hello everyone and hope that you're doing well today we're looking through this paper two CC biology paper this biology paper is from May June 2023 as always please remember to read through the instructions carefully before you start the examination and if you should have any questions or queries clarify those with the examiner before you begin now let us jump into section a question number one and this reads that figure one shows micrographs of an animal cell and a plant cell and you notice carefully you see the animal cell on your left and the plant cell on your right now let's jump to the questions now the first question part A it said what type of microscope was used to produce the images shown in figure one and this is an electron microscope how we know this is because of the details of each cell all right let's go to the next question part two of a it said draw a large clearly labeled diagram of one plant cell from the micrograph shown in figure one all right I've drawn my diagram here with the labelings let me just zoom in a little bit so you get a better scope of this diagram all right and here we go so diagram again must be large all right let's go one more time right that is good so your diagram show should be large relatively large and properly labeled and if you notice you see the cell wall you see the cell membrane the nucleus the nucleolus the cytoplasm the chloroplast the vule and the mitochondria again this also proves that it is an electron microscope because of the details that are in the diagrams all right a light microscope as you know will not produce such detail more likely you will only get the outline of the cells all right so let's go to our next question our part of question all right so let's go down and this is part three all right and this question reads say list two similarities between plant cell and the animal cell all right let's go a little bit more in our Zoom all right just be a second right that is better all right so similarities will include cell membrane ribosomes vacu cytoplasm nucleus and mitochondria so both cells have these structures in common for part four it said the most prominent structure on the animal cell electron micrograph carries gentic information in the form of DNA State the name of this structure and notice here it said that this is an electron micrograph and and this is another clue to prove that it is an electron microscope all right however the prominent structure in the diagram if you could go back you'll notice that it is the nucleus that is shown so definitely the nucleus is that structure that is most prominent and that cell that carry the DNA all right and of course which I'm going to discuss this a little bit further down but you should also know that chromosomes carry DNA all right but the chromosomes are not um that obvious in this diagram unless the diagram is not clear otherwise you can use chromosome as a structure as well all right for Part B it said the diagram in figure two shows the general structure of a bacterial cell all right and here it asks to identify one similarity between the bacteria cell and the plant cell now the first question actually ask you to label this I think um there's a question talk about labeling all right it's down further all right so we label the structures I don't need to go back I just want to make sure you actually understand and know the structures of the bacteria cell we have our flagella all right flagellum for singular we have p and pum will be singular we have our plasmid we have our DNA and you can actually label it as circular DNA we have our ribosomes we have our capsule which is outermost layer we have our cell wall and cell membrane so part one of this question asks us to identify one similarity between the bacterial cell and a plant cell and the similarity between a plant and animal cells that both bacterial cell and a plant cell they have a cell wall all right so that is similarity between both for part two it said the structures of the bacterial cell are especially suited for its role in infecting other organisms table one lists four of these structures complete table one by explaining how each structure helps the bacterium to infect organism an example as being provided for you all right so we have the structures there we have our P which is also called our fmria we also have our flagellum we have our slime capsule or you can just say capsule and we have our cell wall all right as they give us the example up top there so I'm going to go straight into fulum and fulum enables movement towards the target um Target cell or the host um cell all right and the capsule will protect the bacterium from armful chemicals and also help the bacterium to stick to the Target cell all right and the cell wall also provides some form of protection as well um and it provides protection against antibodies and also the fosite all right now now we at part C and it said human beings are multicellular all right and are made up of a large variety of cells it's a complete table too by distinguishing between the following cells I'm going to distinguish between red blood cells skin cells and nerve cells and so the difference between red blood cells and skin cells is that the red blood cells have no nucleus while a of course the skin cell will have nucleus all right red blood cells are by concave in shape generally smaller than the skin cell and contains hemoglobin which of course the skin cells skin cells have none of these the difference between a um skin cells and nerve cells is that nerve cells have extensions and they are called axin and ddes skin cells lock axen and ddes um again nerve cells are insulated with what are called milin sheath all right and of course skin cells do not have those number part two it said name one feature that would enable a scientist to distinguish a spiral bacterial cell from an animal cell when viewed under