Q17 - If one of the effects

[geverett]

Couldn't figure this out. Does the phrase "then and only then" create a bi-conditional?

[timmydoeslsat]

Couldn't figure this out. Does the phrase "then and only then" create a bi-conditional?

Indeed it does!

These are just a bunch of statements. We are given a must be false question.

The stimulus:

One of the effects of genetic mutation makes substantial contribution <---> Mutation favored in natural selection

You can use the bi conditional arrow in this case, meaning it goes both ways. This means that you cannot have one without the other. If we have a case of NOT one of those variables, then the other one cannot occur. They both need each other.

The other statement in the stimulus is not something I would diagram, rather internalize in my head, which in this case, is common sense. The favored trait, that brings along with it negative traits if necessary, cannot have those negative traits cancel out this favored trait.

Answer choices:

A) A species could possess a trait that has effects that are all neutral for the survival of its species. That would just mean that there would be no favor-ability in natural selection for those traits. This is not something that has to be false.

B) I think of some SUPER DUPER creature here! But the stimulus does not preclude this possibility. It could be possible that all of the effects of genetic mutation contribute substantially to the survival of the species.

C) Sure this is possible. The great trait that is favored has with it bad traits, just as long as it is not canceling out what this trait does.

I think of this idea in an easy to see way:

Trait A: Mutated as to contribute to survival of the species by making lungs invincible to pollution. However, other traits in this species has been dragging down the species for a while, which is that its eyes go blurry for 30 mins every 2 hours. It is an annoying occurrence, but it does not interfere with the impermeability of those lungs.

D) Identical to C.

E) Could this happen? A genetic mutation whose effects are all neutral to a species that is favored in natural selection.

What happens when we have a situation of a mutation being favored in natural selection....I placed the stimulus below as a reminder!

One of the effects of genetic mutation makes substantial contribution <---> Mutation favored in natural selection

It brings about a necessary condition of there being at least one effect that makes a substantial contribution.

Since this answer choice says the effects are all neutral, then it cannot be favored in natural selection.

This must be false.

[yihannah90]

What are some other bi-conditional indicators besdies "if and only if" and "vice versa"? Thanks!

[ManhattanPrepLSAT1]

Here are some of the most common language cues indicating biconditionality:

if, and only if
when, and only when
then, and only then
if, but only if
all and only

[jake.jh.park]

Just a quick issue about answer E.

The answer E says
:A genetic mutation whose affects are all neutral to a species is favored in natural selection.

And as like in the stim:
GM -> favored in NS-> must not be negative as to annul the benefits of having the new favored trait.

So, the answer E (GM -> all neutral) cannot be true because GM -> must not be negative (which means it can be positive whatever) as to annul..

[ohthatpatrick]

I'm not sure if you were asking a question or offering your own take on (E).

One rule we can derive from the stimulus is

If NONE of the effects of a genetic mutation make a substantial contribution to the survival of the species, then that mutation will NOT be favored in natural selection.

(E) talks about a mutation whose effects are all neutral. So NONE of its effects make a substantial contribution. So that mutation will NOT be favored in natural selection.

Hence, (E) must be false.

[roseleec0729]

I'm having trouble understanding this question..
This is MBF question and before I raise a question i want to make sure the formula that i know!

If A->B condition is true,

MBF condition is A->~B
CBT conditions are some B->~A
some ~A->B
all ~A->~B or all B->A

In first sentence, you can make conditional like this: substantial contribution<->favored

(E) says: ~substantial contribution-> favored
How can this be MBF? Is it just CBT statement?