[Photosynthesis]
Roger: Hey Barbara, what lab are we doing today?
Barbara: Today, we're going to look at how different light sources
or even the absence or presence of light
affects the rate of photosynthesis in a cup of spinach leaves.
Roger: Excellent.
Well, we've got the right sensors and the right material.
Let's get started.
Barbara: Our carbon dioxide sensor is already calibrated
so we're going to put the sensor into the system.
Now it's a closed system with just spinach leaves and a carbon dioxide sensor.
Roger: I'll hit the start button, and we can see the rate.
Barbara: Let me turn on the light.
We're going to start with white light.
We're going to collect data for five minutes.
We'll speed through that data collection for you.
Roger: As we're winding up now towards five minutes, we can see a nice rate of CO2 is going down.
Barbara: Let's stop collecting data since we've got five minutes.
Because we have to keep the conditions the same in the next run, what we're going to
do is we're going to leave the light on, but we're going to wrap...
In case you're wondering why this foil is here,
we are going to use it to wrap the container
to keep the light from getting in while still having the light on
so we're only changing the one variable at a time.
We'll show you how to analyze the data once we've got it.
I'll give you some tips on how to analyze once we've got all the runs complete.
That should be good, I'm in just about the same position that I was before.
I don't want to put too much foil on.
I don't want to cover my sensor all the way
because I want that signal to get out of the sensor still, and that looks like I'm good.
Let's start collecting in dark.
Five minutes and we will speed up the data collection for you.
Roger: Excellent.
We got five minutes worth of data.
Let's go ahead and stop that.
Barbara: Roger, do you think you could rename the runs
so I don't get confused which was the light and which w as the dark?
Also, what happen to run one?
Why can't I see it?
Roger: You're going to notice we have run one and run two.
First thing I'll do is put those in, so you can see those both together.
Then, if I want to manage these guys, I can go to the tools down here,
and we can manage our runs.
We'll call the run one, and we're going to choose that to become "with light."
We're going to manage the runs again.
Barbara: While Roger is renaming that second run, I'm going to open up our system,
remove the foil, and let the bottle breathe a little bit before we do our next run.
We had white light in the first two runs.
We're going to do a third run now with green light.
Roger: Excellent.
Barbara: I wonder how that's going to affect the rate of photosynthesis.
Let's close the bottle and let it sit for a little bit to get itself back to equilibrium.
I think I need to probably reposition the light. I moved it when I turned on the button.
We can probably start collecting data now.
We're going to collect data for five minutes and speed through the collection for you.
Roger: All right.
Five minutes there.
I will save that run.
Barbara: While Roger renames that run, I'm going to switch to red light.
Interesting, I wonder what the difference we saw could be from.
There's my red light.
Oh no, I can't get it to go in the same place.
There.
Roger: There you go.
Barbara: OK, we got it.
Roger: All right, let's take a new run.
Roger: OK.
At five minutes, we'll go ahead and stop that.
Barbara: OK.
I can turn off my light now.
Roger: While she's doing that, I'll rename this one with "red light",
Manage the run so that we remember which is each condition.
Barbara: Then Roger will show you some of the tools that you might find useful
when asked to do the analysis.
Right now we have all the data, but how do you interpret it?
Here are some tools.
First, how do we see all the runs at the same time?
Roger: If you want to see the runs, you'll notice that we have checked on the last run here.
We can make sure that these others are also entered in,
and we can see all of those showing at the same time.
That's one way to make sure that we can see these.
If we want to do analysis where we would see the slope
of how fast the carbon dioxide is being produced per time...
Make sure you'll notice that there's a red box that's at the end.
If you want to start from just the general light, that was white,
and notice that if you look at the the light itself,
you'll notice it's also a larger light.
We didn't control all the variables that we could have,
but it's white and it has a certain rate.
If I want to come in here to my tools, notice I've selected that run with white light.
If I want to run the best line through that whole set of data because it looks consistent,
I'll put a linear fit on here, and we would look for the general formula of the line.
y=mx+b is there and you're looking for what the slope is.
In that formula, you're going to see that the slope, m,
is given by the number on the second line after the generalized formula.
That's what you want to compare in terms of talking about these different conditions.
Barbara: The rate.
Roger: Now, what is also interesting is you may notice that if I switched to my second,
then I can move this, too, so that I can still see what's going on with other ones.
I'll move this up to the top.
In the second condition, you may notice that it looks like there can be some areas
where there are some different rates.
Without light, I might be more convinced to say this towards the end
is more typical of that light.
Let's switch to that one.
If I don't want the total line, like the consistency of the green line looks the same all the way through,
perhaps I want to say, let's just look at the red light towards the end.
Then I'm going to need to select the green light.
Thank you.
The green light I think I'm more convinced that the end here was more typical of that light.
I'm going to use a tool here, that's the select a region.
I'll go in here and I'll draw a box around that region.
I'd say that seems to be to me more consistent for what I would use,
and you have to use those reasonings while you're doing your analysis.
We can continue to run that same slope analysis just for that area.
Then I can move this up and we can have a number m there, that is a much smaller number.
Barbara: Roger, what if I wanted to know the specific CO2 concentration or time
on just one point on the without light run, the one on the bottom.
Roger: Fantastic.
If I want to see specific points in this time, I have a tool that is a coordinate tool.
If I click on that, I'm still in the green light mode,
so I got the green light to show up.
If I don't want that to show up, I'm going to X that out by clicking once on the box.
Let's go into the without light mode.
I just want to see what that looks like.
I'll click on this again, and we'll choose some point in the middle of this line.
You can move along here to see what the lowest point was, for instance, by just moving these.
You can move the box here, but you can grab the box that's on the line itself
to find a spot in here to say what was the lowest value or the highest value
for whatever your analysis you would like to do.
Barbara: OK.
I think you've got everything you need to be able to do the analysis.
Good luck with the rest of your experiment.
Roger: Thanks.