VCE Biology Question Thread

[Evolio]

Hey,
Also just wondering about a question in Insight 2017 exam question 9a)
"Scientists believe that each of the 6 modern species of finch evolved through natural selection from populations of the founder species arriving on each of the islands.
What term do scientists use to describe the emergence of these 6 species from the original founder species?"
I wrote Allopatric speciation, but the solutions say that the only answers that will be accepted is adaptive radiation or divergent evolution,
Why is this?

Hmmm, technically allopatric speciation can also be correct because there was no gene flow occurring as the finch populations were isolated from each other and they were subject to different selection pressures.
I think they accepted adaptive radiation because new species arose very rapidly in a short time frame, but is is usually associated with the time period after extinction and they didn't really give you context about extinction.
In my opinion, I think VCAA would accept allopatric speciation if this was a VCAA question.

Also, how does a new strain of virus come into existence?

Do you mean with reference to a specific disease? If so, it would be by mutation. For example, the HIV virus is an example. RNA viruses mutate more quickly than DNA viruses and that's why it is really hard to find a cure for HIV as the virus keeps mutating.

With transcription factors, is there multiple ways they can work in eukaryotic and prokaryotic cells, like binding to RNA polymerase to enable it to bind/ not bind to the promoter region, or binding to the operator region on the sequence? Do transcription factors function differently in eukaryotic cells and prokaryotic cells?

Yes, transcription factors could bind to the promoter region, the RNA polymerase itself or the operator region.
Hmm, I'm not sure about the second question.

I'm having a hard time with the experimental type questions in my practice exams. Any tips to help with this? Some of it is my lack of understanding of how to define a control in an experiment. Sometimes its to set up a baseline for an experiment, sometimes its to confirm the whether the independent variable is only affecting the dependent variable.
Any general tips on experimental design questions
thnx

What helps me is making sure that you fully understand and analyse the experiment. That way, you are easily able to identify the IV and the DV. Redoing questions you found hard is also a great way to consolidate your understanding but redoing is only helpful when you understand why your answer is wrong and why the correct answer is correct instead of memorising the correct answer and doing the question again without really understanding.
For defining a control, I usually say 'to compare the effect of the independent variable' as that's what VCAA says in their examiner's reports or sometimes I also chuck in the additional 'to act as a standard of comparison'.

I hope this helps!
Please feel free to correct me if I'm wrong!

[PhoenixxFire]

Hey,
Also just wondering about a question in Insight 2017 exam question 9a)
"Scientists believe that each of the 6 modern species of finch evolved through natural selection from populations of the founder species arriving on each of the islands.
What term do scientists use to describe the emergence of these 6 species from the original founder species?"
I wrote Allopatric speciation, but the solutions say that the only answers that will be accepted is adaptive radiation or divergent evolution,
Why is this?

This is textbook adaptive radiation. VCAA probably should still accept allopatric speciation if this was one of their questions, however there is no mention of whether gene flow is occurring between the islands or not, so you can't be sure its allopatric.

Do transcription factors function differently in eukaryotic cells and prokaryotic cells?
Thanks so much 

For the context of what you need know about transcriptions factors (ie molecules that alter the rate of transcription of genes), no. Just be aware that they bind to different spots.

I'm having a hard time with the experimental type questions in my practice exams. Any tips to help with this? Some of it is my lack of understanding of how to define a control in an experiment. Sometimes its to set up a baseline for an experiment, sometimes its to confirm the whether the independent variable is only affecting the dependent variable.
Any general tips on experimental design questions
thnx

Both of those functions of a control are the same thing just worded differently. Normally it's called a baseline if it's something that can change somewhat spontaneously over time - eg temperature - and is measured before adding the IV. It's normally called a control group if it goes through the experiment in the same way, simultaneously to the experimental group.

If you're asked to say what the control is for, then saying that it's to provide a comparison so that you know that the changes are due to the IV should be fine for the majority of questions (adapt it to the question though, eg. say what the IV is not "IV").

[Evolio]

Hi guys.
When the question asks to describe the humoral response, where do we start from?
Like do we start from the antigen presentation all the way to B memory cells and B plasma cells being produced? And, do we talk about agglutination in these types of questions?
Thank you for your help!
 

[PhoenixxFire]

Hi guys.
When the question asks to describe the humoral response, where do we start from?
Like do we start from the antigen presentation all the way to B memory cells and B plasma cells being produced? And, do we talk about agglutination in these types of questions?
Thank you for your help!
 

There isn't an easy answer to this because it'll depend on the context given in the question. If the question is "describe how humoral immunity is activated?" or something equally general, then you should include
- phagocytosis & presentation
- Th cells binding to presented antigen
- Activation of B cells by free antigens
- Co stimulation of B and Th cells
- This leading to proliferation and differentiation into memory and plasma/active cells.

