Cambridge IGCSE Biology (0610) — Past Papers, Revision Notes & Exam Prep

Common mistakes and how to avoid them

1. Digestive organ jobs

   MistakeYou give organs the wrong digestive jobs, such as the gall bladder making bile, acid or enzymes, starch digested in the stomach, or the large intestine absorbing most water.

   Fix

   The liver makes bile; the gall bladder only stores it, making no acid or enzymes.

   Amylase digests starch in the mouth and small intestine.

   The small intestine absorbs most water.

2. Xylem and phloem

   MistakeYou swap xylem and phloem, so you say phloem carries water, mineral ions or starch, or you pick the wrong tissue in a root or leaf section.

   Fix

   Xylem carries water and mineral ions; phloem carries sucrose and amino acids, not starch.

   Xylem forms a central star in a root and lies above the phloem in a leaf.

3. Kidneys, ureters and urethra

   MistakeYou swap the ureter and urethra on a diagram, or name the bladder, urethra, liver or gall bladder as the organ that removes urea from the blood.

   Fix

   The kidneys remove urea, excess water and excess ions from the blood.

   Two ureters carry urine to the bladder, which stores it; one urethra carries it out.

4. Osmosis

   MistakeYou think tissue in a concentrated sugar solution takes in water and gains mass, or that the sugar itself crosses the membrane by osmosis.

   Fix

   Osmosis moves only water, from dilute to more concentrated solution, through a partially permeable membrane.

   In a solution more concentrated than its cells, tissue loses water and mass.

5. Food tests

   MistakeYou mix up the reagents, such as choosing Benedict's solution as the test for protein, or expecting DCPIP to turn blue when vitamin C is present.

   Fix

   Learn reagent, nutrient and result: iodine, starch, blue-black; Benedict's (heated), reducing sugars, blue to brick red; biuret, protein, purple; ethanol, fats, cloudy white; DCPIP, vitamin C, blue to colourless.

6. Cell structures

   MistakeYou give root hair cells chloroplasts or sperm cells a cell wall, or think the cell wall controls what enters and leaves a cell.

   Fix

   Root hair cells get no light underground, so have no chloroplasts.

   Animal cells, including sperm, have no cell wall.

   The cell membrane controls entry and exit; the wall gives support.

7. Diffusion

   MistakeYou choose an option saying a steeper concentration gradient or a larger surface area slows diffusion, or that diffusion needs energy from respiration.

   Fix

   Diffusion uses no energy from respiration: the net movement is from higher to lower concentration.

   A steeper gradient, larger surface area, higher temperature or shorter distance all speed it up.

8. Anaerobic respiration

   MistakeYou mix up the products of anaerobic respiration, giving muscles alcohol and carbon dioxide, or giving yeast lactic acid.

   Fix

   Learn both word equations.

   Yeast: glucose → alcohol + carbon dioxide.

   Muscles during vigorous exercise: glucose → lactic acid, with no carbon dioxide.

   Neither uses oxygen.

More multiple-choice traps: Top 10 IGCSE Biology MCQ Mistakes

Common mistakes and how to avoid them

1. Mitosis and meiosis

   MistakeYou mix up the two divisions, thinking meiosis makes identical cells for repair, or giving a human gamete 46 chromosomes because you swap haploid and diploid.

   Fix

   Mitosis gives genetically identical cells for growth, repair and asexual reproduction.

   Meiosis, used to make gametes, gives genetically different haploid cells: a human gamete has 23 chromosomes, not 46.

2. Turgid, flaccid, plasmolysed

   MistakeYou call a plant cell plasmolysed when it has gained water by osmosis, or mix up the terms turgid, flaccid and plasmolysed.

   Fix

   A cell that gains water swells against its wall and is turgid.

   A cell that loses water goes flaccid, then plasmolysed: the membrane pulls away from the wall.

3. Antibodies

   MistakeYou pick the phagocyte as the cell that makes antibodies, or think an antibody fits any pathogen or has the same shape as its antigen.

