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IB Biology›Biology SL
Revision Notes

IB Biology SL

Clear, student-friendly revision notes for IB Biology Standard Level — from the molecules of life all the way to genetics and ecosystems, each with worked examples and exam pointers for Papers 1 and 2.

Biology SL · Revision Notes

Table of Contents

Click any topic to expand and view all the notes inside.

1

Life’s Building Blocks & Variety

Water, DNA, cell structure, the diversity of life, evolution and conservation.

30 notes▾

Water & Its Properties

2▾
Hydrogen Bonds→ Water’s Physical & Chemical Properties→

DNA, RNA & the Genetic Code

3▾
Structure of DNA & RNA→ The Basis of the Genetic Code→ Nucleic Acid Structure & Function→

Cell Structure & Microscopy

10▾
Cell Theory→ Cell Theory (Skills)→ Microscopes→ General Cell Structure→ Prokaryotic Cell Structure→ Eukaryotic Cell Structure→ Functions of Life→ Eukaryotic Cells: Comparisons & Atypical Examples→ Cell Types & Structures (Skills)→ Drawing Cells (Skills)→

Classifying Living Diversity

6▾
The Biological Species Concept→ Chromosome Number→ Karyograms (Skills)→ Genomes→ Comparing Genome Sizes (Skills)→ Uses of Genome Sequencing→

Evolution & Speciation

4▾
Evolution→ Evidence for Evolution→ Convergent Evolution→ Speciation→

Protecting Biodiversity

5▾
Biodiversity→ Causes of Extinction→ Ecosystem Loss→ Loss of Biodiversity→ Preserving Biodiversity→
2

Structure & Function in Living Things

The molecules and structures of life — membranes, organelles, gas exchange, transport and adaptation.

43 notes▾

Carbohydrates & Lipids

7▾
Properties of Carbon→ Macromolecules→ Carbohydrates: Function & Examples→ The Role of Glycoproteins→ Lipids→ Fatty Acids→ Phospholipids→

Proteins & Their Structure

3▾
How Proteins Form→ The Variety of Proteins→ Protein Structure: pH & Temperature→

Cell Membranes & Transport

5▾
Lipid Bilayers→ Membrane Proteins→ Membrane Transport→ Glycolipids & Glycoproteins→ The Fluid Mosaic Model (Skills)→

Organelles & Compartments

2▾
Cell Organelles→ Cell Compartmentalisation→

Specialised Cells & Stem Cells

2▾
Stem Cells→ Cell Specialisation→

Gas Exchange Systems

7▾
Gas Exchange in Organisms→ Adaptations of Mammalian Lungs→ How Ventilation Works→ Measuring Lung Volumes (Skills)→ Gas Exchange in Plants→ Drawing Leaf Structure (Skills)→ Determining Stomatal Density (Skills)→

Transport in Animals & Plants

7▾
Blood Vessels→ Identifying Blood Vessels (Skills)→ Measuring Pulse Rate (Skills)→ Coronary Heart Disease (Skills)→ The Transpiration Stream→ Xylem Vessel Adaptations→ Drawing Root & Stem Structure (Skills)→

Adapting to the Environment

5▾
Habitats→ Abiotic Factors & Distribution→ Species Distribution (Skills)→ Abiotic Factors: Marine & Terrestrial→ Biomes→

Ecological Niches & Nutrition

5▾
Ecological Niches→ Methods of Nutrition→ Nutrition in Hominidae (Skills)→ Nutritional Adaptations→ Competition Between Species→
3

Interactions & Ecosystems

How life processes connect — enzymes, energy, signalling, immunity and ecosystems.

