[YazB7]

(Original post by Dorkins)
What do you want to know?

Taxonomic hierarchy:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species

- As you go down the list, the number of species in each category decreases; but the similarity between organisms increases.

Names of species:
- Genus + Species
- eg:

• Orcytolagus cuniculus
• Genus: Orcytolagus
• Species: cuniculus

Thanks but I genuinely don't understand any of it

[Tikara]

(Original post by YazB7)
Thanks but I genuinely don't understand any of it

Khan Academy does a good video on taxonomy - It's basically just latin words that classify organisms by different features.

link: http://www.youtube.com/watch?v=oHvLlS_Sc54

[YazB7]

(Original post by Tikara)
Khan Academy does a good video on taxonomy

Thank you so much x

[choccandy21]

(Original post by Tikara)
So when would DNA mass half in the cell? - after cytokinesis?

Yes cytokinesis/telophase/during mitosis. I don't think we need to know the details of both cytokinesis and telophase. Just class them as one- when a nuclear membrane forms making 2 nuclei.

[Tikara]

(Original post by halii_94)
Yes cytokinesis/telophase/during mitosis. I don't think we need to know the details of both cytokinesis and telophase. Just class them as one- when a nuclear membrane forms making 2 nuclei.

Yeah, okay thanks very much

When the spindle fibres shorten and pull the sister chromatids to opposite poles, is each chromatid now called a chromosome? and are the 2 chromatids together collectively a chromosome? darn it this is confusing xD

[choccandy21]

(Original post by Tikara)
Yeah, okay thanks very much

When the spindle fibres shorten and pull the sister chromatids to opposite poles, is each chromatid now called a chromosome? and are the 2 chromatids together collectively a chromosome? darn it this is confusing xD

It is very confusing I agree! Ha
Just say The chromosome divides in two and each sister chromatid moves to opposite poles of the cell like you memtioned
I think they are called chromatids when at opposite poles but when the cell divides and two new nuclei are formed they are then called chromosomes..I think..haha

[rommy123]

Can someone explain genetic bottlenecks and the founder effect, really dont understand any of it

[Hamzi]

(Original post by halii_94)
It is very confusing I agree! Ha
Just say The chromosome divides in two and each sister chromatid moves to opposite poles of the cell like you memtioned
I think they are called chromatids when at opposite poles but when the cell divides and two new nuclei are formed they are then called chromosomes..I think..haha

They are called chromosomes when a nuclear envelope develops around them at telophase.

[Hamzi]

(Original post by rommy123)
Can someone explain genetic bottlenecks and the founder effect, really dont understand any of it

Genetic bottleneck:
When a chance event such as volcanic eruption or human inteference causes a massive reduction in the population of species living in an area. This means that the diversity of alleles in the population is reduced so the genetic diversity, which is the variety of alleles in a population, is reduced.

Founder Effect:
When a proportion of a population migrate and colonise a new place. They carry only a proportion of the alleles of the intial population so thats how there genetic diversity is reduced. When they reproduce, these alleles are passed on so it remains low even when the population is increasing. The way the variety of alleles can increase in this population is if they reproduce with the local version of their own species.

[starfish232]

(Original post by rommy123)
Can someone explain genetic bottlenecks and the founder effect, really dont understand any of it

Founder effect

• A small number of individuals from the original population move and settle in another area.
• This groups has less variation in alleles compared to original population
• When the individuals reproduce and the a whole population developed over time, there's a reduced amount of alleles present in the population as the individuals they've derived from had small amount of different alleles.
• As a result, this new population has less genetic diversity than the original population.

Genetic Bottlenecks
A natural disaster or an event that happens resulting in the most of the population of a species dying.
There are few survivors and there's reduced amount of different alleles in this group. As a result, when the individuals reproduce and and slowly replace the population lost, overall the population has limited number of varied alleles compared to the original population. So the new population has less genetic diveristy compared to the original population.

I think that's it really and I hope this helps you. If not then I'm sorry about that.

[bad8oy]

can someone please post the paper and markscheme for january 2012 unit 2 biology. Thanks i would be very much appreciated.

[Tikara]

(Original post by bad8oy)
can someone please post the paper and markscheme for january 2012 unit 2 biology. Thanks i would be very grateful.

Here you go
AQA-BIOL2-W-QP-JAN12.pdf

AQA-BIOL2-W-MS-JAN12.pdf

[Hamzi]

Can someone give me features and explanations of cellulose, glycogen and starch.

How is index diversity better than just counting the number of species?(2 marks)

Is it because it takes into account the total number of all species within a population which can help to see if one species is in a greater proportion than the others.

[nasira372]

can any1 help with 2dii please

http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF

dont understand the answer

[bad8oy]

(Original post by Tikara)
Here you go
AQA-BIOL2-W-QP-JAN12.pdf

AQA-BIOL2-W-MS-JAN12.pdf

thank you i give u +

[Hamzi]

Can someone explain how the insects gas exchange system is efficient?

[Hamzi]

(Original post by nasira372)
can any1 help with 2dii please

http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF

dont understand the answer

The rate of blood flow is slow in the capillaries because there is greater friction/resitance to the blood flow so it allows time for substances to diffuse in and out of the blood.

[britash]

Hey. Can someone please explain question 7(c) on January 2012 paper?
(I can write it out if you need me to..)

[Tikara]

(Original post by nasira372)
can any1 help with 2dii please

http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF

dont understand the answer

No, I don't get these blood flow ones either

Mark Scheme says "more time for exchange of substances"

I guess it wants you to say that the lower blood flow means that blood flows slower through the network and therefore has more time to exchange substances.

I always think these aqa biol questions are annoying D:

By blood flow does it mean movement of blood, so more rate of blood flow means quicker the blood moves through the vessel?

[Dorkins]

(Original post by Hamzi)
Can someone give me features and explanations of cellulose, glycogen and starch.

Cellulose:
- Beta Glucose forms long, straight chains. This is why the cell wall is strong.

Starch/Glycogen:
- Alpha Glucose chains.
- Chains are long and branched, so it can easily store a hell of a lot of glucose molecules.
- Chains also form spirals, so they fold up and are very compact.

Starch:
- Found in plant cells.

Glycogen:
- Found in animal cells.
- Forms more branches along a chain, so it is more compact than starch.