Leah.J
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In one of the past papers there was a question that asked us to investigate the effect of pesticides on the heart rate of daphnia .
My question is, do I put the daphnia in the pesticide or do I add a few drops of the pesticide to the daphnia ?
Because there’s a mark for the immobilization of daphnia and I don’t know how we can do that if the daphnia is in a solution
But there’s also a mark for the acclimatization of the daphnia in the pesticide and I don’t know how we’re going to do that if we add drops of the pesticide to the daphnia.

Please help me I’m confused
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AzureCeleste
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Add pesticide to the solution the daphnia is in.
Give time for the daphnia to acclimitise to its new environment and then see if it dies or not (further investigations could be done as to what concentration of pesticide would kill the daphnia).
Don't put the daphnia in the pesticide- how will it survive considering it lives in water?
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Leah.J
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(Original post by AzureCeleste)
Add pesticide to the solution the daphnia is in.
Give time for the daphnia to acclimitise to its new environment and then see if it dies or not (further investigations could be done as to what concentration of pesticide would kill the daphnia).
Don't put the daphnia in the pesticide- how will it survive considering it lives in water?
THANK U but What solution should I put the daphnia in ? Just pond water ? And how do I immobilize the daphnia in this case ? I don't want it to die I want to measure it's heart rate and that would be difficult if its moving.
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AzureCeleste
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(Original post by Leah.J)
THANK U but What solution should I put the daphnia in ? Just pond water ? And how do I immobilize the daphnia in this case ? I don't want it to die I want to measure it's heart rate and that would be difficult if its moving.
Just water. When you get them they come in bags of water- I kept mine in them. It's basically just pond water.
You get them on a microscope slide, leaving them in a little water on the slide and then it's quite easy to count it
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Leah.J
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(Original post by AzureCeleste)
Just water. When you get them they come in bags of water- I kept mine in them. It's basically just pond water.
You get them on a microscope slide, leaving them in a little water on the slide and then it's quite easy to count it
Ooo do I count the heart beats under a microscope ? Would that damage them ?
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AzureCeleste
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(Original post by Leah.J)
Ooo do I count the heart beats under a microscope ? Would that damage them ?
That's how I counted their heart beats?
No? What do you mean by would it damage them?
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Leah.J
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(Original post by AzureCeleste)
That's how I counted their heart beats?
No? What do you mean by would it damage them?
Because they're exposed to bright light It doesn't matter. Just to make sure of this, I'm investigating the effect of pesticides on the heart rate of daphnia . Which of the following should I do ?
A) Get several daphnia of the same species and from the same source. Put each on cotton wool on a microscopic slide to immobilize it and then use a pipette to add the same volume of each pesticide to a slide ( one pesticide on one daphnia ) Allow the daphnia to acclimatize in the pesticide and then count the number of heart beats in a set time for each.
B) Get several daphnia of the same species and from the same source. Prepare five test tubes with the same volume of pond water and add the same volume and concentration of the different pesticide to each test tube seperately
Control the temperature using a water bath and then add the same number of daphnia to each tube to allow them to acclimatize . Then Put each on cotton wool on a microscopic slide to immobilize it and measure the number of heart beats in a set period of time
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AzureCeleste
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(Original post by Leah.J)
Because they're exposed to bright light It doesn't matter. Just to make sure of this, I'm investigating the effect of pesticides on the heart rate of daphnia . Which of the following should I do ?
A) Get several daphnia of the same species and from the same source. Put each on cotton wool on a microscopic slide to immobilize it and then use a pipette to add the same volume of each pesticide to a slide ( one pesticide on one daphnia ) Allow the daphnia to acclimatize in the pesticide and then count the number of heart beats in a set time for each.
B) Get several daphnia of the same species and from the same source. Prepare five test tubes with the same volume of pond water and add the same volume and concentration of the different pesticide to each test tube seperately
Control the temperature using a water bath and then add the same number of daphnia to each tube to allow them to acclimatize . Then Put each on cotton wool on a microscopic slide to immobilize it and measure the number of heart beats in a set period of time
Oh yeah, with the light you keep the brightness as low as possible and only have the light on when you are counting their heart rate

Personally when I did this (but with caffeine). I made up solutions of caffeine of different concentration (like 0.1%, 0.01%, 0.001% etc.). Placed one daphnia on the microslide and removed all water surrounding it before quickly adding a couple of drops of the caffeine solution. I let it acclimitise for about a minute or so and then measured its heart beat acoss a period of 5 minutes
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Kinyonga
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Poor things
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