VCE Biology Questions Thread
- Edited
Just want to confirm if my reasoning is right and ask a question about how index fossils are use to date other fossils found in the same strata:
Firstly radiometric dating is utilized to date igneous rock associated with (near) sedimentary layer that the index fossil is found within, percentage of parent isotope is compared to broken down products, hence using stratigraphy it can be inferred that the age of the index fossil = ____.
Using stratigraphy, the fossil found in the same strata is the same age as the index fossil, ____.
So if the question asked whether using index fossils is absolute or relative (point 2) what would be say?
Relative - because the age of the fossil is being determined by using the index fossil nearby?
or Absolute - because the NUMERICAL value of the fossil is known because of the INDEX fossils whose NUMERICAL age is also known?
Hey tubes!
- Firstly radiometric dating is utilized to date igneous rock associated with (near) sedimentary layer that the index fossil is found within, percentage of parent isotope is compared to broken down products, hence using stratigraphy it can be inferred that the age of the index fossil = ____.
Here you must mention that calculations are made based on the half life of the particular radioisotope measured in the radiometric dating; otherwise, how does the ratio of parent to daughter nuclei help?
It might also be good to mention the type of radiometric dating technique you are referring to (i.e. K-Ar dating), as they all have ranges.
- Using stratigraphy, the fossil found in the same strata is the same age as the index fossil, ____.
Yes, you are correct here as well, but because the unknown fossil is more often than not in another strata from the index fossil used, the index fossils are often used in conjunction with the principle of superposition (which states that rock strata are arranged in a order of progressing age, with the newest at top, in normal conditions). That is to say, if there is a fossil of unknown age and it is found below an index fossil, it can be inferred that the unknown fossil is older than a certain age (i.e. that of the index fossil); and vice versa.
So if the question asked whether using index fossils is absolute or relative (point 2) what would be say?
Relative - because the age of the fossil is being determined by using the index fossil nearby?
or Absolute - because the NUMERICAL value of the fossil is known because of the INDEX fossils whose NUMERICAL age is also known?
Relative. If an index fossil is used it is always relative. Because it is in relation -- or in other words, relative to -- the index fossil (also links back to my previous point that the unknown fossil is more often than not, in a different rock strata to the index fossil, so the approximate numerical age is not known anyway).
Hope this helps 
.
Moskva
Thank you it makes sense. But this VCAA question is kind of confusing, like I understand the answers but I'm confused on how to categorize it. 2018 NHT 7 b and c in which it asks how the ABSOLUTE AGE can be determined using the ancient mollusk (similar to index fossils in the sense of providing RELATIVE age), so it is a relative dating technique that can provide ABSOLUTE AGE or it is an absolute dating technique.
Thank you once again
- Edited
God
Hi,
I agree with your first point. But in that VCAA question by determining absolute age of the igneous rock you could determine the absolute age of the ancient mollusk (as specified in the stem) by using relative dating techniques, since its found in the same stratum (after first using absolute dating techniques on the igneous rock), so would finding the relative age of the ancient mollusk (in the same stratum as the dated igneous rock) be used to determine its absolute age of 50 my???? So is it also possible for it to be the other way around????
So all in all what technique would it be: absolute or relative???
- Edited
Question Stem: The scientists justified that the P. portelli fossil is 50 million years old by referring to fossils of several ancient molluscs.
Exam Report: The radiometric dating is done on igneous rock layers associated with the sedimentary layers in which the fossil molluscs have been found elsewhere in the world
Ahhh...I think I understand what you're saying. In this case, it would be a relative age of the fossil. (Made more accurate as the index fossil is tested many times in many places) (The age of the rock would be absolute)
Hello again tubes
But in that VCAA question by determining absolute age of the igneous rock you could determine the absolute age of the ancient mollusk (as specified in the stem) by using relative dating techniques, since its found in the same stratum (after first using absolute dating techniques on the igneous rock),
You misinterpreted the VCAA question (/suggested answer).
Scientists take samples of igneous rock from igneous rock strata above and below the mollusc fossils. Then they use the ratio of Potassium-40 to Argon-40, and the half-life value of Potassium-40 to calculate the age of these igneous rock strata. Since the mollusc is in between these two strata of igneous rock scientists can kind of average the two values and get an approximate age* of the mollusc fossil. This is absolute dating.
