IB Biology Syllabus HL & SL

IB Biology Syllabus

Complete, up-to-date and broken down by sub-topics for the IB Biology SL and IB Biology HL courses!

IB Biology Syllabus HL & SL

Topic 1: Cell Biology

This section of the IB Biology syllabus explores the cells found within all living organisms. It builds the fundamental understanding required for later topics in the IB Biology syllabus.



1.1: Introduction to cells

(1) According to the cell theory, living organisms are composed of cells

(2) Organisms consisting of only one cell carry out all functions of life in that cell

(3) Surface area to volume ratio is important in the limitation of cell size

(4) Multicellular organisms have properties that emerge from the interaction of their cellular components

(5) Specialized tissues can develop by cell differentiation in multicellular organisms

(6) Differentiation involves the expression of some genes and not others in a cell’s genome

(7) The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development, and makes stem cells suitable for therapeutic uses

(1) Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae

(2) Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism

(3) Use of stem cells to treat Stargardt’s disease and one other named condition

(4) Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues

(5) Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs (Practical 1)

1.2: Ultrastructure of cells

(1) Prokaryotes have a simple cell structure without compartmentalization

(2) Eukaryotes have a compartmentalized cell structure

(3) Electron microscopes have a much higher resolution than light microscopes

(1) Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf

(2) Prokaryotes divide by binary fission

(3) Drawing of the ultrastructure of prokaryotic cells based on electron micrographs

(4) Drawing of the ultrastructure of eukaryotic cells based on electron micrographs

(5) Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells

1.3: Membrane structure

(1) Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules

(2) Membrane proteins are diverse in terms of structure, position in the membrane and function

(3) Cholesterol is a component of animal cell membranes

(1) Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes

(2) Drawing of the fluid mosaic model

(3) Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model

(4) Analysis of the falsification of the Davson- Danielli model that led to the Singer-Nicolson model

1.4: Membrane transport

(1) Particles move across membranes by simple diffusion, facilitated diffusion, osmosis, and active transport

(2) The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells

(1) Structure and function of sodium– potassium pumps for active transport and potassium channels for facilitated diffusion in axons

(2) Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis

(3) Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions (Practical 2)

1.5: The origin of cells

(1) Cells can only be formed by division of pre-existing cells

(2) The first cells must have arisen from non-living material

(3) The origin of eukaryotic cells can be explained by the endosymbiotic theory

(1) Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth

1.6: Cell division

(1) Mitosis is division of the nucleus into two genetically identical daughter nuclei

(2) Chromosomes condense by supercoiling during mitosis

(3) Cytokinesis occurs after mitosis and is different in plant and animal cells

(4) Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm

(5) Cyclins are involved in the control of the cell cycle

(6) Mutagens, oncogenes, and metastasis are involved in the development of primary and secondary tumours

(1) The correlation between smoking and incidence of cancers

(2) Identification of phases of mitosis in cells viewed with a microscope or in a micrograph

(3) Determination of a mitotic index from a micrograph

Topic 2: Molecular Biology

This section of the IB Biology syllabus explores the molecules and components found within cells. It links to the content covered in topic 1 of the IB Biology syllabus.



2.1: Molecules to metabolism

(1) Molecular biology explains living processes in terms of the chemical substances involved

(2) Carbon atoms can form four covalent bonds allowing a diversity of stable compounds to exist

(3) Life is based on carbon compounds including carbohydrates, lipids, proteins, and nucleic acids

(4) Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism

(5) Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions

(6) Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers

(1) Urea as an example of a compound that is produced by living organisms but can also be artificially synthesized

(2) Drawing molecular diagrams of glucose, ribose, a saturated fatty acid, and a generalized amino acid

(3) Identification of biochemicals such as sugars, lipids, or amino acids from molecular diagrams

2.2: Water

(1) Water molecules are polar and hydrogen bonds form between them

(2) Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water

(3) Substances can be hydrophilic or hydrophobic

(1) Comparison of the thermal properties of water with those of methane

(2) Use of water as a coolant in sweat

(3) Modes of transport of glucose, amino acids, cholesterol, fats, oxygen, and sodium chloride in blood in relation to their solubility in water

2.3: Carbohydrates and lipids

(1) Monosaccharide monomers are linked together by condensation reactions to form disaccharides and polysaccharide polymers

