The genomes of free-living spirochaetes are larger than those living in animal hosts. Why might this be so? A. Free-living spirochetes will need to synthesize proteins to obtain or create their own food from the environment around them. Parasitic spirochetes can leech food particles from the animal host, and may not need to move towards those food particles. B. The spirochetes in animal hosts are different species entirely. As different species, they would naturally have smaller genomes. C. A smaller genome implies simplicity-the spirochetes living in animal hosts have fewer needs, so they need fewer genes. D. It isn't so-all spirochetes would have the same size genomes, since they're all the same species of microbe.

A. Free-living spirochetes will need to synthesize proteins to obtain or create their own food from the environment around them. Parasitic spirochetes can leech food particles from the animal host, and may not need to move towards those food particles.

Explanation:

Spirochetes can be free-living aerobic or facultative aerobic species that are found in sulfur-rich fresh and marine water. Some other species of spirochetes are symbiotic or parasitic and are mainly found in hindguts of termites and digestive systems of mollusks and mammals.

The spirochetes species living in the bodies of other organisms obtain their nutrition from the host and do not require the proteins involved in various steps of nutrition.

On the other hand, free-living spirochetes require the proteins involved in the process of nutrition and related activities. Therefore, the genome size of the free living spirochetes is larger than the one found in the bodies of the other organisms