*I know the name of the dating method would suggest that it yields an absolute value, but unfortunately it is not always possible to directly date a fossil.
- Edited
Hi guys, I was just wondering if any of you could review and guide me with answering Question 9 of the sample examination for 2022 VCE.
a) Homo heidelbergensis that evolved into Homo sapiens 300,000ya in Africa and then migrated to Australia 50,000 ya. Already present before the arrival of the ancestors of Indigenous Australians was Homo erectus - an earlier hominin- that had previously migrated out of Africa and had diverged into Homo floresiensis in Indonesia also coexisted with Homo sapiens.
b) Migration to Australia occurred in 2 distinct pathways, were one group reached and travelled along the East coast 40,000 ya and the 2nd group travelled across the western coast and settled 41000, because the 2 main groups were geographically isolated by Australia's mainland, gene flow was limited and hence different mutations occurred and accumulated in each population's genome
c)i) Evidence of art (cultural evolution) such as cave paintings
The presence of stone tools
c)ii) The large genetic variation in mtDNA indicates that a long time had elapsed since migration hence the time for mutations to accumulate, supporting a continuous presence in Australia as well as in discrete areas as many different mutations occurred in specific isolated population and hence accumulated because of the lack of gene flow leading to 111 mtDNA genomes to diverge
Thanks
Hello hello tubes!
Ah, human evolution question! My [least] favourite! 
I will try to give some tips, advice, and some suggested answers. However please note that I am not a teacher, so other advice (i.e. from your VCE Biology teacher) is highly recommended.
a) Which currently known hominin species is most likely the ancestor of Aboriginal Australians? Explain
your response by referring to the different species and other information presented in the article. (3 marks)
a) Homo heidelbergensis that evolved into Homo sapiens 300,000ya in Africa and then migrated to Australia 50,000 ya. Already present before the arrival of the ancestors of Indigenous Australians was Homo erectus - an earlier hominin- that had previously migrated out of Africa and had diverged into Homo floresiensis in Indonesia also coexisted with Homo sapiens.
You should make it clearer which hominin species you are selecting for your answer (e.g. "Homo heidelbergensis, evolved into Homo sapiens...").
The question stem specifically asks for an explanation using hominin species referenced in the provided article, you made a tangent which references hominins referenced in the article; these are very different things.
In this question/example, Homo denisova would have been the best hominin species to reference in your answer, because we are told (presented information) that Aboriginal Australians share some common DNA with H. denisova. Even more compelling evidence presented in the article is that it specifically states no other currently known ancestral species shares similar nuclear DNA with Aboriginal Australians.
b) Comparisons of genomes of Aboriginal Australian populations on the west coast and east coast suggest
that there were two distinct pathways of migration across Australia.
Using supporting evidence from the article, explain likely reasons for the differences seen in the
genomes of the populations. (2 marks)
tubes b) Migration to Australia occurred in 2 distinct pathways, were one group reached and travelled along the East coast 40,000 ya and the 2nd group travelled across the western coast and settled 41000, because the 2 main groups were geographically isolated by Australia's mainland, gene flow was limited and hence different mutations occurred and accumulated in each population's genome
This is good, you have the main guts of it down; as you mentioned gene flow is limited and accumulation of different mutations lead to differences. I would only suggest polishing it up a little bit.
E.g.
- Migration to Australia, by who?
- Be more precise in how gene flow is limited, mainland is usually a means of gene flow.
- Also be more precise that a large amount of time has elapsed in order for the mutations to accumulate.
Overall pretty good answer for this part, goodjob 
️
c) Analysis of mtDNA from Aboriginal Australians and phylogeographic patterns support the contention
that there was a continuous presence of distinct populations in discrete geographic areas for up to
50000 years.
i) Identify two types of artefacts that may be found in a particular geographic area if Aboriginal
Australians had lived in that area for long periods of time (thousands of years)? (2 marks)
i) Evidence of art (cultural evolution) such as cave paintings. The presence of stone tools.
VCAA has specifically stated in their 2022 VCE Biology FAQs that "...ability to distinguish between biological evolution and cultural evolution is not required."
