HSC Biology Question Thread

[itssona]

heeey help pls

[Natasha.97]

heeey help pls

Hi,

Not 100% sure, but I think the answer is C:
- Autotrophs make their own food by converting inorganic molecules to organic compounds (e.g. through photosynthesis)
- Heterotrophs have to consume autotrophs to produce energy, and they respire (which provides CO₂ for the autotrophs)

Hope this helps

[itssona]

Hi,

Not 100% sure, but I think the answer is C:
- Autotrophs make their own food by converting inorganic molecules to organic compounds (e.g. through photosynthesis)
- Heterotrophs have to consume autotrophs to produce energy, and they respire (which provides CO₂ for the autotrophs)

Hope this helps

thank you!!!

[sidzeman]

For those who do the genetics elective
  - can someone please explain the difference between homeotic and homeobox and hox genes?

[pikachu975]

For ectotherms and endotherms how do their metabolism AND enzyme rates differ at different temperatures?

[Mathew587]

For ectotherms and endotherms how do their metabolism AND enzyme rates differ at different temperatures?

Endotherm
At a low temp,

• Metabolism increases to maintain body temp and function
  Enzyme rates stay contstant due to a regulated internal environment- homeostasis. However, extreme temps will result in denaturing (obv)

At a normal temp,

• Metabolism is normal
  Enzyme rate is normal

At a high temp,

• Metabolism is higher once again as body needs to work harder to maintain homeostasis
  Enzyme rate stays constant due to homeostasis. However, extreme temps will result in denaturing (once again obv)

Ectotherm
At a low temp,

• metabolism is low cos unable to do shit
  Enzyme rate is low cos of dependency on ext temp for function. will result in denaturing if extreme temps

At a normal temp,

• metabolism is normal
  enzyme rate is normal

At a high temp,

• Metablosim is way higher as activity correlates with temperature increase
  Enzyme rate is higher till peak is reached followed by drops and eventual denaturing.

you could have just thought about it...

[vanessa mbogo]

Use your understanding of genetics and evolution to explain  why some charcteristics becomes more common in a population than others please help

[vox nihili]

Use your understanding of genetics and evolution to explain  why some charcteristics becomes more common in a population than others please help

You need to have a crack at this first then we'll help

[gh971]

Could someone please help me with how to best answer this question??

Compare the way mammals transport oxygen and carbon dioxide in the blood. (4 MARKS)

This is my answer but I'm worried I'm missing things:
Mammalian blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body.These gases are carried in various forms such as dissolved in the plasma or chemically combined with haemoglobin. For oxygen transport, oxygen binds with haemoglobin in the lungs, where the oxygen concentration in the blood is low, and transports it to where the oxygen is needed. Once it reaches the desired location the oxygen bond easily breaks and the oxygen is used for processes such a respiration. However, for carbon dioxide transport it is carried in the blood in in two forms; dissolved in plasma and travels as bicarbonate ions resulting from the dissociation of carbonic acid.

[Natasha.97]

Could someone please help me with how to best answer this question??
Compare the way mammals transport oxygen and carbon dioxide in the blood. (4 MARKS)

Hi!

I'm sitting the HSC this year (so not entirely sure if I'm correct), but I've included some comments below:

Mammalian blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body.Good introductory sentence These gases are carried in various forms such as dissolved in the plasma or chemically combined with haemoglobin. For oxygen transport, oxygen binds with haemoglobin in the lungs, where the oxygen concentration in the blood is low, and transports it to where the oxygen is needed. Once it reaches the desired location the oxygen bond easily breaks and the oxygen is used for processes such a respiration Not entirely sure about the relevance of this sentence to the question. However, for carbon dioxide transport it is carried in the blood in in two forms; dissolved in plasma and travels as bicarbonate ions resulting from the dissociation of carbonic acid.You've talked about the similarities and differences between these two gases, which directly addresses the question

Could include statistics for both of the gases:
CO₂:
         - HCO₃^2- = 70%
         - Carbamino-haemoglobin molecules in red blood cells = 23%
         - Dissolved directly in the plasma = 7%
O₂:
         - Carried by red blood cells in the form of oxyhaemoglobin = 98.5%
         - Dissolved in plasma = 1.5%

Hope this helps

[pikachu975]

Endotherm
At a low temp,

• Metabolism increases to maintain body temp and function
  Enzyme rates stay contstant due to a regulated internal environment- homeostasis. However, extreme temps will result in denaturing (obv)

At a normal temp,

• Metabolism is normal
  Enzyme rate is normal

At a high temp,

• Metabolism is higher once again as body needs to work harder to maintain homeostasis
  Enzyme rate stays constant due to homeostasis. However, extreme temps will result in denaturing (once again obv)

Ectotherm
At a low temp,

• metabolism is low cos unable to do shit
  Enzyme rate is low cos of dependency on ext temp for function. will result in denaturing if extreme temps

At a normal temp,

• metabolism is normal
  enzyme rate is normal

At a high temp,

• Metablosim is way higher as activity correlates with temperature increase
  Enzyme rate is higher till peak is reached followed by drops and eventual denaturing.

you could have just thought about it...

