Essential fatty acids a. are synthesized by the liver.
b.
are a necessary precursor to cholesterol.
c.
cannot be synthesized by the body.
d.
are necessary for blood clotting.

Which of the following birds remained ancient looking in the miocene epoch? a. crows b. owls c. grouses d. none of the above

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi