VCE Biology Question Thread

[simrat99]

Hey guys, can somebody please tell me what passive defence mechanisms are in plants? And are we required to know about them? Thanks 

[Quantum44]

Hey guys, can somebody please tell me what passive defence mechanisms are in plants? And are we required to know about them? Thanks 

It's highly unlikely you will be asked about plant defences but it's useful to know about a few just in case. The ones I remembered for the exam were phytoalexins and waxy cuticles.

[anotherworld2b]

This is what I think but I'm not sure if this would be right considering duration increasing ( I have feeling heart rate would increase initially then stabilize at a certain point?) I would like to hear what other people think and why

I think that as the duration of exercise increases, heart rate will increase gradually. This would mean the cardiac output - amount of blood leaving one of the ventricles every minute - would increase as the rate of blood flow depends on how fast the heart is beating and how much blood the heart pumps with each beat.  To maintain the activity of the muscle cells during exercise, a large increase in blood flow is required to ensure an adequate supply of oxygen and nutrients, and to remove the carbon dioxide and heat produced.

The rate at which energy is released by the breakdown of food is called the metabolic rate. The factor with the greatest effect on the metabolic rate of an individual is exercise. During exercise, muscular activity can increase metabolic rate by up to 40 times so that very large quantities of heat are released. Thus the cardiac output may increase form 5L per minute at rest to a maximum of 30L per minute in a trained athlete. During exercise it is the contracting muscles that require the extra blood flow. Other organs do not need extra oxygen and nutrients and do not release extra carbon dioxide. To ensure that blood supply to the muscles is increased, blood vessels in internal organs contract. At the same time blood vessels in the muscles dilate. Blood is directed away from organs that do not require increased blood flow to the contracting muscles that do require more blood. When a person is about to begin, exercising, there is an anticipatory response brought about by the autonomic nervous system and by release of the hormone adrenaline, heart rate and stroke volume increase and there is an increase in the blood to skeletal muscles.

Tell us what you think first.

[vox nihili]

This is what I think but I'm not sure if this would be right considering duration increasing ( I have feeling heart rate would increase initially then stabilize at a certain point?) I would like to hear what other people think and why

I think that as the duration of exercise increases, heart rate will increase gradually. This would mean the cardiac output - amount of blood leaving one of the ventricles every minute - would increase as the rate of blood flow depends on how fast the heart is beating and how much blood the heart pumps with each beat.  To maintain the activity of the muscle cells during exercise, a large increase in blood flow is required to ensure an adequate supply of oxygen and nutrients, and to remove the carbon dioxide and heat produced.

The rate at which energy is released by the breakdown of food is called the metabolic rate. The factor with the greatest effect on the metabolic rate of an individual is exercise. During exercise, muscular activity can increase metabolic rate by up to 40 times so that very large quantities of heat are released. Thus the cardiac output may increase form 5L per minute at rest to a maximum of 30L per minute in a trained athlete. During exercise it is the contracting muscles that require the extra blood flow. Other organs do not need extra oxygen and nutrients and do not release extra carbon dioxide. To ensure that blood supply to the muscles is increased, blood vessels in internal organs contract. At the same time blood vessels in the muscles dilate. Blood is directed away from organs that do not require increased blood flow to the contracting muscles that do require more blood. When a person is about to begin, exercising, there is an anticipatory response brought about by the autonomic nervous system and by release of the hormone adrenaline, heart rate and stroke volume increase and there is an increase in the blood to skeletal muscles.

I suspect what the question is asking though is that if you did the same intensity of exercise, would one's heart rate increase or decrease as you keep on doing that exercise?

You know your physiology well, but I don't think you've addressed the question at hand.


THIS ISN'T VCE STUFF (just chuck that in there for anyone who's feeling overwhelmed).

[anotherworld2b]

Yes your assumption is correct. The experiment involves having a subject run 400m continuously and measuring their heart rate at intervals of 100m (100, 200, 400). But I'm still unsure what kind of trend will be shown in regards to heart rate increasing or decreasing or maybe another pattern. How could I explain the why this would happen better? Are there particular aspects I've missed or failed to explain in enough detail?

