So biology is a science.
I mean,
you're probably taking this course because you need a natural science, and so biology is one of those natural sciences.
But what is science, you know we all have this idea of what sciences the periodic table of elements,
you know, microscopes, beakers, and it's things that scientists do, you know? But what is that?
So what science is, if you want like a fancy definition, it's first of all -- it's a systematic study
meaning it's not all hand waving you know there's in order to do things
There's a way of doing things in order to make sure that you are doing accurate science.
So we have this study,
We're looking at the structure, so what things are made of and behavior,
how do things act, and it's not just animals, how do they act, but how do natural processes act of
Both the physical world, so think of physics, as well as chemistry, as well as the natural world which is our
biology and environmental biology. And
we do this study through both observations and experiment. So an observation, we're
looking at the world and making notes more or less, and an
experiment is when we're manipulating things.
And there's benefits to each, so observation and experiment, one isn't better than the other.
Now you have probably learned about the scientific method at some point in your life,
maybe it was in second grade at the science fair,
maybe it's a biology class you've already taken. And you may think I already know this, and I don't doubt that you do.
But I'm going to go over kind of a scientific method again.
Because it's incredibly important to understanding how science works and the science that I teach you in this class all
came from the scientific method.
So the very first step in science is actually really not science at all. It's just making observations,
noticing the world around you. Whether it's something outside, something in something under the microscope
it's just something you see.
So imagine these are two plants in my apartment, same species
it's the same type of plant,
and I bought them at the same time. And when I bought them they were the same size. Well looking at it,
you could probably guess,
or you could observe,
One is taller than the other. Something just as simple as that can start the scientific method.
So my observation is, you know, one of these plants is larger than the other.
Now you need to turn your observation into a
question and a question you can actually
test.
So for this example,
my question is why is one plant taller than the other -- I can actually test that.
But an example of a non testable question is
do boys or girls
like mint chocolate chip ice cream
more than
strawberry ice cream? You can kind of test that but it's all opinion.
It's not really
hard science, or you know what is the best ice cream flavor? Well, what are you defining
as best. Is it by taste? Well, how are you defining taste? So you need something that is very cut and dry,
something that you could actually run an experiment, and that's what we're going to do. So why is one plant taller than the other?
Now that we have a question that we want to experiment, we need to develop a
hypothesis. A
hypothesis is an educated guess, you've probably heard that before.
And what we mean by that is I'm not just throwing out random things,
oh, maybe this one is taller because I sing to it every day. Like,
no offense, but very bad hypothesis.
But you know plants, you know,
what plants need. So you could develop a guess based all the things you know about plants.
So I've already told you that the same plant and at the time I bought them
they're both the same size and so my question to you is why is there difference? And you would probably think the same thing.
So let's just try to think of what plants
like. I
Apologize how crappy this is going to look.
So sun, is one.
Maybe I have one in the window and one in my closet for some reason. Maybe water.
Maybe I just, like, really neglecting my plant and like oh, I really like this plant so
I'll give it water and I totally forget about the other plant sitting right next to it.
Think about again what other things do plants need, they need nutrients.
So maybe I'm fertilizing one, but I'm not fertilizing the other or fertilizing one more than the other.
Maybe, you know, I use two different types of soil.
So there might be different nutrients or different properties of that soil that makes one plant grow better than the other and
this list can go on and on. Just whatever you can think of that could be making one plant grow,
but the other not. And this is where science starts. You observe something and now you're making guesses as to
why that exists. So
we've noticed a difference. We've come up with a couple of reasons
why we think there's a difference, and now what we get to do is we choose one. We choose one of those to test.
So the one I'm going to choose in sunlight. If plants receive sunlight,
then they will grow taller. And you notice I have this if-then statement there, you know. If
my hypothesis, so if this guess, plants receive sunlight then:
here's my question which one will grow taller, so if they're receiving sunlight
they will grow taller. So this is the question that I'm going to test based on that hypothesis.
Now that you have a very clear question and a very clear hypothesis, we can conduct an experiment.
Now when conducting an experiment it is crucial,
crucial,
to have a control group. A control group is used to compare
between groups.
So if I were to conduct an experiment,
let's actually go to a new slide.
So my question again is that plants that are in sunlight grow taller, so I'm going to ...here is the sun
and
here's a plant.
Cool.
Plants that grow in sun grow taller.
Taller than what? Like, you can't just grow a plant in the sun be like, ah!
Definitely taller, ... taller than
Other plants? Taller than... bla bla bla bla? So the control group is something that you are
comparing. You need a comparison. Is it growing taller or would it have grown the same height if it was in the shade?
