VCE Biology Exam Discussion and Solutions

[smamsmo22]

Anyone else feel pretty disappointed in how they (presumably) did? I feel like the concepts I spent extra time solidifying and all the techniques I really tried to develop from doing past exams and 2017 practice papers weren't reflected in my exam at all Not having a go at the exam or anything, I just generally feel quite disconcerted with that (and my own efforts) and wanted to know how other people found it (or any advice etc).
Thanks

[casematta]

Hmmm, very true point! I'll amend the answer. Have to admit that I didn't read the question in its entirety. !

The question implies that the plasmids used are all recombinant, so the tetracycline would not have to be used in your last step. I think that instead they wanted students to see that the gene was broken and so tetracycline could not be used as both transformed and normal bacteria would both die from it. Thoughts?

[Domek]

Hi,
1. So for the question about describing the chemical reaction that occurs in the joining of amino acids (1.b)iii)), I described the process of condensation polymerisation. I talked about how the hydroxide from the carboxyl group joins with the hydrogen from the amine group of the other amino acids, to form water which is released, resulting in a peptide bond between the amino acids. It was on the study design and the question did ask to describe the 'chemical reaction'. Did anyone else do that as well and would I get some marks?
2. I said innate immunity instead of innate immune system for question 4.d)i). Is that acceptable?
3. For 7.b) would it be sufficient to say that 900 000 years ago (the age of the H. naledi fossil) Australopithecus was extinct, so it could not have been the missing link?
4. One of the ethical considerations I mentioned was discrimination of the individuals testing positive by insurance companies, especially later in their life. Is this relevant?
5. Approx. how many marks would I lose if I didn't mention ampicillin and tetracylin in my answer for 9. c)? I just kind of generally talked about an 'antibiotic' because I didn't read the question properly :I
6. For 10. f) one of controlled variables was how the temperature was kept at 30 degrees for 10 minutes and then decreased for 20 minutes, so the amount of time for each temperature would not have been the same. So the oxygen levels and carbon dioxide levels would have been different at for example 10 degrees than if it had been at that temperature for 10 minutes. What do you think?

Thanks a bunch for the solutions! They're really helpful!

[waterangel82]

Hi Guys,

I have checked Vox's answers, but I'm not sure if what I said could also potentially be okay.

1.) For SA 4e, I said that the scientists hope to find that the humans who took peptides would recover from bacterial infections much more quickly compared to those who took antibiotics.

2.) For SA 7a, I said that genus Homo would generally have a (much) shorter arm-to-leg ratio compared to Australopithecus.

3.) For SA 7b, I said that because the H.naledi appeared less that 1 mya, this means that the existed at a time when H. erectus was already around. Also, I mention how H. habilis and H. ergaster existed earlier than H.naledi, so H. naledi would not be the link. Is this sufficient for 1 mark?

4.) For SA 10a, I did quote some references in the text, but I also kind of explained more because it was 3 marks. I said something like because of the fact that the environment changed so much from the burning and excessive hunting (different selection pressures), the megafauna did not possess the favourable phenotypes to survive and pass down to offspring, so rapid extinction occurred. Would this be acceptable?

5.)  For SA 10b, I said some very general justifications, such as that the coexistence of First Australians and megafauna for 17000 years suggests that perhaps the extinction of these species were not as rapid as thought. Would this be sufficient?

6.) For SA 11e, I said that recording for 4 minutes would allow better precision and accuracy of results.

7.) For SA 11f, would controlling the temperature of the heat lamp be valid? Also, would it also make sense to say that the same type of food was given (because some foods can speed up rate of cellular respiration)?

8.) For SA 11gii, would it be valid to conclude that 'as temperature decreases, the rate of aerobic cellular respiration in the cockroach decreases' and then give the evidence to back up?

Thanks!

[vox nihili]

The question implies that the plasmids used are all recombinant, so the tetracycline would not have to be used in your last step. I think that instead they wanted students to see that the gene was broken and so tetracycline could not be used as both transformed and normal bacteria would both die from it. Thoughts?

