Jonas Salk's polio vaccine trials of 1954 involved giving placebos to 201,229 children and the polio vaccine to 200,745 children
Out of the placebo group, 142 children developed polio, whereas 57 children from the vaccine group developed polio. Approximately how many more times likely was a child to develop polio if he or she were NOT vaccinated?
A) thirty
B) ten
C) five
D) three
D
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Which wetland type is known for low pH?
A) fringe wetlands B) mires C) bogs D) bottomlands
What regulates the flow of water through the xylem?
a) the number of companion cells in the phloem b) passive transport by the endodermis c) the evaporation of water from the leaves d) active transport by sieve-tube members e) active transport by tracheid and vessel elements.
All of the following could result in an increase in the genetic variety within a gene pool except
A. mutation within the gene pool. B. migration of individuals into the gene pool from other subspecies. C. sexual reproduction with individuals of other gene pools. D. selective breeding that creates individuals with specific sets of characteristics.
What are nutrients that the human body requires in large quantities?
What will be an ideal response?