(2) Fatty acids can be saturated, monounsaturated, or polyunsaturated

(3) Unsaturated fatty acids can be cis or trans isomers

(4) Triglycerides are formed by condensation from three fatty acids and one glycerol

(1) Structure and function of cellulose and starch in plants and glycogen in humans

(2) Scientific evidence for health risks of trans fats and saturated fatty acids

(3) Lipids are more suitable for long-term energy storage in humans than carbohydrates

(4) Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids

(5) Use of molecular visualization software to compare cellulose, starch, and glycogen

(6) Determination of body mass index by calculation or use of a nomogram

2.4: Proteins

(1) Amino acids are linked together by condensation to form polypeptides

(2) There are 20 different amino acids in polypeptides synthesized on ribosomes

(3) Amino acids can be linked together in any sequence giving a huge range of possible

(4) The amino acid sequence of polypeptides is coded for by genes

(5) A protein may consist of a single polypeptide, or more than one polypeptide linked together

(6) The amino acid sequence determines the three-dimensional conformation of a protein

(7) Living organisms synthesize many different proteins with a wide range of functions

(8) Every individual has a unique proteome

(1) Rubisco, insulin, immunoglobulins, rhodopsin, collagen, and spider silk as examples of the range of protein functions

(2) Denaturation of proteins by heat or by deviation of pH from the optimum

(3) Drawing molecular diagrams to show the formation of a peptide bond

2.5: Enzymes

(1) Enzymes have an active site to which specific substrates bind

(2) Enzyme catalysis involves molecular motion and the collision of substrates with the active site

(3) Temperature, pH, and substrate concentration affect the rate of activity of enzymes

(4) Enzymes can be denatured

(5) Immobilized enzymes are widely used in industry

(1) Methods of production of lactose-free milk and its advantages

(2) Design of experiments to test the effect of temperature, pH, and substrate concentration on the activity of enzymes

(3) Experimental investigation of a factor affecting enzyme activity (Practical 3)

2.6: Structure of DNA and RNA

(1) The nucleic acids DNA and RNA are polymers of nucleotides

(2) DNA differs from RNA in the number of strands present, the base composition, and the type of pentose

(3) DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs

(1) Crick and Watson’s elucidation of the structure of DNA using model making

(2) Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons, and rectangles to represent phosphates, pentoses and bases

2.7: DNA replication, transcription and translation

(1) The replication of DNA is semi- conservative and depends on complementary base pairing

(2) Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds

(3) DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a template

(4) Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase

(5) Translation is the synthesis of polypeptides on ribosomes

(6) The amino acid sequence of polypeptides is determined by mRNA according to the genetic code

(7) Codons of three bases on mRNA correspond to one amino acid in a polypeptide

(8) Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA

(1) Use of Taq DNA polymerase to produce multiple copies of DNA rapidly by the polymerase chain reaction (PCR)

(2) Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species

(3) Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid

2.8: Respiration

(1) Cell respiration is the controlled release of energy from organic compounds to produce ATP

(2) ATP from cell respiration is immediately available as a source of energy in the cell

(3) Anaerobic cell respiration gives a small yield of ATP from glucose

(4) Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose

(1) Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking

(2) Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions

(3) Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer

2.9: Photosynthesis

(1) Photosynthesis is the production of carbon compounds in cells using light energy

(2) Visible light has a range of wavelengths with violet the shortest wavelength and red the longest

(3) Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours

(4) Oxygen is produced in photosynthesis from the photolysis of water

(5) Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide

(6) Temperature, light intensity, and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis

(1) Changes to the Earth’s atmosphere, oceans, and rock deposition due to photosynthesis

(2) Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis

(3) Design of experiments to investigate the effect of limiting factors on photosynthesis

(4) Separation of photosynthetic pigments by chromatograph (Practical 4)

Topic 3: Genetics

This section of the IB Biology syllabus focuses on the genetic information present within all living organisms. It provides understanding necessary for the later topics in the IB Biology syllabus.



3.1: Genes

(1) A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic

(2) A gene occupies a specific position on a chromosome

(3) The various specific forms of a gene are alleles

(4) Alleles differ from each other by one or only a few bases

(5) New alleles are formed by mutation.

