An organ that is hygroscopic
(a) is sensitive to changes in moisture.
(b) is exemplified by the peristomal teeth in the sporophyte of mosses.
(c) may aid in spore dispersal in mosses.
(d) is all of the above.
(d) is all of the above.
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After some time, the tip of a plant that has been forced into a horizontal position grows upward. This phenomenon is related to _____
A) calcium release from the endoplasmic reticulum of shaded cells B) whether the plant is in the northern or southern hemisphere C) gibberellin production by stems D) auxin production in cells receiving red light E) auxin movement toward the lower side of the stem
In an experiment similar to that performed by Shatkin and colleagues, a student synthesized mRNAs such that 32P-GTP was incorporated; 7-meG labeled with 3H was used to cap the mRNA
A fraction of the sample was run on a gel and confirmedthat radiolabeled capped transcripts had indeed been produced. The remainder of mRNA was incubated with wheat germ cell extract to allow binding to ribosomes. The sample was deposited at the top of a sucrose density gradient and spun in a centrifuge. Surprisingly, neither label comigrated with the ribosome fraction; the ribosomes did migrate as expected. What is the most likely reason for this result? A. The ribosomes did not incorporate the 3H label. B. The sucrose gradient was not made correctly. C. The wheat germ was contaminated with guanylyltransferase. D. The wheat germ was contaminated with RNase E. The centrifuge did not spin at the correct speed.
Which of the following is a possible advantage for the environment of having farmers use plants that genetically produce Bt toxin?
A) Plants with genes for the toxin are eaten less often by insects, and therefore less insecticide is needed. B) Plants that produce Bt toxin must be grown from new seeds each season, and therefore fewer of them are planted. C) Bt toxin is advantageous to many species of invertebrates that grow in the same fields. D) Harvesting plants with these genes is less disturbing to the soil layers where they are planted. E) Plants with these genes must be sprayed with the organism, but need much less than other plants.
In a reflex arc, the correct sequence of cell types through which an electrical signal would pass would be
A. motor neuron ? sensory neuron ? interneuron in the PNS B. sensory neuron ? motor neuron ? interneuron in the CNS C. sensory neuron ? interneuron in the CNS ? motor neuron D. motor neuron ? interneuron in the PNS ? sensory neuron