Complete AQA GCSE Biology Required Practicals Guide

here are all the GCSE biology required practicals for AQA first some tips that you should always keep in mind when

answering a question on a practical in your exams remember that in many of these investigations there's an

independent variable the thing you change a dependent variable the other thing that changes as a result which you

measure and controls variables that could change but we keep them the same throughout in order to ensure that

results are accurate always say what piece of equipment you use for each measurement don't just say measure the

length of the object also add with a ruler or whatever using that's a mark in itself when it comes to safety we always

use goggles and off and gloves when working with chemicals State the flipping obvious if you think surely

they don't want me to put that put it down anyway you never know what marks you might pick up talk about the

accuracy of measurements how will you reduce errors and uncertainties for example you get your eye in line with

the measurement when using a ruler or measuring cylinder to reduce Parallax error another classic thing you should

put down is multiple or repeat measurements or readings to calculate a mean from finally it's okay to write

your answers in bullet points format in fact I recommend it as it helps you and the examiner keep track of how many

different points are being made because I'm trying to fit lows in here you might see me write abbreviated points for the

sake of brevity but when you write a point do it in full make sure you use proper English don't start going all

Tarzan like saying heat liquid with fire more like heat the water gently on a gauze on a tripod over a buns and bur a

flame also don't forget that you can see me and others from mansbury science doing these practicals for realsies on

mansbury education link is in the description let's go by Biology one microscopy usually you'll get a thin

layer of onion skin using a scalpel and tweezers place it on the microscope slide add a drop of iodine to stain the

cells so they're more visible and place a cover slip on top place the slide on the stage turn the microscope's light on

or if it's a mirror instead tilt it so it reflect up the condenser to the slide and make sure you start with the

shortest objective lens the smallest magnification use the co Focus knob then the fine focus knob to move the stage

until the specimen is in Focus then change to a higher magnification objective lens and refocus if needed you

could have a tiny graticule a tiny ruler that sits on the slide as well that lets you measure the size of cells in

micrometers micro is times 10- 6 in standard form so a cell length of 2.5 microm is 2.5 * 10- 6 M by all two

osmosis the aim is to find the concentration of sugar in potato cells but it could be another veggie instead

cut equal size cylinders from the same vegetable using a COR chop off the ends so there's no non-permeable skin left

dab the excess water off the surface we using a top and balance then place in test tubes filled with different

concentrations of sugar solution this is our independent variable after a set time say a day we remove them dab off

the excess water again and reway calculate the percentage difference in Mass for each cylinder this is our

dependent variable some will have a positive change some negative plot these against solution concentration and you

should get a straight line where the line of best fit meets the x-axis is the concentration at which no osmosis occurs

no water moves in or out of the cells so that must be the same as the concentration of glucose in in the T

cells themselves bi all three enzymes the aim is to determine the optimum temperature or pH for an enzyme usually

done with the enzyme amalay and substrate starch but it could be something else instead the independent

variable is either temperature or pH which we change using a water bath or buffer Solutions respectively the

dependent variable is the time taken for all of the starch the substrate to be broken down measure out a set volume of

the amalay and starch Solutions using a syringe or measuring cylinder then mix together and start your timer every 10

seconds remove a bit of the mixture put a drop in the spotting tile dimple that has iodine in it will turn black

initially showing there's still starch present it hasn't been completely broken down yet repeat this every 10 seconds

until there is no color change at all that's the end point record this time repeat these steps using different

temperatures thanks to the water bath and measure the temperature with thermometer in the test tube itself of

course or we change to a different pH buffer solution plot the time for each against temperature or pH and draw a

line of best fit which will be a curve we say the optimum temperature or pH is between the two lowest points by all

four food tests finding out what nutrients are in different foods for solid food we grind using a pesin water

then add distilled water to create a solution we've already seen the test for starch we just add iodine solution if it

turns black or a dark purple there is starch present to test for glucose and simple sugars we add benedic solution

and heat using a water bath it's a semi-quantitative test as the color can go from blue to green yellow to Orange

depending on how much sugar is in the food biret reagent will turn from Blue to purple in the presence of protein to

test for fats that's lipids we add cold ethanol and leave it for a minute then add this to a test tube of water if the

solution goes cloudy that's a positive test F lippits by all five photosynthesis the aim is to determine

the relationship between light intensity and rate of photosynthesis technically the independent variable is the distance

