Biology AS Edexcel Unit 3

[Lost_Life]

OMG OMG IM SO STRESSED!! I DONT KNOW WHAT TO REVISE! I CAN'T REVISE ANY OTHER SUB CAUSE I MIGHT MIX UP. PLUS, I SOLVED ALL THE PP

 

[bloom princeton]

then just RELAXXXXX..IF YOU DID ALL PP. AND CAN EASILY IDENTIFY THE VARIABLES AND LIST HOW TO CONTROL THEM and have a clear idea about each practical of the nine practicals(many suspect that MITOSIS experiment will be the one in this exam) but dont rely on that,make sure you know every step done and why was it done..AND UR CLEAR ABOUT RANGE BAR(variability), ERROR BAR, SDs, mode ,median, mean, outliers, correlation,causation, reliability, validity,accuracy systematic errors and random errors, ethical,social environmental and economical issues, bibliography (reference) . YOU JUST HAVE TO RELAXXXXXXXXX..and dont wrry no hard work goes in vain! GOOD LUCK

 

[3amak]

r

just read the article slowly underlining the useful and important points.. when you reach the suggestions, ex: how to improve the article, think outside the box. ex: you may say, by adding flow diagrams or pie charts to support the data..etc if you need more advice,ask. i'm here to help

my problem is how to write the reference in the biolography:S?

 

[Lost_Life]

r
my problem is how to write the reference in the biolography:S?

When writing a suitable bibliography, when writing the authors name, the second name (surname) should come first and then the first letter of his first name.

Eg. Michael Reiss should be written as Reiss M

When there are 2 or more authors the the second name should be written in alphabetical order.

Eg. Michael Frank, John Samuels
This should be written as Frank M, Samuels J

The order of the bibliography is constantly changing as you can see in the mark scheme. The best one to use for the upcoming paper if asked is :-

Author name(s), year of publish,(name of article in journal)*, Title of book\(journal), Publisher name, (Volume no. of journal)*, Pages
*Applies to journals

NOTE

When writing the page number and volume no. dont include "page no" in the biblography write it as "...cambridge press, 223-225"

Another point!

If in the student bibliography, if he has written for eg "Loh and others", if asked to write a suitable bibliography, u have to write "Loh et al"

 

[Lost_Life]

then just RELAXXXXX..IF YOU DID ALL PP. AND CAN EASILY IDENTIFY THE VARIABLES AND LIST HOW TO CONTROL THEM and have a clear idea about each practical of the nine practicals(many suspect that MITOSIS experiment will be the one in this exam) but dont rely on that,make sure you know every step done and why was it done..AND UR CLEAR ABOUT RANGE BAR(variability), ERROR BAR, SDs, mode ,median, mean, outliers, correlation,causation, reliability, validity,accuracy systematic errors and random errors, ethical,social environmental and economical issues, bibliography (reference) . YOU JUST HAVE TO RELAXXXXXXXXX..and dont wrry no hard work goes in vain! GOOD LUCK

can we discuss about reliability and validity? i guess its not very clear to me...

 

[karimz96]

it kinda does. You have to know how to arrange a reference or bibliography :

Format Examples

Books

Format:
Author's last name, first initial. (Publication date). Book title. Additional information. City of publication: Publishing company.
Examples:
Allen, T. (1974). Vanishing wildlife of North America. Washington, D.C.: National Geographic Society.
Boorstin, D. (1992). The creators: A history of the heroes of the imagination. New York: Random House.
Nicol, A. M., & Pexman, P. M. (1999). Presenting your findings: A practical guide for creating tables. Washington, DC: American Psychological Association.
Searles, B., & Last, M. (1979). A reader's guide to science fiction. New York: Facts on File, Inc.
Toomer, J. (1988). Cane. Ed. Darwin T. Turner. New York: Norton.

Encyclopedia & Dictionary

Format:
Author's last name, first initial. (Date). Title of Article. Title of Encyclopedia (Volume, pages). City of publication: Publishing company.
Examples:
Bergmann, P. G. (1993). Relativity. In The new encyclopedia britannica (Vol. 26, pp. 501-508). Chicago: Encyclopedia Britannica.
Merriam-Webster's collegiate dictionary (10th ed.). (1993). Springfield, MA: Merriam-Webster.
Pettingill, O. S., Jr. (1980). Falcon and Falconry. World book encyclopedia. (pp. 150-155). Chicago: World Book.
Tobias, R. (1991). Thurber, James. Encyclopedia americana. (p. 600). New York: Scholastic Library Publishing.

