Edexcel IGCSE Biology Paper 1BR (4BI1/1BR) – May 2024 Question Paper

Ace your Edexcel IGCSE Biology exams with this official May 2024 Paper 1BR question paper, exactly the type used by the British International School of Boston – the only private high school in Boston, Massachusetts offering Pearson Edexcel IGCSE qualifications. This authentic past paper covers onion epidermis cells (human red blood cell components – no nucleus, no cell wall, has cytoplasm), tissue definition, serial dilution to make 5% sucrose solution from 10% solution, plasmolysis explanation for cell appearance change after sucrose treatment, insect-pollinated flower structure (pollen production from anther, fruit from ovary), pollen grain magnification calculation (30mm image to 313μm actual = 96x), adaptations for insect pollination (spiky/prickly surface to attach to insects), plant cuttings advantage over seeds (genetically identical, faster), alveolus structure (air passage order: trachea → bronchus → bronchiole → alveolus), surface area calculation from diagram, adaptations for gas exchange (thin walls, large surface area, good blood supply, moist lining), experiment design for exercise effect on carbon dioxide release (limewater or hydrogencarbonate indicator), amylase digestion investigation (starch broken down into maltose, amylase produced by pancreas and salivary glands), water bath pre-incubation to equilibrate temperatures, iodine test for starch (blue-black to brown/yellow), mean calculation at 30°C (20+20+25=65/3=21.67 to 22 minutes, 22 minutes to 2 sf), effect of temperature increase (faster digestion down to 10 minutes at 40°C due to more kinetic energy and enzyme-substrate complexes), enzyme denaturation at 50°C (active site shape changed), modification for accurate optimum temperature (smaller intervals e.g. 5°C), Arctic Ocean food web (phytoplankton features: chloroplast and nucleus, no chitin), tertiary consumers (polar bear and cod), food chain with most trophic levels (phytoplankton → zooplankton → small fish → seal → polar bear), percentage increase calculation (12.6-1.2=11.4, ÷1.2×100=950%), graph analysis of phytoplankton and zooplankton biomass changes linked to light hours and nitrate concentration (spring bloom due to increased light and nitrate), reflex arc pathway (stimulus → sensory neurone → relay neurone in spinal cord → motor neurone → effector), snail habituation experiment (repeated touching decreases time in shell from 112s to 83s over 8 stimuli, benefit = saves energy/avoids wasting time on non-threatening stimuli), graph plotting, coronary heart disease (artery vs vein wall differences – thicker muscle/elastic, smaller lumen, no valves in arteries), CHD artery cross-section with fatty plaque narrowing lumen, reduced blood flow to heart muscle during exercise causing angina/less efficient response, risk factors for CHD (high blood pressure, high cholesterol, obesity, poor diet, lack of exercise), graph analysis of risk factor alleles and smoking (increasing alleles increases risk, smokers have higher risk than non-smokers at same allele number), lactose intolerance genetics (recessive allele d, inability to digest lactose), genetic diagram probability calculation for child with lactose intolerance, diarrhoea explanation (undigested lactose draws water into intestine by osmosis), natural selection in milk-drinking populations (variation in lactase persistence, those able to digest milk had survival advantage, reproduced and passed on dominant D allele), fermenter (stirrer maintains even temperature/nutrient distribution, water jacket removes excess heat), transgenic tomato plants (recombinant vector production using restriction enzymes and DNA ligase), photosynthesis rate graph (temperature increases rate up to optimum then decreases, higher light intensity gives higher overall rate), sustainable glasshouse system (artificial lighting and heating from wood-burning power station, CO₂ pumped in to enhance photosynthesis, benefits: year-round growing, higher yields, reduced food miles, environmental: renewable wood fuel, but CO₂ from combustion). Perfect for realistic exam practice under timed conditions – ideal for students following the Pearson Edexcel International GCSE (9-1) Biology specification (4BI1) or Science Double Award (4SD0).