Edexcel BIOLOGY Doubts!!!!

[rameeziiii]

^Thanks alot


Can anyone explain me Q7 b i and ii of this paper (attached)

Let me try to help as best as I can.
First off, you can see from the table that the Ulva photosynthesize most in RED light. From this, we know that the plant likes RED light and will flourish in areas with high amounts of RED light. Now, as the question says, RED light does NOT penetrate deep into water which means the plant will be most in shallow areas. This means that the Ulva will mostly be located at the top of the shore. Top of shore means the area with less water, in case you were wondering.

Second off, you can also see from the table that the dubyi photosynthesizes heaviest in GREEN light. Deep water ALLOWS for the penetration of GREEN light ( question says only yellow, orange, and red light are absorbed, meaning that green will pass through). Since GREEN light can reach deep into the water, the dubyi will be found all over the shore, as GREEN light reaches all those places.

Did that help?

[SZM]

Hello forum, in our edexcel Biology new syllabus,under specification point number 1 in topic 1, 2, 3 4, 5, 6 7 and 8, it states, that-

Students will be assessed on their ability to demonstrate knowledge and understanding of the practical and investigative skills identified in numbers 4 and 5 in the table of How Science Works on page 13 of this specification.


Can u please tel me what does this specification point means and what do they want us to know?? Pls tel me clearly in details.

This is the link for edexcel GCE Biology new syllabus.

http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/UA024831%20GCE%20in%20Biology%20Issue%204%20250510.pdf

Please help me immediately///

I need ur reply very urgent.

Thanx for ur advance.

[Malak]

How can we show variability on graph?

E.g. Unit 3B Sample assesment Q1 b (ii)

thanks

[Amelia]

I think variability means the range, the interquartile range (IQR), variance, and standard deviation.

You know how to calculate those, right?

[Romeesa-Chan]

Draw the error bars to show the variability.

[MKh]

How can we show variability on graph?

E.g. Unit 3B Sample assesment Q1 b (ii)

thanks

To show the variability in the data, you have to include 'range bars' or 'error bars' on each plot of your (bar or line) graph. Range bars and Error bars are the same thing. In the A2 level, you always have to include them in your graph whether asked to do so or not, but I am not sure if it's the same at AS. I assume, in the AS level also, you have to include them in your graphs since doing so usually gets you a mark.

To see an example of error bars/range bars on a bar chart, see the link below, although you don't have to know all that inorder to draw error bars/range bars on your line or bar charts. Here's the link: http://en.wikipedia.org/wiki/Error_bar

Now, for example, if you have to plot a graph of a set of mean values, you will first have to decide whether you are going to plot a bar chart or a line graph. If you have 5 or more mean values to plot, you have to draw a line graph - so plot each point and join them with a straight line of best fit or a curve, although, in most cases, you have to draw a stright line of best fit. If you have 4 or less mean values to plot, you have to draw a bar chart.

Now, how do you draw error bars/range bars on your line or bar graph?
To answer this question, ask yourself how you obtained those mean/average values that you have plotted on your line or bar graph. You have obviously used a SET OF VALUES to calculate a mean value for that particular set. This SET OF VALUES for each mean value that you have plotted, is very important as it will allow you to draw an error bar/range bar on each plot of your line or bar graph.

You have to plot a range bar/error bar with each plot on your graph (that is, with each mean value). So, for example, you have 3 mean values (23, 24 and 25) and you have to show these on a graph. Draw a bar chart (as there are 3 values to plot) and draw a bar to represent each mean value on your graph.
Now, how do you draw an error bar/range bar on each of the three bars on your graph?
So, you have calculated a mean value of 23 from a SET OF VALUES (say, 21, 22, 23, 24 and 25). One of your 3 bars on your bar chart is 23 and you calculated this value of 23 from a SET OF VALUES as mentioned above. To show the variability on your bar graph, draw an error bar/range bar on each bar. On the bar of 23, to show the error bar, draw a vertical line from the highest value (that is, 25) in your SET OF VALUES to the lowest value (that is, 21) in your SET OF VALUES and draw a small horizontal line on each end of this vertical line.

This vertical line along with a small horizontal line on each end of the line shows the SET OF VALUES that you used to calculate the plotted mean value on your (line or bar) graph. This is known as the error bar or range bar and shows the variability in the data. You have to draw such an error bar or range bar for each of your plotted value.

Although I have repeated myself on many occasions along my post here, I hope it helped your understanding of this concept. For further help, do not hesitate to quote me. You can also use google if you don't understand anything and hopefully you will get a clear explanation.

[Malak]

I understand what you mean...but..

For example, In my graph for one set of values (91, 75, 84 and 69 per 30 seconds) the mean is 159.5 beats per min, now the lowest value is 69 beats per 30 seconds. To draw the error bar, should I double 69? cause it is per 30 sec and not per min?

2ndly, I have started my graph from 150 and so the lowest value in the Set of values doesnt even fit in my graph :s ? I don't think an error bar would be that long.

[MKh]

I understand what you mean...but..

For example, In my graph for one set of values (91, 75, 84 and 69 per 30 seconds) the mean is 159.5 beats per min, now the lowest value is 69 beats per 30 seconds. To draw the error bar, should I double 69? cause it is per 30 sec and not per min?

