• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Bacteria and Cleanliness. Question: Among the insides of a toilet, dishcloth, sink, and a refrigerator handle, what is the cleanest?

Extracts from this document...


Pooja Mehta 4th period IB Biology 1-3-2010 Cleanliness Background: Bacteria are microorganisms that grow everywhere. We can collect and grow them in specially prepared Petri dishes. Blood agar or tryptic soy agar with 5% sheep's blood is an excellent medium for supplying bacteria with nutrients and an environment in which we can see them grow. Sterile powdered agar with nutrients can be mixed with water, heated and then poured into empty Petri dishes or ready-to-use dishes can be purchased. The indigestible agar is a gelatin-like substance with a semi solid surface on which the bacteria can grow while they consume the added nutrients (like sheep's blood). In fact, this is why gelatin itself does not make a good growing medium. Some bacteria can digest gelatin, which is a protein derived from animal tissue. This destroys the growing surface in the Petri plate making it unsuitable as a bacteria growth medium. CAUTION: Most bacteria collected in the environment will not be harmful. However, once they multiply into millions of colonies in a Petri dish they become more of a hazard. Be sure to protect open cuts with rubber gloves and never ingest or breathe in growing bacteria. Keep growing Petri dishes taped closed until your experiment is done. Then you should safely destroy the fuzzy bacteria colonies using bleach. Question: Among the insides of a toilet, dishcloth, sink, and a refrigerator handle, what is the cleanest? ...read more.


13. Before disposing of dishes in the trash the bacteria should be destroyed. Pour a small amount of household bleach over the colonies while holding dish over sink. CAUTION-do not allow bleach to touch your skin, eyes or clothes. It will burn! Data Table: Number of Bacteria Colonies in Petri Dish 1 Number of Bacteria Colonies in Petri Dish 2 Number of Bacteria Colonies in Petri Dish 3 Average Number of Bacteria Colonies in all 3 Petri Dishes Inside of a Toilet 175 colonies 195 colonies 180 colonies 183 1/3 colonies Dishcloth 268 colonies 254 colonies 271 colonies 264 1/3 colonies Sink 153 colonies 248 colonies 187 colonies 196 colonies Refrigerator Handle 200 colonies 198 colonies 202 colonies 200 colonies The positive control (the spit) did produce 264 bacteria colonies, and the negative control (nothing inside the Petri dish) produced 0 bacteria colonies, thus showing my experiment was properly conducted. Since the negative control yielded zero bacteria colonies, the number of bacteria colonies initially counted is the true number of bacteria colonies present. If the negative control did produce some colonies, we would have to subtract this number from the colonies counted upon experimentation. The uncertainty, which was derived from the standard deviations of each of the four areas tested, is as follows: Inside of a Toilet: � 10.4083 bacteria colonies Dishcloth: � 9.0738 bacteria colonies Sink: � 48.1352 bacteria colonies Refrigerator Handle: � 2 bacteria colonies The spread of data is due to the different areas of the four items I tested. ...read more.


Procedural errors were kept to a minimum, and the equipment in addition to the time management were suitable for this experiment. The time to collect all the bacteria took seven minutes, and the choice of equipment, as stated above, avoided any possible errors with judgment. Furthermore, the chosen process was the most appropriate for this experiment and thusly eliminated any possible errors involved with the procedures. Though this experiment yielded results that are credible and are of good quality, there are multiple methods that I could have taken to improve this experiment. A weakness in this experiment that multiple trials were not conducted. Although I did have three different Petri dishes for each of the four independent variables, I simply tested the four variables out of one common household. To have a better comprehension of the data, I should have ventured out to test other households. This weakness is very significant, and could have dramatically altered the results, possibly inviting a couple of outliers, and a change in the order of cleanest to the dirtiest. Another weakness in this experiment, also highly significant as the last one, was the fact that I only tested four areas that were concentrated in either the kitchen or the bathroom. To retrieve a better representation of a common living area and to overall improve the experiment, I should have extended the experiment to other areas such as the living room, study room, garage, the attic, and the master bedroom. Spreading out the areas I would have tested could have too altered the results severely. ?? ?? ?? ?? 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Biology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Biology essays

  1. Marked by a teacher

    Neurology and Behaviour. Focus question: Is there an increase in the perception and ...

    5 star(s)

    (Ts-Si, n.d.a) This variance in the raising of male and females can lead to the higher disgust rating in girls as boys seem to be raised in a way in which they are more exposed to dirtier items whereas girls are usually encouraged to be clean and tidy.

  2. Should Animals have the same rights as Humans? Both animals and humans exhibit behaviours ...

    However, if something is out of place, they will wake up totally and put it right before being able to go back to sleep. Many new mothers allow their baby to fall asleep in their arms and then put them asleep into their cribs.

  1. Stimuli and Response. Investigation Question: How do different tempos of music affect response ...

    8 in C Minor (Movement 2) Happy, relaxing Violin Concerto No. 2 in E Major Upbeat, regal, playful Piano Sonata No. 8 in C Minor (Movement 3) Quite upbeat, minor, fast Symphony No. 5 (Movement 4) Fast, loud, grand, over the top with drums, sounds like Soviet Russia Piano Sonata No.

  2. Research Question (RQ) How does the position of the arm (cuff) in relation ...

    Table 1: The Systolic (SYS) and Diastolic (DIA) Pressures (mmHg) of the subjects' for varying positions of the monitored arm Name Trial Test 1 (directly above head) 2 (at heart level) 3 (down by side) SYS (mmHg) DIA (mmHg) SYS (mmHg) DIA (mmHg) SYS (mmHg) DIA (mmHg) Subject 1 1 171.0 105 151 60 165 89 2 170.0

  1. Biology Extended Essay 2009

    scurvy; bleeding and swollen gums, wounds and bruises that do not heal.5 Ascorbic acid is very sensitive to chemical and enzymatic oxidation. During food processing, cooking and storage is the period where its content can be loss by coming in touch with oxygen.6 This suggests the reason for depletion of Ascorbic acid content over time in freshly squeezed orange juice.

  2. LAB-What infuences blood pressure

    83 125 80 120 80 30 + 90,9 178 92 120 85 120 85 31 + 57,8 171 72 115 75 115 75 32 + 70 176 79 115 80 120 85 33 + 58,7 161 75 100 60 100 60 34 + 64,7 170 77 + 125 75 120

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work