Biology SL/HL help

[iber2011]

oh ok thanks a lot

[Mahuta ♥]

I normally answer in bullet points (even in uni). Instead of writing a long paragraph and missing out things, I would answer in clear straight forward bullet points to ensure I didn't miss anything. Even question asking about the light independent reaction for example, I answered it in bullet points. My teacher (IB examiner) always said it's much easier for the examiner to read a long answer in bullet point than read through a paragraph.

Yes you can draw diagrams like Drake said, but if they said 'explain' I would just write (to be on the safe side). I mean you're doing Biology HL, sure you can know the things and be able to write them all down in the exam!

Something like the Bohr shift? Even though you understand that really well, I would always keep in mind the the diagram with two graphs (for two different partial pressures of CO₂), just a rough diagram. However I wouldn't use that as an answer (though you could) but I just draw it on the draft papers and answer while looking at it.

Like mentioned above, drawing diagrams will guaruntee you the mark if you missed something, but don't rely on diagrams only. I always give my answer (from 2pt to 8pt questions..doesnt matter) written in bullet points then add a diagram at the end.

[iber2011]

Thank you so much! In all my term exams I used to write my answers in paragraphs and my teacher is new to Ib so she didn't tell me.....thank you once again...i'll definitely use your tip in my fianls

[Sandwich]

I normally answer in bullet points (even in uni). Instead of writing a long paragraph and missing out things, I would answer in clear straight forward bullet points to ensure I didn't miss anything. Even question asking about the light independent reaction for example, I answered it in bullet points. My teacher (IB examiner) always said it's much easier for the examiner to read a long answer in bullet point than read through a paragraph.

I don't know how true it is, but in the long answers because 2 of the points are for structure/presentation, our biology teacher told us that we couldn't score those two points unless we wrote it out in full because bullet points aren't considered proper structure/presentation. So in those questions I'd certainly make sure you answer in full sentences to be on the safe side, because those bonus points are stupidly easy to get and you'd kick yourself for missing them!

[Mahuta ♥]

Yeah good point. But by bullet points I don't mean like:

1. Photons excited causing bla bla.

2. Electron moves to bla bla.

It's basically a paragraph written out in bullet points if I am making any sense..

But like I said I agree and our teacher did tell us about that, but he also said "If you are unsure that you can write a long full answer in a paragraph(s) without the info being all over the place, do it in bullet points". To be honest with you, as A2 english student (ex-student), I was more confident giving my answers full in a clear coherent way and not getting the two points than trying to score the 2 points by writing it out as a paragraph. I didn't suck at English, but still wasn't confident enough to risk it. I did try writing an 8 mark question as a paragraph in one exam and in bullet points in another exam. Even though I only scored one point higher in the second one(7 for the first, 8 for the second), my teacher clearly told me "Go for bullet points, it's like they were two exams from completely different people. After all you're still getting 7s"

Anyways, you get my point IBer, Sandwich is absolutely right about the two points but please don't risk giving unclear answers to score the two points. If you are an awesome english student..then definitely take Sandwich's advice.

[iber2011]

Hey thanks you guys and yeah i get what you mean....even though i'm not bad in english...i'll try to write in bullet points but not in short like just breaking the paragraph....thank you again Mahuta and Sandwich i appreciate your help

[timmotytimmoty]

I know this question appeared n-times, but I would like to ask again, because I can't find it in the internet, Where is Syllabus of Biology for IB 2012 May exam? Thank you, and I do appreciate any responses.

[dessskris]

I know this question appeared n-times, but I would like to ask again, because I can't find it in the internet, Where is Syllabus of Biology for IB 2012 May exam? Thank you, and I do appreciate any responses.

You come to the right place! We have it in our Files section. Here you go

[Hinuku]

Ive got this question regarding mitosis. How accurately do I have to know all the stages including G1 S G2 phases. I mean - do I have to write a paragraph on each or simply know that they are there adding one sentence about separation in anaphase for example, leaving out all the info like mitotic spindle or microtubule-organizing center and so on. I have two books and both vary in the strong details as mitosis is a fluent process (doesnt have visible stages). Thus, Im also not sure which to follow. Same goes with meiosis. Its a real issue while learning.

Thank you,

Matt

[Drake Glau]

Well, G1 is just normal cell stuff, make proteins, do it's thing, yada yada. S is where the DNA is replicated. G2 is the same as G1

For the actual mitotic phase you will need to know all 4 stages rather in-depth. If you get a question about the process of mitosis it WILL be an 8-9 point "essay" question, which is as high as they go. Doesn't have to be SUPER in-depth though.

Some thing like:

Centrosomes moves to poles

Nuclear envelope falls apart

chromosomes line up on metaphase plate

micro-tubules from the centrosomes bind to the chromosomes

they pull them apart

cytokinesis happens

nuclear envelope is re-built

2 cells are made

haploid number remains the same

There's probably at least 7 points in that, maybe more if you specifically state which phase these are happening in because you'll probably get one for stating the phase and then another 1-2 for what goes on in it.

[Hinuku]

Well, G1 is just normal cell stuff, make proteins, do it's thing, yada yada. S is where the DNA is replicated. G2 is the same as G1

For the actual mitotic phase you will need to know all 4 stages rather in-depth. If you get a question about the process of mitosis it WILL be an 8-9 point "essay" question, which is as high as they go. Doesn't have to be SUPER in-depth though.

