A level Biology: Post your doubts here!

[andreiaafonso14]

Hey, can anyone explain sympatric speciation in simple terms to me?

 

[omarjaved619]

Not exactly, but yes, you should generally have your basic AS concepts clear.
Did you give paper 5?

Yeah I did 52. It was alriiiiight honestly. Q1 was unexpected. Q2 was good I think. So yeah.

 

[xXGTZXx]

Hey, can anyone explain sympatric speciation in simple terms to me?

Sympatric speciation is when a new species is born form an orginal species while the are in the same geographically area. This happens for a variety of reasons, a mutation can cause a change in look, behaviour or smell that is unatractive to the original species, thus they cannot find a mate and cannot mate within the original species but they can find a mate with those who have the same mutattion. They mate with each other and pass on their genes to their offspring after, contiual spertation due to their cahange and breeding with indivuduals with similar changes their DNA changes just enough for them to be considered a same species ie, they cannot interbreed with other original species. They are now considered a new species.

Sympatric speciation may also occur due to polyplodis (i am copying the following from my previous anw)

Polyploids is when the chromosome number of an organism increase to more than 2n, if the it is an odd no. eg 3n, 5n they are infertile as they cannot undergo meiosis as homologous paring of chromosomes cannot take place. If it is even then homologous paring can take place and therefore they are fertile
Hybridization is when two gametes of different species are allowed to fuse together to form an offspring eg, is a mule it is formed from a horse and a donkey. Hybridized organism are usually show more better characteristics of both the parents the mule shows both the characteristics of the horse and donkey

Hybridized individuals are always infertile as they cannot undergo meiosis, but sometimes during the formation of gametes they skip meiosis and the gametes have 2 sets of chromosomes ie, 2n. if two individuals who undergo this faulty division mate the resulting offspring is polyploids

 

[andreiaafonso14]

Sympatric speciation is when a new species is born form an orginal species while the are in the same geographically area. This happens for a variety of reasons, a mutation can cause a change in look, behaviour or smell that is unatractive to the original species, thus they cannot find a mate and cannot mate within the original species but they can find a mate with those who have the same mutattion. They mate with each other and pass on their genes to their offspring after, contiual spertation due to their cahange and breeding with indivuduals with similar changes their DNA changes just enough for them to be considered a same species ie, they cannot interbreed with other original species. They are now considered a new species.

Sympatric speciation may also occur due to polyplodis (i am copying the following from my previous anw)
Polyploids is when the chromosome number of an organism increase to more than 2n, if the it is an odd no. eg 3n, 5n they are infertile as they cannot undergo meiosis as homologous paring of chromosomes cannot take place. If it is even then homologous paring can take place and therefore they are fertile
Hybridization is when two gametes of different species are allowed to fuse together to form an offspring eg, is a mule it is formed from a horse and a donkey. Hybridized organism are usually show more better characteristics of both the parents the mule shows both the characteristics of the horse and donkey

Hybridized individuals are always infertile as they cannot undergo meiosis, but sometimes during the formation of gametes they skip meiosis and the gametes have 2 sets of chromosomes ie, 2n. if two individuals who undergo this faulty division mate the resulting offspring is polyploids

Thank you so much, that was very helpful!

 

[MissBellum]

mine was variant 2...it was decent, not as expected..yours?

i think it was a good a paper, but the end of question 1 was a little tricky

 

[MissBellum]

Yeah I did 52. It was alriiiiight honestly. Q1 was unexpected. Q2 was good I think. So yeah.

yeah me too, i found the end of question one tricky , but overall it was good

 

[MissBellum]

mine was variant 2...it was decent, not as expected..yours?

btw mine was varient 2 aswell

 

[BeBeskii108]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_11.pdf

Q14?? sum1 plz explain

D. B seems correct but D is the right answer. They both have lower water potential but that does not show how they are being differentiated so A is not. B makes a difference but plant cell sap can never have same water potential as fresh water as cells contain many organnelles and metabolites. Plants cells are permeable to water but just controls. So D is the correct answer. I forgot how they control water intake.

 

[Gummy Beat]

This
[PA] explain how the anatomy and physiology of the leaves of C4 plants such as maize or
sorghum are adapted for high rates of carbon fixation at high temperatures in terms of:
• the high optimum temperatures of the enzymes involved
• the spatial separation of initial carbon fixation from the light-dependent stage
(biochemical details of the C4 pathway are not required);
And
outline the following examples of crop improvement by genetic modification and include any
associated detrimental effects on the environment or economy:
• herbicide-resistant oil seed rape
• insect-resistant maize and cotton
Someone plz Explain this : S

 

[bubbles1997]

Aoa. please post guess paper for biology practical 33 here:
https://www.xtremepapers.com/community/threads/as-biology-practical-33-guess-paper-2014.33611/

 

[roxylara]

Guys can any of you please show me and example of a High power plan diagram where we have to draw all cells?!

 

[moonangel996]

HELLO EVERYONE IF YOU ARE AN A-LEVEL STUDENT (A2) READ THIS PLEASE !!!!!!!! IS THIS IN OUR SYLLABUS ?? ABOUT THE ACTION OF GLUCAGON ON LIVER CELLS IN REGULATION OF BLOOD ?????? !!!!!!
1. glucagon binds to receptors in cell surface membrane of liver cell
2. receptor changes conformation
3. G-protein activated
4. adenylate cyclase activated
5. ATP converted to cyclic AMP or cyclic AMP made
6. cyclic AMP is second messenger
7. cyclic AMP activates kinase protein
8. enzyme cascade
9. glycogen phosphorylase
10. glycogen broken to glucose
11. glucose, diffuses and passes out of liver cell into the blood
12. through GLUT2 transporter proteins
13. stimulating gluconeogenesis
PLEASE HELP !!!

 

[ruler_of_the_world]

HELLO EVERYONE IF YOU ARE AN A-LEVEL STUDENT (A2) READ THIS PLEASE !!!!!!!! IS THIS IN OUR SYLLABUS ?? ABOUT THE ACTION OF GLUCAGON ON LIVER CELLS IN REGULATION OF BLOOD ?????? !!!!!!
1. glucagon binds to receptors in cell surface membrane of liver cell
2. receptor changes conformation
3. G-protein activated
4. adenylate cyclase activated
5. ATP converted to cyclic AMP or cyclic AMP made
6. cyclic AMP is second messenger
7. cyclic AMP activates kinase protein
8. enzyme cascade
9. glycogen phosphorylase
10. glycogen broken to glucose
11. glucose, diffuses and passes out of liver cell into the blood
12. through GLUT2 transporter proteins
13. stimulating gluconeogenesis
PLEASE HELP !!!

No, only the action of insulin is required.

 

[ruler_of_the_world]

can someone please explain independant assortment to me.

 

[moonangel996]

No, only the action of insulin is required.

R u sure ??? cuz its there in the 3rd edition textbook (2013 text book )

 

[SOTZAIDI]

The threshold for 42 will InshaAllah be low that's all !!!!

 

[Malik777]

The threshold for 42 will InshaAllah be low that's all !!!!

https://www.xtremepapers.com/community/threads/bio-paper-42.33637/

 

[Rameen Haider]

Practical helppp P33 -- what to learnn - any idea whats coming up ?x

 

[hela]

How was 42 paper biology
Is it difficult

 

[hela]

How was 42 please. Is it difficult