Explain the transpiration-cohesion-tension mechanism that acts in the xylem of plants
What will be an ideal response?
Transpiration is the net loss of water by leaves through stomates. Because water is characterized by hydrogen bonding between adjacent water molecules, it is literally "pulled" up through the xylem. Since water molecules cohere to other water molecules, and also tend to adhere to the cellulosic lining of the xylem elements, this column of water rises. This entire unbroken column of water is under tension due to the constant evaporative loss of water in the leaves.
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How does a vaccination help to prevent a disease?
A. It generates a population of B memory cells that will speed up response to an actual infection. B. It reduces the severity of symptoms to a disease. C. It established defenses that prevent a pathogen from returning to the body. D. It generates a population of plasma cells that increase the concentration of antibody in the bloodstream.
Which circumstance violates the conditions of the Hardy—Weinberg model?
a. the population is infinitely large b. the population is closed to migration from other populations c. no mutations are occurring d. all genotypes in the population survive and reproduce equally well e. nonrandom mating with respect to genotypes occurs between individuals
In general, microtubules disassemble and consequently pull the chromatids to the ends of the spindle
during ____.
a. prophase b. interphase c. anaphase d. metaphase e. telophase
Which of the following enables a virus to attach to the molecules of a host cell?
a. core b. capsid c. envelope d. glycoprotein