Key term
Edexcel GCSE Biology 1BI0
Key Concepts in Biology
Topic overviewEukaryotic and prokaryotic cellsSpecialised cells and their adaptationsMicroscopes and magnification calculationsSize, scale and units in cell biologyEnzyme action and denaturationFactors affecting enzyme activityEnzymes in synthesis and digestion, and rate calculationsFood tests and the energy in foodDiffusion, osmosis and active transportOsmosis in potatoes and percentage change in mass
Cells and Control
Topic overviewMitosis and the cell cycleWhy mitosis matters: growth, repair and cancerGrowth, differentiation and percentile chartsStem cells and their use in medicineThe structure and function of the brainNeurones, receptors and the reflex arcThe structure and function of the eyeEye defects and how they are corrected
Genetics
Topic overviewAsexual and sexual reproductionMeiosis and the formation of gametesDNA structure, genes and the genomeExtracting DNA from fruitMendel's work and the inheritance of blood groupsAlleles, genotype and phenotypeMonohybrid crosses and sex determinationProbability and ratios from genetic crossesCauses of variation: genes and environmentThe Human Genome ProjectGenetic variation and the effects of mutation
Natural Selection and Genetic Modification
Topic overviewDarwin, Wallace and the theory of evolutionNatural selection and antibiotic resistanceFossil evidence for human evolutionStone tool evidence for human evolutionThe pentadactyl limb and the three domainsSelective breedingTissue cultureGenetic engineering and modern agricultureBenefits and risks of GM organisms
Health, Disease and the Development of Medicines
Topic overviewHealth, disease and susceptibilityPathogens and common infectionsHow pathogens spread, and the virus life cycleSexually transmitted infectionsHow plants defend themselvesPhysical barriers and chemical defencesThe immune system, immunisation and herd immunityAntibiotics and developing new medicinesAseptic technique in culturing microorganismsTesting antiseptics and antibiotics on bacterial culturesLifestyle factors and non-communicable diseaseTreatments for cardiovascular disease
Plant Structures and Their Functions
Topic overviewPhotosynthesis as an endothermic reactionLimiting factors in photosynthesisLight intensity and the rate of photosynthesisRoot hair cells, xylem and phloemTranspiration and translocationLeaf structure for photosynthesis and gas exchangeFactors affecting the rate of transpirationPlant adaptations to extreme environmentsPlant hormones, phototropism and gravitropism
Animal Coordination, Control and Homeostasis
Topic overviewHormones, endocrine glands and homeostasisThe menstrual cycle and its hormonesHormonal and barrier contraceptionHomeostasis and thermoregulationControlling blood glucose, and type 1 diabetesType 2 diabetes and body massThe urinary system and the production of ureaThe nephron, filtration and selective reabsorptionTreating kidney failure: dialysis and transplants
Exchange and Transport in Animals
Topic overviewWhy multicellular organisms need exchange surfacesAlveoli and gas exchangeRate of diffusion and Fick's lawThe blood and its componentsArteries, veins and capillariesThe heart and the circulatory systemCellular respiration as an exothermic reactionAerobic and anaerobic respiration comparedInvestigating the rate of respirationCardiac output, stroke volume and heart rate
Ecosystems and Material Cycles
Topic overviewLevels of organisation and interdependenceAbiotic and biotic factors in a communityParasitism and mutualismSampling with quadrats and transectsEstimating population size from field dataEnergy transfer between trophic levelsHuman impact on ecosystems and biodiversityFood securityThe carbon cycleThe water and nitrogen cyclesFactors affecting the rate of decompositionCalculating the rate of decay
Plant Structures and Their Functions
Plant adaptations to extreme environments
- 3 things to know
- Paper 2
Overview
How desert, dry grassland and cold-climate plants reduce water loss with small leaves and spines, thick waxy cuticles, few stomata on the lower surface, stomata opened only at night or sunk in pits and surrounded by hairs, rolled leaves and needle-shaped leaves.
What you need to know
Answer each one before you reveal it.
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Key term
Explain how a cactus benefits from having leaves reduced to spines.
Key term
Explain how a thick waxy cuticle helps a plant survive where water is scarce.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Explain how having leaves with a small surface area helps a plant survive in a hot desert.
Model answer
Less surface is exposed to the air, so less water evaporates and diffuses out of the plant.
- 2
Explain how a cactus benefits from having leaves reduced to spines.
Model answer
Spines have a very small surface area, so very little water is lost, and they also protect the plant from being eaten.
- 3
Explain how a thick waxy cuticle helps a plant survive where water is scarce.
Model answer
The thick waterproof layer greatly reduces evaporation of water from the leaf surface.
- 4
Explain how having very few stomata, and only on the lower surface, helps a desert plant.
Model answer
There are fewer pores for water vapour to diffuse out of, and those there are lie on the cooler shaded side, so water loss is low.
- 5
Explain the advantage to a desert plant of opening its stomata only at night.
Model answer
Night air is cooler and more humid, so the plant can take in carbon dioxide while losing far less water.
- 6
Explain how stomata sunk into pits, or surrounded by hairs, reduce water loss.
Model answer
They trap a layer of moist air next to the pore, which lowers the concentration gradient so less water vapour diffuses away.
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