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PhoenixxFire

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Challenging biology questions
« on: December 22, 2018, 12:26:17 pm »
+13
All of these questions are past VCAA questions that were poorly answered (below 50% of the state got full marks). Please don't be worried if you don't know how to answer these, they are ones that most of the state did not correctly answer in the exam! I've included a prompt in a spoiler below each question to help you if you don't know how to start on it.

The solutions and a new set of questions will be posted each Monday.

Please write your solutions in a spoiler and include the number of the question you are answering. To use a spoiler, copy the code below into your post.
Code: [Select]
[spoiler]Write your answer here[/spoiler]
There is no requirement to attempt all of these, feel free to do as many as you would like throughout the week :)

Questions: Week 1
Multiple choice:
Question 1

Prompt
For this question you need to consider the separate chemical equations for each of the stages of photosynthesis.

Question 2

Prompt
The simplest way to work out this question is to start by crossing out the wrong answers.

Question 3

Prompt
To work out this question, go through each of the possible options. It may help to draw arrows showing the direction of water movement.

Question 4

Prompt
Begin by crossing out the wrong answers.

Question 5

Prompt
Go through each of the options to work out the answer for this.

Question 6

Prompt
This question relies on knowledge of what is considered normal cell death and what is not. Cross out any options that are considered normal.

Short answer questions:
Question 7

Prompt
Consider the inputs of cellular respiration.

Question 8

Prompt
Pay close attention to the number of marks allocated, you are required to include two pieces of information in this question.

Question 9

Prompt
The trick with this question is answering it in the correct depth. Pay attention to the command word (Explain) used in this question.

Question 10

Prompt
c. Consider what is necessary for carbon dioxide to be able to leave blood cells
f. Consider what factors may be affecting the rate of photosynthesis

Note: If the image appears stretched out click on it to resize it.

Week 2 questions
« Last Edit: January 14, 2019, 11:08:26 pm by PhoenixxFire »
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Re: Challenging biology questions
« Reply #1 on: January 07, 2019, 12:35:20 pm »
+1
More incredible work by PhoennixFire :)


I'd highly encourage biology students to have a shot at these - when I was studying biology I found completing practice questions throughout the whole year to be incredibly valuable. I cannot understate how important practice questions were for me as a biology student; please take advantage of PFs contributions :)


(PF created this post in advance for the start of the science games, note that "this week" refers to the week starting today and not to December)

Erutepa

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Re: Challenging biology questions
« Reply #2 on: January 07, 2019, 05:53:09 pm »
+1
Multiple choice:
Question 1
A - glucose is a product of the dark reaction

Question 2
B - Structure x is the site where 6-carbon compounds are produced

Question 3
A - Solution P is hypertonic to the cytosol of the red blood cell
B - Solution Q has a higher water concerntration than the cytosol of the RBC

Question 4
B - ribosomes are the site of polypeptide synthesis

Question 5
D - both require the use of proteins and carriers

Question 6
C - the development of breast cancer

Short answer questions:
Question 7
Glucose

Question 8
By attacking the mitochondria, manosonomes may prevent or reduce the ability of the fungi’s mitochondria to undergo cellular respiration, thus reducing or preventing the production of ATP. As a result of a reduced availability of ATP in the fungus cells, the cells may lack the required energy to facilitate vital cellular metabolism and thus die.

Question 9
The purpose of a saline solution was to serve as a negative control test whereby the saline should have no effect on clearing the infection, allowing the evaluation of the efficacy of the vaccine in treating the infection.


Question 10
c) through the constant conversion of carbon dioxide into bicarbonate ions within RBC, a concentration gradient is established whereby carbon dioxide is in a higher concentration in the body cells and a low concentration in the blood cells, facilitating the movement of carbon dioxide from the body cells, through the blood plasma and into the red blood cells.

f) The graph shows that the concerntration of carbonic anhydrase reaches a constant indicating that the rate of carbon dioxide production from the conversion of bicarbonate ions in the water reaches a constant rate. As the rate of photosynthesis increases, the rate of carbon dioxide intake also increases. As such, by minute 90, carbon dioxide concentration may have acted as a limiting factor, thus causing a constant rate of photosynthesis
« Last Edit: January 09, 2019, 08:20:20 pm by Erutepa »
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alexthenerd

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Re: Challenging biology questions
« Reply #3 on: January 09, 2019, 08:02:06 am »
+3
my answers:

Spoiler
Question 1: A
Question 2: B
Question 3: C
Question 4: B
Question 5: D
Question 6: C
2019: biology (42)
2020: english language, methods, chemistry, further, music performance

PhoenixxFire

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Re: Challenging biology questions
« Reply #4 on: January 09, 2019, 05:11:21 pm »
+2
Question 3
A - Solution P is hypertonic to the cytosol of the red blood cell
Spoiler
You've written a correct statement here but it doesn't match what option A in the question is.

