HSC Biology Question Thread

[liya1234]

Pen. If you're unsure, do it in pencil first then trace over with pen. this is because the papers are scanned (I think  markers were given physical copies in the past), and pencil wouldn't be able to show well

I thought this as well but I was just going through the 2016 paper and it says on the front page to draw diagrams in pencil so I think it should be okay to leave graphs in pencil

[caitlinlddouglas]

I think just know a brief outline of the epidemiological study by Hill and Doll from the 50's in the UK
so like the case study: by collecting data on the occurrence of the disease to identify the impacts of age, race, geographic specificity
e.g. lung cancer incidence was higher in UK than Japan and try to form a hypothesis for the etiology of the disease (E.g. could be due to increased smoking since WW2 or from increased construction of roads etc)
then they did a case control by determining the frequency of the determinant (smoking) in diseased and non diseased individuals
e.g. they asked 650 lung cancer sufferers and only 2 didn't smoke --> so there is a correlation b/w smoking and lung cancer
but this sample size was too small so they did a cohort study following 40,000 doctors for like 40 years or something where they one group is exposed to the determinant whereas the other isn't (analytical study)

and then Doll found the odds ratio b/w smoking and lung cancer to be like 9.01 and anything above 1 suggests there is a causal relationship

hope this is right lol
not sure if u needa know that much detail

hey thanks! I've just got limited stuff on the Hammond and Horn study in the US - I think they surveyed 1 million people but did a follow up of 180 000 men for mortality to determine the link so hopefully that's enough, imight briefly mention the hill and doll study too.

[Opengangs]

Best of luck to everyone sitting the biology exam tomorrow! Make sure you get enough sleep since the exam starts at 9:25am.
I'll be here to answer any last minute requests for each of the three core + genetics

[tsauceonchips]

Hey there, just wondering do we need to know the mechanisms that allow interaction between B and T lymphocytes?? If so, what are they? :DD

[66295]

Hey there, just wondering do we need to know the mechanisms that allow interaction between B and T lymphocytes?? If so, what are they? :DD

You do. There are three major Mechanisms:
1) MHC molecules: MHC molecules are the glycoprotein molecules on the surface of the cells from the body that allow them to identify them as belonging to the body. These Molecules also are able to identify the foreign cells found in the body.
2) Clonal selection: In short it pretty much talking about immunological memory (Immune system gaining a memory from previous exposures) and how the body will produce two different specific types of lymphocytes - one will remain in body to create a memory b or t cell and the other will fight off the pathogen/foreign cells.
3) Cytokines: these are a group of signalling compounds used for communication between cells.

Hope this helps it was based on my knowledge and off top of my head

Good luck

[66295]

Hii wondering what type of adaptation sunbaking is? e.g. central netted dragon sunbake during the morning to absorb heat which activates their daily body functions.

also during day their skin becomes lighter? what type of adaptation is this too?

Behavioural adaptation for the sun baking and physiological for the changing skin shade

[Daniyahasan]

help!!
a) outline the processes used to prodice a NAMED transgenic species. (3 marks)
b) Describe the environmental issues that arise from the species you describes in part a). (3 marks)

i was gonna do strawberries will the antifreeze gene from salmon but then that wouldnt make sense in part 2 cos it doesnt really arise any environmental issues

[ellybubble]

Hey guys, sorry if this is a stupid Q, but how does bio-geography support the theory of evolution? I'm a bit hazy when I explain it in an answer.
Thanks!

[66295]

help!!
a) outline the processes used to prodice a NAMED transgenic species. (3 marks)
b) Describe the environmental issues that arise from the species you describes in part a). (3 marks)

i was gonna do strawberries will the antifreeze gene from salmon but then that wouldnt make sense in part 2 cos it doesnt really arise any environmental issues

Im not going to address question fully but enough to get marks

BT cotton is an example of a transgenic organism.
Process used:

1.Normal cotton seedlings are cut into small pieces and placed into a solid growth medium, where they grow into calluses. The callus cells are then transferred into a liquid medium where they are given hormones so they can grow into cotton plant embryos.

