ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Biology => Topic started by: Bri MT on February 22, 2019, 03:32:03 pm

Title: VCE Biology Upgrade My Answer
Post by: Bri MT on February 22, 2019, 03:32:03 pm
VCE BIOLOGY
UPGRADE MY ANSWER


What is this thread for?
If you want feedback on your answers so you can get more marks for your knowledge, this is the place!

Step 1. Share a question you didn't get full marks on, including your answer and how many marks the question was worth
Step 2. Wait for another user (maybe even multiple!) to provide feedback on how they might've approached the question and how you could improve your answer
Step 3. Apply the feedback you've learnt to aim for higher marks more confidently :)


Who can/will provide feedback?
Everyone is welcome to contribute; even if you're unsure of yourself, providing different perspectives is incredibly valuable.

Please don't be dissuaded if you haven't finished Year 12, or didn't score as highly as others, or your advice contradicts something else you've seen on this thread, or whatever; none of this disqualifies you from helping others. And if you're worried you do have some sort of misconception, put it out there and someone else can clarify and modify your understanding! 

There'll be a whole bunch of other high-scoring students with their own wealths of wisdom to share with you, including TuteSmart tutors! So you may even get multiple answers from different people offering their insights - very cool.


To ask a question or make a post, you will first need an ATAR Notes account. You probably already have one, but if you don't, it takes about four seconds to sign up - and completely free!


OTHER BIOLOGY RESOURCES
Title: Re: VCE Biology Upgrade My Answer
Post by: SmartWorker on March 29, 2019, 05:05:16 pm
Hi, can we submit pracs for review?
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on March 29, 2019, 05:49:43 pm
Hi, can we submit pracs for review?
Hey,
It depends what the prac is for - if it's work that you're going to be submitting for a SAC (e.g. U4 AOS3) then we can't help you with it as that's against VCAA rules. If it's not something that you're going to be submitting then we can give you feedback on it :)
Title: Re: VCE Biology Upgrade My Answer
Post by: almondsforlife on April 09, 2019, 06:04:19 pm
Hi! This is my first post and I had my first sac in term 1. This is one question I didn’t get full marks on - could someone please give some feedback?
Question: Two species of plants are found, and both live in highly saline soils. Sodium is transported via facilitated diffusion in root cells. Suggest why this is vital for the survival of these Antarctic plants. (3 marks)
My answer: The root cells need sodium ions to survive in the harsh saline environment, and so there is a net passive movement of sodium ions from an area of high concentration of sodium ions in the highly saline soils to an area of low concentration of sodium ions in the root cells across a semipermeable membrane via channel proteins until equilibrium is reached.
Thanks again.
Title: Re: VCE Biology Upgrade My Answer
Post by: Sine on April 09, 2019, 06:18:52 pm
Hi! This is my first post and I had my first sac in term 1. This is one question I didn’t get full marks on - could someone please give some feedback?
Question: Two species of plants are found, and both live in highly saline soils. Sodium is transported via facilitated diffusion in root cells. Suggest why this is vital for the survival of these Antarctic plants. (3 marks)
My answer: The root cells need sodium ions to survive in the harsh saline environment, and so there is a net passive movement of sodium ions from an area of high concentration of sodium ions in the highly saline soils to an area of low concentration of sodium ions in the root cells across a semipermeable membrane via channel proteins until equilibrium is reached.
Thanks again.
You have basically answered WHAT is happening in this situation. The questions wants to know WHY it is important.
Title: Re: VCE Biology Upgrade My Answer
Post by: almondsforlife on April 09, 2019, 07:36:37 pm
You have basically answered WHAT is happening in this situation. The questions wants to know WHY it is important.
Oh okay. So would the root cells become too turgid if there was a steep concentration gradient of sodium ions?
Title: Re: VCE Biology Upgrade My Answer
Post by: Erutepa on April 09, 2019, 08:16:08 pm
Oh okay. So would the root cells become too turgid if there was a steep concentration gradient of sodium ions?
If the soil was highly saline and had a high concentration of sodium relative to the roots, then water would move from the root cells into the soil (water moves towards the solute).
Given this, maybe it will be a bit more obvious why it is important for the root cells to transport sodium into the cell, remembering that plants do need water to survive.
Title: Re: VCE Biology Upgrade My Answer
Post by: almondsforlife on April 09, 2019, 08:30:33 pm
If the soil was highly saline and had a high concentration of sodium relative to the roots, then water would move from the root cells into the soil (water moves towards the solute).
Given this, maybe it will be a bit more obvious why it is important for the root cells to transport sodium into the cell, remembering that plants do need water to survive.
Ohhh! So the root cells would become plasmolysed or flaccid due to the movement of free water molecules from the cells to the soil. Thank you!
Title: Re: VCE Biology Upgrade My Answer
Post by: enociz on April 09, 2019, 10:28:52 pm
Ohhh! So the root cells would become plasmolysed or flaccid due to the movement of free water molecules from the cells to the soil. Thank you!