(6) The genome is the whole of the genetic information of an organism

(7) The entire base sequence of human genes was sequenced in the Human Genome Project

(1) The causes of sickle cell anaemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in haemoglobin

(2) Comparison of the number of genes in humans with other species

(3) Use of a database to determine differences in the base sequence of a gene in two species

3.2: Chromosomes

(1) Prokaryotes have one chromosome consisting of a circular DNA molecule

(2) Some prokaryotes also have plasmids, but eukaryotes do not

(3) Eukaryote chromosomes are linear DNA molecules associated with histone proteins

(4) In a eukaryote species there are different chromosomes that carry different genes

(5) Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes

(6) Diploid nuclei have pairs of homologous chromosomes

(7) Haploid nuclei have one chromosome of each pair

(8) The number of chromosomes is a characteristic feature of members of a species

(9) A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length

(10) Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex

(1) Cairns’ technique for measuring the length of DNA molecules by autoradiography

(2) Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens and Paris japonica

(3) Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum

(4) Use of karyograms to deduce sex and diagnose Down syndrome in humans

(5) Use of databases to identify the locus of a human gene and its polypeptide product

3.3: Meiosis

(1) One diploid nucleus divides by meiosis to produce four haploid nuclei

(2) The halving of the chromosome number allows a sexual life cycle with fusion of gametes

(3) DNA is replicated before meiosis so that all chromosomes consist of two sister chromatids

(4) The early stages of meiosis involve pairing of homologous chromosomes and crossing over followed by condensation

(5) Orientation of pairs of homologous chromosomes prior to separation is random

(6) Separation of pairs of homologous chromosomes in the first division of meiosis halves the chromosome number

(7) Crossing over and random orientation promotes genetic variation

(8) Fusion of gametes from different parents promotes genetic variation

(1) Non-disjunction can cause Down syndrome and other chromosome abnormalities

(2) Studies showing age of parents influences chances of non- disjunction

(3) Description of methods used to obtain cells for karyotype analysis e.g., chorionic villus sampling and amniocentesis and the associated risks

(4) Drawing diagrams to show the stages of meiosis resulting in the formation of four haploid cells

3.4: Inheritance

(1) Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed

(2) Gametes are haploid so contain only one allele of each gene

(3) The two alleles of each gene separate into different haploid daughter nuclei during meiosis

(4) Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles

(5) Dominant alleles mask the effects of recessive alleles, but co-dominant alleles have joint effects

(6) Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles

(7) Some genetic diseases are sex-linked. The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes

(8) Many genetic diseases have been identified in humans, but most are very rare

(9) Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer

(1) Inheritance of ABO blood groups

(2) Red-green colour blindness and haemophilia as examples of sex- linked inheritance

(3) Inheritance of cystic fibrosis and Huntington’s disease

(4) Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl

(5) Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses

(6) Comparison of predicted and actual outcomes of genetic crosses using real data

(7) Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases

3.5: Genetic modification and biotechnology

(1) Gel electrophoresis is used to separate proteins or fragments of DNA according to size

(2) PCR can be used to amplify small amounts of DNA

(3) DNA profiling involves comparison of DNA

(4) Genetic modification is carried out by gene transfer between species

(5) Clones are groups of genetically identical organisms, derived from a single original parent cell

(6) Many plant species and some animal species have natural methods of cloning

(7) Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells

(8) Methods have been developed for cloning adult animals using differentiated cells

(1) Use of DNA profiling in paternity and forensic investigations

(2) Gene transfer to bacteria using plasmids makes use of restriction endonucleases and DNA ligase

(3) Assessment of the potential risks and benefits associated with genetic modification of crops

(4) Production of cloned embryos produced by somatic-cell nuclear transfer

(5) Design of an experiment to assess one factor affecting the rooting of stem-cuttings

(6) Analysis of examples of DNA profiles

(7) Analysis of data on risks to monarch butterflies of Bt crops

Topic 4: Ecology

This section of the IB Biology syllabus discusses the organisms and their interaction with the natural environment that surrounds them. It covers terms used elsewhere in the IB Biology syllabus.



