In general, there is about a ______ percent loss of energy as we proceed from one trophic level to the next higher level.
A. 90
B. 80
C. 60
D. 50
A. 90
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In vertebrates, the main function of the urinary
system is to
a. rid the body of excess water. b. rid the body of unwanted solutes. c. conserve excess water. d. rid the body of excess water and unwanted solutes. e. do none of these
What is the free energy change for the inward movement of calcium ions into the bacterial cell?
A cell biologist interested in the transport of calcium ions (Ca2+) across the plasma membrane of bacterial cells made the following measurements on bacterial cells at 25°C: Vm = ?150 mV [Ca2+] outside = 20 mM [Ca2+] inside = 0.4 mM A) +4.6 kcal/mol; an endergonic reaction B) +4.6 kcal/mol; an exergonic reaction C) ?9.2 kcal/mol; an endergonic reaction D) ?9.2 kcal/mol; an exergonic reaction E) +9.2 kcal/mol; an exergonic reaction
Which of the following could result in the most serious type of mutation?
A. A nucleotide substitution in an exon. B. A nucleotide deletion in an exon. C. A nucleotide insertion in an intron. D. A nucleotide substitution in an intron. E. More than one of these would be most serious.
Macromolecules that are used by most organisms to store hereditary information are called:
A. transfer RNA molecules. B. proteins. C. messenger RNA molecules. D. DNA molecules. E. ribosomal RNA molecules.