They ask you how they can identify which ones took up the plasmid with the gene in it, so you’d have to talk about the tetracycline. 

If you read my answer in the pdf, you’ll see an explanation of how they use the tetracycline.

Hi,
1. So for the question about describing the chemical reaction that occurs in the joining of amino acids (1.b)iii)), I described the process of condensation polymerisation. I talked about how the hydroxide from the carboxyl group joins with the hydrogen from the amine group of the other amino acids, to form water which is released, resulting in a peptide bond between the amino acids. It was on the study design and the question did ask to describe the 'chemical reaction'. Did anyone else do that as well and would I get some marks?
2. I said innate immunity instead of innate immune system for question 4.d)i). Is that acceptable?
3. For 7.b) would it be sufficient to say that 900 000 years ago (the age of the H. naledi fossil) Australopithecus was extinct, so it could not have been the missing link?
4. One of the ethical considerations I mentioned was discrimination of the individuals testing positive by insurance companies, especially later in their life. Is this relevant?
5. Approx. how many marks would I lose if I didn't mention ampicillin and tetracylin in my answer for 9. c)? I just kind of generally talked about an 'antibiotic' because I didn't read the question properly :I
6. For 10. f) one of controlled variables was how the temperature was kept at 30 degrees for 10 minutes and then decreased for 20 minutes, so the amount of time for each temperature would not have been the same. So the oxygen levels and carbon dioxide levels would have been different at for example 10 degrees than if it had been at that temperature for 10 minutes. What do you think?

Thanks a bunch for the solutions! They're really helpful!

Will answer this in a tic

[landem]

I was really disappointed in this exam. Coming from someone that did 60+ exams (accelerated) I found it a bit unfair not to examine students on half of the study design topics. I was waiting for some of the traditional questions about speciation, apoptosis, vaccines etc that I knew I could smash out and instead I feel like I bombed it because I panicked 
It was unlike any exam I’ve done before and although I felt I had all the background knowledge that I needed, I found some questions really difficult when it seemed like writing was being assessed more than biology content.

The megafauna question seemed like a waste of marks when there was no SA on photosynthesis, speciation, natural selection, fossils, signal transduction, allergic or immune responses etc

[casematta]

Also, for the question about rational drug design, for two marks it is necessary to include that the drug will prevent the natural action of the molecule which it binds to from occurring. Have seen this in previous exams- definitely worth adding.

[bayliejade99]

is aerobic cellular respiration OK to say for Q11a or does it have to be cellular respiration

[vox nihili]

Hi Guys,

I have checked Vox's answers, but I'm not sure if what I said could also potentially be okay.

1.) For SA 4e, I said that the scientists hope to find that the humans who took peptides would recover from bacterial infections much more quickly compared to those who took antibiotics.

2.) For SA 7a, I said that genus Homo would generally have a (much) shorter arm-to-leg ratio compared to Australopithecus.

3.) For SA 7b, I said that because the H.naledi appeared less that 1 mya, this means that the existed at a time when H. erectus was already around. Also, I mention how H. habilis and H. ergaster existed earlier than H.naledi, so H. naledi would not be the link. Is this sufficient for 1 mark?

4.) For SA 10a, I did quote some references in the text, but I also kind of explained more because it was 3 marks. I said something like because of the fact that the environment changed so much from the burning and excessive hunting (different selection pressures), the megafauna did not possess the favourable phenotypes to survive and pass down to offspring, so rapid extinction occurred. Would this be acceptable?

5.)  For SA 10b, I said some very general justifications, such as that the coexistence of First Australians and megafauna for 17000 years suggests that perhaps the extinction of these species were not as rapid as thought. Would this be sufficient?

6.) For SA 11e, I said that recording for 4 minutes would allow better precision and accuracy of results.

7.) For SA 11f, would controlling the temperature of the heat lamp be valid? Also, would it also make sense to say that the same type of food was given (because some foods can speed up rate of cellular respiration)?

8.) For SA 11gii, would it be valid to conclude that 'as temperature decreases, the rate of aerobic cellular respiration in the cockroach decreases' and then give the evidence to back up?

