HSC Biology Question Thread

[Razeen25]

Thank you both for your input ^_^. It was really interesting to read and I really hope C is the correct answer otherwise CYAA loool.

[PhoenixxFire]

my understanding of reliability was also that when the experiment was repeated several times by a different experimenter, the same results would occur.

Reliability means that you or another person could repeat the experiment and get the same results. The only thing that could change the results of the experiment are if you make a mistake, your method is not clear enough for someone else to follow or (most commonly) if there are variables that aren't controlled - hence why controlling variables is part of reliability.

[ateenytinybear]

can anybody help with this past hsc question?

Which of the following statements best describes the process of hybridisation frequently used in agriculture?
A The transfer of a gene from one species to another.
B The crossing of two genetically different strains of a species.
C The production of genetically identical offspring by cloning.
D The artificial selection and breeding of suitable offspring within a species.

I kinda see how all of these could be the answer so idkkkk
thankyou for any help

[KT Nyunt]

can anybody help with this past hsc question?

Which of the following statements best describes the process of hybridisation frequently used in agriculture?
A The transfer of a gene from one species to another.
B The crossing of two genetically different strains of a species.
C The production of genetically identical offspring by cloning.
D The artificial selection and breeding of suitable offspring within a species.

I kinda see how all of these could be the answer so idkkkk
thankyou for any help

Hybridisation is crossing two organisms of different species or two organisms of different strains of a species, producing a hybrid which has hybrid vigour. Thus, I believe the answer should be (B). (A) is definitely transgenic species. (C) is cloning. Whereas, (D) is just artificial selection or artificial insemination/pollination. So by the process of elimination the answer is (B). A,C and D are processes under the reproductive technologies topic. Although they all (including hybridisation) aim to produce offspring that has favourable characteristics, the process in which they do so is different.

Hope this helps!

[Mate2425]

Hi could i please get help with understanding why the answer to the 2015 MCQ15 is C. Thank you, please find attached below a link to the paper: 
https://www.boardofstudies.nsw.edu.au/hsc_exams/2015/exams/2015-hsc-biology.pdf

[jasn9776]

Hi could i please get help with understanding why the answer to the 2015 MCQ15 is C. Thank you, please find attached below a link to the paper: 
https://www.boardofstudies.nsw.edu.au/hsc_exams/2015/exams/2015-hsc-biology.pdf

Probably incomplete dominance so Ry is orange. I think they removed it from the syllabus anyways but to work it out just cross RR and YY to get RY then cross two RY to get RR, RY, RY, YY. These are just probablities and the experiment could be close enough to these ratios.

[TheBigC]

Hi could i please get help with understanding why the answer to the 2015 MCQ15 is C. Thank you, please find attached below a link to the paper: 
https://www.boardofstudies.nsw.edu.au/hsc_exams/2015/exams/2015-hsc-biology.pdf

Awesome question! I am VCEer, however, hopefully I can be of some help here.

This question is tricky because it requires very careful reading. Notice how it specifically intimates that 'the F2 results were...': it is referring to generation 2, not 1. Thus, the answer is C, as the ORIGINAL parents had genotypes RR and YY, thus producing offspring: RY, RY, RY, RY. These offspring then mated (RY x RY) to yield: RR, RY, RY, YY. Hence, we can see that the ratio of RR (red) : YY (yellow) is roughly equivalent (6:5) and the amount of RY (orange - incomplete dominance) should be approx double, which it is (11).

[Mate2425]

Probably incomplete dominance so Ry is orange. I think they removed it from the syllabus anyways but to work it out just cross RR and YY to get RY then cross two RY to get RR, RY, RY, YY. These are just probablities and the experiment could be close enough to these ratios.

Thanks for your help 

[Mate2425]

Awesome question! I am VCEer, however, hopefully I can be of some help here.

This question is tricky because it requires very careful reading. Notice how it specifically intimates that 'the F2 results were...': it is referring to generation 2, not 1. Thus, the answer is C, as the ORIGINAL parents had genotypes RR and YY, thus producing offspring: RY, RY, RY, RY. These offspring then mated (RY x RY) to yield: RR, RY, RY, YY. Hence, we can see that the ratio of RR (red) : YY (yellow) is roughly equivalent (6:5) and the amount of RY (orange - incomplete dominance) should be approx double, which it is (11).

