All living things react in some way to changes in their environment. This is what we call the interaction function and it is one of the three vital functions performed by living things. The others are nutrition and reproduction. We call these changes in the internal or external environment of an individual, stimuli. Stimuli can be physical, changes in temperature, pressure etc. chemical, the presence or absence of chemical substances or biotic, that is, produced by another living thing. The way in which a living thing reacts to the stimulus is called the response.
We have done an experiment to study how temperature affects cell division in unicellular living things.
Natural yeast is very easy to find in any supermarket and is a great way to obtain cells for experiments.Only one gram of this yeast contains billions of cells!
We dissolved some yeast in water and added some sugar. We placed a small amount of this mixture in the fridge and some in the bain Marie at 37ºC.
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| Yeast cells in the fridge |
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| Yeast cells in the bain Marie at 37ºC |
After a couple of days we took samples of both preparations and observed them through the microscope.
This is what we saw:
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| Cells kept in the fridge |
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| Cells kept at 37ºC |
We noticed a difference in the number of cells. Does temperature affect cell division? How do the cells react to the different temperature conditions? Can we consider this interaction? What do you think?. If we put the cells at a very high temperature, would they divide even more?
There are a lot of cells i the second picture. It is great.
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