Some thing like:

Centrosomes moves to poles

Nuclear envelope falls apart

chromosomes line up on metaphase plate

micro-tubules from the centrosomes bind to the chromosomes

they pull them apart

cytokinesis happens

nuclear envelope is re-built

2 cells are made

haploid number remains the same

There's probably at least 7 points in that, maybe more if you specifically state which phase these are happening in because you'll probably get one for stating the phase and then another 1-2 for what goes on in it.

Thanks, but what I need is actually more on the G1, S, G2 - I simply cant find the info in the syllabus. Just how much do I need to know about them. And often there are some key words.

[Mahuta ♥]

I can't remember the syllabus very well but if you can't find it in the syllabus then it's not in! Then again I do remember the teacher talking a little but about Interphase.

But if you really want to know, all we were told is this:

G1:

• Cell size increas.
  
• RNA &Protein are synthesized
  
• Basically, making sure everything is ready for DNA synthesis.
  

S:

• DNA replication takes place
  

G2:

• Cell continues t grow in size and the necessary things are checked. If it helps, think about it as a check point on whether the cell is ready to divide.
  

[Hinuku]

Yet another question!

What is the difference between euchromatin and heterochromatin? Are both the same structurally, just one less condensed form of chromatin and the other more chondensed form of the same chromatin? Or is euchromatin an entirely different type of chromatin (e.g. different purpose and different structure)than heterochromatin? And finally, is it then called heterochromatin? And before the condensation all of it was called euchromatin? Or are there always two variants?

[Mahuta ♥]

You absolutely don't have to know that, I only learned those things this year!

If I remember correctly, euchromatin and heterochromatin are two different versions of chromatin. As you know, chromatin is a tightly packed DNA. The main difference between the two is that euchromatin is 'loosely' packed DNA(not very condensed) whereas heterochromatin is tightly packed(highly condense). Think about it as a copper coil that is coiled but very loosely and another coiled very tightly. If you are really curious about them, eucrhomatin (loosely coiled DNA) is more active in terms of transcription.

Here's something that will help picturing it (just look at the top part only):

Once again, this is not in the syllabus and you are not requiredto know it.

[Hinuku]

You absolutely don't have to know that, I only learned those things this year!

If I remember correctly, euchromatin and heterochromatin are two different versions of chromatin. As you know, chromatin is a tightly packed DNA. The main difference between the two is that euchromatin is 'loosely' packed DNA(not very condensed) whereas heterochromatin is tightly packed(highly condense). Think about it as a copper coil that is coiled but very loosely and another coiled very tightly. If you are really curious about them, eucrhomatin (loosely coiled DNA) is more active in terms of transcription.

Here's something that will help picturing it (just look at the top part only):

Once again, this is not in the syllabus and you are not requiredto know it.

OThis was really really helpful actually! Yet another thing is - after compaction of chromosomes in prophase both euchromatin and heterochromatin are more condensed? Am I correct? Because chromatin is what builds a chromosome?

[Mahuta ♥]

The euchromatin and heterochromatin both become very highly condensed during prophase (even before actually, during interphase), however we cannot say they are both the same because they're not. All we can say is that they are both very tightly packed.

[Hinuku]

I have this question, after anaphase I of meiosis, the two cells produced are haploid (since there is just one member of each homologous pair in each cell). How come gametes are also referred to as haploid if they are halved once more? I don't quite agree with what I wrote up there but that's what's in my book. I mean, in my opinion we start with 4n - not diploid, then we move on to 2n or diploid since one member of a tetrad is still a double copy of oneself and finally after anaphase II do we only get a haploid cell. So this is what I think, but in my book, and it's a great book - villee, it's written otherwise.

Or am I wrong in saying that we start with 4n? I mean, these are just paired up chromosomes so the number stays the same doesn't it? We have 23 male and 23 female chromosomes in a zygote. So at the start of prophase I we get 23 homologous pairs or tetrads (or bivalents - why so many names!!) Is that so?

Correct me It's so hard for me to understand this chapter!

Thank you

P.S. Am I required to know about Mendel's work? Not the laws but for example state why his work was so brilliant and lucky, summarise the experiment?

Edited April 17, 2011 by Hinuku

[iber2011]

Wait 4n?? As far as I know it's n+n=2n for humans that is....and gametes are from one parent each so that's why they're called haploid...they're only n.

[Drake Glau]

Wait 4n?? As far as I know it's n+n=2n for humans that is....and gametes are from one parent each so that's why they're called haploid...they're only n.

Both mitosis and meiosis start with 2n...

During Meiosis you have your 2n (homologous chromosomes, 46 in humans) and they line up and split and cytokineses happens and you have 2 cells, each with now 23 homologues. Meiosis 2 happens and the sister chromatids making up the homologues split and you end with 23 actual chromosomes. So you went from 2n in one cell to n in 4 cells.

Edited April 17, 2011 by Drake Glau

[Hinuku]

A cross is carried out between two heterozygous individuals (AaBb) where the genes A and B are not linked genes. What would be the proportions of genotypic recombinants amongst the offspring of this cross?

A. 0%

B. 2%

C. 7%

D. 100%

Does anyone know how to solve this? The answer is 7% as stated by the key.