fraction of all species ever to exist that we currently are aware of. We mean the fraction of planets in the galaxy on which a civilization could theoretically develop right now.
Part P
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?
Hint P.1
Study Section 24.4.
ANSWER:

Never, because they will rust and fall apart Several decades About a thousand years Tens of thousands of years Hundreds of years
Part Q
Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will _________.
Hint Q.1
Study Section 24.4.
ANSWER:

never be able to make the trip within their lifetimes have more fun than people who stay behind on Earth age more than people who stay behind on Earth age less than people who stay behind on Earth
Part R
If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?
Hint R.1
Study Section 24.5.
ANSWER:

They are anatomically much like us, with two arms, two legs, two eyes, and two ears. For fun, they enjoy "buzzing" to Earth and temporarily abducting people, showing a clear preference for people located in less-developed rural areas. They are far more technologically advanced than we are. They have social structures that are completely different from our own; for example, different types of "family" units, and so on.