[Music] [Music] let's talk about how to do well in your IGCSE biology exams just like on most courses the best way to succeed is to learn every fact on the course understand those facts learn the skills and then be able to apply all of that if you can do that you are guaranteed to do well in your exams but let's get real some exam prep can really go a long way and can really boost your chances so what I want to present today are what I think are ten of the most common question types that come up in a GCSE biology exams I'm basing this on paper 1b that's the biology paper of the Pearson edexcel GCSE 9 to 1 specification but to be honest I GCSE biology specifications don't change that much whichever one you're studying so this is probably relevant to most IGCSE biology students there's quite a lot to go through and if you look in the description I've got some timestamps so if you just want to skip ahead of certain questions you can do that let's get on with it first up is the movement of substances this one comes in three parts and each of them are common in exams you might be asked to define the term diffusion for two marks the movement of particles will get you the first mark and from an area of higher concentration to an area of a lower concentration will get you the second one a common mistake is to say a substance instead of particle and that will usually lose you the mark for all of these movement questions remember that you're stating what moves and from where to where another common mistake is to say high concentration gradient which doesn't make sense you can add down the concentration gradient but that's not essential to define the term osmosis you need to state three marking points osmosis is the movement of water from a more dilute solution to a more concentrated solution through a partially permeable membrane forgetting the specifically state water is a good way to throw away a mark defining active transport can also have up to three marking points this is the movement of particles from an area of a lower concentration to an area of higher concentration using energy from respiration next is comparing arteries and veins there are four marking points and you only need three of them for this one arteries have thicker walls more elastic tissue a smaller lumen and they have no valves but veins do I often say students use the word they in these types of questions and depending on the wording of the question this might or might not be acceptable so just play it safe and name the blood vessel you're talking about also note that this is a comparison question so make sure you use comparative language like thicker rather than thick smaller rather than small etc [Music] another common question theme is the gas exchange system these usually get you to describe or explain the features of the alveoli a good example is explain how human lung tissue allows efficient gas exchange since it's an explained question you have to give reasons or justify each point rather than just describing the features firstly the alveoli provide a large surface area a state that alveoli are present and that's good for gas exchange because of the large surface area that's the explanation our viola walls are one cell thick and we then explained that this provides a shorter diffusion pathway alveoli walls are moist for gases to dissolve the capillary wall is only one cell thick again for a short diffusion pathway and the flowing blood maintains a concentration gradient be specific with these responses saying they makes it unclear what you're referring to and wold earn a mark and a very common error I see a student stating that the alveoli are one cell thick this is wrong it's their walls that are one cell thick [Music] next up is absorption in the small intestine explain how the structure of the small intestine is adapted for efficient exchange of substances the villi provide a large surface area and they have thin walls for a short diffusion pathway they also have many capillaries to absorb glucose the blood supply maintains a diffusion gradient and the villi have lacteals to absorb fatty acids and glycerol the lacteals are also long to give a large surface area just like the alveoli question don't write the villi or oneself thick it's their walls that are one cell thick the next one is genetically modified bacteria an example question is describe the stages that are used to genetically modify a bacterium that is able to manufacture insulin they could ask about manufacturing anything but in this case we'll focus on insulin regardless and the mark scheme should be really similar whatever the topic is firstly isolate the bacterial plasmids and there's a mark for acknowledging that these plasmids act as vectors open the plasmids using a specific restriction enzyme from a human sample extract the human gene for insulin or whatever the question asks about using the same restriction enzyme take that gene and join it with the bacterial plasmid using ligase forming a recombinant plasmid the next step is inserting the plasmid into the bacteria and from what I've seen they don't tend to a water mark for saying that regardless we could mention it to be safe [Music] next designing an investigation this may be specific to this specification but designing an investigation is an essential skill if studying the Edexcel IGCSE nine to one course and there's a specific mark scheme that's always used just think combs C or RMS C is for the thing you will change in your experiment or refers to the organism R is for reliability M is for the thing you will measure and s for what you will keep the same or constant there are often two marks