The extinction that occurred on earth 65 million years ago was immediately followed by:
a. an increase in atmospheric oxygen levels.
b. the rise of archaea.
c. the emergence of the first non-photosynthetic organisms.
d. the rise of reptiles, including the dinosaurs.
e. the rapid divergence and radiation of modern mammals.
Ans: e. the rapid divergence and radiation of modern mammals.
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Plant hormones bind specific cellular receptor molecules that trigger gene expression responses. Which statement is correct concerning these responses?
A. Only cells lacking receptors can bind hormones. B. Only cells in the meristem can respond. C. Only cells that express the appropriate receptors can bind hormones. D. Only cells that have been previously activated can bind hormones. E. None of these choices is correct.
In alternation of generations, a diploid sporophyte goes through meiosis to form spores.
A. haploid B. tetraploid C. endo- D. diploid E. gameto-
What stage of translation occurs when ribosomal subunits and tRNAs converge on mRNA?
a. initiation b. elongation c. termination d. peptide bond formation e. elongation and peptide bond formation
A homozygous red-eyed female Drosophila mates with a red-eyed male Drosophila. What proportion of the female offspring will have white eyes?
A. 75% B. 0% C. 100% D. 50% E. 25%