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Bio exam thoughts (1 Viewer)

pikachu975

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Mathew587

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Noor333

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the exam was easier than what I expected!! I am happy :)
 

r3

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oops there goes my 2 marks..... jesus im getting 50% at this rate. I didnt know xylems were hexagonal :'(
whaaaat did you have to draw it hexagonally

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aycaramba

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whaaaat did you have to draw it hexagonally

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idk man i just drew a circle that was bigger than the phloem and labelled the outer layer a lignified cell wall???/
 

anton93

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For xylem I just drew a circle kinda thing with lignin thickening and for phloem I drew a sieve tube, perforated sieve plate, and a companion cell. Not sure what they're expecting since you can find so many different images for the transverse section of xylem and phloem online. Also about the hexagonal thing, I doubt that would be something marks will be taken off/awarded for, there are microscope images of xylem with a kind of round structure. I'm guessing the main thing is to note that xylem is thickened by lignin while phloem aren't and that phloem are living, xylem are dead at maturity.

For the question about marine fish and freshwater fish I had a similar question in my trial where I got full marks for writing (summarised)
- freshwater fish excrete dilute urine (have large glomeruli to filter large fluid volume)
- freshwater fish excrete nitrogenous waste in the form of ammonia (majority lost via gills due to close proximity with water, some ammonia is excreted in urine, salt concentration of urine is low due to active reabsorption)
- marine fish excrete conc urine to conserve water (nitrog waste excreted as urea, higher conc of salts in urine due to active secretion)

But in the HSC I basically just wrote the dilute urine vs concentrated urine thing and explained using some structures (ie large vs small glomeruli corresponds to volume of fluid filtered, and loop of Henle is long in marine fish counter-current multiplier system to increase reabsorption of water which makes urine very concentrated) but didn't mention ammonia vs urea. Could I still get 4 marks?
 

r3

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idk man i just drew a circle that was bigger than the phloem and labelled the outer layer a lignified cell wall???/
same i dont think you need to draw it hexagonally. its 2 marks lol

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jjHasm

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same i dont think you need to draw it hexagonally. its 2 marks lol

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pretty sure one labled feature was enough on each
 

jjHasm

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My structure for the beadle and tatum (which im assuming will give me a 6-8/8 when i planned it): One gene-one protein --> one gene-one polypeptide --> understanding of DNA nowadays coding for favourable characteristics --> understanding of transgeneic species (definition and example/explanation) and favourable characteristic via picking specific polypeptide to code for desired characteristic, and isolating that gene etc --> little sum up of the whole flow chart, saying that if it werent for B&T, transgenic species wouldnt be possible and all this tech stuff wouldnt happen --> value of judgement since it was an assess q.
 

asfdfasdf

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How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
 

anton93

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My structure for the beadle and tatum (which im assuming will give me a 6-8/8 when i planned it): One gene-one protein --> one gene-one polypeptide --> understanding of DNA nowadays coding for favourable characteristics --> understanding of transgeneic species (definition and example/explanation) and favourable characteristic via picking specific polypeptide to code for desired characteristic, and isolating that gene etc --> little sum up of the whole flow chart, saying that if it werent for B&T, transgenic species wouldnt be possible and all this tech stuff wouldnt happen --> value of judgement since it was an assess q.
My approach for the Beadle and Tatum was that their experiment showed that the production of a particular polypeptide could be linked to a particular gene and that advancements in technology such as DNA sequencing, and Chromosome mapping allowed scientists to identify the gene/s responsible for producing a certain protein and extract these and use restriction enzymes etc to incorporate them within the genome of another species. So the key in their experiment (and why it was important in development of transgenic species) was that they revealed that particular products could be linked to one or a number of genes. Felt like I could've talked about some other discoveries such as discovering structure of DNA and noting that all organisms have same basic structure so genes could be transferred across species.
 

aycaramba

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How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
i just talked about the different stages of action potential like the resting membrane potential where the na+/k+ pump kept the membrane potential at -70mV (referring to the graph ofc), the depolarisation due to influx of na+ into axon through the na+ ion channel which rapidly increases when threshold has been reached etc etc. Dunno if it's enough for a 3 marker tho

BTW guys for multis, what did rosalind franklin discover? i was switching between the double helix structure and other the phosphate one and ended up picking the phosphate option
 

sourish

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This is more or less what i wrote:

