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October 21, 2019, 12:48:01 am

Author Topic: VCE Biology Question Thread  (Read 1384957 times)  Share 

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Apricot

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Re: VCE Biology Question Thread
« Reply #9345 on: October 02, 2017, 03:01:01 pm »
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Great questions! (I would try and provide an educated guess to most of them but think its better if someone who is certain answers them!)

For question 2, I think this refers to the suspected interbreeding between the two groups. 'New alleles' would have been introduced into the gene pool. By this I mean alleles that weren't present in that particular population may have entered when they interbred. This then means that there are new alleles that can be passed down to future generations and changes the allele frequencies of the population. (Note these alleles have not been 'created' they are simply passed along when interbreeding occurs)

For question 5, repeating an experiment (with all the same controlled variables) will not reduce the effect of a systematic error as a systematic error is a consistent error such as a scale (or measuring cylinder, stopwatch etc.) that is calibrated slightly incorrect. If the same scale was used every time the experiment was repeated (which it should be) then the mistake in mass will be the same regardless of how many times the experiment is repeated.

Sorry I can't be of more help, if there are flaws in my answers please correct me !

For question 5, I confused systematic with random error, so will repetition reduce the effect that random errors in trials have on the results, as well as uncontrolled variables?

But thank you for your help!

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9346 on: October 02, 2017, 03:07:43 pm »
+6
It will reduce the effect of random errors as they only occur in one repetition of the experiment. So they will then be averaged out with other correct results. Repetition will help any uncontrolled variables that are only present in SOME of the repetitions. If uncontrolled variables have the same effect in ALL of the experiments then repetition will not help (as you are just averaging many incorrect results).
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Apricot

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Re: VCE Biology Question Thread
« Reply #9347 on: October 02, 2017, 03:14:16 pm »
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1) Carbon dating can only be used on very new fossils (not 'true' fossils) that still have carbon which is why it is not particularly useful.

2) Gene flow is the movement of alleles between populations. It does not involve new alleles, only mutations can create new alleles. Gene flow between neanderthals and humans is referring to interbreeding, producing offspring that have some human and some neanderthal DNA (which would make them the same species, which they're not so it's a bit confusing - people aren't really sure). This neanderthal DNA is now present in the human population (ie. it is represented in their gene pool and can be passed down through generations. This is what they mean by gene flow - The alleles moved from the neanderthal gene pool to the human gene pool and are now 'available' for the next generation. - Tell me if this doesn't make sense and I'll try and explain it a different way.

3) It would depend on how the question is worded. In VCAA exams I doubt they would just ask you to define it without context. If your context has a nucleus then mention it if they're talking about a bacteria then don't. In bacteria its sort of like the ribosomes find the mRNA not so much the other way around. It can end up being translated whilst it is still attached to the DNA and being transcribed - This is why bacterial DNA doesn't have introns.

4) They don't only recognise them in lymph nodes, they recognise them whenever they happen to bump into them (ie. in the blood or lymph) but most naive B and T cells are in lymph nodes at any point in time. Think about it like a fish swimming around trying to find another particular fish - They could find each other in a river but they are far more likely to find each other in the ocean.

5) It wouldn't help for systematic errors that are present in all replications of the experiment, however it would help against errors that are in one experiment. Eg. If you used a thermometer measuring 5 degrees low in all of one experiment it would be a systematic error but if you repeated the experiment on another day and used a different thermometer that was working then it would only affect one replication of the experiment so its affect would be minimised through repetition, however if you used the same (broken) thermometer for all the experiments then repeating it would not help.
It's the same sort of thing. Repetition only helps reduce the effect of uncontrolled variables if they are not present in all repetitions. Any errors that are present in all cannot be minimised through repetition as you will continue getting the same wrong results, however errors that are not present in all can be minimised as some of your results are accurate.

6) I don't know about this maybe someone else can knows? I need to revise this myself lol.

7) Do you mean like the gene for antibiotic resistance? Or an antibiotic to kill it?
For resistance it would be the same as they introduce any other gene. If they wanted to see which bacteria could survive antibiotics (eg. to see which had successfully gotten the resistance gene) then I guess they'd just dump the antibiotic on top of them? I don't know exactly how but I don't think we need to know that.

Feel free to ask any other questions you come up with or let me know if this doesn't make sense.

For q3, the VCAA question just said "State a type of RNA and it's function" without context, in this case, would not mentioning the nucleus be considered incorrect?
For q4, if a B cell were to recognise it's specific antigen in the blood, could clonal selection and expansion technically occur there, providing a specific T helper cell was present to activate the B cell in the bloodstream?
Q7, as part of the benefits of GMO's section, our textbook stated that "GMO's give us the possibility of introducing antibiotics and vaccines into foods...which can provide disease resistance to the population," it seems like they're talking about the actual antibiotic which seems quite unfeasible?
Also, for scientific method, could you please outline the key distinguishing factor between an error and an uncontrolled variable?

Thank you for your help and lengthy reply!

