#18 - The flagellum, which bacteria use to swim, requires

[goingslow]

Thanks Robert!

[lsatstudent99966]

Hi there,

Would (A) be correct if it says "The evolutionary ancestors of bacteria that had only a few of the parts of the flagellum would be at a disadvantage relative to similar organisms that had all of these parts"?

I think the answer is still NO, and I have tried to identify two reasons for this:
1. The stimulus doesn't guarantee that a bacterium with all parts of the flagellum will be able to propel, it just says that this is the necessary condition for them to propel. So this revision of (A) would still be too strong and therefore unnecessary?
2. Even if we compare a bacterium with only a few parts of the flagellum (and therefore unable to swim) to an organism with all parts of the flagellum that can swim, we still can't say that the former is at a disadvantage relative to the latter? I think the mere fact that "the former does not gain a survival advantage from the flagellum part, while the latter does" does not allow us to infer "the former is at a disadvantage relative to the latter", because maybe the former has some other advantage from other body parts that the latter does not have?

Sorry for such a lengthy question...

[lsatstudent99966]

Hi there,

Would (A) be correct if it says "The evolutionary ancestors of bacteria that had only a few of the parts of the flagellum would be at a disadvantage relative to similar organisms that had all of these parts"?

I think the answer is still NO, and I have tried to identify two reasons for this:
1. The stimulus doesn't guarantee that a bacterium with all parts of the flagellum will be able to propel, it just says that this is the necessary condition for them to propel. So this revision of (A) would still be too strong and therefore unnecessary?
2. Even if we compare a bacterium with only a few parts of the flagellum (and therefore unable to swim) to an organism with all parts of the flagellum that can swim, we still can't say that the former is at a disadvantage relative to the latter? I think the mere fact that "the former does not gain a survival advantage from the flagellum part, while the latter does" does not allow us to infer "the former is at a disadvantage relative to the latter", because maybe the former has some other advantage from other body parts that the latter does not have?

Sorry for such a lengthy question...

I'm sorry, please ignore my previous post. I've revised my question below:

Hi there,

Would (A) be correct if it says "The evolutionary ancestors of bacteria that had only a few of the parts of the flagellum would be at a disadvantage relative to similar organisms that had many of these parts"?

I think the answer is still NO, and I have tried to identify two reasons for this:
1. The stimulus doesn't guarantee that a bacterium with all parts of the flagellum will be able to propel, it just says that this is the necessary condition for them to propel. So this revision of (A) would still be too strong and therefore unnecessary?
2. Even if we compare a bacterium with only a few parts of the flagellum (and therefore unable to swim) to an organism with many parts of the flagellum that can swim, we still can't say that the former is at a disadvantage relative to the latter? I think the mere fact that "the former does not gain a survival advantage from the flagellum part, while the latter does" doesn't allow us to infer "the former is at a disadvantage relative to the latter", because maybe the former has some other advantage from other body parts that the latter does not have?

Sorry for such a lengthy question...

[Adam Tyson]

I think your analysis is good, and changing the answer in that way would still not make it an assumption of the argument. Consider this, too, in addition to what you said: Another organism having many of those parts still might not be able to swim!