VCE Biology Question Thread

[Bri MT]

EDIT: Just adding to Bri MT's response.
Genetic drift can be slowed by gene flow because it is the transfer of different genes from one population to another, so there will likely be a lot of genetic variation, if I'm understanding Chocolatepistachio's question correctly.

Geneflow is about the transfer of genetic material between populations yes. Alleles would be a more accurate term to use here than genes.

Genetic drift is not the same thing as reduction in genetic diversity however it can have that consequence. I'm not sure what you're arguing here.  (I don't mean arguing in a negative sense btw, just that I'm unsure of your intended message )

thanks also for this question why is it d and not 0.2.

Is there any other context for this question? Allele frequencies should add to 1.

[Chocolatepistachio]

no there is no other context for the question

[SmartWorker]

Hey,
I have been doing practice exams for Bio have been consistently getting between 80 to 84% (VCAA exams ~ 3 + ~3 others). How do you suggest I can improve? I have been correcting the exams myself.

[homeworkisapotato]

A few years ago, I was browsing AN and I found a similar post with an amazing answer. I cannot find that post, but there was this great Excel spreadsheet I think you should try.
This is not my sheet. This was provided by a generous AN user on one of their posts. I do not want to take credit for someone else's hard work. If this is yours please PM me so I can add your name to this. I'm not taking credit for this.

I strongly believe that you should also write down the questions you got wrong, what you put as an answer, and what the recommended answer is. Then, you should find what you did wrong and note that in that table I've attached. If you do this for a few exams, there will be a pattern. Once you find the pattern, it'll be easier to improve. The pattern might be one specific topic, or one question type, or maybe scientific terminology.
Good luck!

[Owlbird83]

Hey,
I have been doing practice exams for Bio have been consistently getting between 80 to 84% (VCAA exams ~ 3 + ~3 others). How do you suggest I can improve? I have been correcting the exams myself.

This is sort of a similar idea to homeworkisapotato, but create a word document that you always have open when correcting your exaams, and write down all the points you need to remember, how you've lost marks. Make sure you spend a lot of time correcting your exams, rather than just ticking crossing, I did not spend a lot of time/energy or focus when I was correcting my past exams for bio, I realised how important is was after that. (I possibly spent almost 1hour for correction of past exams in yr12). Also I found it helpful to read over all multiple choice even the ones I got correct after correction, because sometimes there are some you guess correctly, but never come back to them

an example (but this is chem)

I also had the percentage, name of exam, score at the top

Got this idea originally from someone on AN also 

[Chocolatepistachio]

why is the answer for this question c

[1729]

Quick and dirty pedigree rules

Autosomal dominant
- Never skip generation
- Involve male-to-male transmission

Autosomal recessive
- Usually skip generation
- Involve male-to-male transmission
- Involve consanguinity

X-linked recessive
- Usually do not skip generation
- Never involve male-to-male transmission
- Males predominantly affected

X-linked dominant
- Usually do not skip generation
- Never involve male-to-male transmission
- Females will have roughly equal prevalence compared to males

Y-linked
- Only involve male-to-male transmission (very distinct)

Mitochondrial
- All children of diseased mother affected
- Disease stops transmission whenever a male has progeny

Looking at the pedigree, we notice a few things:
- The disease skips generations
- Only males are affected

Diseases that skip generations must be inherited recessively, as diseases that follow dominant patterns of inheritance are present in every generation in a pedigree. Choices (B) and (D) are eliminated. Autosomal recessive diseases involve male-to-male transmission, whereas X-linked recessive diseases never involve male-to-male transmission. We cannot tell based on the pedigree if the disease is transferred in an autosomal or X-linked manner because there are not enough generations or affected individuals present; however, the mode of inheritance is likely X-linked recessive because no male-to-male transmission is present. Choice (C) is the best answer.

why is the answer for this question c

In other words, you can eliminate autosomal dominant, if in generation 1, the father and the mother are both, say, "aa" for the specific trait, then how would the son have the trait in generation 2? So if I is not a possible option, then III is also not a possible option because we can eliminate B. Autosomal recessive is definitely possible. Say the father in generation 1 is "Aa" and the mother is "Aa." the son of generation 2 could be "aa." And x linked recessive is possible. The father in generation 1 could be "Xa Y" and the mother could be "XA Xa". So the son in gen 2 could be "XA Y," in which he would inherit the trait so II and IV is the answer. 

