Final answer:
If two organisms do not share many amino acid sequences, they are less related to each other. Similarity in these sequences indicates a more recent common ancestor and closer evolutionary relationship. Molecular differences in amino acids and DNA provide insight into phylogenetic relations and evolutionary history.
Step-by-step explanation:
If two organisms do not have many of the same amino acid sequences, they would be less related to each other. The similarity in the sequences of amino acids can reveal how closely related two species are assumed to be. In essence, the more similar their sequences, the more recent their common ancestor. When comparing organisms such as a mammal to a bird, a mammal to a frog, and a mammal to a fish, the mammal and bird would likely share more differences in DNA and amino acid sequences compared to a mammal and a frog, or a mammal and a fish. This is because birds are more closely related to mammals due to being warm-blooded, among other characteristics, while frogs and fish are more distantly related as they are cold-blooded and have significant physiological differences.
During the process of evolution, DNA and amino acid sequences accumulate changes. These molecular differences provide a record of the evolutionary history and can be used to infer phylogenetic relationships. For example, humans and chimpanzees have almost identical cytochrome c protein sequences, indicating a recent common ancestor, whereas human and yeast comparisons show significant differences, indicating a more distant common ancestor.
A critical point is that molecular biology provides genetic similarities reflective of evolutionary lineage, which are believed to be less influenced by natural selection and hence offer a more accurate reflection of ancestry than other morphological traits. However, it is also important to consider that in some cases, organisms with vastly different appearances may still be closely related if they've diverged more recently in evolutionary terms. This underlying genetic connection might be indicated by similarities in DNA or protein sequences. On the other hand, 3D structures of proteins are conserved and might suggest relatedness even when there are differences in the underlying amino acid sequences.