VCE Biology Question Thread

[millie96]

Why would variation in mtDNA be greater in African populations than other populations according to the out-of-African hypothesis?

out-of-Africa theory proposes that all humans diverged from Africa - suggesting its the oldest source of a population.

so, because mutations occur over time, the more mutations, the longer the time since divergence. more mutations in African populations = longer time since divergence = supports hypothesis that every hominon diverged from Africa

[millie96]

Can somebody explain to me the electrical transmission mechanisms through the Na+/L+ pumps? Ive never understood what happens with calcium and ions etc etc can someone please put it into terms?

[Sup]

I said the nature of a particular hormone was water-soluble. VCAA's answers were one of: protein based, hydrophilic or polar. Would I still be given a mark?

[shivaji]

I said the nature of a particular hormone was water-soluble. VCAA's answers were one of: protein based, hydrophilic or polar. Would I still be given a mark?

hydrophilic = water soluble

[ValiantIntellectual]

katiesaliba is correct; here's a bit of an elaboration.

A bat's wing looks like this:

While a bird's wing looks like this:

Can you tell an important difference between the two?

Spoiler

It's that with the bat's wing there are 5 digits (akin to fingers - pentadactyly). Bird wings usually only demonstrate three digital bones (tridactyly).

From that, we can infer that although both structures are involved in the same general function (flight), they are quite clearly anatomically and structurally distinct. There are several other ways of understanding this, such as presence/absence of feathers between the two animals.

Because function is roughly the same but other characteristics are not, we can say that the structures are homologous.

That's what I thought but this site is telling me other wise https://www.mun.ca/biology/scarr/Analogy_of_forelimbs.htm

It says they are analogous as wings but homologous as forelimbs? I don't understand how something can be both analogous and homologous at the same time!

[RazzMeTazz]

Are we allowed to bring tissues into the examination?

[doomdestroyer]

Are we allowed to bring tissues into the examination?

I don't see why not.

[RazzMeTazz]

For this question VCAA defined a hormone as " a chemical compound produced in a cell. It either acts within the cell or diffuses or is transported to other cells where it brings about a specific response."

The assessment report said that stating things like "produced by endocrine glands" are more specific and hence are even more incorrect than the original definition in the question stem.

Does that mean not all hormones are produced by endocrine glands? Also the VCAA definition outlines hormones are being able to act within cells. Can someone give an example of when hormones act within cells? o.O

[Chang Feng]

For the VCE biology exams, are the multiple choice answer sheet scanned? Does the marking have to be dark and does it matter if square not fully shaded? If you know? Thanks

[joecantwell]

For the VCE biology exams, are the multiple choice answer sheet scanned? Does the marking have to be dark and does it matter if square not fully shaded? If you know? Thanks

Yeah the multiple choice sheet is scanned so you would want to make sure that the square is filled and dark enough to scan properly 

[althepal]

Can anyone explain this question to me? The correct answer is B

[howlingwisdom]

I was wondering, could anyone explain to me why the answer is B and not A?

Thank you!

[lzxnl]

I was wondering, could anyone explain to me why the answer is B and not A?
(Image removed from quote.)
Thank you!

Well...it's a flowering plant, so I'm assuming we're looking at the diploid sporophyte here
So, you're crossing Hh; Ww with hh; ww
The possible gametes are HW, Hw, hW and hw vs hw only
You'll get Hh;Ww, Hh;ww, hh;Ww, hh;ww as the possibilities
Out of the fruit without hair, or the hh ones, there is one fruit with ww and one fruit with Ww => B is correct

[alondouek]

That's what I thought but this site is telling me other wise https://www.mun.ca/biology/scarr/Analogy_of_forelimbs.htm

It says they are analogous as wings but homologous as forelimbs? I don't understand how something can be both analogous and homologous at the same time!

Yep, my earlier post was a bit ambiguous and I've added a bit of a clarification as an edit at the end.

Basically, what you've linked is correct; wing structures in different animals (assuming they have a flight function) are ANALOGOUS structures. They have dissimilar anatomy (different dactyly) but similar function.

The forelimb structures are NOT the same as the wing structures in these animals. They are functionally different but anatomically similar, which makes them HOMOLOGOUS.

So in short, a structure cannot be BOTH homologous AND analogous. However, two closely-related anatomical structures could very well be either homologous or analogous (as is the case here) - but any single structure never can be both.

Hope that clears things up!

[althepal]

I was wondering, could anyone explain to me why the answer is B and not A?
(Image removed from quote.)
Thank you!

Well the expected phenotypic ratio is 1hair and yellow:1hair and white:1 no hair and yellow:1 no hair and white. Therefore half of the hairless ones will be white so B is correct. A is incorrect as only half of the offspring would have hair. As for how you get the phenotypic ratio you just have to know that a dihybrid test cross (heterozygous x homozygous recessive) will have a phenotypic ratio of 1:1:1:1 provided the genes are not linked.