AQA Biology B2 - Unofficial Mark Scheme

Scroll to see replies

Reply 520

HarryGCSE

What did you guys put for the stem research questions?

(edited 7 years ago)

Reply 521

JakeHorsey

Original post by afghan-superman

The genotypes was the parents genotypes which were Bb and Bb. You were meant to put the offsprings genotypes in separately. And yes sorry, the gametes were XX and XY

The gametes were as follows: B and b, and B and b. 'Gamete' does not refere to the genetics that determine gender. It refers to the cells (sperm/egg) that are haploid and carry a variated set of 23 single chromosomes, with genes from the mother and the father. In each one, only a single 'B' or 'b' could exist to influence the hair colour - the other would come from the other gamete from the sexual partner.

So yea, gametes are: B / b on both (written separately).

Reply 522

username2642707

Original post by JakeHorsey

Yep, and 'bb' alleles for the offspring basically meant having red hair instead of brown. Making it a 25% chance of having red hair

Reply 523

markschememate

Original post by 11masanda002

how many marks were these questions worth?

One mark each

Reply 524

Reykaif

For The mitosis It didnt double to 13.2. It said that they duplicated so it was stilll 6.6 so they then halved to 3.3 and then to 1.65.

Reply 525

Torres9991

Original post by mmgnaahk123

I have completed the whole mark scheme except for 1 question worth 1 mark. I have also put all the mark allocations on. https://docs.google.com/document/d/1hxWXg_Uv9-TDqFtJndhA5s7OtOUt_u65wxPkTArmwR0/edit?usp=docslist_api

Hey there, have you made the b3 mark scheme?

Reply 526

asox

Original post by ajs12

0.25m^2 = 0.0625
0.0625 * 10 = 0.625 <<<< 0.065 (what you have said as the area of one quadrat) is only 6.25cm squared??? Thats smaller than the sides of the quadrant???
20/0.625 = 32

There are 32 plantains in 10m^2, NOT 1 m^2

5000/10=500
500 * 32 = 16000

Surely the plantain question is this:

Total number of plantain in 10 quadrats: (add them together) = 20 plantains in 10 quadrats

Area of 10 quadrats in metres squared: 1quadrat= 25x25 = 625cm squared
Divide 625 by 100 to get it in metres = 6.25, then times by 10 for ten quadrats= area of ten quadrats is 62.5 metres squared.

Average number of plantains per quadrat = 20 plantains in 10 quadrats so its 20/10 = 2 plantains per quadrat

Area of field = 100 x 50 = 5000 metres squared

Estimated number of plantains in field = the number of metres squared times by the average number of plantains per quadrat = 5000 x 2 = 10 000 plantains

Even if you got a different value for the total number of plantains in 10 quadrats you could still do the mean number of plantains per quadrat x area of field...

Is this right? It's so confusing...

Reply 527

ajs12

Original post by asox

In the great scheme of things this all now seems somewhat insignificant, I think I also made a few more corrections later on, but 625 cm^2 is not 6.25m^2, its 0.0625m^2... according to Google, because you're working with areas not lengths you don't divide by 100 but instead 100^2, which is 10000

Reply 528

goldenusername

Original post by Reykaif

For The mitosis It didnt double to 13.2. It said that they duplicated so it was stilll 6.6 so they then halved to 3.3 and then to 1.65.

thats what i got too

Reply 529

asox

Original post by ajs12

http://prntscr.com/bffiyk
???^

edit// ohhh i get you

(edited 7 years ago)

Reply 530

miapeters

Original post by Dauntless27

So you didn't mention anything about fatigue or lactic acid either? Do you think we will get the marks?

noo not at all - i thought we'd get points for:
-(smaller surface area so) less oxygen diffuses from air to alveoli
-less oxygen delivered to cells so
-less respiration happens, so less energy is released and they find it difficult to exercise

reading all the other comments ha made me think this is wrong thoughh

Reply 531

tianshan

For Question 7, didn't they say Cell A has 6.6? So Cell B must have 13.2 after DNA replication, Cell C should be 6.6 and the gametes at the bottom with 3.3 each. A normal cell has 6.6. Correct me if I'm wrong.

Reply 532

tianshan

Original post by Reykaif

For The mitosis It didnt double to 13.2. It said that they duplicated so it was stilll 6.6 so they then halved to 3.3 and then to 1.65.

Duplication still means making a copy of all of its DNA, so 6.6 becomes 13.2 after the first stage (DNA replication). The gametes' DNA would combine to become 6.6, like a normal cell (same as Cell A). This means each gamete has DNA of 3.3 pictograms.

Reply 533

samii2100

if u get a u in one paper and a c in the other 2 what grade do you get overall?

Reply 534

guy321

do you think any marks will be awarded for the mass of cells question. I basically lost 5 marks in that question ffs. I forgot that the cell dna duplicates and thus mass would be 13.2. Because i got that wrong I also got the others wrong. But will they allow error carried forward???

also for the hair gametes question it wasn't asking about gender gametes so I didn't put XX and XY. However, lots of people on tsr are saying it was XX and XY