Andrew P. Hendry and colleagues discovered that Galápagos ground-finches with small bills and ground-finches with
large bills were more common and had higher fitness than birds with bills of intermediate size, a demonstration of ____ selection
a. disruptive
b. directional
c. stabilizing
d. sexual
e. artificial
ANSWER: a
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The difference between normal hemoglobin and sickle-cell hemoglobin is in the
a. heme portion of the molecules. b. number of chains of amino acids. c. substitution of a specific amino acid for another specific amino acid. d. addition of one amino acid to the normal hemoglobin molecule. e. deletion of only one amino acid from the normal hemoglobin molecule.
What would happen to a plant that is treated with a chemical that prevents electrons from moving through the electron transport chain?
A. It could not produce NADP+. B. Water would be broken down to form oxygen at a higher rate to compensate. C. It could no longer produce CO2. D. More electrons would be available for the light harvesting array. E. It could not generate an electrochemical H+ gradient across a membrane.
What is the explanation for why B cells come in so many different types that can produce so many different antibodies?
A) B cells can regulate shape to match the antigen. B) The genome of B cells is much larger than other body cells. C) B cells can recombine their genes with T cells. D) B cells can recombine their genes with the pathogen. E) B cells have gene fragments that can shuffle or recombine.
Which of the following hormones is produced by the anterior pituitary gland that regulates the production of cortisol?
A. thyroxine B. melanocyte-stimulating hormone C. adrenocorticotropic hormone D. gonadotropic hormones E. prolactin