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Pleased with the results, the research advisor suggests it’s time to follow-up on this work and gather more evidence.

Which experiment below was most likely suggested by the advisor to advance the coughing frog’s speciation?

The Coughing Frog

Use the passage below, as well as the original reading, to answer this question.

Scientists use a number of pieces of evidence to determine if an organism should be classified as its own species. These pieces of evidence almost always include making comparisons between the new organism and other species who are similar to the new organism. One such comparison can be made by looking at DNA sequences between organisms, scientists can not only determine species origin, but they can also determine how closely related species are and gather knowledge about an organisms evolutionary history.

The doctoral student has drawn blood samples from each of five organisms: The coughing frog, a Northern Leopard Frog, a Southern Leopard Frog, the American Bullfrog, and a chicken. Using the latest in automated techniques, he sequenced DNA from an area in the first chromosome from each organism. Using a sophisticated database, he was able to compare the sequences of each of the species to the others. The goal of the comparison was to show the per cent homology (likeness) between the sequences. The results of the comparison are shown in the chart below:

Per Cent Homology between DNA Sequences Taken From Chromosome #1 Blood Samples

Organism Coughing Frog NOrthern Leopard Frog Southern Leopard Frog Bullfrog Chicken
Coughing Frog 100 92 88 70 14
Northern Leopard Frog 92 100 93 74 16
Southern Leopard Frog 88 93 100 72 18
Bullfrog 70 74 72 100 21
Chicken 14 16 18 21 100

Do more homology experiments comparing the coughing frog DNA chromosomes with the chicken DNA to see how closely related they are.


Test other areas of the coughing frog DNA chromosome with the other frog species DNA to see how closely related they are.


Repeat this experiment with other chromosome’s DNA with these organisms to see if the results can be duplicated.


Both Choices 'A' and 'C' would be sound scientific approaches.

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