The question stem says, which of the following statements most accurately expresses the conclusion drawn?

So this is a main conclusion question.

Let's identify the line that we think is a main conclusion,

and then look for the answer that best restates that line.

or in other words, necessary to the survival of life on Earth,

biodiversity does not require the survival of every currently existing species.

So right now, the very first half, beginning with while,

sounds like a concession.

Or maybe it's not concession, but just a contextual point that the author then wants to clarify.

The author's saying, look, I agree that biodiversity is necessary for life.

But then we're drilling down on this more specific issue

about whether biodiversity requires every currently existing species to survive.

And the author's saying, no, it doesn't require that.

Now let's see where the author goes.

For there to be life on Earth, various ecological niches must be filled.

So in order to have life, you have to fill certain ecological niches.

So maybe there's like carnivores, there's certain prey,

there's different parts of, I guess, the ecosystem that have to be filled.

The author continues, many niches, however, can be filled by more than one species.

And because of this last line here, that's what's making me think

that the main conclusion is this part,

biodiversity does not require the survival of every currently existing species.

The reason that seems to be the conclusion is that the author offers support for that.

If you ask the author, well, why should I think that biodiversity

doesn't require every living thing to survive?

The author would say, because many ecological niches can be filled by more than one species.

So maybe like this is one niche, and this is another niche,

and this is a third niche, and we need these to be filled.

But if more than one species can fill, let's say, these niches,

then that constitutes a reason why we don't need every single one of these species to survive.

Maybe these ones could die out, but then the niche can be filled by this species.

And maybe these ones can die out, but this niche can be filled by that species.

So that's the way that the very last line here offers support for the main conclusion,

which is biodiversity does not require survival of every currently existing species.

This part is what I'd be looking for in the answers.

Now, sometimes people are confused,

because they think that the word for here is being used like a premise indicator.

And so I've seen some people think, oh, well,

because the word for was used at the beginning of the sentence,

that made me think, like, the second half of the last sentence was a conclusion.

And also, sometimes people are fooled by the word however, and they think,

oh, well, you know, however often introduces author opinion,

and so that's why I thought can be filled by more than one species was a conclusion.

But if that stopped you from getting this question correct,

or gave you trouble on this question,

I think you have to be a lot less mechanical about these words.

The word for does not always just introduce a premise.

Sometimes the word for can be used in other ways, and that's how it's being used here.

For is essentially just the same thing as in order for there to be life on Earth.

If I say, for me to get an A, I need to study,

the word for there is just introducing the sufficient condition.

I'm just saying, if I want to get an A, then I need to study.

For me to get an A, I need to study. That means the same thing.

And the word however here, sure, traditionally,

it is a signal of where the author's argument starts to come in,

but that's not how it's used all the time.

So you have to pay attention to the meaning of the statements

in addition to these indicator words.

If you think about the meaning of the statements,

the idea that many niches can be filled by more than one species

is helping to show that biodiversity does not require every species to survive.

So when we go to these answers, I'm looking for something that means

the same thing as that bracketed part.

biodiversity does not require that all existing species continue to exist.

That's exactly right.

That is exactly what this bracketed part means,

and that is the main conclusion.

there are various ecological niches that must be filled

if there is to be life on Earth.

Now that is something the author says that matches up with this for line,

but that's not the thing the author's trying to prove to us.

That's not the main conclusion.

The author is acknowledging that,

but then telling us that more than one species can fill those niches,

and that in turn is why biodiversity does not require

that all existing species survive.

the survival of life on Earth depends upon biodiversity.

That's just a match for the very first half of the first sentence,

beginning with while,

but that's not the author's conclusion

because the author then drills down into something more specific.

The author is acknowledging,

yes, biodiversity is necessary for life.

But now let me talk about this more specific aspect of biodiversity

and what biodiversity requires, or doesn't require.

So the first half of the first line is not the conclusion,

it's really just context.

there are many ecological niches that can be filled by more than one species.

That's just a match to the premise in the very last line,

so it's not the conclusion.

And then finally, E says

Well, we don't know about any particular species

or which one is most necessary.

So E is not the main conclusion,

and it's not even supported by the stimulus.