IB Biology Syllabus + Topics

Whether you're a current IB Biology student looking to get a deeper grasp of the syllabus or a prospective IB student weighing your science options, this post will be your guide. We'll break down the IB Biology syllabus to give you a clear understanding of what to expect in the course. 

IB Biology Syllabus + Topics

The IB Biology syllabus is divided into four themes:

• Theme A: Unity and diversity

   

• Theme B: Form and function 

   

• Theme C: Interaction and interdependence

   

• Theme D: Continuity and change 

Each theme consists of a variety of topic, but at the core of them all is the study of molecules, cells, organisms, and ecosystems, which serve as the foundation of the entire course.

Theme A: Unity and diversity 

In this theme, you will explore the following topics:

• Water – where you will explore the essential molecule that forms the foundation of life. You will explore the following:
  • Hydrogen bonds
  • Adhesive and cohesive properties of water
  • Physical and solvent properties of water
  • Extraplanetary origin of water (HL only)

• Nucleic acids – where you'll uncover the vital molecules that store and transmit genetic information. In this topic, you will focus on these key concepts:
  • DNA and RNA
  • Nucleotides
  • Directionality of RNA and DNA (HL only)
  • Purine-to-pyrimidine bonding (HL only)
  • Nucleosome structure (HL only)

• Origins of cells (HL only) – where you'll delve into the theories and processes that explain how the very first cells emerged and gave rise to all life forms. You will cover the following: 
  • Pre-biotic formation of carbon compounds
  • Cells as the smallest units of self-sustaining life
  • Spontaneous origin of cells and vesicles
  • The last universal ancestor

• Cell structure – where you will explore the structure of the basic unit of life. This topic covers the following:
  • Cells as the basic structural unit of life
  • Microscopy
  • Prokaryotic and eukaryotic cells
  • Endosymbiosis (HL only)
  • Cell differentiation (HL only)

• Viruses (HL only) – where you'll explore tiny entities that blur the line between living and non-living. In this HL topic, you will learn about the following:
  • Virus structure
  • The lyctic and lysogenic cycle of a virus
  • Origins of viruses
  • Rapid evolution in viruses

• Diversity of organisms – where you'll explore the vast variety of living things. This topic focuses on the following:
  • The species concept
  • The binomial system
  • Speciation and divergence
  • Karyotyping and karyograms
  • Genomes
  • Dichotomous keys (HL only)

• Classification and cladistics (HL only) – where you'll study how organisms are classified and discover their evolutionary connections through shared characteristics. In this HL topic you will explore the following:
  • Classification of organisms
  • The taxa system and its limitations
  • Clades, cladistics, and cladograms

• Evolution and specification – where you'll examine the processes through which species evolve over time and the mechanisms that lead to the formation of new species. This topic focuses on the following:
  • The concept of evolution
  • Selective breeding
  • Homologous structures and analogous structures
  • Sympatric and allopatric speciation (HL only)
  • Adaptive radiation (HL only)
  • Hybridization and polyploidy (HL only)

• Conservation of biodiversity – where you'll investigate the issues of biodiversity and ecosystem loss. This topic focuses on the following:
  • Biodiversity and its loss
  • Anthropogenic species extinction
  • Ecosystem loss
  • Species conservation

Theme B: Form and function

In this theme, you will explore the following topics:

• Carbohydates and lipids – where you'll explore the structure and function of these essential biomolecules. In this topic you will learn about the following: 
  • The carbon atom – the basis of life
  • Macromolecules
  • Condensation and hydrolysis reactions
  • Monomers and polymers
  • The phospholipid bilayer

• Proteins – where you'll delve into the structure, function, and importance of proteins in biological processes. This topic focuses on the following:
  • Amino acids
  • Peptides, dipeptides, and polypeptides
  • Denaturation
  • Primary, secondary, tertiary, and quaternary structure of proteins (HL only)
  • Globular and fibrous proteins (HL only)

• Membranes and membrane transport – where you'll explore the composition of cell membranes and how substances move in and out of cells. This topic focuses on the following:
  • Simple diffusion and osmosis 
  • Medians of membrane transport
  • The fluid mosaic model 
  • Cholesterol and membrane fluidity (HL only)
  • Vesicle formation (HL only)
  • Indirect active transport (HL only)

