Key term
OCR A-Level Biology B H422
The Developing Cell: Cell Division and Cell Differentiation
The Developing Individual: Meiosis, Growth and Development
The Development of Species: Evolution and Classification
Cells and Microscopy
Topic overviewMicroscopy and the cell theoryBlood smears, staining and microscope drawingsBlood cells and their structureMagnification and measuring cellsHaemocytometer cell counts and dilutionsFlow cytometry in blood analysisUltrastructure of the animal cellPlant and prokaryotic cellsMembrane lipids and the fluid mosaic modelMovement of molecules across membranesThe roles of membranes and the secretion of proteins
Water and Its Importance in Plants and Animals
Proteins and Enzymes
Nucleic Acids
Patterns of Inheritance
Population Genetics and Epigenetics
Gene Technologies
The Principles and Importance of Homeostasis
The Hormonal Control of Blood Glucose and the Management of Diabetes
Kidney Functions and Malfunctions
Topic overviewExcretion and the gross structure of the kidneyThe nephron: ultrafiltration and selective reabsorptionInvestigating the composition of urine, plasma and filtrateOsmoregulation and the action of ADHThe kidney as an endocrine gland and kidney failureDialysis, transplantation and the future of transplant surgery
The Cellular Basis of Cancer and Treatment
Respiratory Diseases and Treatment
Cellular Respiration
Metabolism and Exercise
Topic overviewThe consequences of exercise on the bodyAerobic fitness and VO₂ maxTraining, F.I.T.T. factors and investigating fitnessEnhancing athletic performanceHaemoglobin and the transport of oxygenOxygen dissociation curves of different respiratory pigmentsOxygen deficit and oxygen debtThe structure of skeletal muscleThe sliding filament theory of muscle contraction
Pathogenic Microorganisms
The Immune System
Controlling Communicable Diseases
Photosynthesis, Food Production and Management of the Environment
Topic overviewChloroplast ultrastructure and photosynthetic pigmentsThe light-dependent stage of photosynthesisThe Calvin cycleInvestigating the factors affecting photosynthesisThe Hill reaction and DCPIPUsing TP and GP to build carbohydrates, lipids and amino acidsThe compensation point and crop productionMicroorganisms, the nitrogen cycle and biosensorsBiomass transfer and efficiency in food productionRuminants in the human food chainFarms as ecosystems and the conflict with conservationDeflected succession and measuring biodiversity
The Impact of Population Increase
Planning and Implementing Practical Work
Analysing and Evaluating Practical Results
Practical Skills, Apparatus and Techniques
Topic overviewInvestigative approaches and working safelyFollowing instructions, recording and presenting dataResearch, referencing and processing data with softwareMeasuring mass, volume, time, temperature, length and pHColorimeters and potometersLaboratory glassware and serial dilutionsLight microscopy, graticules and biological drawingQualitative reagents for biological moleculesChromatography and electrophoresisAseptic technique and dissectionWhole-organism responses, fieldwork sampling and data logging
Fertility and Assisted Reproduction
The Effects of Ageing on the Reproductive System
Plant Reproduction
The Nervous System and the Identification and Consequences of Damage
Topic overviewOrganisation of the nervous system and nervous tissueThe structure and function of the human brainThe structure of motor, sensory and relay neuronesResting potential and the action potentialSynapses and the integration of responsesReflexes, reaction times and their investigationBrain scans and the consequences of nervous system damageDrugs, brain function and dependency
Monitoring Visual Function
The Effect of Ageing on the Nervous System
The Heart and Monitoring Heart Function
Transport Systems in Mammals
Gas Exchange in Mammals and Plants
Practical Skills, Apparatus and Techniques
Light microscopy, graticules and biological drawing
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on using objective lenses, focus and the iris diaphragm, field of view and total magnification, calibrating an eyepiece graticule with a stage micrometer and measuring cells, the magnification of a drawing, drawing conventions, low power plans and high power drawings, and labels and annotations.
What you need to know
Answer each one before you reveal it.
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Key term
Why is the coarse focus never used with the high power objective?
Key term
How is the field of view brightened when the microscope is switched from low to high power?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the order in which the objective lenses are used when a slide is examined.
Model answer
The lowest power objective is used first to locate the specimen, and only then is a higher power selected.
- 2
Why is the coarse focus never used with the high power objective?
Model answer
The lens is very close to the slide and could be driven into it, breaking the coverslip and damaging the objective.
- 3
How is the field of view brightened when the microscope is switched from low to high power?
Model answer
The iris diaphragm is opened further or the lamp is turned up, because the higher power objective admits less light.
- 4
What happens to the field of view when the objective is changed from ×10 to ×40?
Model answer
Its diameter becomes four times smaller, so a smaller area of the specimen is visible.
- 5
Calculate the total magnification when a ×10 eyepiece is used with a ×40 objective.
Model answer
The total magnification is ×400.
- 6
What is an eyepiece graticule?
Model answer
It is a scale etched onto a small disc placed in the eyepiece, whose divisions appear superimposed on the specimen.
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