[Music] Hello, welcome back. We are going live once again, units 5 through 8 this time for AP Biology. Hello, I'm Melanie King. I'm from the Absolute Recap, Ultimate Review Packet, the podcast, The Exam Slayer, wherever you happen to know me from, I'm happy that you're here. We have a lot planned tonight and we're going to do this in about an hour which means what 12 to 15 minutes per unit. It's going to be fast, but please participate in the chat. Make sure you're subscribers so that you can type that in. Ask your questions. We're going to get to as much as possible tonight. Before we get started, however, um this is called affectionately the binge because we are going to go through this so quickly and there's a lot of topics and content to cover. In order for you to get the absolute most out of this review, I need you to do me a solid. All right, go grab the accompanying guided notes. They're totally free to download. This QR code will take you there. is going to take you over to the ultimate exam slayer so you can print, download, get a copy of these guided notes because the best way to go about this studying is with some active practice. And I know that seems a little silly at this stage of the game. You're like, I just want you to tell me the answers and I will go through a lot of them. But the chat on this is not going to save. Although the video will save to YouTube. You can rewatch it later on and pause it as you need to to go back through some trickier concepts. But I need you to go grab this particular document and I'm going to show you exactly where it is if you were to log in free account for the ultimate uh exam slayer. And this is exactly what it looks like. So once you log in, you're going to see different sections, introduction, all the different resources we have, some videos, um some background things, speed review, binge review guide, the simulator practice, my one pager skills practice, so many things. go down to where it says live exam review and you're going to see the 1 through 4 which has already happened. You're also going to see the guided notes for 5 through 8 live. That's what this one looks like. YouTube link for your reference and then all of the different presentation pieces on the lefthand column and for you to take notes on the right. One of the other things it's going to have in here are these learning objectives and things that you don't have to know. And I'm going to reference those a lot tonight so that you can kind of like cut out some extra studying for yourself. Things that you can just not waste your time with going over. This perhaps might surprise you because certain teachers um they do emphasize really their favorite topics in class. And I don't blame them. I have my favorite topics, too. But the College Board, it cuts out some content for you. So, we want to make sure you're not wasting your time in these final what eight, nine days. It's so soon. Fifth is going to be here before you know it. Um, and so it's a couple pages long as you can see, but go on over, grab this resource for yourself, and I think that you will be more than glad that you did. Um, so you can be better prepared. Again, it's totally free. Just make an account. You can use your Google. Um, and that will that will make it happen for you. But before we get started, where are you from? Um, if you see, where is it? Here. We are from Philadelphia just outside the city on the east coast. So it's nine o'clock here. I know that our particular people who use our resources, you're from all over. Um and so whether you're an international student or you are um studying independently, that happens a lot for for our students that that work here. Um we're we're happy that you found us and that you're able to study AP bio with the things that we provide for you. Hi Dallas. long way away. Um had a little bit of Dallas weather here today. It's about 75. It was It was beautiful. All right, we're going to do five through eight tonight. Um heredity, gene expression, and regulation, natural selection, and ecology. Now, some teachers actually start the year, tend to start the year with seven and eight. I'm not one of those teachers. Um but if you happen to do that, things might have been a little flip-flopped and reversed for you. Um this is going to be excuse me. um in normal sequence if you will. If you happen to miss units 1 through 4, you can go back and watch that. No problem. All the resources are there for you. Download again from either the Ultimate Exams layer or the review packet. Okay. So, we're going to zoom in. Uh, famous monk started a garden, and that's why we have the heredity chapter all of your learning objectives that you do not have to know, but um, so not you do have to know them. However, uh, they're listed for you in your review guide. So, not going to go into them in great detail here, but anything about reproductive cycles, whether it's plants or animals, is not required of you. They might be in questions, but they have to give you enough context. All right, I'm going to pause here for a second and see what you remember. Anybody know any of these letters so that we can collectively label our diagram. I need to talk to my uh science colleagues here. I apologize. So many of our vocab words in this unit begin with the letter C. All right, I see a lot of good words in the chat. I see sister chromatid, centromeir, chromosomes. Uh, clearly we see that familiar X shape, right? This X shape that we see during some stages, and we'll go over those some stages of cell division. Um, but in order to get this a little bit more clear for us, let's go over