Astronomy Test Review #3 – Flashcards
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The planets in our solar system are thought to have come from
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the same cloud of gas and dust in which the Sun formed
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As the solar nebula collapsed, it became a disk because
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the overall rotation of the nebula plus collisions between particles made the particles go in more or less the same direction
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The outer planets are mostly large and gaseous because
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beyond the frost line, the gravity of large, ice-rich planetesimals captured the abundant light gases
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Because of the temperatures in the protoplanetary disk,
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Rocks and metals froze in both the inner and outer regions, and ices froze only in the outer region.
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As the solar nebula collapsed under its own gravity
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It heated and spun up
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You are sent to find dense and rocky planets. Where in the Solar System should you look?
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close to the sun
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A key characteristic of the cloud from which the Solar System formed was its
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rotation
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Planetary systems form
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within the dense disks of material surroudnign ver young stars
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The current arrangement of continents and oceans on the earth�s surface
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is the result of motion of plates
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The earth's atmosphere has
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changed due to volcanoes, rainwater induced chemical reations, and photosynthesis
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A planet that is differentiated
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must have been sufficiently molten that the denser materials sank to the center
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The magnetic field of the earth
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fluctuates in strength and reverses direction about every 20,000 years.
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The most useful means to explore the crust and mantle of the earth is
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studying earthquakes and seismic waves
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The convection of hot rocks in the mantle of the earth occurs because
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over some ranges of depth, the density is almost constant,
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We know the interior of the earth is liquid because
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earthquake waves that cant go through liquids are blocked by the interior of the earth.
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If there were no plate motions and continent building,
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everything would be under water
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Continents stay at the surface of the earth because
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They are made of low density rock that floats on the mantle
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Continental motions were first measured directly by
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military network of cameras set up to improve how accurately nuclear missiles could hit their targets
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Craters are caused by
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objects crashing into a planet's surface
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What is the main reason Mercury is hotter than the Moon?
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Mercury is closer to the sun
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The approximate age of the Solar System is
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4.5 billion years
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A rock sample is analyzed and found to have only 25% as much of a radioactive element as it would have been predicted to contain originally. The half-life of the radioactive element is 8x108 years. How old is this rock?
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1.6X10^2
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The lack of an atmosphere on the moon implies that
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it escaped because of the moon's weak gravity
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An object with no atmosphere or erosion processes is found in the Solar System with fewer craters on its surface than the lunar highlands. This object
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has had a new layer deposited on its surgace since it formed
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Mercury's surface looks a lot like
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the surface of the moon...
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Observations of the Moon show that the lunar maria have only 3% as many craters as the lunar highlands. It can be reasoned that
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lunar lava flowed across the surface AFTER most of the Moon's larger craters were created...
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The composition of the moon is
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similar to the earth's crust...
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An important scientific result from the Apollo program to send astronauts to the moon is
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Bringing back samples that allowed us to determine the ages of the rocks in different areas on the moon...
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Studying the craters on the moon shows that
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the rate of bodies striking the earth fell rapidly after the first 500 million years...
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Greenhouse gases ____________.
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absorb infrared light and transmit visible light ...
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What would the temperature of a planet be if it reflected nearly all the sunlight?
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it would be very, very cold...
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Mars' surface temperature would be higher if _______
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its atmosphere contained more greenhouse gases...
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The only body other than Earth to show signs of running water on its surface is
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Mars...
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Volcanoes on Mars
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are much larger than on earth...
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The concerns about global warming on the earth arise because
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humans are producing large enough amounts of carbon dioxide to increase the greenhouse effect significantly...
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Our understanding of the temperature on the earth a long time ago is based on
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measuring the relative amounts of oxygen isotopes in ancient seashells...
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The canals on Mars are
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an illusion caused by observers trying too hard to see features on the planet...
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Ultimately, the reason the Martian volcanoes grew to their current sizes is
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because mars is too small to retain significant interior heat...
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"Terraforming" refers to
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modifying the atmosphere of a planet to make its climate more like that of the earth...
