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March 29, 2024, 09:12:40 am

Author Topic: Biology External Exam  (Read 6828 times)

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Bri MT

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Re: Biology External Exam
« Reply #15 on: November 02, 2020, 03:37:14 pm »
Hey everyone,

So bio is done and I really need an answer for the last question on paper 2. I am really nervous because it was worth a lot and I am reallllllyyyy sure they did not give enough information.

The question stated that the 3 time points were leading up to the speciation now, if the speciation occurred like the gene flow was in the most recent time point, it would have been parapatric speciation right? Because the population wasn’t isolated (there was still gene flow between two sub populations).

But in theory, if the speciation occurred later, the gene flow could have been fully reduced because that was the trend, making the population isolated, and the answer being allopatric speciation!

The question says the data is “leading up to the speciation event” but without knowing when the population developed reproductive isolation mechanisms, it could either be parapatric or allopatric (not sympatric because gene flow stopped between the target population and populations B and C)

Anyway,
What did you all think of that question? Am I being crazy or was there actually some critical information missing?

I haven't seen the exam question but I am going to point out that from how you've written your post it seems like regardless of whether you wrote the target answer or not you will have shown good biological thinking. Fingers crossed!

XD12345

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Re: Biology External Exam
« Reply #16 on: November 02, 2020, 03:45:45 pm »
I haven't seen the exam question but I am going to point out that from how you've written your post it seems like regardless of whether you wrote the target answer or not you will have shown good biological thinking. Fingers crossed!

Yea that’s what I’m hoping :/, but looking at the marking guide for the practice exam, the points are distributed very plainly on just “stating this” and “explaining that”, I hope I did ok.

I am very interested in seeing what other students answered, that question really confused me

Gold_Ken

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Re: Biology External Exam
« Reply #17 on: November 02, 2020, 04:33:09 pm »
Biology exam wasn't bad. It was interesting and kind of fun?


Gold_Ken

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Re: Biology External Exam
« Reply #18 on: November 02, 2020, 04:36:02 pm »
But in theory, if the speciation occurred later, the gene flow could have been fully reduced because that was the trend, making the population isolated, and the answer being allopatric speciation!

Anyway,
What did you all think of that question? Am I being crazy or was there actually some critical information missing?

Yea that's what I thought too. If we were to see future generations pass the third time point I'm sure it would have lead to allopatric speciation with niche D eventually becoming isolated from the others.

Like Bri said, I guess there is not really a right or wrong answers as long as you can justify your position?
« Last Edit: November 02, 2020, 04:37:43 pm by Gold_Ken »

XD12345

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Re: Biology External Exam
« Reply #19 on: November 02, 2020, 04:43:04 pm »
Yea that's what I thought too. If we were to see future generations pass the third time point I'm sure it would have lead to allopatric speciation with niche D eventually becoming isolated from the others.

Like Bri said, I guess there is not really a right or wrong answers as long as you can justify your position?

You have no idea how relieved I am to see that I was not the only one who thought of this! I was so worried!

Bri MT

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Re: Biology External Exam
« Reply #20 on: November 02, 2020, 04:51:38 pm »
Yea that's what I thought too. If we were to see future generations pass the third time point I'm sure it would have lead to allopatric speciation with niche D eventually becoming isolated from the others.

Like Bri said, I guess there is not really a right or wrong answers as long as you can justify your position?

I mean, (again I haven't seen the exam so kinda hard for me to predict) it could very well be the case that there is a right answer but if it's a q with lots of marks then most of those won't be for saying which type but rather communicating your understanding of the relevant biological context.

Also worth pointing out that you generally don't need to full mark exams to get the top score.


Biology exam wasn't bad. It was interesting and kind of fun?



I remember in my bio exam I saw a question on evolution of tortoises during reading time and from that I was like full hype and ready to go. Strange how exams can be really intimidating things but sometimes also enjoyable to actually do?

