Deck 15: Life on Other Worlds

Question 1

What are a cell's DNA molecules made of?

A) amino acids
B) proteins
C) sugars, phosphates, and bases
D) fatty acids

Answer 1

sugars, phosphates, and bases

Question 2

Which of the following lists events in the order that they occurred?

A) the Cambrian period, first life on land, first primitive mammals, first flowering plants
B) first life on land, the Cambrian period, first primitive mammals, first flowering plants
C) the Cambrian period, first life on land, first flowering plants, first primitive mammals,
D) first life on land, the Cambrian period, first flowering plants, first primitive mammals,

Answer 2

the Cambrian period, first life on land, first primitive mammals, first flowering plants

Question 3

Why do astrobiologists spend relatively little time studying the possibility of silicon-based life in the universe?

A) Silicon can not form complex molecules.
B) Silicon is not very abundant in the universe.
C) They have no examples to study.
D) Silicon has a high melting point

Answer 3

They have no examples to study.

Question 4

Why do scientists no longer think that complex organic molecules must have first formed in shallow pools?

A) Shallow pools wouldn't have a sufficient concentration of amino acids.
B) Complex molecules could not form in the early Earth's atmosphere.
C) Complex molecules would be destroyed by volcanism and meteorite impacts.
D) Abiogenesis requires an existing form of life.

Question 5

What are believed to have been the best places for life to have formed on Earth?

A) near the south pole, on the ice
B) on the continent of Africa, in the areas with no water
C) in liquid water, probably in the deep oceans near hydrothermal vents
D) in volcanoes, where lots of energy was available

Question 6

What molecule in the cell nucleus stores the information to make specific proteins out in the cell body?

A) an enzyme
B) DNA
C) RNA
D) ALH84001

Question 7

Suppose that a lifeform was discovered on Mars, and all of the different individuals in this lifeform had exactly the same genetic material. Why would biologists find this surprising?

A) Mars has never had conditions suitable for life.
B) Lifeforms on other planets are not expected to have genetic material.
C) Mars has had varying environmental conditions through its history.
D) Random variations in genetic material are expected to help lifeforms adapt.

Question 8

DNA is coiled into a tight spiral and makes up the genetic material in a cell. What is that material called?

A) amino acids
B) enzymes
C) nucleus
D) chromosomes

Question 9

Which of the following is a segment of a chromosome that controls a specific function?

A) DNA
B) RNA
C) a gene
D) an amino acid

Question 10

When did the first single-celled organisms evolve on Earth?

A) longer than 4.6 billion years ago
B) between 4.6 and 3.4 billion years ago
C) between 3.4 and 1.2 billion years ago
D) Between 1.2 billion years ago and 500 million years ago

Question 11

What molecule carries information from the cell nucleus out into the cell, where specific proteins are made from the information?

A) an enzyme
B) DNA
C) RNA
D) PAH

Question 12

How is DNA important to a cell?

A) DNA is the cell membrane that allows nutrients to enter the cell and allows waste to leave the cell.
B) DNA contains the information necessary to make all of the molecules required by the organism to reproduce itself.
C) DNA contains the information necessary for a cell to defend itself against nearby enemy cells.
D) DNA is the molecule that stores energy within a cell.

Question 13

What was happening elsewhere in the universe when the first complex life appeared on Earth?

A) The Milky Way galaxy was just forming.
B) Some of the stars we see in the sky today were still forming.
C) The light we see from stars on the other side of the Milky Way was just starting its journey.
D) The late heavy bombardment in our solar system had just finished.

Question 14

What shows that the building blocks of life form naturally under a wide range of circumstances?

A) the Miller-Urey experiment
B) the Chicxulub event
C) the earliest fossils
D) the Drake equation

Question 15

If you uncoiled and stretched out all of the DNA molecules in a typical human, what would their total length be?

A) about 1 kilometre
B) about 600 kilometres
C) about 1 astronomical unit
D) about 600 astronomical units

Question 16

What did the Miller-Urey experiment create?

A) artificial proteins
B) amino acids
C) simple mould
D) DNA

Question 17

Which of the following best describes a mutation?

A) an alteration of DNA base pairs with random or environmental causes
B) an alteration of DNA that is a result of genetic engineering
C) an alteration of DNA that is harmful to the survival of an organism
D) an alteration of DNA that enhances the survival of an organism

Question 18

A single human cell encloses about 1.5 metres of DNA, containing 4.5 billion base pairs. How far apart are these base pairs in the DNA?

A) 3.3×10¹⁰ nm
B) 3×10⁹ nm
C) 300 nm
D) 0.34 nm

Question 19

How do we usually refer to deoxyribonucleic acid?

A) as vitamin D
B) as reproductive enzymes
C) as RNA
D) as DNA

Question 20

What do DNA molecules contain the patterns for?

