Edexcel BIOLOGY Doubts!!!!

[MKh]

Salaam all, I have a few qns regarding the core practicals for Edexcel AS Bio:

We get practical-related questions in all three of the AS Bio papers - U1,U2 & U3B. We are usually asked to write down the procedures of the core practicals like the Daphnia and the Vitamin C core practical questions. Could anyone of you write down the appropriate step-by-step procedure of each of the following core practicals along with 1) the safety precautions that we have to take and 1) the associated risks, and 3) the variables/factors to be controlled in these investigations and 4) how to control these variables/factors and also 5) what if these variables/factors are not controlled??

Unit 2, Topic 4: 1. Describe how to determine the tensile strength of plant fibres practically.

2. Describe how to investigate plant mineral deficiencies practically.

3. Describe how to investigate the antimicrobial properties of plants.

I have already checked out the AS Bio Core pracs worksheet which you guys must already be aware of but it doesn't seem to help much in understanding step-by-step procedures of these core pracs....What are the steps your teachers taught you for these core pracs?  We can be asked to write down the procedures of these core pracs, that is why I asked.

Any other help/suggestions regarding AS Bio core pracs would be highly appreciated… Thanks all...

[dragon_knight]

how should we prepare for unit 6 internation alternative to practical of edexcel biology?

and any references that could teach me the statistical tests in unit 6, and any tips for answering paper 6?

[mayisha]

Suggest an explanation for why a whole muscle might respond differently to a stimulus than a single fibre ... its from the edexcel bio a2 book

[Amelia]

Suggest an explanation for why a whole muscle might respond differently to a stimulus than a single fibre ... its from the edexcel bio a2 book

 Muscles consist of large numbers of (long cells) muscle fibres bound together by connective tissue. They can contract (shorten) to do work. When they relax, they can be pulled back to their original length.

The whole muscle will respond differently because different fibres have different tresholds and contract with different strengths.

Here

[moalna]

1. Explain why base pairs are a suitable way of measuring length of a piece of a DNA?

2. Explain why (1) Penicillin, (2) Tetracyclin and (3) Quinolones are not effective against viruses?

[MKh]

Salaam all, I have a few qns....I hope u guys will be able to help to your best.

1) what is the difference between random error and systematic error?

2) what is the difference between a belt transect and a line transect?
Have you guys got any pics of belt transect and line transect in your books, guides, notes etc. I want to know how each one looks to make their difference clearer.

Tried googling this and got answers but they were not very clear and people over here have better info than google so please share your info. thanxx...

[Master_Key]

Salaam all, I have a few qns....I hope u guys will be able to help to your best.

1) what is the difference between random error and systematic error?

2) what is the difference between a belt transect and a line transect?
Have you guys got any pics of belt transect and line transect in your books, guides, notes etc. I want to know how each one looks to make their difference clearer.

Tried googling this and got answers but they were not very clear and people over here have better info than google so please share your info. thanxx...

1) The main Diff. is one can be corrected by repeating experiment but other cannot.

[~ Miss Relina ~]

1) The main Diff. is one can be corrected by repeating experiment but other cannot.

and that one which can be corrected by repetition is the random

[Amelia]

1. Explain why base pairs are a suitable way of measuring length of a piece of a DNA?

DNA is measured in base pairs because it is usually double-stranded. Hence, the number of total base pairs is equal to the number of nucleotides in one of the strands (with the exception of non-coding single-stranded regions of telomeres).

2. Explain why (1) Penicillin, (2) Tetracyclin and (3) Quinolones are not effective against viruses?

Because they are antibiotics and hence, used for fighting bacterias and not viral infections.

[moon]

Can u please help me in these questions

1) Explain what is meant by the term genetic carrier?

2) One of the polypeptide chains in the haemoglobin of a person with sickle cell anaemia has a change in one of its amino acids.Explain how change in   
    DNA can lead to a change in a single amino acid in polypeptide chain.

I appreciate ur help!!

[Amelia]

Can u please help me in these questions

1) Explain what is meant by the term genetic carrier?

A genetic carrier (or just carrier), is a person or other organism that has inherited a genetic trait or mutation, but who does not display that trait or show symptoms of the disease. They are, however, able to pass the gene onto their offspring, who may then express the gene. This phenomenon is a direct result of the recessive nature of many genes.

For example, the daughters of Queen Victoria, the princesses Alice and Beatrix, were carriers of the X-linked hemophilia gene (more precisely, an abnormal allele of a gene necessary to produce one of the blood clotting factors). Both had children who continued to pass the gene to succeeding generations of the royal houses of Spain and Russia, into which they married. Males who carried the altered gene had hemophilia, while females simply passed it to about half of their children.

-Wikipedia.  

2) One of the polypeptide chains in the haemoglobin of a person with sickle cell anaemia has a change in one of its amino acids.Explain how change in    
    DNA can lead to a change in a single amino acid in polypeptide chain.

I appreciate ur help!!

Each base pairing in the DNA sequence codes for a different amino-acid. So, a change in these base-pairing will change the aminoacid it is supposed to code for. This will alter the polypeptide chain.

[MKh]

Salaam all, I have a question:
what is the meaning of range bars and error bars? Are both the same thing? If yes, what are these actually? I think these are used in graphs but I am not sure how to draw or interpret a range bar or error bar??

Help if anybody knows anything about these...Thanks!

[guMnam]

what is the role of elastic recoil in the arteries ??

[Amelia]

what is the role of elastic recoil in the arteries ??

The vessels which receive blood from the heart, the elastic arteries, have thick, strong walls to cope with the sudden high pressure produced during diastole; they contain abundant elastic material to allow stretch so that the vessel lumen may accommodate the change of volume. They also have a thick, outer coat of collagenous connective tissue whose tensile strength prevents over-distension of the elastic tissue.

The elastic recoil of these elastic arteries is responsible for maintaining a continuous, though decreased, flow of blood to smaller vessels during systole.

[mayisha]

Can sum1 plz explain the t-tests and confidence levels ? or suggest a book where its explained wel but not 2 detailed ... just wats needed for unit 6 bio ...