Biochemical analysis of tissues from two species shows many similarities. What is the most direct reason for assuming an evolutionary relationship?
The correct answer and explanation is:
Correct Answer:
The most direct reason for assuming an evolutionary relationship is that the two species have similar DNA and protein sequences.
Explanation (300 words):
Biochemical analysis involves studying the molecular composition of living organisms, particularly focusing on DNA, RNA, and proteins. When two different species show many biochemical similarities, especially in their genetic material and the proteins their genes produce, this strongly suggests that they share a common ancestor. These molecular similarities are considered the most direct and reliable evidence for an evolutionary relationship.
DNA is the hereditary material that stores genetic information. Over generations, DNA sequences can change through mutations, but closely related species tend to have more similar DNA sequences than species that are distantly related. These similarities can be observed in both coding regions (which determine protein structure) and non-coding regions (which may regulate gene expression or have other functions).
Likewise, proteins are the products of genes, and their structure and function are determined by the genetic code. If two species have very similar protein sequences, it indicates that the genes encoding those proteins are also similar. This can only be explained if the species inherited those genes from a shared ancestor.
Biochemical similarities go beyond physical traits, which can sometimes arise independently due to similar environmental pressures (a process called convergent evolution). Unlike physical traits, DNA and protein sequences provide direct insight into the lineage and mutation history of organisms. Scientists can even construct evolutionary trees, or phylogenies, based on molecular data, showing how closely related different species are.
Therefore, when tissues from two species are found to be biochemically alike, especially at the molecular level, the most direct and scientifically accepted explanation is that the species share a common evolutionary origin. These molecular markers serve as a record of descent and provide a clearer picture of how species have diverged from one another over time.