XD12345

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Re: Biology External Exam
« Reply #21 on: November 02, 2020, 05:04:19 pm »
Biology exam wasn't bad. It was interesting and kind of fun?

I think the biology exam was fine, I got confused by the last question on paper 2 because there are two possible ways the answer could have been argued, but apart from that it was fine.

I was kind of disappointed that there wasn’t a question on either of the two types of gametogenesis or on Mendel’s laws, I put a lot of emphasis on those while studying :(

I was so happy when I saw there was a question on DNA replication tho, I think I went into a little too much detail

Anice

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Re: Biology External Exam
« Reply #22 on: November 02, 2020, 05:16:28 pm »
so how i approached that question was that i
1. interpreted the diagram the question gave me and told what happened ant what time + what change
2. then i went on stating that it was allopatric speciation since 1. it is not sympatric speciation since sympatric speciation often occurs when a mutation (etc. polyploidy...) occurs and reproductive isolation would've occurred in approx 1 generation while teh diagram given shows gradual isolation of population D 2. it is not parapatric speciation since no necessary geographical barriers occur in parapatric speciation to absolutely stop / cease the gene flow, while the diagram given show that the gene flow ceases absolutely by wiping out the whole arrow (instead of making it thinner or sth...)

Bro i dunno if im correct or not....

Like what do u guys think?
« Last Edit: November 02, 2020, 05:19:56 pm by Anice »

XD12345

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Re: Biology External Exam
« Reply #23 on: November 02, 2020, 05:25:10 pm »
so how i approached that question was that i
1. interpreted the diagram the question gave me and told what happened ant what time + what change
2. then i went on stating that it was allopatric speciation since 1. it is not sympatric speciation since sympatric speciation often occurs when a mutation (etc. polyploidy...) occurs and reproductive isolation would've occurred in approx 1 generation while teh diagram given shows gradual isolation of population D 2. it is not parapatric speciation since no necessary geographical barriers occur in parapatric speciation to absolutely stop / cease the gene flow, while the diagram given show that the gene flow ceases absolutely by wiping out the whole arrow (instead of making it thinner or sth...)

Bro i dunno if im correct or not....

Yeah you make some great points for allopatric speciation. But for all we know, the speciation could have occurred during time period 3, or, the trend could have continued until there was no gene flow. It would have been great to know when the actual speciation event occurred. I was going to say allopatric speciation but because there was still gene flow I settled for parapatric. It could have been parpatric, of course we do not know anything about the environment of the species, but if the two niches are lets say, on other sides of a mountain, but still in the same geographic range, there could be complete blockage of gene flow between those two niches

Both types of speciation can be argued with evidence, I just shut myself off from any emotions or paranoia and thought to myself, there is gene flow, so it would not be allopatric.

Then again, not knowing when the speciation event occurred really threw things around for me.

One more thing, it is important to note that even though the population was split up into 4 niches, that (in plain terms) they are still one population. Even though it appeared that there was complete isolation, if you consider the 4 groups as one population, it was reduced gene flow, and not complete isolation. Isolation between niches: yes, isolation between populations: no
« Last Edit: November 02, 2020, 05:38:12 pm by XD12345 »

Anice

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Re: Biology External Exam
« Reply #24 on: November 02, 2020, 05:45:21 pm »
ohhh yeah that makes sense hhh
i kinda went around that point by saying it is geographically isolated with population C & D? (like i was imagining all the populations are connected by bridges and the bridge between D with C & B collapsed)

I get what u are saying with the parapatric speciation....maybe im wrong hmmm

But i still dont get it when you say two niches are on other sides of a mountain, but still in the same geographic range, there could be complete blockage of gene flow between those two niches--isnt that already a geographical barrier that makes it a allopatric isolation? (im really confused now hahahaha

Anyway, thanks for your reply :)