to our answer key. So, if you have the study guide with you, make sure to add your labels or you can go back and do this afterwards if you rewatch the video. These are chromosomes that are specifically already in their duplicate form, right? Duplicate form. So, A is a duplicate chromosome. So, is the adjacent chromosome next to it, which means that they've already gone through the Sphase of the cell cycle. They've already copied their DNA connected at their centromeir. They are going to be identical within the chromosome. However, they are going to be similar homologous to the chromosome they pair up with when we become a diploloyid cell. So, this means that they have similar instructions for genes. They do not have identical genes between the one chromosome and its homologous pair. We got these pairs from sexual reproducing organisms. They came from our parents um alone. Yes. Who else is sick? I apologize. I'm over here with a cough drop. I'm going to do my best. So, if you don't hear me for a minute, I went on mute so that you wouldn't have to hear me coughing. All right. Going into meiosis. Lot of terms that we have to cover and we want to make sure that we can separate these out from one diagram to the next. All right, let's look at diploid and hloid. So diploid referring to 2n that's going to have a full set of chromosomes. I would have my homologous pairs in that circumstance. But if I'm in normal cell functioning, I'm not going to have the X shape that I'm familiar with. Here we're looking at cellular division that's about to start. And so because cellular division is about to begin, DNA has already been duplicated. When we go through in this stage meiosis, the goal of this cell division is in fact to create hloid cells. And these hloid cells are going to have half of my amount of chromosomes. So because they have half of the amount of genetic information, they're going to then be prepared to pair up during sexual reproduction. Those hloid cells that you see at the bottom right hand corner of this screen, they've not yet fully differentiated. So these are just like raw hloid cells. They have half the genetic information. They would have to go through some sort of cellular differentiation in order to get prepared for actual reproduction. Looking at some of these other terms, the difference between homologous pairs and sister chromatids, we already mentioned sister chromatids are identical copies. They're produced during the Sphase. Homologous have similar information, but they're not going to be produced during the Sphase of the cell cycle. Crossing over that occurs during prophase 1 when we have an exchange of genetic information. That's going to create new recombinants of genes that passes on a chromosome that actually didn't exist in the prior parent. This however does not increase genetic diversity of the gene pool just of the organism itself. So that's one important distinction feature to make. When we look at chromatin verse chromosome that's going to depend on what phase am I in? How condensed and how coiled. Most often DNA is found in chromatin form the loosest form innerphase. You should not be able to see one chromosome from another during these phases. All right, raise your hand if you love genetic problems. I am one of the people that really likes genetic problems. Um, please don't be intimidated by them. You want to look for patterns. And when you think you've solved the problem, go back, read the question again, and ensure that you've actually addressed the question. So, was the question asking about um percentage of phenotypes? Was it asking about percentage of genotypes? Was it talking about something in the F1 versus the F2 generation? All of those different components matter. So, be mindful of that. When you think you're finished, don't just stop and move on. Reread the question and go back to look for that. Common patterns we have are diehybrid cross or 9 to 3 to 3:1 to look out for. Um, we have to be aware of our Mendle's laws whether it's segregation or independent assortment and when that's um what that's referring to. So independent assortment means that chromosome pair number one has no impact on chromosome pair number three. They're going to separate how they like. Segregation means that they just are going to separate. Now this may not always happen and that's when we end up with things like non-isjunction and you're going to have um an incorrect ployity within your final cell. All right. Here we have a sample problem. Sex linked recessive disorder. I'm looking at color blindness as my example um represented by my C as a superscript. This is sex linked recessive. And so sex link recessive is going to allow you to follow through your pattern. Things to be mindful of. A sex link recessive disorder does not need to inherit two copies if you are in fact male. So if you only if you are male and you have one X chromosome that means you are hemious for this disorder and you would express it which is why many males who have will express sex linked disorders more frequently. All right. So, we are going to pivot over. If you were in the unit one through four, we're going to pop over to um the exam slayer so I can show you what some of these practice questions look like. And in the interest of saving my voice, I am going to allow you some time to think before we in fact go to this section. Um, and so you will hear me be a little quieter um, at this moment so that I am able to save my voice um, and allow you guys to work through some of these questions. I'm going to give you about 30 seconds per question. And we're going to do two for