Consider the example of sickle cell anemia and the allele for sickle cell trait and answer questions 1-3.

1. Eventually, natural selection will usually result in the sickle cell allele becoming fixed in the population. .

2. Selection at this locus is an example of disruptive selection.

3. Hypothetically, if recessive homozygotes had the highest fitness (i.e., selection was directional) of the three genotypes discussed in the text, then natural selection would lead to fixation of the sickle cell allele.

4. If evolution occurs in a population, then the allele frequencies in that population must have changed.

5. Fermentation produces an amount of energy equivalent to that of respiration because both processes achieve the complete oxidation of carbon compounds to CO2. 6. Natural selection is not involved in adaptive radiation.

7. Many antibiotics that target protein synthesis in bacteria are ineffective against archaea.

8. Farmers plant soybeans to regenerate nitrogen nutrients in soils because soybean roots have nodules that can fix nitrogen.

9. Chemoautotrophy is an exclusively prokaryotic metabolism.

10. Although the gene encoding the small subunit of ribosomes was used to generate the universal tree of life, many genes are inappropriate choices for this analysis because horizontal gene transfer has occurred for billions of years between humans. ancestors that give rise to the three domains.