HSC Biology Question Thread

[sidzeman]

Questions from the 2015 biology HSC
Q7 - why is the answer not thermoreceptors within the skin? Its them that detect changes from the norm temperature not the brain right?
Q15 I'm at a complete loss as how to do
Q23 - should the process not be DNA unzipping - how can we tell its DNA replication does DNA not also unzip during transcription

[Opengangs]

Questions from the 2015 biology HSC
Q7 - why is the answer not thermoreceptors within the skin? Its them that detect changes from the norm temperature not the brain right?

Q7: You're correct in that thermoreceptors detect changes within the skin, but these thermoreceptors merely send a signal to the brain. The brain enacts on these messages and sends them back to the arterioles and muscles. So, it is a trick question because really, two things happen at or near X.

For the full picture, we'd get:

Core body temp falls below normal -> Thermoreceptors detect these changes in the skin -> Hypothalamus (brain) enacts to these changes -> Signal is sent to the muscles and arterioles -> Return to normal body temp.

So, that's why the brain is the most correct answer.

Questions from the 2015 biology HSC
Q15 I'm at a complete loss as how to do

Q15: this is a pretty tough question, so don't feel bad!

If we read the question properly, we can see that: individual plants have either yellow, red or orange flowers.
Right off the bat, this implies either co-dominance or incomplete dominance as three phenotypes are involved.
We can then eliminate dominant/recessive relationships (B)

Next, the sentence tells us that two plants contain different flower colours. This allows us to eliminate (A).

We now have an even 50/50 split between (C) and (D). The question tells us that the breeding experiment was carried out like Mendel did.
If we recall how Mendel crossed his plants, the parent plants had to be pure bred or homozygous, meaning that (D) cannot be correct.

(C) will be the final answer (based on elimination).

Questions from the 2015 biology HSC
Q23 - should the process not be DNA unzipping - how can we tell its DNA replication does DNA not also unzip during transcription

Q23:
I see what you mean -- transcription or DNA unzipping is the process by which the DNA strand is copied into the mRNA. To observe why it's not transcription, consider what the end result of transcription is and what the end result of DNA replication is from a top-down perspective of the model. If we ever get a model, we should always approach the model with a top-down focus (ie from the top and reading the model going down), because that's the intended direction of how they are made.

Transcription is simply the unwinding and unzipping of the DNA strands using the enzyme helicase. It splits the two strands into its leading and lagging strands, while elongation (which is a process under DNA replication) is simply the synthesis of the complementary base pair onto the leading strand or the "template" strand.

Both of these "processes" comes under the umbrella process we call: DNA replication, which is the preferred process to name. But really, transcription and elongation are procedures that finally accumulate to the process of DNA replication.

[sidzeman]

Q7: You're correct in that thermoreceptors detect changes within the skin, but these thermoreceptors merely send a signal to the brain. The brain enacts on these messages and sends them back to the arterioles and muscles. So, it is a trick question because really, two things happen at or near X.

For the full picture, we'd get:

Core body temp falls below normal -> Thermoreceptors detect these changes in the skin -> Hypothalamus (brain) enacts to these changes -> Signal is sent to the muscles and arterioles -> Return to normal body temp.

So, that's why the brain is the most correct answer.
Q15: this is a pretty tough question, so don't feel bad!

If we read the question properly, we can see that: individual plants have either yellow, red or orange flowers.
Right off the bat, this implies either co-dominance or incomplete dominance as three phenotypes are involved.
We can then eliminate dominant/recessive relationships (B)

Next, the sentence tells us that two plants contain different flower colours. This allows us to eliminate (A).

We now have an even 50/50 split between (C) and (D). The question tells us that the breeding experiment was carried out like Mendel did.
If we recall how Mendel crossed his plants, the parent plants had to be pure bred or homozygous, meaning that (D) cannot be correct.

(C) will be the final answer (based on elimination).
Q23:
I see what you mean -- transcription or DNA unzipping is the process by which the DNA strand is copied into the mRNA. To observe why it's not transcription, consider what the end result of transcription is and what the end result of DNA replication is from a top-down perspective of the model. If we ever get a model, we should always approach the model with a top-down focus (ie from the top and reading the model going down), because that's the intended direction of how they are made.

