AP Biology Labs - part 1

Hi. It's Mr. Andersen and in this video I'm going to go through the AP Biology labs. Actually I'm going to go through the first seven of thirteen AP Biology labs. I'm not going to go into too much detail. You may be watching this at the beginning of the year as you start to look ahead to the year. Or you might be watching it the night before the AP exam as you're reviewing all of the labs. The one thing you should know is that they've changed these labs to make them more inquiry. And what that means is instead of just following a cookbook lab, you're going to be the chef. And you're going to be designing parts of the experiment and collecting data on your own. And so let's begin with lab number 1. This in on artificial selection. In this lab, what I did in my class is we used fast plants. And so you plant these, it's called a brassica plant that grows really really fast. You can go from seed to new seeds again in less than a month. And so what we were doing is we're choosing which traits we want to pass on to the next generation. And you do that using what's called a bee stick, which is just a dead bee glued onto a stick. And what you can do is you can pollinate other flowers on other fast plants. And so in my lab what we were doing is we were looking at height. And so this is plant height in millimeters. And this is the number of plants in the classroom that each have different heights. Now you have to figure out what day I'm going to do that. So then what you do is you choose just the tallest of plants to breed for the next generation. So you're selecting those traits to move on. And now in second generation you can see that we're going to have much more tall plants at that same time period. And so what kind of selection is this? This is going to be directional selection. We're pushing this bell shaped curve to the right. You didn't have to measure height. Another one that a lot of teachers will do is trichomes. Those are going to be little hairs that are found on the fast plant. You can breed the hairier plants and you're going to a hairier population. So that's investigation one. Investigation 2 is on Hardy-Weinberg equilibrium. In my classroom we started with the bead lab where you would put 50 of each, of two different colors of beads in a cup. You shake that cup and you pull out two pairs at a time. And so we call that the mating chamber. Or that's simulating sex in this population. And what you'll find is that the equilibrium will remain the same. That's what equilibrium means. So the p and q values are going to remain the same throughout the whole experiment. Next thing you do is you do what's called selection. So if you pull out two of the homozygous recessive than you can kill those. And then you figure out the population based on the survivors. Another one you can look at is heterozygote advantage. And so you'll see a little bit of variance in the data, but as long as you're keeping those 5 constraints the same, so we've got large sample size, random mating, no mutations, no gene flow and no natural selection it should remain about the same. Now one thing they added this year is spreadsheet analysis. And so my students created this spreadsheet and then they used it to figure out a little bit more about Hardy-Weinberg equilibrium. So let me jump into excel. Okay so here's the spreadsheet. Let me kind of show you what's going on. These are the p and the q values. These are going to be gametes that are each created. These are the zygotes. And then these are the phenotype ratios down here. And so what I can do is I can just rerun the simulation. So let me rerun it. And watch those numbers in the spread sheet. And so it's recalculating everyone of of these cells over and over and over. And so what we're getting is starting at 0.5 and 0.5 but we're getting end p and q values that tend to change. And so let's look at those. So what's going on there? How does this spreadsheet work? Well let's dig into the formula a little bit. So if we look right here on this cell, so this is this cell right, if we look at its equation, what it's going to do is generate a random number from 0 to 1. And so think of a random number right now. Let's say 0.23. It's then going to take that number, 0.23 and if it's less than what's in here, so the 0.5, then it's going to put an A in the box. But if it's greater than that then it's going to put a B. And since these values are fifty-fifty, it's going to be about half on each side. Now why are we seeing changes? This is genetic drift. We have a small sample size and so you're going to see change. Let's change this value up here to like 0.1 and then this one to 0.9 and see what happens. Well now the chances of it being less than 0.1 are going to be really slim. And so we have less of those As. It doesn't mean that we don't have them, but if I recalculate this again, we can see variation in there as well. It's going to be mostly Bs. And so you can do a lot of cool experiments. So you could set it to 0.5 and 0.5. You could then run it. Figure out what my p and q values are and then set those for the next generation. So we could do it over and over and over again. And so again, why are spreadsheets great? They allow us