Biology
Comprehensive study guides aligned with the IB 2025 Biology syllabus.
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Cell Biology & Ultrastructure
Start here → ~20 min readCovers cell origins, prokaryote vs eukaryote ultrastructure, organelle functions, and the cell cycle including mitosis.
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Form & Function — Physiology
~25 min readCovers gas exchange, blood transport in mammals, and immune defence mechanisms including innate and adaptive immunity.
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IB Biology HL Enzymes & Cell Biology — C1.1, A1.1, D1.1
~22 min readCovers enzyme kinetics, inhibition, metabolic pathways, and how cell structure supports metabolic function.
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IB Bio HL Photosynthesis & Respiration — Notes + MCQs 2026
~28 min readCovers glycolysis, the Krebs cycle, oxidative phosphorylation, the light-dependent reactions, and the Calvin cycle.
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DNA Replication & Gene Expression
~25 min readCovers DNA replication, transcription, translation, and the regulation of gene expression including epigenetics.
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Meiosis, Genetics & Inheritance
~25 min readCovers meiosis, Mendelian genetics, dihybrid crosses, linkage, and sex-linked inheritance patterns.
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Neural Signaling & Homeostasis
~25 min readCovers action potentials, synaptic transmission, hormonal homeostasis, blood glucose regulation, and system integration.
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Ecology: Populations, Communities & Energy Transfer
~22 min readCovers population dynamics, community interactions, food webs, nutrient cycling, and energy transfer through ecosystems.
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Biochemistry: Carbohydrates, Lipids & Proteins
~22 min readCovers the structure and function of carbohydrates, lipids, proteins, and HL biochemical separation techniques.
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Evolution, Biodiversity & Conservation
~20 min readCovers natural selection, speciation, cladistics, taxonomy, and strategies for conserving biodiversity.
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Muscle Contraction, Adaptation & Ecological Niches
~20 min readCovers the sliding filament model of muscle contraction, environmental adaptation, and ecological niche theory.
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IB Biology HL: Mutations, Gene Editing, Reproduction & Water Potential
~30 min readCovers mutations, CRISPR gene editing, water potential, sexual reproduction, and HL gene expression regulation.