Video: Evidence for Evolution (Part 2)

﻿Hello and welcome to this Oak National Academy Biology lesson. It's Mrs. Gibbs here. If you haven't done this already yet, please write the title. It's Evidence for Evolution part two. Now would also be a good time to remove yourself from any distractions. Ensure you're working in a way where you won't be disturbed, that your phone's to one side and you've closed any tabs that you may have open. That way you can give this lesson your full attention. Work your way through all of the activities throughout this lesson. And once you're finished, don't forget to do the end of lesson quiz. The equipment you'll need for this lesson is a pen and something to write on. If you haven't got that yet, please pause the lesson now, go get a pen and some paper or a notepad, come back and resume the lesson once you are settled. This is the second part on our two part lesson on evidence for evolution. Last lesson, we looked at how the fossil record provides evidence for evolution. Let's look at what we'll be learning about today. We'll be learning about antibiotic resistance in bacteria. Now that is actually evidence for evolution. And we will learn about why. We'll then learn about the development of antibiotic resistance and how we can prevent antibiotic resistance. Let's begin by looking at what antibiotic resistance in bacteria actually is. Now on the next slide, I'm going to show a picture and it's a little bit gory. So if you a bit squeamish, it's a good idea to look away now. And I'll tell you when it's safe to look again. You're ready? This image here shows an antibiotic resistant bacterial infection. So this person has been infected with something called MRSA. I've taken it off the screen now. So if you were looking away, it's safe to look back. So what was being shown there was somebody's arm. They had a wound but it had become infected and it become infected with a bacterial pathogen called MRSA. Remember pathogens will get into the bloodstream and if you've got a wound, then it's a lot easier for the pathogens to get in. MRSA is particularly common in hospitals 'cause obviously lots of people are going in with open wounds. MRSA is resistant to antibiotics. What that means is that it cannot be killed by antibiotics. It's really important that we say it's resistant and not that it's immune. So MRSA is resistant to antibiotics. It's what we call a resistant strain. And what cause that resistance to antibiotics is a genetic mutation. So antibiotic resistance is caused by mutations. Let's check your knowledge then. What's the missing word? Antibiotic resistance is when a species of cannot be killed by antibiotics. What type of infection was MRSA, what species? Three, two, one, tell me. Excellent, it's the species of bacteria. We should know from our infection topic that you would have done previously that only bacteria can be killed by antibiotics, not viruses but if it's resistant, then even antibiotics won't kill it. An example of a bacteria with antibiotic resistance is? What was that example we looked at? Five seconds, tell me the answer. Three, two, one. Perfect, it's MRSA. Now MRSA can not be killed by most antibiotics. So scientists have to develop new antibiotics to kill MRSA but it's continually developing resistance. And remember making antibiotics, antibiotics are a type of drug. It's a very long and expensive process. Next question. Antibiotic resistance is caused by genetic? What's the missing word? Tell me in three, two, one. Brilliant, genetic mutations. Remember genetic mutations is our first step of natural selection. I'd like you to pause the video to complete this task. Consolidate what you know so far. Resume the lesson, once you are done. How did you do? Pause the lesson. So mark and make any corrections and review once you are finished. So far, we've established that some species of bacteria are resistant to antibiotics, so they cannot be killed by antibiotics. We're going to learn about how that antibiotic resistance develops and it's actually through the process of natural selection. Let's take a look. For now you don't need to write anything down. So put your pen down so you can give the screen your full attention. We begin with a bacterial cell, which is on the left. Bacteria reproduce asexually which means they just copy their genetic material and then the cell will divide into two identical copies. Bacteria in optimum conditions and that means when there's the best conditions. So the correct temperature, the right levels of oxygen and nutrients, when they're in those optimal conditions, bacteria can reproduce as quickly as every 20 minutes. So that bacteria there, will copy its DNA and reproduce asexually. And very quickly there'll be lots of cells. Within seven hours, you can get millions of bacterial cells just from one cell. Look at the image though. Notice that two of the bacteria have had mutations in their DNA. We've learned about mutations before. Mutations changes to the DNA sequence and they happen when DNA's been copied and they happen randomly and continuously. Most mutations have no effect on the phenotype whatsoever. I want you to imagine here that that mutation there is a mutation for antibiotic resistance. There's usually competition within bacteria for oxygen and nutrients. So all those bacteria are competing and at the moment that mutation doesn't get the bacteria any advantage until the bacteria get exposed to antibiotics. Have a look now. Notice that all the other bacteria have been killed, except those with the resistant gene. They now have no competition for nutrients or oxygen. They have the survival advantage and those that are surviving will reproduce and pass on the gene for resistance to their offspring. And eventually all of the bacteria within the population carry the gene for antibiotic resistance. And that's how things like MRSA have developed. I said at the start of this lesson, that development of antibiotic resistance in bacteria is evidence for evolution by natural selection. Let's look at why. In an earlier lesson, we establish that the first stage of natural selection is variation caused by mutations. Well, the variation in this population of bacteria was some had resistance to antibiotics and some didn't and that resistance was caused by a mutation. Our next step of natural selection is competition. The bacteria in this example, were competing for oxygen and nutrients. The next stage is survival advantage. The bacteria once they were exposed to antibiotics, those with the resistant gene have a survival advantage. Only if they're exposed to antibiotics, if they're not, then it's not an advantage. It will have no effect really. But if they're exposed to antibiotics which they were in our example, those with the mutation for resistance, have the survival advantage. The others are less well adapted and they die. And our final stage of natural selection is reproduce and pass on genes. The bacteria with the mutation for resistance survived and we produced a resistance strain. That's what they're called, they're called resistant strain of bacteria emerged. Now this is evidence of evolution by natural selection, because this is happening all the time in the world. Antibiotics were only discovered back in the 1920s. Yet lots of resistant strains have emerged. Usually natural selection takes place over millions of years but because bacteria reproduce so quickly, it's possible to see that evolution happen. Let's check our knowledge. We're going to do a multiple choice quiz. And I want you to point to the correct answer. Let's have a look at the first question. A species of bacteria which has antibiotic resistance is known as a? Read the four options, 10 seconds. Point to the correct answer. Three, two, one. It's a resistant strain, excellent. Antibiotic resistance in bacteria is evidence for? Read the four options, 10 seconds. Point to the correct answer. Three, two, one, brilliant. It's evolution by natural selection. Remember it follows those four steps of natural selection. Bacteria evolve rapidly because? 