Question 9
The purpose of injecting some mice with a saline solution was to serve as a negative control test whereby the saline should have no effect on clearing the infection, allowing the evaluation of the efficacy of the vaccine in treating the infection.
Spoiler
If you're trying to be more concise, there's no need to include the first part of this - you don't need to reintroduce the topic. You can just write 'The saline solution was used as a negative control...'

Question 10
c) through the constant conversion of carbon dioxide into bicarbonate ions, a relatively low concentration of carbon dioxide in the red blood cell is maintained. This establishes a concentration gradient whereby carbon dioxide is in a higher concentration in the body cells and a low concentration in the blood cells, facilitating the movement of carbon dioxide from the body cells into the red blood cells.

f) At minute 90, the rate of photosynthesis was the same as the concentration of the enzyme carbonic anydronase. As a result, the rate at which carbonic anydronase produced carbon dioxide from the conversion of bicarbonate ions in the water, and the rate of carbon dioxide intake from photosynthesis may have been equal. As such, carbon dioxide concentration may have acted as a limiting factor, thus causing a constant rate of photosynthesis
Spoiler
c). You've got the right idea but you've explained it a bit wrong. You've need to refer to the CO2 concentration in the blood stream - CO2 is going from the body cell into the blood plasma and then into the RBC, so you need to talk about why this conversion allows that. You've only talked about the body cells and RBC.

f). The rate of photosynthesis and the concentration of the enzyme were not exactly the same, this also doesn't matter - if the graph showed the amount of CO2 produced and the rate of photosynthesis then it might matter. Your second statement here is getting at the right idea but not something that can be determined from this graph. Your conclusion is correct but you also need to say why carbon dioxide became the limiting factor. Consider what is stopping more bicarbonate ions from being converted into CO2.
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Erutepa

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Re: Challenging biology questions
« Reply #5 on: January 09, 2019, 08:25:26 pm »
+1
Spoiler
You've written a correct statement here but it doesn't match what option A in the question is.
Spoiler
If you're trying to be more concise, there's no need to include the first part of this - you don't need to reintroduce the topic. You can just write 'The saline solution was used as a negative control...'
Spoiler
c). You've got the right idea but you've explained it a bit wrong. You've needed to refer to the CO2 concentration in the bloodstream - CO2 is going from the body cell into the blood plasma and then into the RBC, so you need to talk about why this conversion allows that. You've only talked about the body cells and RBC.

f). The rate of photosynthesis and the concentration of the enzyme were not exactly the same, this also doesn't matter - if the graph showed the amount of CO2 produced and the rate of photosynthesis then it might matter. Your second statement here is getting at the right idea but not something that can be determined from this graph. Your conclusion is correct but you also need to say why carbon dioxide became the limiting factor. Consider what is stopping more bicarbonate ions from being converted into CO2.
Thanks a heap PF!
This is really great advice and I completely understand everything you are saying.

For MC question 3, it was a simple misreading and I re-answered the question.

For question 9, I cut out the redundant information as per your recommendation.

For question 10, I took on board the advice and tried to fix up the responses, although I am still not quite satisfied with them. Effectively communicating my thought process is one of my poorer skills which probably dragged me down a bit this year in bio.
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PhoenixxFire

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Re: Challenging biology questions
« Reply #6 on: January 14, 2019, 02:26:33 pm »
+3
Week 1 answers
MCQ
1 - A
2 - B
3 - C
4 - B
5 - D
6 - C

SAQ
7 - Glucose or amino acids or fatty acids

8 - Fewer mitochondria means that less ATP is produced.
and
Energy dependent cellular processes cannot occur, the fungus
will die.

9 - To act as a point of comparison with the vaccine injected mice
(experimental group) to show that the vaccine enabled the mice
to eliminate the bacterium.

10c - Continual use of carbon dioxide to produce bicarbonate that
can readily leave a red blood cell means that carbon dioxide
will continually diffuse into a red blood cell from plasma.
AND
This creates a concentration gradient in which carbon dioxide
is lower in plasma than it is in cells so carbon dioxide will
move from cells into plasma.

10f - Chlorella has reached its maximum rate of production of
carbonic anhydrase, hence level of carbon dioxide remains
constant. Therefore, carbon dioxide becomes the limiting
factor for photosynthesis.
Happy to go through them if anyone has questions about them :)

Week 2 questions
MCQ
1

prompt
To answer this you need to know whether smaller or larger fragments travel faster in agar gel

2

prompt
Adenine can only bond to thymine, guanine can only bind to cytosine. The total of all bases must add up to 100%

SAQ
3

prompt
There are two types of dating - relative or absolute, note that this question asks about relative dating

4

prompt
This is a fairly standard question asking you to explain how a genetic trait that is selected for comes to be present in a disproportionate number of individuals in future generations.

