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PEARSON EDEXCEL · XBI11 / YBI11

A Level Biology units and topics

Pearson Edexcel International A Level Biology in six units. Choose a unit to explore its topics and lessons.

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First lesson: 1A 1 The Chemistry of Life

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Six units. One connected course.

Units 1–3 form International AS. Units 4–6 complete the International A Level. The practical units bring together the skills used throughout the course.

Start learning: Chemistry for Biologists

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Unit 1Molecules, Diet, Transport and HealthTopic 1 · Topic 2
Topic 1Molecules, Transport and Health3 textbook sections
1AChemistry for Biologists5 numbered lessons · textbook order
  1. 1A 1 The Chemistry of Life
  2. 1A 2 Carbohydrates 1: Monosaccharides and Disaccharides
  3. 1A 3 Carbohydrates 2: Polysaccharides
  4. 1A 4 Lipids
  5. 1A 5 Proteins
  6. Thinking Bigger: Trehalose
  7. Exam Practice
Open the 1A page
1BMammalian Transport Systems5 numbered lessons · textbook order
  1. 1B 1 The Principles of Circulation
  2. 1B 2 The Roles of the Blood
  3. 1B 3 Circulation in the Blood Vessels
  4. 1B 4 The Mammalian Heart
  5. 1B 5 Atherosclerosis
  6. Exam Practice
Open the 1B page
1CCardiovascular Health and Risk7 numbered lessons · textbook order
  1. 1C 1 Risk, Correlation and Cause
  2. 1C 2 Investigating the Causes of CVDs
  3. 1C 3 Risk Factors for Cardiovascular Disease
  4. 1C 4 Diet and Cardiovascular Health
  5. 1C 5 Dietary Antioxidants and Cardiovascular Disease
  6. 1C 6 Using the Evidence
  7. 1C 7 The Benefits and Risks of Treatment
  8. Thinking Bigger: Heart Failure
  9. Exam Practice
Open the 1C page
Open the Topic 1 page
Topic 2Membranes, Proteins, DNA and Gene Expression3 textbook sections
2AMembranes and Transport6 numbered lessons · textbook order
  1. 2A 1 Cell Membranes
  2. 2A 2 Cell Transport and Diffusion
  3. 2A 3 Osmosis: A Special Case of Diffusion
  4. 2A 4 Active Transport
  5. 2A 5 The Need for Gas Exchange Surfaces
  6. 2A 6 The Mammalian Gas Exchange System
  7. Thinking Bigger: Asthma and Air Pollution
  8. Exam Practice
Open the 2A page
2BProteins and DNA6 numbered lessons · textbook order
  1. 2B 1 Enzymes
  2. 2B 2 How Enzymes Work
  3. 2B 3 The Structure of DNA and RNA
  4. 2B 4 How DNA Works
  5. 2B 5 The Genetic Code
  6. 2B 6 DNA and Protein Synthesis
  7. Thinking Bigger: Raw Enzymes
  8. Exam Practice
Open the 2B page
2CGene Expression and Genetics5 numbered lessons · textbook order
  1. 2C 1 Gene Mutation
  2. 2C 2 Patterns of Inheritance
  3. 2C 3 Sex Linkage
  4. 2C 4 Cystic Fibrosis: A Genetic Disease
  5. 2C 5 Genetic Screening
  6. Exam Practice
Open the 2C page
Open the Topic 2 page
Open the Unit 1 page
Unit 2Cells, Development, Biodiversity and ConservationTopic 3 · Topic 4
Topic 3Cell Structure, Reproduction and Development3 textbook sections
3ACell Structure5 numbered lessons · textbook order
  1. 3A 1 Observing Cells
  2. 3A 2 Eukaryotic Cells 1: Common Cellular Structures
  3. 3A 3 Eukaryotic Cells 2: Protein Transport
  4. 3A 4 Prokaryotic Cells
