LR Question 22 Explanation
QUESTION TEXT: Some types of organisms originated through endosymbiosis…
QUESTION TYPE: Most Strongly Supported
FACTS:
- Some organisms originated through endosymbiosis. That is when one organism engulfs another and the engulfed organism becomes a functioning part of the new organism.
- An unusual nucleomorph has been found inside a chlorarachiniophyte.
- Two versions of a gene were found inside the nucleomorph.
- We would only expect to find one unless the nucleomorph had been engulfed.
ANALYSIS: There is a ton of scientific detail here. You do not need to understand it all. I’ll simplify the above.
FACTS: (simplified)
- Some things have been engulfed.
- This nucleomorph is unusual unless it was engulfed.
- Therefore it is strongly supported that the nucleomorph was engulfed by that long word that starts with C (chlorarachiniophyte…answer choice E.)
It is important to note that a nucleomorph is not an entire organism. It’s just a part of another organism.
___________
- Not at all supported. Nucleomorphs could be present in everything as far as we know.
- Not necessarily. A nucleomorph is just part of another organism. It might not have all of the other organism’s DNA.
- This is backwards. That long C-word organism engulfed a nucleomorph. But nucleomorphs existed before that.
- No. The nucleomorph was just an example. We have no idea what the limits of endosymbiosis are.
- CORRECT. Otherwise it would be highly unusual that the nuclearmorph has two versions of a certain gene.
More Resources for Most Strongly Supported Questions
- Intro Course lesson: This intro course lesson covers Most Strongly Supported questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers most strongly supported questions.
Quick comment on choice (B), as personally I got trapped by it:
To be honest I’m not sure if I can agree with your explanation. From what I remember having been taught, the DNA of an organism contains all of its genetic material. So, if this nucleomorph contains DNA, it does contain all the genetic material of the organism it belongs to. Not sure if we can ask ourselves whether it is all the DNA or not: as far as I know, the DNA of an organism’s cell is very well protected in its core, and the process of substances going in and out of the cell is very well regulated. I can’t imagine, therefore, that part of the DNA escapes the cell (and, even if, it would be reasonable to still call it “DNA” then).
The reason why this choice is wrong is because it does not specify that it is talking about this, specific, unusual nucleomorph from the stimulus. I understood it to mean “any” nucleomorph in the plant. Who is telling me that the plant does not itself have nucleomorphs anyway, which did not come into contact with the other organism and thereforoe do not have its genetic material? :)
You ask a good question. It is good to use outside knowledge that *everyone* would agree with, but dangerous to reason too far from outside principles. The question says that nucleaomorphs have “the remains” of another organism’s DNA and that one particular gene has two versions.
So it sounds like over time the second organism’s DNA may have been modified and now only parts of it remain. We can’t definitively conclude that the entire original DNA remains intact within the other organism.
Note: This is an old comment but I wanted to clarify the point.