So I'm gonna cut a line down here, and I do suggest kind of drawing this in your notes and kind of annotating it.
So grow one in the sun, and I am going to grow one in
the shade. So here's the sun, and it's going to x through that.
And here's the plant.
So now if the one in the sun is growing taller, then
we now have something to compare it to, It is growing taller then plants grown in the shade or plants grown inside.
And so that's where
this control group, so again, this is the control group
is so crucial because you need something to compare it to.
But this is not a good experiment.
It's a good start, but we're not quite there. I
only have one plant in the sun and one plant in the shade.
What if the plant in the sun was like an abnormally short plant?
It's just like people,
some plants have genetics that make them short. It doesn't matter how many nutrients you give them, no matter how much sunlight you give them
they're going to be short.
Same with people. It doesn't matter how short you are, like if you eat more carrots unfortunately you are not growing any taller
Same thing with plants.
So when we test one plant, it's not enough.
You know what if there's some weird abnormal genetics thing going on in that plant?
So maybe I have these kind of weird plants, and they are growing taller in the shade. So you want to run
multiple trials.
So I am not going to draw ten, but just imagine there's like ten on each side. 10, 10 is a good number.
We call them trials, we also call them replicates, so
trial or a
replicate. Spelled just like replicate, but you pronounce it replicate.
So you're running multiple
plants, and this is incredibly
Important because again maybe random genetics will make some taller than the other,
so you're running multiple trials or multiple plants are multiple replicates you can kind of use all of those interchangeably.
Now we have a really good experiment.
Now I showed you in here
that we've got the sun.
That's what we're changing, so sunlight/no sunlight.
But what about water?
What about nutrients? What about soil? All these things that we said in the previous slide that could be affecting plants.
So what do we do with all those things? You know, we've got water, we still need to water our plants, we
still need to put our plants in soil,
we still need to give them fertilizer. NPK is the main ingredients of fertilizer.
What do we do about those? And here's, here's a very crucial thing, these must stay the same
between our two groups. If the plants in the sunlight
get a cup of water then the plants in the shade also need to get a cup of water. If the
plants in the sunlight are given
two cups of fertilizer every month then the plants in the shade need to be given a cup of fertilizer or two cups of fertilizer
every month. You can't change things. Why? This is very important, so make sure you're writing this down.
Why do they need to be the same? Well, if they're not the same that means if one planet grows taller than the other
It could be because of the sun, or it could be whatever else you changed.
It could be because you also gave them more water.
It could be because you also gave them more fertilizer.
And now we can't tell, we don't know which one of these factors is increasing plant growth. So in science is incredibly
important to test one thing at a time.
Now in our experiment, I
talked about a lot of variables, a lot of things that could change. We didn't change everything,
but we could change them. So water is a variable in our experiment --
we didn't change it, but we could have. Sunlight is a variable and in our experiment, we did change it.
So a variable is anything in your experiment that can be change.
Doesn't mean you did it, just means it could have been.
There's three different types of variables. The first one is called the independent variable.
This is the one the scientist is changing. This is what we are testing.
So in our case, our
independent variable
was sunlight.
We were changing
sun, so some plants got sun, some plants didn't get sun.
No, we weren't actually manipulating the sun,
but that was the variable that we changed in our experiment. Some plants got one thing, some plants got another thing.
So the independent variable is what we change.
The dependent variable is what the scientist measures, so this is
what we are looking for, so remember think back to our hypothesis -- if
plants get sunlight
then plants will grow taller, and that's what we're measuring in our experiment. We're measuring the height of our,
n this case, the height of our plants.
The dependent variable will
depend on the independent variable. If these plants are grown in sunlight,
then their height will depend on how much some may get or how much sun they don't get.
So the independent variable is what we are changing, the "if" part of our hypothesis and the
dependent variable is what we are measuring or the "then" part of our hypothesis.
All right, we have one more class of variables because we've got two more pictures on here: our water and our fertilizer.
Now in our experiment. We didn't change these, we could have but we didn't, we knew to do good science
you should only change one variable at a time.
These last set of variables are considered constants.
So the word constant means the same and that's exactly what it means in a scientific sense. Constants are
variables that we kept the same between our
experiment. So the plants that got sun got a cup of water and the plants that didn't get sun also got a cup of water.
So what you could see on the test is I could give you a scenario,
I could give you an experiment and I might ask you to identify
what's the independent variable the dependent variable, what are the constants? So be prepared for a question like that.
