VCE Biology Question Thread

[Reus]

Bump. I don't understand this as well

I'm guessing it means structured weight and balance to gravity in allowing bipedalism to be efficient. What's the point of walking upright, if you limb 50cm left and right every time you walk ? - does not save energy at all.

[Reus]

What does 'heirloom parasite' mean? Is this in the SD? Cause it's off insight 2014.

[TimewaveZero]

What does 'heirloom parasite' mean? Is this in the SD? Cause it's off insight 2014.

A quick google returned this

Heirlooms are the parasites inherited from our primate ancestors in Africa, and souvenirs are those that we have acquired from the animals with which we have come in contact during our evolution, migrations, and agricultural practices.

[eagles]

Could Australopithecus handle tools?

See attached for question 7a.iii.
I thought it would be 16?
Because 2 x 4 x 2?
(2 - sex chromosomes, 4 - remaining chromosomes, 2 - other 2 to be selected from)

Thanks.

[TimewaveZero]

Would this be a satisfactory response for an allergy question (poison Ivy being the allergen)

Poison Ivy particles enter the body. These are recognised as foreign by antigen presenting cells (APC). T-cells recognise the proteins presented by the APC's and stimulate plasma cell production. These then produce many antibodies which bind to mast cells. The mast cells then reslease histamine when recognise Posion Ivy particles, resulting in the itchy red patches and blisters Paul experienced

[anat0my]

Do we have to know about photoperiodism? ALSO does anyone have a good definition for molecular clock and natural selection? THANKS!

[Reus]

Would this be a satisfactory response for an allergy question (poison Ivy being the allergen)

Poison Ivy particles enter the body. These are recognised as foreign by antigen presenting cells such as mast cells (APC). T-cells recognise the proteins presented by the APC's and release cytokine which stimulate's B-lymphoctes into plasma cell antibody production. These then produce many antibodies, specifically IgE antibodies which bind to mast cells. The mast cells then reslease histamine when recognised Posion Ivy particles, resulting in the itchy red patches and blisters Paul experienced

Just added extra stuff in red

[Reus]

Also what does it mean by "desensitisation" when referring to immunotherapy? Thanks.

[TimewaveZero]

does anyone have a good definition for molecular clock and natural selection? THANKS!

Molecular clock; the concept of estimating the time since two species diverged based on differences in molecular sequences, particularly protein sequence, due to the average rate of genetic mutations.

Natural selection; the concept that organisms better adapted to changes in their environment (selection pressures) are put at a selective advantage, and thus tend to survive to a greater extent and in turn have an overall higher reproduction rate, contributing their successful genome to future generations

If someone could add to these / make them better that would be great

[TimewaveZero]

Just added extra stuff in red

Thankyou! But I did not know mast cells where APCs??

[TimewaveZero]

Also what does it mean by "desensitisation" when referring to immunotherapy? Thanks.

Pretty sure it's just the process of making someone less 'sensitive' (may want to use a different word), to negative immune responses such as allergies. An example of this would be (i think) exposing children to nuts etc to reduce risk of allergic response?

[grannysmith]

Do we have to know about photoperiodism? ALSO does anyone have a good definition for molecular clock and natural selection? THANKS!

Nah, photoperiodism is off the course I think.
Molecular clock: using a known mutation rate to estimate the time of divergence of two species
Natural selection: I think VCAA's answer was something like "where a selective agent removes the unsuited, and the suited survive and reproduce".

Thankyou! But I did not know mast cells where APCs??

Yeah nah, they're not. APCs = macrophages, dendritic cells, B cells.

[That Other Guy]

Would this be a satisfactory response for an allergy question (poison Ivy being the allergen)

Poison Ivy particles enter the body. These are recognised as foreign by antigen presenting cells (APC). T-cells recognise the proteins presented by the APC's and stimulate plasma cell production. These then produce many antibodies which bind to mast cells. The mast cells then reslease histamine when recognise Posion Ivy particles, resulting in the itchy red patches and blisters Paul experienced

This illustrates a great understanding of the hypersensitive response, but you could maybe pare back on the T-cell activity. Looking at examiner's reports, they don't seem to care about that. This is what I would have said:

The allergen invades the body. It is detected as non-self and antibodies specific to the allergen are produced. These antibodies bind to receptors on mast cells. When the allergen is encountered again, the allergen-antibody complex is formed and histamine is released into the bloodstream, eliciting red patches and blisters.

The examiner's report said something similar, I believe.

[anat0my]

Pretty sure it's just the process of making someone less 'sensitive' (may want to use a different word), to negative immune responses such as allergies. An example of this would be (i think) exposing children to nuts etc to reduce risk of allergic response?

Just a side note - I did a commercial practice exam and it mentioned that using methods of desensitisation with nuts for people with nut allergies is not recommended by doctors because it can cause a severe response [anaphylactic shock]. The actual question asked something along the lines of why would doctors not use nut desensitisation methods or something like that.

[katiesaliba]

Natural selection; the concept that organisms better adapted to changes in their environment (selection pressures) are put at a selective advantage, and thus tend to survive to a greater extent and in turn have an overall higher reproduction rate, contributing their successful genome phenotype and the alleles its coded by to future generations

All members of the same species have the same genome.