I suspect what the question is asking though is that if you did the same intensity of exercise, would one's heart rate increase or decrease as you keep on doing that exercise?

You know your physiology well, but I don't think you've addressed the question at hand.


THIS ISN'T VCE STUFF (just chuck that in there for anyone who's feeling overwhelmed).

[TheAspiringDoc]

Yes your assumption is correct. The experiment involves having a subject run 400m continuously and measuring their heart rate at intervals of 100m (100, 200, 400). But I'm still unsure what kind of trend will be shown in regards to heart rate increasing or decreasing or maybe another pattern. How could I explain the why this would happen better? Are there particular aspects I've missed or failed to explain in enough detail?

Where are you getting this question from? Are you a VCE student?
In a 400m run as fast as possible, the anaerobic energy systems (ATP-PC and anaerobic glycolysis) will contribute predominantly to the resynthesis of ATP and thus less oxygen will initially be required for aerobic cellular respiration. Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.
What this means is that the contribution of the aerobic cellular respiration pathway will continually by increasing throughout the event, and thus an increasing amount of oxygen will need to be delivered to the working muscles for aerobic cellular respiration. Since heart rate (along with stroke volume) is a key determinant of how much oxygen can be delivered to the working muscles, heart rate will increase throughout the event (note that the runner could theoretically also reach max heart rate towards the later stages).
Also, for clarification, a 20 minute run at 16km/h will result in a higher heart rate than if the same individual were to run for 20 minutes at 12km/h as a greater amount of ATP will need to be synthesised by the aerobic cellular respiration pathway due to the higher intensity.
A complicating factor in the experiment you're referring to is that the individual may have an anticipatory heart rate increase prior to their run.

[anotherworld2b]

I got this question from a prac. We have to discuss what would happen to heart rate as the duration of exercise increases and why. I am a WACE student

I attempted to another discussion of why heart rate would increase while keeping into consideration the information you provided. Would there be other aspects that would be beneficial to include in this discussion?

Spoiler

As the duration of exercise increases, heart rate will increase gradually until a max heart rate is reached. The increase in heart rate is necessary to maintain the activity of the muscle cells during exercise. To do this a large increase in blood flow is required to ensure an adequate supply of oxygen and nutrients, and to remove the carbon dioxide and heat produced. This would mean the cardiac output - amount of blood leaving one of the ventricles every minute - would increase as the rate of blood flow depends on how fast the heart is beating and how much blood the heart pumps with each beat. 

To maintain the activity of the muscle cells during exercise a source of energy is required. Cellular respiration is the process by which organic molecules are broken down in the cells to release energy for the cell's activities. Initially anaerobic respiration allows cells to produce some energy in the absence of oxygen from glucose. However, this results in the accumulation of lactic acid in the muscles and a oxygen debt from combining lactic acid with oxygen to form glucose. Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.To provide oxygen necessary for Aerobic respiration to maintain muscle activity and to ensure that blood supply to the muscles is increased heart rate will increase. Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. As heart rate increases and blood vessels in internal organs contract blood vessels in the muscles dilate. Blood is directed away from organs that do not require increased blood flow to the contracting muscles that do require more blood. Hence, heart rate will increase throughout the event.

 But I'm a bit confused on some parts of your answer and was hoping you could explain them further to me please.

Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles.

- what is PC stores? and why would they diminish?
- Why would anaerobic glycolysis system's contribution decline and will have to be performed by the aerobic cellular respiration pathway?
- Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. Does this refer to the fact that a increase in heart rate will increase how much oxygen is provided in the blood?

