__________ moves food down the esophagus and through a __________ (a ring of muscle that can
close off an opening) into the stomach. Fill in the blank(s) with the appropriate word(s).
Peristalsis; sphincter
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What statement about biochemical pathways is correct?
A) All enzymes in the pathway catalyze the same reaction. B) If an enzyme in a pathway is inactive, adding excessive amounts of its substrate will restore the normal phenotype. C) If an enzyme in a pathway is inactive, adding excessive amounts of its product will restore the normal phenotype. D) If the enzyme that catalyzes the final step in a pathway is inactive, all the other enzymes will be inactivated as well. E) If the first enzyme in a pathway is inactivated, adding the final product will not restore the normal phenotype.
Nonsense codons are
A) codons that code for multiple amino acids. B) codons that do not code for an amino acid. C) codons that can be read forward or backward. D) start codons.
Which of the following statements is not true about natural selection?
a. Offspring of individuals that are better adapted will make up a larger proportion of the next generation. b. Natural selection directs evolution by preserving traits acquired during an individual's lifetime. c. Natural selection depends on the genetic variability in a population, which arises through mutations. d. Natural selection acts to preserve favorable traits and eliminate unfavorable traits. e. Natural selection leads to adaptive evolutionary change.
The left ventricle has a more muscular wall than the other three chambers of the heart because the left ventricle
A) must generate enough blood pressure to pump blood into the aorta and throughout the body. B) pumps blood more rapidly than the other chambers. C) pumps blood into the atria. D) must decrease the amount of pressure on the blood so it can flow more smoothly. E) receives blood directly from major arteries.