   Fix

   Lymphocytes make antibodies; phagocytes engulf and digest pathogens.

   Each antibody's shape is complementary to one antigen, like a key to one lock, so it binds only pathogens with that antigen.

4. Active transport

   MistakeYou forget that active transport needs energy from respiration, so you miss why a lack of oxygen slows ion uptake, or you reverse its direction.

   Fix

   Active transport moves particles from lower to higher concentration, against the gradient, using protein carriers and energy from respiration.

   Less oxygen means less aerobic respiration, so less uptake.

5. Hydrogencarbonate indicator

   MistakeYou expect the indicator around a plant in bright light to turn yellow, forgetting that photosynthesis then takes in carbon dioxide faster than respiration releases it.

   Fix

   Yellow means more carbon dioxide than normal, red means normal, purple means less.

   In bright light the plant takes up carbon dioxide overall; in the dark it only releases it.

6. Limiting factors

   MistakeOn a rate of photosynthesis graph, you name the same limiting factor for the whole curve, or think photosynthesis stops where the line levels off.

   Fix

   Where the rate rises as the x-axis factor increases, that factor is limiting.

   Where the line levels off, the rate is steady, not zero, and another factor is limiting.

7. Transpiration

   MistakeYou think water leaves a leaf as a liquid, or you choose an option where humid, still air speeds up transpiration.

   Fix

   Water evaporates from mesophyll cell surfaces into air spaces, then diffuses out through the stomata as vapour.

   Humid or still air reduces the water vapour concentration gradient, so transpiration slows.

8. Enzymes

   MistakeYou say a high temperature kills an enzyme, or assume that every enzyme works best at pH 7.

   Fix

   Enzymes are proteins, not living things.

   Too much heat denatures them: the active site changes shape so the substrate no longer fits.

   Each enzyme has its own optimum pH.

More multiple-choice traps: Top 10 IGCSE Biology MCQ Mistakes

Common mistakes and how to avoid them

1. Blood components

   MistakeYou write that white blood cells 'fight disease' or that blood gives 'protection', which is too vague to show what actually happens.

   Fix

   Name the process: white blood cells carry out phagocytosis and produce antibodies.

   Red blood cells carry oxygen using haemoglobin.

   Plasma transports substances such as nutrients, urea and hormones.

2. Genetic diagrams

   MistakeYou write a parent's whole genotype as one gamete, so your Punnett square holds the wrong alleles and the ratio comes out wrong.

   Fix

   Each gamete carries one allele of the gene.

   Write the parents' genotypes, circle each possible gamete, then fill the Punnett square and count the phenotypes to get the ratio.

3. Key definitions

   MistakeYou give half a definition, such as a gene as 'a unit of inheritance' or a species as 'similar organisms living in one place'.

   Fix

   Learn them exactly.

   A gene is a length of DNA that codes for a protein.

   A species is a group of organisms that can reproduce to produce fertile offspring.

4. Photosynthesis

   MistakeYou mix up chlorophyll, chloroplasts and palisade mesophyll, leave carbon dioxide out of photosynthesis, or write symbols when a word equation is asked for.

   Fix

   Chlorophyll is the green pigment inside chloroplasts, found mainly in palisade mesophyll cells.

   Learn: carbon dioxide + water → glucose + oxygen, in light with chlorophyll.

5. Describe and explain

   MistakeWhen asked to explain, you only describe what happens or repeat the data, without giving the biological reason behind it.

   Fix

   Describe means say what happens, using data from the graph or table with units.

   Explain means give the biological reason why it happens.

   Compare means state similarities or differences.

Common mistakes and how to avoid them

1. Enzyme action

   MistakeYou explain enzyme action by talking about the enzyme's shape in general, without mentioning the active site or how the substrate fits it.

   Fix

   The active site has a shape complementary to the substrate.

   They collide and form an enzyme-substrate complex, then products are released.

   The enzyme is unchanged and can be reused.

2. Antibiotic resistance

   MistakeYou say bacteria become 'immune' to antibiotics, or that the antibiotic causes the mutation that makes them resistant.

