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January 20, 2020, 12:49:30 am

Author Topic: VCE Biology Upgrade My Answer  (Read 2537 times)  Share 

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enociz

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Re: VCE Biology Upgrade My Answer
« Reply #15 on: September 27, 2019, 06:22:28 pm »
+4
@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.

PhoenixxFire

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Re: VCE Biology Upgrade My Answer
« Reply #16 on: September 27, 2019, 06:29:58 pm »
+5
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.
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Rameen

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Re: VCE Biology Upgrade My Answer
« Reply #17 on: September 28, 2019, 07:30:02 pm »
+4
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 :/ )

Chocolatemilkshake

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Re: VCE Biology Upgrade My Answer
« Reply #18 on: September 30, 2019, 04:33:20 pm »
+1
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
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Erutepa

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Re: VCE Biology Upgrade My Answer
« Reply #19 on: September 30, 2019, 04:57:26 pm »
+4
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
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Re: VCE Biology Upgrade My Answer
« Reply #20 on: September 30, 2019, 08:28:57 pm »
+6
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.
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paulthekiller123

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Re: VCE Biology Upgrade My Answer
« Reply #21 on: October 02, 2019, 03:14:13 pm »
+1
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"

Bri MT

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Re: VCE Biology Upgrade My Answer
« Reply #22 on: October 02, 2019, 05:29:42 pm »
+3
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

paulthekiller123

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Re: VCE Biology Upgrade My Answer
« Reply #23 on: October 02, 2019, 06:20:01 pm »
0
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)?

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Re: VCE Biology Upgrade My Answer
« Reply #24 on: October 05, 2019, 10:39:37 am »
+4
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

FrankieDens

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Re: VCE Biology Upgrade My Answer
« Reply #25 on: October 10, 2019, 06:06:52 pm »
0
    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.

  • 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[/list]
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PhoenixxFire

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Re: VCE Biology Upgrade My Answer
« Reply #26 on: October 10, 2019, 06:22:25 pm »
+2
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.
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SmartWorker

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Re: VCE Biology Upgrade My Answer
« Reply #27 on: December 15, 2019, 01:09:31 pm »
+1
Hey,

I have a question, can someone please help me clarify this and improve my answer:

1. Sucrose cannot cross the plasma membranes of red blood cells, but glucose can. Red blood cells are immersed in the following solutions:
■ a hypertonic sucrose solution
■ a hypertonic glucose solution
■ a hypotonic sucrose solution
■ a hypotonic glucose solution.
a Which solution would be expected to cause the greatest water loss and shrinkage of the red blood cells? Explain.
b Which solution, if any, might cause the red blood cells to burst? Explain.


For a) I wrote: A hypertonic sucrose solution is described as where the solute concentration is greater outside the cell and since sucrose cannot enter Red Blood Cells, the solution will remain hypertonic and the water may flow out of the cell via osmosis causing the cell to shrink.

For b) I wrote: A hypotonic glucose solution is described as where the solute concentration is greater inside the cell and since glucose can enter Red Blood Cells,  water may flow into the cell via osmosis causing the cell to burst.

Any help is appreciated 👍
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ssillyssnakes

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Re: VCE Biology Upgrade My Answer
« Reply #28 on: December 15, 2019, 02:47:58 pm »
+3


Hey,

I have a question, can someone please help me clarify this and improve my answer:

1. Sucrose cannot cross the plasma membranes of red blood cells, but glucose can. Red blood cells are immersed in the following solutions:
■ a hypertonic sucrose solution
■ a hypertonic glucose solution
■ a hypotonic sucrose solution
■ a hypotonic glucose solution.
a Which solution would be expected to cause the greatest water loss and shrinkage of the red blood cells? Explain.
b Which solution, if any, might cause the red blood cells to burst? Explain.


For a) I wrote: A hypertonic sucrose solution is described as where the solute concentration is greater outside the cell and since sucrose cannot enter Red Blood Cells, the solution will remain hypertonic and the water may flow out of the cell via osmosis causing the cell to shrink.

For b) I wrote: A hypotonic glucose solution is described as where the solute concentration is greater inside the cell and since glucose can enter Red Blood Cells,  water may flow into the cell via osmosis causing the cell to burst.

Any help is appreciated

For both your answers, it may be best to clearly state which solution is expected to cause (...), such as "The hypersonic sucrose solution would likely cause the greatest water loss and shrinkage in the red blood cells as...".

 I also think you went into a little too much detail in explaining WHAT the terms mean, rather than why they would cause these cells to shrink/swell/whatever. The question assumes you know what the terms hypo and hypertonic mean and dont ask you to define them, so doing so is pretty much a waste of time.

Hope this helps!
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SmartWorker

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Re: VCE Biology Upgrade My Answer
« Reply #29 on: December 15, 2019, 05:53:45 pm »
+1

For both your answers, it may be best to clearly state which solution is expected to cause (...), such as "The hypersonic sucrose solution would likely cause the greatest water loss and shrinkage in the red blood cells as...".

 I also think you went into a little too much detail in explaining WHAT the terms mean, rather than why they would cause these cells to shrink/swell/whatever. The question assumes you know what the terms hypo and hypertonic mean and dont ask you to define them, so doing so is pretty much a waste of time.

Hope this helps!

Oh thanks a lot ;)
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