So I think this is a typical case of VCAA blunder, and am not so sure you will encounter such questions on the end of year exam.However, in the case that it does show up, answers such as cave paintings, burial sites... etc. are perfectly fine, I think (stress "I think"
).
ii) Explain how mtDNA phylogeny provides evidence for the continuous presence of Aboriginal
Australian populations in discrete geographic areas. (3 marks)
ii) The large genetic variation in mtDNA indicates that a long time had elapsed since migration hence the time for mutations to accumulate, supporting a continuous presence in Australia as well as in discrete areas as many different mutations occurred in specific isolated population and hence accumulated because of the lack of gene flow leading to 111 mtDNA genomes to diverge
This is a hard question. I had to think about it for a while. What do they mean by continuous presence?
The question asks for an explanation, you need to give a structured and logical line of thought in order to explain this.
Perhaps you could say "When Aboriginal Australian populations formed in discrete geographic locations, they became isolated from other populations; which then limited gene flow between these populations. Consequently, over long (and continuous) periods of time, differences in their gene pools from mutations, natural selection and genetic drift accumulated. MtDNA phylogeny can serve as evidence of these differences, and hence the continuous presence of these populations."
Or perhaps we can take a different angle of attack and say "Large differences between genetics of Aboriginal Populations of discrete geographical areas illustrated in mtDNA phylogeny, evidence that these populations have been established a very long time ago and have been continuously present. As those are the conditions required for these differences to arise, conditions required for factors such as lack of gene flow, different mutations, different natural selection pressures acting, and genetic drift to act on these populations; and create such differences."
Feel free to add anything to these "suggested" answers (or dispute their validity), I feel like VCAA expects a fairly meaty answer for this type of question; perhaps some more information from the article can be utilised?
Be careful, as it is very easy to fall into the trap of making an answer which uses false logic/circular reasoning for this sort of question, yuck
.
Hope this helps!
(Apologies if I may have used harsh wording.)
Hey! Just wondering if the action of mRNA exiting the nucleus and traveling to the ribosome should be included as part of transcription or translation? Thanks!
chimichurri
I'm gonna guess neither. (As it is not being created / copied)
- Edited
Hey chimichurri!
VCAA probably wouldn't ask you about this specifically.
I would only include it in the context of a Translation question.
️
Hey guys. I was thinking about c)ii) from the sample exam, and an idea came up to use "111 mitochondrial genomes exist" as how "mtDNA phylogeny provides evidence" Just wondering if my line of thought would be correct:
"Genomes" suggests that they are distinct gene pools (in terms of mtDNA). If gene flow was possible between these populations there would be one genome with high variation not separate genomes
Hence they must have been present in Australia for the genetic variations caused and accumulated by natural selection, genetic drift and mutations for the genomes to become separate/"diverge"
- Edited
thanks for your help guys! also, why does pre-mRNA read the template strand (in transcription) in a 3' to 5' direction? Isn't DNA usually read in a 5' to 3' direction?
Also, I had been taught that one gene coded for multiple amino acids but then isn't an operon made of multiple genes that code for the one amino acid? Is that right? What's the difference between a gene and an operon here?
hi
- Edited
Hi chimichurri!
Let me try and explain how operons/genes work.
Firstly, remember that a gene is a section of DNA that codes for a specific protein. Of course, genes are found in both eukaryotes and prokaryotes. A gene will code for multiple amino acids, forming a polypeptide chain that can be folded to form a functional protein. An operon is generally only found in prokaryotes, and its a cluster of linked genes that all share a common promoter and operator, and are transcribed at the same time. Generally, all of these genes are related by function (i.e. biochemical process that they are a part of). Now, the genes in the operon are structural genes (genes that don't code for regulatory proteins, but instead proteins needed for structure or cellular functioning). The trp operon (that you need to know about from the study design) consists of multiple structural genes and has a structure like the following:
3' end - Promoter - Operator - Leader (TrpL) - Attenuator - TrpE - TrpD - TrpC - TrpB - TrpA - Trailer - 5' end
TrpE to TrpA are your important structural genes. As we know, genes code for many amino acids, so an operon is not going to just code for amino acid. It is easy to think that the trp operon codes only for one amino acid, that being tryptophan (since the process can be quite confusing to understand). However, the trp operon actually codes for multiple polypeptides, each structural gene being transcribed and translated to form different proteins (specifically enzymes) that are required to produce tryptophan. Here are some details on the enzymes formed (don't need to know the specifics, but it can be helpful in understanding how it works).