to do really cool simulations very quickly. And it's much easier than pulling beads out of a cup. Okay. Let's get back to investigation 3. Investigation 3 what you're looking at is comparing DNA. And so this is a cladogram over here. It's showing pretty much the evolutionary history of these organisms. And what we used to use to do this was morphology. So the study of shapes. So we look at bone structure for example. But that's highly inaccurate. A much more accurate way to do it is to look at their DNA. And so in this simulation what we did is we came up with a specific gene. So this is human actin. We then did a blast search of the nucleotides. And what we did is we found out how related they are to other organisms. And so for me we took human actin and then we compared it to all the other organisms in the database and we were able to create a cladogram that shows how related you are to a chimpanzee, a gorilla even a panda bear. And so that's the blast analysis. Next one, investigation 4, is kind of a three part thing. It's looking at diffusion and osmosis. Step one, what we do is we take cubes. We're going to cut those cubes, first of all we make them using agar. That's going to be similar to what you find in a petri dish. And then we add a chemical to that called phenolphthalein. Phenolphthalein is going to be clear. And so these cubes are going to be kind of clear with a bluish tint. We then let them sit in sodium hydroxide. And as you let them sit in sodium hydroxide, when sodium hydroxide and phenolphthalein meet, when the pH changes, phenolphthalein will turn to kind of a reddish color. And so if you let it sit over night what you'll get are cubes, the bigger cubes, littler, littler, littler or smaller. The sodium hydroxide is going to move in the same amount on each of these. It's going to diffuse in the same amount but these cells that are really small, it's going to get to the center more quickly. And that's why cells are small. It allows diffusion to all the parts of the cell more quickly then it would if our cells were very large. Next one is another qualitative analysis. In this one we're looking at diffusion. So what you start with in this beaker is water and IKI. IKI is simply a source of iodine. So in here we've got water and IKI. And then we have a dialysis bag. And in the dialysis bag we've got water. We also have starch. And we have glucose. Now a way to figure out if you had glucose or not is to use test tape. So you put that into the solution and if it turns a color then you have glucose in there. So again what do we have in here? Starch, water, glucose. What do we have out here? Water and IKI. One thing I should tell you is if starch and IKI are ever in the same place it's going to turn kind of a bluish color. So what we then did is put it inside our beaker and let it sit. This takes about an hour. And what happens is this turns blue. And so then I asked my students to figure out which is bigger. Rank these things over here in size. Which is smallest? Which is largest? One other thing I should tell you is if we put test tape out here when we're done, we're going to find glucose out there. And so let's start with the glucose. There was glucose in the bag before. There's glucose after. So what do we know? We know that glucose got out. And so we know that that's going to be smaller then the holes in the dialysis tubing. Water would be hard to tell. We have to mass this to figure out if water is moving. But it is. And then the last thing is going to be starch. Starch is a polysaccharide. It's made of a number of different sugar molecules. If it would have gotten out of the bag the whole beaker would have turned blue. But it didn't. The IKI was able to make it in. And so we know that that's smaller than the pores in the dialysis tubing. But the starch is going to be bigger. And so the starch wasn't able to get out. The next one is going to be more gathering of data. You do this as an inquiry lab. And so what the students are doing is taking cores of potato and they are putting them in different concentrations of sugar water. And so you can see here that they're putting them in distilled water all the way up to 1.0 molar sucrose solution. And then they're measuring the percent change over night. So they let it sit over night. And what you'll find is in the 0.0 or the zero distilled water, the potatoes are actually are going to see an increase in their percent mass. And then on this side they're going to see a decrease. And this is a nice line of fit right here. So what you can see is where it crosses the line, that would be where they're isotonic to their surroundings. So that would be the solute of the concentration concentration of potatoes themselves. Next is number five. This is the photosynthesis lab. To do this lab, do this as an inquiry lab. What we do is we take little chads, so these are holes punched out of a leaf. We put them in a syringe and pull all of the gases out of the chad. And what happens to the chads is that they sink to the bottom of the beaker. One other thing we have to put in that beaker is carbon dioxide. And we do that using a little bit of baking soda. We then apply light to it. And what's going to happen is the light reaction