Three. Okay, if this is your first time seeing the software, a couple things to take note. It looks super familiar, but I promise you not created or endorsed by the College Board or Blue Book. The counter at the top is in fact counting up. Um, and we can see our split screen here for the different stimulus pieces. You are also able to click show answer if you're not sure of what the question is or you want some extra support. If you choose not to hit show answer, you will still see all the answers and explanations on your printout at the end, which I will show you. Just like in the real exam, you can mark your question, skip around questions, strike out possible incorrect choices as you go through. I'm going to hit show answer so that we can see our response here. Things to take note of. All my F1s were blue. That's a really really big clue here that I must have some sort of dominant inheritance because not all my parents even showed blue. My third example here had pink and white. I still got blue in my F1. So the correct answer here is D because this is going to show you that this is inherited. There's a lot of red herrings in the rest of this information. It's not necessarily going to be most productive to the response. Let's look at another question here. A pedigree. I once had a student pause for a moment. I once had a student who uh gave up on learning pedigrees and just told me when they got a pedigree on the test, they were just going to guess. Please don't do that. Um if you know at least one or two inheritance patterns, just follow them through. Um and if it doesn't work for that exact example, move on. Okay? Just move on. Um that should get you far enough to at least make an educated guess. All right? Take a moment to look at this question and I will be back. All right. It's super possible that you might have known something about cickle cell inheritance from one of your example problems. But if we look at this pedigree and the way that it's expressed, circles for females, squares for males, anything shaded, that's going to be an expression. Not shaded will not. That circle that that first generation female offspring is not going to be affected and had a parent that was affected. That is your absolute clue that this cannot be dominant. You also see it skipping generation over on the right side of the pedigree. Another clue that this is not going to be dominant. So if I go here and look at what my answer should be, B is the correct response and my explanation down at the bottom. Um, as we're looking for that pattern of inheritance um that we should see here, you will have different ways in which these questions are referenced on the AP exam. Um, so just be mindful of that as you go forward. Um, that you'll see the questions kind of like marked out in different ways. Oftentimes in pedigrees you have your generation as Roman numerals and then you'll have individuals marked by cardinal numbers. That wasn't in this example. I'm a little surprised by that. This is from the 2013 release exam, but you know, things have evolved since then. It's been a long time since we've gotten some released AP bio questions. If you need more help on unit five, okay, the unit five summary video, totally free inside the ultimate review packet. It's also on YouTube, so you guys can go watch that there. And then I also have the study guides, the practice sheets, the multiple choice questions, all for unit 5 heredity content. So if you need some more support, go check those things out. But with that, we are already a little over 15 minutes through. We're going to already pop over to unit six, gene expression in your study guide. Here's your learning objectives direct from the CED. I've mentioned this twice. This is the course exam description. And you can find it freely online. I do also have it referenced inside the ultimate review packet and the ultimate exam slayer. You can pick that out. It's kind of like your cheat sheet for what is going to be the barebones, I say bare bones, it's not everything things on the exam, but it also does tell you what you don't have to know. So please, I beg you, don't memorize any of the enzymes for replication. Don't memorize the codon chart. If you need the mRNA codon chart, and you probably will, it'll be on the exam for you to reference. Um, you also don't have to know a lot of details of biotechnology. So, if you're really being bogged down by things like PCR, um, gel electropharesis, if these are kind of like, uh, bacterial transformation, maybe your lab went totally haywire, these are really, really, really small pieces of the exam. They're not big big pieces. Um, good question here. How should we learn the learning objectives? Um, the learning objectives are some really good checkpoint things. So if you are looking for like a way to selfreflect it's a good thing to go through and say can I do these things like can I explain one thing versus another. Um this is going to allow you to like separate out and at least compartmentalize the things you know and the things you still need to study. So it's a good like uh I would say last minute like checklist that you could go through um if that was an issue for you. All right, let's go back to the cell cycle. everything in gray interphase. That's when you see cells in chrom with chromatin. Now, it's a little counterintuitive because the Sphase of the cell cycle is where you copy your DNA. You're like, "Okay, so I copy my DNA. I form my X chromosome, but why don't I see it?" You don't see it yet because DNA has not been um made to condense yet. We Right, we've not gotten ready for cell division