HSC Biology Question Thread

[Potatohater]

Hello, just a short question, when giving your answers, could you explain why the others are incorrect please?

Thanks

The answer would be A. This is because the wale lives in a salty environment and is constanly losing water via osmosis, so it needs to excrete concentrated urine in order to maintain water levels.
B is incorrect as whales excrete salt rather than store it as they need to get it out of their system.
C is incorrect since whales excret small amounts of very concentrated urine to preserve water, where as humans excrete urine that is still concentrated but just a little more dilute depending on environment and water intake.
D. Is correct in a way but it wouldn't be the answer to this question. The reason why the humans need to excrete more to remove the same amount of salt comes down to the concentration rather than the amount. Since whale urine is saltier it will take less urine to excrete the same level of salt as the human which has more dilute urine and needs to excrete more.
Hope this makes sense! (I know what I mean but not sure if I have articulated it well)

[blasonduo]

The answer would be A. This is because the wale lives in a salty environment and is constanly losing water via osmosis, so it needs to excrete concentrated urine in order to maintain water levels.
B is incorrect as whales excrete salt rather than store it as they need to get it out of their system.
C is incorrect since whales excret small amounts of very concentrated urine to preserve water, where as humans excrete urine that is still concentrated but just a little more dilute depending on environment and water intake.
D. Is correct in a way but it wouldn't be the answer to this question. The reason why the humans need to excrete more to remove the same amount of salt comes down to the concentration rather than the amount. Since whale urine is saltier it will take less urine to excrete the same level of salt as the human which has more dilute urine and needs to excrete more.
Hope this makes sense! (I know what I mean but not sure if I have articulated it well)

Hey! Thanks for the answer, I also put A, but the answers say it is D.

I thought I must have missed something.

Thank you for the clearup

[Potatohater]

Hey! Thanks for the answer, I also put A, but the answers say it is D.

I thought I must have missed something.

Thank you for the clearup

So the Answer is D? I'm really doubting myself now, can anyone explain why we are wrong?

[vox nihili]

Where's the question from? My suspicion is that they've just stuffed up and that A is correct.

[maddiewainwright]

Can someone please explain to me the concept of sex-linkage?? I understand it, but when given a question always mess it up thxxx

Hi gillv2017,
Basically, sex linkage is the concept that certain genes are located on either the X or Y chromosome exclusively (i.e. the gene for haemophilia is only located on the X chromosome). This can mean that patterns of inheritance are slightly different to typical Mendelian inheritance. For recessive genes linked to the X chromosome, males in a population will be affected at a higher rate. This is because males (XY) only inherit one X chromosomes from their mothers, and therefore will not have two alleles for the gene. This means they must express whatever allele is inherited, even if they only inherit one recessive trait.
For a question on sex-linkage I always liked to draw a punnet square because it's a really simple way to demonstrate this concept.
Hope this helps!

[blasonduo]

Where's the question from? My suspicion is that they've just stuffed up and that A is correct.

It was the 2013 Sydney tech trial paper Question 3

http://www.acehsc.net/wp-content/uploads/TrialPapers/2013/Biology/2013_Biology_-_Sydney_Tech_Trial_with_Solutions.pdf

[DalvinT]

Hey! I'm struggling to answer the higher order questions like the 7 marker questions!!! Like when I go to the marking guideline, I didn't even think of including some of the things that must've been incorporated in our response to gain the marks.

For example, in the attachment, I wouldn't even think of writing about the problems engaged initially...

[caitlinlddouglas]

Hey i was wondering for the dot point in search for better health for the secondary source dotpoint: describe 1 named infectious disease in terms of its cause, transmission, host response, major symptoms, treatment, prevention & control how detailed an answer for the host response had to be? Thanks!

[Mounica]

Hey, Guys
can someone please explain to me what introns and exons are??
thanks

[Opengangs]

Hey, Guys
can someone please explain to me what introns and exons are??
thanks

Exons are the coding regions of DNA. That is, they encode proteins and express genes.
Introns are the non-coding regions of DNA found between the exons. They do not specialise in encoding proteins, but some introns help with the expression of genes. Some introns contain hypervariable strands or Variable Number Tandem Repeats (VNTR) which is basically the way forensic scientists discover one's DNA fingerprints.

[Opengangs]

Hey! I'm struggling to answer the higher order questions like the 7 marker questions!!! Like when I go to the marking guideline, I didn't even think of including some of the things that must've been incorporated in our response to gain the marks.

For example, in the attachment, I wouldn't even think of writing about the problems engaged initially...

The key section is its directive term, justify
It's a good idea to get used to what BOSTES wants with these directive terms.

So, to justify something means to support an argument or conclusion.

My personal marking breakdown:

1 mark -- Define DNA-DNA hybridisation.
1 mark -- Define karyotype analysis
2 marks -- Outline the uses of DNA-DNA hybridisation
2 marks -- Outline the uses of karyotype analysis
1 mark -- Relate these uses back to the stimulus (ie how are they used to solve these problems)

The breaking down of marks just comes back to practice and practice!!
The more you understand what they want, the better you'll be at it.

[DalvinT]

The key section is its directive term, justify
It's a good idea to get used to what BOSTES wants with these directive terms.
So, to justify something means to support an argument or conclusion.

My personal marking breakdown:

1 mark -- Define DNA-DNA hybridisation.
1 mark -- Define karyotype analysis
2 marks -- Outline the uses of DNA-DNA hybridisation
2 marks -- Outline the uses of karyotype analysis
1 mark -- Relate these uses back to the stimulus (ie how are they used to solve these problems)

The breaking down of marks just comes back to practice and practice!!
The more you understand what they want, the better you'll be at it.

Ahh I see! THANK YOU SO MUCH! It really has helped!!

[stephjones]

Hey guys, how do you go about answering the "How would you improve this experiment?" questions?

[Natasha.97]

Hey guys, how do you go about answering the "How would you improve this experiment?" questions?

Hi!

I think those types of questions are usually looking for the following 3 things:
1) Reliability: Repeating the experiment numerous times (and getting similar results), or have 2 groups follow the same experimental procedure (and getting similar results), then the results are reliable
2) Accuracy: Using precise equipment to reduce uncertainty, e.g. using a pH probe instead of pH paper + chart, a measuring cylinder rather than a beaker
3) Validity: Making sure that the results obtained stem from ONLY the change in the independent variable (the one you vary). This is ensured by keeping all variables the same, e.g. effect of substrate concentration on enzymes: control temperature, pH, volume of enzyme etc.

Hope this helps!

[mjorfian]

most important (or most commonly asked) concepts to nail down in bio core? I have two days to prepare #ragrets