• Organelles and compartmentalization – where you'll study the specialized structures within cells and how they are organized to carry out specific functions. In this topic you will explore the following:
  • Organelles and their functions
  • Compartmentalization 
  • The mitochondrion, chloroplast, nucleus, ribosomes, and the Golgi apparatus

• Cell specialization – where you'll investigate how cells differentiate and become specialized for various functions within organisms. In this topic you will learn about the following key concepts:
  • Differnetiation and specialization of cells
  • Stem cells
  • Cell size
  • Pneumocytes (HL only)
  • Sperm and egg cells (HL only)

• Gas exchange – where you'll examine how organisms exchange gases like oxygen and carbon dioxide with their environment. This topic focuses on the following:
  • Gas exchange surfaces 
  • Concentration gradients
  • Gas exchange in animals and leaves
  • Transpiration
  • Foetal and adult hemoglobin (HL only)
  • Bohr shift a cooperative binding (HL only)

• Transport – where you'll explore how organisms move essential substances such as nutrients and gases throughout their bodies. This topic focuses on the following:
  • Capillaries, veins, and arteries
  • Circulation in bony fish and mammals (HL only)
  • Stages of the cardiac cycle (HL only)
  • Xylem and phloem vessels (HL only)
  • Transpiration and translocation (HL only)

• Muscle and motility (HL only) – where you'll study the structure of muscles and how they enable movement in organisms. This topic focuses on the following:
  • Sliding filaments 
  • Titin
  • Antagonistic muscles 
  • Motor units in skeletal muscle 
  • Joints

• Adaptation to environment – where you'll learn how organisms adapt to survive and thrive in different environments. You will learn about the following:
  • Habitat
  • Species distribution 
  • Coral reef formation 
  • Terrestrial biome distribution

• Ecological niches – where you'll explore how species fit into ecosystems, including their roles, interactions, and habitats. This topic focuses on the following:
  • Role of species in an ecosystem
  • Anaerobes and aerobes 
  • Photosynthesis 
  • Holozoic, mixotrophic, and saprotrophic nutrition 
  • Omnivores, herbivores, and predators

Check out our free Biology IA exemplars

View all exemplars on Clastify

Grade received: 6

How do altering salicylic acid concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0%) affect the germination of Capsicum annuum longum seeds measuring the radicle length (mm) of the sprouts over 7 days?

Grade received: 7

What is the effect of Nickel (II) Chloride concentration on the germination rate (%) of Triticum aestivum seeds?

Grade received: 7

What is the optimal concentration of baking soda (NaHCO3) for the rate of photosynthesis in submerged spinach (Spinacia oleracea) leaves?

View hundreds of other Biology IA exemplars on Clastify

Click to view exemplars

Grade received: 6

Investigating the effect of coffee on the rate of protein digestion

Grade received: 7

What is the effect of increasing iron (III) chloride concentration (0 mg/L, 2mg/L, 4mg/L, 6mg/L, 8mg/L, 10mg/L) on the growth of duckweed (Lemna minor) in terms of change in number of leaves over 5 days?

Grade received: 7

How does the concentration of 50ml of ethanol solution (15%, 30%, 45%, 60%, 75%) influence the cell membrane permeability of beetroot, measured by the absorption transmission of light (Au) using a colorimeter, for 10 minutes?

Grade received: 7

How do different teas (chamomile, dandelion, nettle, black, and green tea) based on their potassium content used to water Vigna radiata seeds affect the success rate of germination over 96 hours, determined by successful germinations?

View hundreds of other Biology IA exemplars on Clastify

Click to view exemplars

Grade received: 7

What is the effect of different KCl percentage concentrations (0.0, 0.5, 1.0, 1.5, 2.0, 2.5) on the germination rate of Triticum Aestivum.

Grade received: 7

Investigation Regarding the Correlation Between HDI and Mortality Rates due to Stroke

Grade received: 6

Comparison of protein content in animal-based milk and plant-based milk (cow milk, goat milk, almond milk, soy milk, rice milk) by weighing mass of coagulated precipitate formed after adding a coagulant (vinegar)

Grade received: 6

How do altering salicylic acid concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0%) affect the germination of Capsicum annuum longum seeds measuring the radicle length (mm) of the sprouts over 7 days?

