In comparative biochemistry, the degree of evolutionary relationship between different organisms can be determined by comparing the amino acid sequences of conserved proteins such as Cytochrome c. If human Cytochrome c differs by amino acids from chimpanzees, amino acid from rhesus monkeys, amino acids from horses, and amino acids from baker's yeast, which of the following conclusions is most valid?
- Humans share the most recent common ancestor with chimpanzees and the most distant common ancestor with baker's yeast.Answer
- BBaker's yeast evolved directly into horses and primates through the inheritance of acquired physiological adaptations.
- CThe structural similarities in Cytochrome c among these organisms are analogous features resulting from convergent evolution in identical habitats.
- DThe variations in amino acid sequences represent discontinuous morphological variations caused entirely by environmental fluctuations.
Answer
Humans share the most recent common ancestor with chimpanzees and the most distant common ancestor with baker's yeast.
The correct answer correctly interprets comparative biochemical evidence. The fewer the differences in the amino acid sequence of a universal, conserved protein such as Cytochrome c between two species, the more recently those species diverged from a common ancestor. Since human and chimpanzee Cytochrome c sequences are identical, they share the most recent common ancestor, while the large difference of 45 amino acids between humans and yeast indicates a very ancient divergence.
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Key Concept
Comparative Biochemistry as Evidence for Evolution
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