What is the reason for the prevalence of the sickle-cell allele in African populations?
A) Heterozygotes have some resistance to the parasite that causes malaria.
B) Sickled cells are better able to clot blood.
C) African populations tend to be at higher altitudes, and sickled cells better bind oxygen in these environments.
D) Sickled cells help prevent vitamin A deficiency among African populations.
A
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For many years, biologists felt that the highest level of classification of living organisms was the five kingdoms. Recently, some biologists have proposed that the hierarchical classification of organisms start with three domains, the Bacteria, the Archaea, and the Eucarya. Explain the reasoning behind this proposal and why the Bacteria and the Archaea should be in separate domains even though
their members are all prokaryotes. What will be an ideal response?
Genes with large numbers of _____________ base pairs are more likely to have a higher mutation rate
than genes with large numbers of ___________ base pairs. Fill in the blank(s) with the appropriate word(s).
How does an increase in atmospheric greenhouse gases increase global temperatures?
A) By preventing some of the heat from escaping the planet's surface B) By decreasing the ozone layer in the atmosphere C) By increasing the amount of heat from the sun that reaches the planet's surface D) By reacting with each other
Which of the following observations are expected if an infectious disease were a contributor to amphibian decline?
a. Amphibian decline occurs simultaneously at many points throughout the entire range of am-phibian populations. b. Amphibian decline correlates with habitat alteration. c. Individuals from nondecline populations that are transplanted into in-decline populations show the same symptoms as in-decline individuals. d. Symptoms of in-decline individuals can be cured by medication in the lab. e. C and D.