IBDP Biology SL
This AccelaStudy domain covers the complete IB Diploma Programme Biology Standard Level syllabus, preparing students for all three external examination papers and the Internal Assessment. The course is organized around six core topics — Cell Biology, Molecular Biology, Genetics, Ecology, Evolution and Biodiversity, and Human Physiology — and integrates the Nature of Science strand throughout.Cell Biology introduces the foundational principles of life at the cellular level, from the cell theory and ultrastructure of prokaryotic and eukaryotic cells to membrane dynamics and mitosis. Molecular Biology builds on this foundation by exploring the chemistry of life: the structure and function of carbohydrates, lipids, proteins, and nucleic acids; enzyme kinetics; DNA replication; transcription and translation; and an overview of cell respiration and photosynthesis. Genetics covers inheritance from the molecular level (genes and chromosomes) through to classical Mendelian patterns, sex-linked traits, meiosis, and the ethical dimensions of genetic technology. Ecology examines energy flow through ecosystems, biogeochemical cycles, population dynamics, and the pressing global challenge of biodiversity loss and climate change. Evolution and Biodiversity traces the evidence for evolution by natural selection, the mechanisms of speciation, and the principles of biological classification including cladistics. Human Physiology provides a systems-level understanding of digestion, circulation, immunity, gas exchange, neural signalling, and hormonal homeostasis.Experimental and quantitative skills are woven throughout every topic. Students learn to design investigations, collect and process data, apply statistical tests (t-test, chi-squared), construct and interpret graphs, and evaluate experimental methodology — skills assessed in Paper 3 Section A and in the Internal Assessment. The Internal Assessment component guides students through a self-directed scientific investigation, developing personal engagement, analytical rigour, and scientific communication.AccelaStudy's adaptive engine targets each of the four IB assessment objectives (AO1–AO4), using spaced repetition, contrastive question pairs, and worked data-based examples to build the depth of understanding required for a grade 6 or 7 at SL.
210
Minutes
80
Questions
4/7
Passing Score
$173
Exam Cost
Who Should Take This
This course is designed for IB Diploma students studying Biology at Standard Level — typically students in Years 12 and 13 (ages 16–18) who are interested in the life sciences but are not specializing in biology at Higher Level. It is equally valuable for students who want a strong scientific foundation to complement other Group 4 or Group 3 subjects, for those preparing for university programmes in medicine, environmental science, psychology, or health sciences, and for any student who wants to develop rigorous scientific thinking and data-analysis skills. No prior formal biology qualification is required beyond a solid middle-school science background.
What's Covered
1Cell theory, prokaryotic and eukaryotic cells, membrane structure, transport across membranes, cell division (mitosis)
2Molecules to metabolism, water, carbohydrates, lipids, proteins, enzymes, DNA structure and replication, transcription and translation, cell respiration, photosynthesis
3Genes, chromosomes, meiosis, inheritance (monohybrid, dihybrid, sex-linked), genetic modification and biotechnology
4Species, communities and ecosystems, energy flow, carbon cycling, climate change, population ecology
5Evidence for evolution, natural selection, classification of biodiversity, cladistics
6Digestion and absorption, the blood system, defence against infectious disease, gas exchange, neurons and synapses, hormones, homeostasis and reproduction
What's Included in AccelaStudy® AI
Adaptive Knowledge Graph
Practice Questions
Lesson Modules
Console Simulator Labs
Exam Tips & Strategy
13 Activity Formats
Course Outline
1Topic 1: Cell Biology 4 topics
1.1 Introduction to Cells
- State that all living organisms are composed of cells, and outline the cell theory including its three core principles and the exceptions such as skeletal muscle fibres and aseptate fungal hyphae.
- Distinguish between prokaryotic and eukaryotic cells by comparing their structural features, including the presence or absence of a nucleus, membrane-bound organelles, and cell wall composition.
- Construct and annotate biological drawings of prokaryotic and eukaryotic cells as seen under the electron microscope, applying correct biological drawing conventions including scale bars and labels.
1.2 Ultrastructure of Cells
- Identify and describe the functions of organelles found in eukaryotic cells, including the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, and vacuoles.
