How do sugars move from one sieve-tube cell to the next?
A) by osmotic diffusion through the sieve plate
B) by flowing along with water through perforations in the sieve plate
C) by active transport across cell membranes at the sieve plate
D) by diffusion through a companion cell that spans the sieve plate
Answer: B
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The distribution of social animals is likely to be
a. clumped. b. random. c. uniform. d. constant. e. homogeneous.
How does one produce long-term potentiation of cells in the mammalian nervous system? Group of answer choices
a. a burst of many stimuli within a few seconds b. many stimuli spaced at exactly equal intervals over a period of minutes c. minutes of uninterrupted inhibitory stimulation d. a simultaneous pairing of an excitatory stimulus and an inhibitory stimulus
The receptors in the respiratory center are most sensitive to a small
A) increase in blood carbon dioxide levels. B) increase in blood oxygen levels. C) decrease in blood nitrogen levels. D) decrease in blood oxygen levels. E) increase in blood pH.
Alterations to the positioning of the testes in males serve the purpose of ________
A) adjusting the temperature needed for production of healthy sperm B) allowing for an erection to occur C) allowing more room for the urethra D) allowing glands to release their contents