iGCSE CIE Biology Paper 6 Revision Questions And Answers Verified 100% Correct

iGCSE CIE Biology Paper 6 Revision Questions And Answers Verified 100% Correct What is the test for Vitamin C? - ANSWER-Add drops of DCPIP to the solution slowly. It will turn from blue to red if it is acidic. Continue and if it contains Vitamin C the solution will turn colourless. How should you design an experiment? - ANSWER-*Find the variable which is to be changed (from the question) and mention how you are going to change it (ex: to change temperature, use thermometer-controlled water bath at temperatures 10 to 50 degree Celsius). *List all variables that you have to keep constant throughout the experiment (ex: room temperature, volume of water, insect species). Make sure there's only one variable for the investigation. *Mention how long your experiment will last. *Say how you will measure experiments' results (ex: if you're examining presence of starch, say that the food sample which turns the iodine solution a deeper blue contains more starch) *Finally: say 'repeat experiment to get more reliable results and minimise error. It's guaranteed to gain you marks. *If you can, set a control for your experiment. (ex: use boiled enzyme in an experiment to test for enzyme activity) Magnification Equation - ANSWER-MAgnification = Measured / Actual Testing plant for Starch - ANSWER-Boil to break down cell wall. Add ethanol to get rid of chlorophyll. Soak in cold water to soften it. Then use iodine to test for starch. Orange to black. Annelid characteristics - ANSWER-Segmented body, chaetae (bristles) Molluscs - ANSWER-Shell, foot Nematodes - ANSWER-Long, thin body, covered in mucus (parasite) Arthropods - ANSWER-Crustacea, Myriapods, Insects, Arachnids Crustacea - ANSWER-Jointed limbs, hard shell, claws Myriapods - ANSWER-Antennae, exoskeleton, segmented Insects - ANSWER-Antennae, compound eyes, head, thorax, abdomen Arachnids - ANSWER-Head + thorax, abdomen, 4 pairs of legs, spinneret Fish - ANSWER-Scales, fins, lateral line (detect vibration) Amphibians - ANSWER-Lungs, wide mouth, moist skin, four limbs Reptiles - ANSWER-Dry scaly skin Birds - ANSWER-Wings, beak, feathers, scales (on legs) Mammals - ANSWER-Fur/hair, internal fertilisation, feed milk to young Test for water - ANSWER-Cobalt chloride paper. From blue to pink What is an independant variable? - ANSWER-The variable that is changed by the investigator What is a dependant variable? - ANSWER-A variable that changes and is measured What is a control variable? - ANSWER-A variable that should be kept constant so as to not affect the result of the dependant variable How can you make an experiment better? - ANSWER-Do it 3 times and then take an average. Exclude anomalies from your average. How many decimal places should you ANSWER with? - ANSWER-If the rest of the table is to 1 decimal place then you should ANSWER with 1 decimal place even if your ANSWER is a whole number. What is the test for protein? - ANSWER-Add a few drops of Biuret Reagent, gently shake, it should turn from blue to mauve/purple What is the test for Starch? - ANSWER-Add a few drops of Iodine Solution, gently shake, it should turn from brown/orange to blue/black What is the test for Reducing Sugars? - ANSWER-Add 2cm³ Benedict's Reagent, heat/boil, it should turn from blue to green to yellow to orange to red What is the test for Fat (Lipids)? - ANSWER-The emulsion test: Add 2cm³ of ethanol to the unknown solution, gently shake, pour into equal volume of distilled water. If present a milky-white emulsion is formed. What is the test for Oxygen? - ANSWER-A glowing splint is held above a glass tube, in which oxygen gas is trapped. When the stopcock is opened, oxygen gas rushes out, and ignites the glowing splint What is the test for Carbon Dioxide? - ANSWER-Bubble the test gas through limewater (calcium hydroxide solution). Carbon dioxide turns limewater cloudy white.