A scientist carried out an experiment to follow the movement of carbon atoms within animal cells. To do this, the scientist added glucose with radioactively labeled carbon atoms to a culture of cells growing in a Petri dish. After a certain amount of time had passed, the scientist tested parts of cells for radioactivity. Radioactivity was detected in various biomolecules, including DNA.

Which of the following statements best explains why radioactivity was detected in the DNA?
Choose 1

(Choice A)
The DNA was in close proximity to the radioactive glucose during its formation.

(Choice B)
Carbon atoms that were once in the radioactively labeled glucose were used to form DNA.

(Choice C)
The DNA was made up of radioactively labeled glucose subunits.

Over the past 60 years, many amphibian species have experienced significant population declines and some species have become extinct. scientists suspected that local human activities such as the destruction of wetlands, regional pollution, and deforestation were the main reasons for these losses. however, research over the past 20 years reveals significant amphibian population declines in protected areas of the world, such as nature preserves and parks. these global declines suggest widespread problems including increased ultraviolet radiation, acid rain, and disease. in switzerland, for example, 14 of the 20 native amphibian species are threatened with extinction. chytridiomycosis is a fungal disease first identified in 1998 as a cause of massive amphibian deaths. in some severely impacted populations, a few individuals have survived, perhaps because of some natural resistance. if these resistant individuals continue to survive and prosper, new resistant populations might emerge. this would be an example of the founder effect artificial selection genetic drift natural selection sexual selection

Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.

What does the hardy-weinberg principle relate to? a. chances of survival of an organism b. frequency of alleles in a population c. natural selection in a species d. causes of evolution among organisms