Edexcel AS Biology Unit 2 (6BIO2) - 26/0/2011- OFFICIAL THREAD !

Original post by NatB28

Well Done

How does a tumour develop? (5 marks)

Tumour develops by uncontrolled cell divison
where a mass of cancerous cells are produced
DNA becomes damaged
Tumour suspressor gene become inactive due to mutation
further cell division takes

Reply 82

how do you measure the inhibition zone around the lawn of bacteria

Reply 83

Original post by voices1

Tumour develops by uncontrolled cell divison
where a mass of cancerous cells are produced
DNA becomes damaged
Tumour suspressor gene become inactive due to mutation
further cell division takes

That's really good you know your stuff. :smile:

I would say the exactly the same, if the question is for even more marks. I would mention proto-oncognees have to be mutated to oncogones (as well as TSG) to cause cancer

Reply 84

Nat cud u answer my previous 2 post please

Reply 85

bertiejess

Original post by voices1

GOT question need your help

for continuous variation can you have a chart of bars touching each other not seperate bars but touching

What is difference between tissues and organ

Tissues are made up of several cells, in order to perform a specific function by working together, e.g muscle tissue
Organs are made up of several types of tissue, in order to perform a specific function, e.g the heart

Reply 86

Original post by voices1

how do you measure the inhibition zone around the lawn of bacteria

I'm not sure if I should include the practical describtion I will. Just mention it for the fun of it.

Created bacterial lawn in a petri dish containing agar
Use aspeptic /sterile techniques eg flame neck bottles, autoclaved etc
Use single strain of bacteria
Filter paper discs - (soaked in extract plus ethanol)
Placed on seeded agar lawn
Incubate for 24 hours at 25 degrees C
Measure inhibition zones (clear zones) diameter (if not round, lots of measurements work out mean)
Largest zone = most effective
I wouldn't remove the lid to measure (safety)
Control = pure ethanol
3+ repeats

I'm not sure on this pratical please give me the correct answer, thank-you

Reply 87

Original post by bertiejess

Tissues are made up of several cells, in order to perform a specific function by working together, e.g muscle tissue
Organs are made up of several types of tissue, in order to perform a specific function, e.g the heart

I would just add

Tissues made up of similar cells (similar origin)
Organs obviously contain different cells as made up of diff tissues.

Reply 88

yep its correct
thanks
4 continuous variation do you get bars attached to each other
i know discon is seperate bars

Reply 89

Original post by Nator

1) Genetic diversity is the number of different alleles in a species, within a gene pool. I don't know how you would go about measuring it, perhaps a quadrat?

2) Biodiversity is the number of different living organisms in a habitat.

3) An endemic species is one that is subject to only one environment, i.e. it is found only in one place.

:smile:

I forgot to mention for biodiversity youn include genetic diversity and well as species richness (what you mentioned)

You measure genetic diversity by the heterozygousity index (sorry about the spelling I'm dyslexic)

Reply 90

Original post by NatB28

I would just add

Tissues made up of similar cells (similar origin)
Organs obviously contain different cells as made up of diff tissues.

do tissues carry out many functions?
dO ORGans carry out one specific function

Reply 91

aggie30

Original post by NatB28

I'm not sure if I should include the practical describtion I will. Just mention it for the fun of it.

Created bacterial lawn in a petri dish containing agar
Use aspeptic /sterile techniques eg flame neck bottles, autoclaved etc
Use single strain of bacteria
Filter paper discs - (soaked in extract plus ethanol)
Placed on seeded agar lawn
Incubate for 24 hours at 25 degrees C
Measure inhibition zones (clear zones) diameter (if not round, lots of measurements work out mean)
Largest zone = most effective
I wouldn't remove the lid to measure (safety)
Control = pure ethanol
3+ repeats

I'm not sure on this pratical please give me the correct answer, thank-you

could you explain the points for the totipotent experiment we never actually did it in class thanks

Reply 92

Original post by voices1

yep its correct
thanks
4 continuous variation do you get bars attached to each other
i know discon is seperate bars

Yes, they can be next to each other can you can draw a histogram for continuous (I believe)

Reply 93

aggie30

does any one know what core practical is most likely to come up plus other topics that may come up as well so i can focus my revision on them

Reply 94

RosePetal

11

Original post by Nator

1) Genetic diversity is the number of different alleles in a species, within a gene pool. I don't know how you would go about measuring it, perhaps a quadrat?

2) Biodiversity is the number of different living organisms in a habitat.

3) An endemic species is one that is subject to only one environment, i.e. it is found only in one place.

:smile:

For measuring genetic diversity you look at the phenotypes and the genotypes - analysing the DNA.
For species diveristy you can use sampling - e.g. using quadrants.
Just wanted to point that out.

Reply 95

Original post by NatB28

Yes, they can be next to each other can you can draw a histogram for continuous (I believe)

cheers mate
im a correct in saying that organs carry out ONE specific function, whereas tissues carry out many

Reply 96

Original post by voices1

do tissues carry out many functions?
dO ORGans carry out one specific function

Tissues can only carry out one function, organs can carry out one or more functions (but they have an overall main "particular" function). Does that make sense

This is according to edexcel anyway. That tissues have one function (from past exam papers) and organs can have more than one. The clegg text book says that too in the glossary

(edited 12 years ago)

Reply 97

Original post by RosePetal

For measuring genetic diversity you look at the phenotypes and the genotypes - analysing the DNA.
For species diveristy you can use sampling - e.g. using quadrants.
Just wanted to point that out.

For genetic measure the number of alleles that code for same characteristic

Reply 98

Machimbawe

they normally ask for bars in bar charts to be drawn about o.5cm apart in discontinues but i am not really sure what they ask for in continous. anywat they dont normally ask for a chart to be drawn in unit 2 do they ?

-What are stem cells?
-What are the disadvantages and advantages of the use of stem cells (embryonic, adult and ennucleated)?
-What are stem cells used for ?

Reply 99