Question

Molecular data can be used to assess relationships among the major groups of living organisms whose common ancestors lived millions or billions of years ago. Similar techniques can be used to assess relationships among populations within a species. How can molecular techniques be useful for such varied comparisons?

A. Studying the relationships among different populations of a single species can be just as effective as studying the relationships of major biological groups if you look at a lot more genes.
B. The relationships between very different groups such as bacteria and whales are assessed using mtDNA sequences, whereas rRNA sequences are used for very closely related groups.
C. The same data can be used for any comparison with equal efficiency.
D. Faster-evolving gene sequences provide better data for comparisons among close relatives, whereas very slowly evolving sequences work best for distantly related taxa.

Answer 1

Molecular techniques are essential for studying relationships among living organisms, using varying rates of molecular sequence evolution to determine relationships within a species and among major groups. D. Faster-evolving sequences are used for closely related taxa, while slowly evolving sequences are suitable for distantly related groups.

Step-by-step explanation:

Molecular techniques are incredibly valuable for both studying relationships within a species and assessing relationships among major groups of living organisms.

The answer to the student's question is that different molecular sequences evolve at different rates, which makes certain ones more suitable for determining relationships depending on the evolutionary distance.

For close relatives, D. faster-evolving sequences give better data, whereas for more distantly related taxa, very slowly evolving sequences are ideal.

This is because closer relatives share more recent common ancestors, and their DNA will have accumulated fewer mutations in comparison to distant relatives whose DNA divergence happened much longer ago.

Molecular systematics uses DNA sequencing to construct phylogenetic trees, confirming earlier taxonomic classifications and detecting errors.

These phylogenies are based on the assumption that the more similar the molecular sequences between two organisms, the more closely related they are.

Databases like GenBank and analysis tools help in comparing and understanding the degree of relation between organisms by analyzing sequence homology, which is then used to infer evolutionary distances.