VCE Biology Questions Thread

tubes

md2112 The explanation is that H. floresiensis had a much small stature and couldn't be the ancestor of the otherwise taller Indigenous Australians. H. densiova can't be because they share only a small percentage of DNA, and if it was the ancestor it would show much greater genetic similarity, thus the small percentage of DNA similarity would be because of interbreeding rather than descent. For example, Neanderthals and modern H.sapiens share max 5-7 percent (smth like that) DNA in common, but we say they shared a common ancestor and interbred rather than Neanderthals being the ancestor of H.sapeins, the same logic applies here.

md2112

tubes so it is homo erectus, also how do we know that h.floresiensis has a small stature

Christ

tubes
Yeah I see where your coming from.
I hope they don't have a question like that on the exam.

tubes

md2112 this was from prior knowledge, And I really do understand your point about this text lacking information, but perhaps the fact that they were found in Indonesia????? Its a bit of a stretch, but I have heard sample exams for VCE indicate the type of questions we'll be given and not necessarily the actual content, like from this article we can perhaps expect a "similar case study" were we have to explain concepts but in the context of the article

md2112

tubes thanks for the help, also for the last question 10d what was ur answer, with the marking in consideration

tubes

md2112 Straight off the bat you had to recognise that anaerobic fermentation was producing the Co2
So i think (note he word think), the mark allocation would be:

Recognition that the wheat seeds were anaerobically fermenting because of low oxygen conditions preventing aerobic respiration
The process is faster than aerobic respiration and thus would show a consistently high level of CO2 production (this is what my teacher advised)
This process produces CO2
However after a period of time a decrease inn CO2 levels is observed as the accumulation of ethanol as a by product would accumulate and may be toxic OR because of the inefficiency of anaerobic fermentation (produces less ATP per glucose molecule) the glucose storages of the seed would run out

Again this is not a definitive guide but close enough

md2112

ok thanks do we need to know about the dates when the new homminn species diverged

atarwonders

hi i need help with 4 a. sample exam

Christ

atarwonders
So with question 4a,
As the Indigenous population and the British population had never come in contact, Aboriginal's did not have the adaptive immunity in terms of B memory cells against the pathogens carried by the British, including smallpox, which resulted in deadly infection in the Aboriginals.
I believe to get the third mark you have to mention how British people had active immunity against smallpox and hence able to fight off infection and so the severity of infection was not as bad as in the aboriginal population

Pasta

md2112 It is Denisovans. There is 4-6% similarity in the nuclear DNA shared amongst Indigenous Australians, Papua New Guineans and Indonesians and this covers the likely route to Australia (as seen in the article). Homo erectus and Home floresiensis were in the areas near Sahul at the time of the migration to Australia but none of their nuclear DNA is shared with indigenous Australians.
(It’s not H. erectus because the article states clearly that no other species apart from Denisovans shared nuclear DNA with Indigenius Australians).

md2112

Pasta and so why isn't it floresis

chemistry1111

for question 6 multiple choice of the vcaa 2019 exam,
why is the answer D and not B. Thank you

_sophiestudies_

chemistry1111 it cannot be B because the question has stated that aldicarb is a reversible inhibitor of acetylcholinesterase. This means it will form weak intermolecular bonds with the the enzyme (not strong covalent bonds like irreversible inhibitors), allowing it to detach from the active site (reversible = non-permanent). B says it strongly binds to the active site of acetylcholinesterase, which is therefore incorrect. A is also incorrect because the question already states that it is reversible, not permanent/irreversible. C is incorrect because inhibitors prevent the substrate from being catalysed by the enzyme, meaning the rate of the breakdown of acetylcholine cannot increase. D is correct because it will reduce the activity of acetylcholinesterase, binding to its active site and "reducing the number of active sites for acetylcholine to bind to". Hope that helps!

Smartiestarz

md2112 It’s not H floresiensis because they tend to have smaller stature so compared to Aboriginal Australians who are much larger, they couldn’t be the ancestor - you can also probably talk in terms of cranial capacity and how it was found much more recently than 50000/60000 years ago when Aboriginal Australians first arrived into Sahul. The only confusion comes with H Denisova and H erectus
Because it says “fossils from this time period include H erectus” I’d argue that H erectus lived in the same time period as the aboriginal Australians so its not likely to be an ancestor (also considering the lack of similarity of nuclear DNA)
I feel like although H denisova only shares 4-6% nuclear DNA in common its probably the best answer here accoridng to the information given in the passage

studyingvce2022

do i need to know the specific amounts of products/inputs for cellular respiration and photosynthesis?

md2112

studyingvce2022 no you just need to know the specific atp

chemistry1111

has the master gene been removed from course

md2112

Smartiestarz ok, also how do cytotoxic t cells get activated by t helper cell

md2112

what are two differences between cytotoxic t cells and natural killer cells

Smartiestarz

md2112

Cytotoxic T cells are involved in an adaptive immune response (cell mediated) and they release chemicals like perforins to induce apoptosis in virally infected cells upon binding to the non self antigen presented on MHC 1 markers of the infected host cell
Whereas natural killer cells are involved in the innate immune response. It detects the lack of MHC 1 markers on a host cell and recognises it as “non self” releasing granzymes initiating a death ligand that causes apoptosis

_sophiestudies_

md2112 cytotoxic t cells are part of the adaptive cell-mediated response, whereas natural-killer cells are non-specific immune cells part of the innate immune system (second line of defence). Cytotoxic t cells will therefore specifically bind to MHC I markers/antigens it's initial T cell was selected for, whereas natural killer cells will target any foreign MHC I markers it notices on viral infected cells or tumour cells. Also, natural killer cells have killer activation and killer inhibition receptors that indicate whether it kills the cell, whereas cytotoxic t cells are already programmed to kill the cell that they bind to using their t cell receptor.

md2112

Smartiestarz ok thanks, also do u know how do cytotoxic t cells get activated by t helper cell

« Previous Page Next Page »