IAL Biology Edexcel Unit 6 JUNE 2018 official forum

Original post by Studypro2012

Even though it was provided in the paper

What did they say exactly? I always read things quickly and end up losing the most important details...
And how many marks was that very first question again? Was it 5?

(edited 5 years ago)

Reply 81

Screw edexcel

3

Original post by zoae

What did they say exactly? I always read things quickly and end up losing the most important details...
And how many marks was that very first question again? Was it 5?

The question mentioned that the abdomen of the locust contract and relax when they breathe, i think there’s one more statement but i forgot and yes it worth 5 marks

Reply 82

username3159712

12

Original post by Screw edexcel

The question mentioned that the abdomen of the locust contract and relax when they breathe, i think there’s one more statement but i forgot and yes it worth 5 marks

I'm so mad at me for not noticing that! Oh well then respirometer squad is screwed.
Maybe we'll still get 2 or 3 marks for allowing to acclimatise, controlling temperature and repeating+means.

Hopefully the boundaries will be low-ish. I can't understand how they could set 37/50 for a* in October 2017 for DCPIP + ecology...

Reply 83

Rockitty99

9

Original post by zoae

I'm so mad at me for not noticing that! Oh well then respirometer squad is screwed.
Maybe we'll still get 2 or 3 marks for allowing to acclimatise, controlling temperature and repeating+means.

Hopefully the boundaries will be low-ish. I can't understand how they could set 37/50 for a* in October 2017 for DCPIP + ecology...

Exactly! That’s really high and October had rather difficult core practicals, plus October’s critical and calculated value question consisted of a negative value, so this paper was way easier than October so I guess grade boundaries would be 42/50 for A* , and yes I’m in the respirometer squad too :frown:

.

But tbh we are still not sure whether it’s spirogram, respirometer or daphnia practical because all seem to answer the question in some way correctly, and students evenly wrote all 3, so I guess they should consider.

Reply 84

username3159712

12

Original post by Rockitty99

Exactly! That’s really high and October had rather difficult core practicals, plus October’s critical and calculated value question consisted of a negative value, so this paper was way easier than October so I guess grade boundaries would be 42/50 for A* , and yes I’m in the respirometer squad too :frown:

.

But tbh we are still not sure whether it’s spirogram, respirometer or daphnia practical because all seem to answer the question in some way correctly, and students evenly wrote all 3, so I guess they should consider.

Ah. I meant it was low. A negative t had already came up in January 2015 and honestly you can see the significant difference from the graph. DCPIP and ecology were quite "standard" practicals, so I considered our paper more difficult...

Out of the three methods, I would say the spirometer is definitely wrong. How would you attach a spirometer to a locust? They don't even breathe through their mouth...

Reply 85

Aiwl

1

But the daphnia method can only measure breathing rate, how about the tidal volume?

Reply 86

Rockitty99

9

Original post by zoae

Ah. I meant it was low. A negative t had already came up in January 2015 and honestly you can see the significant difference from the graph. DCPIP and ecology were quite "standard" practicals, so I considered our paper more difficult...

Out of the three methods, I would say the spirometer is definitely wrong. How would you attach a spirometer to a locust? They don't even breathe through their mouth...

Really? Ah well I only did the June papers from 2010 onwards, and some ones of Jan only (2012, 2016) , so I didn’t know the negative value when I attempted October lol. And DCPIP was actually quite difficult for me to process without an examiner report because all the answers in mark scheme were over the place, but that’s just me lol.

And yeah I thought the same thing too but then how else would you have calculated breath rate? My friend from abroad from the spirogram answerers said that they connected a smaller tube to the locusts and so it’d be able to breath that , i don’t know though

Reply 87

Screw edexcel

3

Original post by Rockitty99

Really? Ah well I only did the June papers from 2010 onwards, and some ones of Jan only (2012, 2016) , so I didn’t know the negative value when I attempted October lol. And DCPIP was actually quite difficult for me to process without an examiner report because all the answers in mark scheme were over the place, but that’s just me lol.

And yeah I thought the same thing too but then how else would you have calculated breath rate? My friend from abroad from the spirogram answerers said that they connected a smaller tube to the locusts and so it’d be able to breath that , i don’t know though

But insects do not breathe through their mouths

Reply 88

username3159712

12

Original post by Aiwl

But the daphnia method can only measure breathing rate, how about the tidal volume?

They did not ask for the tidal volume. Some of us confused ventilation rate as minute ventilation (which would have required the tidal volume), while others, as respiration rate (which would have required O2 analysis). It turns out ventilation rate is a synonym for breathing rate, ie, a measure of how many breaths an organism takes per unit time (although they could have used the proper term that is usually taught...)

Original post by Rockitty99

My friend from abroad from the spirogram answerers said that they connected a smaller tube to the locusts and so it’d be able to breath that , i don’t know though

That's not realistic. Breathing rate is number of contractions divided by time.

What did you put as the abiotic factors to be controlled? Someone mentioned light intensity isn't correct... Why?

Reply 89

sarafdiez

5

I wrote down respirometer for Q1 and now realise counting breaths seems more like the answer. HOWEVER, in the edexcel text books ventilation rate is described as volume per minute so that would require using a respirometer right? What do you guys think?

Anyways I think 2 things might happen now:

-Edexcel realise it was quite confusing and allow both answers
-Respirometer answer rejected which means half of us have it wrong and grade boundaries go down a lot.