Grade received: 7

What is the effect of Nickel (II) Chloride concentration on the germination rate (%) of Triticum aestivum seeds?

Grade received: 7

What is the optimal concentration of baking soda (NaHCO3) for the rate of photosynthesis in submerged spinach (Spinacia oleracea) leaves?

View hundreds of other Biology IA exemplars on Clastify

Click to view exemplars

Grade received: 6

Investigating the effect of coffee on the rate of protein digestion

Grade received: 7

What is the effect of increasing iron (III) chloride concentration (0 mg/L, 2mg/L, 4mg/L, 6mg/L, 8mg/L, 10mg/L) on the growth of duckweed (Lemna minor) in terms of change in number of leaves over 5 days?

Grade received: 7

How does the concentration of 50ml of ethanol solution (15%, 30%, 45%, 60%, 75%) influence the cell membrane permeability of beetroot, measured by the absorption transmission of light (Au) using a colorimeter, for 10 minutes?

Grade received: 7

How do different teas (chamomile, dandelion, nettle, black, and green tea) based on their potassium content used to water Vigna radiata seeds affect the success rate of germination over 96 hours, determined by successful germinations?

View hundreds of other Biology IA exemplars on Clastify

Click to view exemplars

Grade received: 7

What is the effect of different KCl percentage concentrations (0.0, 0.5, 1.0, 1.5, 2.0, 2.5) on the germination rate of Triticum Aestivum.

Grade received: 7

Investigation Regarding the Correlation Between HDI and Mortality Rates due to Stroke

Grade received: 6

Comparison of protein content in animal-based milk and plant-based milk (cow milk, goat milk, almond milk, soy milk, rice milk) by weighing mass of coagulated precipitate formed after adding a coagulant (vinegar)

Grade received: 6

How do altering salicylic acid concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0%) affect the germination of Capsicum annuum longum seeds measuring the radicle length (mm) of the sprouts over 7 days?

Grade received: 7

What is the effect of Nickel (II) Chloride concentration on the germination rate (%) of Triticum aestivum seeds?

Grade received: 7

What is the optimal concentration of baking soda (NaHCO3) for the rate of photosynthesis in submerged spinach (Spinacia oleracea) leaves?

Theme C: Interaction and interdependence

In this theme, you will explore the following topics:

• Enzymes and metabolism – where you'll explore how enzymes catalyze biochemical reactions and the metabolic pathways that sustain life. This topic focuses on the following:
  • Metabolism
  • Enzymes
  • Anabolic and catabolic reactions
  • Allosteric sites and non-competitive inhibition (HL only)
  • Feedback inhibition (HL only)

• Cell respiration – where you'll investigate how cells break down glucose to produce energy in the form of ATP. This topic explores the following:
  • ATP and ADP
  • Anaerobic and aerobic respiration 
  • Glycolysis and the link reaction (HL only)
  • Krebs cycle (HL only)
  • Electron Transport chain (HL only)

• Photosynthesis – where you'll examine how plants and other organisms convert light energy into chemical energy through photosynthesis. This topic focuses on the following:
  • The photosynthesis reaction
  • Photosynthetic
  • Photolysis and chemiosmosis (HL only)
  • The Calvin cycle (HL only)
  • Light-dependent and light-independent reactions (HL only)

• Chemical signalling (HL only) – where you'll study how cells communicate with each other using chemical messengers like hormones. In this HL topic you will learn about the following:
  • Cell signalling 
  • Hormones, neurotransmitters, cytokines, and calcium ions
  • Adrenaline receptors
  • Positive and negative feedback

• Neutral signalling – where you'll explore how nerve cells transmit signals to coordinate bodily functions and responses. In this topic you will learn about the following:
  • Neurons
  • Resting and action potential 
  • Synapses
  • Oscilloscopes (HL only)
  • Inhibitory transmitters (HL only)
  • Consciousness (HL only)

• Integration of body systems – where you'll learn how various body systems work together to maintain homeostasis and overall function. This topic focuses on the following:
  • Coordination 
  • Cells, tissues, organs, and body systems
  • The brain, the spinal cord, and nerves
  • The endocrine system
  • Positive phototropism (HL only)
  • Auxins (HL only)

