The rate of flow of water through the xylem is regulated by
A. passive transport by the pith
B. The force of transpirational pull
C. the number of companion cells in the phloem
D. active transport by the sieve tube members
E. active transport by tracheid and vessel cells
Ans: B. The force of transpirational pull
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Arrange the following levels of geological eras in the correct order. Write the letter of the oldest period
next to 1 and the letter of the newest period next to 10.
A. Triassic B. Permian C. Archaean D. Cretaceous E. Devonian F. Cambrian G. Silurian H. Jurassic I. Ordovician J. Carboniferous 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Without _____, humans might have a tail.
A. differentiation B. epigenetics C. cell migrations D. apoptosis E. the maternal gene effect
Which of the following observations were an outcome of studies by David Tilman and coworkers at Cedar Creek, Minnesota on ecosystem stability? (Check all that apply.)A) Plots with more species showed less year-to-year variation in biomass.B) Species-rich plots were less affected by drought than species-poor plots.C) Over-yielding was observed in more recent work at Cedar Creek.D) Nitrogen uptake and total biomass produced were negatively correlated to species richness.E) More diverse plots were less susceptible to invasion by new species.
What will be an ideal response?
Which of the following terms describes bacteriophage DNA that has become integrated into the host cell chromosome?
A) intemperate bacteriophages B) transposons C) prophages D) T-even phages E) plasmids