Writing essays and dissertations

The basics of scientific writing are always the same, whatever the task. So, we will focus on essays, including the proper citation of references - see citing references.

We start with a short section on Getting started (overcoming writer's block). If you don't have this problem then go straight to How to write an essay.

Getting started

Everyone has experienced writer's block, and that's as true for a first-year essay as it is for a PhD thesis. It is a psychological hurdle - the task ahead seems daunting, and you spend ages trying to decide how you will produce the perfect, polished, final product. Meanwhile you have produced nothing; you are no further forward! Or perhaps you do start - you write the first few paragraphs, you don't feel happy with them, so you rewrite them again and again, and never make progress. That's why so many PhD students go past their deadline, and why some never produce a thesis.

The solution is simple, and it always works. Let's assume that you have done all the preparation - you know more or less what you want to write about, and you have accumulated lots of rough notes or experimental results, etc.

Start writing, keep going, and don't look back until you get to the end!

Remember that this is your first draft, and no-one else will see it. Don't worry about the finer points of structure. Don't worry about the order of your sentences - sometimes the order will be sensible, sometimes not. Don't worry about your spelling or punctuation. Don't worry if you can't find the right word or phrase - just use dashes (--------) or a reminder such as (say something about dogs here) and keep going. Don't even worry if something you have written is not strictly true or will need to be checked. Just keep going!

Once you have produced this rough draft you will have broken the back of the job. Then you can rearrange whole sections or blocks of text, putting them where they fit best. And then you can go through the text, correcting anything you need to correct, and inserting anything you need to insert.

Everything that I have ever written (including two books, more than 100 scientific papers, and even this web site) was produced initially as a rough draft from start to finish, and then rewritten or rearranged at least 3 times. The Cut, Copy and Paste buttons on word-processors make the job easy when you have got the basic content in place.

How to write a good scientific essay

[See important guidance on PLAGIARISM]

Good writing requires preparation, organisation and structure.

We don't really need these things in an email message (although it helps!). We certainly need them for anything that we want to "put on record" - an essay, a scientific report, etc.

'Far too many relied on the classic formula of a beginning, a muddle and an end'

Philip Larkin
New Fiction

Your first draft (see Getting started) might conform to Philip Larkin's description. Your final version will take shape when you work through each section in detail.

What makes a good scientific essay?

The answer is: good structure and good content. Look at your favourite textbook, or one of the good review journals such as "Trends" (Trends in Evolution and Ecology, Trends in Microbiology, etc.). Why do you like it? Because its structure guides you through the subject in an accessible way:

  • the Introduction sets the scene;

  • the separate sections have headings;

  • the longer sections are divided into sub-sections, with sub-headings, so you don't have to plough through long sections of text;

  • the tables, diagrams and photographs illustrate or summarise key points, while also breaking the text (textbook editors are skilled at making the pages appear interesting);

  • the Conclusion puts everything in perspective, and typically suggests where further work is needed;

  • the References cover key areas referred to in the text.

Your essay should have the same features. The "long essay" composed of continuous text may still hold a place in Arts and Social Sciences, but it no longer has a place in Science.

(i) The Introduction

Any piece of writing should have an Introduction. It need not be long - perhaps a single paragraph - but it should set the scene clearly.

For a scientific paper it is usual to give an overview of previous work in the field, then state why you did your work - e.g. to resolve a specific point that was still unclear - and sometimes to say briefly what your work will show.

For an essay it is usual to define clearly the subject you will address (e.g. the adaptations of organisms to cold environments), how you will address this subject (e.g. by using examples drawn principally from the Arctic zone) and what you will show or argue (e.g. that all types of organism, from microbes through to mammals, have specific adaptations that fit them for life in cold environments).

The Introduction will be the first section that you write, but it will probably be one of the last sections that you revise, to make sure that it leads the reader clearly into the details of the subject you have covered.

Check-list for the Introduction

  • Does your Introduction start logically by telling us what the essay is about - for example, the various adaptations to habitat in the bear family (Ursidae)?

  • Does your Introduction outline how you will address this topic - for example, by an overview of the habitats of bears, followed by in-depth treatment of some specific adaptations?

(ii) The main body of text

The main body of text should have a clear, obvious structure. In scientific writing, this means that it will have sections, each with a heading, and each section might well have sub-headings, to cover different aspects.

