VCE Biology Question Thread

[grannysmith]

what exactly does reproductive isolation refer to?
is it during allopatric speciation when the original population can not breed with each other as they are separated from each other?
or does it refer to the fact that two species are reproductively isolated as they can't reproduce?

Reproductive isolation leads to speciation, but it's not definitely not allopatric. I think it's sympatric but that's not in the course.

It includes prezygotic isolating mechanisms (different mating behaviours, structural incompatibilities) and postzygotic mechanisms (unviable/infertile offspring).

[AllG_]

How do antibodies act on viruses? Also how do memory B cells work to produce a faster and greater amount of antibodies upon detection of antigen? Do they, too, undergo clonal expansion, divide into plasma cells etc.?

[Rishi97]

anyone know a simple yet good definition for natural selection that I can use for exams?

[grannysmith]

How do antibodies act on viruses? Also how do memory B cells work to produce a faster and greater amount of antibodies upon detection of antigen? Do they, too, undergo clonal expansion, divide into plasma cells etc.?

Specific antibodies attach to antigens on the virus surface, making it easier for phagocytes to recognise and engulf the viruses.
The more B memory cells there are, the greater the amount of antibodies that can be produced, and at a faster    rate. This is what produces a faster and greater response.
Yes, they basically clone and differentiate into plasma B cells and some memory B cells.

[Reus]

anyone know a simple yet good definition for natural selection that I can use for exams?

The process in which organisms that are better suited to their environment are able to survive hence reproduce offspring.

[AllG_]

Thanks grannysmith!

Another question: for one of the VCAA questions which asked something along the lines of "suggest how this hormone can produce different responses in different cells", one of the answers were that they had different receptors. But how can one hormone with a specific shape bind to different receptors??

And how and why did humans develop cheekbones the way they did? And why did humans develop a more compact pelvis?

[Reus]

And why did humans develop a more compact pelvis?

Balance of weight and bipedalism in order to walk upright efficiently. So basically structural support.

[Reus]

A question of my own, when explaining a reflex arc is it correct to say "... a response in which the brain is no included (as the response needs to be fast" or would I have to say "... in which the central processing unit is not included.."? Thanks!

[AllG_]

A question of my own, when explaining a reflex arc is it correct to say "... a response in which the brain is no included (as the response needs to be fast" or would I have to say "... in which the central processing unit is not included.."? Thanks!

A reflex arc is a pathway from a receptor to an effector that does not involve the brain. It DOES go to a central processing point (usually the spinal cord) in the CNS

[maddihanna]

2 questions:
the vcaa 2013 sample exam has the question: "explain how the message is transmitted along the axon of the post-synaptic neuron" and my teachers and my description of action potential are very different however both seem right, I'd love to see how you guys would answer that question.

Also, how much depth should I know for the allergic response?

[anat0my]

A question of my own, when explaining a reflex arc is it correct to say "... a response in which the brain is no included (as the response needs to be fast" or would I have to say "... in which the central processing unit is not included.."? Thanks!

Both is fine. You could say that it bypasses the brain but engage solely with the peripheral nervous system.


What's a good definition for recombination? thanks!

[grannysmith]

A question of my own, when explaining a reflex arc is it correct to say "... a response in which the brain is no included (as the response needs to be fast" or would I have to say "... in which the central processing unit is not included.."? Thanks!

A reflex arc is an automatic response that occurs without involvement of the brain. It brings about a fast/immediate response (to protect the body from damage).

This was a VCAA answer I think.

[Reus]

Thanks guys!

[anat0my]

2 questions:
the vcaa 2013 sample exam has the question: "explain how the message is transmitted along the axon of the post-synaptic neuron" and my teachers and my description of action potential are very different however both seem right, I'd love to see how you guys would answer that question.

Also, how much depth should I know for the allergic response?

-Threshold is reached.
-Consequently sodium channels open causing an influx of Na+ into the axon, thus propagating the impulse causing depolarisation (was initially polarised).
-To correct this, Potassium channels open, allowing for K+ for flow out of the axon, hence repolarising the membrane.

Yeah iffy explanation. Can someone polish this up plz.

[Tyleralp1]

Always receiving conflicting information from sources..

Are they Na+/K+ pumps, ion channels?
Protein carriers or channels?

Some even say depolarisation is ion channels, whist repolarisation is active transport for pump/carriers.

Please end my confusion haha!