Magazine & Newspaper Articles

Format:
Author's last name, first initial. (Publication date). Article title. Periodical title, volume number(issue number if available), inclusive pages.

Note: Do not enclose the title in quotation marks. Put a period after the title. If a periodical includes a volume number, italicize it and then give the page range (in regular type) without "pp." If the periodical does not use volume numbers, as in newspapers, use p. or pp. for page numbers.
Note: Unlike other periodicals, p. or pp. precedes page numbers for a newspaper reference in APA style.
Examples:
Harlow, H. F. (1983). Fundamentals for preparing psychology journal articles. Journal of Comparative and Physiological Psychology, 55, 893-896.
Henry, W. A., III. (1990, April 9). Making the grade in today's schools. Time, 135, 28-31.
Kalette, D. (1986, July 21). California town counts town to big quake. USA Today, 9, p. A1.
Kanfer, S. (1986, July 21). Heard any good books lately? Time, 113, 71-72.
Trillin, C. (1993, February 15). Culture shopping. New Yorker, pp. 48-51.

Website or Webpage

Format:
Online periodical:
Author's name. (Date of publication). Title of article. Title of Periodical, volume number, Retrieved month day, year, from full URL
Online document:
Author's name. (Date of publication). Title of work. Retrieved month day, year, from full URL

Note: When citing Internet sources, refer to the specific website document. If a document is undated, use "n.d." (for no date) immediately after the document title. Break a lengthy URL that goes to another line after a slash or before a period. Continually check your references to online documents. There is no period following a URL.
Note: If you cannot find some of this information, cite what is available.
Examples:
Devitt, T. (2001, August 2). Lightning injures four at music festival. The Why? Files. Retrieved January 23, 2002, from http://whyfiles.org/137lightning/index.html
Dove, R. (1998). Lady freedom among us. The Electronic Text Center. Retrieved June 19, 1998, from Alderman Library, University of Virginia website: http://etext.lib.virginia.edu/subjects/afam.html

Note: If a document is contained within a large and complex website (such as that for a university or a government agency), identify the host organization and the relevant program or department before giving the URL for the document itself. Precede the URL with a colon.
Fredrickson, B. L. (2000, March 7). Cultivating positive emotions to optimize health and well-being. Prevention & Treatment, 3, Article 0001a. Retrieved November 20, 2000, from http://journals.apa.org/prevention/volume3/pre0030001a.html
GVU's 8th WWW user survey. (n.d.). Retrieved August 8, 2000, from http://www.cc.gatech.edu/gvu/usersurveys/survey1997-10/
Health Canada. (2002, February). The safety of genetically modified food crops. Retrieved March 22, 2005, from http://www.hc-sc.gc.ca/english/protection/biologics_genetics/gen_mod_foods/genmodebk.html
Hilts, P. J. (1999, February 16). In forecasting their emotions, most people flunk out. New York Times. Retrieved November 21, 2000, from http://www.nytimes.com




Hope that helped

how can we improve biobliography ?
thnx in advance.

 

[bloom princeton]

can we discuss about reliability and validity? i guess its not very clear to me...

OKAY SURE.. SEE
whether the data is reliable or not , u have to check the following:
the standard deviation whether it is high or low..do this by doing the following calculation (standard deviation divided by the mean) multiplied by 100..for the data to be reliable it should not be greater than i think (5% or 10%) im not quiet sure which one but more likely the 5%.
the second thing to check if there is an overlap in values ie.after you have added and subtracted the standard deviation from the mean value you have an idea about the RANGE of values obtained at a particular, say glucose con., do the same for the other samples and see if the values obtained between them overlap,if so THE DATA IS NOT RELIABLE, (this also means there's no correlation between the variables investigated) not sure about this point though you can check JAN.2012 check the markscehme it explains the above point.
on ther hand valid data means that the extent to which a measurement, test or studymeasures what it purports to measure.. the data will be valid if it is cross-checked with a data done by another person yet the same methodology ie the method used should be same and you must have all the info about that data say if you did an experiment about effect of temperature on vit.C content and compared it with data that also investigated the same aspect but in that data you are not told about the method used or the temperatures at which the experiment was carried out ,but bothe data show that as temp increases the vit.c content decreases , this is shown by both datas but a valid comparison cannot be made unless you know about the above mentioned aspects. validity of data will be better if it was compared by one that has been peer reviewed ie was found in a scientific journal etc. the validity of YOUR results can be checked,

 

[bloom princeton]

can we discuss about reliability and validity? i guess its not very clear to me...

can you tell me explain me the social, economical and environmental implications?