I think your answer should look at:
- The problem (there is a lot of sodium in the soil as opposed to the root cells, leading to a strong concentration gradient by which water is able to have a net movement out of the cells and into the lower water potential in the highly saline soil)
- The solution given (when the passive diffusion of salt into the root cells occurs, it balances the concentration gradient by equalising the salt concentration inside the cell with that in the soil)
- The impact this has (this prevents the net movement of water out of the cell by removing the concentration gradient needed for the osmosis of water molecules to occur, allowing the plant to retain the water needed to survive)

That might be too much detail for each part, but it should cover the 3 marks. :)
Title: Re: VCE Biology Upgrade My Answer
Post by: almondsforlife on April 10, 2019, 06:26:26 pm
I think your answer should look at:
- The problem (there is a lot of sodium in the soil as opposed to the root cells, leading to a strong concentration gradient by which water is able to have a net movement out of the cells and into the lower water potential in the highly saline soil)
- The solution given (when the passive diffusion of salt into the root cells occurs, it balances the concentration gradient by equalising the salt concentration inside the cell with that in the soil)
- The impact this has (this prevents the net movement of water out of the cell by removing the concentration gradient needed for the osmosis of water molecules to occur, allowing the plant to retain the water needed to survive)

That might be too much detail for each part, but it should cover the 3 marks. :)
Thank you so much for the sample response! I wasn’t thinking about osmosis, only diffusion, so I only mentioned movement of sodium ions.
Title: Re: VCE Biology Upgrade My Answer
Post by: FrankieDens on September 21, 2019, 09:03:41 am
Hey guys,  :D

(Please note that my school gives half-marks only for SACs to provide a more accurate ranking)

Q.How does the technique of DNA hybridisation enable scientists to determine the evolutionary relationships between species? [2 marks]
My answer:
[I received 1.5 marks]

So the teacher who marked my SAC circled 'the more stronger the hydrogen bonds' and wrote a question mark. They also said that instead of 'more recent common ancestor' I should have used 'more closely related' and that I should use terminology more carefully.
My question is, which one did I lose the half mark for and how would you improve my answer?

Thanks everyone!  8)
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on September 21, 2019, 12:09:17 pm
Hey guys,  :D

(Please note that my school gives half-marks only for SACs to provide a more accurate ranking)

Q.How does the technique of DNA hybridisation enable scientists to determine the evolutionary relationships between species? [2 marks]
My answer:
  • The higher the temperature to separate hybrid DNA strands, the more stronger the hydrogen bonds
  • This means there are a lot of complimentary bases and the DNA between the two organisms are similar
  • Therefore, it can be determined if two organisms shared a more recent common ancestor and how related they are.
[I received 1.5 marks]

So the teacher who marked my SAC circled 'the more stronger the hydrogen bonds' and wrote a question mark. They also said that instead of 'more recent common ancestor' I should have used 'more closely related' and that I should use terminology more carefully.
My question is, which one did I lose the half mark for and how would you improve my answer?

Thanks everyone!  8)
1) Hydrogen bonds don't differ in strength. If species share more dna bases, thy will have more hydrogen bonds holding the strands together. The more hydrogen bonds that need to be broken, the more energy that is required.

2) More closely related is better for this because you don't know if they shared a more common ancestor, that's the most likely reason that they'd have more bases in common, but it's also possible that after speciation they faced similar selection pressures and due to those selection pressures any individuals with mutations died, which kept their dna similar for longer (although if you're hybridising between non coding regions then this becomes irrelevant).

