Edexcel A2 Biology exams (6BIO4) 25th January 2012 exam discussion

Reply 580

.snowflake.

14

Original post by SLlewellyn

What questions on the paper are you referring to - I've got my answers but not sure which one you're referring to.

the T lymphocytes and the antibiotics one.

Reply 581

Crushy

Anyone know what is meant my 'compensation point' when describing light as a limiting factor? (Specifically in reference to june 10 3biii)

Reply 582

This Honest

3

Original post by Bright

Haha!! guys.... :P

I really hope we get A*'s for this man! :frown:

just hope the questions are do-able/easy

Original post by .snowflake.

Those two Q's narked me as well. Impressively the title page for one of the 2010 papers read as the following
GCE Biology
Advanced Subsiduary
Unit 4.

IIRC, Unit four is Advanced level!!

ahh edexcel :rolleyes:

Reply 583

This Honest

3

Original post by Crushy

Anyone know what is meant my 'compensation point' when describing light as a limiting factor? (Specifically in reference to june 10 3biii)

i think this is when the rate of photosynthesis and the rate of respiration are equal.
Darn! This is in my bio coursework though :danceboy:

Reply 584

Crushy

Original post by This Honest

i think this is when the rate of photosynthesis and the rate of respiration are equal.
Darn! This is in my bio coursework though :danceboy:

Okay, so above that point 'net' photosynthesis takes place because there's more energy coming in via photosynthesis than going out via respiration. Thanks.

Reply 585

Bekah93

Hi I don't know if it's already been asked, but could someone explain spec point 22 please? 'Explain how reproductive isolation leads to speciation'?

Reply 586

.snowflake.

14

Original post by Bekah93

Hi I don't know if it's already been asked, but could someone explain spec point 22 please? 'Explain how reproductive isolation leads to speciation'?

its covered on pages 60-61 in the SNAB textbook (the orange one) and page 16-17 in the revision guide.

I will explain it later, im currently in the middle of writing notes about the core practicals.

(edited 12 years ago)

Reply 587

avataraang

6

Original post by Bekah93

Hi I don't know if it's already been asked, but could someone explain spec point 22 please? 'Explain how reproductive isolation leads to speciation'?

Reproductive isolation leads to speciation because...

1) Random mutations occur that increases the genetic diversity of the gene pool
2) Populations can be seperated into smaller groups, maybe due to something like a natural disaster, geographical barrier etc.
3) Selection pressure of new environments (e.g. climate) will increase the chances of those organisms who have the advantageous alleles to adapt to this new climate to reproduce and give fertile offspring.
4) Allele frequency for this mutation increases
5) Restricted gene flow within the populations means that mutations can be easily inherited leading to changes in phenotype (making it not possible to interbreed with other population group)
6) Hence reprodutive isolation leads to speciation

Hope that helps :biggrin:

Reply 588

avataraang

6

By the way the specification states that "explain the concept of niches accounts for the abundance and distribution of organisms in a habitat"

:s-smilie:

Help me please!

Reply 589

This Honest

3

Original post by Crushy

Okay, so above that point 'net' photosynthesis takes place because there's more energy coming in via photosynthesis than going out via respiration. Thanks.

Reply 590

d_94

7

2 days to go :/ :/ Aghh. I really just want to get it over with and have my winter break!!

Reply 591

This Honest

3

Original post by avataraang

By the way the specification states that "explain the concept of niches accounts for the abundance and distribution of organisms in a habitat"

:s-smilie:

Help me please!

niche is the role of a species in a habitat
I'm sure you're aware that 2 different organims cannot occupy the same niche.
When 2 occupy the same niche, one will have slightly better adaptions which will give that organism a selective advantage over the other organism.
So the other organism will be out-competed and will be immigrated/distributed from that niche to another one
So, as they get out-competed, the "better" organism will survive, breed and reproduce and will increase in population size, hence become moe abundant.
:smile:

Reply 592

avataraang

6

Original post by This Honest

niche is the role of a species in a habitat
I'm sure you're aware that 2 different organims cannot occupy the same niche.
When 2 occupy the same niche, one will have slightly better adaptions which will give that organism a selective advantage over the other organism.
So the other organism will be out-competed and will be immigrated/distributed from that niche to another one
So, as they get out-competed, the "better" organism will survive, breed and reproduce and will increase in population size, hence become moe abundant.
:smile:

Ahhh... I see. So that is basically the same as AS topic 4 then really. Thanks for the reminder

Reply 593

wam-bam

1

Original post by Bekah93

x

Original post by .snowflake.

x

Original post by avataraang

x

i posted this earlier its every point on the specification explained

http://www.thestudentroom.co.uk/showthread.php?p=35958620&highlight=awsome%20specification%20specific%20notes%20 :biggrin:

hope it helps!

Reply 594

This Honest

3

Original post by avataraang

Ahhh... I see. So that is basically the same as AS topic 4 then really. Thanks for the reminder

yeah something like that
remember unit 4 is synoptic :sigh:

Reply 595

wam-bam

1

Original post by This Honest

.

Okay i'm a tad confused please can you explain.... i don't understand why the antibiotic needs to be changed for treatment when the one's used for identification (Enrofloxacin & Florfenicol) are the most effective???

i've attached the Q and MS (it's 2a.iii form Jan 11)

thanks

Original post by This Honest

yeah something like that
remember unit 4 is synoptic :sigh:

Ugh... yeah I know :frown:

By the way do u happen to know any ethical issues about using brine shrimp? I have a feeling that this might come up :O

Reply 597

This Honest

3

Original post by wam-bam

Okay i'm a tad confused please can you explain.... i don't understand why the antibiotic needs to be changed for treatment when the one's used for identification (Enrofloxacin & Florfenicol) are the most effective???

i've attached the Q and MS (it's 2a.iii form Jan 11)

thanks

hey

ok, so if you use many antibiotics to treat an infection depite knowing which anitgen is causing it, then you are just going to increase the general resistance of bacteria and soon the bacteria will be completely resistant to that antibiotic
As soon as we know which antigen is causing the infection, we resort to narrow-spectrum antibiotic/specfic antibiotic because as the MS says, it is more effective because it can form antigen-antibody complexes effectively.
Also, if we contiune to use many antibiotics for one infection, different strains of bacteria may evolve which means they are mutated and they will be resistant to specific antibiotics which we don't want :no:

Reply 598

This Honest

3

Original post by avataraang

Ugh... yeah I know :frown:

By the way do u happen to know any ethical issues about using brine shrimp? I have a feeling that this might come up :O

again the ethical issues are related to unit 1 bio
remember the daphnia exp.?

Well, I'm going to use the same ethical issues for daphnias and with brime shrimps

so ethical issues:
brime shrimps can't give consent
subjected to painful procedures
high temperatures
they are living creaturs, not fair/ethical to play with their lives
animal rights

Reply 599

This Honest

3

Will come back online in 20mins, gonna read a bit

Edexcel A2 Biology exams (6BIO4) 25th January 2012 exam discussion

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