Book a tutor
SearchResourcesRevision notesFlashcardsMind mapsExam questionsTopic testsPracticalsGCSE Biology coursesAQA GCSE Biology (8461)AQA GCSE Combined Science: Trilogy (8464)Edexcel GCSE Biology (1BI0)Edexcel GCSE Combined Science (1SC0)IGCSE Biology coursesCambridge IGCSE Biology (0610)Cambridge IGCSE Combined Science (0653)Edexcel International GCSE Biology (4BI1)Edexcel International GCSE Science (Double Award) (4SD0)IB Diploma Biology coursesIB Diploma Biology SLIB Diploma Biology HLMoreVideosAboutContact
Book a tutor

IB Diploma Biology SL revision notes

Short notes for every spec point. Pick a topic, then a note.

A1

Molecules (Unity and diversity)

2 subtopics · 8 notes

Water
  1. Subtopic overview: questions, flashcards and PDFs
  2. Water as the medium for life and hydrogen bonding
  3. Cohesion and adhesion
  4. Solvent properties of water
  5. Physical properties of water and aquatic animals
Nucleic acids
  1. Subtopic overview: questions, flashcards and PDFs
  2. DNA as the genetic material and nucleotides
  3. RNA polymers and the DNA double helix
  4. Differences between DNA and RNA
  5. Base pairing, information storage and the genetic code
All molecules (unity and diversity) notes (PDF)Download all notes (PDF)11 pages
A4

Ecosystems (Unity and diversity)

2 subtopics · 8 notes

Evolution and speciation
  1. Subtopic overview: questions, flashcards and PDFs
  2. Evolution as change in heritable characteristics
  3. Evidence from sequences and selective breeding
  4. Homologous and analogous structures
  5. Speciation, reproductive isolation and differential selection
Conservation of biodiversity
  1. Subtopic overview: questions, flashcards and PDFs
  2. Biodiversity and the number of species
  3. Anthropogenic species extinction and ecosystem loss
  4. Evidence for and causes of the biodiversity crisis
  5. Approaches to conservation and the EDGE of Existence programme
All ecosystems (unity and diversity) notes (PDF)Download all notes (PDF)13 pages
B1

Molecules (Form and function)

2 subtopics · 11 notes

Carbohydrates and lipids
  1. Subtopic overview: questions, flashcards and PDFs
  2. Carbon atoms and the diversity of carbon compounds
  3. Condensation and hydrolysis reactions
  4. Monosaccharides: form and function
  5. Starch, glycogen and cellulose
  6. Glycoproteins and cell–cell recognition
  7. Lipids: hydrophobic properties, triglycerides and phospholipids
  8. Fatty acids, energy storage and insulation
  9. Phospholipid bilayers and steroids
Proteins
  1. Subtopic overview: questions, flashcards and PDFs
  2. Amino acids and peptide bonds
  3. Dietary amino acids and the variety of peptide chains
  4. Effect of pH and temperature on protein structure
All molecules (form and function) notes (PDF)Download all notes (PDF)17 pages
B2

Cells (Form and function)

3 subtopics · 6 notes

Membranes and membrane transport
  1. Subtopic overview: questions, flashcards and PDFs
  2. Lipid bilayers, barriers and simple diffusion
  3. Osmosis, channel proteins and pump proteins
  4. Membrane proteins, glycoproteins and the fluid mosaic model
Organelles and compartmentalization
  1. Subtopic overview: questions, flashcards and PDFs
  2. Organelles, the nucleus and compartments
Cell specialization
  1. Subtopic overview: questions, flashcards and PDFs
  2. Differentiation and stem cells
  3. Cell size and surface area-to-volume ratio
All cells (form and function) notes (PDF)Download all notes (PDF)13 pages
B3

Organisms (Form and function)

2 subtopics · 10 notes

Gas exchange
  1. Subtopic overview: questions, flashcards and PDFs
  2. Gas exchange and exchange surfaces
  3. Adaptations of mammalian lungs
  4. Ventilation and lung volumes
  5. Gas exchange in leaves
  6. Transpiration and stomatal density
Transport
  1. Subtopic overview: questions, flashcards and PDFs
  2. Adaptations of capillaries
  3. Structure and adaptations of arteries and veins
  4. Pulse rates and occlusion of the coronary arteries
  5. Water transport in xylem
  6. Tissues in dicotyledonous stems and roots
All organisms (form and function) notes (PDF)Download all notes (PDF)14 pages
B4