XD12345

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Re: Biology External Exam
« Reply #25 on: November 02, 2020, 06:24:31 pm »
ohhh yeah that makes sense hhh
i kinda went around that point by saying it is geographically isolated with population C & D? (like i was imagining all the populations are connected by bridges and the bridge between D with C & B collapsed)

I get what u are saying with the parapatric speciation....maybe im wrong hmmm

But i still dont get it when you say two niches are on other sides of a mountain, but still in the same geographic range, there could be complete blockage of gene flow between those two niches--isnt that already a geographical barrier that makes it a allopatric isolation? (im really confused now hahahaha

Anyway, thanks for your reply :)

That’s where clinal variation comes in. There would be indirect gene flow (idk if that’s the right term to use)

Basically imagine 3 populations connected by bridges

A———-B——-C

Now, there is no gene flow between C and A, but there is gene flow between B and A, that’s kind of what I thought when answering the question. Yes, there is somewhat isolation, but it’s still just one large population that is connected by reduced gene flow.

Or see it this way, a population spreads from east QLD to west QLD. Individuals in the west won’t breed with individuals in the east, but they both bread with individuals in the middle of QLD. Technically, east and west populations would be isolated from each other, yet there is still gene flow because they are still one unified population spread over a wide geographic range.

It appears everyone else settled for allopatric speciation :( which makes me think I am wrong, because yea, it makes sense if you assume that eventually the gene flow completely stops, but at that point in time, there was still gene flow.

I think I’m just gonna have to accept that I looked too much into it :(.

If the question stated,

If speciation occurred during time period 3..... it would be parapatric

But if it stated,

If speciation occurred in future time periods.... it would have been allopatric because as you said, the reduced gene flow would have eventually stopped

Anice

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Re: Biology External Exam
« Reply #26 on: November 02, 2020, 06:45:14 pm »
That’s where clinal variation comes in. There would be indirect gene flow (idk if that’s the right term to use)

Basically imagine 3 populations connected by bridges

A———-B——-C

Now, there is no gene flow between C and A, but there is gene flow between B and A, that’s kind of what I thought when answering the question. Yes, there is somewhat isolation, but it’s still just one large population that is connected by reduced gene flow.

Or see it this way, a population spreads from east QLD to west QLD. Individuals in the west won’t breed with individuals in the east, but they both bread with individuals in the middle of QLD. Technically, east and west populations would be isolated from each other, yet there is still gene flow because they are still one unified population spread over a wide geographic range.

It appears everyone else settled for allopatric speciation :( which makes me think I am wrong, because yea, it makes sense if you assume that eventually the gene flow completely stops, but at that point in time, there was still gene flow.

I think I’m just gonna have to accept that I looked too much into it :(.

If the question stated,

If speciation occurred during time period 3..... it would be parapatric

But if it stated,

If speciation occurred in future time periods.... it would have been allopatric because as you said, the reduced gene flow would have eventually stopped

Wow thanks for your explanation!!!
Now this makes sense (but i forgot to assume the 'eventually in the long term' thing so that remains a risk for me :) and my justification for not parapatric doesn't seem to be enough hhhhh)

Nah but i think as long as u justify your answer it will be marked correct :) so relax bro 

XD12345

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Re: Biology External Exam
« Reply #27 on: November 02, 2020, 07:13:37 pm »
Wow thanks for your explanation!!!
Now this makes sense (but i forgot to assume the 'eventually in the long term' thing so that remains a risk for me :) and my justification for not parapatric doesn't seem to be enough hhhhh)

Nah but i think as long as u justify your answer it will be marked correct :) so relax bro


Yea I hope I get some marks but the sample assessment marking guide has very clear mark allocations,

The Marking guide isn’t
7-provides cleat justified viewpoint 
6-Represents a viewpoint with evidence etc

It’s more like,
1 mark=recognise it’s allopatric
1 mark=explain allopatric speciation
1 mark= Use evidence to prove it as allopatric
And so on...

(That was the marking guide for the sample assessment so idk if it will be like this in the actual external exam)