5a-b

prompt
The haemoglobin protein is important and as such is highly conserved - this means it may be the same in different species. Consider the redundancy of DNA when answering part b.

5c-d

prompt
pay attention to the wording of part d and note that stop codons do not add an amino acid.

6a-c

prompt
This is fairly straightforward, you just need to pay attention to what bases are present in mRNA vs DNA and what base they can bind to. Make sure not to include too much information - each part is only worth 1 mark.

6d-e

prompt
This is a fairly straight forward process question - try to be as direct as possible in your answer, don't include unnecessary information.

7

prompt
The child would have received one allele from each of their parents - so if you have fragments from both parents you should be able to match an allele in the child to one in each of the mother and father.

8

prompt
In order to test that the trait is under genetic control, you need to eliminate differences in environment.

9

prompt
You need to ensure that your answers here are specific - you should refer to features of that region, pollen, or that timeframe that may have prevented fossilisation.

10

prompt
This is a fairly standard speciation question, you need to talk about the 3 steps required for speciation - geographical isolation, differing selection pressures, and differences accumulating over time.

Sorry about the lack of Multi choice questions this week - the ones from the exams I went through were generally well answered.

As before, attempt as many or as few as you would like :) If you haven't done last week's questions you're welcome to try them too
« Last Edit: January 16, 2019, 03:05:24 pm by PhoenixxFire »
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Erutepa

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Re: Challenging biology questions
« Reply #7 on: January 14, 2019, 07:14:28 pm »
+2
Thanks again for your hard work in collating these!

Week 2 questions
MCQ
1

D - The plasmid is approximately 6kb

2

B - 32% of the bases were cytosine

SAQ
3

The relative age of the fossil can be determined through its relative position to index fossils of known age. The concept of superposition suggests that if the discovered fossil is in the same strata as the index fossil it will be the same relative age, or if the discovered fossil in in the strata above or below the index fossil it will it will be younger or older, respectively.

4

The myxoma virus is a selective agent which acts on wild rabbit populations with infected individuals potentially developing the fatal disease myxomatosis. Within wild rabbit populations exposed to this selection pressure, individuals who possessed a genetic resistance to the myxoma virus would have had a greater chance at survival, thus being 'selected' and having greater reproductive success than susceptible rabbits. As a result of this, wild rabbits with genetic resistance to myxoma virus would have contributed disproportionately greater to the gene pool of subsequent generations, such that over time this action of natural selection would have brought about the increase in resistance rabbits as seen in the above graph.

5a-b

a) Species 1
b) Since chimpanzees are the closest living relative to humans, they would likely possess a B-globin sequence of the greatest degree of similarity which is shown in the above table to be species 2.
 
c) this difference in variability is due to the redundancy of the genetic code. Since each amino acid can be coded for by multiple DNA triplet codes, some changes, or variation, in the DNA sequence for the B globin gene may not always result in changes, or variation, in the amino acid sequence.

5c-d

c) the first base of the 6th codon of HBA has changed from a G to an A
d) this point substitution would cause the 7th codon to become a 'stop' codon. This would cause the synthesis of a truncated B globin mutant of only 6 amino acids long.

6a-c

a) the presence of uracil instead of thymine indicates that the sequences are mRNA and not DNA
b) the first base of the DNA triplet complementary to the 4th mRNA codon shown above would have changed from G to A.
c) as a result of this mutation, the amino acid coded for by the 4th codon changes from arg to cys.

6d-e

d i)transcription
d ii) Transcription is initiated by the binding of RNA polymerase to the promoter region in the presence of necessary transcription factors. RNA polymerase unwinds the DNA helix and proceeds down the DNA template strand reading in the 3' to 5' direction while synthesizing a complementary mRNA strand in the 5' to 3' direction.
e)
restriction enzymes cut the DNA sequence at specific recognition sequences and different restriction enzymes have different unique recognition sequences.
Restriction enzymes can cut the DNA to produce restriction fragments with sticky ends (ends with exposed single-stranded DNA) of blunt ends.
 

7

Each band on the gel represents a specific number of repeats and thus specific alleles for the D1S80 locus with each individual shown possessing two distinct alleles. Since each parent contributes one allele for the D1S80 locus to the child, the mother must contribute the allele represented above by the closer band to the child, and as such the paternally contributed allele must then be that of the further band. Since the proposed father does not possess this paternally contributed allele, then he is not likely the actual biological father.

8

Corn plants from each farm were obtained and separately planted in two identical pots and were left under the same conditions (e.g same temperature, same light exposure, same soil) with their each of their mature highest being recorded. This was replicated using corn from each farm multiple times under the same conditions and their final hights recorded. If the height of the corn was under genetic control, then the results would show that in the same conditions, the corn from the farm which grew taller corn would have consistently grew taller than the corn from the farm which grew the shorter corn.