A) amino acids
B) proteins
C) phosphates and sugars
D) four kinds of bases

Question 21

Suppose that SETI researchers discovered a radio signal coming from a star in the direction of the centre of the Milky Way that was about 10% closer to the centre than the Sun. If humans sent a reply to this signal immediately, and the aliens replied when they got our message, how long would it take before the alien reply reached Earth?

A) a few years
B) several decades
C) thousands of years
D) a few hundred years

Question 22

Which of the following star systems would be the best place to search for planets that could host life?

A) an isolated K star
B) an isolated F star
C) a binary system of two G stars
D) an G star with a protoplanetary disk

Question 23

Suppose you wanted to use your radio telescope to search for signals from alien civilizations. Which stars would be the best targets?

A) Low-mass stars, because they are more likely to be old.
B) Luminous stars, because they are the easiest to find in the sky.
C) Nearby stars, because signals would travel to us in the shortest time.
D) Binary stars, because the chances of habitable planets are twice as high.

Question 24

Why are massive main sequence stars not likely to have planets that contain life?

A) These stars would sweep away all of the material from which planets could form.
B) These stars are too hot to allow water to exist as a liquid on any planets that might form.
C) These stars are on the main sequence for too short a time to allow life to evolve.
D) These stars are almost always binaries and planetary orbits are unstable around binaries.

Question 25

Presuming that it takes a few billion years for complex life to evolve in a stable environment, what kind of stars are most likely to currently have inhabited planets?

A) G to K main sequence stars
B) B to A main sequence stars
C) G to K giants
D) white dwarf stars

Question 26

Who is the intended recipient of the Arecibo message?

A) astronomers on the other side of the world
B) intelligent civilizations in a nearby globular cluster
C) possible inhabitants of Gliese 581
D) astronauts aboard the International Space Station

Question 27

Which of the choices below sorts the solar system locations from most-to-least likely for life to develop?

A) Mars, Europa, Enceladus, Titan
B) Mars, Earth's moon, Mercury, Europa
C) Mercury, Venus, Earth's moon, Mars
D) Titan, Europa, Venus, Mars

Question 28

The first complex life appeared on Earth about 0.5 billion years ago. What period was that?

A) the Jurassic Period
B) the Cambrian Period
C) the Precambrian Period
D) the Neolithic Period

Question 29

What happens to a star's habitable zone as the star ages?

A) It shrinks in size.
B) It becomes very narrow.
C) It moves farther from the star.
D) It stays in the same position.

Question 30

What is "the habitable zone"?

A) a region only found around G and K stars
B) the region on a planet where conditions are acceptable for life to exist
C) a region around a star at a distance where a planet's temperature would permit the sustained existence of liquid water
D) a region on a young planet at a temperature where amino acids can begin to form DNA molecules

Question 31

What is ALH 84001?

A) It is a meteorite that some scientists think shows evidence for life evolving on Mars.
B) It is the compound used by Miller and Urey to begin their experiment to produce amino acids.
C) It is the molecule that controls the reproduction of DNA within a cell.
D) It is the molecule that acts as DNA's messenger to assemble proteins from amino acids.

Question 32

What is important about the habitable zone around a star that makes astronomers believe life could exist there?

A) The level of UV radiation from the star is minimal in the habitable zone.
B) Only in the habitable zone can complex organic molecules be found.
C) Planets in the habitable zone will always have an oxygen atmosphere.
D) In the habitable zone, liquid water can exist on the surface for long periods of time

Question 33

Why do scientists consider it to be very unlikely that UFO reports are due to visitors from another solar system?

A) Interstellar travel requires huge amounts of time and energy.
B) There is no evidence that life exists elsewhere in the universe.
C) No scientist has ever seen a UFO.
D) Scientists believe that any alien civilization would be much more advanced than humans.

Question 34

The most likely region of the radio spectrum for communication with other civilizations is called "the water hole." What part of the spectrum is this?

A) the part of the spectrum near the radio emission of water
B) the part of the spectrum between the radio emission of hydrogen and oxygen
C) the part of the spectrum between the radio emissions of hydrogen and OH
D) the part of the spectrum near the radio band where water in the Earth's atmosphere strongly absorbs energy

Question 35

What is the most important reason why scientists do NOT believe Earth has ever been visited by alien life forms?

A) They believe that life can evolve only on Earth.
B) They can't explain how aliens could travel such great distances.
C) There is no credible evidence.
D) Their teachers didn't believe in alien visitations.

Question 36

The New Horizons spacecraft travels at about 16 km/s. At this speed about how long would it take to reach TRAPPIST-1, which is 40 light-years away?

A) 90 000 years
B) 640 000 years
C) 750 000 years
D) 23 million years

Question 37

Which of the following is used by all known forms of life on Earth as a medium for chemical reactions?

