bio letters

IB biology notes

NEW UPDATES: 27th December, 2025
10 topic notes left to go
topic notes should be done by early January 2026

Question Bank

A4.1 Paper 1A
[MARKSCHEME]

B2.3 Paper 1A
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NEW

B1.1 Paper 1A
[MARKSCHME]

C4.1 Paper 1A
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C4.2 Paper 1A
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C4.2 Paper 2
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Notes

A1.1 Water

A1.2 Nucleic acids

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

NEW

B3.3 Muscle and motility

B4.1 Adaptation to environment

B4.2 Ecological niches

C1.1 Enzymes and metabolism
C1.2 Cell respiration
C1.3 Photosynthesis
C2.1 Chemical signalling
C2.2 Neural signalling
C3.1 Integration of body systems

C3.2 Defence against disease
C4.1 Populations and communities

C4.2 Transfer of energy and matter

D1.1 DNA replication
D1.2 Protein synthesis

D1.3 Mutation and gene editing

D2.2 Gene expression
D3.1 Reproduction
D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection