Edexcel A2 Biology Unit 4 (6BI04) - 15 June 2012 - Official Exam Discussion Thread!!!

Can someone explain peat bogs to me. Still don't fully understand it..

Reply 581

Original post by Stryder402

finding it hard to remember the experiments!

can somebody post up the experiments pls

http://www.thestudentroom.co.uk/show...&page=9&page=9
last post of this link.....hope this helps....

Reply 582

demdil

i am very bad at speciation, does anyone have general points that get marks for speciation? they ask it on each paper and i always get 2 marks maximum from that :O

Reply 583

VRS

Original post by This Honest

Can someone explain peat bogs to me. Still don't fully understand it..

Taking samples deep from the earth (around 1-2.5metres) analysing the seeds, then using the seeds to decide what the climate was like back then. If there were loads of oak seeds (say oaks only grow in a hot climate) then it was hot back then.

Reply 584

Kylewalker346234

12

Original post by cisne

Antisense strand: This serves as a template for the formation of mRNA. The mRNA is complementary to the template or antisense strand. The information from the antisense strand is copied on to mRNA during transcription.

Sense strand: It is similar to the mRNA except that T is replaced by U, which codes for the polypeptide chain. It contains the sequence of bases to which RNA polymerase binds and begins transcription. It also contains the stop or terminator sequence at the end of each gene that causes RNA polymerase to stop transcription.

Anticodon: A sequence of three bases that will pair up with the complementary codons of mRNA. The anticodon determines which amino acid can bind with the amino acid methionine only.

Ribosome: To hold the mRNA molecule and enzymes so that anticodons of tRNA can pair up with complementary codons of mRNA

Stop codon: The stop codon signals the termination of translation. It allows a release factor to bind the mRNA. This prevents another amino acid from binding o the chain and cause ribosomal sub-units to seperate.

Start codon: Finds the start point of the mRNA

tRNA: Transfer amino acids from cytoplasm to the ribosome. tRNA then matches amino acids to their specific codons within the ribosome. The tRNA binds with a specific amino acid in the cytoplasm to form amino-acyl complex.

This is pretty much the only thing I was unsure about :smile:

thank you

Reply 585

Original post by VRS

basically... this is forensic entomology and the study of the life cycle of a blow fly...

1.

Blow Fly (adult)

2.

(+23 hours) Laval 1st stage

3.

(+27 hours) 2nd laval stage

4.

(+22 hours) 3rd laval stage

5.

(+130 hours) pupa

6.

(+143 hours) adult blow fly

basically this life cycle is used to determine how long ago that person died...

like if there was pupa in there, they person died around 202 hours ago

hei,just making sure,....is this in order??
i mean first 23hrs then 27 and then 22???

Reply 586

lucy20

Original post by cisne

Antisense strand: This serves as a template for the formation of mRNA. The mRNA is complementary to the template or antisense strand. The information from the antisense strand is copied on to mRNA during transcription.

Sense strand: It is similar to the mRNA except that T is replaced by U, which codes for the polypeptide chain. It contains the sequence of bases to which RNA polymerase binds and begins transcription. It also contains the stop or terminator sequence at the end of each gene that causes RNA polymerase to stop transcription.

Anticodon: A sequence of three bases that will pair up with the complementary codons of mRNA. The anticodon determines which amino acid can bind with the amino acid methionine only.

Ribosome: To hold the mRNA molecule and enzymes so that anticodons of tRNA can pair up with complementary codons of mRNA

Stop codon: The stop codon signals the termination of translation. It allows a release factor to bind the mRNA. This prevents another amino acid from binding o the chain and cause ribosomal sub-units to seperate.

Start codon: Finds the start point of the mRNA

tRNA: Transfer amino acids from cytoplasm to the ribosome. tRNA then matches amino acids to their specific codons within the ribosome. The tRNA binds with a specific amino acid in the cytoplasm to form amino-acyl complex.

Thank you !

Reply 587

Freyma

2

Can some one post up all of the Core Practicals we need to learn?

Reply 588

Original post by ConnorB

This is pretty much the only thing I was unsure about :smile:

thank you

most welcome :smile:

Reply 589

lucy20

can anyone please tell me what exactly we need to know about specific immune response ? finding it really difficult to remember everything :frown:

Reply 590

Original post by VRS

Taking samples deep from the earth (around 1-2.5metres) analysing the seeds, then using the seeds to decide what the climate was like back then. If there were loads of oak seeds (say oaks only grow in a hot climate) then it was hot back then.

Thank you!
Is there anything more because the book doesn't go into detail :s-smilie:

It might come up :frown:

Reply 591

Original post by lucy20

Thank you !

most welcome :smile:

Reply 592

Original post by Freyma

Can some one post up all of the Core Practicals we need to learn?

http://www.thestudentroom.co.uk/show...&page=9&page=9
last post of the thread....

Reply 593

19941994

Original post by This Honest

Can someone explain peat bogs to me. Still don't fully understand it..

I think you just need to know that pollen can be used in peats to determine climate conditions at the time the pollen was laid
This is because pollen is produced in vast amounts and are very resistant to decay (tough outer layer). Peat forms in layers, deeper layer = older peat. Also each species of plant has a unique type of pollen, so each species of plant has particular conditions that it flourishes best in. So the amount of pollen in the peat tells us what the climate was like

This was posted from The Student Room's iPhone/iPad App

Reply 594

Also does anyone know the proper definitions for GPP and NPP and trophic level?

Reply 595

avataraang

Original post by demdil

i am very bad at speciation, does anyone have general points that get marks for speciation? they ask it on each paper and i always get 2 marks maximum from that :O

I will give this a shot...

Speciation is the formation of a new species.
* Firstly, the mainland population is seperated, possible due to a natural disaster like a volcano or earthquake. This seperates the population into two different environments with different selection pressures (e.g. temperature, food etc.)
* Random mutations have already occured in the population beforehand, some of these may be advantageous and therefore in response to the selection pressure, they are more likely to survive and reproduce to give fertile offspring. This is reproductive isolation.
* Due to restricted gene flow, the mutations are passed onto the offspring and the allele frequency of this mutation will increase.
* Over time, wide differences in genotype of the two species leads to changes in phenotype making them unable to reproduce any further to give fertile offspring. Interbreeding cannot occur. Speciation has happened.

I think that is all the points! :smile:

Reply 596

Original post by 19941994

I think you just need to know that pollen can be used in peats to determine climate conditions at the time the pollen was laid
This is because pollen is produced in vast amounts and are very resistant to decay (tough outer layer). Peat forms in layers, deeper layer = older peat. Also each species of plant has a unique type of pollen, so each species of plant has particular conditions that it flourishes best in. So the amount of pollen in the peat tells us what the climate was like

This was posted from The Student Room's iPhone/iPad App

Ok thanks!
So if the pollen was in small amounts, what does that tell us?

Reply 597

19941994

Original post by This Honest

Also does anyone know the proper definitions for GPP and NPP and trophic level?

NPP- The rate at which energy is incorporated into organic molecules that make up the new plant biomass

GPP- the rate at which energy is encorporated into the plant during photosynthesis

This was posted from The Student Room's iPhone/iPad App

Reply 598

avataraang