
Concept explainers
Changes in the Air To assess the impact of human activity on the carbon dioxide level in Earth's atmosphere, it helps to take a long view. One useful data set comes from deep core samples of Antarctic ice. The oldest ice core that has been fully analyzed dates back a bit more than 400,000 years. Air bubbles trapped in the ice provide information about the gas content in Earth's atmosphere at the time the ice formed. Combining ice core data with more recent direct measurements of atmospheric carbon dioxide—as in FIGURE 46.20—can help scientists put current changes in the atmospheric carbon dioxide into historical perspective.
FIGURE 46.20 Changes in atmospheric carbon dioxide levels (in parts per million). Direct measurements began in 1980. Earlier data are based on ice cores.
The industrial revolution occurred around 1800. What was the trend in carbon dioxide level in the 800 years prior to this event? What about in the 175 years after it?

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Chapter 46 Solutions
Biology: The Unity and Diversity of Life (MindTap Course List)
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- HAND DRAW There should be two proarrow_forwardMolecular Biology Question. Please help solve. Thanks. Please draw how two nucleotide triphosphates are linked together to form a dinucleotide, and label the 5' and 3' ends of the resulting dinucleotide.arrow_forwardWhat is a reversion in molecular biology?arrow_forward
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- 24) Use the following information to answer the question below. Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. The dominant allele (T) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined (see table) and used to determine the actual allele frequencies in the population. TT 0.49 Tt 0.42 tt 0.09 Refer to the table above. Is this population in Hardy-Weinberg equilibrium? A) Yes. C) No; there are more homozygotes than expected. B) No; there are more heterozygotes than expected. D) It is impossible to tell.arrow_forward30) A B CDEFG Refer to the accompanying figure. Which of the following forms a monophyletic group? A) A, B, C, and D B) C and D C) D, E, and F D) E, F, and Garrow_forwardMolecular Biology Question. Please help with step solution and explanation. Thank you: The Polymerase Chain Reaction (PCR) reaction consists of three steps denaturation, hybridization, and elongation. Please describe what occurs in the annealing step of the PCR reaction. (I think annealing step is hybridization). What are the other two steps of PCR, and what are their functions? Next, suppose the Tm for the two primers being used are 54C for Primer A and 67C for Primer B. Regarding annealing step temperature, I have the following choices for the temperature used during the annealing step:(a) 43C (b) 49C (c) 62C (d) 73C Which temperature/temperatures should I choose? What is the corresponding correct explanation, and why would I not use the other temperatures? Have a good day!arrow_forward
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