Conducting tubes of phloem consist of stacks of ____.
A. dead sieve elements
B. living sieve elements
C. dead vessel elements
D. living vessel elements
E. dead companion cells
Answer: B
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Dissimilatory sulfide-oxidizers use a variety of unique ecological strategies in order to
A) avoid the toxicity of hydrogen sulfide. B) position themselves at interfaces where sulfide and oxygen meet. C) position themselves where there is sufficient light for sulfide oxidation. D) find organic carbon substrates.
Which of the following statements is true regarding T cell receptors? Select all correct
A. They recognize antigen-MHC complexes. B. They contain variable and constant regions. C. They are composed of two heavy (H) chains and two light (L) chains. D. They are formed by the rearrangement of V, J, C, and D gene segments. E. They can be found in the bloodstream independent of T cells.
________ reactions require an input of energy when electrons are gained, such as in the conversion CO2 ? CH4
Fill in the blank with correct word.
Alexander Fleming kept finding mold contamination that was killing his bacterial cultures. This observation eventually lead to the development of the antibiotic penicillin. Why would a fungus produce a compound that is selectively toxic to bacteria?
A. Killing bacteria is an accident. B. Fungi are killed by bacterial toxins. C. Fungi compete with bacteria for resources. D. Fungi eat bacteria.