  5. 3A 5 The Organisation of Cells
  6. Exam Practice
Open the 3A page
3BMitosis, Meiosis and Reproduction5 numbered lessons · textbook order
  1. 3B 1 The Cell Cycle
  2. 3B 2 Mitosis
  3. 3B 3 Sexual Reproduction and Meiosis
  4. 3B 4 Gametes: Structure and Function
  5. 3B 5 Fertilisation in Mammals and Plants
  6. Thinking Bigger: Male Infertility
  7. Exam Practice
Open the 3B page
3CDevelopment of Organisms5 numbered lessons · textbook order
  1. 3C 1 Cell Differentiation
  2. 3C 2 Interactions Between Genes and the Environment
  3. 3C 3 Controlling Gene Expression
  4. 3C 4 Stem Cells
  5. 3C 5 Using Stem Cells
  6. Thinking Bigger: Microbiota
  7. Exam Practice
Open the 3C page
Open the Topic 3 page
Topic 4Plant Structure and Function, Biodiversity and Conservation3 textbook sections
4APlant Structure and Function7 numbered lessons · textbook order
  1. 4A 1 The Cell Wall
  2. 4A 2 Plant Organelles
  3. 4A 3 Plant Stems
  4. 4A 4 The Importance of Water and Minerals in Plants
  5. 4A 5 Using Plant Starch and Fibres
  6. 4A 6 Plant-based Medicines
  7. 4A 7 Developing New Drugs
  8. Exam Practice
Open the 4A page
4BClassification3 numbered lessons · textbook order
  1. 4B 1 Principles of Classification
  2. 4B 2 What Is a Species?
  3. 4B 3 Domains, Kingdoms or Both?
  4. Thinking Bigger: The Quagga
  5. Exam Practice
Open the 4B page
4CBiodiversity and Conservation6 numbered lessons · textbook order
  1. 4C 1 Biodiversity and Endemism
  2. 4C 2 Measuring Biodiversity
  3. 4C 3 Adaptation to a Niche
  4. 4C 4 Gene Pool and Genetic Diversity
  5. 4C 5 Reproductive Isolation and Speciation
  6. 4C 6 Conservation: Why and How?
  7. Thinking Bigger: Orang-utans
  8. Exam Practice
Open the 4C page
Open the Topic 4 page
Open the Unit 2 page
Unit 3Practical Skills in Biology IAS practical skills · CP1–CP9
ASCore PracticalsPractical investigations
  1. CP1 Estimating Reducing Sugar and Starch Concentrations
  2. CP2 Vitamin C Content of Food and Drink
  3. CP3 Membrane Properties and Permeability
  4. CP4 Factors Affecting Enzyme-catalysed Reactions
  5. CP5 Animal Cells and Measurements Using a Light Microscope
  6. CP6 Mitosis in a Root Tip Squash
  7. CP7 Plant Structures and Tissues Using a Light Microscope
  8. CP8 Tensile Strength of Plant Fibres
  9. CP9 Antimicrobial Properties of Plants
Open the AS page
SkillsPlanningExam technique for planning an investigation: variables, apparatus, repeats, risk and error.
  1. P1 Variables and a fair test
  2. P2 Apparatus and the measurements you will take
  3. P3 Repeats, risk and sources of error
Open the Skills page
SkillsImplementation and MeasurementsExam technique for commenting on a method you are shown: readings, range, anomalies and records.
  1. I1 Readings, range and significant figures
  2. I2 Inconsistent readings and useful improvements
  3. I3 Drawings, scales and what to comment on
Open the Skills page
SkillsProcessing ResultsExam technique for tables, graphs, gradients, uncertainty and a conclusion that matches the evidence.
  1. R1 Tables, units and processed numbers
  2. R2 Scales, lines and gradients
  3. R3 Conclusions, uncertainty and realistic changes
Open the Skills page