9

i) the conditions at richmond basin before 228 mya was not suitable for fossilisation of the polen
ii) before 228 mya steevesipollenites did not exist in richmond basin, thus could not have been fossilized

10

When rising sea levels separated Pedra Branca Rock from mainland tasmania, an ancestral skink population would have been separated into two distinct genetically isolated populations between which, no gene flow could occur. Over time, due to random mutation and the action of different selective pressures, differences would have accumulated between the two skink populations. This divergent evolution would have given way to the unique Niveoscincus Palfreymani species of skink once they had become reproductively isolated from other mainland skink species.

« Last Edit: January 15, 2019, 07:25:14 pm by Erutepa »
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PhoenixxFire

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Re: Challenging biology questions
« Reply #8 on: January 15, 2019, 12:38:19 pm »
+2
3

Since limestone is a sedimentary rock and as such cannot be dated reliably itself, nor can the fossil be carbon dated, the scientists could have used potassium-argon dating to estimate the age of igneous rocks found within the same strata as the discovered fossils. Since the dated igneous rocks and fossils are in the same strata, as implied by the law of horizontal continuity, they will be the same age, thus the estimated age of the igneous rocks would give the scientists an estimated age of the fossils.
Spoiler
Your answer is feasible but it relies on a fair bit of luck (there happening to be igneous rock in the same layers) and is far more complicated than necessary. The question is only worth 1 mark, and note that it asks about the relative age of the fossils - there's a much simpler answer. Also worth considering that potassium-argon dating wasn't used until the early 1900's (although you wouldn't really be expected to know that).

4

The myxoma virus is a selective agent which acts on rabbit populations. The increased exposure of wild rabbit species to the Myxoma virus in the early 1950s as part of the reduction of wild rabbit population numbers, increased the selective pressure on the wild populations. Within wild rabbit populations exposed to this selection pressure, individuals who possesed a genetic resistance to the myxomia caused by the myxoma virus would have been selected for and had greater reproductive success than susceptible rabbits. As a result of this, wild rabbits with genetic resistance to myxomia would have contributed disproportionately greater to the gene pool of subsequent generations, such that over time this action of natural selection would have brought about the increase in resistance rabbits as seen in the above graph.
Spoiler
Your answer is totally fine as it is, but given you're still doing VCE, I'm going to keep picking on the way you've written it :P
Your second sentence is unnecessary - you're not given any information to indicate that the myxamotisis virus existed prior to being introduced in the 1950's (it didn't exist in Aus) so "increased exposure" is technically incorrect, there's also no need to go into that much detail - all you need for that first mark is to identify that the virus is a selective agent. I would probably mention the fatality of the virus somewhere when talking about reproductive success (something about the majority of non-resistant rabbits dying and therefore not reproducing, meaning future generations were predominantly made up of offspring of resistant rabbits) because it makes your answer a bit more specific to the scenario (at the moment it's a bit clunky to read), but that's not really necessary.

5a-b

a) Species 2
b) Species 1 shows a 100% in sequence similarity with humans, thus it is likely in fact human. Since chimpanzees are the closest living relative to humans, they would likely possess a B-globin sequence of the next closest similarity, which is shown in the above table to be species 2.
 
c) this difference in variability is due to the redundancy of the genetic code. Since each amino acid can be coded for by multiple DNA triplet codes, some changes, or variation, in the DNA sequence for the B globin gene may not always result in changes, or variation, in the amino acid sequence.
Spoiler
I had the same thought when I first saw this question, but species 1 is not human. Haemoglobin is a pretty important blood protein, and as such it would be pretty highly conserved and it wouldn't be unreasonable for it to be the same in a similar species - any individuals with deleterious mutations would probably die before reproductive age.


5c-d

c) the first base of the 6th codon of HBA has changed from a G to an A
d) this point substitution would cause the 7th codon to become a 'stop' codon. This would cause the synthesis of a truncated B globin mutant of only 6 amino acids long, and as such the HBA mutant would likely not carry out its function.
Spoiler
The part I've put a line through above isn't necessary - the question only asks about the effect on synthesis of the protein.

6a-c

b) the first base of the DNA triplet complimentary to the 4th mRNA codon shown above would have changed from G to T.
Spoiler
Would have changed to A not T.


