If the 14C to 12C ratio present in a fossil is 25% of that in living organism, how many years have passed since this
fossilized organism died?
a. 1,432
b. 2,865
c. 5,730
d. 11,460
e. 17,190
ANSWER: d
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Serratia marcescens bacteria has a gene that regulates red pigment production by cells. A student inoculates two nutrient agar plates of Serratia and incubates one at 25oC and the other at 37oC. Following incubation, the student observes that colonies on the 25oC plate are red while those on the 37oC plate are nonpigmented. Which of the following statements is a logical conclusion based on these results?
A. This is an example of constitutive gene expression. B. Serratia cells undergo a genotypic change that is proportional to changes in temperature. C. Low temperatures cause repression of certain housekeeping genes. D. Serratia genes for pigment production are induced at certain temperatures.
The period following an action potential during which a neuron cannot be stimulated to generate another action potential is referred to as
A. the refractory period. B. the threshold period. C. the resting period. D. the inactivation period. E. the critical period.
One of the science-related concerns associated with the use of genetically modified (GM) foods is that
A) overreliance on GM crops may lead to genetic uniformity. B) GM foods are not natural. C) genetic modification degrades the nutritional value of food crops. D) buffer zones of GM crops halt the pollination of non-GM crops.
Which of the following represents a reactant in the light reaction of photosynthesis?
A. oxygen B. carbon dioxide C. H2O D. NADPH E. ATP