10 seconds, point to the correct answer. Three, two, one, well done. They reproduce at a fast rate. Remember in optimal conditions, some species so E.coli is an example, can reproduce every 20 minutes. Well done on that quiz. I'd now like you to pause the video to complete this task. And resume once you are finished. How did you do? Pause the video to correct your task and resume once you're finished. So far in this lesson, we've established that antibiotic resistant strains of bacteria can emerge. It's part of evolution by natural selection. However, this antibiotic resistance is not a good thing. Antibiotics take years to get onto the market. And they're very expensive. And if there's resistance strains, those antibiotics become ineffective. It's really important therefore, to prevent resistant strains emerging. So let's look at how. Here's that diagram we saw earlier on in the lesson. We said that the mutation for antibiotic resistance would normally have no effect. Most mutations don't affect the phenotype. The reason it has an effect in this case is because of this stage here, the bacteria get exposed to antibiotics. If the bacteria hadn't been exposed to the antibiotics, then that mutation still would have arisen but it would have had no effect because they've all been in competition for nutrients and oxygen still. The mutation didn't arise because it was exposed to antibiotics. Remember mutations just happen randomly, therefore to reduce the emergence of antibiotic resistant strains, we need to reduce exposure to antibiotics. And there's several ways we can do that. Firstly, antibiotics should not be prescribed for non-serious illnesses. If somebody has an illness that they will recover from quite easily by themselves, there's no point in prescribing antibiotics. It might speed up the recovery but it would also increase exposure of antibiotics to bacteria. In addition to this, antibiotic should not be prescribed for viruses. So something like a cough or a cold which is caused by a virus should not be given antibiotics for. Remember antibiotics only treat bacterial infections. Another thing that could be done is complete courses of antibiotics. If you've ever been prescribed antibiotics, your doctor might say to you, complete this course for two weeks. And they'll give you two weeks worth of antibiotics. Sometimes people may start to feel better within a week. However, it's really important that that person still takes the antibiotics for the full time that they've been prescribed. The reason they'll start to feel better is the antibiotics will kill most of the bacteria. So the person will feel better because there's less bacteria releasing toxins. However, there's likely that there'll be a few which survive. The antibiotics dosage will be lower and that will provide opportunities for resistant strains to emerge. Another way to prevent resistant strains of bacteria emerging, is to restrict antibiotic use in agriculture. Agriculture means farming. Often animals within farms are kept in quite close confinement. So that makes it more likely for bacteria to spread between populations on a farm. So very often farmers will give their poultry or their cattle antibiotics and that will stop them getting bacterial infections. However, that also increases the exposure of bacteria to antibiotics. Therefore increasing the chances of resistant strains emerging. Let's check our knowledge. We're going to do a true or false quiz. And I want you to point to the answer as to whether you think it's true or false. First one, antibiotics should not be prescribed for viral infections. Is that true or false? Point to it. Three, two, one. That is true, well done. Antibiotics should not be prescribed for non-serious infections. Point to the correct answer. Three, two, one. That is true, well done. Again, we should not provide antibiotics for non-serious infections. Next one, patients should finish a course of antibiotics early if they feel well. True or false? Point to it. Three, two, one, excellent. That is false. Remember they should finish the course, even if they feel well. So that low doses aren't present in the system. Use of antibiotics in farming should be reduced. True or false? Three, two, one. Perfect, that is true, well done. Another one, increasing exposure of bacteria to antibiotics will prevent resistant strains developing. Give you a bit longer to read through that. Five seconds. Three, two, one. Well done, that is false. It's decreasing exposure. We need to decrease our exposure of antibiotics to bacteria. Excellent work on that quiz. Here's a practise exam question. There's six marks worth of questions here. Pause the lesson to complete the questions and resume once you are finished. Here's the answers to part A and B. Pause the lesson to mark these. And when you're ready to mark part C, resume the lesson. How did you do with part C? There's four possible answers and you need to have said three of them. Pause the lesson to mark your work and resume once you are finished. In this lesson, we've learned what antibiotic resistance in bacteria is. Remember antibiotic resistance is when bacteria can not be killed by antibiotics and MRSA is an example. We've learned how antibiotic resistance develops in bacteria. It's an example of evolution by natural selection. And finally we've learned about ways to prevent antibiotic resistance which all comes down to reducing our exposure to antibiotics, be in agriculture or in human medicine. That's it for this lesson. And you've been absolutely brilliant with all those quizzes and activities. Don't forget to do the end of lesson quiz by clicking on next activity. And I'll see you in the next lesson.

Worksheet: Evidence for Evolution (Part 2)

Exit Quiz: Evidence for Evolution (Part 2)

Completed: Evidence for Evolution (Part 2)

In this lesson we will learn about how antibiotic resistance in bacteria develops, and how this provides evidence for evolution by natural selection.

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Evidence for Evolution (Part 2)

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