- The higher the temperature required to separate hybrid DNA strands, the more hydrogen bonds there are holding the strands together.
- More hydrogen bonds means that the strands of DNA have more complimentary bases, which means they are more closely related.
- Therefore, DNA strands of species that are more closely related will seperate at a higher temperature than DNA strands of species less closely related.

I'd say losing half a mark was probably due to the first problem, the second one isn't that big of a deal.
Title: Re: VCE Biology Upgrade My Answer
Post by: Rameen on September 27, 2019, 06:03:29 pm
Question: Describe the process of allopatric speciation.

My answer: The process of forming a new species due to a geographical barrier that separates a population. These isolated populations are subject to different selection pressures so when they meet again, they are no longer able to interbreed.

This question was 3 marks. How could I improve it?
Thank you in advance
Title: Re: VCE Biology Upgrade My Answer
Post by: Evolio on September 27, 2019, 06:11:17 pm
Hi!
You could also say that no gene flow occurs between the two populations due to the geographical barrier allowing no exchange of genetic information. Following on from the different selection pressures point, you could also say that there would be changes in allele frequencies as one allele may be favourable in one group but not favourable in the other group (due to the different selection pressures).
You could also say that mutations occur which affect mating.
When you mentioned that they are no longer able to interbreed, you could also add additional info about how the two members of the separate groups will not be able to produce fertile, viable offspring.
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on September 27, 2019, 06:21:10 pm
Question: Describe the process of allopatric speciation.

My answer: The process of forming a new species due to a geographical barrier that separates a population. These isolated populations are subject to different selection pressures so when they meet again, they are no longer able to interbreed.

This question was 3 marks. How could I improve it?
Thank you in advance
Your answer covers the three main points you need to include, but doesn't focus on the right areas.
I'd get rid of the first half of the first sentence - you're describing the process not defining or explaining what it is.

The three point that you have to include are:
G - geographical isolation
S - selection pressures are different
D - differences accumulate to the point where they're unable to interbreed successfully.

You've got:
G - The process of forming a new species due to a geographical barrier that separates a population.
S - These isolated populations are subject to different selection pressures
D - so when they meet again, they are no longer able to interbreed.

Suggestions:
G - get rid of the first half. Say something more like "allopatric speciation occurs when a population is separated by a geographical barrier" instead.
S - This part is fine, I'd change it slightly though to get rid of "isolated" and instead put at the end of that sentence something about no gene flow occurring due to their isolation from each other/barrier.
D - you need to also mention accumulation of mutations/differences, and change your phrasing to be more specific "unable to produce fertile, viable offspring". You could also put the bit about no gene flow at the start of this sentence instead of the end of the previous one if that's easier.

Feel free to have a go at rewriting it if you want :)
Title: Re: VCE Biology Upgrade My Answer
Post by: enociz on September 27, 2019, 06:22:28 pm
@rameen I'm having a crack at it here, working off your answer. I approached it by first outlining some key points of allopatric speciation, then explaining the process of speciation, and then outlining the result.

- Allopatric speciation occurs when a geographical barrier is introduced in the environment, separating a population. Due to this, there is reproductive isolation, where there is no exchange of genetic information between the two populations.
- The different environments introduce different selection pressures to the each population. Given that there is genetic variation within the populations, some individuals will have heritable traits that may be more advantageous than others. These individuals will survive to reproduce, and so will pass on the alleles to their offspring.
- Over many generations, there is a change in the allele frequencies, and speciation occurs, making the two populations unable to interbreed and produce viable, fertile offspring.
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on September 27, 2019, 06:29:58 pm
Due to this, there is reproductive isolation, where there is no exchange of genetic information between the two populations.
Careful. Reproductive isolation is the name of a specific set of conditions - it's what's occurring when species are unable to interbreed and produce viable, fertile offspring when brought back together. I assume you're just using reproductive isolation to mean that they can't interbreed, but in this case the lack of exchange of genetic information is due to geogrpahic isolation and you could lose marks if examiners think you're referring to the conditions of reproductive isolation, rather than just using those words to mean they're not interbreeding.
Title: Re: VCE Biology Upgrade My Answer
Post by: Rameen on September 28, 2019, 07:30:02 pm
When you mentioned that they are no longer able to interbreed, you could also add additional info about how the two members of the separate groups will not be able to produce fertile, viable offspring.