Thanks!

1. Potentially ok.
2. Yes, that's fine
3. That sounds reasonable. The idea that there are lots of other species that appear to predate H.naledi really works against it being the link; you could go with that logic too.
4. That's fine but it was unnecessary. You only need to answer what you're asked.
5. I think that's fine.
6. They might accept this, but it doesn't really demonstrate that you know what you're talking about, although yuo're technically correct. I think accuracy is the more important factor here.
7. No, it wouldn't be. He uses the same protocol each time with the same lamp and we can see from the results that he graphed against the temperature anyway, so it was already controlled. Food is fine.
8. No, this is not what the graph shows. The rate of respiration is the same for every temperature below 30, it doesn't decrease with temperature according to those graphs.

The megafauna question seemed like a waste of marks when there was no SA on photosynthesis, speciation, natural selection, fossils, signal transduction, allergic or immune responses etc

There were some questions on some of these topics. The megafauna question was really an application question about natural selection. There were multiple questions on the SAQ that required knowledge of fossils, such as the megafauna and the H.naledi question. I agree that to some extent the immune system seemed fairly undersubscribed in the SAQ. This always happens with exams though, they can't ask about everything!

Also, for the question about rational drug design, for two marks it is necessary to include that the drug will prevent the natural action of the molecule which it binds to from occurring. Have seen this in previous exams- definitely worth adding.

No, this is unnecessary.

is aerobic cellular respiration OK to say for Q11a or does it have to be cellular respiration

That's perfectly fine

[waterangel82]

1. Potentially ok.
2. Yes, that's fine
3. That sounds reasonable. The idea that there are lots of other species that appear to predate H.naledi really works against it being the link; you could go with that logic too.
4. That's fine but it was unnecessary. You only need to answer what you're asked.
5. I think that's fine.
6. They might accept this, but it doesn't really demonstrate that you know what you're talking about, although yuo're technically correct. I think accuracy is the more important factor here.
7. No, it wouldn't be. He uses the same protocol each time with the same lamp and we can see from the results that he graphed against the temperature anyway, so it was already controlled. Food is fine.
8. No, this is not what the graph shows. The rate of respiration is the same for every temperature below 30, it doesn't decrease with temperature according to those graphs.

There were some questions on some of these topics. The megafauna question was really an application question about natural selection. There were multiple questions on the SAQ that required knowledge of fossils, such as the megafauna and the H.naledi question. I agree that to some extent the immune system seemed fairly undersubscribed in the SAQ. This always happens with exams though, they can't ask about everything!

No, this is unnecessary.

That's perfectly fine

Thank you  . So for 11gii, would I still be able to receive 2 marks if I mentioned that the rate of consumption/production between 10-30 minutes (and give specific figures) was slower than the rate of consumption/production between 0-10 mins (and give specific figures)?

[ShyamChandak]

Yeah Same Mr. Padlan.

[omgvce]

1. Potentially ok.
2. Yes, that's fine
3. That sounds reasonable. The idea that there are lots of other species that appear to predate H.naledi really works against it being the link; you could go with that logic too.
4. That's fine but it was unnecessary. You only need to answer what you're asked.
5. I think that's fine.
6. They might accept this, but it doesn't really demonstrate that you know what you're talking about, although yuo're technically correct. I think accuracy is the more important factor here.
7. No, it wouldn't be. He uses the same protocol each time with the same lamp and we can see from the results that he graphed against the temperature anyway, so it was already controlled. Food is fine.
8. No, this is not what the graph shows. The rate of respiration is the same for every temperature below 30, it doesn't decrease with temperature according to those graphs.

There were some questions on some of these topics. The megafauna question was really an application question about natural selection. There were multiple questions on the SAQ that required knowledge of fossils, such as the megafauna and the H.naledi question. I agree that to some extent the immune system seemed fairly undersubscribed in the SAQ. This always happens with exams though, they can't ask about everything!

No, this is unnecessary.

That's perfectly fine

Hi vox,

Could you please explain how for q11gii, the graphs don't show a slower rate of respiration as temperature falls?