- Explain how the structure of organelles such as mitochondria and ribosomes is related to their specific functions, applying the principle of structure–function relationships in biology.
1.3 Membrane Structure
- Describe the fluid mosaic model of membrane structure, identifying the roles of phospholipids, cholesterol, glycoproteins, and integral and peripheral proteins in membrane function.
- Explain the processes of passive transport (diffusion, osmosis, facilitated diffusion) and active transport across membranes, distinguishing between them in terms of energy requirements and direction of movement.
1.4 Cell Division
- Outline the stages of mitosis (prophase, metaphase, anaphase, telophase) and describe the significance of mitosis for growth, repair, and asexual reproduction in eukaryotic organisms.
- Analyse data from experiments investigating the effect of environmental factors on the rate of cell division, including interpreting mitotic index calculations from micrograph data.
2Topic 2: Molecular Biology 5 topics
2.1 Molecules to Metabolism
- Identify the four main classes of biological molecules (carbohydrates, lipids, proteins, nucleic acids) and describe their monomers, polymers, and the condensation and hydrolysis reactions that interconvert them.
- Explain the metabolic roles of enzymes as biological catalysts, describing how enzyme structure (active site, substrate specificity) relates to function and how enzymes lower activation energy.
2.2 Water
- Describe the properties of water that are significant to living organisms, including cohesion, adhesion, high specific heat capacity, high latent heat of vaporization, and its role as a solvent and reactant.
2.3–2.5 Carbohydrates, Lipids, and Proteins
- Describe the structure and biological functions of monosaccharides, disaccharides, and polysaccharides, including glucose isomers, glycogen, starch, and cellulose, relating structure to function.
- Distinguish between saturated and unsaturated fatty acids and explain the structure and functions of triglycerides and phospholipids in energy storage and membrane formation respectively.
- Explain the four levels of protein structure (primary, secondary, tertiary, quaternary) and analyse how the sequence of amino acids determines the three-dimensional shape and function of a protein.
2.6–2.7 Enzymes and Cell Respiration
- Analyse experimental data on enzyme activity, explaining the effects of temperature, pH, substrate concentration, and inhibitor type (competitive and non-competitive) on reaction rate.
- Outline the stages of cell respiration including glycolysis in the cytoplasm and the link reaction and Krebs cycle in the mitochondria, identifying the net ATP yield from aerobic and anaerobic respiration.
2.8–2.9 Photosynthesis and DNA
- Outline the light-dependent and light-independent reactions of photosynthesis, identifying the roles of chlorophyll, ATP, NADPH, and the Calvin cycle in converting light energy to chemical energy.
- Describe the structure of DNA as a double helix, identifying the components of nucleotides, the antiparallel strands, complementary base pairing, and the role of hydrogen bonds in maintaining the structure.
- Explain the process of DNA replication, including the roles of helicase, DNA polymerase, and ligase, and justify why replication is described as semi-conservative using evidence from the Meselson–Stahl experiment.
3Topic 3: Genetics 3 topics
3.1 Genes
- Define the terms gene, allele, genome, genotype, phenotype, dominant, recessive, codominant, homozygous, and heterozygous, and apply these definitions accurately in genetic problem-solving contexts.
- Explain the relationship between genes and proteins, describing how the sequence of bases in a gene codes for the sequence of amino acids in a polypeptide via transcription and translation.
3.2 Chromosomes
- Describe the structure of chromosomes, distinguishing between diploid and haploid cells, homologous chromosomes, and sister chromatids, and identify the human karyotype including sex chromosomes.
- Outline the stages of meiosis I and meiosis II, explaining how independent assortment and crossing over during prophase I generate genetic variation in gametes.
3.3–3.4 Inheritance and Genetic Modification
- Construct Punnett squares and predict phenotypic and genotypic ratios for monohybrid and dihybrid crosses, including codominance, multiple alleles (ABO blood groups), and sex-linked traits.
- Evaluate the ethical implications of genetic screening, gene therapy, and genetically modified organisms, considering benefits and risks from multiple stakeholder perspectives.