a microscope and one of the most obvious thing that will be noticeable is the bacterial cell or bacterial cells generally will lack nucleus because they do not have a nucleus or a true nucleus also what is important is that the bacterial cells they have one circular DNA which I label up top all right also points that you can also discuss or include depending on the number of marks you can say um the plasmid will be in the bacteria um the bacteria cells will have cell wall they have a capsule they have flagella and also Pei all right and of course an animal cell will not have those all right all right question number two um figure three is an incomplete diagram of meosis in an animal cell is a for gentically different daughter cells P QR and S are produced and notice we have chromosome up top there then we have uh meiosis and these will be our final cells which are which are called daughter cells and again they are generically different just to make a point right there say we need to complete the diagram to show the difference that's what part A is saying so what I did now if you notice what I did just to make sure you understand this notice what we started out with we have a long dotted line or broken line um chromosome we have a short one that is broken line and we also have a long um solid line and a short um solid line which is more curved all right so um we have elix shape chromosome you know based on the diagram so notice the ones they put in P and S okay and they put two solid one in p um two broken lines one in s so what I did now for Q and R which again you can have a different different varieties of these things the most important thing you can only have two chromosomes within each of these cell why because meiosis only produce half the number of chromosomes that's the first thing you have to know now what is also important because of what the C called crossing over and synapsis in prophase one what you're going to have is that you'll have sharing of genetic materials so notice what I did is to mix the solid lines with the broken lines in different ways to get my q and my R all right and um of course also what will be acceptable as well if you put a solid one and a broken one as well that will be also acceptable but remember um is that Sister chromosomes will separate all right we go to up opposite pole so Ence you will not have the same or or different chromosome within the same cell what is also important too remember that um chromosomes are independently assorted as well just to make mention of that all right what is important about the difference just a notation right here that you need to remember is that the differences in daughter cells for meiosis it is due to the crossing over and snapis in prophase one all right now for part two it says State whether the daughter cells produced by meosis or you may pronounce as meiosis are applo or diploid and meiosis only produce haid cells haid means half the number of chromosomes so for example sperm cells right and egg cells they only have half the number of chromosomes and when they fertilize each other then what happen is that the numbers now come to get come together to give you a full number which we call diploid all right for Part B it's a name one part of the body in which uh meiosis occurs and this may take place within the ovaries or testicles so ovaries if you're a girl and testicles if you're a boy all right now for part C is a name the structure within the nucleus which contains the genetic materials and this will be chromosomes chromosomes contain the genetic materials all right and just a point to note right here again is that genes make up D while DNA make up chromosome all right so chromosome will be the large molecule and portion of the chromosome we call DNA and then and again just to make note is that when the DNA um when the chromosome uncoiled all right around estone Protein that's when you get DNA and segments of DNA is what you call the genes all right all right so just to make note of those um extra information there all right so um part D is said um Cara and catura are Daughters of Mr and Mrs balam yet their observable characteristics are very different it's a user knowledge of genetics to explain why the observable characteristics in the sisters are are different include two possible reasons in your response and I just give you the reasons with explanation one time and so for reason number one is that during meiosis especially prophase one all right we have crossing over um result in homologous chromosomes exchanging genetic materials and now this accounts for the differences in the daughter cells or gamit all right and for reason number two is that parents can be carriers of recessive alls H the possibility of of homozygous recessive genotype resulting in different phenotype compared to siblings with dominant alyss so again if they are carriers of the recessive alls that will not show up only when those recessive alls come together then you will see that characteristic so you may see a sibling with certain characteristic and then you see one with a different characteristic is because of the difference between dominant and recessive Al all right so one it could be because of crossing over exchange of genetic material and another one is because of the differences in dominant um alyss and the possession of recessive alyss all right so part e state two reasons why meiosis is important to living organisms and one of the most I wouldn't say it is the most but one of the most important thing is that it result in what we call genetic variation or diversity in organisms and of course we know why because um if organisms are all the same then for example one particular disease could wipe out everything you would have easy extinctions of organisms so Varity variation diversity will give rise to more sustainability of organisms all right and of course the