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9348 on: October 02, 2017, 03:35:02 pm »
+7
q3. For that question I would say mRNA is a copy of a section of genetic code from DNA, it travels to the ribosome where it is translated. If you have access to the examiners report from that exam then have a look there and see what they said. If it was a common error than they will mention it. I don't think they will be that strict on the definition for a question like that, however I would avoid mentioning anything potentially incorrect. In the exam that mentioned the nucleus did you read the examiners comments? Sometimes just because its the sample answer doesn't mean that VCAA won't accept slightly different ones.

q4. A B cell could recognise its antigen anywhere, A T h cell could also recognise its antigen anywhere. They then have to find each other (also could occur anywhere) If they can bind then the T h cell will release cytokines which is what stimulates them to divide and differentiate. Where this occurs does not matter, It's just more likely to happen in lymph nodes as their are more B and Th cells there at any one time. So yes assuming there was an activated B and T h cell both present at the same location in the blood then they would bind, the Th cell would release cytokines and they would divide and differentiate there. Then all of the copies would travel throughout the blood and lymph, continuing to divide.

q7. With vaccines, what they could do was put antigens in food (ie. insert the gene that codes for the antigen protein), then when that food is eaten the bodies immune system will be stimulated. Then if the disease with that antigen infects the population, that population will be immune (think mass vaccination).

I think what they're talking about with antibiotics might be that they can make a population immune to the antibiotic (ie. the antibiotic won't hurt them) then if that population is infected they can be treated with the antibiotic and only the pathogen will be affected? But that doesn't make much sense as antibiotics are only really useful against bacteria. I don't know what they mean by this and I would just forget about it, there are other benefits you can talk about if you need to.

For scientific method an error is something you did wrong ie. accidentally put 2 drops in one tube instead of one, whereas an uncontrolled variable would be something like repeated a photosynthesis experiment at different times of the day (ie. different amounts of light.)
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rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9349 on: October 02, 2017, 04:12:05 pm »
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Me again,

Where are mast cells located? I thought they were found in connective tissue but a (very) old VCAA exam says they are found in blood vessels

Thanks so much !

EDIT: added a question
My bio teacher said we don't need to learn the different plant hormones, but they seem to be everywhere. Should I learn them to be safe?
« Last Edit: October 02, 2017, 09:32:11 pm by rainbowsparkles15 »
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K888

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Re: VCE Biology Question Thread
« Reply #9350 on: October 02, 2017, 04:29:25 pm »
+5
Me again,

Where are mast cells located? I thought they were found in connective tissue but a (very) old VCAA exam says they are found in blood vessels

Thanks so much !
Not sure what the VCAA accepted answer is, but my uni physiology textbook says mast cells are concentrated in connective tissue (particularly that of skin), the lungs, and the gastrointestinal tract. If you think about it - in these areas, they're ideally situated to intercept pathogens (that have been inhaled, ingested or have entered through broken skin).

I guess maybe the reasoning behind that old answer is that mast cells are tissue basophils, and basophils themselves are white blood cells? But yeah, not 100% sure about that.
« Last Edit: October 02, 2017, 04:31:37 pm by K888 »
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Bri MT

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Re: VCE Biology Question Thread
« Reply #9351 on: October 02, 2017, 04:30:45 pm »
+6
For q3, the VCAA question just said "State a type of RNA and it's function" without context, in this case, would not mentioning the nucleus be considered incorrect?
For q4, if a B cell were to recognise it's specific antigen in the blood, could clonal selection and expansion technically occur there, providing a specific T helper cell was present to activate the B cell in the bloodstream?
Q7, as part of the benefits of GMO's section, our textbook stated that "GMO's give us the possibility of introducing antibiotics and vaccines into foods...which can provide disease resistance to the population," it seems like they're talking about the actual antibiotic which seems quite unfeasible?
Also, for scientific method, could you please outline the key distinguishing factor between an error and an uncontrolled variable?

Thank you for your help and lengthy reply!

3. You could just pick tRNA for that which has no controversy around it. But if you had to pick mRNA I wouldn't mention the nucleus directly, instead I would reference "the site of the genetic information" or something. Best to ask your teacher though.
(Phoenixfire's response to this is great)
7. I guess they  could insert an allele coding for a protein which acts as an antibiotic

Also: scientific error is better referred to as uncertainty. Eg . You measure that the temperature is 26 degrees but it could be a degree lower or higher.
An extraneous variable is a variable other than the IV which may impact the DV
An uncontrolled variable is a variable (not the IV or DV) that was not kept constant during the experiment.
You want to control your extraneous variables & reduce their impact.
You want to reduce your uncertainty by using more precise measurements and repetition



In my study design I was taught that mast cells are in blood vessels but I wouldn't trust that answer to be accurate
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ezferns

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Re: VCE Biology Question Thread
« Reply #9352 on: October 03, 2017, 10:33:11 am »
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Quick question: for the exam are we allowed to write outside the lines given?

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Re: VCE Biology Question Thread
« Reply #9353 on: October 03, 2017, 10:34:51 am »
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Quick question: for the exam are we allowed to write outside the lines given?