6d-e

e) (wasn’t too sure about my explanation for this one)
restriction enzymes cut the DNA sequence at specific recognition sequences and different restriction enzymes have different unique recognition sequences.
Restriction enzymes can cut the DNA to produce restriction fragments with sticky ends (ends with exposed single stranded DNA) of blunt ends.
Spoiler
They're correct :)

8

Corn plants from each farm were obtained and separately planted in two identical pots and were left under the same conditions (e.g same temperature, same light exposure, same soil) with their each of their mature highest being recorded. This was replicated using corn from each farm multiple times under the same conditions and their final hights recorded. If the height of the corn was under genetic control, then the results would show that in the same conditions, the corn from one farm consistently grew taller than the corn from the other farm.
Spoiler
Should probably specify that if it were genetic then the plants from the shorter plant farm would be shorter and vice versa (rather than just saying that one would be shorter than the other) - if it was the other way around than on the farms then you'd have a problem with your experiment.
10

(this response aint too great either)
20,000 - 15,000 years ago when Pedra Branca Rock was connected to mainland Tasmania, an ancestral skink population common to both places would have existed. When rising sea levels separated Pedra Branca Rock from mainland tasmania, the ancestral skink population would have been separated into two distinct genetically isolated populations between which, no gene flow could occur. As a result of the accumulation of differences due to random mutation and the action of different selective pressures, the skink population on Pedra Branca Rock would have diverged from the mainland skink species. Over time this divergent evolution would have given way to the unique Niveoscincus Palfreymani species of skink once they had become reproductively isolated from other mainland skink species.
Spoiler
It's probably a bit longer than needed, but it's not too bad - these sorts of questions are always a bit weird to answer because you have to include all the right terms. You'd need at least three sentences to answer this, and you've done it in 4 so it could be shortened slightly, but that always runs the risk of skipping a key term. There's 3 points here, but you've kinda split your answer into two parts - it would probably be better to make it three distinct steps.
You've included a bit too much description at the start of your answer - it's sufficient to just say that an ancestral population was isolated.
The average mark for this question was 0.8/3 so don't feel too bad haha
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Erutepa

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Re: Challenging biology questions
« Reply #9 on: January 15, 2019, 07:29:40 pm »
+2
Spoiler
Spoiler
Your answer is feasible but it relies on a fair bit of luck (there happening to be igneous rock in the same layers) and is far more complicated than necessary. The question is only worth 1 mark, and note that it asks about the relative age of the fossils - there's a much simpler answer. Also worth considering that potassium-argon dating wasn't used until the early 1900's (although you wouldn't really be expected to know that).

Spoiler
Your answer is totally fine as it is, but given you're still doing VCE, I'm going to keep picking on the way you've written it :P
Your second sentence is unnecessary - you're not given any information to indicate that the myxamotisis virus existed prior to being introduced in the 1950's (it didn't exist in Aus) so "increased exposure" is technically incorrect, there's also no need to go into that much detail - all you need for that first mark is to identify that the virus is a selective agent. I would probably mention the fatality of the virus somewhere when talking about reproductive success (something about the majority of non-resistant rabbits dying and therefore not reproducing, meaning future generations were predominantly made up of offspring of resistant rabbits) because it makes your answer a bit more specific to the scenario (at the moment it's a bit clunky to read), but that's not really necessary.
Spoiler
I had the same thought when I first saw this question, but species 1 is not human. Haemoglobin is a pretty important blood protein, and as such it would be pretty highly conserved and it wouldn't be unreasonable for it to be the same in a similar species - any individuals with deleterious mutations would probably die before reproductive age.

Spoiler
The part I've put a line through above isn't necessary - the question only asks about the effect on synthesis of the protein.
Spoiler
Would have changed to A not T.
Spoiler
They're correct :)
Spoiler
Should probably specify that if it were genetic then the plants from the shorter plant farm would be shorter and vice versa (rather than just saying that one would be shorter than the other) - if it was the other way around than on the farms then you'd have a problem with your experiment.
Spoiler
It's probably a bit longer than needed, but it's not too bad - these sorts of questions are always a bit weird to answer because you have to include all the right terms. You'd need at least three sentences to answer this, and you've done it in 4 so it could be shortened slightly, but that always runs the risk of skipping a key term. There's 3 points here, but you've kinda split your answer into two parts - it would probably be better to make it three distinct steps.
You've included a bit too much description at the start of your answer - it's sufficient to just say that an ancestral population was isolated.
The average mark for this question was 0.8/3 so don't feel too bad haha
Thanks again for the feedback - I really do aprecciate the fantastic feedback. Even though I am 'done' with biology I evidently have much to improve  ;D

Just as last time, I have edited my resonses after reading you feedback, so hopefully there just a bit closer to being good.
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PhoenixxFire

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Re: Challenging biology questions
« Reply #10 on: January 22, 2019, 12:09:35 am »
+6
Week 2 answers
1. D
2. B

3. Stratigraphy, the relative depth of the fossil in the limestone layers or position relative to other layers, older fossils are
generally deeper or knowing the age of the limestone in which the fossil is found or indicator/index fossils.

4. • a small number of resistant rabbits existed before the
introduction of the myxoma virus
• relatively more resistant rabbits survive to pass on myxoma
resistance alleles to next generation
• over several generations the frequency of resistant rabbits
increases.