Ecosystems (Form and function)

2 subtopics · 12 notes

Adaptation to environment
  1. Subtopic overview: questions, flashcards and PDFs
  2. Habitats and adaptations to the abiotic environment
  3. Abiotic variables and range of tolerance
  4. Conditions required for coral reef formation
  5. Terrestrial biomes
  6. Adaptations to hot deserts and tropical rainforest
Ecological niches
  1. Subtopic overview: questions, flashcards and PDFs
  2. Ecological niche and tolerance of oxygen
  3. Photosynthesis and mixotrophic nutrition
  4. Holozoic and saprotrophic nutrition, and archaea
  5. Dentition and diet in the Hominidae
  6. Adaptations for herbivory and predation
  7. Adaptations of plant form for harvesting light
  8. Fundamental and realized niches, and competitive exclusion
All ecosystems (form and function) notes (PDF)Download all notes (PDF)16 pages
C1

Molecules (Interaction and interdependence)

3 subtopics · 12 notes

Enzymes and metabolism
  1. Subtopic overview: questions, flashcards and PDFs
  2. Enzymes as catalysts and their role in metabolism
  3. Active sites, induced fit, collisions and denaturation
  4. Effects of temperature, pH and substrate concentration
  5. Effect of enzymes on activation energy
Cell respiration
  1. Subtopic overview: questions, flashcards and PDFs
  2. ATP: the molecule that distributes energy
  3. Cell respiration: aerobic and anaerobic
  4. Variables affecting the rate of cell respiration
Photosynthesis
  1. Subtopic overview: questions, flashcards and PDFs
  2. Photosynthesis: energy, carbon dioxide, water and oxygen
  3. Separating photosynthetic pigments by chromatography
  4. Absorption of light, absorption spectra and action spectra
  5. Investigating limiting factors on photosynthesis
  6. Carbon dioxide enrichment experiments
All molecules (interaction and interdependence) notes (PDF)Download all notes (PDF)17 pages
C3

Organisms (Interaction and interdependence)

2 subtopics · 14 notes

Integration of body systems
  1. Subtopic overview: questions, flashcards and PDFs
  2. System integration and the hierarchy of subsystems
  3. The brain, spinal cord, neurons and nerves
  4. Pain reflex arcs and the cerebellum
  5. Melatonin, epinephrine and control by the hypothalamus and pituitary
  6. Feedback control of heart rate and ventilation rate
  7. Control of peristalsis by the CNS and enteric nervous system
Defence against disease
  1. Subtopic overview: questions, flashcards and PDFs
  2. Pathogens as the cause of infectious diseases
  3. Skin, mucous membranes and blood clotting
  4. Innate and adaptive immunity, and phagocytes
  5. Lymphocytes, antigens and antibody production
  6. Immunity, vaccines and herd immunity
  7. HIV transmission and AIDS
  8. Antibiotics and antibiotic resistance
  9. Zoonoses and evaluating COVID-19 data
All organisms (interaction and interdependence) notes (PDF)Download all notes (PDF)18 pages
C4

Ecosystems (Interaction and interdependence)

2 subtopics · 18 notes

Populations and communities
  1. Subtopic overview: questions, flashcards and PDFs
  2. Populations and random sampling
  3. Capture–mark–release–recapture and the Lincoln index
  4. Carrying capacity and density-dependent factors
  5. Population growth curves
  6. Intraspecific and interspecific relationships
  7. Mutualism
  8. Invasive species and testing for competition
  9. Predator–prey relationships and control of populations
  10. Allelopathy and secretion of antibiotics
Transfers of energy and matter
  1. Subtopic overview: questions, flashcards and PDFs
  2. Ecosystems as open systems and the source of energy
  3. Food chains, food webs and decomposers
  4. Autotrophs and heterotrophs
  5. Trophic levels and energy pyramids
  6. Energy losses between trophic levels
  7. Primary and secondary production
  8. The carbon cycle, carbon sinks and combustion
  9. The Keeling Curve
  10. Interdependence of autotrophs and heterotrophs and recycling of elements
All ecosystems (interaction and interdependence) notes (PDF)Download all notes (PDF)21 pages
D1

