The human spine acts like a weight-bearing column. Compare this to the spine of a horse, which acts like an elastic suspension bridge. Which organism would you predict to experience more back pain and why?
A) the horse, because its spine is less evolutionarily advanced
B) the horse, because its spine supports more organ systems than a human's spine supports
C) the human, because in order to walk upright, the human spine must be compressed
D) the human, because the human spine has longer neurons
Answer: C
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a. live together for generations and have a reproductive division of labor b. typically display altruistic behavior c. nest in colonies but live separately the rest of the year d. associate with others of their species only for breeding
A normal urinary system consists of
a. two urethras. b. two ureters. c. two bladders. d. one kidney. e. all of these
In the mitochondria pyruvate molecules are converted into ____________________ molecules, which can enter the
Krebs cycle reactions. Fill in the blank(s) with the appropriate word(s).
Nicotine from cigarette smoke acts as a ligand and associates with specific cells in the nervous system. Nicotine eventually produces feelings of pleasure and well-being. Below are the events that happen in the cellular response to nicotine. Place the events in the correct order to describe the steps in the signaling pathway.
A. The acetylcholine receptor is an ion channel, and, when a ligand binds, the ion channel opens. B. An influx of ions carries the signal to the reward areas of the brain. C. Nicotine binds to the transmembrane protein that normally binds the neurotransmitter acetylcholine. D. The signal causes release of dopamine in the brain, which causes good feelings. E. Nicotine is quickly eliminated from the body (causing cravings for more cigarettes to produce good feelings). a. Nicotine is quickly eliminated from the body (causing cravings for more cigarettes to produce good feelings). b. A, D, B, C, E c. B, A, C, D, E d. C, A, B, D, E e. C, D, B, A, E