4.1: Species, communities and ecosystems

(1) Species are groups of organisms that can potentially interbreed to produce fertile offspring

(2) Members of a species may be reproductively isolated in separate populations

(3) Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods)

(4) Consumers are heterotrophs that feed on living organisms by ingestion

(5) Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion

(6) Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion

(7) A community is formed by populations of different species living together and interacting with each other

(8) A community forms an ecosystem by its interactions with the abiotic environment

(9) Autotrophs obtain inorganic nutrients from the abiotic environment

(10) The supply of inorganic nutrients is maintained by nutrient cycling

(11) Ecosystems have the potential to be sustainable over long periods of time

(1) Classifying species as autotrophs, consumers, detritivores, or saprotrophs from a knowledge of their mode of nutrition

(2) Setting up sealed mesocosms to try to establish sustainability (Practical 5)

(3) Testing for association between two species using the chi-squared test with data obtained by quadrat sampling

(4) Recognizing and interpreting statistical significance

4.2: Energy flow

(1) Most ecosystems rely on a supply of energy from sunlight

(2) Light energy is converted to chemical energy in carbon compounds by photosynthesis

(3) Chemical energy in carbon compounds flows through food chains by means of feeding

(4) Energy released from carbon compounds by respiration is used in living organisms and converted to heat

(5) Living organisms cannot convert heat to other forms of energy

(6) Heat is lost from ecosystems

(7) Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

(1) Quantitative representations of energy flow using pyramids of energy

4.3: Carbon cycling

(1) Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds

(2) In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions

(3) Carbon dioxide diffuses from the atmosphere or water into autotrophs

(4) Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere

(5) Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground

(6) Methane is oxidized to carbon dioxide and water in the atmosphere

(7) Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils

(8) Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks

(9) Carbon dioxide is produced by the combustion of biomass and fossilized organic matter

(10) Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone

(1) Estimation of carbon fluxes due to processes in the carbon cycle

(2) Analysis of data from air monitoring stations to explain annual fluctuations

(3) Construct a diagram of the carbon cycle

4.4: Climate change

(1) Carbon dioxide and water vapour are the most significant greenhouse gases

(2) Other gases including methane and nitrogen oxides have less impact

(3) The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere

(4) The warmed Earth emits longer wavelength radiation (heat)

(5) Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere

(6) Global temperatures and climate patterns are influenced by concentrations of greenhouse gases

(7) There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures

(8) Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter

(1) Threats to coral reefs from increasing concentrations of dissolved carbon dioxide

(2) Correlations between global temperatures and carbon dioxide concentrations on Earth

(3) Evaluating claims that human activities are not causing climate change

Topic 5: Evolution & Biodiversity

This section of the IB Biology syllabus discusses the existence and emergence of life on planet earth. The content covered is unique to this topic of the IB Biology syllabus.



5.1: Evidence for evolution

(1) Evolution occurs when heritable characteristics of a species change

(2) The fossil record provides evidence for evolution

(3) Selective breeding of domesticated animals shows that artificial selection can cause evolution

(4) Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function

(5) Populations of a species can gradually diverge into separate species by evolution

(6) Continuous variation across the geographical range of related populations matches the concept of gradual divergence

(1) Development of melanistic insects in polluted areas

(2) Comparison of the pentadactyl limb of mammals, birds, amphibians, and reptiles with different methods of locomotion

5.2: Natural selection

(1) Natural selection can only occur if there is variation among members of the same species

(2) Mutation, meiosis, and sexual reproduction cause variation between individuals in a species

(3) Adaptations are characteristics that make an individual suited to its environment and way of life

(4) Species tend to produce more offspring than the environment can support

(5) Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring

(6) Individuals that reproduce pass on characteristics to their offspring

(7) Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species

(1) Changes in beaks of finches on Daphne Major

(2) Evolution of antibiotic resistance in bacteria

5.3: Classification of biodiversity

(1) The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses

(2) When species are discovered, they are given scientific names using the binomial system

(3) Taxonomists classify species using a hierarchy of taxa

(4) All organisms are classified into three domains

(5) The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus, and species

(6) In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species

(7) Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species

(8) Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group

(1) Classification of one plant and one animal species from domain to species level

(2) Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta

(3) Recognition features of porifera, cnidaria, platylhelmintha, annelida, mollusca, arthropoda and chordata

