Micro-organisms are small (very small) living organisms that like the same things as we do: oxygen, moisture, food and an even temperature. Micro-organisms exist everywhere: some are harmful and even dangerous, some cause no problems and even help us (for instance in our digestive tracts).
We were looking at ‘friendly’ bacteria like yogurt and yeast. We investigated the effect of yeast when making bread. We made 6 different sets of bread rolls – ranging from having no yeast to too much yeast – and observed the effect. As you can see, the amount of yeast made a significant difference.
To make our investigation scientific, we kept the test fair by keeping everything else the same (same amount of every other ingredient, same method and same cooking time) and checked our results by repeating the test to make 6 bread rolls with each mixture. We then noted our observations in a table and discussed what we had learned about yeast from our investigation. Click the link to see a sample table.
This Science topic is ‘Micro-organisms’. We began by looking at viruses (extremely small organisms that cause diseases like measles, colds and ‘flu), fungi (moulds that cause diseases like athlete’s foot) and bacteria (microscopic organisms that cause infections and some diseases). We also thought about how to avoid or prevent the effects of harmful micro-organisms as well as the positive effects of other micro-organisms. For instance, we understand that although antibiotics can cure infections, they can also kill antibodies and friendly bacteria in our bodies.
We focused on yeast as it is a familiar and friendly micro-organism that reacts visibly when given the basic requirements – oxygen, warmth, water and food. To prove yeast is a living micro-organism, we put some dried yeast in a test tube and added some warm water and sugar, then observed what happened. Within 2 minutes, there were so many bubbles, the test tube was overflowing. To be sure that something was being produced, we repeated the experiment, but put a balloon over the end of the test tube. The balloon inflated, showing that a gas was present. We know this gas was carbon dioxide which is produced by living things during respiration.