You will need to think about the hierarchies of headings, so that the reader doesn't get lost. There are several ways of doing this, but one example is:

Section headings in bold lower case (Mammals of the temperate zone, Birds, etc.)
Sub-sections in italics (The arctic fox, The polar bear, etc.) or underlined.

You should include tables, diagrams, and perhaps photographs in your essay. (See tables, diagrams, photographs). Tables are valuable for summarising information, and are most likely to impress if they show the results of relevant experimental data. Diagrams enable the reader to visualise things, replacing the need for lengthy descriptions. Photographs must be selected with care, to show something meaningful. Nobody will be impressed by a picture of a giraffe - we all know what it looks like, so the picture would be mere decoration. But a detailed picture of a giraffe's markings might be useful if it illustrates a key point.

All the points above refer to structure and presentation. But, of course, the most important point is that an essay must have substance. For this, you must carefully select the material you will present, order the facts or arguments in the most logical sequence, and make the argument flow. For example, if you are writing an essay about adaptations to cold environments, it is not enough to just piece together a series of examples - a cold-adapted bacterium, a cold-adapted moss, a cold-adapted bear, etc. Instead, you should have chosen your examples to illustrate the adaptations that they have in common, or the contrasting ways in which they achieve the same result, and make these points as you go through the essay.

Useful tips:

1. Often you will have a word limit - say, 2000 words. Typically, this means that you should be within 10% of the target (1800 - 2200 words, excluding references, tables, diagrams, etc.). Anything much more, or less, is likely to be penalised.

2. How can you cover anything reasonably in 2000 words, when you could write at least 10,000 words on the subject? That's just the point - we (the markers or readers) don't want to read 10,000 words, and there is no guarantee that it would be any better than 2000 words. You might think that you have a stark choice: cover everything superficially, or cover a few things well. But there is a "third way" (if that expression has not been wholly devalued by New Labour). We can call it "breadth with depth": cover the main elements of the subject, then focus on one or two key issues for more detailed consideration. These issues should be selected carefully - and say so - for topicality, for the particular depth of study they have received, etc.

Checklist for the main body of text

  • Does your text have sections with headings and sub-headings?

  • Does the text follow a logical sequence, so that the argument flows?

  • Does your text have both breadth and depth - i.e. general coverage of the major issues, with in-depth treatment of particularly important points?

  • Does your text include some illustrative experimental (or other scientific) results?

  • Have you chosen the diagrams or photographs carefully, to provide information and understanding, or are the illustrations merely decorative?

(iii) The Conclusion

An essay needs a conclusion. Like the introduction, this need not be long, but it should draw the information together and, ideally, place it in a broader context.

Unfortunately, the conclusion is often the most difficult part of an essay. Student essays all too often end with some bland statement such as "As can be seen by the examples I have discussed, organisms that live in cold environments usually have specific adaptations that fit them for these conditions."

That's just words: an excuse for a conclusion. On the other hand, a conclusion should not introduce more facts. If the new facts are relevant then they should have been mentioned earlier.

The best conclusions are those that show you are thinking further. For example, it might be interesting to transfer cold-adapted organisms to more moderate environments and see whether the "cold-adapted" traits are still expressed. Or, it might be interesting to look for sequence homology in the genes of cold-adapted organisms and organisms of more moderate environments. As a last resort, you might use a nice, short quotation - preferably a witty one to put the marker in a good mood!

[A note on conclusions in exam answers. Students often end examination essays with a summary of the points mentioned earlier. This is a total waste of time. You can only score the marks once, no matter how many times you repeat a point.] Click here for more guidance on examination technique.

(iv) References and citations

In all scientific writing you are expected to cite your main sources of information. Scientific journals have their own preferred (usually obligatory) method of doing this. The piece of text below shows how you can cite work in an essay, dissertation or thesis. Then you produce an alphabetical list of references at the end of the essay.

Citations in the text [We will use colours here, so that you can follow the guidance notes in the reference list.]

Jones & Smith (1999) showed that the ribosomal RNA of fungi differs from that of slime moulds. This challenged the previous assumption that slime moulds are part of the fungal kingdom (Toby & Dean, 1987). However, according to Bloggs et al. (1999) the slime moulds can still be accommodated in the fungal kingdom for convenience. This view has been challenged by Deacon (1999).