Open the Unit 3 page
Unit 4Energy, Environment, Microbiology and ImmunityTopic 5 · Topic 6
Topic 5Energy Flow, Ecosystems and the Environment3 textbook sections
5APhotosynthesis3 numbered lessons · textbook order
  1. 5A 1 The Importance of ATP
  2. 5A 2 Chloroplasts and Chlorophyll
  3. 5A 3 The Biochemistry of Photosynthesis
  4. Thinking Bigger
  5. Exam Practice
Open the 5A page
5BEcology7 numbered lessons · textbook order
  1. 5B 1 What Is Ecology?
  2. 5B 2 How Ecosystems Evolve
  3. 5B 3 The Effect of Abiotic Factors on Populations
  4. 5B 4 The Effect of Biotic Factors on Populations
  5. 5B 5 Ecosystem Interactions and the Importance of the Niche
  6. 5B 6 Investigating Abundance and Distribution of Organisms
  7. 5B 7 Statistics and Ecology
  8. Exam Practice
Open the 5B page
5CEnvironment and Climate Change10 numbered lessons · textbook order
  1. 5C 1 Transfers Between Trophic Levels
  2. 5C 2 Net Primary Productivity
  3. 5C 3 The Carbon Cycle in Nature
  4. 5C 4 Greenhouse Gases and Climate Change
  5. 5C 5 Looking at the Evidence
  6. 5C 6 The Global Warming Debate: Correlation or Causation?
  7. 5C 7 Models of Climate Change and Their Limitations
  8. 5C 8 The Biological Impact of Climate Change
  9. 5C 9 Climate Change and Evolution
  10. 5C 10 What Can Be Done?
  11. Thinking Bigger
  12. Exam Practice
Open the 5C page
Open the Topic 5 page
Topic 6Microbiology, Immunity and Forensics3 textbook sections
6AMicrobiology8 numbered lessons · textbook order
  1. 6A 1 Bacteria and Viruses
  2. 6A 2 How Viruses Reproduce
  3. 6A 3 The Growth of Bacterial Colonies
  4. 6A 4 Microbial Techniques
  5. 6A 5 Measuring the Growth of Bacterial Cultures
  6. 6A 6 Invading the Body
  7. 6A 7 Case Studies of Disease: Tuberculosis
  8. 6A 8 Case Studies of Disease: HIV/AIDS
  9. Thinking Bigger
  10. Exam Practice
Open the 6A page
6BImmunity5 numbered lessons · textbook order
  1. 6B 1 Non-specific Responses to Infection
  2. 6B 2 The Specific Response to Infection
  3. 6B 3 Developing Immunity
  4. 6B 4 Antibiotics: Treating Bacterial Disease
  5. 6B 5 Antibiotic Resistance
  6. Thinking Bigger
  7. Exam Practice
Open the 6B page
6CDecomposition and Forensics5 numbered lessons · textbook order
  1. 6C 1 Microorganisms and Decomposition
  2. 6C 2 Forensic Science and the Time of Death
  3. 6C 3 The Process of Decay
  4. 6C 4 Polymerase Chain Reaction (PCR)
  5. 6C 5 DNA Profiling
  6. Thinking Bigger
  7. Exam Practice
Open the 6C page
Open the Topic 6 page
Open the Unit 4 page
Unit 5Respiration, Internal Environment, Coordination and Gene TechnologyTopic 7 · Topic 8
Topic 7Respiration, Muscles and the Internal Environment3 textbook sections
7ACellular Respiration5 numbered lessons · textbook order
  1. 7A 1 Respiration in Cells
  2. 7A 2 Glycolysis and Anaerobic Respiration
  3. 7A 3 The Krebs Cycle
  4. 7A 4 The Electron Transport Chain
  5. 7A 5 Respiratory Substrates and Respiratory Quotient
  6. Exam Practice
Open the 7A page
7BMuscles, Movement and the Heart8 numbered lessons · textbook order
  1. 7B 1 Tissues of the Skeletal System
  2. 7B 2 What Is Muscle?
  3. 7B 3 Different Types of Muscle Fibre
  4. 7B 4 How Muscles Contract