adaptation Pro process will be better as well um another option you can put there is that um because of meiosis you can suppress or reduce gentic disorders for example cell anemia right versus normal blood all right so of course um if a person with sick of cell made with a normal blood the child may not come out the sick of cell and eventually May Fade Out um depending on the meeting with normal blood persons all right so the next one is that increase adaptation and survival of organisms and that one is closely related to number one as well number three is closely related to number one and that is because of diversity and variation of course um another point here is that it can AIDS in the production of gametes for sexual reproduction and another point is that provides means of maintaining died number of chromosomes when gametes are joined because meiosis give you half and so because you have that half when they come together by means of fertilization you get the full number all right so it's very important to do that all right part two it stated that meiosis also occurs in floring Plants it a name two gametes Nam the two gametes produced and those two gametes are polling and ovules and point to note is that each polling has two sperm cells all right and I think there was a question one time that that I think they give you like um like two pollen grains and asks you how many ovules can be fertilized and all you need to do is to multiply that number by two we get four all right so things like that you need to just be bear in mind when you're going through these papers question number three say list three kingdoms other than the animal kingdom into which organisms can be classified and they have four options to choose from you have the Plante which is plants you have the bacteria otherwise called the manaria we have fungi and protesta all right for Part B it say fish are organisms that belong to the animal kingdom is a figure four shows six species of fish a to F that live on Coral Reef in the bahamama sorry in the Caribbean all right and so here you have the six of them and here we have the six species notice they're very different of course um and these are Caribbean fishes and so for part one it said list three visible characteristics that may be used to classify the fish in figure four all right so if you look at them you notice that the the shape and size of their fins are different right so you can put them in different groups Bas and size uh and shape of their fins we can also look at the body the shape and size as well the body not all the same shape and not all the same size the type of shape of the mouth the mouth is also different if you notice them as well um you have the patterns on the body as well so patterns on body is also a difference the markings or patterns or Contour in some cases they're all different okay all right and so the next part of a question asks us now say using any one of the characteristics listed in B1 I the fish species a to F into two groups um and we have group one and two and so they give us the the two columns here so group one and it's a characteristic use so we going to use large mouth compared to smaller mouth which and the smaller mouth ones you notice they are typical um shape of fish mouth right and if you look at the diagrams you notice that c fish c and e they have larger mouth or unusually shaped mouth especially um I think was what let me just go back one second uh notice that se like a snout type of um mouth a very long unusual mouth and E which is a group of very large mouth as well the others are typically small mouth all right so that's one you can also use the fin you can also use the the patterns and put them in different categories as well so you could do anything to get those four marks real easily all right for part c one is a Define the term conservation as us in biology and there are some important words you want to put into this and it is any process or method or attempt to manage protect and preserve natural resources so you must use the word manage protect preserve those are very important words to use when it come on to conservation all right now for part two it say fish populations which live on coral reefs in the Caribbean are under a threat of Extinction due to predation and po um pollution all right so is exp two methods of conservation that may be used to minimize these Str um but point to note here before we go to these threats is that when talk about predation is not only fish eating fish or larger sea animal eating fish but we also hunt and capture fish as well so we are their predators I just want to Bear it in mind I know sometimes when you think about the the Marine ecosystem you only think about um when we talk about predation pre or Predator you refer to the larger organisms um like shark and all those are bigger fishes but definitely we are predators um of fishes as well all right so one we can establish proper garbage disposal methods um so you don't pollute the water of course you can design proper sewage treatment plans to prevent sewage from entering um the water body all right and um that word is spelled incorrectly and just quickly change that entering and a point to note is that as I do this quickly um I just wanted to note that um when I think about sewage entering water body you need to think about um oh I make an error anyway all right so the sewage entering water body to prevent um pollution and again what is important with that um point that I made is that um sewage will lead to what they call UT tropication which is excess growth of algae it just mentioned that our next Point here is that encourage the reduction of pesticides and fertilizer used among Farmers near coastal areas so the farmers that live in the coastal areas encourage them not to use um pesticides um and fertilizers and so on all right again there ease missing from the fertilizer