Science is a dynamic subject and it changes all the time. In the science field, research is always on going and when new evidence are discovered about a particular topic, the new evidence are usually used to update the scientific information that is already on ground. All the areas of science listed about have enjoyed scientific updates in the recent.
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I feel it's to easily differentiate the positive from the negative...... like in gram staining of bacteria, the colour tell us which bacteria is gram positive or gram negative...... I just feel that this is science and it is advisable to know what the opposite result of an experiment should look like.
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The plant is photosynthesizing and using up the CO2.
