VCE Biology Question Thread

[cosine]

The Hypothesis that Homo sapiens first evolved in Africa and then migrated out replacing other populations they came in contact with.
Evidence
- Greatest mtDNA variation exist in African populations
- Oldest and transitional hominin fossils are only found in Africa

By 'homo sapiens first evolved in Africa and then migrated' does this mean that humans firstly evolved in Africa, and then waves of populations of humans FROM africa moved out to other regions of the world to inhabit different environments?

Also for the evidence, what does greatest mtDNA variation got to do with African populations?

[katiesaliba]

How does a "population bottleneck" contribute to a lack of variation if the numbers subsequently increase?
I don't know how to put this in a 2 mark answer that VCAA will accept

Look over past vcaa exams for an answer they'd accept. Bottlenecks essentially reduce the prevalence of alleles within a population,thus reducing their variation. Remember that this occurs due to a random event.

By 'homo sapiens first evolved in Africa and then migrated' does this mean that humans firstly evolved in Africa, and then waves of populations of humans FROM africa moved out to other regions of the world to inhabit different environments?

Also for the evidence, what does greatest mtDNA variation got to do with African populations?

Yes. Homo erectus migrated out of Africa earlier and evolved into Homo neanderthalis. Those Homo erectus individuals that stayed in Africa eventually evolved into Homo sapiens. I recommend that you watch the documentary 'walking with cavemen' - it's very interesting and relevant to this section of the bio course

Greater mtDNA variance=more time for mutations to accumulate.

[vox nihili]

How does a "population bottleneck" contribute to a lack of variation if the numbers subsequently increase?
I don't know how to put this in a 2 mark answer that VCAA will accept

Just to add to what Katie said, it all comes down to the key to evolution: variation. Bottlenecks reduce population size, this reduces variation, therefore there is less to select for.

I make this point more or less for the benefit of other people reading because I think that a lot of people tend to forget that variation, and by extension population size, is really the driver of evolution. Organisms that can get more varied more quickly (by breeding lots and/or mutating fast) tend to evolve more quickly. Anyway the effect of a bottleneck is to reduce variation by reducing population size, which means that there's less to select for, thereby making it more likely that the population as a whole will be susceptible to changes in environment.

[Biology24123]

Is rational drug design still on the course

[vox nihili]

Is rational drug design still on the course

Yes

[sunshine98]

Want to clarify how neurotransmission occurs ,so this is what I know :
1) Neurotransmitter stored in vesicle
2) During action potential Ca2+ ions come into the cell. Vesicles move to membrane and are exocytosed out of cell and they release content into synaptic cleft
3) It diffuses across synapse and binds to  receptors on the post synaptic membrane
also , why does Ca 2+ move into the neuron?
Thanks 

[Biology24123]

Want to clarify how neurotransmission occurs ,so this is what I know :
1) Neurotransmitter stored in vesicle
2) During action potential Ca2+ ions come into the cell. Vesicles move to membrane and are exocytosed out of cell and they release content into synaptic cleft
3) It diffuses across synapse and binds to  receptors on the post synaptic membrane
also , why does Ca 2+ move into the neuron?
Thanks 

Depolarization causes voltage-dependent calcium channels to open. I think calcium ions bind to the vesicles containing the neurotransmitters 

[Biology24123]

Do we need to know the specifics of blood clotting and fever

[vox nihili]

Depolarization causes voltage-dependent calcium channels to open. I think calcium ions bind to the vesicles containing the neurotransmitters

In essence, yep. Calcium influx makes the vesicles exocytose.

Do we need to know the specifics of blood clotting and fever

Nope.

[cosine]

"Describe the events that occur when non-self transplanted organs are rejected"

The answer only includes the cell-mediated response. I get how T-Helper cells are activated and actually activate Cytotoxic T cells and then these release cytotoxins to destroy the non-self cells, but, how come the production of antibodies is not included? Are the production of antibodies involved when non-self transplanted cells are introduced?

[neverstopexploring19]

Does anyone have advice for revising:
(1) stages of photosynthesis
(2) ALL the evolution stuff

Thanks 

[TheAspiringDoc]

Does anyone have advice for revising:
(1) stages of photosynthesis
(2) ALL the evolution stuff

Thanks 

Try and find how the concepts in one topic tie in and link with all the other topics. So don't just think about photosynthesis, rather also think about it in regards to cellular respiration or chemistry. Look at it from all angles and be inquisitive. Plus I think bangali lok mighta made some biol theory revision questions 
edit: 400th post 

[sushibun]

How much depth do I need to study for plant hormones?
Can someone also explain to me why the answer is B and not C.
Thank-you :)

[sushibun]

Is it true that even if you cook meat infected with tapeworms very well, you can still become infected with it if you consume it?
EDIT: why is the answer A to the question attached?

[Biology24123]

"Describe the events that occur when non-self transplanted organs are rejected"

The answer only includes the cell-mediated response. I get how T-Helper cells are activated and actually activate Cytotoxic T cells and then these release cytotoxins to destroy the non-self cells, but, how come the production of antibodies is not included? Are the production of antibodies involved when non-self transplanted cells are introduced?

According to the course it's mainly the cell mediated response