Plant cells often have a large membrane-bound sac that is used for storing water and other substances. This organelle is called:
A. centriole
B. chloroplast
C. nucleus
D. central vacuole
E. Golgi body
D. central vacuole
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Researchers tested nitrogen loss from soil where the moss Dawsonia was growing, and compared it to soil from which Dawsonia had been removed. The data are presented below
Researchers decided to test the hypothesis that if the 1-meter-tall Dawsonia gametophyte-sporophyte plants had acted as a physical buffer, then they would have reduced water's ability to erode the soil and carry away its nitrogen. They began with four equal-sized areas where Dawsonia mosses grew to a height of 1 m above the soil surface. One of the four areas was not modified. In the second area, the mosses were trimmed to a height of 0.5 m above the soil surface. In the third area, the mosses were trimmed to a height of 0.25 m above the soil surface. In the fourth area, the mosses were trimmed all the way to the ground, leaving only the rhizoids. Water, simulating rainfall, was then added in a controlled fashion to all plots over the course of one year. The figure below presents four graphs that depict potential results of this experiment. In the figure above, which graph of soil nitrogen loss over time most strongly supports the hypothesis that if the 1-m tall Dawsonia gametophyte-sporophyte plants had acted as a physical buffer, then they would have reduced water's ability to erode the soil and carry away its nitrogen? A) A B) B C) C D) D E) None of these graphs support the hypothesis.
The notochord has a similar function to the
a. nervous system. b. spinal cord. c. skeletal system. d. skin system. e. muscle system.
There is no matrix in blood because it is a liquid.
Answer the following statement true (T) or false (F)
You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells
The Gprotein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? (a) addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive (b) addition of a drug that prevents GTP hydrolysis by G? (c) addition of a drug that activates adenylyl cyclase (d) addition of a drug that mimics the ligand ofERC1