The assumption that there was little free oxygen in
the earth’s first atmosphere is supported by evidence
derived from the study of
a. ancient iron-containing rocks.
b. the ancient atmosphere.
c. oceanic sediments.
d. moon rocks that formed at the same time as the
earth.
e. none of these.
Answer: a
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A change in the ratio of bicarbonate to carbon dioxide concentration in the blood will
A) cause a vasodilation of systemic arterioles. B) change blood pH. C) change blood potassium concentration. D) cause a bronchodilation. E) change blood chloride concentration.
Which of the following is created as ions diffuse across membranes?
a. an electrical gradient b. an electrochemical gradient c. a chemical gradient d. a biochemical gradient
In some parts of Mexico, ________ has become a viable alternative to green plants as a primary nutrient source.
Fill in the blank(s) with the appropriate word(s).
When an action potential begins and sodium channels open, why does sodium rush into the cell? (Check all that apply.)A) The inside of the cell is negatively charged.B) The inside of the cell is positively charged.C) Chloride ions are waiting to bind to the sodium inside the cell.D) The diffusion gradient drives sodium into the cell.E) Channels use energy to move ions across the membrane whenever they are open.
What will be an ideal response?