The first living cells emerged approximately how many years ago?
a. 100 million
b. 500 million
c. 1 billion
d. 2 billion
e. 4 billion
ANSWER: e
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Indicate whether the statement is true or false.
As light levels increase, some electrons from photosystem I are redirected from ____ back into the electron-transport chain
Fill in the blank with the appropriate word.
The impact of a large meteorite with Earth would have most likely caused mass extinctions by
A. creating large clouds of dust that blocked out sunlight and destroying plant life. B. causing a great prolonged rise in the earth's temperature and destroying plant life. C. destroying plant life on Earth. D. creating large clouds of dust that blocked out sunlight.
During exercise, the skeletal muscles receive
__________ blood, the brain receives __________ blood, and the gut receives __________ blood than at rest. a. more; the same amount of; less b. more; less; less c. the same amount of; the same amount of; less d. the same amount of; the same amount of; more e. less; more; less