Molecules (Continuity and change)

3 subtopics · 11 notes

DNA replication
  1. Subtopic overview: questions, flashcards and PDFs
  2. Exact copies by semi-conservative replication
  3. Roles of helicase and DNA polymerase
  4. PCR and gel electrophoresis
  5. Applications of PCR and gel electrophoresis
Protein synthesis
  1. Subtopic overview: questions, flashcards and PDFs
  2. Transcription and gene expression
  3. Translation at the ribosome
  4. The genetic code
  5. Mutations that change protein structure
Mutation and gene editing
  1. Subtopic overview: questions, flashcards and PDFs
  2. Substitutions, insertions and deletions
  3. Causes of mutation and randomness
  4. Germ and somatic cells, and mutation as a source of variation
All molecules (continuity and change) notes (PDF)Download all notes (PDF)16 pages
D2

Cells (Continuity and change)

2 subtopics · 7 notes

Cell and nuclear division
  1. Subtopic overview: questions, flashcards and PDFs
  2. Cell division and cytokinesis
  3. Mitosis, meiosis and chromosome movement
  4. Phases of mitosis
  5. Meiosis, non-disjunction and variation
Water potential
  1. Subtopic overview: questions, flashcards and PDFs
  2. Solvation and osmosis
  3. Osmosis in plant tissue: the practical
  4. Water movement in cells with and without walls
All cells (continuity and change) notes (PDF)Download all notes (PDF)13 pages
D3

Organisms (Continuity and change)

3 subtopics · 18 notes

Reproduction
  1. Subtopic overview: questions, flashcards and PDFs
  2. Sexual and asexual reproduction
  3. Male and female sexes and human reproductive systems
  4. Ovarian and uterine cycles and their hormones
  5. Fertilization in humans and hormones in IVF
  6. Sexual reproduction in flowering plants and insect-pollinated flowers
  7. Cross-pollination and self-incompatibility
  8. Seed dispersal and germination
Inheritance
  1. Subtopic overview: questions, flashcards and PDFs
  2. Haploid gametes, diploid zygotes and genetic crosses in plants
  3. Genotype, phenotype, dominance and phenotypic plasticity
  4. Phenylketonuria, SNPs, multiple alleles and ABO blood groups
  5. Incomplete dominance and codominance
  6. Sex determination, sex linkage and haemophilia
  7. Pedigree charts
  8. Continuous variation and box-and-whisker plots
Homeostasis
  1. Subtopic overview: questions, flashcards and PDFs
  2. Homeostasis and negative feedback
  3. Regulation of blood glucose
  4. Type 1 and type 2 diabetes
  5. Thermoregulation
All organisms (continuity and change) notes (PDF)Download all notes (PDF)26 pages
D4

Ecosystems (Continuity and change)

3 subtopics · 17 notes

Natural selection
  1. Subtopic overview: questions, flashcards and PDFs
  2. Natural selection as the mechanism of evolution
  3. Mutation and sexual reproduction as sources of variation
  4. Overproduction, competition and selection pressures
  5. Sexual selection and Endler's guppies
Stability and change
  1. Subtopic overview: questions, flashcards and PDFs
  2. Stability of natural ecosystems
  3. Amazon deforestation as a possible tipping point
  4. Mesocosms and keystone species
  5. Sustainable harvesting and agriculture
  6. Eutrophication
  7. Biomagnification of pollutants
  8. Microplastic and macroplastic pollution of the oceans
  9. Rewilding
Climate change
  1. Subtopic overview: questions, flashcards and PDFs
  2. Anthropogenic causes and positive feedback
  3. Boreal forest tipping point and polar habitat change
  4. Nutrient upwelling and threats to coral reefs
  5. Poleward and upslope range shifts
  6. Afforestation, forest regeneration and peatland restoration
All ecosystems (continuity and change) notes (PDF)Download all notes (PDF)18 pages