A103 Exam 2 (Homework)

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Life on Earth can use a variety of different carbon and energy sources. However, the onething that no organism on Earth can survive without is

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liquid water

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More than 96% of the mass of living cells are made of

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carbon, hydrogen, oxygen, and nitrogen

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Any change in the base sequence of an organism’s DNA is referred to as a

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mutation

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The most numerous life form on Earth is

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microbes

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Chemically based extraterrestrial life

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may not use DNA to store information but will very likely use a molecule with a similar function

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The complete set of genetic information that makes up an organism is known as a

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genome

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Which is the MOST important property of the element carbon that makes it ideal as afundamental building block of biological molecules?

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it readily forms chemical bonds with itself and other elements, allowing a wide variety ofcomplex molecules to form

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What is the MOST important role that carbohydrates play in living organisms on Earth?

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short term energy storage

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What is the MOST important role that proteins play in living organisms on Earth?

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basic function of living organisms

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Which of the following observations is consistent with the hypothesis that all life on Earth has a common ancestor?

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different organisms use the same set of amino acids

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Metabolism is a term that describes the

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chemical processes that occur inside cells

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Chemists refer to molecules containing carbon atoms as

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organic

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The discovery of extremophiles on Earth suggests that

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life elsewhere may be possible over a much wider range of conditions than initially thought

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The most basic definition of life which takes account of the relative importance of the sixfundamental properties of living things is that life is something that can

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reproduce and evolve through natural selection

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What is the main factor that drives Darwinian evolution?

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the competition for finite resources

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Different dog breeds have been bred by humans from a common ancestor over the pastfew thousand years. This is an example of

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artificial selection

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The resistance of bacteria to certain antibiotics is an example of

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natural selection

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Which of the following is NOT considered a key piece of evidence supporting a common ancestor for all life on Earth?

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the fact that all life on Earth is carbon-based

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All organisms have finite lifetimes and eventually die. Which of the basic characteristics of life corrects for this?

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reproduction

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Energy utilization in living organisms is

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one of the most basic requirements of life, without which organisms could not maintain order, grow, and reproduce

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The geological record suggests that life on Earth

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appeared very soon after the late heavy bombardment, perhaps within 100 million years or less

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The first living organisms probably were

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cells without nuclei that used RNA as their genetic material

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Many approaches are used in examining how life originated on Earth. Currently, the most promising of these approaches involve

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laboratory simulations of conditions present on the early Earth

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Which statement about Earth’s ozone layer is true?

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it formed only after the atmosphere became rich in oxygen.

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Early life arose in an oxygen-free environment, but if any of these microbes had somehow come in contact with oxygen, the most likely effect would have been

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to kill them

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The oxygen in Earth’s atmosphere was originally released by

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cyanobacteria.

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The Cambrian explosion refers to

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a dramatic increase in animal diversity beginning about 542 million years ago

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According to the fossil evidence, modern humans

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evolved on a lineage that split from other apes 6 million years ago or more

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Biologists suspect that the first molecules of RNA probably formed

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on the surfaces of clays or other minerals

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Approximately 545 million years ago, at the start of the Cambrian Period,

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an explosion of genetic diversity appeared, leading to the appearance of the first animals.

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A major reason why life on Earth is unlikely to have originated on land is that

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there was no ozone layer to shield out harmful UV rays

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In Miller–Urey experiments, prebiotic molecules are produced using a variety of different gasses to represent the early Earth’s atmosphere. The one situation where prebiotic molecules are NOT produced is when

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oxygen (O2) is present in the flask

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f the conditions required for substantial amounts of oxygen to build up in a planetary atmosphere are quite rare, then life on other worlds

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may still be common but may never be able to evolve past microscopic forms.

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The search for extraterrestrial Earth-like life is essentially a search for

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liquid water

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Which of these is NOT an advantage for water over other liquids as a solvent for life forms?