   Fix

   Mutations happen at random.

   If one gives resistance, the antibiotic kills the other bacteria while resistant ones survive, reproduce and pass on the allele.

   This is natural selection.

3. Energy transfer

   MistakeYou say producers make energy, or state that energy is lost between trophic levels without saying how it is lost.

   Fix

   Producers transfer light energy to chemical energy; they do not make it.

   Energy is lost between levels as heat from respiration, and in uneaten parts and waste such as faeces.

4. Similar-sounding terms

   MistakeYou swap terms that sound alike, such as antigen and antibody, insulin and glucagon, or rods and cones, so a correct idea reads as wrong.

   Fix

   Antibodies are proteins that bind to antigens on pathogens.

   Insulin lowers blood glucose; glucagon raises it.

   Rods are more sensitive, for night vision; cones give colour vision.

5. Calculations and rounding

   MistakeYou round too early, give the wrong number of decimal places or significant figures, or calculate the percentage lost when the percentage transferred was asked for.

   Fix

   Underline what is asked and how to round it.

   Keep every digit until the last step, round once, and give the unit.

   Show your working.

Common mistakes and how to avoid them

1. Recording results

   MistakeYou record some times in minutes and others in seconds, or use a different unit from the one the instructions ask for.

   Fix

   Check the unit asked for before you start.

   Convert every reading to it, record them all the same way, and put the unit only in the column heading.

2. Biological drawings

   MistakeYou shade or colour your drawing, sketch with broken or hairy lines, or draw it too small to show the structures clearly.

   Fix

   Use a sharp pencil and single, clear, continuous lines with no shading.

   Make the drawing large, include every visible feature in the right proportions, and use ruled label lines.

3. Safety precautions

   MistakeYou give a general precaution like 'wear gloves' without saying how it lowers the risk, or add goggles and gloves for a harmless solution.

   Fix

   Name the actual hazard, such as a sharp blade or hot water, then the precaution that matches it, such as cutting downwards onto a tile, away from your fingers.

4. Drawing graphs

   MistakeYou choose an awkward scale, leave units off the axes, plot points carelessly, or extend your line beyond the first and last readings.

   Fix

   Choose a scale that fills over half the grid, label both axes with units, plot small neat crosses, and do not extend lines beyond your first and last points.

5. Writing conclusions

   MistakeYour conclusion repeats the readings or mentions only 'time', without linking the result to the aim or to the biology being tested.

   Fix

   Reread the aim.

   State the trend in the results, using the variable names, then link it to the process being tested, such as diffusion, osmosis or enzyme activity.

Common mistakes and how to avoid them

1. Table headings

   MistakeYou head a column with something vague like 'test-tube', or write units next to every number in the table instead of in the heading.

   Fix

   Head each column with the quantity and its unit, such as 'time / s'.

   Write only numbers in the cells, all to the same number of decimal places.

2. Controlled variables

   MistakeAsked which variable was kept constant, you name one you think should have been controlled, rather than one the method actually kept the same.

   Fix

   Look through the method for quantities given as fixed values, such as the same volume, mass or temperature each time.

   Name that variable, not the one being changed or measured.

3. Improving a method

   MistakeYou suggest vague improvements like 'cut more carefully' or 'be more accurate', or change a step that already worked well.

   Fix

   Pick a real weakness and give a specific fix: repeat each test and calculate a mean, control temperature with a water bath, or measure volumes with a syringe.

4. Making dilutions

   MistakeWhen making a dilution, your volumes of stock solution and distilled water do not give the concentration asked for, or do not add up to the final volume.

   Fix

   Stock volume = final volume × wanted concentration ÷ stock concentration; distilled water makes up the rest.

   So to halve a concentration, mix equal volumes of stock and water.

5. Magnification

   MistakeYou measure the image in centimetres but use the actual size in millimetres, or divide the wrong way round, so your magnification is far too big or small.

   Fix

   Magnification = image size ÷ actual size, with both in the same unit, usually mm.

   Show the answer with a × sign, no unit, and the significant figures asked for.