Reading Comprehension

PT118 · S2 · P3 · Q17 Lichen-forming Fungi DNA

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A lichen consists of a fungus living in symbiosis (i.e., a mutually beneficial relationship) with an alga.

Topic

The evolutionary origins and classification of lichen-forming fungi, and how new DNA studies are reshaping our understanding of fungal evolution.

Framework

Old / New

Main Point

New DNA research has clarified that lichen-forming fungi are not outliers with mysterious origins, but are closely related to already-known branches of the fungus family tree, reshaping previous assumptions about both their identity and evolutionary patterns. (Most Valuable Sentence: - end of P1)

P1: Introducing Lichen Origins & New Research

We learn that lichens are a partnership between a fungus and an alga, and that their evolutionary background has been mysterious until now. Recent DNA studies have found that lichen-forming fungi are not evolutionary outliers, but are actually closely related to other familiar fungi, which explains why some lichens visually resemble mushrooms.

P2: Historical Challenges and New Technologies

The author explains why fungi, and especially lichen-forming fungi, have been difficult to classify: they're hard to separate from their symbiotic partners and lack clear physical features. In the past, this led to lichens being considered a separate group with unknown origins. However, new genetic tools have allowed researchers to analyze their DNA and place them on five known branches of the fungal family tree, and the number is likely to grow with more research.

P3: Evolutionary Implications of the New Findings

The new research challenges the old assumption that parasitic organisms naturally evolve to become more benign and mutually beneficial over time. The updated fungus family tree shows that both harmful and helpful fungi have appeared throughout evolutionary history, suggesting fungi can switch between parasitism and mutualism rather than follow a one-way evolutionary path.

17.

Which one of the following most accurately describes the organization of the passage?

explanation of the difficulty of
Bad 1st Ingredient
The final ingredient here is a great fit, so this survives the first pass. But the opening ingredient sounds more like the 2nd paragraph than like the beginning of the passage. We don't get into the "complications / difficulty" of classifying lichens until Paragraph 2.
6% picked this
definition of lichens; discussion of
Bad Last Ingredient
The final paragraph applies these new findings to an evolutionary theory, but its doesn't support the theory. "It provides evidence to help overturn the long-standing evolutionary assumption".
7% picked this
Correct
definition of lichens; discussion of
Why this is right
The last ingredient checks out (implications of research), so we read the rest. Do we start by defining lichens? Yes, that's our first sentence. Do we proceed to discuss the difficulty in classifying their fungal components? Yes, the first half of P2 does this. Do we present a resolution of this difficulty? Yes, the second half of P1 and P2 do this. Do we end with implication of the research? Yes, P3 does this. This answer is a little annoying because it skips over most of the 1st paragraph without mention, but it still ends up being the answer whose descriptions all match the passage and whose start-to-finish progression best captures the beginning-middle-end of the passage.
Skill tested: Organization · how this choice captures the passage's function is the move to repeat next time.
71% picked this
discussion of the symbiotic relationship
Bad 2nd Ingredient
The last ingredient (implications) looks good, so we check out the rest. Did the passage begin by discussing the symbiosis that constitutes lichens? Yes, 1st sentence does that. Do we then discuss how new research can distinguish parasitic from symbiotic fungi? No. We discuss how new research can disentangle the fungus from the algae, so that we can look at the specific DNA of the fungus.
11% picked this
explanation of the symbiotic nature
Trap
Bad Last Ingredient Incomplete: lacks new study's findings The last ingredient looks good at a glance (implications for evolutionary theory), but the last paragraph is saying "here are the implications of this new stuff we found out about the fungus family tree". This answer is saying the last paragraph is discussing "the implication of problems posed by the symbiotic nature of lichens". The 1st ingredient matches the 1st sentence. The 2nd ingredient matches the first half of P2. But nowhere in this answer is the second half of P1 and P2, where we announce that a new study has transcended these problems and discovered some of the info we had been seeking! And then the 3rd ingredient should be talking about the implications of that info we discovered, not implications of problems.
5% picked this

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