Transcription is simply the unwinding and unzipping of the DNA strands using the enzyme helicase. It splits the two strands into its leading and lagging strands, while elongation (which is a process under DNA replication) is simply the synthesis of the complementary base pair onto the leading strand or the "template" strand.

Both of these "processes" comes under the umbrella process we call: DNA replication, which is the preferred process to name. But really, transcription and elongation are procedures that finally accumulate to the process of DNA replication.

Those are some really indepth responses hahhaaha thank you so much for your help!!

[Zizzle]

Hi,

I was wondering if anyone knew the distribution of the types of cones in the retina (red cones, green cones, blue cones). So like, what are the percentages of each.

Thanks!

[Daniyahasan]

Hi,

I was wondering if anyone knew the distribution of the types of cones in the retina (red cones, green cones, blue cones). So like, what are the percentages of each.

Thanks!

im pretty sure you dont need to know the percentage of them

[Mounica]

does anyway know an easy was to remember the function of veins/arteries/capillaries

[Daniyahasan]

does anyway know an easy was to remember the function of veins/arteries/capillaries

i like it remember it like this
Arteries take blood Away from the heart -- Arteries -> away
veins bring blood back to the heart
capillaries join the artieris and veins and are one cell thick
Hope that helps:)

[Mounica]

i like it remember it like this
Arteries take blood Away from the heart -- Arteries -> away
veins bring blood back to the heart
capillaries join the artieris and veins and are one cell thick
Hope that helps:)

Yup! makes sense
btw do arteries have valves or veins?
and what is the function of valves

[Daniyahasan]

Yup! makes sense
btw do arteries have valves or veins?
and what is the function of valves

Veins have valves (you can remember it like V-veins,valves)
veins stop the blood from flowing in the other direction

[pikachu975]

Q23:
I see what you mean -- transcription or DNA unzipping is the process by which the DNA strand is copied into the mRNA. To observe why it's not transcription, consider what the end result of transcription is and what the end result of DNA replication is from a top-down perspective of the model. If we ever get a model, we should always approach the model with a top-down focus (ie from the top and reading the model going down), because that's the intended direction of how they are made.

Transcription is simply the unwinding and unzipping of the DNA strands using the enzyme helicase. It splits the two strands into its leading and lagging strands, while elongation (which is a process under DNA replication) is simply the synthesis of the complementary base pair onto the leading strand or the "template" strand.

Both of these "processes" comes under the umbrella process we call: DNA replication, which is the preferred process to name. But really, transcription and elongation are procedures that finally accumulate to the process of DNA replication.

Transcription is copying DNA to mRNA not the unwinding of the DNA strand. Transcription is part of polypeptide synthesis not DNA replication.

i like it remember it like this
Arteries take blood Away from the heart -- Arteries -> away
veins bring blood back to the heart
capillaries join the artieris and veins and are one cell thick
Hope that helps:)

Just be aware that the pulmonary artery takes deoxygenated blood TO the heart, so not all arteries take it away.

[Opengangs]

Transcription is copying DNA to mRNA not the unwinding of the DNA strand. Transcription is part of polypeptide synthesis not DNA replication.

Oh, my bad! Haha, you're correct; transcription doesn't occur in the replication of DNA.

[av-angie-er]

Hi! For a question that asks for you to describe the work of three named scientists who have contributed to our understanding of inheritance, would it be appropriate to address Sutton and Boveri together, as well as Mendel and Morgan? So sort of like a packaged deal; equating their work to that of one scientist since their ideas are pretty similar? Thanks

[blasonduo]

Hi! For a question that asks for you to describe the work of three named scientists who have contributed to our understanding of inheritance, would it be appropriate to address Sutton and Boveri together, as well as Mendel and Morgan? So sort of like a packaged deal; equating their work to that of one scientist since their ideas are pretty similar? Thanks

yes! That seems like a great idea! Putting them as one can really strengthen your argument. The great part of these questions is the freedom we get! However, you could argue that you are talking about 4 scientists, but I doubt marks would be lost on that technicality

[av-angie-er]

yes! That seems like a great idea! Putting them as one can really strengthen your argument. The great part of these questions is the freedom we get! However, you could argue that you are talking about 4 scientists, but I doubt marks would be lost on that technicality

Ooh, good point! Thanks so much

[Arvacado]

Can someone please explain to me to action potential, membrane potential and depolarisation thing in Communication - I don't understand it    Thank you!