of the plant from the light source the Deep inent variable is either the volume of gas made in a certain time or the

number of bubbles released say in a minute we use Pond weed that's submerged in water in an inverted test tube or

measuring cylinder once it's in there we want to get our little scissors and cut the stem at an angle and add sodium

hydrogen carbonate in the water to promote oxygen release and of course we want to do this in a dark room we

measure the distance between the light source and pond weed using AER rule turn on the light and wait say a minute for

the pond weed to acclimatize for the photosynthesis to reach a constant rate then we start counting bubbles or we

measure the volume of oxygen made we repeat this at different distances then plot bubbles or volume of oxygen made

against distance you should end up with a curve that looks something like this this is because light intensity follows

an inverse Square relationship with distance that is if you double the distance the light intensity quarters

and therefore the rate of photosynthesis should two by all six reaction times nice and easy we just hold a ruler

between your lab partner's finger and thumb with the zero Mark in line with them and drop it without warning and

they grab it as fast as they can the reaction time can be calculated using one of Newton's equations of motion

rearranged as t equal < TK of 2 s/ a where s is the distance in meters which you need to convert and a is the

acceleration due to gravity 9.8 m/s squared or you might be given a conversion table instead don't forget to

do repeats and calculate means for this one but it is worth remembering that a person will get better over multiple

tries you could then add in an independent variable to see how that changes reaction time this could be with

and without distraction say texting on a phone or before and after drinking a sugary drink which would be a stimulant

B all 7 quadrats we can use a quadrat to help us estimate the population of an organism in an area use a random number

generator to choose grid positions in your area to place the M squ quadrat over and count the number of the chosen

organism inside each you should aim to sample 10% of the total area to give an accurate estimate calculate the mean

number per me squar then multiply this by the total area in me squ to give an estimate for the total population you

can also combine the quadrant with a transect aign to see how the population density varies with distance in a

certain direction say along a beach moving the quadrant up the transect 1 M at a time you can plot population

density against distance then this could also be a kite graph don't forget the factors that affect population density

caused by other living things are biotic factors say Predators if it's a non-biological Factor say the surface

that the organism is on this is an abiotic factor the final three biology PRS are triple only biology 8 is

microbiology we can either put spots of different bacteria cultures on AAR in a pet radition and observe how they grow

over time or spread a culture all over the AAR to make a lawn on which we can put drops of antibiotics or paper discs

soaked in them we use a septic Tech technique that is every piece of equipment must be sterile we can ensure

this by putting the glass pet spreader or Rod Etc through a bunson flame before using we also open the dis just a little

bit to work on it and also towards the Bunton Flame the heat will kill microbes and also the up trft from the flame will

stop microbes from moving into the dish we only put a couple of bits of tape on the dish to secure the lid as we want

air to get in to allow aerobic respiration in the bacteria if it's anerobic some real nasty stuff could be

made instead we then leave them incubate for a number of days then we measure the diameters of the colonies on the EG

using a ruler or the areas in which there were no bacteria if we used antibiotics we then calculate the areas

using p pi r squ or PD squ over four and compare them by all nine germination we just take some seeds say Crest put them

on damp cotton wool in a Petri dish left to stand upright in the dark and let them germinate cute after a few days you

can rotate the dish 90° after another few days you'll be able to see a bend in The Roots this is because of geotropism

the fact that Roots will always grow downwards you can also let a small amount of light into where the dish and

you'll be able to see their shoot growing towards the hole this is due to phototropism by all 10 Decay we measure

out a certain volume of hole milk or cream using a syringe or measuring cylinder and put in a test tube we add

sodium carbonate then the indicator phenol phalin this turns pink above a certain pH about 8.3 adding the enzyme

lipase will cause the milk to Decay and the solution becomes more acidic and so it will eventually decolorize our

independent variable is the temperature we use a water bar to achieve this and we put a thermometer in the test tube

itself to sure we getting accurate reading for temperature use a stop clock to get the time taken for the solution

to decolorize then plot these times against temperature again similar to the enzymes PRACK will end up with a curve

the hotter the temperature the faster the rate of reaction that is until the enzyme denatures so once again the

optimum temperature is between the two lowest points on the graph leave a like and a comment if you found this helpful

click on the cards to go to the milsbury science playlist or the other card to go to the videos covering whole papers see

you next time