HSC Biology: Answers & Discussion

[kevin217]

Graphs in science are supposed to be drawn with pencil

Just on the subject, everything in maths is supposed to be in pen right?

[stephanieazzopardi]

Just on the subject, everything in maths is supposed to be in pen right?

Yep. BOSTES specifies 'Black' pen. 

[samsam0001]

With question 26) how was the graph meant to look like? Because i found it troubling since there was no axis for the species so I had to make one myself. Also i think i stuffed it up so I couldn't infer a relationship from this graph. Such a bad exam.

[naomisirmai]

Hey Naomi do we still have a chance of scraping band 6? I know I got 14/20 for multiple choice (cries) which means I only have 4 marks left to mess up in Section 2 and 3 :O

What I think is:
- don't panic and try to guess your marks. You never know.
- take into account scaling. This years MCQs were tricky and most people will be in your position.
- wait and see! No more use panicking.

Good luck for the rest of your exams xxx

[mtse]

Haven't done HSC (so I might be wrong sorry) but from my somewhat mediocre VCE/med bio knowledge
Question 20 Answer - I'd put a C
The question is asking for the effect of a "vaccine" - vaccines are a form of artificial active immunity, i.e. it wants to stimulate the body to create its own memory B and T cells (a.k.a lymphocytes) for future use.

The other answers are wrong because:
A - T cells don't produce antibodies
B - Helper T cells activate B cells
D - technically B cells don't destroy anything - they PRODUCE antibodies which may destroy melanoma cells (but from my knowledge cytotoxic T cells are the ones that can destroy cancer cells, pretty sure antibodies are relatively ineffective because cancer cells mutate way too often for an antibody to remain specific to the cell)

[jack.wheatstone]

Hey! I'm not claiming to be an expert or anything, but couldn't the answer to question 19 have to be B?
Technically, since it is suggesting that they use the patients "own" melanoma cells in order to create the vaccine, wouldn't it be impossible for self-antigens to be present on the cancer cells and for them to still be able to fight the melanoma?

Additionally, for question 20... The question kind of could be either C or D couldn't it? Though a Vaccine generally isn't known to specifically be designed to produce lymphocytes via cellular division, technically that is what it does? Additionally, for D whilst antibodies do not directly destroy antigens, technically the production of Plasma B-Cells do produce Antibodies that are responsible for the process of killing the antigens, right? So I think the question could go both ways...

[jakesilove]

Hey! I'm not claiming to be an expert or anything, but couldn't the answer to question 19 have to be B?
Technically, since it is suggesting that they use the patients "own" melanoma cells in order to create the vaccine, wouldn't it be impossible for self-antigens to be present on the cancer cells and for them to still be able to fight the melanoma?

Additionally, for question 20... The question kind of could be either C or D couldn't it? Though a Vaccine generally isn't known to specifically be designed to produce lymphocytes via cellular division, technically that is what it does? Additionally, for D whilst antibodies do not directly destroy antigens, technically the production of Plasma B-Cells do produce Antibodies that are responsible for the process of killing the antigens, right? So I think the question could go both ways...

Hey Jack! Check out all the discussion above; it's pretty clear that Q19/20 are contentious as fuck. Basically, there are good arguments for heaps of possible answers, so no point stressing now! 

[stephanieazzopardi]

Hey! I'm not claiming to be an expert or anything, but couldn't the answer to question 19 have to be B?
Technically, since it is suggesting that they use the patients "own" melanoma cells in order to create the vaccine, wouldn't it be impossible for self-antigens to be present on the cancer cells and for them to still be able to fight the melanoma?

Additionally, for question 20... The question kind of could be either C or D couldn't it? Though a Vaccine generally isn't known to specifically be designed to produce lymphocytes via cellular division, technically that is what it does? Additionally, for D whilst antibodies do not directly destroy antigens, technically the production of Plasma B-Cells do produce Antibodies that are responsible for the process of killing the antigens, right? So I think the question could go both ways...

Yes but this could be BOSTES way of trying to trick you... B cells don't directly destroy antigens, antibodies do.

[Phillorsm]

For question 27b, I said that the mutation affects the lignin in the spiral thickenings, so it would also affect the lignin in the leaves that gives them rigidity. Was I completely off by saying this?
... Is there even lignin in the leaves to give them rigidity??

[jakesilove]

For question 27b, I said that the mutation affects the lignin in the spiral thickenings, so it would also affect the lignin in the leaves that gives them rigidity. Was I completely off by saying this?
... Is there even lignin in the leaves to give them rigidity??

Google has confirmed that there is in fact lignin in some leaves (namely, grass)

[youknowwho]

can someone please explain what on earth is ringbarking ?

[jakesilove]

can someone please explain what on earth is ringbarking ?

It's when you cut around a tree in a circle, essentially destroying the outer layer! This destroys the phloem, which is integral in the transportation of nutrients and sugars to the roots. Thus, the tree will die! (Is a sad face more appropriate?)

[youknowwho]

It's when you cut around a tree in a circle, essentially destroying the outer layer! This destroys the phloem, which is integral in the transportation of nutrients and sugars to the roots. Thus, the tree will die! (Is a sad face more appropriate?)

i chose B (decrease in water transport)   

[ehatton2016]

hey guys! Can anyone please explain why Q13 is B and not D?

[Mal08]

Hey guys

Funnily enough, I'm having the opposite anxiety, were it seems I aced multiple choice but my short responses were weaker and I have some questions.

1) For the graph, I was an idiot and did the scale from 0-100. The curve is still visible, with all points properly plotted but will I lose a mark since the scale is too large?

2) For the xylem mutation question, I had two main points. For the first point I briefly went over how xylem vessels are composed of rigid lignin walls and that this mutation would effectively decrease the amount of lignin, decreasing rigidity and having a wilting effect.

 For my second point however, I said something that I haven't even heard anyone else talk about yet. I said that thinning the cell walls of the xylem will effectively thin the walls of the xylem vessel causing it to have a larger diameter. Water moves in the xylem via the TRACT model, in which water passively moves up the vessel by adhering to the cell walls of the vessel alongside the positive pressure that is created in the roots and the negative pressure created in the leaves due to transpiration. By increasing the diameter of the vessel however the SA:V of water contact to xylem walls has decreased and the pressure that is created in the xylem is lessened. This leads to water moving more slowly up the vessel and hence cells that require water for photosynthesis etc receive it more slowly. Overtime this decrease in metabolic rate can potentially lead to wilting as the plant dies

Did i screw myself?

edit: The answer about water leaving the xylem via osmosis at unintentional locations doesn't make too much sense to me which is partly why I avoided it. I've pretty much accepted it as the correct answer as everyone else seems to have put it down but wouldn't eventual osmotic equilibrium alongside the areas where it is unintentially left mean that water will end up still travelling up the plant to the areas it is meant to? I guess the point is that its less efficient water travel?