Final answer:
Model organisms such as yeast and worms are used in molecular biology to understand evolutionary conservation, while mice and fruit flies are key for genetic manipulation. Yeast is also valuable for studying sexual reproduction, providing insights into biological processes related to fitness and adaptation. The correct option is A.
Step-by-step explanation:
Model organisms play crucial roles in molecular biology studies due to their simplicity and the ease with which they can be manipulated. They help scientists understand biological processes that may be similar in more complex organisms, including humans.
Yeast and worms, like Saccharomyces cerevisiae and Caenorhabditis elegans, demonstrate evolutionary conservation, meaning that many of their biological processes are preserved across different species, including humans.
Mice (Mus musculus) and fruit flies (Drosophila melanogaster) are critical for genetic manipulation studies; their genomes have been extensively studied and manipulated, allowing insights into genetics, development, and disease. Mice, being mammals like humans, are especially useful for studying diseases such as obesity and its related complications.
Model organisms like yeast are also useful for studying complex phenomena, such as sexual reproduction, which is evolutionarily expensive and complex compared to asexual reproduction. Yeast can provide insight into why sexual reproduction may be favored despite its costs through the study of fitness and mutations in varying environmental conditions.