A) gaseous helium
B) frozen carbon dioxide
C) liquid water
D) frozen water

Question 38

What wavelengths are used in current searches for extraterrestrial intelligence by radio telescopes?

A) wavelengths that are longer than the local wavelengths emitted by the Earth's atmosphere
B) wavelengths that are longer than the radio wavelength "noise" naturally emitted by our galaxy
C) the same wavelengths that are used on Earth for TV signals
D) wavelengths with the greatest speeds

Question 39

All of the terms in the Drake equation are estimates. In the next decade, which of these estimates is likely to improve the most because of better observational data?

A) number of stars in the Milky Way
B) fraction of stars with planets
C) fraction of planets where life evolves to intelligence
D) number of planets per star in the habitable zone

Question 40

Why do some scientists think that the idea of the habitable zone as a fixed distance range from a star is too restrictive?

A) Changes in stars' brightness might change the position of habitable zones.
B) Many forms of life do not require liquid water.
C) Planets may not always keep a constant distance from their star.
D) Liquid water can be maintained by tidal heating.

Question 41

The portion of the electromagnetic spectrum between the 21 cm line of neutral hydrogen and the 18 cm line of OH is known as the _____________ _____________.

Question 42

Which of the following limits the number of technological civilizations in our galaxy?

A) the lifetime of M dwarf stars
B) the number of satellite galaxies of the Milky Way
C) the fraction of civilizations that wish to communicate with others
D) the number of planets per star in a habitable zone for longer than a few billion years

Question 43

The sudden increase in complexity of life nearly 4 billion years ago is called the ______________ __________________.

Question 44

The DNA molecules contain six different bases.

Question 45

What does the Drake equation tell us about life in the universe?

A) Life should be very common in the Milky Way Galaxy.
B) Humans are likely to be the only technological civilization in the Milky Way Galaxy.
C) There are probably 10 million other civilizations in the Milky Way Galaxy that could be trying to communicate with us.
D) We have very little knowledge about how common life in the universe is.

Question 46

The oldest fossils on Earth are more than 3 billion years old.

Question 47

A certain galaxy has twice the star formation rate as the Milky Way Galaxy but stars in this galaxy are only half as likely to have planets. Using the Drake equation, how would the predicted number of technological civilizations in this galaxy compare to the number predicted for the Milky Way Galaxy?

A) It would be half as much.
B) It would be the same.
C) It would be twice as large.
D) It would be 4 times larger.

Question 48

When considering the possible number of technologically advanced civilizations in our galaxy, which of the following factors is it useful to consider?

A) the average lifespan of an alien
B) the average lifespan of the civilization
C) the distance to the civilization's planet
D) the type of advanced communication they use

Question 49

In the Drake equation, when considering the possible number of technologically advanced civilizations in our galaxy, which of the terms is most uncertain?

A) the number of stars in our galaxy
B) the average lifespan of the civilization
C) the fraction of suitable planets on which life begins
D) the fraction of a star's life during which an intelligent species is communicative

Question 50

Evolution can occur only if there is some random variation.

Question 51

The Viking landers searched for life on ____________________.

Question 52

The Miller-Urey experiment succeeded in creating _____________ _________.

Question 53

____________ is often referred to as the "universal solvent."

Question 54

Evolution is a random process.

Question 55

The oldest easily identifiable fossils appear in sedimentary rocks that formed 3.4 billion years ago during the ____________________ period.

Question 56

All life on Earth is based on carbon chemistry.

Question 57

DNA molecules cannot be altered by chance errors in reproduction.

Question 58

The ___________________ ___________ is a region around a star where liquid water can exist.

Question 59

The equation that estimates the total number of communicative civilizations in the Milky Way Galaxy is called the ____________________ equation.

Question 60

The most important factor necessary for life to form appears to be the existence of ____________ _____________ on the surface of the planet.

Question 61

There is only enough room for one planet to orbit within a star's habitable zone.

Question 62

Chemical evolution concentrated the various smaller molecules into more stable forms.

Question 63

Even if societies on stars in distant galaxies survive at a technological level for only 10 years, that is long enough to establish two-way communication with them.

Question 64

The wavelengths that are most likely for communication with other civilizations are those in the water hole.

Question 65

A stellar habitable zone around cooler stars is larger than the stellar habitable zone around Sun-like stars.

Question 66

The Viking spacecraft searched for life on Mars by looking for the effects of life in the upper atmosphere.

Question 67

The Miller-Urey experiment created synthetic DNA.

Question 68

If life is to develop on a planet, the planet must lie well inside the inner edge of its star's habitable zone.

Question 69

A stellar habitable zone around hotter stars is larger than the stellar habitable zone around Sun-like stars.