Biochemical techniques can be used to determine how closely organisms are related to each other by comparing the similarities and differences in their molecular structures, such as proteins and nucleic acids (DNA and RNA).
One common biochemical technique used to determine relatedness is molecular sequencing, where the DNA or RNA of two or more organisms is compared to identify similarities and differences in the sequences of their nucleotides. If two organisms have a high degree of similarity in their nucleotide sequences, it suggests that they are closely related and may have diverged more recently from a common ancestor. Conversely, if two organisms have significant differences in their nucleotide sequences, it suggests that they are more distantly related and may have diverged from a common ancestor further in the past.
Another technique that can be used is immunological analysis, where the similarity between the protein structures of different organisms is compared by examining how their immune systems respond to each other's proteins. If two organisms have similar protein structures, their immune systems may not recognize each other's proteins as foreign, and may not produce an immune response. Conversely, if two organisms have significantly different protein structures, their immune systems may recognize each other's proteins as foreign and produce an immune response.
Overall, by comparing the biochemical structures of organisms, scientists can gain insights into their evolutionary history and relationships, which can inform our understanding of the diversity of life on Earth.