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The surface of Venus
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is dominated by volcanic geology...
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Over decade-to-century time spans,
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independent measurements of the temperature on earth agree that it is going up...
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The metallic hydrogen in Jupiter's interior contributes to
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its strong magnetic field...
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The thermal emission from several giant planets
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is larger than would be predicted from the amount of sunlight absorbed by the planets...
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The high level of motions and activity in Jupiter's atmosphere results from
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convection driven in part by the interior heat of the planet...
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The low level of oxygen in Jupiter's atmosphere suggests that:
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Jupiter formed around a core that contains a large fraction of its oxygen...
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The poles and equator on Jupiter do not rotate at the same rate, implying that
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Jupiters visible surface is made of liquid or gas...
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Some planets were able to retain their hydrogen and helium as they formed because
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They were cooler...
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Aurorae are seen around the Earth and Jupiter because
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both have strong magnetic fields...
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Landing a spacecraft on Jupiter would be challenging because
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the "surface" is liquid hydrogen...
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Saturn is most similar to
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Jupiter...
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Uranus is very similar to
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Neptune...
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Moons that come too close to a planet
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Will disintegrate...
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Rings around planets
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are common around giant planets...
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Prior to the Cassini mission, we had not made a good map of the surface features on Titan because
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it has a relatively opaque atmosphere...
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The densest of Jupiter's large moons are found
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close to jupiter...
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This moon of Jupiter has a relatively smooth icy surface suggesting an underlying ocean.
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europa...
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Volcanoes may occur on a moon because of
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Tidal heating...
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The rings of Saturn are made of
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small particles largely of ice...
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Now that Huygens has landed on Titan, we see that its surface
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has drainage channels that look a bit like arroyos...
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Gaps and sharp edges in Saturn's rings are caused by
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gravitational effects of the planets moons...
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Pluto's atmosphere
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freezes on plutos surgace when it is far from the sun...
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A key ingredient in discovering Pluto was
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comparison of photographs taken at different times...
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We have determined the surface compositions of asteroids by
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finding pieces of them on the ground and studying spectra of sunlight reflected from them...
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Comets originate
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from cloud surrounding the Solar System...
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Pluto is likely one of the largest members of
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the Kuiper belt...
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A meteor shower results when
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The earth passes through the remnants of a comet...
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Comets are comprised mainly of
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ice...
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If all the asteroids in the asteroid belt were assembled into a planet, it would be
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Less than 1/1,000 of earths mass...
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No full-sized planet formed between Mars and Jupiter because
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Jupiters gravity kept stirring things up so no large object was safe from big collisions
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The relative lack of craters on the surface of the earth is because
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they erode away...
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What kind of experiment has proven most useful for finding planets around other stars?
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measuring accurate Doppler shifts in the stellar spectra to detect the effects of the planets graviational tugs on the stars' motions...
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How many planets have we discovered outside the solar system?
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about 700...
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Planetary debris disks are
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dust and particles generated by collisions amon small planetary bodies...at least one...
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The number of planets we know are suitable for life are
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at least one...
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The average temperature at the earth has been constant for the 4 billion years over which life has developed because
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the carbon dioxide level in teh atmosphere has changed to produce a greenhouse effect that compensated for changeds in the sun...
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The ice ages in the last few hundred thousand years seem to have been triggered by
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small perturbations in the orbit and polar inclination caused changes in the climate...
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To determine when ice ages have occurred in the past, we
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analyze the isotopes of oxygen in shellfish fossils ...
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Looking back over hundreds of millions of years, the earth
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is cooler than average...
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Planets in the "habitable zone" will
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may form life if they retain atmospheres, have the right amount of water, are on circular orbits, and meet other conditions...
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Habitable zones are the regions
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around a star where water on the surface of a planet is likey to be liquid...
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Life is unlikely to form on planets orbiting stars much more massive than the sun because
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they burn their nuclear fuels and evolve off the main sequence too quickly...