as well I'm just bear it in mind I'm not going to change it because I'm going to erase it I don't know why but anyhow next Point here is that establish and enforce open and closed season and the reason for open and closed season is that the close season will allow the marine organisms or the fish to reproduce all right give them chance to reproduce and replenish their population you can also sanction the prohibition of releasing pet fish or other marine species in water bodies and this will reduce the possibility of invasive species all right and lion fish is a is a problem at this point because the lion fish is an invasive species in the Caribbean so definitely um and I guess it was released Maybe by a fish owner that no longer need that fish into the large body of water and then it become invasive all right number four he said organisms can be either multicellular or unicellular state examp state one example of a unicellular organism and a pretty much easy one here is bacteria um so that would be my first answer we have other examples that you can also list um such as protest and protest example of that will be amiba parium or ugina all right so those are some examples there um heast for example can be a as a single cellular and heast will fall on the fungi but of course not all fungi or unicellular just to make mention of that now part two is a list three material that can be transported in multicellular organisms and this you can just run out on this one because we have so many um things we can list water for example glucose amino acids mineral salts hormones fatty acids glycerol sucros in Plants waste um example UA all right so there are so many things that we can list for that one and for part three is it explain why multicellular organisms require transport system systems while unicellular organisms do not include two reasons in your response and so what I do is to put the reasons and just explain one time um and so the first reason is that it's based upon size okay and that multicellular organisms are bigger or have lower surface volume ratio and so because of this they need transport system to take substances to and from from the many cells over relatively long distances all right also they need transport system because tissu are generally large and require a large supply of substances so therefore you have to transport these requirements of substances towards these um tissues or cells reason number two is that exchange of substances directly between the external environment and these are the points now to make note of are the point to make note of so unlike unicellular organisms most cells in multicellular organisms they are unable to exchange substances directly to the external environment for example your alveoli your lungs and then it will take oxygen towards the cells of your body for respiration these cells are embedded deep with inside of you so therefore you have to transport the oxygen through your respiratory system mother of fact it go through your breathing system first first then it go through your blood and then it go through those cells because those cells are deep with inside of you a single cellular organism it just exposed directly to the environment so they can just capture um the gases that they need from the environment if they do need gases all right and point to note here is that um again just the last sentence there say ends transport systems are needed to effectively take substances to and from these cells all right now next question here here it said define the terms translocation and transpiration and this paper is relatively easy ask a lot of definitions for some reason now translocation is said that the transport of of plant food throughout the plant by the FL and this plant food that I'm talking about is generally sucrose okay sucrose not glucose sucrose all right now transpiration is evaporation of water that's very important to mention the transp transpiration is the evaporation of water from the uppermost parts of a plant generally the leaves I'm talking about right all right so part two here now it said explain two ways in which the structure of the xylm is suited for its role in transpiration now this question is kind of asked a certain way because looking for the importance of xylm in transpiration not the importance of xylm in terms of Transportation but transpiration all right remember that xylm transports water and mineral Sals but how the xylm is suited to a cyst transpiration which is the movement of water through the plants and then it will evaporate through through the leaves so one is that the xylm is dead is a dead tissue and since it's dead it allows water to travel through easily without being absorbed along the way because if the xylm cells or tissues were not dead then they themselves will absorb water so the xylm is like a straw dead hard structure rigid all right all right and so it is also narrow and because of this narrowness it aids in a capillary action all right that mean water could climb through the xylm easily all right and so water can move upwards um without any resistance or Little Resistance Against Gravity all right also it's tube likee which is kind of related to narrowness of course but it's tube like for the fact it's tube like and since it's tube tube like it also allows capillary action and easy passage of water all right water travel water travels through through tubes quite easily compared to other stuff all right and again to note because of these factors or or or adaptation we may call them water can passively move upward through the xylm so it move easily without little little to no energy all right or little to no resistance now for part three it said suggest how the structure of the flm allows it to deliver nutrend to see elements and this is one similar process called diffusion however based on the nature of the concentration of substances is