Yes, as long as you write within the lines around the paper
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Apricot

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Re: VCE Biology Question Thread
« Reply #9354 on: October 03, 2017, 12:55:37 pm »
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In regards to the "types of fossils" point on the study design, what are the types we should know about? Some textbooks divide fossils up into physical, trace and biosignatures while other sources say body, petrified, trace, cast, mould, biosignature etc. so it's a bit confusing about what terms we should use when stating what type of fossil something is. Could someone please clarify?

rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9355 on: October 03, 2017, 01:08:53 pm »
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In regards to the "types of fossils" point on the study design, what are the types we should know about? Some textbooks divide fossils up into physical, trace and biosignatures while other sources say body, petrified, trace, cast, mould, biosignature etc. so it's a bit confusing about what terms we should use when stating what type of fossil something is. Could someone please clarify?

According to the Heinmann textbook, Edrolo and ATAR Notes Complete Course Notes the types of fossils mentioned are the body, petrified, trace, cast, mould, biosignature etc.
I haven't come across the first categories you listed (though of course there's always a possibility they could show up)
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Apricot

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Re: VCE Biology Question Thread
« Reply #9356 on: October 03, 2017, 02:44:34 pm »
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According to the Heinmann textbook, Edrolo and ATAR Notes Complete Course Notes the types of fossils mentioned are the body, petrified, trace, cast, mould, biosignature etc.
I haven't come across the first categories you listed (though of course there's always a possibility they could show up)

Nature of biology uses the first few categories I listed for the types of fossils but it seems quite limited to reduce it to merely 3 categories. Does this mean body fossils are the actual remains of the organism without it having undergone replacement by minerals? For instance, a skull that is exactly as it was when the organism died?

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9357 on: October 03, 2017, 02:59:41 pm »
+5
Some definitions stolen from google that may help:
Physical fossil: Couldn't find a defintion. I think this is just your typical fossil - Mineralised or actual hard parts.

Trace fossil: Trace fossils provide us with indirect evidence of life in the past, such as the footprints, tracks, burrows, borings, and feces left behind by animals, rather than the preserved remains of the body of the actual animal itself. https://en.wikipedia.org/wiki/Trace_fossil

Biosignatures: Chemical fossils are chemicals found in rocks that provide an organic signature for ancient life. Molecular fossils and isotope ratios represent two types of chemical fossils.
Molecular fossils are often referred to as biomarkers or biosignatures and represent products of cellular biosynthesis that are incorporated into sediments and eventually into rock. Many of these chemicals become altered in known ways and can be stable for billions of years. http://petrifiedwoodmuseum.org/ChemicalMolecularFossils.htm




Body fossils: Body fossils are the most common type of fossil found across the world. They are formed from the remains of dead animals and plants. Most body fossils are of hard parts such as teeth, bones, shells, or woody trunks, branches, and stems. Seems to just be your typical fossil. https://www.dkfindout.com/us/dinosaurs-and-prehistoric-life/fossils/body-fossils/

Petrified fossils: I think this is when the entire organism is replaced by minerals not just the hard parts. (think Pompeii)  A petrified fossil is different from other fossils such as resin fossils or permineralized fossils because the original material of the organism is still intact in resin fossils or permineralized fossils. https://sciencing.com/petrified-fossil-10017264.html

Mould fossil: When the original hard parts disappear but the area is not filled with minerals, just leaving a hole in the rock.

Cast fossil: Cast fossils are formed due to a layer of a different type of sediment filling a mould fossil, and then the mould fossil disappearing (eg eroding faster than cast)

So fairly sure they're all 'correct' just different levels of classification. I would just learn about 2 or 3 I doubt they will ask you to describe them all -They may mention a type in a question and expect you to know what it is though.
« Last Edit: October 03, 2017, 03:01:57 pm by PhoenixxFire »
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ezferns

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Re: VCE Biology Question Thread
« Reply #9358 on: October 03, 2017, 06:54:12 pm »
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Hey everyone
What's the difference between social and ethical implications?
And what kind of social and ethical implications exist in gene cloning and DNA profiling?

Thanks in advance!

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Re: VCE Biology Question Thread
« Reply #9359 on: October 03, 2017, 08:26:06 pm »
+2
Social: Effects people. eg. Not all farmers will be able to afford a GM crop
Ethical: Just bad (at least to some people). eg. Humans shouldn't be allowed to interfere with nature - 'playing god'

Not sure what you mean by gene cloning? Like GM organisms or clones of a whole organism?

For DNA profiling

Social:
-If you find out that you have a genetic disorder that means our parent does too.(eg Huntingtons - something you don't find out until later in life)
-Not everyone will be able to afford DNA profiling
-May be charged more for life insurance
-May lose/not get job due to possible inability to work in future

Ethical:
-Should you be allowed to find out if there's no treatment
-When used in embryo selection it alters our gene pool.

There's plenty of others but that's just what I came up with. I'm sure there's some that fit into both as well.
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