available for M and s let's see an example design an investigation to find out if the color of light affects the amount of fruit produced by a plant let's start by listing the colors of light we could use this checks the change part grow to model plants of the same age under each light color we've now stated the organism and something will keep constant about it stating something you'll keep constant about the organism is sometimes needed for the omok grow five plants under each color those are our repeats four measurements will record the mass of two models produced per plant in one month we've stated what we'll measure and the timeframe so that's both of the M marks accounted for we should use the same light intensity for all plants and give them each an equal volume of water we've now listed two things will keep the same that's seven marking points and we only need six of them for full marks another common theme is stating variables it's common to see a question that presents an investigation and asks you to state either the dependent independent or control variables or maybe even all of them he has an example experiment a student conducted an experiment to find out how the type of light bulb effect the mass of fruit produced by a plant plants are grown under lamps with three different types of bulb incandescent fluorescent and LED here the dependent variable that's the thing we're measuring is the mass of fruit the independent variable is the thing we are in charge of the thing we are choosing to change here it's the type of light bulb control variables are the things you want to keep constant a few common things to think about are the concentration of a named substance the volume or the mass temperature of the environment and light intensity obviously they are all relevant to every experiment for this particular example keeping the temperature of the environment constant and the light intensity seemed to be most obvious variables are a good place to throw marks away for being too vague a mount is a word you should avoid be specific and say mass volume concentration etc light is a word that will never gain a mark in this context often you'll be referring to the light intensity or wavelength of light so state that clearly lastly is the word substance whatever substance you're talking about name it reliability of results you'll sometimes be presented with an experiment conducted by a student and the question will read something like give two reasons why her results were reliable he has an example of an investigation a student wanted to compare the amount of starch in different liquid food samples she adds the recenter meters cubed of each liquid sample to different test tubes she does three repeats for each sample she then adds two drops of iodine solution to each test tube and compares the intensity of the color change on a spotting tile for most questions about reliability look for repeats and look for something that has kept the same don't just say she did repeats because it's too vague for this experiment you could state that she used three test tubes for each sample giving three repeats and next she used the same volume of food sample for each food test a very common skill you need to demonstrate is graphing skills this question requires a line graph but sometimes a question will state whether a bar or line graph is needed and you have to decide which is appropriate for all graph questions on this specification the mock scheme is the same you'll need to consider the scale the axes must be the right way around and labeled the points have to be correct there must be a line units on the axes and a key to show which line is which if there is more than one data set remember sap look ASAP lú kè let's look at it in practice you'll get your grid and draw the axes with appropriate numbers on each the data points should take up at least half of the available space so keep that in mind when drawing the scale next label your axes with the independent variable on the bottom and the dependent variable on the side plot your points carefully with a neat X don't make big splotches because if the point is more than half a square out of place or covers too large an area you'll be marked down next is your line usually you need to do point to point with a ruler and don't connect it to zero unless you're told to if you label your axes correctly you'll have included the units but double-check that they are there finally make sure it's clear which line is which by either including a key or by labeling each line like I have here lastly clotting bar graphs for this task we'll need to consider the scale axes plotting the points correctly drawing the lines right and adding on the units there's no k4 key in this question because we only have one data set let's start with adding our scale this one might look good because it covers at least half of the available space but if we look at our data we will see the lowest point is eight point one so there's no need to go as low as zero this scale from eight to nine is more sensible and would earn the mark next label the axes then draw bars of exactly the right height you can usually be no more than half of one of the smallest squares too high or too low any more than that and you lose the P mark notice that there's a space between each bar as well to be awarded the line mark your bars must be drawn neatly no wonky lines drawn without a ruler lastly make sure you include the correctly units on your axis titles just like with the line graphs it's necessary to include a key if you have more than one data set but that's not the case here so it's fine without [Music] [Music]