Where are you getting this question from? Are you a VCE student?
In a 400m run as fast as possible, the anaerobic energy systems (ATP-PC and anaerobic glycolysis) will contribute predominantly to the resynthesis of ATP and thus less oxygen will initially be required for aerobic cellular respiration. Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.
What this means is that the contribution of the aerobic cellular respiration pathway will continually by increasing throughout the event, and thus an increasing amount of oxygen will need to be delivered to the working muscles for aerobic cellular respiration. Since heart rate (along with stroke volume) is a key determinant of how much oxygen can be delivered to the working muscles, heart rate will increase throughout the event (note that the runner could theoretically also reach max heart rate towards the later stages).
Also, for clarification, a 20 minute run at 16km/h will result in a higher heart rate than if the same individual were to run for 20 minutes at 12km/h as a greater amount of ATP will need to be synthesised by the aerobic cellular respiration pathway due to the higher intensity.
A complicating factor in the experiment you're referring to is that the individual may have an anticipatory heart rate increase prior to their run.

[maria.ali]

hi quck question,
would complete selection have a greater effect over a dominant or recessive trait?

[Bri MT]

hi quck question,
would complete selection have a greater effect over a dominant or recessive trait?

what do you think? Keep in mind that recessive traits aren't always expressed, and it is the phenotype which is selected against.

[zxcvbnm18]

Are t helper cells specific?

[vox nihili]

Are t helper cells specific?

Yes

[anotherworld2b]

I am quite confused how the body switches between using anaerobic and aerobic respiration when a person runs a marathon.
I am also quite confused about how it relates to an increase of heart rate :/

I got this question from a prac. We have to discuss what would happen to heart rate as the duration of exercise increases and why. I am a WACE student

I attempted to another discussion of why heart rate would increase while keeping into consideration the information you provided. Would there be other aspects that would be beneficial to include in this discussion?

Spoiler

As the duration of exercise increases, heart rate will increase gradually until a max heart rate is reached. The increase in heart rate is necessary to maintain the activity of the muscle cells during exercise. To do this a large increase in blood flow is required to ensure an adequate supply of oxygen and nutrients, and to remove the carbon dioxide and heat produced. This would mean the cardiac output - amount of blood leaving one of the ventricles every minute - would increase as the rate of blood flow depends on how fast the heart is beating and how much blood the heart pumps with each beat. 

To maintain the activity of the muscle cells during exercise a source of energy is required. Cellular respiration is the process by which organic molecules are broken down in the cells to release energy for the cell's activities. Initially anaerobic respiration allows cells to produce some energy in the absence of oxygen from glucose. However, this results in the accumulation of lactic acid in the muscles and a oxygen debt from combining lactic acid with oxygen to form glucose. Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.To provide oxygen necessary for Aerobic respiration to maintain muscle activity and to ensure that blood supply to the muscles is increased heart rate will increase. Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. As heart rate increases and blood vessels in internal organs contract blood vessels in the muscles dilate. Blood is directed away from organs that do not require increased blood flow to the contracting muscles that do require more blood. Hence, heart rate will increase throughout the event.

 But I'm a bit confused on some parts of your answer and was hoping you could explain them further to me please.

Once the PC stores have diminished and the anaerobic glycolysis system's contribution also starts to decline, the ATP resynthesis will increasingly have to be performed by the aerobic cellular respiration pathway.Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles.

- what is PC stores? and why would they diminish?
- Why would anaerobic glycolysis system's contribution decline and will have to be performed by the aerobic cellular respiration pathway?
- Heart rate and stroke volume is a key determinant of how much oxygen can be delivered to the working muscles. Does this refer to the fact that a increase in heart rate will increase how much oxygen is provided in the blood?

[TheBigC]

hi quck question,
would complete selection have a greater effect over a dominant or recessive trait?

Note that if a dominant trait is acted against in complete selection, then - after one generation - the gene pool of the corresponding population (assuming no mutations or gene flow etc. (Hardy Weinberg population)) will consist entirely of recessive individuals, hence preventing the re-introduction of the dominant allele (as the recessive allele is fixed (q = 1.0)). To further emphasise this, imagine that the recessive trait was completely selected against, of which being eliminated in the next generation's gene pool, however, its allele frequency may not be 0: it may be 'hidden' in a heterozygous genotype (i.e. Aa), hence allowing for the allele to be re-introduced into the next generation again if two heterozygotes mate. Ultimately, as the allele is not lost in the population, the effect of complete selection against the recessive trait would be less impacting.

Hope this helped!

[anotherworld2b]

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?

[peachxmh]

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