In the reference list at the end of the essay: [List the references in alphabetical order]

Bloggs A.E., Biggles N.H. & Bow R.T. (1999) The Slime Moulds. Academic Press, London & New York.

[Guidance: this reference is to a book. We give the names of all authors, the publication date, title, name of publisher and place of publication. Note that we referred to Bloggs et al.(1999) in the text. The term "et al." is an abbreviation of the Latin et alia (meaning "and others"). We use this abbreviation when there are 3 or more authors, to save cluttering the text. Note also that "Bloggs et al." is part of a sentence in the text, so we put only the date in brackets.]

Deacon J.W. (1999) The Microbial World (http://helios.bto.ed.ac.uk/bto/microbes/microbes.htm) [accessed 15 November 1999]

[Guidance: this reference is to a website. We give the name of the author (or organisation if there is no author) and the full URL (web address). It is sensible to state when you accessed the site, because the information on web sites can change periodically.]

Jones B.B. and Smith J.O.E. (1999). Ribosomal RNA of slime moulds. Journal of Ribosomal RNA 12, 33-38.

[Guidance: this is a reference to a published scientific paper. We give the names of all authors, the date, title of the paper, the journal, volume number (in bold) and page numbers (first and last) of the paper.]

Toby F.S. & Dean P.L. (1987). Slime moulds are part of the fungal kingdom. In A. E. Edwards & Y. Kane (eds) The Fungal Kingdom. Osbert Publishing Co., Luton.

[Guidance: this is a reference to a chapter in a book edited by Edwards & Kane. We give the names of all authors, date, title of the article, editors of the book, title of the book, publisher and place of publication. Note how we cited this reference (Toby & Dean, 1987) in the text. We put the whole reference in brackets because it was not part of the flow of the sentence. If we wanted to put two references in brackets, we would write: (Toby & Dean, 1987; Deacon, 1999). Typically, we would use chronological order (1987 before 1999) and separate the two references by a semicolon.

(v) Tables, diagrams, photographs

Technicalities. Tables, diagrams and photographs can be (1) xeroxed into spaces which you leave in the text, (2) scanned onto a disk, using a flat-bed scanner, then imported into a Word document, (3) copied from a WWW source and imported into a Word document, or (4) xeroxed and simply glued into your text. [Click here for guidance on saving and importing images from WWW sources]. Remember that almost anything you use will be covered by copyright. It is wise to ask (email) the owner of a website for permission to use the image in an essay. In my experience few would refuse such a "one-off" request.

Labelling, legends and acknowledgment. Whenever you use a table, diagram or image in your essay you must:

  • cite the source (e.g. from Bloggs, 1989)

  • use your own legend and explanation, not the original one.

For example: Figure 1. The pathway of synthesis of the amino acid alanine, showing...From Bloggs (1989). [Never use the original legend, because it is likely to have a different Figure number and to have information that is not relevant for your purposes. Also, make sure that you explain any abbreviations or other things that your reader needs to know about the Figure]

vi. Quotations

Often in a scientific essay you will need to quote sections of other people's work. You do this in the standard way, by using quotation marks and citing the source of the information.

For example: Mansell (1999) stated that "The World is round."
Or: "The World is round." (Mansell, 1999).

Be careful not to over-quote. The best advice is to quote only highly significant sentences or phrases, not "The world is round" or "All mammals have fur", nor points that could be made equally well in your own words. See the guidance on Plagiarism.

When quoting other people's work, a few rules must be followed. They are stated here, then illustrated in an example.

  • Always quote the words exactly as the person gave them.

  • If you need to miss out parts of the quoted section because they are not relevant for your purposes, then use an ellipsis (three dots). Note that there are no spaces before or after an ellipsis.

  • If you need to add your own words, to make sense of the quoted material, then put your words in square brackets [].

  • If there is an error in the quoted material then write '(sic)' after it, to show that the error is not yours. But this is most unlikely to arise. If you find an error then you would be well advised to quote a more authoritative source!

An example:

One of the students wrote "...the world is like a giant balloon...[that] spins about it's (sic) axis...[and] orbits the sun."

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