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There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans or into a separate species of their own. Most DNA sequence data analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept is most applicable in this example?

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of

Dogs (Canis lupus familiaris) and gray wolves (Canis lupus) can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time) and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species?

Figure 20.3In Figure 20.3, phylogeny branch lengths represent genetic changes. Which organism on the tree has undergone the most genetic changes since divergence from common ancestor?

Figure 20.4Extrapolating backward in time using the molecular clock indicates that the HIV-1 M strain originated around

Which of the following will produce the greatest increase in blood pressure?  

Which type of tissue is most likely to repair itself if injured?

Which of the following represents a segment of RNA?

Which type of tissue conducts electrochemical impulses via cells called neurons?

Due to the cast placed on her broken leg, Kinsley’s muscles have decreased in size. Which term best describes how her muscles have been affected?