VCE Biology Question Thread

[PhoenixxFire]

The humoral immune response definitly does occur - it also occurs during viral infections. Generally though that is not what VCAA wants to know about. So whilst it isn't wrong, it's about understanding what VCAA wants which will generally be cell mediated immunity. If you want to talk about it I would just say that it's activated and not go into too many details.

[LifeisaConstantStruggle]

Yeah exactly. I typed that just to make sure we're not in the assumption that only cell-mediated responses occur in these scenarios. Thank you.

[ezferns]

Thanks for the quick reply!

VCAA has defined a hormone as 'a chemical compound produced in a cell that either acts within the cell or diffuses or is transported to other
cells where it brings about a specific response'
If this is the case then what is the difference between a hormone and a neurotransmitter or cytokine?

[PhoenixxFire]

Thanks for the quick reply!

VCAA has defined a hormone as 'a chemical compound produced in a cell that either acts within the cell or diffuses or is transported to other
cells where it brings about a specific response'
If this is the case then what is the difference between a hormone and a neurotransmitter or cytokine?

The study design on these points have changed. We need to know the source and mode of transmission so a hormone is a chemical signalling molecule released by an endocrine gland that travels through the blood. A neurotransmitters is a chemical signalling molecule that is released into the synaptic gap by a pre synaptic neuron and a cytokine is a chemical signalling molecule released into the blood or lymph by an immune cell.

[ezferns]

Oh damn thats confusing then cos VCAA wrote for Q 6c 2008 E1
'Students needed to expand at least in part on the definition provided, taking into
account other examples of hormones they had studied. Too often, the new definition was even shorter than that given or
was made more specific and hence more incorrect; for example, ‘produced by endocrine glands’. '

[PhoenixxFire]

Yeah it's weird because of the study design changes. You can probably define hormones without mentioning endocrine glands but I haven't written a good definition. We need to mention that they travel in the bloodstream (throughout the whole body) though.

[LifeisaConstantStruggle]

Oh damn thats confusing then cos VCAA wrote for Q 6c 2008 E1
'Students needed to expand at least in part on the definition provided, taking into
account other examples of hormones they had studied. Too often, the new definition was even shorter than that given or
was made more specific and hence more incorrect; for example, ‘produced by endocrine glands’. '

Ah this question. They have reverted back to the usual definition we've been using since the universe began so  also that question was made 11 years ago, so it's sort of irrelevant mate.

[ezferns]

Alright lucky I checked with you guys before using that definition in the future haha

[zxcvbnm18]

what are the key points needed when we defining allopatric speciation?

[PhoenixxFire]

what are the key points needed when we defining allopatric speciation?

A definition: The formation of a new species as a result of the ancestral population becoming isolated by a geographical barrier.
For a scenario question:
GSD
G Geographical Isolation
S Selection Pressures - The groups face different selection pressures, causing them to evolve differently
D Differences accumulate to the point where, if brought back together they will not interbreed to produce fertile, viable offspring.

[vox nihili]

Thankyou!!

When talking about organ rejection, is it incorrect to talk about both the action of Tc cells and B plasma cells? I did q5b VCAA 2008 E1 and it only mentioned the cell mediated response in the answer.

They really should reward you for talking about the humoral response. Organ rejection can involve a predominantly B-cell mediated response, particularly if it happens early on. Later rejection often involves cell mediated responses.

These details are obviously extraneous to VCE, but I’ve provided them out of interest and just to highlight the fact that sometimes the way VCAA conceptualises topics strays a little from the reality—all the more reason to continue studying biology after VCE

[vox nihili]

Yeah it's weird because of the study design changes. You can probably define hormones without mentioning endocrine glands but I haven't written a good definition. We need to mention that they travel in the bloodstream (throughout the whole body) though.

Sorry for the double post, on phone.

My suspicion is that the previous study design didn’t like endocrine glands because not all hormones are produced by them. Take for example neurohormones, which are produced by nervous tissues rather than endocrine glands. Anything produced by the posterior pituitary fits into this class of hormones.

[ringring]

Hey everyone!
In DNA hybridisation, does a higher or lower temperature indicate closer relatedness between species?

[PhoenixxFire]

Hey everyone!
In DNA hybridisation, does a higher or lower temperature indicate closer relatedness between species?

The higher the temperature the more closely related they are.
Species that are more closely related have more matching DNA bases therefore more hydrogen bonds can form, which requires more energy (heat) to break

[ringring]

Thanks PheonixxFire

Also , can someone pls outline the general steps of antibiotic resistance in bacteria?