4Topic 4: Ecology 4 topics
4.1 Species, Communities, and Ecosystems
- Define the ecological terms species, population, community, ecosystem, habitat, niche, and biome, and describe the biotic and abiotic components that characterize an ecosystem.
- Explain the flow of energy through ecosystems using food chains and food webs, distinguishing between producers, primary consumers, secondary consumers, and decomposers, and calculating energy transfer efficiency.
- Construct and interpret pyramids of energy, biomass, and numbers for given ecosystems, explaining why energy pyramids are always upright while biomass and number pyramids may be inverted.
4.2 Energy Flow
- Describe the carbon and nitrogen cycles, identifying the key processes (photosynthesis, respiration, decomposition, nitrification, denitrification, nitrogen fixation) and the organisms involved in each transformation.
4.3 Carbon Cycling and Climate Change
- Evaluate the impact of human activities on the carbon cycle and global climate, analysing data on atmospheric CO₂ concentrations and temperature trends to assess the evidence for anthropogenic climate change.
- Discuss the causes and consequences of loss of biodiversity, including habitat destruction, invasive species, overexploitation, and pollution, and evaluate conservation strategies at local and global scales.
4.4 Population Ecology
- Explain the factors that regulate population size, including carrying capacity, limiting factors, and the differences between J-shaped (exponential) and S-shaped (logistic) population growth curves.
- Analyse data from population studies, applying the Lincoln index formula to estimate population size from mark-recapture data and evaluating the assumptions and limitations of this method.
5Topic 5: Evolution and Biodiversity 4 topics
5.1 Evidence for Evolution
- Describe the evidence for evolution from the fossil record, comparative anatomy (homologous and analogous structures), molecular biology (DNA and protein sequences), and direct observation of natural selection.
- Explain the mechanism of natural selection, describing how variation, heritability, differential survival, and reproduction lead to changes in allele frequencies in populations over successive generations.
5.2 Natural Selection
- Evaluate the evidence for evolution by natural selection using specific examples such as antibiotic resistance in bacteria, industrial melanism in peppered moths, and the evolution of the horse, assessing the strength of each line of evidence.
- Explain the concept of speciation, distinguishing between allopatric and sympatric speciation and describing how reproductive isolation leads to the formation of new species over time.
5.3 Classification of Biodiversity
- Outline the binomial nomenclature system and the hierarchical classification of organisms into domain, kingdom, phylum, class, order, family, genus, and species, with examples from each domain.
- Distinguish between the key features of the five kingdoms (Prokaryotae, Protoctista, Fungi, Plantae, Animalia) and apply dichotomous keys to identify and classify unfamiliar organisms from their observable characteristics.
- Describe the distinguishing features of the major animal phyla (Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda, Echinodermata, Chordata) and the major plant divisions.
5.4 Cladistics
- Explain the principles of cladistics, describing how shared derived characteristics (synapomorphies) and molecular sequence data are used to construct cladograms that reflect evolutionary relationships.
6Topic 6: Human Physiology 5 topics
6.1 Digestion and Absorption
- Describe the structure and function of the human digestive system, identifying the roles of the mouth, oesophagus, stomach, small intestine, large intestine, liver, and pancreas in mechanical and chemical digestion.
- Explain the adaptations of the small intestine for absorption, including the roles of villi, microvilli, lacteals, and capillaries, and describe how different nutrients (glucose, amino acids, fatty acids) are absorbed.
6.2 The Blood System
- Describe the structure and function of the human heart, including the roles of the four chambers, valves, coronary arteries, and the cardiac conduction system in maintaining unidirectional blood flow.
- Distinguish between arteries, veins, and capillaries in terms of structure and function, and explain how the structure of each vessel type is adapted to its role in the circulatory system.
- Explain the transport of oxygen and carbon dioxide in the blood, describing the role of haemoglobin, the Bohr shift, and the conversion of CO₂ to bicarbonate ions in red blood cells.
6.3 Defence Against Infectious Disease
- Describe the non-specific and specific immune responses, including the roles of phagocytes, B lymphocytes, T lymphocytes, antibodies, and memory cells in defending the body against pathogens.
