Leah.J
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When investigating the effect of temperature on the rate of respiration in seeds, what is the dependant variable ?
Is it the distance moved by the oil droplet ? Or the volume of O2 consumed ? Or the respiration rate ? And why is it one rather than the other ?
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macpatgh-Sheldon
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Hi, young lady (again!),
I am assuming this is the same experiment I did over 10 years ago [that tells you that I don't drink from a milk bottle any more [unlike some of us!!] - actually, I still drink a lot of milk - as you know, skimmed milk contains about 22g of protein/pint). You probs won't find this funny (sorry!) cos you are in deep slumber rt now!

The distance moved by the oil droplet is simply a reflection of the volume of oxygen used up, because this droplet is in the capillary tube, and is pulled along by the negative pressure created by the using up of the "air" in the tube (oxygen really).

Therefore, you can represent your rate of respiration by the use of either of these I.e. either oxygen consumption, or distance moved by the oil droplet, cos each is (approx.) proportional to the rate of respiration [unless you fudge your results as a lot of students do!], still with me? So you can plot EITHER the dist moved by droplet OR O2 consumption on your y axis.

Finally, your last Q is: "......or it it the respiration rate?" - now it is almost impossible to work out the actual respiration rate, as you do not know the ratio of the variables you are measuring to this rate, which is usually (that is, the ratio is) denoted by "k" in any such mathematical situation e.g. y = kt if you are comparing some known variable y to time t.

(pls ignore the text in italics if you find it confusing - this is just my being carried away by my Sheldon-ness!

See ya - I am going to make my full English now - about time, too!
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Leah.J
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(Original post by macpatgh-Sheldon)
Hi, young lady (again!),
I am assuming this is the same experiment I did over 10 years ago [that tells you that I don't drink from a milk bottle any more [unlike some of us!!] - actually, I still drink a lot of milk - as you know, skimmed milk contains about 22g of protein/pint). You probs won't find this funny (sorry!) cos you are in deep slumber rt now!

The distance moved by the oil droplet is simply a reflection of the volume of oxygen used up, because this droplet is in the capillary tube, and is pulled along by the negative pressure created by the using up of the "air" in the tube (oxygen really).

Therefore, you can represent your rate of respiration by the use of either of these I.e. either oxygen consumption, or distance moved by the oil droplet, cos each is (approx.) proportional to the rate of respiration [unless you fudge your results as a lot of students do!], still with me? So you can plot EITHER the dist moved by droplet OR O2 consumption on your y axis.

Finally, your last Q is: "......or it it the respiration rate?" - now it is almost impossible to work out the actual respiration rate, as you do not know the ratio of the variables you are measuring to this rate, which is usually (that is, the ratio is) denoted by "k" in any such mathematical situation e.g. y = kt if you are comparing some known variable y to time t.

(pls ignore the text in italics if you find it confusing - this is just my being carried away by my Sheldon-ness!

See ya - I am going to make my full English now - about time, too!
Helllo again , I'm in a deep slumber indeed
I don't think I understood the respiration rate thing
At my level, while incorrect or inaccurate, we can measure (and often have to find out) the respiration rate, is it still inaccurate to use ?
Or is it a rule that the dependant variable cannot be a calculated value, that it should be the measured ? I guess what I'm asking is, if I was investigating he effect of sth on the rate of sth ( too many somethings I know, please bare with me ) and to do that, I had to measure the value that is going to be divided by time-maybe distance or volume of gas
Which one in this case should I identify as the dependant variable ?
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HoldThisL
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the dependent variable is called dependent because it's value depends on the value of the independent variable

if you measure the effect on respiration, your dependent variable has to be caused by the seed respiring; that could be the volume of carbon dioxide consumed or it could be respiration rate - it's really up to you or your teacher as to which variable you measure
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macpatgh-Sheldon
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(Original post by Leah.J)
Helllo again , I'm in a deep slumber indeed
I don't think I understood the respiration rate thing
At my level, while incorrect or inaccurate, we can measure (and often have to find out) the respiration rate, is it still inaccurate to use ?
Or is it a rule that the dependant variable cannot be a calculated value, that it should be the measured ? I guess what I'm asking is, if I was investigating he effect of sth on the rate of sth ( too many somethings I know, please bare with me ) and to do that, I had to measure the value that is going to be divided by time-maybe distance or volume of gas
Which one in this case should I identify as the dependant variable ?
Good morning - I suppose mum is still frying the egg and sausages so you must be hypoglycaemic (Greek hypo = low; glyc = glucose; (h)aem = blood;............…...……
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