yet. So that wouldn't occur until the end of G2 preparing for mitosis which is going to be nuclear division. Cytochinesis is then going to be um cytoplasmic division right division of everything else. And just be aware again this process occurs differently if you are an animal cell versus a plant cell because you have to deal with those cell walls. So animal cells are going to go through cytochinesis from the essentially outside in as a pinching off process and then plant cells are going to divide from the inside out as you form a new cell plate. Oh G not sorry G subzero. Some cells go into cell cycle arrest. Um nervous system cells really good example of this. And so they in fact don't continue with their cell division. They can however under some circumstances be given cellular signals to trigger to go back into cell division. just depends upon um the way the cell communication is happening for that. All right, looking at our DNA molecule. Um so question here of where do I find the exam slayer? If you click on any of the QR codes that I had in the earlier presentation, just go back. That'll send you right over so you can um get your free account for exams slayer for sure. Looking here, uh, remember we're in a nucleic acid and specifically having monomers of nucleotides. This is DNA. It's antiparallel. If we think of the O of the oxygen as kind of like the roof of the house, the pentos, they point in opposite directions here. So, if I hold my arms up, um, if I hold my arms up in this orientation, I have one hand pointing in this direction and one hand pointing in this direction. They're parallel but antiparallel. um because I don't have them aligned with my hands facing the same direction. So that's a good analogy here when you're looking at the way these strands are also um shown. We are also looking at directionality because my carbon rings of my five carbons are going to be indicated um with my with my numbers. So the phosphate group attaches to the fifth carbon. I have the the third carbon having my hydroxil and that's what's going to form my backbone. The onep prime carbon is where I have my nitrogenous base and my nitrogenous bases are in the middle here joined by hydrogen bonds. So since there's two hydrogen bonds here, I know which two nitrogenous bases I'm dealing with. We have our single rings and we have our double rings, right? We have our purines and we have our perramdines. Perramines are single. Purines are double. Um and so uh guanine and adinine gold is always pure. Um that is going to be our purines. We have cytosine and thymine our perramitines. And so I can identify my nitrogenous bases on here just based on that alone. You don't have to know what's what. Meaning you're not going to be given a diagram and asked to identify nitrogen based on structure. Um but you should be able to distinguish between purines and primitines because of the way that they're um distinctive. So why does directionality matter for DNA? It matters because the same way that we uh in read in the English language left to right DNA polymerase as an enzyme reads three prime to fivep prime it synthesizes five prime to threep prime. So that refers to essentially how it's connecting the nucleotide monomers down the DNA sequence. So if I look here this is an example of ACMI origin site. I'm synthesizing in two directions simultaneously because I have two hilicases creating what is known as like a replication bubble. The green is an RNA primer and RNA we may recall uses uricil. So that will have to get replaced but it's going to give a binding site for my DNA pulase to attach my molecule and begin to synthesize. Things to notice I have a continuous synthesis following the enzyme helicase. I'm un separating out my my helix. I have discontinuous synthesis Okazaki fragments, small pieces of fragments with multiple RNA primers moving in the opposing direction. And again, that has to do with the fact that the polymerase enzymes, the enzymes that are doing the work, they only synthesize in the um five prime to threep prime direction. So there's not enough exposed essentially bases yet for them to work more continuously, which is why we see this like that. Okay, here's what I was talking about with my um with the codon chart. I'm going to block it. So, let me do that. Okay, with the codon chart, it's going to be provided for you for you to reference. Um and so, you always want to read it left, top, and right. the codon chart, the fact that it is universal, the fact that it has um multiple bases coding for the same amino acid, it gives you a lot of information about really the process of evolution, the continuity of working about errors. So if you make a mistake, the U right if there's a mistake in the process of the central dogma, it's less likely to have the wrong protein if they have this kind of like overlap built into the system. So, I have the answer down here for you in order to link up your amino acids. Um, noticing that mRNA also has directionality because it is also a nucleic acid, although singlestranded. Things to be mindful of when you're looking at something like this. When the transcript is made, right, the message is made, it's still in the same language, right? We've only written a shorthand. We've written it in RNA language, but I'm still dealing with nucleic acid language. when translation occurs at a ribosome, I'm changing the chemical language from nucleic acid over to a protein. And so that's why we are no longer working with our bases and we've switched essentially over. Now, depending upon where your m your mutation is, like where is the error? If the error