When did the last mass extinction occur?
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a. at the beginning of this era.
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b. at the beginning of this period.
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c. at the beginning of this epoch.
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d. at the beginning of this eon.

Aneuron is stimulated with an electric pulse. the action potential is detected at a point 3.70 cm down the axon 0.0052 s later. when the action potential is detected 7.20 cm from the point of stimulation, the time required is 0.0063 s. what is the speed of the electric pulse along the axon? (why are two measurements needed instead of only one? )

Which of the following is a true statement? a. individuals evolve to have adaptations. b. individuals have adaptations that can change over time. c. individuals have traits that may or may not make them successful at reproduction. d. populations cant evolve, only individual organisms.

This is a membrane-bound, disk-shaped compartment inside chloroplasts and cyanobacteria. they are the site of the light-dependent reactions of photosynthesis.