biology design help

[maereth]

I have to write a design lab (a good one preferably) and as biology is not my strongest subject I need some advice. Our teacher recommended to focus on physiology and I was thinking about the effects of moderate physical effort on blood pressure. However, I found out that it should not vary that much in healthy people and I guess I can't make someone get like really tired can I? So would my hypothesis that effort increases blood pressure be valid in the first place? Or maybe I should assume that in healthy people it doesn't affect blood pressure and make it my RQ? Or both, one being research hypothesis, the other null hypothesis.

Plus, if it's a design and I don't need to actually do the experiment, do I have to suggest how much should the pressure increase to be considered significantly different or at least say "use statistical test to determine it"?

Any help would be appreciated.

[Jeanie15]

The most important thing to remember about design labs is that it doesn't matter as much about the lab itself as it does how you write it up! Your design is evaluated through the amount of error which is discovered in you lab report, so as long as your design eliminates error, all the other issues can be resolved through a good lab write up. Look on the biology page here and you can find a good resource for writing it up. Sorry I couldn't help more! Good luck! (I'm working on my lab write up right now!)

[maereth]

Thanks! The thing is, I cannot write a good lab on sth I don't understand and since I don't fully understand most of the biology, it's hard for me to do my IA's ;d I guess I will start with what I mentioned but if anyone could tell me which approach I should employ I would be grateful.

EDIT: so to simplify my question, if I make a healthy person make a moderate physical effort, say, go up and down the stairs few times or whatever ;d can I assume that his blood pressure will increase significantly and make it my hypothesis or will that be a wrong assumption? and how do I determine the significance of the results?

Edited January 20, 2013 by maereth

[Sandwich]

Yeah blood pressure shouldn't change much on exercise. Blood pressure is part of an equation with cardiac output (the amount of work your heart is doing) and what's known as total peripheral resistance (TPR). TPR is the resistance of your circulatory system to flow, so it's to do with how your blood vessels contract and dilate. When you start to exercise, your cardiac output (CO) increases but your TPR actually reduces as your body dilates blood vessels supplying skeletal muscle (obviously you want to increase blood flow to your muscles on exercise), so your BP remains relatively constant because BP = CO x TPR. Conversely, if you suddenly lost a lot of blood you would go into a state of shock and get a lot of circulatory constriction (i.e. TP resistance goes UP) in order to keep blood pressure high enough to perfuse your essential organs. It's a simple concept, really.

Heart rate would obviously go up and down with exercise, if that helps.

The main thing with experiment design is partly the write-up quality, as stated, but you DO also need to have a high quality experiment. This means identifying all the variables and controlling as many factors as possible. If you just identify a load of variables and then when you get rubbish non-specific results say "it's because I did not control for age, gender, amount of exercise taken per week, body mass index..." blah blah, then you don't really get points for that because YOU designed the experiment so it's your fault that it sucks. You need to control as many variables as it's physically reasonable to - then after that, by all means blame un-controllable variables for your results.

[maereth]

hi, I have another question about the design This time it really will be the last one and my teacher advised me to go for physiology again, saying that nervous system can be easy to write about. The only thing that came to my mind was how fast we will react on sth, how fast we catch the ruler for example, measuring the reflex basically. However, I suppose that what can influence this would be coffee, diet, fatigue... Again, I don't know what I'm allowed to do, how can I manipulate any variables here? Or maybe I should come up with something better? The problem is, my teacher is no help and she can't even explain anything properly so I don't know how to write a design after 1,5 year in IB so please, could someone tell me what to do...

[Sandwich]

What was wrong with just doing Heart Rate? Much easier.

[maereth]

I did it and got 3, now I need to do one more. Btw, my teacher said it's too easy and that I can't write abt sth if I know the answer at the beginning and that measuring blood pressure before and after physical effort isn't manipulation... So like I said, I don't think she has any idea what this is all about ;d

And people that did the heart rate heard the same: too simple. And she doesn't want anything about blood anymore.

Edited February 16, 2013 by maereth

[Pallavi]

hi, I have another question about the design This time it really will be the last one and my teacher advised me to go for physiology again, saying that nervous system can be easy to write about. The only thing that came to my mind was how fast we will react on sth, how fast we catch the ruler for example, measuring the reflex basically. However, I suppose that what can influence this would be coffee, diet, fatigue... Again, I don't know what I'm allowed to do, how can I manipulate any variables here? Or maybe I should come up with something better? The problem is, my teacher is no help and she can't even explain anything properly so I don't know how to write a design after 1,5 year in IB

For the manipulation of variables: You could pick out 3 groups of people- 1st group could have a diet rich in fats, 2nd- rich in carbs and 3rd- rich in proteins. You could then see how each group reacts to a certain thing. Let's say "how fast they can catch something" and you could talk about levels of lethargy in your qualitative analysis. However, there are lots of limitations to this: way too many external and genetic factors like metabolism, how strict they are with their diet, etc. This may only work as a design. You also have to make it extremely detailed and make sure you try and control every aspect from what they drink and eat outside to picking out candidates who have similar physical make-up (again, not so promising).

You use lab mice instead of people and probably see how fast they react to a particular stimulus. (You could just do a design on it if you can't get access to lab mice).

[maereth]

But is it permitted to do such things that you make people eat/drink sth? Also, the design has to be something I could do at school even if I'm not planning to. Plus IBO wouldn't like the experiment on animals I suppose

Edited February 16, 2013 by maereth

[Pallavi]

Yeah, fair enough. Or, how about something on touch receptors? We did this in school, so I'm sure it's possible. We took different objects- one was quite sharp (one of those geometry box materials), one slightly sharp and one quite blunt. We then poked people (subjects) with it (it wasn't dangerous since we didn't apply too much pressure). The experiment was to see the amount of time that it takes to feel pain or discomfort to such a stimulus. Like some people react immediately whereas some actually took quite a lot of seconds.

I'm probably making this sound a little risky but if you ask your teacher, she'd tell you the exact method and safety precautions. This one is definitely something that is acceptable by the IB because I've seen labs on this from previous years.