is in the original DNA sequence, you're going to make the wrong protein every single time. If the errors in the mRNA transcript, like you just had a transcript production error, then it's likely not going to affect the outcome. You're just going to make a new transcript. Um, and this position within the uh codon matters. So, are you deleting a letter and having a whole frame shift because we only read three letters at a time? Have you inserted or have you just swapped the letter? Um, if it's a swap, a substitution, that has the least likely chance of an effect because you may end up with the same amino acid anyways. Let's just assume that you've made an error, you end up with the wrong amino acid, you're going to uh fold incorrectly, which means you're going to make the wrong shape, which means you're going to have the wrong function, and you're not going to be able to um allow this to be again a functional protein. Um, and so this is going to be an occurrence in which you have to be mindful of where is the error in terms of predicting the impact that it would have. We see these types of questions in the predict the effect uh often. If you need more practice, I have um a whole section on central dogma inside the URP for a practice video and as well as the practice sheet. This goes into repetitive motions of transcription and translation and making sure that you're comfortable um with using that chart. All right, replication and transcription have a lot in common um because of their processes because they are going to use similar enzymes um because they need to work with directionality in each of these components. Um the way in which it's accomplished does look different in proarotic versus ukarotic cells and that has to do with the lack of a nucleus. Right? So if you are working through transcription and you're proarotic, you can transcribe and translate nearly seamlessly and simultaneously, which means you're not going to have any sort of post-t transcriptional modification like you see in ukareotic land. Um the the polymerase is just named DNA to RNA. You're going to see the same directionality as it's going to synthesize, but RNA polymerase does not have the opportunity to proofread. So that's a big difference. terms of the bases, you have uricil being used in transcription. You're not going to see that inside the replication and you're not going to have any sort of lagging or leading strands on transcription either. We'll see that in replication. All right. Gene expression looking at the way um genes can be turned on, turned off and regulated does have a lot of variation. I'm make this a little larger for you to see since this is just text. Um does have a lot of differentiation. So on the proarotic side um this is where you see things like promoters and operators. Um on the ukareotic side you're going to have transcription factors. You're going to have like a groups and conglomerates of genes working um within that uh essentially forming this cluster of regulation in order to either turn on or turn off genes. And this is al often done as well with negative feedback. So what I mean by that is that in ukareotic gene expression you often see products of the uh gene expression actually turning off the gene expression and the reason behind that is really you don't want to waste your energy making a protein you don't need as a cell anymore and so we'll see that kind of flipping back and forth. So let's go over to the ultimate um exam slayer. We're going to practice again um with some questions. Move this. Put this back on. Okay, let's make it full screen once again to save my voice for a little bit. I'm going to um turn my mic off for about 30 seconds. Give it a shot. If you think you know, you can type it into the chat. All right, everyone seems universally wanting to choose B. So, uh, let's do it. And then hit we're going to hit show answer. Um, and well done. So, looking at the option for B, universal energy releasing process and we also have incorrect things, right? So, this is not true. We use aerobic and anorobic respiration. Um, convergent, this is not true. So, convergent implies that it would have had to have arisen independently multiple times and that's not going to happen. All organisms carry glycolysis and mitochondria. Uh, also incorrect. Where does glycolysis happen? This was a unit three concept, but do we know where does glycolysis happen inside of cells? Hopefully, that's something that we feel comfortable responding to. I'll wait for someone to pop it over in the chat. Um, I see it in the cytoplasm. Great job. All right, let's go on to our next question. Um, a new mutation arose and I want to mention we had a question about mutation in the chat. I'm going to come back to that after this question. So, turning my mic off for a few seconds for you to think. Okay. So before we get to this question, I do want to respond to the um something we had about mutation. So isn't cancer a type of mutation? Um so let's just look at this briefly. Cancer is uncontrolled cell division. So in and of itself it is not a mutation. It may be a product of a mutation. Um but you can have uncontrolled cell division of we'll say healthy cells. You can also have uncontrolled cell division of unhealthy cells or cells that they them they within them have a mutation. Um so it really does vary. Now the question might be well okay why do the cells divide uncontrollably? It has to do with the fact that they aren't being regulated within the cell cycle. they're not going through the standard process and checkpoints. So, there's something that's wrong with the regulation process