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Justify the choice of experimental procedure below and the recording method used to...

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natalyap12 | Student, Grade 11 | (Level 2) Honors

Posted February 26, 2010 at 6:57 PM via web

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Justify the choice of experimental procedure below and the recording method used to collect and record the data?

I investigated the effects of temperature (room temperature, 25°C, 30°C) and glucose conc. (1%, 5%, 10%) on the growth of yeast, and measuring its growth by counting the number of yeast cells in 1mm3 at five time points over a 48 hour time period using a haemocytometer. I was provided with 250ml of a 0.1% yeast culture.

Method –

1. Label 10 boiling tubes with a number 1 to 10 plus your initials, add the following to each tube then seal the tops with a plug of cotton wool.

  1. RT 1% - 20mls 0.1% yeast culture + 0.2g glucose
  2. RT 5% - 20mls 0.1% yeast culture + 1.0g glucose
  3. RT 10% - 20mls 0.1% yeast culture + 2.0g glucose
  4. 25°C 1% - 20mls 0.1% yeast culture + 0.2g glucose
  5. 25°C 5% - 20mls 0.1% yeast culture + 1.0g glucose
  6. 25°C 10% - 20mls 0.1% yeast culture + 2.0g glucose
  7. 30°C 1% - 20mls 0.1% yeast culture + 0.2g glucose
  8. 30°C 5% - 20mls 0.1% yeast culture + 1.0g glucose
  9. 30°C 10% - 20mls 0.1% yeast culture + 2.0g glucose
  10. Control - 20mls of water + 0.2g glucose

2. Do an initial count on all tubes and record these readings as T0.

3. Place all the RT (room temp) labelled tubes (1%, 5%, 10%) in a cupboard and note the temperature,

Place all the 25°C and 30°C labelled tubes in the correct water baths.

4. Count the yeast in each tube at the following hourly time intervals: T0, T24, T27, T30, T48.

I recorded my results (data) in a table.

1 Answer | Add Yours

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litteacher8 | Middle School Teacher | (Level 1) Distinguished Educator

Posted March 1, 2012 at 12:29 PM (Answer #2)

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I suggest you justify what you did by explaining that you were methodical in creating and labeling the samples, and you collected them at regular intervals. This is good because it avoids samples being just random, and avoids confusion and mix up of samples.

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