In the evolutionary history of the earth, Homo sapiens probably first appeared approximately ________ years ago.
A) 2,000
B) 20,000
C) 200,000
D) 2,000,000
C) 200,000
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If I wanted to sample some rapidly dividing cells in a plant, a good choice would be
____________________.
a. cells making up fibers b. cells making up wood c. guard cells d. root tip cells
Living organisms are members of all of the
levels listed below. However, soil is a component of
a. the community. b. the population. c. the ecosystem. d. the biosphere. e. both the community and the biosphere.
The receptors that detect head rotation ____
a. are located in the cochlea b. are located in the utricle c. are found at the base of each semicircular canal d. respond best to straight line acceleration e. are contained in an air-filled space
A nerve impulse is initiated when
A. a reversal in the polarized state of the cell causes it to reach action potential. B. voltage-gated channels close. C. physical disruption of the cell membrane causes some of its contents, including ions, to leak out. D. the Schwann cells move into their new position.