5. ai. 1
aii. Human and chimpanzee share a recent common ancestor or are
the most closely related; therefore you expect a closer similarity
in DNA and amino acid sequences.
b. Because several amino acids can have more then one codon (or
the genetic code is degenerate/redundant) there can be differences
in the DNA sequence for the same amino acid sequence
c. In HBA globin glu codons GAA or GAG
In HBC globin lys codons AAA or AAG
Therefore the change has been G to A or guanine to adenine.
d. glu GAA – UAA which is a stop codon
The translation of the mRNA would stop after amino acid 6 or the
polypeptide is shortened.

6.
a. The presence of uracil in place of thymine indicates that it is mRNA and not DNA.
b. Guanine to Adenine or G to A or Guanine (G) replaced by Adenine (A).
c. The amino acid arginine is replaced by the amino acid cysteine in the amino acid sequence.
di. Transcription
dii. DNA double helix unwinds, one strand acts as a template for mRNA production or a single strand of DNA acts as a
template
and
bases are added to the growing RNA strand which are complementary to the DNA
and
RNA polymerase recognises the promoter region and binds to the DNA or RNA polymerase recognises a termination
sequence and transcription finishes and the mRNA moves to the cytoplasm.
e. Any two of:
• have recognition sequences specific to the enzyme
• produce sticky or blunt ends when they cut DNA
• were originally extracted from bacteria
• are named after the bacterium from which they were extracted.

7
The male is not the father. Of the two fragments in the gel for the
child, the mother contributed the large fragment (or fragment
closest to loading wells) and the father does not have the smaller
fragment seen in the child (or fragment furthest from loading
wells) therefore is not the father.

8
Two possible answers were:
• Take samples of seeds from the plants on both farms and
grow them in a controlled environment. If the trait is genetic
the phenotypes should be tall from the seeds of the plants on
the property where the plants were tall and shorter from the
property where the plants were shorter.
• Take the seeds from each property and grow them on the
other property. If the trait is genetic the phenotype of the tall
plant should be tall on the property where the shorter plants
grew and vice versa.

9
Two of:
• unsuitable habitat for the plant species
• not in that region pre 228 mya (not correct to say not found
before 228 mya because it was found in other areas)
• unsuitable climate in the region for fossilisation of the pollen
• not found yet during sampling.

10.
• an ancestral species of Niveoscincus palfreymani became
isolated or a species which had continuous distribution
between Tasmania and Pedra Branca Rock (PBR) became
isolated on PBR when sea levels rose
• as a result of no interbreeding (or no gene flow) between PBR
and Tasmania
• genetic differences accumulate over time (with different
selective pressures) and the new species results, i.e.
Niveoscincus palfreymani.

Week 3 questions
MCQ
1

prompt
Cross out the answers you know are incorrect, and pick the best of the remaining options.

2

prompt
Make sure you go through all the possible answers.

3

prompt
The limiting factor remains constant throughout the experiment, an increase in it will increase the reaction rate.

SAQ
4

prompt
This questions requires a bit of logic and not much biological knowledge.

5

prompt
Consider what water sources would be available in a dry environment and ways of retaining water.

6

prompt
Part B isn't really relevant to the study design anymore (it's 1/2 content now) but I've included it anyway as it's a good example of an experiment question.

7

prompt
Make sure you name the structure, not just a component of the structure.

8

prompt
Consider what the parasite might be unable to do if it weren't in a cyst.

9

prompt
This question is asking about how the presence of receptors on different cells can affect the cellular response.

10a-c

prompt
You don't need to be specific in your answers here.

10d-e

prompt
Remember that inflammation is an innate process.
Consider how an immune response could stop an allergen from causing a reaction.
2019: B. Environment and Sustainability/B. Science @ ANU
2020: Just Vibing
2021: B. Paramedicine/B. Nursing @ ACU Canberra

Erutepa

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Re: Challenging biology questions
« Reply #11 on: January 27, 2019, 10:56:20 am »
+2
Week 3 questions
MCQ
1

D - chloroplasts contain layers of intern membranes.

2

A - celulose composed of glucose

3

C - the amount of enzyme

Just did the MCQ because I don't have my computer and really don't wanna write out a bunch of short answer questions on my phone.  :)
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Erutepa

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Re: Challenging biology questions
« Reply #12 on: January 20, 2020, 10:33:00 am »
+2
The science games have begun

As such, it is time for a freshly baked batch of challenging questions!
If you want to score points for the science games, you can do so by answering questions in (and after) this post here. Feel free to answer the question before this, however you won’t earn science games points (but you will still get fantastic revision/learning out of it)
These challenging questions are past VCAA exam questions on which 50% of the state didn’t get full marks (for multiple choice questions) or for which the average mark is less than half of the full available marks (for short answer questions). Please note that while these questions are from VCE study designs, since there is significant overlap between science across the different states, most of these questions should be able to be answered by those from other states.
This thread will be updated weekly with a new batch of 5 Multiple Choice questions and 10 Marks worth of Short Answer questions.
Here is your first batch:
multiple choice
Question 1

The biochemical pathway of glycolysis involves nine intermediate reaction steps. One of these steps is represented in the diagram below.


