Edexcel 6BIO2 ~ 3rd June 2013 ~ AS Biology

Original post by Tha Realest

Yeah - the pollen tube secretes enzymes = which digest the style tissue .

... Which is then used as nutrition/food for the pollen tube to grow further...

Thanks dude :smile:

Reply 941

Original post by Branny101

... Which is then used as nutrition/food for the pollen tube to grow further...

Thanks dude :smile:

No Problem Mate - glad to help :biggrin:

Reply 942

diggy

Where do, find critical evaluation in The cgp or Anand book

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Reply 943

Original post by Tha Realest

No Problem Mate - glad to help :biggrin:

Then I got another question for yous (XD). Okay so this is taken from the SNAB revision guide but take a look see at part c), the ms says sample site 3 but why is this ? ImageUploadedByStudent Room1370083128.873399.jpg

ImageUploadedByStudent Room1370083128.873399.jpg

(edited 10 years ago)

Reply 944

Original post by Branny101

Then I got another question for yous (XD). Okay so this is taken from the SNAB revision guide but take a look see at part c), the ms says sample site 4 but why is this ? ImageUploadedByStudent Room1370083128.873399.jpg

The mark scheme says site 3 ...

Because it's total number of individuals of all species divided by number of species. :bigsmile:

Reply 945

Original post by Tha Realest

The mark scheme says site 3 ...

Because it's total number of individuals of all species divided by number of species. :bigsmile:

Typo.

And ahh okay :smile:

ty

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Reply 946

mynameisntbobk

Original post by 344302

Is staining your clothes a safety risk haha??

Just wondering

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nope, you could talk about the acid/alcohol you used as well being irritant..

Original post by Kurraiyo

Can someone help me with this question (jan 2010 question 3 c)

-Describe how you could use a plant tissue culture technique to show which of the two tissues is totipotent. (You have two tissues: A and B)

Mark scheme:

1. ref to {sample / explants} from both (tissues): what are explants?

2. ref to aseptic conditions / named example ; would covering the tubes with cling film and not opening them again be okay here?

3. grow cells into a callus / eq ; what is a callus?

4. ref to growth regulators / eq ; what are these?

5. ref to {cells / tissue} can differentiate / cells can
become {whole plants / eq} ;

6. ref to details of procedure e.g. agar / leave
for a suitable length of time / suitable
controlled variable ;

please help me with those four points up there ! :smile:

explants are parts of plants that that have come from an original parent plant with their cotylydons still intact.

I don't believe it would since its not really an asceptic technique.. but then a gain, its really up to the examiner

not sure what a callus is

I believe they're substances that control the gowth of a plant

(edited 10 years ago)

Reply 947

Original post by Branny101

shudn't it be site 1?

Reply 948

Original post by mynameisntbobk

nope, you could talk about the acid/alcohol you used as well being irritant..

explants are parts of plants that that have come from an original parent plant with their cotylydons still intact.

no it wouldn't be okay, if you open it, you risk contaminating the experiment

not sure what a callus is

I believe they're substances that control the gowth of a plant

I believe a "callus" is a cluster of unspecialised plant cells?

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Reply 949

Original post by Daniel Atieh

shudn't it be site 1?

Site 3
Because it's the total number of individuals of all species divided by the number of species .

Reply 950

Rubyturner94

a callus is a mass of undiffrentiated cells, so the explant divides my mitosis and forms a callus.

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Reply 951

Original post by Rubyturner94

a callus is a mass of undiffrentiated cells, so the explant divides my mitosis and forms a callus.

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Thought so :biggrin:

(edited 10 years ago)

Reply 952

Original post by Tha Realest

Site 3
Because it's the total number of individuals of all species divided by the number of species .

By definition ... species richness is the number of different species in an area

Reply 953

Original post by Daniel Atieh

By definition ... species richness is the number of different species in an area

The question was in regards to part c) - "population density", not, species richness :smile:

Reply 954

Original post by Branny101

The question was in regards to part c) - "population density", not, species richness :smile:

haha i was like wth .... why am not understanding the concepts lol....

Reply 955

Original post by Daniel Atieh

By definition ... species richness is the number of different species in an area

What I am not sure of is ...

The answer is site 3 because

1) highest total number of individuals of all species and site 3 has 8000

or

2) 8000 / 1 = 8000

I think it's because of answer (2) ... Would that be right ??

(edited 10 years ago)

Reply 956

Original post by Daniel Atieh

haha i was like wth .... why am not understanding the concepts lol....

Lol I could see aha that's was like I'd help out the conversation :wink:

Reply 957

VALID vs. RELIABLE ?????????????????????????????

Reply 958

LivDoesBiology

Original post by Daniel Atieh

Also i want answers for these:
Q) Define Sustainability
Q) WHat is the difference between cellulose molecule and cellulose microfibrils ( 4 points )

cellulose microfibrils are formed by the cellulose molecules in the cell walls. They are layed down in layers held together by a matrix of hemicelluloses.
A cellulose molecule is made of beta glucose molecules held together by glycosidic bonds which are formed in condensation reactions.

Reply 959

That_Clever_Guy

Original post by Daniel Atieh

VALID vs. RELIABLE ?????????????????????????????

Valid is all about a fair test reducing uncertainties etc using control variables such as light temperature in the nitrate experiment :wink:

reliability is all about repeats and that if you repeated the experiment under the same conditions that you would get the same results and find the same observations hope that makes sense :wink: