2016年5月IB生物SL真题下载-Paper3
1. Solutions of ions, for example NaCl dissolved in water, can be used to investigate the concentration of solutes in plant tissues. After immersion in solutions of varying concentration, the percentage changes in mass of potato samples were measured. The graph shows the results.
(a) (i) Estimate the osmolarity of the plant tissue.
. . . . . . . . . . . . . . . . . . . . . . . moles dm–3
(ii) Identify which part of the graph represents samples measured in a hypotonic solution.
(iii) State one possible source of error when collecting data during this experiment.
(b) Ions move across the plasma membrane of a neuron during an action potential.The oscilloscope trace shows voltage changes generated in a neuron during three action potentials.
Explain the movement of ions which causes the voltage changes observed during the interval labelled X on the graph.
2. Over 50 years ago, Meselson and Stahl investigated the mechanism of DNA replication. They transferred a rapidly growing population of Escherichia coli from a growth medium containing only 15N to a growth medium with only 14N. DNA samples were centrifuged at high speed in a salt density gradient. In the original published research, DNA molecules of the same density appear as a band in the UV absorption photographs as shown.
(a) The density of the DNA band at generation 0 is 1.724 and the density of the dark band of DNA at generation 4.1 is 1.710. Estimate the density of the DNA band at generation 1.0.
(b) Describe the nitrogen composition of the DNA band in the E. coli at generation 1.0.
(c) Explain the pattern shown in generation 3.0.
(d) This experiment was designed to demonstrate whether replication was semi-conservative or conservative. Distinguish between semi-conservative replication and conservative replication.
3. Increasing carbon dioxide concentration in the atmosphere leads to acidification of the ocean. This in turn reduces the amount of dissolved calcium carbonate. A study was undertaken to investigate the effect of increasing the concentration of atmospheric carbon dioxide on the calcification rate of marine organisms. Calcification is the uptake of calcium into the bodies and shells of marine organisms. The study was undertaken inside Biosphere-2, a large-scale closed mesocosm. The graph shows the results of the data collection.
(a) State the relationship between atmospheric carbon dioxide and calcification rates.
(b) Distinguish between the exchange of matter and energy with the surroundings in a closed mesocosm.
2016年5月IB生物SL真题余下省略！
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