It is correct to state that, in this reaction, phosphofructokinase
A.   acts as a coenzyme.
B.   increases the rate of reaction.
C.   is the substrate for the reaction.
D.   releases energy in the form of ADP.
Question 2
Hydrogen peroxide is a toxic by-product of many biochemical reactions. Cells break down hydrogen peroxide into water and oxygen gas with the help of the intracellular enzyme catalase. The optimum pH of catalase is 7.
A Biology student measured the activity of catalase by recording the volume of oxygen gas produced from the decomposition of hydrogen peroxide when a catalase suspension was added to it. The catalase suspension was made from ground, raw potato mixed with distilled water. The student performed two tests and graphed the results.


Test 1 used 5 mL of 3% hydrogen peroxide solution and 0.5 mL of catalase suspension, and was conducted at 20 °C in a buffer solution of pH 7.
Test 2 was carried out under identical conditions to Test 1, except for one factor that the student changed.

An explanation for the results of Test 2 would be that the student
A.   increased the concentration of catalase by adding less water to the ground potato.
B.   increased the temperature by placing the test tube in a water bath set at 30 °C.
C.   used a hydrogen peroxide solution with a higher concentration.
D.   added a catalase suspension made from a cooked potato chip.

 
Question 3

An animal cell culture was exposed to radioactively labelled oxygen. The cells were then monitored for three minutes. After this time, the radioactively labelled oxygen atoms would be present in which cellular chemical?
A.   adenosine triphosphate
B.   carbon dioxide
C.   glucose
D.   Water
 
Question 4

Mass extinctions
A.   kill all but the most primitive species.
B.   are caused by the introduction of competing species.
C.   are followed by a period of rapid divergent evolution.
D.   have been caused by continental drift and earthquakes.
 
Question 5

The emergence of antibiotic-resistant diseases in humans means that
A.   antibiotics are causing resistance mutations in bacteria.
B.   some bacteria are less sensitive to antibiotics.
C.   viruses are becoming resistant to antibiotics.
D.   humans are less sensitive to antibiotics.
 
Short Answer
Question 1

Consider the diagram of a plasma membrane below.

There is a higher concentration of a small hydrophobic molecule in the extracellular environment than in the intracellular environment.        

a)   Draw one arrow on the diagram above to show the pathway taken by the small hydrophobic molecule across the plasma membrane. (1 mark)
b)   Justify the pathway you have drawn. (2 marks)

Question 2

Explain how the expression of a single gene can lead to the production of different proteins (3 marks)
Question 3

Although plants have no immune systems, they do have many chemical and physical methods of defence against pathogens and attacks by insects.
White clover (Trifolium repens) reproduces asexually from a runner that grows along the soil surface. The connected new plants are called ramets. The white clover plant in the diagram below is producing ramets in the direction left to right. The fully grown ramets are numbered 1 to 7, from the youngest ramet to the oldest ramet.
 

Scientists hypothesised that when T. repens ramets are damaged by caterpillars of Spodoptera exigua, the damaged ramets stimulate other ramets to defend themselves against attack by the caterpillars. The scientists conducted an experiment to test their hypothesis. The experiment used two genetically identical runners, A and B. The method is outlined in the flow chart below.

What was the role of the Runner A ramets? (1 mark)

The experiment was repeated 40 times. The average results obtained after Stage 2 are shown in the graph below.


After the experiments, the contents of the leaves were analysed. Significantly higher quantities of phenolic acid were found in the young ramets from Runner B. Phenolic acid acts as a signalling molecule.
It was noticed that the caterpillars preferred to eat the mature leaves in Runner B.

Suggest an effect of the signalling molecule on the cells of the young leaves that would account for the caterpillars’ preference for eating the mature leaves in Runner B (1 mark)

question 4
Rational drug design was used by scientists to develop the drug Relenza.
What is meant by the term ‘rational drug design’? (2 marks)

When Answering your questions, please write your answer inside of a spoiler like this:
question 1
Spoiler
This is my answer
The reason behind this is just so that other users who are having a go at answering these questions don’t accidentally see what others have put down and can have a go at it themselves.
I would also like to encourage everyone to have a go at answering these questions without looking at other user’s responses – this will help develop your ability to really critically think about a question independently. Remember, there is no harm in getting something wrong and making a mistake is an opportunity to learn!
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Chocolatemilkshake

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Re: Challenging biology questions
« Reply #13 on: January 21, 2020, 07:12:48 am »
+5
Thanks so much for putting this together Erutepa and helping run the science games  ;D ;D (I do kinda miss these bio questions)