- TrpE and TrpD -> Form enzyme Anthranilate synthase, which converts chorismate (found in the cell) into anthranilate.
- TrpC -> Forms enzyme Indole-3-glycerol-photosphate synthase, which converts anthranilate into indole-3-glycerol-photosphate.
- TrpB and TrpA -> Forms enzyme Tryptophan synthase, which converts indole-3-glycerol-photosphate into tryptophan.
(Requires lots of energy, meaning the process needs to be tightly regulated via attenuation and repression mechanisms).
To put it simply, the enzymes are produced to convert certain chemical products into tryptophan, with each enzyme consisting of many amino acids that form polypeptides and therefore are folded into functional proteins (i.e. enzymes). Hopefully that makes sense.
With directions, it can be quite confusing. RNA polymerase (not pre-mRNA) reads the strand in a 3' to 5' direction, forming an mRNA strand (mRNA for prokaryotes, but pre-mRNA for eukaryotes) that is 5' to 3' (due to complementary nature of DNA transcription). DNA replication is the same, as DNA polymerase reads the strand from 3' to 5' and writes a new DNA strand from 5' to 3'. I remember it like this: "When we study, we read up on a topic (3' to 5'), and then you write it down (5' to 3')". That said, google makes it kind of confusing by saying that DNA is read 5' to 3', but I'm assuming that it is referring to the fact that whilst the template strand being copied in a complementary manner is the 3' to 5' direction, the actual coding strand that is being replicated is 5' to 3' (which is why the created DNA or RNA strand is always written in a 5' to 3' direction). I might be wrong about that though. Not sure if that makes sense, since I'm still trying to wrap my head around how it works haha.
how does natural selection contribute to allopatric speciation
chemistry1111
Allopatric speciation begins with a species population being separated due to a geographical barrier (e.g. ocean, mountain ranges, vast desert, etc.). These populations will therefore be exposed to different environmental selection pressures, resulting in the accumulation of genetic differences. During this process, natural selection will confer an selective advantage to members of these populations that carry advantageous alleles, of which increase their fitness and ability to survive when exposed to these different selection pressures. It is important to note that of course, the selection pressures will vary and therefore the members of each population selected for and against by natural selection will differ. Over time, this process of natural selection will result in the population members being unable to interbreed if they come in contact with each other (i.e. the geographic barrier is removed), as they will no longer be able to produce viable and fertile offspring.
Hello there,
Can someone please explain to me why fermentation must not allow the presence the oxygen to happen successfully? (Like I get it's because that's anaerobic respiration but I don't know what would happen if we have oxygen present in it?).
Cheers 
I'm not sure on the bio-mechanics of it all - perhaps its got to do with the build up of pyruvate molecules - but the gist of it is:
Aerobic respiration is more efficient. So it will be conducted when sufficient oxygen is available.
Fermentation will occur when there is not enough oxygen - as it provides an alternate means of re-cycling the NADH molecules.
Hello there,
Can someone please explain to me the process of monoclonal antibodies and how effective this method is when we use it as a treatment for a disease?
Kind regards
- Edited
hey, what is the difference between coding strand
chemistry1111
Hi
The template strand only serves as the template for transcription (so this template strand is often from DNA, and is used to transcribe into mRNA). Whereas, the coding strand contains the exact same sequence of nucleotides in the mRNA except for thymine.
Hope this helps
_sophiestudies_
Thank you so so so much! I understand now
hi all! sorry if someone's already asked this question:
does anyone know if there are solutions available for the 2022 sample bio exam on the vcaa page? and if so where they are located?
my teacher literally made the class complete it under timed conditions and everything but we can't even correct our work...
thanks in advance!
-bw
bw304 I don't think there are any solutions (VCAA doesn't seem to ever give sample exam solutions for any subject, which is really annoying). You might need to ask your teacher for answers, or see if they can mark it for you.
Can someone please explain part b of this question from the 2019 VCAA exam? Like i get that the mitochondrial DNA of the girl’s finger bone will be very similar to the mtDNA of her female ancestors, but I dont get why. MtDNA has a high mutation rate but it remains relatively unchanged from one generation to another- can someone pls explain what the concept is behind mtDNA and how that links to this question? Cos the way the edrolo textbook has explained it is kinda contradictory..