Thanks this helped a lot 

[Razeen25]

Hii!

In the 2 mark question 'Identify how the concentration of TWO substances will change as fluid moves through the proximal convoluted tubule', would it be correct to say that "As fluid passes through the proximal tubule, the fluid concentration of water will DECREASE as it passively is reabsorbed into blood by osmosis, and that the fluid concentration of amino acids will also DECREASE as it is re-absorbed into the blood through active transport"?

Thank you!

[Potatohater]

Hii!

In the 2 mark question 'Identify how the concentration of TWO substances will change as fluid moves through the proximal convoluted tubule', would it be correct to say that "As fluid passes through the proximal tubule, the fluid concentration of water will DECREASE as it passively is reabsorbed into blood by osmosis, and that the fluid concentration of amino acids will also DECREASE as it is re-absorbed into the blood through active transport"?

Thank you!

Yeah that's pretty much it, there are other substances but the question only asks for 2 so that's fine

[Razeen25]

Yeah that's pretty much it, there are other substances but the question only asks for 2 so that's fine

Thank you soo much!! 

[Kate Science]

Hii!
Today in my The Search For Better Health exam there was a multiple choice question showing a picture of Pasteur's experiment being modelled, and there were 2 answers (the other 2 were silly answers) I'm confused about.
The diagram showed two flasks containing broth (one broken, one unbroken) being boiled and the question was 'How is this experiment valid' or something and the two answers were:
c) The use of a control
d) The heat used to boil the broth

I chose C but I don't know if I should have chosen D smh since IDEK if there was a control rip

(C) is the correct answer but it's important to understand the full scope of what you are dealing with. Validity, in first hand investigations, is determined by how well you control all the variables that could possibly impact on the experiment. For example if you wanted to test the effect of 'variable Y' on 'variable Z', then A, B, C, .... X must be controlled. If any factor of A, B, C, ... X is NOT kept constant, then you are now NOT testing the effect of Y on Z - you'll actually be measuring the effect of Y and B on Z etc - not your aim, not valid.

The next thing is about the idea of a 'control' and a 'test' version - in this case the intact and broken glass. This is to with VALIDITY - not reliability. Here's why:

Our test is investigating the effect of 'Variable X - air exposure' on 'Variable Y - microbial growth in broth'. Our CONTROL is testing 'Variable Y - microbial growth in broth' WITHOUT changing 'Variable X - air exposure' so that we can compare the two later on. This is validity - testing your aim - being able to compare an unchanged with something you've changed (i.e. broken neck of flask).

Be careful not to say this has to do with reliability which, in the context of first hand investigations, is purely to do with the consistency and replicability of your results - not the nature or method of your experiment (which fall under validity always).

[Razeen25]

(C) is the correct answer but it's important to understand the full scope of what you are dealing with. Validity, in first hand investigations, is determined by how well you control all the variables that could possibly impact on the experiment. For example if you wanted to test the effect of 'variable Y' on 'variable Z', then A, B, C, .... X must be controlled. If any factor of A, B, C, ... X is NOT kept constant, then you are now NOT testing the effect of Y on Z - you'll actually be measuring the effect of Y and B on Z etc - not your aim, not valid.

The next thing is about the idea of a 'control' and a 'test' version - in this case the intact and broken glass. This is to with VALIDITY - not reliability. Here's why:

Our test is investigating the effect of 'Variable X - air exposure' on 'Variable Y - microbial growth in broth'. Our CONTROL is testing 'Variable Y - microbial growth in broth' WITHOUT changing 'Variable X - air exposure' so that we can compare the two later on. This is validity - testing your aim - being able to compare an unchanged with something you've changed (i.e. broken neck of flask).

Be careful not to say this has to do with reliability which, in the context of first hand investigations, is purely to do with the consistency and replicability of your results - not the nature or method of your experiment (which fall under validity always).

Thank you so much for this, it helped me understand this a lot!

[cnimm2000]

Hey guys,
I was working on the genetics: code unbroken topic. For dihybrid crosses, does the question state if its linked or unlinked or do we need to figure it out. If so how would i figure out if its linked or unlinked?
Thanks in advance