Chapter 19 the history of life – Flashcards
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Paleontologists
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Scientists who study fossils
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Extinct
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No living members
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Relative dating
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A method of determining the age of a fossil by comparing its placement with that of fossils in other rock layers
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Index fossils
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A distinctive fossil that is used to establish and compare the relative ages of rock layers and the fossils they contain
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T or F: relative dating does tell the age of a fossil in years
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False
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Radiometric dating
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Method in which scientists use radioactive isotopes to find the age of rocks and fossils.
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Half-life
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The time it takes for half the radioactive atoms in a sample to decay
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Geologic time scale
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The time line used to represent Earth's history
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T or F: the geological time scale is based on both relative and absolute dating.
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True
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Era
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A major division of geologic time; usually divided inti two or more periods
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Period
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A division of geologic time into which eras are subdivided.
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Which eon are humans present in the geologic time scale?
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Phanerozoic
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In the geologic time scale, which era are humans in?
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Cenozoic
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Macroevolutionary patterns
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The changes in anatomy, phylogeny, behavior, and ecology, which take place in clades that are larger than a single species.
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Background extinction
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Extinction caused by the slow and steady process of natural selection
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Mass extinction
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An event during which many species become extinct during a relative short time
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What process influence whether species and clades survive or become extinct?
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If the rate of speciation in a clade is equal or greater than the rate of extinction, the clade will live; if the rate of extinction is greater than the rate of speciation, the clade will become extinct.
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Gradualism
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The evolution of species by the gradual addition of small genetic changes over long periods of time
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Punctuated equilibrium
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The pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
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Adaptive radiation
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Process by which a single species or. Small group of species evolves into several different forms that live in different ways
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How fast does evolution take place
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Evolution has moved at different rates for different organisms at different times over the long history of life on Earth.
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Convergent evolution
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Process by which unrelated organisms independently evolve similarities when adapting to similar environments
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Coevolution
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The process by which two species evolve in response to changes in each other over time.
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What are two forms of macroevolution
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Adaptive and convergent evolution
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What do scientists hypothesize about early Earth?
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Earth's atmosphere was mainly CO2, water vapor, and nitrogen, with lesser amount of carbon monoxide, hydrogen sulfide, and hydrogen cyanide. It contained little or no oxygen.
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What do scientists hypothesize about the origin of life?
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Scientists suggested how mixtures of organic compounds necessary for life could have arisen form simpler compounds in the atmosphere of early Earth
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What do fossils reveal about ancient life?
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The fossil record shows the structure of ancient organisms, their environment, and the way in which they lived.
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Plate tectonicts
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The theory that explains the slow movement if solid continental plates over Earth's mantle.
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What three periods are in the era cenozoic?
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Quaternary, Neogene, Paleogene
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What do fossils reveal about ancient life?
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From the fossil record, paleontologists learn about the structure of ancient organisms, their environment, and the ways in which they lived.