actually active transport because the substances will go against a concentration gradient all right so you put the fusion and put active transport then you get the answer or you can put active transport is also so fine all right but the major process is the fusion by active transport all right and so for question number five we're almost there he said define the following terms again this is loaded with definitions um I don't know they may want to give away points the um that here so it said diffusion is the first word to Define and diffusion is the movement of particles from an area of high concentration to an area of low concentration until the particles are evenly distributed breathing is is the next term that they want us to Define and de breathing is the process of inhalation so inhaling which is taking air in and exhaling which is the removal of air all right and the final word on this question to Define is respiration and respiration is a process by which nutrients such as carbohydrates particularly glucose are used to produce energy so it's really the production of energy from food all right but I just want to make mention that that energy that we talk that food we talking about is actually glucose carbohydrate is the primary source of um energy all right all right now next part of question here now is Part B it said name the three muscles in the rib cage which are responsible for breathing in humans and typically um you'll have the diaphragm you have intercostal muscles and M of fact just make mention here you have the internal intercostal muscles and you have external intercostal muscles and um if you go to the cape level you might learn about also inner um intercostal muscles so you have actually three intercostal muscles but surpisingly for this question diaphragm internal intercostal and external intercostals they are sufficient for this um level all right part C and for part C it said explain how the process of gas exchange occurs in the lungs and um I kind of give you a whole outline of how the air reach the lungs first and then we and then I just mention it at the bottom we actually take place in your lungs so the first thing that air air is a mixture of gases just to make mention of that it enters the the nose or nostril and also the mouth and a moves down the traa all right and traa the Chuck is kept open by a c-shaped um ring um rings of cartilage a matter of fact and then air then enter the um Branch off into the broni and then air then enters the bronchioles once it in the bronchioles and what going to happen here now is that air then enters the alvioli and alvioli those are the sack like structures that are attach the ends of the bronchioles and what is important the Alvi they are surrounded by many capillaries this is very important in the gasos exchange process by the way now oxygen now is able to diffuse across the alveoli into the cap Aries while carbon dioxide will diffuse from the capillaries into the Alvi and that is how we have the gases exchanging so carbon dioxide is exchanged for oxygen and carbon dioxide is exhaled out of the body of course in the in the reverse process going towards the nostril and the mouth all right so again in in the lungs you must talk about the the capillaries many capillaries around the Alvi and the movement of um the gas in and out and what is also important for you to mention within the lungs is the concentration of these gases so in the Alvi what you're going to have and please make a note of it please write it down so in the Alvi what you're going to have is a higher concentration of oxygen therefore it will move from the Alvi into the bloodstream where there is a low concentration of oxygen however now in the capillaries surrounding the Alvi you will have a high concentration of carbon dioxide hence carbon dioxide will move into the alveoli where there is a low concentration of carbon dioxide and this process is diffusion so you must mention that please mention that write down those all right I should have written down all of that but space all right the next thing to make note of is that the alveoli must be thin moist with large surface area to be effective in gaseous exchange so this bit of information very important for you to understand the whole process of breathing and gaseous exchange let's jump to the next part of question here Part D it said explain how human beings use anerobic respiration during exercise and a point to note that um I'm just going to use this concept of explain oxygen debt all right and so during cus exercise oxygen sometimes become low okay in the cell and this is because oxin is used up faster than it can breathe in all right however though even though oxin is low respiration still takes place all right so what happened in the muscles now because this is where un aerobic respiration takes place in the muscles point to note as well that in animals including us we undergo un aerobic respiration in our muscles but particularly in the cyop plasm of the cells an aerobic respiration does not occur in the mitochondria but it takes place in the cytoplasms of the cells so please cytoplasm of cells that's way is taking place please make a note all right so point to note here is that anerobic respiration which is called lactic acid fermentation that's occuring us because you have another un anerobic respiration which is called alcoholic fermentation not in animals but in microorganisms such as heast all right so again on aerobic respiration which is lactic acid fermentation occurs instead of aerobic respiration because of low oxygen so without oxygen glucose molecules breaks down into two lactic acid molecules all right and so half of a structure of a glucose is technically a lactic acid they're not the same it's not exactly equal to half because the structure is different and it is acidic in nature all right and so this release a small amount of