VCE Biology Question Thread

[vox nihili]

I was looking at a graph for heart rate which spiked up dramatically for the first 100m then gradually slowed down the extent of increase as the distance the subject jogged increased to 200,300 and 400m. I was wondering what would be the best why to explain why there is a spike at the beginning at 100m then a slow gradual increase at 200, 300 and 400m?

Graph the change in activity intensity next to it. That'll show you why

[PhoenixxFire]

On the study design for Unit 1, there's a section called 'Functioning systems' under Area of Study 1.

Basically it says:
- a study of one selected vascular plant with reference to how its cells are specialised and organised (cells into tissues and tissues into organs) for the intake, movement and loss of water from the plant
- a study of one selected mammalian system (circulatory, digestive, excretory or respiratory) with reference to how cells in the system are specialised and organised (cells into tissues, tissues into organs and organs into systems), how a specific malfunction can lead to biological consequences and how the system is interconnected to other systems for the survival of the organism

I was revising some content from Unit 1 but realised my teacher had completely left this section out (don't you just love it when this happens  ) and that we haven't covered anything about it. What should I know from this topic? How important/relevant is it to Units 3/4? Also, for the second point about the mammalian systems, would be beneficial to learn about all of them? How in-depth should I go?

Thank you in advance 

In terms of Units 3/4 none of that is really relevant at all. I wouldn't worry about it given Unit 1 is done. If you want to, the parts I would suggest looking at would be making sure you know how water is taken from the roots all the way up to the leaves and then evaporation (transpiration) in vascular plants. Also, the point about mammalian specialisation and malfunctions is probably intended as a introduction to immunity/disease which is in U3. Its not really relevant specifically, sort of just background knowledge. I would advise making sure you know about cell specialisation/ when this occurs and what cells can differentiate in embryos/adults. It's not specifically relevant but is useful to make links between concepts you learn.

You don't really need to know about the different systems in 3/4 just be aware of what they are. If you really want to investigate one go with circulatory or excretory. The circulatory system is probably the most relevant to 3/4 (particularly look at lymph vessels, nodes, etc. they are relevant to immunity in 3/4.

Also i see its your first post. Welcome to AN. Unless you've been a lurker for a while in which case congrats on actually posting!

[anotherworld2b]

Graph the change in activity intensity next to it. That'll show you why

I'm not still not sure why?

[vox nihili]

I'm not still not sure why?

NOT VCE RELEVANT FOR OTHERS READING

Initial sharp increase is obviously because of the sharp increase in activity intensity. Moving from standing to a jog. Then it continues to increase as you deplete your anaerobic sources of energy and start to switch to aerobic energy production.

[anotherworld2b]

Why would the graph continue to gradually increase from the initial spike?
Would it be due to a build up of lactic acid from anaerobic respiration at the start of a experiment?
I was wondering would the body want to increase heart rate to allow the lactic acid to be carried away by the blood to the liver, where it is broken down? Would this be happening as the person is still jogging?

NOT VCE RELEVANT FOR OTHERS READING

Initial sharp increase is obviously because of the sharp increase in activity intensity. Moving from standing to a jog. Then it continues to increase as you deplete your anaerobic sources of energy and start to switch to aerobic energy production.

[anotherworld2b]

Would my explanation successfully explain why the graph continue to gradually increase from the initial spike? Is there anything I am missing for a complete explanation?

Spoiler

Initially anaerobic respiration allows cells to produce some energy in the absence of oxygen from glucose. This results in the accumulation of lactic acid in the muscles and an oxygen debt from combining lactic acid with oxygen to form glucose and eventually glycogen. Heart rate continues to increase as the subject depletes their anaerobic sources of energy and starts to switch to aerobic energy production from 200 metres to 400 metres. As the subject’s speed and activity intensity remains the same from 200 metres onwards, the amount of oxygen required for the activity remains the same and a sharp increase in heart rate is not necessary to maintain a steady jog. Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. To provide sufficient oxygen necessary for aerobic respiration to maintain muscle activity and to ensure that blood supply to the muscles is adequate, heart rate will increase gradually from 200 metres onwards. The increased heart rate allows lactic acid to be carried away by the blood to the liver, where it is broken down. It also allows the oxygen debt incurred by the body to be slowly repaid.

[vox nihili]

Would my explanation successfully explain why the graph continue to gradually increase from the initial spike? Is there anything I am missing for a complete explanation?

Spoiler

Initially anaerobic respiration allows cells to produce some energy in the absence of oxygen from glucose. This results in the accumulation of lactic acid in the muscles and an oxygen debt from combining lactic acid with oxygen to form glucose and eventually glycogen. Heart rate continues to increase as the subject depletes their anaerobic sources of energy and starts to switch to aerobic energy production from 200 metres to 400 metres. As the subject’s speed and activity intensity remains the same from 200 metres onwards, the amount of oxygen required for the activity remains the same and a sharp increase in heart rate is not necessary to maintain a steady jog. Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. To provide sufficient oxygen necessary for aerobic respiration to maintain muscle activity and to ensure that blood supply to the muscles is adequate, heart rate will increase gradually from 200 metres onwards. The increased heart rate allows lactic acid to be carried away by the blood to the liver, where it is broken down. It also allows the oxygen debt incurred by the body to be slowly repaid.