within those checkpoints that tends to cause mut the the cancerous cells to form tumors. Um, so just be aware of that when you're using your uh terminology. It may not in fact be um what what you expecting to respond to. Okay. So clicking show answer here the correct answer was A and that was a good vote in the chat mentioning here somatic cells. Somatic cells are going to give you the same um the opposing to gamtic cells. So gitic cell is going to be if you were dealing with um the creation of a hoid gamt. Somatic cell is going to be referring to a body cell. Great job everyone. Quick halftime break. Everyone else can get a drink of water since I've been taking a break too. What other AP exams are you taking? I took AP bio in high school as well. Um I think AP AP US history. AP bio was a different landscape back then. I will tell you the CED was very different. So much more focused on microbiology now. Um but I know sometimes uh AP style questions can seem a little ambiguous. So how many cups of sugar does it take to get to the moon? Uh it's a quote from the Goofy Movie. If you're looking for a nice uh low-key brain break as well, um all I have to say is that the amount of APs that you take and you conquer is amazing. AB bio being 8 a.m. on Monday, first exam. Get it out of the way. Clean slate for the rest of the week is going to be um fantastic. All right, moving on to unit seven and populations changing over time. There are so many learning objectives and um again they are all on your guided notes. So if you haven't yet grabbed your copy, go grab your copy of the guided notes inside of Exam Slayer for free. Um but unfortunately there are no things they tell you you don't have to know in evolution. You have to know um all the things they have in the learning objectives. So definitely something to go refer back to. All right. So evidence of evolution. There's a ton of evidence of evolution, but I did want to point out a couple of really big kind of areas. Fossil evidence. Um, there's a ton things about uh intermediate fossils showing kind of like gaps in evolutionary history. You can have carbon dating. All of this is going to be relevant. The fact that the earth has changed so much, so biogeography, where living things are both found and have been found historically is going to give you information about how life has changed over time. You can look at things inside of organisms. So these are going to be components like homologous structures as well as vestigial structures like the remnants of DNA instructions from the past. Um and molecular so um molecular evidence is really some of the best evidence of evolution. It's also the more recent um parts of evolution. And so um these are really really important. So when I when we talk about um the the process of development, right? So I see someone mentioning embryology in the in the in the chat. Yeah, absolutely. So fogyny, the way that uh you have evolutionary history supported by embryological development, all of those are going to be relevant here. The the the theme of takeaway is that multiple lines of independent evidence po point towards the same evolutionary conclusions. And that's why um evolution is such a strong uh theory. So by in definition land, I'm not a huge fan of definitions to be quite honest, but um evolution is the change in alil frequencies in a population over time. And so population is a really important term here. And al frequencies is important just to reference here. It's not about just what you look like, the expression of those alals, but it's about the actual alals themselves. And so here we have our go to Hardy Weineberg. Um, and the things that have to be met in order for the alil frequencies essentially to remain fixed or locked in or evenly distributed, however you want to when you want to go about expressing that. Um, if you aren't familiar, Boseman has the five fingers of evolution. great video which explains this Hardy Weinberg process and the conditions that need to be met. Um, if you feel overwhelmed by Hardy Weinberg problems, the trick here is to go for the recessive first because that's going to be Q2 and Q ^2 can give you Q, which then works back to the whole problem. Don't set yourself up set yourself up in order to um be a little like box into solving an equation with two variables. That's not the strategy for Hardy Weinberg problems. If you need Hardy Weinberg practice, um, I have some in the math skills practice sheet. So, there's an entire math skill sheet inside exams player that walks through a lot of these areas. There's also math skills practice inside the ultimate review packet within every practice sheet. I saw someone ask about Kaiquare. So, Kaiquare is in here, too. Um, I also do inside the ultimate review packet. So, we're not going to go over Kaiquare tonight. It's going to be in the last bio binge, the one on Saturday night. um a small sample on Kaiquare if you're interested in that. All right, so I mentioned the word fogyny. Um and this is going to be uh really relevant to um all right, I'm going to pause for a second because I'm getting asked where can I find the exam slayer. So we're going to do this for you. Here's your QR code. There you go. Go grab it. Um that should get you there the fastest because I don't have the QR code up anymore. I hope that helps you um Alina. All right, looking at here with fogyny, looking at our cltograms, um the way that we place organisms out on their different branches, the way that we have our nodes, um couple things to be aware of. Just because the well here they're letters, right? So just because the letters are