As temperatures fell below 30 degrees, the rate of oxygen intake reduced and the rate of carbon dioxide production reduced as well, shown by less slopey gradients. Does this not imply a slower rate of respiration?

Thank you

[vox nihili]

Thank you  . So for 11gii, would I still be able to receive 2 marks if I mentioned that the rate of consumption/production between 10-30 minutes (and give specific figures) was slower than the rate of consumption/production between 0-10 mins (and give specific figures)?

Yes I think so. That sounds pretty reasonable.

Hi vox,

Could you please explain how for q11gii, the graphs don't show a slower rate of respiration as temperature falls?

As temperatures fell below 30 degrees, the rate of oxygen intake reduced and the rate of carbon dioxide production reduced as well, shown by less slopey gradients. Does this not imply a slower rate of respiration?

Thank you

Hey there!

To be perfectly honest, I thought this was a frighteningly difficult question, to the extent that I wonder whether VCAA will produce the right answer themselves.

If you look carefully at the graphs, on the x axis we have time and on the y-axis we have the % amount of oxygen or carbon dioxide. The rate of cellular respiration is thus given by the slope/gradient of the graph, not the y-value of the graph. A rate is a change in quantity over time...we have a quantity on the y-axis and we have a time on the x axis, therefore it's the gradient that gives us the rate in this case.

Now iwith that in ind, if we look at the graph we can see that gradient of the graph is quite steep as the temperature is kept constant at 30 degrees, but when the temperature starts to fall, the gradient falls. Critically, the gradient doesn't change as the temperature falls. This indicates that the rate of respiration below 30°C in this experiment is kept the same. So whether it's 25°C or 10°C there's no difference in the rate.

Another reasonable conclusion that could be made on the basis of those data is that the rate of respiration is highest at 30°C and lower at lower temperatures. If you say that the rate of respiration correlates with temperature though, you would be wrong. The data don't demonstrate this.

The challenge of this experiment was ditching your preconceived notions about what should happen in the system and actually just focus in on what the results of the experiment tell us. The reality is that the experiment probably wasn't that good, hence the unexpected results.

[omgvce]

Yes I think so. That sounds pretty reasonable.

Hey there!

To be perfectly honest, I thought this was a frighteningly difficult question, to the extent that I wonder whether VCAA will produce the right answer themselves.

If you look carefully at the graphs, on the x axis we have time and on the y-axis we have the % amount of oxygen or carbon dioxide. The rate of cellular respiration is thus given by the slope/gradient of the graph, not the y-value of the graph. A rate is a change in quantity over time...we have a quantity on the y-axis and we have a time on the x axis, therefore it's the gradient that gives us the rate in this case.

Now iwith that in ind, if we look at the graph we can see that gradient of the graph is quite steep as the temperature is kept constant at 30 degrees, but when the temperature starts to fall, the gradient falls. Critically, the gradient doesn't change as the temperature falls. This indicates that the rate of respiration below 30°C in this experiment is kept the same. So whether it's 25°C or 10°C there's no difference in the rate.

Another reasonable conclusion that could be made on the basis of those data is that the rate of respiration is highest at 30°C and lower at lower temperatures. If you say that the rate of respiration correlates with temperature though, you would be wrong. The data don't demonstrate this.

The challenge of this experiment was ditching your preconceived notions about what should happen in the system and actually just focus in on what the results of the experiment tell us. The reality is that the experiment probably wasn't that good, hence the unexpected results.

Oh I get you! So the rate only decreased once from a higher rate to a fixed lower rate... rather than continually decreasing as temperature decreases.

Well now I really hope vcaa doesn't take that too seriously when marking :/

Thanks for your really quick reply!

[vox nihili]

Oh I get you! So the rate only decreased once from a higher rate to a fixed lower rate... rather than continually decreasing as temperature decreases.

Well now I really hope vcaa doesn't take that too seriously when marking :/

Thanks for your really quick reply!

That’s an excellent way to summarise the point.

The question is genuinely that tricky that I’m worried they might not even know that’s the right interpretation