Also can someone explain Q4 from the 2020 VCAA exam’s multiple choice section? How do we know that substrate B is gonna be a competitive reversible inhibitor? I actually thought substrate B wouldn’t even bind to the active site cos its not forming a product - I’ve been a bit confused with these two questions since yesterday so if someone could help clarify this in detail that’d be great. Thanks so much!
With the 2020VCAA question - I think the clue is that is says 'an enzyme-substrate complex was formed in each of the three test tubes'. This indicates that both substrates have bound to the enzyme. Then - I think its a matter of trial and error.
Intuitively, i would expect it to either decrease - or stay the same. Then going through each option:
Option A) can't be true because - it doesn't make sense. The only way substrate A & B could both bind at the same time would be if B was an allosteric inhibitor - in which case you would expect to see no product. But the option says it would be the same as testube 1. It could be a co-enzyme - but then you would expect test-tube 1 to have no product produced.
Option B) can't be true because substrate b can form an 'enzyme-substrate complex'. Which means, some of the time it will be bonded to the active site. Hence the rate of reaction would decrease - as it doesn't actually make a product when bound.
Option C) sounds ok.
Option D) sounds ok.
Now I'm not 100% sure on the logic to differentiate between C & D. Looking through my old prac exams from last year - I chose C. I think this is why:
Whenever an answer says something definite - like ' zero' product produced - I tend to doubt it. Even if it was an irreversible inhibitor - some product (theoretically) would still get produced.
Apologies for the long-winded response. Maybe someone else can help more.
Also - Mitochondrial DNA is passed down from mother to child. (Unlike chromosomal DNA which is 50/50 split from mother/father)
Without reading the article - I presume the time-span was too small to pickup any differences in mitochondrial DNA. It could also be that - due to recent interbreeding between the two species - the girl could have mtDNA of her mother's species. Which might be very different to her father's.
Hello Smartiestarz!
Can someone please explain part b of this question from the 2019 VCAA exam? Like i get that the mitochondrial DNA of the girl’s finger bone will be very similar to the mtDNA of her female ancestors, but I dont get why. MtDNA has a high mutation rate but it remains relatively unchanged from one generation to another- can someone pls explain what the concept is behind mtDNA and how that links to this question? Cos the way the edrolo textbook has explained it is kinda contradictory..
mtDNA does not change from generation to generation as much as nuclear DNA because it does not undergo recombination. It is solely inherited maternally (well... in most cases anyways).
Think about it like this; suppose you have a deck of cards. Which would result in a more drastic change?
- Changing, adding, or taking away a card every now and then.
- Shuffling the cards, and replacing half of them from another shuffled deck.
Scenario 1 would be comparable to spontaneous mutations in mtDNA, and Scenario 2 would be comparable to genetic recombination. Sure, mtDNA may accumulate mutations faster than nuclear DNA, but it is still relatively insignificant when compared to nuclear DNA recombination.
Also can someone explain Q4 from the 2020 VCAA exam’s multiple choice section? How do we know that substrate B is gonna be a competitive reversible inhibitor? I actually thought substrate B wouldn’t even bind to the active site cos its not forming a product
This was a bad question. Usually we would not call an inhibitor a "substrate" at all, we would call them inhibitors.
Basically you had to choose the most plausible option, option C. The other options didn't really have any coherence.
- Option A - Why does both substrate being able to bind to the enzyme simultaneously result in same product output?
- Option B - How would product output change if the same amount of substrate is added?
- Option D - If substrate B was an irreversible inhibitor, then why are the enzyme and substrate B shown as separate for the results of test tube 2?
Again, the question is pretty bad. Is the experiment under timed conditions? If not, reversible competitive inhibitor shouldn't make a difference in the end... etc.
Hey! So enzymes increase the reaction rate by lowering the activation energy required for a reaction, I was wondering how enzymes do that? I've read that an example of how they lower the activation energy is by bringing reactants together which reduces the amount of energy they use moving around until they collide, is this the only way that they reduce the activation energy?
Hello there
Can someone please explain to me the process of monoclonal antibodies and how effective this method is when we use it as a treatment for a disease?
And also, for example, if someone has a transplanted organ, what's the specific type f cell that helps in identifying that organ? (Why does it has to be "helper T lymphocyte" but not other immune cells?
