in today's video we're going to run through everything you need to know about binary vision which is the process by which prokaryotic organisms like bacteria divide and reproduce so we'll cover how binary fission works and then how to do calculations to figure out how quickly bacterial populations can grow now just before we start i want to make clear that binary fission is not the same as mitosis or meiosis these are processes that happen in eukaryotic cells whereas binary fission is for prokaryotic cells like bacteria so if we start off with a single bacterial cell we can see that they have a cell wall a cell membrane cytoplasm a large circular strand of dna that contains all of their important genes and then a whole bunch of little plasmas which are also circles of dna but contain non-essential genes that only sometimes come in handy some bacteria also have a flagellum which is like a tail that they can use to move around but not all bacteria have one so as we said at the beginning binary fission is the process by which one bacterial cell like this one divides into two and the important point to understand here is that because bacteria are single celled organisms as well as being a type of cell division binary fission is also a type of reproduction because the one organism of the top has to split into two organisms so you might sometimes hear binary fission referred to as asexual reproduction now if we think about how binary fission actually works before a bacterial cell can divide it needs to do two main things first it has to grow a bit so that it's big enough to give rise to two new cells and then secondly it has to replicate all this genetic material so that there's enough for each new cell so it has to replicate its large circular strand of dna and then also replicate all of its little plasmids once this is done the two large circular strands move to either sides of the cell so that the offspring cells will end up getting one each the plasmids though are arranged pretty randomly so one offspring cell might end up getting more than the other then once this is done and is ready to divide it starts to grow a new cell wall down the middle of the cell which when it's complete allows the two halves to pull apart and voila we have two new bacterial cells the next thing we need to look at is how quickly bacterial populations can grow because binary fission is a fairly simple process it doesn't take very long in fact given the right conditions some bacteria can divide once every 20 minutes and because the population doubles with every division one cell becomes two two becomes four four becomes eight and so on so the population as a whole grows really quickly for example if these bacteria kept on doubling every 20 minutes for the next five hours would end up with a colony of over 250 000 bacteria when it comes to your exams you might be asked to calculate something like this for yourself so let's see how we do it for this question here a bacterial cell has a mean division time of 30 minutes how many cells would it produce after three hours and just to point out here that mean division time just means how long it takes to divide on average so it's saying that they can divide every 30 minutes so to work this out the first thing we need to do is figure out how many division cycles there will be in three hours which we can find by dividing the total time of three hours or 180 minutes by the mean division time of 30 minutes which is six so the bacteria will be able to undergo six rounds of division in the three hours next to figure out how many cells that would make we just take our original cell of which there is only one and then multiply it by two or double it six times which equals 64. so there will be 64 cells after three hours you could also have done it a bit more simply by multiplying the one by two to the power of six which is the same thing as multiplying it by two six times something to point out here though is that the mean division time will depend on the species of bacteria and the conditions that the bacteria are in for optimal growth bacteria like somewhere that's warm moist and has plenty of nutrients if they don't have these things then they will divide much more slowly or maybe not at all let's do one more question very quickly before we finish a petri dish contains 1 000 bacteria each cell divides once every 20 minutes how many cells will there be after four hours so this time would do the total time of four hours or 240 minutes divided by the division time of 20 minutes which would give us 12 division cycles and then because we started with 1 000 bacteria this time we'd multiply 1000 by two twelve times or just multiply it by two to the power of twelve which in either case gives us four million and ninety six thousand bacterial cells hey everyone amadeus here i just wanted to let you know that we also have a learning platform where you can watch all of our videos practice what you've learned with questions and keep track of all of your progress for the sciences and maths so if you haven't already you can check it out by clicking on our logo here on the right or if you'd like to do the lesson for this particular video we put the link to that in the description down below we've also arranged all the videos for this subject in a playlist for you here that's all though so hope you enjoy and i'll see you next time thanks