Which technique is commonly used to gather evidence of relatedness among species?

DNA sequencing is a technique that allows scientists to analyze the genetic material of different species. By examining the sequences of nucleotides in DNA, researchers can determine how closely related two or more species are at a molecular level. The more similar the DNA sequences are, the more closely related the species are likely to be. This method provides precise and quantifiable data that can reveal evolutionary relationships, showing not just superficial similarities but underlying genetic connections that might not be obvious from physical traits alone.

While observing morphological traits can also provide insight into species' relatedness, it can be misleading due to convergent evolution, where unrelated species evolve similar traits in response to similar environmental pressures. Studying environmental adaptations focuses more on how species respond to their surroundings rather than their genetic relationships. Classifying organisms into domains is a broader taxonomic activity that helps organize life based on fundamental characteristics but does not specifically assess the genetic links among species. Therefore, DNA sequencing stands out as the most effective and informative method for establishing relatedness among species.