I'm not really sure to be honest. Exercise med is not a forté and obviously not a part of the VCE course. You might have more luck asking this question in the PE thread, but just remember to note that you're a WACE student so people don't get freaked out by the level of detail

[anotherworld2b]

I see
thank you for your help anyway

I'm not really sure to be honest. Exercise med is not a forté and obviously not a part of the VCE course. You might have more luck asking this question in the PE thread, but just remember to note that you're a WACE student so people don't get freaked out by the level of detail

[simrat99]

Hey guys, is the membrane of a chloroplast selectively permeable or can any substance enter? Thanks

[vox nihili]

Hey guys, is the membrane of a chloroplast selectively permeable or can any substance enter? Thanks

All membranes by definition are selectively permeable.

[KANYEWEST]

Hey Everyone!
I have a question that i was having difficulty explaining and it is to do with Industrial revolution Peppered moths,

here is the question"

A student argued that the allele for the dominant dark phenotype in moths could be wiped out more easily in unpolluted forests than the allele for the recessive light phenotype in polluted forests because of the fact that the dominant allele always shows up when it is present in an individual’s genotype.

I understand what this question is saying, but i need somone to explain it to me so i can actually put something down on my paper 

So,If someone would help explain this to me, it would be truely appriciated! thank you xx

[plsbegentle]

Hey Everyone!
I have a question that i was having difficulty explaining and it is to do with Industrial revolution Peppered moths,

here is the question"

A student argued that the allele for the dominant dark phenotype in moths could be wiped out more easily in unpolluted forests than the allele for the recessive light phenotype in polluted forests because of the fact that the dominant allele always shows up when it is present in an individual’s genotype.

I understand what this question is saying, but i need somone to explain it to me so i can actually put something down on my paper 

So,If someone would help explain this to me, it would be truely appriciated! thank you xx

I'm sorry, but what exactly is the question?

[Katt97]

lmao i forgot to copy paste the entire question, i really should have re-read what i wrote,
sorry bout that,

here is the question!

A student argued that the allele for the dominant dark phenotype in moths could be wiped out more easily in unpolluted forests than the allele for the recessive light phenotype in polluted forests because of the fact that the dominant allele always shows up when it is present in an individuals genotype. Do you agree or disagree? Explain why you think so.

the question is to do with the moths during the industrial revolution and how the white moths were getting wiped out due to pollution- making them more visible etc.

if the question still doesnt make sense and you need more context to it, please let me know!

thank you so much

Hi Kanye,

I think the best way to explain this question is to write out the two different conditions in terms of genotypes and phenotypes.

first up let's assign alleles as D= dark and d= light (for moth colour).

Condition 1: polluted forest (trees will be dark in colour due to pollution).
 moths that are DD will be dark, will blend in with the trees and therefore are less likely to be eaten
moths that are Dd will be dark and again, will be less likely to be eaten
moths that are dd will be light, won't blend in and are more likely to be eaten

Condition 2: unpolluted forest (trees will be light in colour)
moths that are DD will be dark, won't blend in and are more likely to be eaten
moths that are Dd will be dark, won't blend in and are more likely to be eaten
moths that are dd will be light, will blend into the trees and are less likely to be eaten

Now let's compare the two situations.  You can see that in an unpolluted forest,  because the D allele is dominant and is therefore expressed in both the homozygote and heterozygote the D allele is always going to be selected against, whereas in the polluted forest the light phenotype is only seen when the moth is homozygous recessive (dd). The moths that have the genotype Dd will be dark, and therefore less likely to be selected against. This means that the light allele (d) is only selected against in the homozygote not both the heterozygote and homozygote as seen in the previous condition. Essentially in the polluted forrest, the D allele masks/protects the d allele in the heterozygote so it is more likely to remain in the population.
(Therefore I'd agree with the student).
Sorry for the long-winded answer, I hope that helps!

[PhoenixxFire]

I don't think we need to know this for VCE but does anyone know if MHC 1 and MHC 2 are structurally different? or do they just have different names because one presents proteins it has produced and the other proteins made by a pathogen?

If they are structurally the same then would a cytotoxic T cell that can bind to the antigen being presented kill it not knowing that it isn't an infected cell?
If they are not structurally the same then would a cytotoxic T cell be unable to bind to its MHC markers (because they're MHC 2 not 1) (on a side note they have both right?) and therefore kill it?

I know its not really VCE relevant but i'm a curious person so if anyone can explain it that would be awesome

[vox nihili]

I don't think we need to know this for VCE but does anyone know if MHC 1 and MHC 2 are structurally different? or do they just have different names because one presents proteins it has produced and the other proteins made by a pathogen?

If they are structurally the same then would a cytotoxic T cell that can bind to the antigen being presented kill it not knowing that it isn't an infected cell?
If they are not structurally the same then would a cytotoxic T cell be unable to bind to its MHC markers (because they're MHC 2 not 1) (on a side note they have both right?) and therefore kill it?

I know its not really VCE relevant but i'm a curious person so if anyone can explain it that would be awesome

This isn't a question that would necessarily be asked to a VCE student; however, it's the kind of question you should be considering. There's no need to make excuses for asking it; it's a good one

I'm going to clear up a couple of misconceptions you've made and then I want you to tell me whether or not they're structurally identical.

This is important VCE knowledge

MHC class I molecules express antigens from inside cells. They are recognised by cytotoxic T-cells, which kill cells that have been infected. Therefore, a simple way of looking at this is that MHC class I molecules exist to deal with intracellular infections (usually viruses, but some bacteria and parasites, too). These molecules are expressed by all nucleated cells.

MHC class II molecules are only expressed on antigen-presenting cells, which take antigens from the environment and then present them on their surface. On T-helper cells respond to these molecules. Therefore, these MHC molecules give an insight into the pathogens present in the extracellular environment.