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Long periods when the climate was warmer than average were probably caused by
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greenhouse warming due to carbon dioxide released by many volcanoes...
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The weather is difficult to predict because
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weather is a chaotic system, that is, it is very complex and small changes can have larfe consequences ...
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Life could not form in the first few hundred million years of the formation of the earth
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because the rapid bombardment of the earth by large bodies made it very hostile to life...
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The most critical aspects of life are
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to harness energy and to reproduce...
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The very first forms of life we have found
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have survived apparently unchanged as the ultimate "living fossils"...
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Stanley Miller's experiment is famous because
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although eh had the wrong chemicals, he introduced the idea of trying to make chemical precursors to life in the laboratory...
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Errors, or mutations, in the reproduction of early life
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were the underlying force for the development of improved life forms...
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DNA replication carries the information for new organisms because
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DNA attracts bonds specific nucleotides that only pair with other specific nucleotides in the DNA chain, producing a negative copy of itself...
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Mars is a high priority target for space exploration because
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it appears to have many of the conditions needed for life in its early history, so we might find signs that life formed...
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Mars is an attractive place to look for early life forms because
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it is on the edge of the suns habitable zone-life might have formed when it still had oceans of water ...
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Multiple forms of complex animal life first appeared
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more than 3 billion years after the first life on earth...
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Sex was an important development toward advanced life because:
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it greatly increased the genetic variety in living organisms...
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Nucleated, complex cells appear to have formed
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by cells developing ways to live together to their mutual advantage ...
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Many Cambrian creatures are related to
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arthropods, the group that includes spiders, insects, crabs, lobsters...
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The rapid development of a broad variety of animals in the Cambrian period occurred
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for reasons we are not entirely sure of, although we have a number of ideas...
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A new development with the Cambrian creatures overall was
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hard shells for protection and predators that fed on other animals...
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Judging by how long it took to happen, the most difficult step toward complex life was
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development of nucleated cells...
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A disaster in which a large asteroid or comet strikes the earth is
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bound to happen sooner or later because the giant planets keep deflecting such objects into chaotic orbits...
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"Chaos" means ___________ to a scientist
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the behavior of a system where very small changes can have very large consequences...
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The means by which the K/T impactor probably killed most of the dinosaurs is
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material hurled up into space came back down, heating up to hgih temperature when it struck the atmosphere and baking them...
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. After the K/T disaster,
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primitive mamals like opossums became abundant relatively quickly...
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Mass extinctions
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occur roughly every hundred million years, probably from a variety of causes...
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Evidence that an asteroid or comet killed the dinosaurs in the K/T extinction includes:
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the exsistence of a giant crater off the Yucatan Peninsula, and observations of the recent impacts of a comet on jupitar and a thin layer of iridium-rich material in rock around earth...
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High iridium content indicates an object came from space because:
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iridium is a heavy material and therfore most of that in the earth has sunk to the center...
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Evidence that large asteroids hit the earth from time to time includes
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the record of craters on other solar system bodies...
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Convergent evolution means
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facing similar challenges, different types of animal ten to evolve toward similar solutions...
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Brain sizes
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have tended to get larger with time...
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Sophisticated, thinking brains and complex nervous and sensory systems developed
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to allow location of easily-digested foods...
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Development of civilization on Earth has waited until sophisticated, thinking brains evolved and
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the climate entered a mild period that made it easier to grow food...
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The number of civilizations we might be able to receive radio signals from
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is very hard to estimate- we can only try and see what happens ...
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The probability of a "fair" coin coming up heads is 1/2. What is the probability of it coming up heads three times in a row?
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1/8...
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Animals with relatively large brains
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might just be extra-good at sensing and hunting their prey ...
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Infant humans
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use most of their body energy to support large and growing brains...
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The biggest uncertainty in how many civilizations there are right now in other planetary systems around us is probably
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how long a civilization lasts before it dies out or destroys itself...
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Science
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has some major events that it cannot explain, like what happend before the Big Bang...
