What are the lines of evidence that Alfred Wegener used to support the idea of continental drift? Why did scientists of his day doubt that continents drifted?
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Alfred Wegener was the first scientist to advance the idea of mobile continents in 1912. Wegener proposed that the continents slowly drift across Earth's surface. Although this idea was not new, the development of better maps by the early 1900s suggested to Wegener that the shapes of matching shorelines on different continents suggested that the continents moved or drifted over geologic time. Several lines of evidence supported the idea of continental drift, namely: matching sequences of rocks and mountain chains; glacial ages and other climate evidence; and the distribution of organisms, including extant organisms and fossilized remains. The main objection from the scientific community centered on the mechanism that Wegener proposed for the movement of continents: gravitational attraction and tidal forces.
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How might the presence of life on another planet be inferred from the composition of that planet's atmosphere?
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Cirrostratus clouds followed by altostratus
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Each of the three population pyramids (above) are census tracts from St. Louis County in northern Minnesota, that stretches from Duluth to Canada. The population pyramid on the left most likely represents
A) a rural population with high out-migration after high school. B) an urban population with a high number of immigrant workers. C) the part of the county with the University of Minnesota-Duluth in it. D) a retirement community on the border with Canada. E) The median census tract, where all the women are strong, the men are good-looking, and the children are above average.
The acquired immune cells that target pathogens in infected cells are
A) B cells. B) T cells. C) antibodies. D) antigens.