According to the _____, modern humans originated in, and migrated out of, East Africa
a. haplotype data of mitochondrial DNA sequences
b. haplotype data of Y chromosome sequences
c. out-of-Africa model
d. multiregional model
e. fossil record
c
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A student complains that it makes no sense to worry about coliform bacteria in water, since we naturally possess harmless coliforms in our intestines anyway. Why do regulatory agencies worry about coliform bacteria in water supplies, then?
A. The coliforms in our intestines can sometimes turn harmful, causing intestinal infections. We need to constantly be on guard against this happening. Coliforms in water might add to this potential problem. B. Not all coliforms are harmless and symbiotic with human beings. Some may carry genes/proteins that can make them dangerous to humans. It's best to keep coliforms OUT of our drinking water, since it's difficult to identify which ones might be harmless and which ones might be harmful. C. Regulatory agencies are worried that multiple types of coliforms in water might lead to greater antibiotic resistance in the bacterial populations. They try to keep them out of water to keep antibiotic resistance levels down. D. Regulatory agencies simply need something to do to justify their existence. There is no real danger from coliforms in water supplies.
In the early 1950s, James Watson and Francis Crick ____
a. were awarded the Nobel Prize for Medicine or Physiology b. combined all of their previous research in order to explain the structure of DNA c. began to work out the structure of DNA by organizing the information about DNA that was already available d. produced X-ray diffraction photographs from highly purified DNA samples e. isolated two strains of S. pneumoniae and used them to further research the structure of DNA
Which phrase best describes "honeydew"?
a. phloem sap leaving the anus of an aphid b. phloem sap harvested as syrup c. xylem sap separated from syrup d. xylem sap forced out of the margins of leaves
One characteristic that New World monkeys have that Old World monkeys lack is
A. females have mammary glands. B. hair covering their bodies. C. binocular vision. D. prehensile tails. E. opposable thumbs.