@rameen I'm having a crack at it here, working off your answer. I approached it by first outlining some key points of allopatric speciation, then explaining the process of speciation, and then outlining the result.

Suggestions:
G - get rid of the first half. Say something more like "allopatric speciation occurs when a population is separated by a geographical barrier" instead.
S - This part is fine, I'd change it slightly though to get rid of "isolated" and instead put at the end of that sentence something about no gene flow
Feel free to have a go at rewriting it if you want :)

Thank you so much for all your help!!

This is my updated response:
Allopatric speciation occurs when a population is separated by a geographical barrier, preventing gene flow due to their isolation.
The populations are exposed to different environments and are therefore, subject to different selection pressures. These selection pressures result in changes in allele frequencies as one allele of a particular gene may favour the reproduction and survival of one population, but not the other.
Speciation occurs over time, which makes the two populations unable to produce fertile, viable offspring.

( I didn't realise how difficult it is to structure a good response :/ )
Title: Re: VCE Biology Upgrade My Answer
Post by: Chocolatemilkshake on September 30, 2019, 04:33:20 pm
Doing VCAA practise exams and question 3b. from VCAA 2014 is...

When glycogenolysis occurs in a cell, the concentration of glucose in the cytosol increases. Glucose passes through the plasma membrane by facilitated diffusion.
Explain how the facilitated diffusion of glucose occurs?
(2)

My answer is...
- There is a lower concentration of glucose inside the cell than outside the cell.
- Glucose binds to carrier proteins which facilitate the passage of glucose into the cell along its concentration gradient.

However the VCAA report says that "Glucose moves through protein channels and along the concentration gradient."

Would I still get a mark for saying carrier protein rather than protein channel?

Thanks everyone
Title: Re: VCE Biology Upgrade My Answer
Post by: Erutepa on September 30, 2019, 04:57:26 pm
Doing VCAA practise exams and question 3b. from VCAA 2014 is...

When glycogenolysis occurs in a cell, the concentration of glucose in the cytosol increases. Glucose passes through the plasma membrane by facilitated diffusion.
Explain how the facilitated diffusion of glucose occurs?
(2)

My answer is...
- There is a lower concentration of glucose inside the cell than outside the cell.
- Glucose binds to carrier proteins which facilitate the passage of glucose into the cell along its concentration gradient.

However the VCAA report says that "Glucose moves through protein channels and along the concentration gradient."

Would I still get a mark for saying carrier protein rather than protein channel?

Thanks everyone
I think you would still get the marks, especially since carrier proteins do facilitate the diffusion of glucose
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on September 30, 2019, 08:28:57 pm
Thank you so much for all your help!!

This is my updated response:
Allopatric speciation occurs when a population is separated by a geographical barrier, preventing gene flow due to their isolation.which prevents gene flow
The populations are exposed to different environmentsal conditions and are therefore, subject to different selection pressures. These selection pressures result in changes in allele frequencies as one allele of a particular gene may favour the reproduction and survival of one population, but not the other.
You need to mention that it's the subsequent accumulation of genetic differences that leads to speciation
Speciation occurs over time, which makes the two populations unable to produce fertile, viable offspring.
You've probably written too much here - the answer is fine, but you'll waste time that could be used on other questions. This would be a 3 mark question in the exam, so you should be able to answer it with three sentences.

You've answered more than just the question being asked here, which is a mistake a lot of people make. The question is about the process of allopatric speciation, so you need to just answer about that. You've also answered another question - How do selection pressures affect allele frequencies - you haven't been asked that, so don't answer it. You can get rid of that entire sentence.

You also still haven't really linked how differing selection pressures leads to speciation.

For reference, this is what I'd write. It tends to be easier to edit your own writing (and that way it flows over to your other answers as well) rather than just copy someone else's writing style though, so make sure you're answering questions in an order/style that's comfortable to you.
Spoiler
Allopatric speciation occurs when a population is seperated by a geographical barrier, resulting in no gene flow. These populations are exposed to different selection pressures, and as a result their gene pools diverge. Over time, this accumulation of genetic differences results in speciation, meaning that if they were brought back together, they'd be unable to interbreed to produce viable, fertile offspring.