=> I came across that question on a practice exam:
Transplanting organs such as lung, heart, liver and kidney have become routine operations over recent years. Only the shortage of donors limits the number of transplants that can be performed.
a. What is the name of the specific type of cell that can identify an organ that has been transplanted?
Cheers.
- Edited
Hi NG900! Let me see if I can be of any help!
So, firstly, monoclonal antibodies are identical lab-made antibodies produced by plasma cell clones, which can be used as an immunotherapy treatment (antibody therapy). They can be both used to activate the immune response (induce/amplify to treat cancer) or suppress the immune response (prevent or reduce to treat autoimmune diseases). I'm assuming your question is referring to how they work, not the production process, but correct me if I'm wrong.
Here are some examples of how they can be used in the body (but not limited to):
Antibody-dependent cell-mediated cytotoxicity - Activation immunotherapy:
- Bind to cancer cells and interact with immune system cells, particularly NK cells (natural killer cells), causing them to recognise the cancer cell coated in antibodies as foreign.
- Helps them kill the cancer cells.
Complement activation - Activation immunotherapy:
- Bind to cancer cells and interact with complement proteins (remember, these are proteins found in the body that opsonise, cause lysis, and attract phagocytes to invading pathogens).
- This interaction aids in helping the complement proteins recognise the cancer cells as foreign, creating membrane attack complexes to kill the cells or enhancing the functions of other immune cells.
Checkpoint inhibition - Activation immunotherapy:
- Immune checkpoints -> Regulate immune system, and when activated, suppress the immune system. This is important for normal bodily functioning, but cancer cells can secrete molecules that stimulate these checkpoints, reducing the ability for the immune system to recognise and destroy them.
- Monoclonal antibodies -> Block immune checkpoints, meaning immune system can function at a grater capacity and destroy the cancer cells more easily.
Cytokine inhibition - Suppression immunotherapy:
- Cytokines = Messenger molecules used by immune system to coordinate an immune response.
- Monoclonal antibodies -> Bind to and inhibit cytokines to suppress the immune response.
B cell and T cell depletion and inhibition - Suppression immunotherapy:
- They bind to autoreactive (cell that recognises self-tissue/self-antigens as non-self) B and T cells -> This can act as a means of inhibiting these cells, or stimulate other immune cells to destroy these autoreactive B and T cells.
Now, how effective are monoclonal antibodies in comparison to tradition treatments.
Cancer treatment (activation immunotherapy):
- Benefit -> More specific and targeted in attack, unlike traditional treatments (chemo and radiotherapy) that target all rapidly dividing cells (means other cells of the body are impacted, such as hair and cells lining gut - results in hair loss, nausea, etc.) This is due to their variable regions that bind with cancer antigens specifically, meaning their is a lower chance of other cells in the body being effected by the treatments and lower side effects.
- Benefit -> Can be used to stimulate the immune system to recognise and destroy cancer cells, unlike traditional treatments that directly kill cancer cells.
- Con -> Still has a wide range of side effects, such as fatigue, fever, nausea, shortness of breath. However, it is still generally less than traditional treatments and does depend on the type immunotherapy being used.
- Con -> Only available as a treatment for very specific types of cancers, and is still used in conjunction with other traditional treatments.
Autoimmune disease treatments (suppression immunotherapy):
- Benefit -> Prevents overall immunodeficiency, which is occurs with traditional treatments that try to reduce the symptoms of the patient by suppressing their whole immune system (immunosuppression). This causes the individual to be more prone to developing cancer and infections. Monoclonal antibodies prevent this because only specific autoreactive cells are being targeted, meaning the rest of immune system can function normally.
- Cons -> Same as cancer treatment cons. It is still used in conjunction with traditional treatments due to not being widely available, and can have some side effects.
I hope that helps. Let me know if you were actually asking about the production process of monoclonal antibodies, not their uses (wasn't 100% what you were asking, that's all).
Now, with your second question, the specific type of cell is indeed helper T lymphocytes. This because these are the cells that are presented with the foreign antibodies by antigen presenting cells (aka dendritic cells, macrophages, and B cells). Obviously, these cells will also identify that their is something foreign in the body, but the helper T lymphocyte is required to actually recognise this and stimulate a specific adaptive immune response against the transplanted organ. Not sure if that makes sense, but that's how I interpret the question and their answer.