right next to each other physically on the diagram does not mean they're most closely related because any place you see a node could be like a swivel or pivot point and that would make it look completely different um but still give the same answer. So you want to think of this like organisms have walked along a path and branched. So when you're finding relatedness, go back to the most recent common node, the most recent common moment and that will give you your your place um of relatedness. So um you can only make these with so much evidence and depending upon what they provided for you like a character table can be used often to produce um phoggenetic trees depending upon the question. But we do want to look at some of this. So let's go over to um some practice questions um for this stage. All right, question five. I'm going to have to scroll a little bit for you here. Um, but it's exactly what I was referring to. We have a character table here showing nucleotide differences and five species of bacteria. Um, so the question here is which of the following filin trees is most consistent with the data. I'm gonna have to scroll for you so that you can see it, but I will um do that a few times as you look through the responses. This All right, it looks like a majority of people in the chat do want to pick C. So, let's do that. And then we'll hit show answer. And C is the correct answer. And let's talk about why. So, it's the correct answer because five is very clearly the out group. It's going to have um the most uh differences that we see here um with five. And then you have kind of clustered things together. and that we're seeing um some really three and four really close together, not a lot of differences. And then you have one and two and five is going to be the one that represents that data the best. Let's go to the next question. Oh, lovely. All right. DNA replication, which is going to be the most best example of the replication fork? I wish I can get all of them in here at the same time. Um Oh, maybe I can. Oh, there we go. All right, we're going to use process of elimination on this one. And I need to know what to get rid of. What to get rid of. So remember that's antiparallel. So I'm going to start here right off the bat. If we have things pointing in the same direction, there's no way that that's correct. A and B are not correct because I'm having synthesis in the same direction and that is not possible. So now it is which one is it? C or D? I'm seeing a lot of votes for D. So, let's pick it. Hit show answer. And D is the correct answer. And we're looking at this because D is the only one also that shows my Okazaki fragments. And so that's going to allow us to have um more representation here of the appropriate way in which leading and lagging strand are going to be expressed. Great job. Last unit and we have 15 minutes left. So we are right on time. I'm going to be honest, ecology is not my favorite. Here's the thing about ecology. Um it is a lot of information and technically you don't have to know any specific examples. That can make it challenging. Um, but if you've taken apes, that's going to be your your clue here. Here's your learning objectives and things you don't have to know. All right, I see help. my class hasn't done this yet. Um, okay. If your class never got to ecology, definitely watch the summary video. Um, you want to focus on some application questions. So, after you kind of get your your feet in the water with what ecology unit covered through a summary video, go straight to practice because you're going to learn the most by doing. And your biology kind of we'll say instincts, they're pretty good by this point. Um, and so you should have a except for some vocabulary that you might be lacking if you haven't yet done unit 8, your bio instinct should kick in with generally the right answers to most of these questions. All right, we have to be very concerned about energy flow in the ecology unit. Um, there's not enough to go around and that's why you have less organisms as you go on higher trophic levels. A troof or troth means feeding. And so when organisms feed or provide energy from um other levels, they're going to um take energy from that level. Generally, it's about a 10% turnover from one level to the other. And this is what organisms want to um obtain. They need to get resources. And these resources come in lots of ways, but energy is probably the ultimate one because you can't make your own energy. And I mean that authentically, okay? Even producers are not making their own energy. They're converting it from sunlight, from chemicals into a usable form. It has to come from somewhere else first. So producers are great, but they can't make it without getting it from somewhere else. So I mentioned that evolution occurs on the population level and so we have to distinguish between a population and a community because they're going to be competing for different things at each of these levels. The reason why evolution occurs at the population level is because that's where mating happens. And so if you are competing with members of your own species, mating and finding a mate, specifically if you are a sexually reproducing organism, that's going to be a piece of that puzzle. On the community level, you're in the same geographic area. You're also with other species. So you're going to be dealing with predation um as a component there, area, space, um at times different food sources. All of this is going to be something that impacts the success of your species. And that's going to impact how many of your species there are. Population