Thanks for this, but pretty sure metabolism decreases at high temps for endotherm cause it produces heat

[Opengangs]

Could someone please help me with how to best answer this question??

Compare the way mammals transport oxygen and carbon dioxide in the blood. (4 MARKS)

This is my answer but I'm worried I'm missing things:
Mammalian blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body.These gases are carried in various forms such as dissolved in the plasma or chemically combined with haemoglobin. For oxygen transport, oxygen binds with haemoglobin in the lungs, where the oxygen concentration in the blood is low, and transports it to where the oxygen is needed. Once it reaches the desired location the oxygen bond easily breaks and the oxygen is used for processes such a respiration. However, for carbon dioxide transport it is carried in the blood in in two forms; dissolved in plasma and travels as bicarbonate ions resulting from the dissociation of carbonic acid.

Hey!

When we're dealing with 4-5-6 mark questions, the best way to approach them is to create a plan or to break down how these marks may be obtained. Remember that these 4 mark questions can actually be asked in four separate 1 mark questions, so always try to break them down to its simplest form.

Compare the way mammals transport oxygen and carbon dioxide in the blood.
So, obviously we need to describe how mammals transport oxygen in the blood, which constitutes one mark.
We then need to describe how they transport carbon dioxide in the blood, which constitutes another mark.
Since the question is a compare question, we need to identify the similarities (1 mark) and the differences (1 mark) between the processes.

This will give you your 4 marks, so using this scaffold as the basis of your answer, let's compare how you may have been marked in an actual exam.

Mammalian blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body. These gases are carried in various forms such as dissolved in the plasma or chemically combined with haemoglobin. For oxygen transport, oxygen binds with haemoglobin in the lungs, where the oxygen concentration in the blood is low, and transports it to where the oxygen is needed. (1) Once it reaches the desired location the oxygen bond easily breaks and the oxygen is used for processes such a respiration. However, for carbon dioxide transport it is carried in the blood in in two forms; dissolved in plasma and travels as bicarbonate ions resulting from the dissociation of carbonic acid. (1)

You may scrape three marks, but it's a very risky three marks. You'll definitely get at least two since you've described the process for both oxygen and carbon dioxide, but explore the similarities and differences a bit more when comparing the two. Let me know if you have any more trouble.

[angelahchan]

Hi I've really struggled with graphs like no matter how hard I try I always seem to stuff them up (maths has never been my strong point). I just wanted to clarify a few things bc I've gotten different responses from different teachers about certain things. Firstly I don't understand when you are supposed to join the dots or draw a line of best fit (I lost a mark in trials for drawing a LOBF). Also I get confused over whether you are supposed to connect the first dot to 0 or not ? Thirdly, I find I always have doubt over whether to use a bar or line graph and I always end up picking the wrong one, I understand that line is usually continuous data and discrete for bar (I think), but I still get confused about it all like in one of my exams they wanted a bar graph for an experiment involving time?? Anyway, some clarification would be super helpful as the graph in trials seriously stuffed up the majority of my exam after I did the entire thing wrong after spending 15 mins on it and had to start all over again (leaving me with 5 mins to do the 7 marker which was not ideal haha). 

1) Usually you join the dots freehand- I don't think I've done a hsc question which asks you for line of best fit, but if the points seem really scattered e.g. you can't draw a clean curve/line with it you may have to do best fit
2) I think that depends on the question, but start at the first value they give you e.g. if you have to a graph an experiment and it starts at room temp of, say, 28 degrees then start at 28  rather than 0 (and if the experiment is based on time then obviously time has to start at 0)
3) sorry  I've never done a past hsc with bar graphs before so I can't really give advice here- maybe if you have the question with you you can post it here to get clarification?

idk if this is helpful, but here's a  few tips for line graphs:
1) have a title
2)put  independent on x axis, dependent on y
3) remember to label axis with units

[Daniyahasan]

Use your understanding of genetics and evolution to explain  why some characteristics become more common in a population than others please help

According to Darwin/Wallace's theory of natural selection, the organisms with traits best suited to their environment will survive and reproduce, passing on the favourable trait to their offspring, while the ones without the favourable trait will eventually die out in the population. Hence favourable traits will become more common in population

shit answer sorry, but i tried, hope it helps:)

[Sine]

Use your understanding of genetics and evolution to explain  why some charcteristics becomes more common in a population than others please help

-genetic variation exists in a population
-Selection pressure may exist
-some phenotypes are more favourable than others under this selection pressure hence more likely to survive and reproduce
-allele frequencies change
-Hence over time the favourable characteristics are more common in the population