Geneflow is about the transfer of genetic material between populations yes. Alleles would be a more accurate term to use here than genes.

Genetic drift is not the same thing as reduction in genetic diversity however it can have that consequence. I'm not sure what you're arguing here.  (I don't mean arguing in a negative sense btw, just that I'm unsure of your intended message )

Ohhhh, yep you are right 100% right, I don't know what I was arguing tbh, I am sorry if I came accross in a negative way as well before.

no there is no other context for the question

Using Bri MT's advice

Allele frequencies should add to 1.

You should be able to figure out the answer being D. p + q = 1, it’s basically just 1 - 0.8 which is 0.2.

[Chocolatepistachio]

Thank you!
The answer said it’s d) 0.1 so the answer is probably wrong.

Also I need help with this question
Describe how regulation of stomata opening by guard cells is an example of homeostasis by negative feedback.

- Guard cells open and close the stomata depending on the amount of water present in the guard cell. The stomata open when the guard cell is turgid (swollen due to water in the cell vacuole). The stomata close when the guard cells are flaccid. It is example of negative feedback as it is reducing the stimulus 

[SmartWorker]

Also I need help with this question
Describe how regulation of stomata opening by guard cells is an example of homeostasis by negative feedback.

- Guard cells open and close the stomata depending on the amount of water present in the guard cell. The stomata open when the guard cell is turgid (swollen due to water in the cell vacuole). The stomata close when the guard cells are flaccid. It is example of negative feedback as it is reducing the stimulus.

The question asks specifically for the regulation of the opening and closing mechanism of guard cells, so I would also mention the controlled influx of potassium ions. As it is because of an increase in solute concentration in the guard cells, water moves via osmosis into the cell from a region of low solute to high solute concentration. When you say reducing the stimulus -> mention it. Also side note: the amount of detail you put into your answer will also be dependent on how many marks the question is worth.

[Chocolatepistachio]

Thanks

For this question:
Describe how negative feedback maintains temperature homeostasis in a warm blooded animal
Would this be a sufficient answer
- Stimulus- there is an increase in temperature- detected by heat receptors on the skin which would send messages to the brain. The hypothalamus would initiate a cooling mechanism such as vasodilation where the blood vessels dilate to increase blood flow taking more heat to the surface to be lost and hence cooling the body.

[Owlbird83]

Thanks

For this question:
Describe how negative feedback maintains temperature homeostasis in a warm blooded animal
Would this be a sufficient answer
- Stimulus- there is an increase in temperature- detected by heat receptors on the skin which would send messages to the brain. The hypothalamus would initiate a cooling mechanism such as vasodilation where the blood vessels [in extremities] dilate to increase blood flow taking more heat to the surface to be lost and hence cooling the body.

Yeah, that sounds good! ^one thing I added, but answer would be still fine without!

[Chocolatepistachio]

The question asks specifically for the regulation of the opening and closing mechanism of guard cells, so I would also mention the controlled influx of potassium ions. As it is because of an increase in solute concentration in the guard cells, water moves via osmosis into the cell from a region of low solute to high solute concentration. When you say reducing the stimulus -> mention it. Also side note: the amount of detail you put into your answer will also be dependent on how many marks the question is worth.

Is the stimulus the turgor pressure I’m a bit confused about how the stimulus is being reduced

[Owlbird83]

Is the stimulus the turgor pressure I’m a bit confused about how the stimulus is being reduced

Increase in water in leaf and guard cells (stimulus), causes the guard cells to be turgid and open the stomata, leading to water being able to leave through transpiration, leading to decrease in water content of leaf. -> maintaining stable water levels in leaf
Decrease in water in leaf and guard cells (stimulus), causes guard cells to loose pressure and become flaccid, causing stomata to close, preventing water from leaving.
This is what I would say for that homeostasis question

[Coolgalbornin03Lo]

What exactly is MCH restriction? How is it relevant to our course? I know it has something to do with the Cell mediated response and naive Cytotoxic T cells but other than that I’m not sure.

[Coolgalbornin03Lo]

If a bacteria replicates do the clones get the recombinant plasmid as well? I was wondering because since the bacterial chromosome replicates separately from the plasmid what does this effect?