size is going to change over time. Now, the graph on the left, exponential growth doesn't tend to occur in perpetuity. So, you might see something like that if bacteria reproducing. But in the natural world, exponential growth, it doesn't last long because resources run out or other um species move into the area. There there is a limiting factor. And that's why logistic growth, the graph on the right, tends to be more informative of how things are occurring. Your role is to be able to interpret things from graphs um and apply that to other circumstances. All right. So, we're going to do some practice for unit 8 and see how cozy we feel with these questions. Moving over to our exam simulator software. Two more questions. So, which of the following graphs is most consistent with the claim that communities with high diversity are more resistant to change than communities with low diversity? which are conducive to resistance to change. Species with high diversity are more resistant to change. What's our correct answer here? All right, a lot of votes for D here. So, we're going to select D. Before I select the answer um show answer, I do want us to think about why this is true. Like why do organisms um or why do communities that have more species richness, why are they more resistant to changes? And so this has to do with more occupied niches inside of that community um being filled. And so because there's more that are filled, we see it having this kind of um like all hands-on deck approach, I guess, is the best way I could express it um in order to survive if there's some sort of change within that particular ecosystem occurring. All right, let's move on to our last practice question here. Some of us are going, "I have no idea how to save the frogs. Why is this a question on the AP bio exam?" All right, we're all over the place in the chat. Let's look at this a little more closely. Um, which of the following human actions is most likely to improve the long-term survival of the amphibians? Okay, long-term survival. So, a cloning initiative is not going to work. It's out. Um, making the population size smaller by 15th. Uh, we don't want small populations. Large populations are going to be more resistant and have greater genetic diversity. Making a dam to control the flooding. Um, that sounds lovely, but I'm not quite sure how that would be super effective. Um, let's choose D and see how we did. D. All right. So, we want to uh make it so that they have some areas for breeding. That's kind of the best way to ensure that their genetic diversity is going to be um long lasting. Um, and so that's going to be what we want to say when it comes down to working with the frogs. just a general question about human impact questions. Um, we want to make sure that humans are the answer is never going to be that humans are doing something positive. Generally speaking, we tend to have negative impacts on the environment and most of the things that we do. Um, so just be aware of that when choosing your responses. If we sound like the heroes in the question, uh, it's probably not the answer. So to recap four units 5 through eight we had heredity gene expression to regulation natural selection and ecology going through many many themes. Now obviously this is not going to cover everything that you've learned this year. This is a super super brief overview of different concepts throughout. So if you need more help or you want to get more practice questions you haven't done the 10 free that I have. So, all the ones we've gone over in this in this live in the unit one through four live, those are all AP College Board release questions, the ones that are inside Exam Slayer and the ones that are in this free sample course, those are brand new, never been seen before. They've been written from scratch AP questions. And there's 10 of them for all of the subjects that we offer. Um, and so if you just want to get more practice and you want to just get 10 more free questions, sign up. You can try them in all the different um APs and that will allow you to um be more specific. So looking for more resources um that I have the podcast obviously also super free you can get any of the stuff I've have on YouTube any of the free resources side exam slayer ultimate review packet um will all be helpful for you we are going to go live two more times the next one is a full um is a practice test exclusively so we're going to do more strategy we're going to do um really like how to approach the question from the start so we won't be boopping back and forth between any content presentation and questions we're going going to go through a sample test together. I'm going to annotate and talk through. Um, we'll be doing less crowdsourcing of answers because I'd rather you hear how I would approach a question from the start. Um, and and as a compared to like seeing what everyone else thinks in the chat. But, um, that hopefully will help you notice the the red herrings, the pitfalls, the things that you the reasons you shouldn't pick some of these other choices, but they sound super good. So, I hope to see you there. It's going to be on the 29th, and then May 3rd is the final review. This is coming up really really um soon. Um all of these are at 9:00 p.m. Eastern Standard Time. Um so if you need to hit notify me on YouTube, make sure to do that. Um make sure to tell your friends. Uh you can also go back and watch the unit one through four later on. Um the practice test will also have some guided notes. So we hope to see you there. I really thank you for tuning in tonight and um hope you guys have a great weekend.