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water plays a role in photosynthesis

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The hypothesis that an impact killed the dinosaurs is

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well supported by geological evidence

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Where did the asteroid that is believed responsible for the extinction of the dinosaurs hitthe surface of the Earth?

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in the Yucatan peninsula in Mexico

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Why can studies of carbon isotopes be used to detect the presence of past biological activity in rocks?

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living organisms absorb certain carbon isotopes more easily than others

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One theory for the origin of life suggests that life was transported to Earth in meteorites.This is referred to as

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panspermia

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What do we mean by “The Oxygen Crisis” in relation to the evolution of life on Earth?

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the extinction of older anaerobic life as oxygen builds up in the atmosphere

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Oxygen and carbon, both of vital importance to biological organisms, are

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the third- and fourth-most-abundant elements in the universe.

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We can recognize the oldest surface regions of Mars by the fact that they have

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the most impact craters;

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Compared to liquid water, liquid methane is

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colder;

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Frozen lakes often have liquid water beneath their icy surfaces primarily because

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ice floats and provides insulation to the water below;

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Temperatures on Mercury are

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very hot in the day and very cold at night;

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The reason that Venus is so much hotter than Earth is

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its thick, carbon dioxide atmosphere creates a far stronger greenhouse effect.

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Life is probably not possible in Jupiter’s atmosphere because

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winds are too strong.

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Which of the following are you most likely to find if you randomly choose a small moon of oneof the jovian planets to examine?

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water ice;

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The largest component of the martian atmosphere is

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carbon dioxide

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Minerals in surface rock studied by the martian rovers seem to tell us that

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they formed in water;

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Rivers on Mars

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existed in the past but are dry today;

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Which must be true if Mars was warmer and wetter in the past?

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Mars once had a much thicker atmosphere.

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What is/are the most likely source(s) of the methane gas detected in the Martianatmosphere by the Mars Express orbiter?

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biological and volcanic activity

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Under the leading scenario, if Mars once had much more carbon dioxide in its atmosphere,most of this carbon dioxide is now

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gone, because it was lost to space;

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The Viking experiments found

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some results consistent with life, but others that were inconsistent with life.

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The Northern hemisphere of Mars is at

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a lower than average elevation and is relatively smooth

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The ancient water erosion features on the surface of Mars suggest that the planet must havehad a much

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warmer, thicker atmosphere in the past

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Evidence for very recent water erosion on Mars comes from the observations of

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gullies in the rims of craters

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The process of making an uninhabitable planet like Mars habitable and suitable for humansis referred to as

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terraforming

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Liquid water cannot exist for very long on the surface of Mars today because

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the Martian atmosphere is too thin

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The largest Jovian moons, Ganymede and Titan, are

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larger than Mercury but smaller than the Earth

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Most of the smallest Jovian moons are most likely

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captured asteroids and comets

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The moons of Saturn may have large amounts of ammonia and methane ice, while those ofJupiter do not because

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the greater cold at Saturn’s distance from the Sun means that ices of ammonia and methane could condense there but not at Jupiter.

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Which statement about synchronous rotation is true?

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It occurs commonly as a result of tidal forces exerted on moons by their parent planets.

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Io is covered in volcanoes while Europa is covered in ice because

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Io is subject to stronger tidal heating than Europa

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Where might we find liquid water on Titan?

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beneath the surface near sources of “icy volcanism”

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Photosynthesis is an unlikely source of energy for life in the seas of Europa primarily because

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sunlight at the distance of Jupiter is too weak

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Why were scientists so surprised to find active geology on Enceladus?

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because it is so small

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If life exists in the Europan oceans, it most likely originated

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close to volcanic vents on its ocean floor

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The complexity of any life present in Europa's subsurface ocean is mainly limited by theA) amount of water in the ocean

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amount of available energy to sustain it

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The chances for life on Titan’s surface are considered slim, mainly because

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the surface temperature is far below the freezing point of water.

