Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesProtein synthesis and the triplet codeEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHow genetic variants influence phenotypeAsexual and sexual reproduction comparedHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination, multiple genes and Mendel's workVariation within a population, and classificationNatural selection and evolutionEvidence for evolution, and the work of Darwin and Wallace
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, and evidence for environmental changeFood security, agricultural and biotechnological solutionsSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesPhysical and chemical plant defencesDetecting plant disease; white blood cells and plateletsNon-specific defences and the immune systemMonoclonal antibodies and their usesVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Topic overviewThe nervous system and coordinated responsesThe reflex arcThe eye and its common defectsThe structure and function of the brainInvestigating and treating the brainHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityPlant hormones and their commercial usesHomeostasis, and the skin in temperature controlInsulin and glucagon in blood sugar controlType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysThe kidney tubule and the effect of ADHResponding to temperature and osmotic challenges
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Organism Level Systems
Plant hormones and their commercial uses
- 3 things to know
- Paper 3
Overview
What tropisms are and how auxin makes shoots bend towards light and roots grow downwards, why these responses help the plant, the processes plant hormones control, the roles of ethene, gibberellins and auxins, and their commercial uses in selective weedkillers, rooting powder, seedless fruit and ending seed dormancy for brewing.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What are phototropism and gravitropism?
Evaluation
Why is it an advantage to a plant for its shoots to grow towards the light?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a tropism?
Model answer
A growth response of a plant in which the direction of growth is set by the direction of the stimulus.
- 2
What are phototropism and gravitropism?
Model answer
Phototropism is a plant's growth response to light and gravitropism is its growth response to gravity.
- 3
Where is auxin made in a growing shoot?
Model answer
In the tip of the shoot.
- 4
Explain how the unequal distribution of auxin makes a shoot bend towards light coming from one side.
Model answer
Auxin moves to the shaded side, where it makes the cells elongate more than those on the lit side, so that side grows longer and the shoot bends towards the light.
- 5
Why is it an advantage to a plant for its shoots to grow towards the light?
Model answer
The leaves receive more light, so the plant can photosynthesise faster and grow better.
- 6
Explain why a root grows downwards when a seed germinates on its side.
Model answer
Auxin collects on the lower side of the root, where it slows down cell elongation, so the upper side grows faster and the root curves downwards.
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