Multiple choice
Question one
Answer 1
B = because the 'ase' ending of phasephofructokinase indicates that it is an enzyme. An enzyme is a protein that acts as a catalyst to speed up a reaction. In this reaction, ATP acts as a coenzyme (which is converted into ADP as the reaction uses energy). The substrate is fructose 6-phosphate.
Question two
Answer 2
C = as using a hydrogen peroxide solution with a higher concentration means that there is more substrate available (increasing substrate concentration), which means the maximum amount of oxygen produced from the reaction is higher. 
Question three
Answer 3
D = This is because oxygen is a reactant in the electron transport stage of cellular respiration. This oxygen bonds to hydrogen molecules carried by coenzymes to form water. It would not be glucose (because animals do not produce glucose) or ATP (only one phosphate is removed to form ADP). CO2 is released as a product in earlier stages of cellular respiration before oxygen in required.
Question four
Answer 4
C = a mass extinction leaves many ecological niches open, allowing species to rapidly diverge to fill such niches without competition.
Question five
Answer 5
B = Antibiotics do not cause mutations in bacteria (common misconception), they simply act as a selecting agent, so over time, bacteria that have resistance to the antibiotics are more likely to survive, reproduce and pass their alleles for their resistance onto their offspring. Hence, the answer is that some bacteria are less sensitive to antibiotics. Antibiotics are not used to kill viruses.

Short Answer
Question one
Answer 1
a) The arrow would be drawn going into the intracellular environment, directly through the phospholipid bilayer and NOT through a protein.
b) This is because the small hydrophobic molecules will travel via simple diffusion down the concentration gradient (from where there is a higher concentration of molecules in the extracellular environment towards where there is a lower concentration of molecules in the intracellular environment). Because the molecules are hydrophobic and small, they are not repelled by the phospholipids and thus can travel directly through the bilayer.
Question two
Answer 2
- Alternative splicing: occurs during RNA processing where enzymes differentially joins exons. This means mRNA strands transcribed from the same gene can have different nucleotide sequences, leading to the production of different mRNA molecules (from the same gene), that are translated to produce different proteins.
- Alternative folding: the presence of different enzymes in different cells may fold a polypeptide (with the same primary structure) into a protein with a different tertiary structure, leading to a different protein (with different functions).
Question three
Answer 3
a) The runner A ramets are used as the control group, demonstrating the amount of leaf eaten by the caterpillars when previous ramets have not been attacked (thus demonstrating the effect of the independent variable). It can be used in comparison to the experimental group where the previous ramets have been attacked by caterpillars.
b) The signalling molecule may cause the young leaves in runner B to produce phenolic acid that deters caterpillars from eating them (such as toxins that give the leaves a bitter taste) thus making the caterpillars more likely to consume mature leaves.
Question four
Answer 4
- Rational drug design is when scientists study the specific shape and action of molecules present in a pathogen that is unique to that pathogen and imperative to the life cycle of that pathogen.
- They then artificially produce a drug, complementary in shape and charge, to the specific molecule, inhibiting its function in the pathogen to give rise to therapeutic benefit.
2021-2025: BMedSci/M.D @ Monash

caffinatedloz

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Re: Challenging biology questions
« Reply #14 on: January 27, 2020, 12:47:55 pm »
0
Multiple Choice
Question 1
B: (as the ending indicates it is an enzyme which would work to speed up a reaction

Question 2
Honestly not sure with this one. I think that it couldn't be A because although the enzyme speeds up the reaction, cooking it would not increase the amount of the enzyme present. Could possibly be B, as temperature could act as a catalyst. It doesn't seem to be C because catalase would work best at its optimum pH of 7 and that it doesn't seem to be D because whether or not the potato was cooked was not part of the list of factors that the student kept the same/changed in the second experiment. Scratch that, it's C as that would affect the pH but would provide more substance to be converted into oxygen. That took me longer than it should have.

Question 3
D. It would be present in water as cellular respiration would have taken place meaning that the oxygen would be converted into CO2 and H2O, however the CO2 would be expelled as the animal breathed out.

Question 4
D. Self explanatory.

Question 5
B. Humans do not become less susceptible to antibiotics, nor do viruses. Antibiotics act on bacteria and due to their overuse, resistant bacteria have been allowed to survive and reproduce and cannot be effectively treated.

Short Answer
Question 1
a)I would draw my arrow straight down the page, directly through the membrane.
b) As there is a higher concentration of molecules outside of the cell diffusion would lead them to diffuse into the cell along their concentration gradient until equilibrium is established. The molecules are small and hydrophobic, meaning that they are attracted to fats and so could cross quite easily across the membrane directly through the fatty acid tails of the phospholipids without needing to travel through a protein channel.

« Last Edit: January 27, 2020, 04:12:46 pm by laura_ »