 

[bloom princeton]

how can we improve biobliography ?
thnx in advance.

it depends on the bibliography given to you..ie if only the website nme is mentioned you can improve it by commenting that a precise URL of the website should be given.. the date and the name of the authour must also be mentioned...so basically once you know the format of writing a bibliography see what is missing in the reference in the report..hope this helps

 

[T19]

can some one go over observing mitosis step by step and why each step is done
thanx in advance

 

[r97]

can some one go over observing mitosis step by step and why each step is done
thanx in advance

1-cut the tip from a growing root. it should be about 5mm long.
2-place the root tip in a watch glass and a few drops of hydrochloric acid.
3-add a few drops of stain,eg. orcein acetin.This will make the chromosomes darker and easier to see.
4-warm the watch glass,BUT DON'T ALLOW THE LIQUID TO BOIL, by running it through a bunsen burner flame or placing it on a hot plate.
5-place the root tip on a microscope slide and use a mounted needle to break it open and spread the cells out evenly.
6-add a few more drops of stain,eg. orcein acetin, and place a cover slip over it.
7-squash the cover slip down gently.
9-warm the slide for a few seconds. This will intensify the stain.

These are the steps Study them really well as it is expected to get mitosis in this session! Good Luck

 

[T19]

1-cut the tip from a growing root. it should be about 5mm long.
2-place the root tip in a watch glass and a few drops of hydrochloric acid.
3-add a few drops of stain,eg. orcein acetin.This will make the chromosomes darker and easier to see.
4-warm the watch glass,BUT DON'T ALLOW THE LIQUID TO BOIL, by running it through a bunsen burner flame or placing it on a hot plate.
5-place the root tip on a microscope slide and use a mounted needle to break it open and spread the cells out evenly.
6-add a few more drops of stain,eg. orcein acetin, and place a cover slip over it.
7-squash the cover slip down gently.
9-warm the slide for a few seconds. This will intensify the stain.

These are the steps Study them really well as it is expected to get mitosis in this session! Good Luck

thanx a lot this very useful but why we add HCl in step 2
good luck

 

[r97]

thanx a lot this very useful but why we add HCl in step 2
good luck

Umm i really don't know i asked myself the same question....maybe to kill any bacteria but that doesn't make sense :S if u knew the answer plz tell me at any time

 

[menna jamal]

https://www.edexcel.com/resultsplus/Pages/default.aspx
you need a pin to register. You can get one from your centre which I believe is the British council. Phone them.

i phoned the british counil but they said we dont have any password to provide you with. Could you plz take a screen shot of the documents and just paste it here. PLEASE

 

[tornado]

thanx a lot this very useful but why we add HCl in step 2
good luck

hydrochloric acid is used to break down the pectins that holds the cells together

 

[tornado]

sequence of observing mitosis and the reasons:
1- cut the final 5mm of a root tip from a plant such as onion or garlic bulb.
this is where mitosis occurs in the root
2- add stain such as orcein and add an acid (hydrochloric acid)
stain highlights chromosomes and acid soften the tissues
3- genty break open on a microscope slid and squash carefully.
this to spread out the cells so the layer is only one cell thick for easy viewing
4- add more stain and warm then look at the slide on a microscope.
this to intensify the stain.use microscope to see the cells and chromosomes


for safety:
1- care when cutting.
2- eye and skin care when using acid and stain
3- carfule not to break the glass slide when squashing

 

[T19]

hydrochloric acid is used to break down the pectins that holds the cells together

do u have explanations like this for all the steps and other experiments also

 

[bloom princeton]

Umm i really don't know i asked myself the same question....maybe to kill any bacteria but that doesn't make sense :S if u knew the answer plz tell me at any time

HCL is used to soften the tissues of the root tip,it does that by partially breaking the cell and its components

 

[r97]

HCL is used to soften the tissues of the root tip,it does that by partially breaking the cell and its components

Thnxx aloot

 

[bloom princeton]

DOES ANYONE KNOW HOW MICROMETER AND EYEPIECE GRATICLE CAN BE USED IN MEASURING THE PHASES OF THE CELLS??...