Beadle and Tatum experimented with Neurosporra crassa (bread mould). They caused mutations to occur in the bread mould by using x-rays. This mutation resulted in the gene to be unable to code for the production of an enzyme that catalyses the production of a specific amino acid. This amino acid allowed the bread mould to grow, without it it would be unable to do so. From this they subsequently proposed the "one gene-one protein" hypothesis (they assumed that an enzyme was a protein and that one protein consisted of one polypeptide chain). It was later understood that proteins are made of more than one polypeptide hence their theory was modified to become the 'one gene-one polypeptide' theory. This allowed for the development of BT (Bacillus thuringiene) cotton. BT cotton is a trangenic species (a organism that contains the genes of another species and is able to pass this gene to its offspring) that is produced by isolating and cutting the BT gene from bacteria using a restriction enzyme. Then inserting it into cotton plant embryos via a vector. This embryo is then germinated and grown under tissue culture, producing the transgenic species. BT is a gene that results in the production of a enzyme that catalyses the development of a natural pesticide. This pesticide causes pest that come close to the plant to die. BT cotton has been beneficial as it saves money for farmers and reduces the harmful impacts of un-natural pesticides on the environment. Hence Beadle and Tatum's work has been imperative in the development of BT cotton through the theory that one gene codes for the production of one polypeptide.
 

pikachu975

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you reckon this will be fine?

https://dc.edu.au/wp-content/uploads/transverse-of-arterial-blood-gas-analysis.png

i pretty much drew this but zoomed out like that one hsc q where they had a diagram with the pith in the middle and xylem and phloem if you remember?
idk man i just drew a circle that was bigger than the phloem and labelled the outer layer a lignified cell wall???/
Most of my class just drew a circle for xylem separated by cambium and a smaller circle for phloem to contrast differences in size

My structure for the beadle and tatum (which im assuming will give me a 6-8/8 when i planned it): One gene-one protein --> one gene-one polypeptide --> understanding of DNA nowadays coding for favourable characteristics --> understanding of transgeneic species (definition and example/explanation) and favourable characteristic via picking specific polypeptide to code for desired characteristic, and isolating that gene etc --> little sum up of the whole flow chart, saying that if it werent for B&T, transgenic species wouldnt be possible and all this tech stuff wouldnt happen --> value of judgement since it was an assess q.
We had this question in our trial u needed a detailed explanation of Beadle and Tatum's experiment, their results i.e. hypotheses, how one gene codes for one polypeptide relates to phenotype, transgenic species, and how one gene is extracted to transfer into the species relates to Beadle and Tatum's work.

How did you guys respond to question in communication of "explain the electrochemical changes in membrane due to signal 2?" It was a 3 marker and Idk if I answered it right
Basically wrote action potential referring to resting membrane potential of -90 mV approx and sodium/potassium etc.

For xylem I just drew a circle kinda thing with lignin thickening and for phloem I drew a sieve tube, perforated sieve plate, and a companion cell. Not sure what they're expecting since you can find so many different images for the transverse section of xylem and phloem online. Also about the hexagonal thing, I doubt that would be something marks will be taken off/awarded for, there are microscope images of xylem with a kind of round structure. I'm guessing the main thing is to note that xylem is thickened by lignin while phloem aren't and that phloem are living, xylem are dead at maturity.

For the question about marine fish and freshwater fish I had a similar question in my trial where I got full marks for writing (summarised)
- freshwater fish excrete dilute urine (have large glomeruli to filter large fluid volume)
- freshwater fish excrete nitrogenous waste in the form of ammonia (majority lost via gills due to close proximity with water, some ammonia is excreted in urine, salt concentration of urine is low due to active reabsorption)
- marine fish excrete conc urine to conserve water (nitrog waste excreted as urea, higher conc of salts in urine due to active secretion)

But in the HSC I basically just wrote the dilute urine vs concentrated urine thing and explained using some structures (ie large vs small glomeruli corresponds to volume of fluid filtered, and loop of Henle is long in marine fish counter-current multiplier system to increase reabsorption of water which makes urine very concentrated) but didn't mention ammonia vs urea. Could I still get 4 marks?
Woah I doubt you need all the stuff about glomeruli etc. I think simply contrasing their urine, what each fish loses to their environment, what goes into their body and why, etc should be enough.

i just talked about the different stages of action potential like the resting membrane potential where the na+/k+ pump kept the membrane potential at -70mV (referring to the graph ofc), the depolarisation due to influx of na+ into axon through the na+ ion channel which rapidly increases when threshold has been reached etc etc. Dunno if it's enough for a 3 marker tho

BTW guys for multis, what did rosalind franklin discover? i was switching between the double helix structure and other the phosphate one and ended up picking the phosphate option
Double helix
 

sourish

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pikachu975 how was my response, what do you think it'll get out of 8?
 

pikachu975

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pikachu975 how was my response, what do you think it'll get out of 8?
Depends on the marking criteria but in my trial I lost a mark for including not much detail for their experiment so you might lose one mark, and not sure if the link to one gene one polypeptide and how it relates to transgenics is enough so possibly 6-7
 

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