Several hypotheses have been proposed to explain the evolutionary origin of viruses. Which of the following does NOT assume that viruses evolved from living cells?
A. Viruses evolved from macromolecules - lipids, proteins, nucleic acids, and carbohydrates.
B. Viruses evolved from plasmids that acquired genes for their own replication.
C. Viruses evolved by losing all the genetic information that is not absolutely required for reproduction.
D. The precursors of DNA genomes may have been self-replicating RNA molecules.
E. Viruses evolved from chromosomal elements.
D. The precursors of DNA genomes may have been self-replicating RNA molecules.
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A rosebush needs to increase the concentration of phosphorus in the water within its xylem. Assuming that there is plenty of usable phosphorus dissolved in the water of the surrounding soil, how can the rosebush achieve this?
A. by transporting more phosphorus across the root cortex B. by transporting more phosphorus across root hairs C. by transporting more phosphorus across the root endodermis D. by transporting more phosphorus across the epidermis of roots
Tom recently started going to the gym, where he has taken up weight lifting. Increases in his
muscle mass are due to __________.
a. cell enlargement b. cell division c. an increase in the number of cells d. all of these
Which of the following hormones promotes cell elongation in stems?
A) auxin B) cytokinin C) ethylene D) gibberellin
Which of the following intially grows from a fungal spore?
a) haploid hypha b) diploid hyphae c) haploid protonema d) diploid protonema