• Defence against disease – where you'll study how the immune system protects organisms from pathogens and disease. This topic focuses on the following:
  • Pathogens
  • Immunity
  • Phagocytes, lymphocytes, and antigens 
  • HIV and AIDS
  • Antibiotics
  • The COVID-19 pandemic

• Population and communities – where you'll explore how species interact within populations and communities, shaping ecosystems and biodiversity. This topic explores the following concepts:
  • Carrying capacity and competition for limited resources 
  • Population growth
  • Interspecific competition, mutualism, parasitism, and pathogenicity
  • Population control

• Transfers of energy and matter – where you'll investigate how energy and matter move through ecosystems, from producers to consumers and decomposers. This topic focuses on the following:
  • Sunlight as the primary energy source
  • Flow of energy, food chains, trophic levels, and energy pyramids
  • Autotrophs, photoautotrophs, and heterotrophs
  • Energy loss
  • The carbon cycle

Theme D: Continuity and change

• DNA replication – where you'll explore how cells accurately copy their DNA before division, ensuring genetic continuity. This topic focuses on the following:
  • DNA replication 
  • Polymerase chain reaction and gel electrophoresis
  • Leading and lagging strands (HL only)
  • Primase, polymerase l, polymerase lll, and ligase (HL only)

• Protein synthesis – where you'll study how the genetic code is translated into proteins, the building blocks of life. This topic explores the following:
  • Transcription and translation 
  • mRNA and tRNA
  • Mutations
  • Post-transcriptionla modification (HL only)
  • Proteasomes (HL only)

• Mutations and gene editing – where you'll investigate how changes in DNA can lead to mutations. This topic focuses on the following:
  • Base substitution, insertions, and deletions
  • Causes of mutation
  • Mutation and genetic variation
  • CRISPR sequences (HL only)

• Cell and nuclear division – where you'll learn about the processes of mitosis and meiosis, essential for growth, repair, and reproduction. This topic explores the following concepts:
  • Cytokinesis
  • Mitosis and meiosis
  • DNA replication 
  • Cell cycle (HL only)
  • Tumors (HL only)

• Gene expression (HL only) – where you'll examine how genes are turned on or off, controlling the production of proteins in response to environmental and internal signals. This topic focuses on the following:
  • Promoters, enhancers, and transcription factors
  • Degradation of mRNA
  • Epigenetic inheritance

• Water potential – where you'll explore the movement of water through cells and tissues. This topic focuses on the following concepts:
  • Osmosis
  • Medical applications of isotonic solutions
  • Water potential (HL only)
  • Contributions of solute potential and pressure potential to the water potential of cells with walls (HL only)

• Reproduction – where you'll study the various modes of reproduction, from sexual to asexual, from plant to animal. This topic focuses on the following:
  • Meiosis and gametes
  • Sexual reproduction in mammals
  • Reproductive systems
  • Sexual reproduction in plants

• Inheritance – where you'll investigate how traits are passed from one generation to the next through genetic material. In this topic you will explore the following:
  • Genetic crosses
  • Alleles
  • Continuous variation
  • Recombinants (HL only)

• Homeostasis – where you'll learn how organisms regulate internal conditions to maintain stability despite external changes. This topic focuses on the following:
  • Negative feedback loops
  • Hromones
  • Kidneys (HL only)

• Natural selection – where you'll explore how traits that enhance survival and reproduction become more common in populations over time. This topic focuses on the following:
  • Mutation and sexual reproduction 
  • Selection pressures and adaptation
  • Gene pool (HL only)
  • Artificial selection (HL only)

• Stability and change – where you'll study how ecosystems maintain balance and the factors that drive change within them. This topic explores the following:
  • Stability in ecosystems
  • Deforestation 
  • Keystone species
  • Sustainability 
  • Succession (HL only)

• Climate change – where you'll examine the causes and impacts of climate change on ecosystems and global biodiversity. This topic focuses on the following:
  • Causes of climate change
  • Global warming
  • Effects of global warming 
  • Phenology (HL only)
  • Evolution and climate change (HL only)

We hope you found this post helpful. For more useful materials associated with the IB check out the wide variety of IA, EE and TOK exemplars available at Clastify.