Many of the organic compounds essential for life, such as amino acids and nucleotides, could NOT
assemble spontaneously in the presence of
a. hydrogen.
b. free oxygen.
c. carbon dioxide.
d. nitrogen.
e. argon.
B
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During the snowball earth temperatures at the equator rarely exceeded -20 degrees Celsius. Why didn't heat from the sun melt the ice?
A. The high levels of atmospheric moisture created extensive cloud cover. B. Ice reflected most of radiant energy. C. The ozone layer absorbed all the heat. D. The earth's core was cooled and kept the ice frozen.
DNA is important to a cell because
a. DNA is the cell membrane that allows nutrients to enter the cell and wastes to leave. b. DNA contains the information necessary to make all of the molecules required by the organism. c. DNA contains the information necessary for the cell to reproduce itself. d. DNA is the cell membrane that allows nutrients to enter the cell and wastes to leave, DNA contains the information necessary to make all of the molecules required by the organism, and DNA contains the information necessary for the cell to reproduce itself, e. DNA contains the information necessary to make all of the molecules required by the organism and DNA contains the information necessary for the cell to reproduce itself.
Humans have altered the nitrogen cycle by burning fossil fuels
Indicate whether the statement is true or false
Stem cells developed by inserting genes that regulate the transcription of specific genes into cells from an adult are ________ cells
A) induced pluripotent stem B) embryonic disk C) gastrula D) chorionic villi E) embryonic stem