- Explain the principles of vaccination and the concept of herd immunity, and evaluate the ethical and social issues surrounding vaccination programmes using real-world examples.
6.4–6.5 Gas Exchange and Neurons
- Describe the structure of the human ventilation system and explain the mechanism of breathing, including the roles of the diaphragm, intercostal muscles, and the adaptations of alveoli for efficient gas exchange.
- Describe the structure and function of neurons, explaining how resting and action potentials are generated and propagated, and how synaptic transmission occurs including the role of neurotransmitters.
6.6 Hormones, Homeostasis, and Reproduction
- Explain the regulation of blood glucose concentration by insulin and glucagon, describing the roles of the pancreatic islets of Langerhans and the negative feedback mechanisms involved in homeostasis.
- Describe the hormonal control of the menstrual cycle, identifying the roles of FSH, LH, oestrogen, and progesterone, and explain how these hormones interact to regulate ovulation and the uterine lining.
7Experimental Skills and Nature of Science 3 topics
7.1 Experimental Design and Data Collection
- Construct a well-structured experimental design by identifying independent, dependent, and controlled variables, formulating a testable hypothesis, and selecting appropriate methods for data collection and safety considerations.
- Calculate mean, standard deviation, and standard error from biological data sets, and determine whether differences between data sets are statistically significant using the t-test and chi-squared test.
- Construct and interpret appropriate graphs (scatter plots, bar charts, histograms, line graphs) from biological data, applying correct conventions for axes, units, error bars, and lines of best fit.
7.2 Evaluation and Nature of Science
- Evaluate experimental methodology by identifying sources of systematic and random error, assessing the reliability and validity of data, and suggesting specific, realistic improvements to experimental design.
- Discuss the role of paradigm shifts, peer review, collaboration, and ethical guidelines in the development of biological knowledge, using historical examples such as the discovery of DNA structure or germ theory.
7.3 Internal Assessment
- Justify a focused, personally meaningful research question for the individual scientific investigation, demonstrating personal engagement with a biological topic and explaining its significance within the broader scientific context.
- Evaluate the conclusions of the individual scientific investigation against the research question and background theory, identifying limitations, suggesting extensions, and communicating findings clearly within the 1,500–2,250 word limit.
Scope
Included Topics
- All six SL core topics: Cell Biology, Molecular Biology, Genetics, Ecology, Evolution and Biodiversity, and Human Physiology — as specified in the IB Biology SL syllabus (first assessment 2016, updated 2023 edition)
- All required practicals and experimental skills: manipulating variables, recording and processing data, graphing, statistical analysis (mean, standard deviation, t-test, chi-squared), and evaluating experimental design
- Nature of Science (NOS) strand integrated across all topics: paradigm shifts, use of models, ethical implications of biological research, and the role of collaboration and communication in science
- Internal Assessment: individual scientific investigation (10 hours, 1,500–2,250 words) assessed on personal engagement, exploration, analysis, evaluation, and communication criteria
- Four assessment objectives (AO1 knowledge/understanding, AO2 application/analysis, AO3 synthesis/evaluation, AO4 experimental/quantitative skills) and IB command terms taxonomy
- Biological drawing conventions, microscopy skills, and use of scale bars
- Data-based questions involving graphs, tables, micrographs, and experimental results as tested in Paper 2
- Key biological concepts: structure and function, universality versus diversity, equilibrium within systems, and evolution as a unifying theme
Not Covered
- All HL-only topics: Nucleic Acids (Topic 7), Metabolism, Cell Respiration and Photosynthesis (Topic 8), Plant Biology (Topic 9), Genetics and Evolution (Topic 10), Animal Physiology (Topic 11)
- All HL-only Option topics beyond the SL portion
- Advanced biochemical pathway mechanisms beyond glycolysis overview and aerobic respiration summary
- Detailed pharmacology or clinical medicine beyond the scope of the SL Human Physiology topic
- University-level statistical methods beyond t-test and chi-squared as specified in the syllabus
Official Exam Page
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