2.The BT gene is extracted from a bacterium Bacillus thuringiensis, using restriction enzymes

3.The BT gene must then be transferred to the embryos using a vector bacteria. The embryos are dipped in a solution (containing the vector and the extracted BT genes, and the vector bacteria inject the BT genes into the cotton cells

4.Once the gene is inserted, the embryos are grown in tissue culture, then placed in a solid medium and germinated into small plants. These plants are now a transgenic species.

[ellybubble]

help!!
a) outline the processes used to prodice a NAMED transgenic species. (3 marks)
b) Describe the environmental issues that arise from the species you describes in part a). (3 marks)

i was gonna do strawberries will the antifreeze gene from salmon but then that wouldnt make sense in part 2 cos it doesnt really arise any environmental issues

a) maybe the production of BT cotton, using recombinant DNA technology to amplify the gene from BT bacteria, then using agrobacterium as a vector in putting it in the embryo of cotton. (then u can go through the recombinant DNA stuff like plasmid, restriction enzyme etc...)

b) one environmental impact is the creation of monocultures of BT cotton, which would become dominant as opposed to normal cotton due to natural pest resistant properties. and since they would be genetically similar, a selective pressure can easily wipe away the whole population.

hope this is right sorry if its not

[sidzeman]

Where in the kidney does active transport and passive transport take place? I know the obvious such as glomerulus --> bowmans capsule passive, proximal is active. However when sodium and water is reabsorbed by Aldosterone and ADH, is that also active transport or passive? Also, just to double check Aldosterone is released in the ascending loop of henle and ADH in the collecting tube correct?

[ellybubble]

Where in the kidney does active transport and passive transport take place? I know the obvious such as glomerulus --> bowmans capsule passive, proximal is active. However when sodium and water is reabsorbed by Aldosterone and ADH, is that also active transport or passive? Also, just to double check Aldosterone is released in the ascending loop of henle and ADH in the collecting tube correct?

I think passive is like all the water reabsorption (osmosis), and filtration due to the high pressure of blood flow at the bowman's cap/glomuerulus,  but when glucose and amino acids are reabsorbed at the proximal tubule, that is active transport as it moves against the concentration gradient . I think salt is also reabsorbed via active transport.

[angelahchan]

Hey guys, sorry if this is a stupid Q, but how does bio-geography support the theory of evolution? I'm a bit hazy when I explain it in an answer.
Thanks!

Nah it isn't a stupid q.
According to theory of evolution, new species can arise when a group of organisms from the original population is isolated for  a long time. Organisms should be more similar to species that lived close by. You can link this to all flightless birds having a common ancestor from Gondwana. And as a result of the separation of Gondwana and subsequent isolation of groups of the population, there are different species of flightless birds. For example emus in australia, ostriches in south africa, kiwis in new zealand etc.

[bimberfairy]

Where in the kidney does active transport and passive transport take place? I know the obvious such as glomerulus --> bowmans capsule passive, proximal is active. However when sodium and water is reabsorbed by Aldosterone and ADH, is that also active transport or passive? Also, just to double check Aldosterone is released in the ascending loop of henle and ADH in the collecting tube correct?

Pretty sure anywhere that salt is absorbed, that's active transport (goes against concentration gradient), while absorption of water is passive transport. Aldosterone increases the absorption of salt, which is active transport since it goes against the concentration gradient. But as a result of this, water follows due to osmosis (passive transport). As for ADH, it just increases the absorption of water, so passive transport only.

From what I have in my notes, ADH is released in the collecting duct, while aldosterone is released in the distal convoluted tubule? You should wait for someone else's reply too for a second opinion though haha

[angelahchan]

Pretty sure anywhere that salt is absorbed, that's active transport (goes against concentration gradient), while absorption of water is passive transport. Aldosterone increases the absorption of salt, which is active transport since it goes against the concentration gradient. But as a result of this, water follows due to osmosis (passive transport). As for ADH, it just increases the absorption of water, so passive transport only.

From what I have in my notes, ADH is released in the collecting duct, while aldosterone is released in the distal convoluted tubule? You should wait for someone else's reply too for a second opinion though haha

Both aldosterone and ADH act on the distal and collecting tubule. Also adding to this there's  also secretion- urea diffuses in at the proximal tubule, whereas hydrogen ions moves into the distal tubule via active transport