Chapter 17 The History of Life – Flashcards
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Scientists who specialize in the study of fossils are called?
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Biologists
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Sedimentary rocks form when layers of small particles are compressed
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Under Water
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Radioactive dating of rock samples?
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is a method of absolute dating
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Half-life is the length of time required for half the atoms in a radioactive sample to?
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Decay
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Earth's first atmosphere contained little or no?
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Oxygen
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In Miller and Urey's experiments with the origin of life-forms, electric sparks were passed through a mixture of gases to?
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Simulate Lightning
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Outlines of ancient cells that are preserved well enough to identify them as prokaryotes are?
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Microfossils
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Which event occurred at the end of the Paleozoic Era?
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Mass Exntinction
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The process that produces a similar appearance among unrelated groups of organisms is?
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Convergent Evolution
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As a group, the large-scale evolutionary changes that take place over long periods of time are called?
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Macroevolution
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How does relative dating enable paleontologists to estimate a fossil's age?
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The age of a fossil is estimated by comparing its placement in rock layers with the placement of fossils in other rock layers.
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Explain how radioactivity is used to date rocks.
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Radioactive elements decay at a steady rate, measured in units called half-lives. Radioactive dating uses half-lives to determine the age of a sample. Scientists can calculate the age of fossil-bearing rocks based on the amount of remaining radioactive isotopes they contain.
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What is the geologic time scale? How was it developed?
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The geologic time scale represents evolutionary time. It was developed by scientists who studied rock layers and index fossils worldwide.
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Discuss what scientists hypothesize about Earth's early atmosphere and the way oceans formed.
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When Earth was young, a collision with a very large object produced enough heat to melt Earth. Elements then rearranged themselves by density. The least dense elements, including hydrogen and nitrogen, formed the first atmosphere. About 3.8 billion years ago, Earth cooled enough for water to remain a liquid. Thunderstorms drenched the planet, eventually forming the oceans.
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Use the diagram below to explain the significance of Miller and Urey's experiment.
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Miller and Urey first demonstrated how organic matter might have formed in Earth's primitive atmosphere. By re-creating the early atmosphere (ammonia, water, hydrogen, and methane) and passing a spark (lightning) through the mixture, they demonstrated that organic matter, such as amino acids, could have arisen from simpler compounds.
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How are proteinoid microspheres like living cells?
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Proteinoid microspheres, like cells, have a selectively permeable membrane across which water molecules can travel and have a simple means of storing and releasing energy.
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How did the addition of oxygen to Earth's atmosphere affect the evolution of life?
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Some organisms began to evolve more efficient metabolic pathways that used oxygen for respiration; others became restricted to oxygen-free habitats.
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Describe the endosymbiotic theory.
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The endosymbiotic theory states that the first eukaryotic cells were formed from symbiosis among different prokaryotic cells. One type with the ability to use oxygen to generate ATP evolved into mitochondria. Another type that carried out photosynthesis evolved into chloroplasts. Both types were engulfed by other cells.
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Describe life as it existed in Precambrian Time.
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The first organisms were anaerobic, heterotrophic bacteria. Photosynthetic bacteria followed, adding oxygen to the atmosphere. Some bacteria adapted to the presence of oxygen, using it in cell respiration. The next to appear were eukaryotes, which gave rise to multicellular organisms.
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During what era did marine life become diverse?
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The Paleozoic Era
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What significant mammalian adaptations led to their success during the Cenozoic Era?
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Mammalian adaptations included hair that provided insulation against the cold and the protection of young before and after birth.
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What events led to the diversification of mammals?
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Disappearance of the dinosaurs enabled the smaller, relatively scarce mammals to flourish and diversify.
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Explain the process of adaptive radiation. Give an example.
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In adaptive radiation, species evolve into several different forms that live in different ways; examples: dinosaurs, mammals.
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Explain the pattern known as punctuated equilibrium.
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Punctuated equilibrium is a pattern in which long periods of little or no evolutionary change are interrupted by brief periods of rapid change.
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Use an example to explain the concept of coevolution.
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Students can use any example from the text to convey the concept of two species evolving in response to changes in each other over time.
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How can hox genes provide evidence of evolution?
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Homologous hox genes established body plans in organisms that had not shared common ancestors for millions of years.
