What findings are consistent with an asteroid impact as a cause for the K–T mass extinctions?
a. Ammonites showed elevated extinction rates prior to 65 MYA.
b. Dramatic pollen increases coinciding with the iridium spike in geological layers.
c. Geological data suggest a period of global warming around 65 MYA.
d. A decline in planktonic fossils around 65 MYA that is stronger but similar to a decline of ma-rine productivity caused by a historic volcanic eruption.
e. B and D.
D
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Scientists have determined that the silversword alliance is most closely related to the tarweed based on
a. phylogenetic similarities. b. molecular comparisons. c. the ability of the two plants to interbreed. d. their geographical closeness. e. seed shape and color.
Most of Earth's water resides in
A) the oceans. B) the polar ice caps and glaciers. C) freshwater lakes, ponds, rivers, and streams. D) groundwater.
The MOST prevalent cation of the extracellular fluid is:
A) sodium. B) chloride. C) potassium. D) bicarbonate.
What accounts for the ability of vesicles to fuse with different membrane compartments in the cell?
A. the cell's cytoskeleton B. the fluid nature of the phospholipid bilayer C. peripheral membrane proteins D. transport proteins