( I didn't realise how difficult it is to structure a good response :/ )
At least it's something you only have to learn once. When you figure it out you'll be able to apply it to all your questions without having to learn how to structure each one individually.
Title: Re: VCE Biology Upgrade My Answer
Post by: paulthekiller123 on October 02, 2019, 03:14:13 pm
Hey so like what would be the differences between speciation and allopatric speciation (in terms of structurally writing it in steps).
Would this example response suffice for the 2014 VCAA question?

Explain how the woolly mammoth M. primigenius probably arose from the woolly mammoth
ancestor M. africanavus.

The mammoths left Africa
-The ancestral populations were separated by a geographical barrier which prevents gene flow
-Each of the isolated populations were subjected to different selection presures
-Genetic differences accumulate to a point that results in speciation thus if they were reintroduced to one another, they would be unable to interbreed and produce viable and fertile offsprinngs

And in addition, when defining selection pressures, would it be okay to define it like this
"Selection pressure are any factors that act on the survivability/fitness of an organism"
Title: Re: VCE Biology Upgrade My Answer
Post by: Bri MT on October 02, 2019, 05:29:42 pm
Survivability and fitness aren't synonymous - e.g. fitness can also include number of viable offspring.

Remember also that speciation isn't always allopatric. You don't need to memorise sympatric speciation or anything,  but if a question asks about speciation without implying a geographical barrier consider other possible causes of change in allele frequencies until eventually the two populations would not be able to produce viable offspring together.

I haven't read any context around that question,  but to me there is nothing implying a geographic barrier
Title: Re: VCE Biology Upgrade My Answer
Post by: paulthekiller123 on October 02, 2019, 06:20:01 pm
Survivability and fitness aren't synonymous - e.g. fitness can also include number of viable offspring.

Remember also that speciation isn't always allopatric. You don't need to memorise sympatric speciation or anything,  but if a question asks about speciation without implying a geographical barrier consider other possible causes of change in allele frequencies until eventually the two populations would not be able to produce viable offspring together.

I haven't read any context around that question,  but to me there is nothing implying a geographic barrier

So in that case, what would be an example of a different approach to the question (if I'm not going to talk about geographic barriers)?
Title: Re: VCE Biology Upgrade My Answer
Post by: Bri MT on October 05, 2019, 10:39:37 am
So in that case, what would be an example of a different approach to the question (if I'm not going to talk about geographic barriers)?

From the context provided in the question (especially looking at the phylogenetic tree) it is reasonable to assume that M. aficanavus accumulated differences overtime as the species adapted to its environment which eventually led to M. primigenius. Note your answer suggests that the phylogenetic tree should bifurcate (split into two) due to the speciation event whereas this answer does not.  To write the type of response I am suggesting, you could use a evolution by natural selection answer style.

- There was genetic variability within M. aficanavus
- Some of this genetic variation conferred a fitness advantage within M. aficanavus's environment, leading to more offspring being born with traits encoded by those genetic variants
- This leads to accumulation of these traits over evolutionary time
- Eventually, this accumulation of traits was significant enough that the resultant population was considered a new species, M. primigenius
Title: Re: VCE Biology Upgrade My Answer
Post by: FrankieDens on October 10, 2019, 06:06:52 pm
My answer: I got one mark.

My answer:I got 1 mark[/list]
Title: Re: VCE Biology Upgrade My Answer
Post by: PhoenixxFire on October 10, 2019, 06:22:25 pm
Hi everyone,

  • Question 1: Describe two ethical implications or issues associated with the use of DNA profiling [2 marks]
My answer:
  • The man has the right to know if he is the father of the child in order to maintain a relationship with him.
  • The child had no say in providing his DNA sample and if he actually wants to know who is his biological father - which is unethical.
I got one mark.
You only got one mark because your first point is a use for dna profiling, but it's not an ethical issue.
  • Question 2: Carl's partner has no history of Huntington's disease in her family, however, the chances of any of their children having the disease is 50%. Describe one social and one ethical issue or implication associated with the use of this technology. (Genetic screening) [2 marks]
My answer:
  • Ethical: Carl and his partner will constantly worry about having a child that will inherit Huntington's disease.
  • Social: This may cause a division between those that can or can not afford genetic screening.
I got 1 mark
Who's being screened here? I assume Carl?
Carl and his partner worrying is more of a social issue than an ethical one, so that's probably where you lost the mark. An ethical issue would be something like it then affecting their choice about whether to/how to have kids.