Hopefully!

Reply 90

m_a_v

4

what did you guys write for the last question of question 1?

Reply 91

username3159712

12

Original post by sarafdiez

HOWEVER, in the edexcel text books ventilation rate is described as volume per minute so that would require using a respirometer right?!

What textbook is it? Are you sure it's not minute ventilation? I use Pearson SNAB 3rd ed. and it does not mention ventilation rate at all. It just mentions minute ventilation and breathing rate.

Original post by sarafdiez

Anyways I think 2 things might happen now:

-Edexcel realise it was quite confusing and allow both answers
-Respirometer answer rejected which means half of us have it wrong and grade boundaries go down a lot.

Probably neither. At the end of the day, it was only a 5 mark question. At least 3 of those were independent of the method used (acclimatisation, thermostatic method and repeats). The rest of section 1 was independent too. Edexcel might just as well give 0 f.

Original post by QueenMolly

what did you guys write for the last question of question 1?

I came up with:
Increase in temperature -> higher rate of metabolic reactions (including respiration) -> respiration requires oxygen -> oxygen demand increased -> ventilation rate increased.

(edited 5 years ago)

Reply 92

MythicalInventor

4

I refer to the edexcel a2 biology student book and CGP, it says that ventilation rate = tidal volume x frequency of inspiration (which wud be the breathing rate) so i guess ventilation rate is actually the minute ventilation.

Reply 93

MythicalInventor

4

Original post by zoae

I came up with:
Increase in temperature -> higher rate of metabolic reactions (including respiration) -> respiration requires oxygen -> oxygen demand increased -> ventilation rate increased.

Including all that, I also wrote about the ventilation centre in the medulla receiving impulses from chemoreceptors that detect changes in o2 concentration; and then quicker impulses being sent to the muscles involved in breathing,fr it contract faster.

Tht cud go for a point i think

Reply 94

sarafdiez

5

Original post by Inventor_jiha

I refer to the edexcel a2 biology student book and CGP, it says that ventilation rate = tidal volume x frequency of inspiration (which wud be the breathing rate) so i guess ventilation rate is actually the minute ventilation.

Yes, exactly, and it is the official edexcel book. (not SNAB though)
Most places I looked up on the internet also agree it is volume per minute.

Reply 95

sarafdiez

5

Original post by Inventor_jiha

Including all that, I also wrote about the ventilation centre in the medulla receiving impulses from chemoreceptors that detect changes in o2 concentration; and then quicker impulses being sent to the muscles involved in breathing,fr it contract faster.

Tht cud go for a point i think

I said this too, talked about sympathetic nerves and impulses to effectors (abdominal muscles). Also mentioned higher metabolic rate and increased heart rate because of temperature so more gas exchange.

Reply 96

username3159712

12

Original post by sarafdiez

I said this too, talked about sympathetic nerves and impulses to effectors (abdominal muscles). Also mentioned higher metabolic rate and increased heart rate because of temperature so more gas exchange.

Yeah increase in BMR is important too I think.

Original post by Inventor_jiha

Including all that, I also wrote about the ventilation centre in the medulla receiving impulses from chemoreceptors that detect changes in o2 concentration; and then quicker impulses being sent to the muscles involved in breathing,fr it contract faster.

Tht cud go for a point i think

I'm not sure. I wrote that it was controlled by the brain, period. Insects probably don't have all that.

Original post by Inventor_jiha

I refer to the edexcel a2 biology student book and CGP, it says that ventilation rate = tidal volume x frequency of inspiration (which wud be the breathing rate) so i guess ventilation rate is actually the minute ventilation.

Really!? Well then it's really ambiguous.
You would need to do both the respirometer AND the counting of breathing... For 5 marks, this doesn't feel right.

(edited 5 years ago)

Reply 97

Rockitty99

9

Original post by Inventor_jiha

Including all that, I also wrote about the ventilation centre in the medulla receiving impulses from chemoreceptors that detect changes in o2 concentration; and then quicker impulses being sent to the muscles involved in breathing,fr it contract faster.

Tht cud go for a point i think

Oh man I forgot to write all that, I wrote more kinetic energy due to increased temperature so more substrate-active site collisions, so metabolism increases causing an increase in respiration rate, which means more CO2 pumped out and more ATP generated, as well as higher breathing rate so minute ventilation is tidal vol x breathing rate, thus higher minute ventilation. I don’t know if this qualifies or not :frown:

Original post by sarafdiez

Anyways I think 2 things might happen now:

-Edexcel realise it was quite confusing and allow both answers
-Respirometer answer rejected which means half of us have it wrong and grade boundaries go down a lot.

I really think that should happen, but first one prolly won’t because spirometer answers were quite frequent too, other questions were also very easy of this paper compared to others so grade boundary must be high, but I might be too pessimistic here haha

Original post by zoae

What did you put as the abiotic factors to be controlled? Someone mentioned light intensity isn't correct... Why?

I used respirometer so I wrote
-volume of soda lime
-pH Levels,
Then proceeded to say pH can be controlled by buffer, and if too high it messes with the enzyme active site shape and so minute ventilation decreases.

(edited 5 years ago)

Reply 98

Rush27

8

Original post by Screw edexcel

The question mentioned that the abdomen of the locust contract and relax when they breathe, i think there’s one more statement but i forgot and yes it worth 5 marks