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what are the controlled variables for this lab design?


NicoHatt

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Hello fellow IB students,

I am currently writing my Biology Internal Assessment Lab-design and I am struggling to determine the controlled variables in my experiment. I am writing about the effect of different temperatures on the ripening process of Bananas. (the ripening process in Bananas is controlled by different enzymes). Now my question is what would be the controlled variables in this experiment?

Thank you for your help!

 

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Think of it this way: there are lots of things that can affect ripening of fruit. You need to make sure you're changing only one variable at a time (temperature). I suggest you look at the other things which can affect fruit ripening (which will be your other variables - a simple google will get you started as to what these might be) and then consider how to control for them. Part of doing your lab project is identifying the variables so I'm not going to list them for you, but that's how you should go about picking them out. The idea of it is that when you do your experiment you're picking up only the effects of temperature - and not confusing it with the effects of, for instance, having one massive and one tiny banana.

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1 hour ago, Sandwich said:

Think of it this way: there are lots of things that can affect ripening of fruit. You need to make sure you're changing only one variable at a time (temperature). I suggest you look at the other things which can affect fruit ripening (which will be your other variables - a simple google will get you started as to what these might be) and then consider how to control for them. Part of doing your lab project is identifying the variables so I'm not going to list them for you, but that's how you should go about picking them out. The idea of it is that when you do your experiment you're picking up only the effects of temperature - and not confusing it with the effects of, for instance, having one massive and one tiny banana.

Thank you so much for your help! This is actually my first post on this page and I really didn´t expect such a fast answer. I did some more research and I actually found some great sources that list all the factors that affect fruit ripening. However, they also listed two factors that I have no idea how to control (exposure to ethylene gas and humidity). Do you think it would be possible to control these factors by placing my bananas in air-sealed plastic bags? :)

 

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No problem. 

Re: ethylene gas insofar as I'm aware this is released by fellow bananas so I would think that keeping them apart would help with that. 

I think keeping a banana inside an air-sealed plastic bag would affect both humidity and temperature - and at different temperatures it would increase or decrease the humidity, further complicating things. I think that just doing the experiment in an identical environment would control for air humidity. You can get humidity monitors and I wouldn't be surprised if your biology department at school has something along those lines if you want to monitor the humidity to demonstrate that factor is kept constant. Otherwise just the same room would seem reasonable.

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