energy in a relatively fast time so of course dur during strength exercise you need that quick energy you're going to respire an aerobically to get that quick energy however it will not be a lot what is also important during strenous exercise you produce a great deal of lactic acid which you call which will cause cramping or may cause cramping all right all right so just to make note that the muscles rely on this quick release of energy to keep working all right and now we are on to our final question again a definition this paper is loaded with definitions now we said define the terms eje and excretion and ingestion is the release of undigested food from the body while excretion is removal of metabolic waste from the body and metabolic means from chemical reactions all right and so for respiration for examp example is a metabolic process so therefore carbon dioxide is a waste all right just to make mention of that all right and it said Part B is said humans in humans several organs are responsible for excretion all right a list two organs of excretion and for each organ State one substance which which is excreted from it so for example the excretory organ which is the lungs all right and the substance released from the lungs is carbon dioxide all right we also and remember that carbon dioxide is produced by the metabolic process of respiration we also have um kidneys and kidneys will release Ura and excess water and Ura comes from process of deamination it's a chemical process so it's metabolic deamination is a chemical process where of course excess amino acids are converted into UA there's a number of steps that take place um you can check out my um uh lesson that I have on deamination all right and skin will release Ura as a waste metabolic waste and also excess water as well all right and so for part C he said Joy is ill and is vomiting a lot during the day she becomes very um dehydrated as a result of her condition because she has lost a large volume of fluid explain the role of the kidneys in in correting Jo's um fluid imbalance and a first point to note is that as she becomes dehydrated her blood becomes concentrated which means less water not dilute but concentrated all right with every other substance except water right because no water is a large part of the blood now the second thing will happen is that this signals the secretion of what we call ADH which is anti dtic hormone and what going to happen here is that more water is re absorb because of ADH more water will be reabsorbed in the nephrons which is the tubules of the kidneys particularly the the the proximal um convolution and also the loop of Henley those parts are are majorly responsible for reabsorption of water all right and then what will take place now is that since water is reabsorbed water is conserned which is point4 what is conserved in collecting duct and the urine will become more concentrated ated because you're not going to urinate a lot now you're going to urinate less and so this also cause less urination and as a result the blood will become more diluted and more water will be available to the cells of the body because if the cells don't not have water or enough water then you're going to start to feel the effect of dehydration and then you may lose your life all right so you have to be the cells have to be hydrated to work and I want to make a mention to the way I make my point really and truly there's no need for you to write no long epistle or no long extended paragraphs you just need to go to the points they looking for your points it's always quality over quantity it's not the amount you write but what you write and also I would say make sure you have a certain order of flow in terms of explanation all right so don't need to be writing writing these long paragraphs and then you're trying to figure out where the points are and all that no unnecessary totally unne necessary now part two suggest one way in which Joy can correct the fluid loss she experien as a result of vomiting and simply drink some water drink some fluid whether be juice or whatever it is or just simply drink rehydrating fluids like example Gatorade all right and of course speed the light and all those type of stuff right anything like that you're right you get your marks all right part D is explain two ways in which plants conserve water and I have four ways right here one is closing their sto mat very easy so if it's losing too much water the stor water will be closed and of course you could explain that is this is closed by the guard cells all right and this will reduce water escaping by evaporation plants also have adopted thick waxy cuticles some plants a matter of fact have those thick waxy cuticle and the and the was cuticle generally whether it be thick or not the was cutic creates a barrier against evaporation and also boxy cuticle is responsible for reflecting light and heat to reduce EV operation um some leaves are very narrow or small smaller leaves are narrow leaves are even leaflets um um for example like some TI right leaflets not really big leaves or defined leaves or well established leaves and these now generally have fewer stomata if any in some cases and so for therefore if you have reduced tomata because of reduced surface area then naturally you are going to have less evaporation some plants also shed their leaves and the reason for shedding the leaves is to reduce the amount of s um surface area for evaporation or simply reducing the amount of stoat that are present on the leaves or plant to cause evaporation all right so those are four ways that you can have and that is number 15 and we end of the test all right so again I wish you luck on the upcoming exams and for those who are just reviewing for knowledge sake thank you for watching as well and please share with your friends of course and I looking forward to see you again take care have a great one