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What is believed to have been the main source of Titan's atmosphere?

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outgassing from its interior

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How is Titan similar to the Earth?

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like the Earth, Titan has an atmosphere made mostly of molecular nitrogen

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Saturn's icy moon Enceladus

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has fountains of ice particles and water vapor spraying out from its surface

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Even though Titan has liquid methane on its surface, some internal heat, and plenty of carbon-containing compounds, it is not a suitable place for life as we know it because

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it is far too cold, and methane is not a very good biological solvent

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Although Titan is roughly the same size as Mercury, Titan has an atmosphere whileMercury does not. How can this be?

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Even though Titan's gravity is weak, it is much colder, allowing its slower moving molecules to be trapped in its atmosphere

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The fact that the strength of gravity decreases with distance means the force of gravity exerted by one object on another (e.g., the Earth and Moon) is greater on the near side than the far side. This effect is commonly referred to as a

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tidal force

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Chemical disequilibrium is likely to be present in all the following places except in (a) volcanic vents on ocean floors

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solid ice exposed to the extreme cold of space

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An understanding of redox chemical reactions gained by studying life on Earth lead us to think that

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life could exist on any geologically active world with liquid water

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Which of the following statements about Europa is NOT true?

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Europa’s oceans are heated by interaction between Europa’s and Jupiter’s magnetospheres

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What is the definition of a star’s habitable zone?

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the range of distances from the star where liquid water can be stable on the surface of a suitable planet

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Over time the Sun’s habitable zone has …

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widened and moved farther from the Sun

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Europa is located outside the Sun’s habitable zone and yet may be habitable. How can this be?

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Europa is tidally heated, allowing liquid water to exist beneath its icy surface

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The Moon is in the habitable zone of the Sun at the same distance as the Earth but is nothabitable. How can this be?

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the Moon is too small to retain an atmosphere necessary for liquid water to be stable

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Apart from its distance from its parent star, what is the next most important factor that

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the size of the planet

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The range of distances that has remained habitable for the entire duration of the Sun's lifetimeis referred to as the

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continuously habitable zone

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The moist greenhouse effect refers to

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the warming process by which water vapor rises into the upper atmosphere above the ozonelayer where it is then broken apart by ultraviolet radiation

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Venus’s atmosphere has much more carbon dioxide than Earth’s because

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Venus lacks oceans in which carbon dioxide can be dissolved;

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What is the likely reason for Venus’s lack of water in any form?

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The water was in the atmosphere, where molecules were broken apart by ultraviolet light from the Sun.

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f Earth were to be moved to Venus’s orbit, it would probably

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suffer a runaway greenhouse effect and become even hotter than Venus is today.

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Compared with today, the Sun’s habitable zone when it was young was

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narrower and closer to the Sun

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Which of the following could cause Earth to become uninhabitable in about 1 billion years?

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a moist greenhouse effect;

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Global warming means that

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Earth’s average temperature is increasing;

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The current concentration of atmospheric carbon dioxide on Earth is

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higher than the concentration at any time during the past million years;

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Why does the Sun brighten with time?

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as hydrogen is converted into helium in the core, the number of hydrogen nuclei decreases,decreasing the fusion rate. To maintain the balance with gravity pressing inward, the core compensates by shrinking and heating up

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A planet that is not within a habitable zone CANNOT have

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abundant liquid water on its surface.

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Around 4 billion years ago, Venus could have been more Earth-like with liquid water on its surface because

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the Sun was dimmer so Venus would have been in the Sun’s habitable zone

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Stars much less luminous than the Sun have

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narrower habitable zones, decreasing the odds of finding habitable planets but much longer lifetimes allowing life to appear and evolve

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Measurements of carbon dioxide concentrations in our atmosphere over the past 650,000years show

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a direct correlation with global surface temperatures

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As global warming raises the moisture content in our atmosphere, storms will

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become more numerous and severe