2ndly, I have started my graph from 150 and so the lowest value in the Set of values doesnt even fit in my graph :s ? I don't think an error bar would be that long.

Ohhkay, so in that case, you will have to double the lowest value (that is, 69) in your SET OF VALUES which then becomes (69*2=) 138, and the highest value (that is, 91) in your SET OF VALUES which then becomes (91*2=) 182. Now you have got your highest and lowest values in BEATS PER MINUTE since all the plots in your graph are in beats per min.

Regarding the plotting problem, can you change your scales so that your error bars can fit within your graph?

In my exam, I had to choose my scales to be able to plot my mean values as well as my error bars although I had to draw a bar graph with two bars only. So choose your scales so that your plots as well as your error bars can fit within your graph.
Also, in my exam, one of my error bars was so long that it fit the whole graph paper. Without making your scales too cumbersome, try to choose an appropriate scale so that your error bars can fit within your chosen scale, even if they are too long.

Hope this solves the problem. I will try to solve the question myself also.

[rameeziiii]

Okay, massive pain in the *** question from me. HOW THE HECK DO YOU PERFORM THOSE T-TEST/Other-statistical-tests?

I just tried the one in the 2012 January paper, and understood NOTHING! I HAVE NO IDEA WHY THE VALUE OF 0.79 WAS USED INSTEAD OF THE 1.00 THE STUDENT USED, OR WHY YOU'RE SUPPOSED TO USE 7 MEANS OR ANYTHING

[MKh]

Okay, massive pain in the *** question from me. HOW THE HECK DO YOU PERFORM THOSE T-TEST/Other-statistical-tests?

I just tried the one in the 2012 January paper, and understood NOTHING! I HAVE NO IDEA WHY THE VALUE OF 0.79 WAS USED INSTEAD OF THE 1.00 THE STUDENT USED, OR WHY YOU'RE SUPPOSED TO USE 7 MEANS OR ANYTHING

Maybe try to google 't-test' or look it up on Wikipedia? Maybe the number of means has something to do with how these tests are performed?

[MKh]

Can someone help me with the following, please?

Read through the following passage on the structure of prokaryotic cells, then write on the dotted lines the most appropriate word or words to complete the account.
   
Bacteria, such as Escherichia coli, are prokaryotic organisms. One of the main differences between prokaryotic cells and eukaryotic cells is that in a prokaryotic cell, the bacterial chromosome is not surrounded by a ............................................. . Prokaryotic cells store carbon compounds in the form of ............................................. and ................................................. and they may also contain one or more small circular DNA molecules, known as ................................................ . E. coli cells are motile due to the presence of a......................................................... .
(Total 5 marks)

I think the answers are: nuclear membrane, glycogen granules, oil droplets, plasmids, flagellum.

Please confirm these answers. Thanks a lot.

[Malak]

Can someone help me with the following, please?

Read through the following passage on the structure of prokaryotic cells, then write on the dotted lines the most appropriate word or words to complete the account.
   
Bacteria, such as Escherichia coli, are prokaryotic organisms. One of the main differences between prokaryotic cells and eukaryotic cells is that in a prokaryotic cell, the bacterial chromosome is not surrounded by a ............................................. . Prokaryotic cells store carbon compounds in the form of ............................................. and ................................................. and they may also contain one or more small circular DNA molecules, known as ................................................ . E. coli cells are motile due to the presence of a......................................................... .
(Total 5 marks)

I think the answers are: nuclear membrane, glycogen granules, oil droplets, plasmids, flagellum.

Please confirm these answers. Thanks a lot.

Yeah, I wrote the same except that instead of oil droplets I wrote lipids but I think both are acceptable.

[rameeziiii]

Maybe try to google 't-test' or look it up on Wikipedia? Maybe the number of means has something to do with how these tests are performed?

Tried that before, didn't help one bit. Luckily for me, and most others who don't know how to attempt this, I found out after asking around on other forums and stuff.

So, this is how it goes:

We are using 7 means, because in the preceding parts, there were 7 concentrations being tested ( this includes the control of 0% caffeine, By the way)

Now, with the value they gave you in the question ( 1.00), look at the table in the row of 7 means and see which value is bigger is than 1.00 (Actually you're supposed to use the value immediately smaller than the value you have but this way is quicker and will save time.)

As you can see, there are no values bigger than 1.00 thus making our hypothesis completely correct and we will reject the null hypothesis.

Simple, wasn't it?

Now some of you may ask,( as I did) Why use the value of p=0.05? Well, you see, a (p) represents the Probability of error and the confidence value is equal to (1-p) * 100. In other words, p=0.05 represents a confidence level of 95%. When conducting a statistical test, a pre-determined confidence value is selected ( In all of Edexcel's cases, this confidence value if 95%) If the student carrying out the experiment gets a value greater than the critical value at the 95% confidence level the hypothesis will be correct, and the null hypothesis rejected.

That is how all of this stat stuff is done, and if you have some ( simple) questions, do ask as I have little preparation for my A2's apart from this.


Anyway, thanks.

~Rameeziiii

[NotAbod]

Where can I find more unit 2 papers to solve? I've solved all the 7 papers, and the specimen more than once.

[Deadly_king]

Where can I find more unit 2 papers to solve? I've solved all the 7 papers, and the specimen more than once.

Try CIE papers

The syllabus is much the same