^Not necessarily in that order.

On the other hand, if the question is "Describe the steps leading to antibody production" then it would be more like
- phagocytosis & presentation
- Th cells binding to presented antigen
- Activation of B cells by free antigens
- Co stimulation of B and Th cells
- This leading to proliferation and differentiation into memory and plasma/active cells.
- B plasma cells produce lots of antibodies with identical binding sites specific to an antigen on this pathogen.

Generally you don't need to talk about agglutination unless its relevant to the question specifically (eg. humoral response to a snake bite, if you're asked what the antibodies do, etc.)

[Evolio]

For example, what's the difference between question 5 a from the 2017 SAMPLE Biology Exam(5 marks) and question 4 b from the 2019 Atar Notes exam (3 marks)?

[interessant]

So, you know that Lovastin is a competitive inhibitor. Here, the HMG-CoA is the real substrate that binds to the HMG-CoA Reductase enzyme where they have a complementary shape to each other. When the HMG-CoA substrate binds to the enzyme, there is an increase in blood cholesterol.

So, you want there to be a higher concentration of Lovastin (the competitive inhibitor) so that it is more likely for the Lovastin to bind to the HMG Reductase enzyme due to successful collisions, rather than the normal HMG-CoA substrate from binding so that the cholesterol cannot be produced, thus resulting in a lower concentration of cholesterol.
You don't want the Lovastin concentration to be too low because it would be more likely for the normal HMG substrate to bind to the enzyme, resulting in cholesterol being produced and high cholesterol and we do not want that.

I hope this makes sense!
 

Thanks Evolio! Understand it now

[PhoenixxFire]

For example, what's the difference between question 5 a from the 2017 SAMPLE Biology Exam(5 marks) and question 4 b from the 2019 Atar Notes exam (3 marks)?

The AN one asks for a "brief outline" this means that you just have to mention each step, not explain it in detail. e.g. you wouldn't need to talk about how any of the activation steps work in detail.

The vcaa one asks you to "describe and explain" which means you need to include more detail about what happens in each step. e.g. rather than rather than saying "macrophages engulf pathogens and present their antigens to Th cells" you might need to say "macrophages engulf pathogens in the extracellular environment and present their antigens on MHC2 markers. Th cells that have receptors complementary to this antigen are able to bind to it and are activated".

The vcaa question also asks about the difference between a primary and secondary immune response so it's worth more marks because of that too.

[1292]

hi, when you have an experimental design question where the IV is temperature, what is the best control group to give? For like a beetroot question, if boiled beetroot was your control group, what temperate should? that be set at

[PhoenixxFire]

hi, when you have an experimental design question where the IV is temperature, what is the best control group to give? For like a beetroot question, if boiled beetroot was your control group, what temperate should? that be set at

If you're doing an experiment where you have groups set at multiple different temperatures, then you don't need a separate control group because you can compare your other groups. You only really need a set control group when you only have one experimental group. Otherwise you just attempt to control all variables other than the IV.

[Bri MT]

Otherwise you just attempt to control all variables other than the IV.

And DV - for hopefully obvious reasons but thought I'd add in case anyone was going to write this

[kaitlynbrydon]

hey,

i get confused regarding humoral and cell mediated immunity. from what i learnt this year, humoral immunity only relates to the functioning of the B cells, and cell mediated involves T cells.

what would you w rite for a question that asks 'provide an in-depth response explaining the process of humoral immunity and cell mediated  immunity?

Thanks so much

[Sconey]

i get confused regarding humoral and cell mediated immunity. from what i learnt this year, humoral immunity only relates to the functioning of the B cells, and cell mediated involves T cells.

That's more or less correct. Keep in mind T helper cells are involved in both response.

what would you w rite for a question that asks 'provide an in-depth response explaining the process of humoral immunity and cell mediated  immunity?

tbh I don't think a question like this will appear. If it does it would be at least 6 marks! But knowing the processes is important; so check out this link, I think they provide a good explanation.

http://www.vce.bioninja.com.au/aos-2-detecting-and-respond/defence-against-disease/third-line-of-defence.html

[kaitlynbrydon]

Keep in mind T helper cells are involved in both response.

How are T helper cells involved in the humoral response? apart for APCs presenting antigens to them?

thanks so much for your help

[1292]

If you're doing an experiment where you have groups set at multiple different temperatures, then you don't need a separate control group because you can compare your other groups. You only really need a set control group when you only have one experimental group. Otherwise you just attempt to control all variables other than the IV.

great thanks:)

[antigony]

Did VCAA ever end up deciding on the total ATP output of aerobic cellular respiration? The atarnotes book says 36-38 (32-34 in ETC) and that's what my teacher said too, but I read in another place that it was 32-34 and another person said 30-32 ... can anyone confirm?