  5. 7B 5 Cardiac Muscle and Control of the Heartbeat
  6. 7B 6 Principles of Homeostasis
  7. 7B 7 Controlling the Heart and Breathing Rates
  8. 7B 8 The Response of the Breathing System to Exercise
  9. Thinking Bigger
  10. Exam Practice
Open the 7B page
7CControl of the Internal Environment4 numbered lessons · textbook order
  1. 7C 1 Homeostasis and Hormones
  2. 7C 2 Osmoregulation in Mammals: The Kidney
  3. 7C 3 Control of the Kidney and Homeostasis
  4. 7C 4 Thermoregulation and Exercise
  5. Thinking Bigger
  6. Exam Practice
Open the 7C page
Open the Topic 7 page
Topic 8Coordination, Response and Gene Technology3 textbook sections
8AThe Nervous System and Neurones6 numbered lessons · textbook order
  1. 8A 1 The Structure of Neurones
  2. 8A 2 How the Nervous System Works
  3. 8A 3 The Neurones in Action
  4. 8A 4 The Effect of Drugs on the Nervous System
  5. 8A 5 Sensory Systems and the Detection of Light
  6. 8A 6 Synapses and Habituation
  7. Exam Practice
Open the 8A page
8BCoordination in Animals and Plants7 numbered lessons · textbook order
  1. 8B 1 The Central Nervous System
  2. 8B 2 The Peripheral Nervous System
  3. 8B 3 Investigating the Human Brain
  4. 8B 4 The Chemical Balance of the Brain
  5. 8B 5 Chemical Control Systems in Plants
  6. 8B 6 Phytochrome and Flowering
  7. 8B 7 Phytochrome and Transcription
  8. Thinking Bigger
  9. Exam Practice
Open the 8B page
8CGene Technology4 numbered lessons · textbook order
  1. 8C 1 Producing Recombinant DNA
  2. 8C 2 Drugs from Genetically Modified Organisms
  3. 8C 3 Microarrays and Bioinformatics
  4. 8C 4 Benefits and Risks of GMOs
  5. Thinking Bigger
  6. Exam Practice
Open the 8C page
Open the Topic 8 page
Open the Unit 5 page
Unit 6Practical Skills in Biology IIA level practical skills · CP10–CP18
IA2Core PracticalsPractical investigations
  1. CP10 Factors Affecting the Rate of Photosynthesis
  2. CP11 The Ecology of a Habitat
  3. CP12 Temperature and the Development of Organisms
  4. CP13 Growth of Microorganisms in Liquid Culture
  5. CP14 The Effect of Antibiotics on Bacteria
  6. CP15 Respiration in Yeast
  7. CP16 Rate of Respiration and Respiratory Quotient
  8. CP17 Exercise and Respiratory Measurements
  9. CP18 Amylase Production in Germinating Cereal Grains
Open the IA2 page
SkillsPlanningExam technique for planning a Unit 6 investigation: a null hypothesis, apparatus, calibration, repeats, risk and ethics.
  1. P1 A null hypothesis and the variables
  2. P2 Apparatus, calibration and the data you will use
  3. P3 Repeats, risk and living organisms
Open the Skills page
SkillsImplementation and MeasurementsExam technique for commenting on a method you are shown: readings, range, figures, units and improvements.
  1. I1 Readings, range and significant figures
  2. I2 Wrong units and a point that does not fit
  3. I3 Improvements that reduce a named error
Open the Skills page
SkillsAnalysisExam technique for tables, graphs including a log scale, patterns, uncertainty and realistic modifications.
  1. A1 Tables, units and processed numbers
  2. A2 Scales, log axes and gradients
  3. A3 Patterns, tests and realistic changes
Open the Skills page
Open the Unit 6 page