Explain the pressure flow theory. What will be an ideal response?
ANSWER: The pressure flow theory provides an explanation of how osmotic pressure pushes sugar-rich
fluid inside a sieve tube from source to sink. Pressure inside a sieve tube decreases at a sink
because sugars leave the tube in this region. Sugar molecules move into companion cells
(either through plasmodesmata or by active transport), and then diffuse into sink cells
through plasmodesmata. Water follows, again by osmosis, so turgor inside sieve elements
decreases in these regions.
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Which of the following is NOT true about the Hardy-
Weinberg formula? a. It is helpful to doctors and genetic counselors. b. It can predict the carrier frequency of alleles known to cause genetic disorders. c. It can explain why some individuals absorb too much iron from their food. d. The math is useful in research on the effects of a mutant BRCA2 allele. e. It can predict that the frequency of hemochromatosis carriers in Irish populations is 0.24
Which of the following statements about radioisotopes is false?
a. The half-life of a radioisotope does not vary with temperature or pressure. b. Carbon-14 is typically used to date the rocks in which fossils are found. c. The ratio of carbon-14 to carbon-12 is used in dating fossils. d. Potassium-40 has an extremely long half-life. e. The nucleus of a radioisotope can change into that of a different element during decay
The volcanic island Selkirk arose from the North Atlantic off Iceland in 1948. The first organisms to start living there are said to be ________
A) central species B) climax species C) pioneer species D) rogue organisms
Bacteria growing at lower temperatures have more saturated fatty acids in their membranes.
Answer the following statement true (T) or false (F)