TMAs, Advice and Exercises

Read the rubric of a question carefully. Make sure you understand exactly what is being asked.

Answer the question asked, not what you would like the question to be. More marks are lost from failure to address the actual question than from any other cause.

Before you write, PLAN! Structure your answer. For essays, include an opening, present a logical progression of arguments, and end with a conclusion.

Use facts and arguments that bear on the question. Resist the temptation to use the "shotgun approach" (everything I know about ...).

When you finish, REVIEW! Ask yourself: Have I omitted relevant points/arguments? Have I included irrelevant material?

Distinguish fact from possibility.

Back up arguments with clear assertions based on agreed facts.

Use the scientific terminology introduced in the course. The tutor may be looking for the appropriate use of terminology in the correct context.

Don’t leave important points or steps in an argument to be inferred – SPELL THEM OUT!

Would diagrams help? Tutors are often instructed to award marks for the appropriate use of diagrams to support an answer.

If you include any material from outside the course in your answer, please give a clear reference to the source (e.g. state the book title, author and date; the OU course code and page reference; the journal title and date with the title of the paper and the author; the name of the Internet site). However, questions can normally be answered perfectly well on the basis of the course materials alone.

Reading around the course is strongly to be encouraged! By all means use appropriate material from outside the course in TMAs. But be careful that such material is relevant to your answer. Remember that the use of outside material in a TMA, including material gleaned from the Internet, does not in itself earn marks.

Pay attention to any word limits. These are guidelines to be treated with respect, though not slavishly followed unless the rubric of the question says so! Within reason, use the space you need to answer the question, but remember that word limits are an indication of how long a full answer should be. If you are far over a word limit, look at your answer again and consider whether it needs to be redrafted. The tutor will not hold you precisely to X number of words, but gross violations of word limits may lose marks.

Show your working for any mathematical calculations.

Make sure you have answered ALL the questions on the TMA. Many marks are lost by students overlooking Q3aiii, or failing to turn over the page where another question lurks!

REMEMBER, YOUR "JOB" IS TO MAKE IT EASY FOR THE TUTOR TO AWARD MARKS.

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Exercise

The Deccan Traps and the K/T Extinction

Read the extract below from a recent article, and write a brief account, either in opposition to or in support of, the proposed hypothesis to explain the end-Cretaceous mass extinction of the dinosaurs. Base your account on what you have learned in Evolving Life and the Earth and The Dynamic Earth.

You will find a model answer by selecting the link at the end of the article below. Try writing your own account first, and then compare your answer to the model answer. There is no one "right" way to write this essay. The model answer is just that -- a model. It is designed to show by example how such a TMA question might be tackled.

Extracted from Louis Psihoyos, "What Really Killed the Dinosaurs?", New Scientist, 16 August 1997.

"The Deccan Traps, a vast plateau in southern India, were created over a few million years at the end of the Cretaceous when about a million cubic kilometres of lava gushed onto the Earth’s surface…

"The eruption was undoubtedly severe. ‘The stress it imposed on the environment would have been phenomenal,’ says Andrew Kerr of the University of Leicester. ‘It beggars belief that the asteroid impact people can ignore it.’

"A very similar outburst of supervolcanism, responsible for the Siberian Traps, coincided with the biggest of all mass extinctions, the Permian-Triassic extinction, which happened about 250 million years ago…

"Sulphur dioxide unleashed by supervolcanism would have created hellish acid rain, while an increase in carbon dioxide would have caused dramatic greenhouse warming. It was this warming that [Dewey] McLean [of Virginia Polytechnic Institute and State University in Blacksburg, Virginia] sees as the principal culling mechanism…

"McLean’s mechanism …is not an obvious one. When the air temperature rises, he says, adult animals cool themselves by diverting blood to the surface of their skin. This reduces the flow of blood to the oviducts and uterus – the sites of fertilisation and of embryonic development.

"This is important because uterine blood flow carries damaging heat away from the region of the uterus and carries nutrients to the developing embryo. ‘In cows, the embryo is killed if the oviduct temperature rises by a mere 1 to 1.5° C above the optimum during the first cleavage of the fertilised egg…’

"…McLean says that, during the rapid greenhouse warming caused by supervolcanism at the end of the Cretaceous, the process of shunting blood away from the oviducts and towards the skin in female dinosaurs would have caused their oviducts to heat above the optimum, killing or damaging any embryos… ‘Times of rapid greenhouse warming are especially hard on large animals…Their small surface-to-volume ratios mean that they retain excess body heat, increasing the mortality rate of embryos.’ So the supervolcanic hypothesis could perhaps explain the selectivity of the extinctions…"

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