is going to occur in here. It's going to breakdown that water. It's going to release oxygen. Those oxygen bubbles are going to build up and then this is going to float to the top. And so what we can do is we can time how long it takes for them to float to the top. Or we could choose 50 of them and see how long it takes for a certain number of them to reach the top. And we're measuring the rate of photosynthesis. And so in my class what we looked at was up to the students. Maybe the amount of light. The distance from the light source. The temperature would be another good one. The color of the light. We use filters to figure that out. And so this is kind of the procedure but then you try to figure out how does this effect the rate of photosynthesis. The next one in the respiration lab. In the respiration lab what we use is a respirometer which is simply a piece of or a tube of glass that's sealed up on both ends. Except on this top end you have it open. What you'll eventually do is put the whole thing under water. One other thing I should mention is that we put potassium hydroxide in the bottom. Potassium hydroxide will grab any carbon dioxide that's loose and turn it into a solid. And so what's going to happen as this thing is just laid down in water is that any or organism inside it, you could use germinating peas or we use worms in class, they're going to do respiration. So they're going to use the food or the nutrients inside their body. And they're going to take in oxygen to create energy, ATP. And so what you'll find is as they consume the oxygen inside the respirometer they produce an equal amount of carbon dioxide. But that quickly becomes a solid. And so the volume in here becomes less and less and less. Water starts to flow in and you can read the water flowing in on this pipette right here. So you can measure the respiration. And so this is what a graph might look like. It's going to be time along the x and then milliliters of oxygen consumed on the y. And this is quick experiment where they're looking at germinating peas vs non germinating peas. And then at different temperatures. And what we'll find is as you increase temperature respiration rate is going to increase. And the reason why is all the molecules are bouncing around more quickly. More likely to have reactions. Also if it's a germinating pea plant, germinating pea plants are going to require more energy. They're growing. And so that's going to require more oxygen. And we're going to see a faster rate of respiration. Remember you can always calculate the rate by figuring out the slope of this line. And that's going to be milliliters oxygen consumed per minute. In the worms what we found is since they're ectotherms, their respiration rate is going to change as we vary the temperature. So the worms at a warmer temperature are going to respire faster. Remember you're an endotherm so it's going to be a little different because you maintain a constant body temperature. And then the last one I'll talk about in this video is the mitosis meiosis. In mitosis, remember mitosis is the division of the nuclei more specifically. But sometimes we just mean the division of cells into cells that are identical. And so this is how all the cells in your body make copies of themselves. And so we use onion root. And what you're looking at is cells that are quickly going through mitosis. And you figure out what phase they're in. And so this would be some data where you count the number that are in interphase, prophase, metaphase, anaphase, telophase. So if we were to go through these, this would be interphase, interphase, interphase, interphase, interphase, prophase because we can see the chromosomes. Interphase, interphase, interphase, interphase, interphase, prophase. Let's see. This would be a metaphase down here. This would be an anaphase. They're pulling apart over here. And this would be a telophase right here. It's starting to form a new cell wall. And so what you can do is count all the cells under the microscope. This is our class data. And this is a pie chart of that. And what you'll find is they spend most of their time in interphase. And that's going to really mirror the cell cycle. They're spending most of their time actually growing. Copying their DNA and that whole splitting of the nuclei and then cytokinesis goes really really quickly. Second part of this is the meiosis lab. What you use is a fungus called sordaria. Sordaria has a dark and a light color. These will grow together and so you'll have spores from these two different types coming together into what's called a parathecium. And what they do is they do quick fertilization and then they do meiosis. And they're going to create all these spores here. The cool thing about that is that if it looks like this, the spore arrangement, four four or four four, no crossing over occurred. But if you get any of these four arrangements over here, crossing over occurred. That's how we get the mixing of these colors. And so what we can do is figure out the frequency of cross-over and that tells you how far the gene is from the centromere. So those are the first seven labs. I'll turn the camera off for a second and then hit the next six. And I hope that was helpful.