53 notes▾

Enzymes & Metabolism

5▾
Metabolism: Enzymes & Reactions→ How Enzymes Work→ Enzyme Activity (Skills)→ Enzyme Reaction Rates (Skills)→ Activation Energy (Skills)→

Cellular Respiration

3▾
Adenosine Triphosphate (ATP)→ Cell Respiration→ Cell Respiration (Skills)→

Photosynthesis

6▾
The Process of Photosynthesis→ Separating Photosynthetic Pigments (Skills)→ Absorption Spectra→ Absorption & Action Spectra (Skills)→ Limiting Factors of Photosynthesis (Skills)→ CO₂ Enrichment Experiments→

Nerves & Signalling

4▾
Neurones: Structure & Function→ Nerve Impulses→ Nerve Impulses (Skills)→ Synapses→

Coordinating Body Systems

5▾
Integration in Living Organisms→ The Nervous System→ Reflex Arcs & Movement Control→ Epinephrine & Melatonin→ Control Mechanisms→

Disease & Immunity

12▾
Pathogens→ Pathogen Barriers: Skin & Mucous Membranes→ Blood Clotting→ The Immune System→ White Blood Cells→ The Adaptive Immune Response→ HIV & AIDS→ Antibiotics→ Antibiotic Resistance→ Zoonoses→ Vaccines & Immunity→ Evaluating COVID-19 Data (Skills)→

Populations & Communities

9▾
Populations in Ecosystems→ Estimating Population Size→ What Limits Population Size→ Limiting Population Size: Examples→ Population Growth Curves (Skills)→ Intraspecific Relationships→ Interspecific Relationships→ Interspecific Competition→ Chi-Squared Test (Skills)→

Energy & Matter in Ecosystems

9▾
Ecosystems as Open Systems→ Energy Flow in Ecosystems→ Obtaining Carbon Compounds→ Trophic Levels→ Pyramids of Energy (Skills)→ Energy Losses→ Primary & Secondary Production→ The Carbon Cycle→ Nutrient Cycling→
4

Genetics, Inheritance & Change

Passing on life — replication, protein synthesis, division, inheritance and balance.

47 notes▾

Replicating DNA

3▾
DNA Replication→ Electrophoresis & PCR→ Electrophoresis & PCR: Applications→

Making Proteins

4▾
Transcription→ Translation→ The Genetic Code→ Protein Structure & Mutations→

Mutations & Gene Editing

3▾
Gene Mutations→ Consequences of Mutations→ Mutations & Genetic Variation→

Cell & Nuclear Division

5▾
Cell Division→ Nuclear Division→ Mitosis→ Mitosis (Skills)→ Meiosis→

Osmosis & Water Potential

3▾
Osmosis→ Osmosis in Cells→ Osmosis (Skills)→

Reproduction

7▾
Sexual & Asexual Reproduction→ Sexual Reproduction→ The Menstrual Cycle→ Fertilisation→ Plant Reproduction→ Pollination→ Seed Dispersal & Germination→

Genetics & Inheritance

6▾
Genetic Inheritance & Crosses→ Inheritance: Key Terms→ Inheriting Alleles→ Sex Determination→ Pedigree Charts→ Continuous Variation (Skills)→

Homeostasis

3▾
Homeostasis: The Internal Environment→ Blood Glucose Regulation→ Thermoregulation→

Natural Selection

3▾
Natural Selection & Evolution→ Selection Pressures→ Selection Pressures (Skills)→

Ecosystem Stability & Change

7▾
Stability in Ecosystems→ Ecosystem Stability (Skills)→ Keystone Species→ Sustainable Ecosystems & Agriculture→ Eutrophication→ The Effects of Pollution→ Restoring Ecosystems→

Climate Change

3▾
Causes of Climate Change→ Impacts of Climate Change→ Carbon Sequestration→
5

Practical Skills Toolkit

The hands-on methods, tech and maths every biology experiment relies on.

9 notes▾

Skill Set 1: Experimental Technique

3▾
Safety, Ethics & the Environment→ Measuring Variables→ Applying Lab Techniques→

Skill Set 2: Using Technology

2▾
Using Tech to Collect Data→ Using Tech to Process Data→

Skill Set 3: Maths for Biology

4▾
Maths Skills for Biology→ Units, Symbols & Values→ Handling Uncertainties→ Graphing Skills→
6

The Scientific Inquiry Cycle

Working like a scientist, from first question to final evaluation.

8 notes▾

Stage 1: Explore & Design

3▾
Exploring a Problem→ Designing an Investigation→ Controlling Variables→

Stage 2: Collect & Process Data

3▾
Collecting Data→ Processing Data→ Interpreting Results→

Stage 3: Conclude & Evaluate

2▾
Drawing Conclusions→ Evaluating the Method→

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