Key term
OCR GCSE Combined Science Biology J250
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesEnzyme 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 mutationsHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination and characteristics controlled by many genesVariation within a population, and classificationNatural selection and evolutionEvidence for evolution from fossils and antibiotic resistance
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, monitoring conservation and ecotourismSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesWhite blood cells, antibodies and plateletsNon-specific defences and the immune systemVaccines, 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 arcHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityHomeostasis and control systems in the bodyInsulin and glucagon in blood sugar controlType 1 and type 2 diabetes
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
Global Challenges
Non-specific defences and the immune system
- 3 things to know
- Paper 8 (Biology)
Overview
Non-specific defences including the skin, nose hairs and mucus, cilia in the airways, stomach acid, tears and scabs, why burns lead to infection, what antigens are, how lymphocytes make antibodies that clump pathogens for phagocytes, why a first infection takes days to recover from, memory cells and immunity, and why one strain of a virus may not protect against another.
What you need to know
Answer each one before you reveal it.
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Key term
How does the nose help to keep pathogens out of the lungs?
Key term
Describe how trapped pathogens are removed from the trachea and bronchi.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by a non-specific defence?
Model answer
One that acts against all pathogens in the same way, rather than being directed at one particular type.
- 2
Give two ways the skin defends the body against pathogens.
Model answer
Its outer layer of dead cells is a physical barrier, and it produces oils and secretions that kill microorganisms.
- 3
How does the nose help to keep pathogens out of the lungs?
Model answer
Hairs and sticky mucus trap pathogens and dust in the air breathed in before it reaches the lungs.
- 4
Describe how trapped pathogens are removed from the trachea and bronchi.
Model answer
Mucus made by goblet cells traps them, and cilia beat to sweep the mucus up to the back of the throat where it is swallowed.
- 5
How does the stomach defend the body against swallowed pathogens?
Model answer
It produces hydrochloric acid, which kills most pathogens taken in with food, drink and swallowed mucus.
- 6
How do tears protect the eyes from infection?
Model answer
They wash particles off the surface and contain an enzyme that destroys the cell walls of bacteria.
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