(4) Recognition of features of birds, mammals, amphibians, reptiles, and fish

(5) Construction of dichotomous keys for use in identifying specimens

5.4: Cladistics

(1) A clade is a group of organisms that have evolved from a common ancestor

(2) Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein

(3) Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor

(4) Traits can be analogous or homologous

(5) Cladograms are tree diagrams that show the most probable sequence of divergence in clades

(6) Evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species

(1) Cladograms including humans and other primates

(2) Reclassification of the figwort family using evidence from cladistics

(3) Analysis of cladograms to deduce evolutionary relationships

Topic 6: Human Physiology

This section of the IB Biology syllabus explores the physiological processes ocurring within humans. The content covered builds on the fundamentals established by earlier topics of the IB Biology syllabus.



6.1: Digestion and absorption

(1) The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut

(2) The pancreas secretes enzymes into the lumen of the small intestine

(3) Enzymes digest most macromolecules in food into monomers in the small intestine

(4) Villi increase the surface area of epithelium over which absorption is carried out

(5) Villi absorb monomers formed by digestion as well as mineral ions and vitamins

(6) Different methods of membrane transport are required to absorb different nutrients

(1) Processes occurring in the small intestine that result in the digestion of starch and transport of the products of digestion to the liver

(2) Use of dialysis tubing to model absorption of digested food in the intestine

(3) Production of an annotated diagram of the digestive system

(4) Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph

6.2: The blood system

(1) Arteries convey blood at high pressure from the ventricles to the tissues of the body

(2) Arteries have muscle cells and elastic fibres in their walls

(3) The muscle and elastic fibres assist in maintaining blood pressure between pump cycles

(4) Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary

(5) Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart

(6) Valves in veins and the heart ensure circulation of blood by preventing backflow

(7) There is a separate circulation for the lungs

(8) The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node

(9) The sinoatrial node acts as a pacemaker

(10) The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles

(11) The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain

(12) Epinephrine increases the heart rate to prepare for vigorous physical activity

(1) William Harvey’s discovery of the circulation of the blood with the heart acting as the pump

(2) Pressure changes in the left atrium, left ventricle, and aorta during the cardiac cycle

(3) Causes and consequences of occlusion of the coronary arteries

(4) Identification of blood vessels as arteries, capillaries, or veins from the structure of their walls

(5) Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure

6.3: Defence against infectious disease

(1) The skin and mucous membranes form a primary defence against pathogens that cause infectious disease

(2) Cuts in the skin are sealed by blood clotting

(3) Clotting factors are released from platelets

(4) The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin

(5) Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases

(6) Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity

(7) Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells

(8) Viruses lack a metabolism and cannot therefore be treated with antibiotics. Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance

(1) Causes and consequences of blood clot formation in coronary arteries

(2) Florey and Chain’s experiments to test penicillin on bacterial infections in mice

(3) Effects of HIV on the immune system and methods of transmission

6.4: Gas exchange

(1) Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

(2) Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange

(3) Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension

(4) Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles

(5) Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them

(6) Different muscles are required for inspiration and expiration because muscles only do work when they contract

(1) Causes and consequences of lung cancer

(2) Causes and consequences of emphysema

(3) External and internal intercostal muscles, and diaphragm and abdominal muscles as examples of antagonistic muscle action

(4) Monitoring of ventilation in humans at rest and after mild and vigorous exercise (Practical 6)

6.5: Neurones and synapses

(1) Neurons transmit electrical impulses

(2) The myelination of nerve fibres allows for saltatory conduction

(3) Neurons pump sodium and potassium ions across their membranes to generate a resting potential

(4) An action potential consists of depolarization and repolarization of the neuron

(5) Nerve impulses are action potentials propagated along the axons of neurons

(6) Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential

(7) Synapses are junctions between neurons and between neurons and receptor or effector cells

(8) When presynaptic neurons are depolarized they release a neurotransmitter into the synapse

(9) A nerve impulse is only initiated if the threshold potential is reached

(1) Secretion and reabsorption of acetylcholine by neurons at synapses

(2) Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides to acetylcholine receptors

(3) Analysis of oscilloscope traces showing resting potentials and action potentials

6.6: Hormones, homeostasis and reproduction

(1) Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration

(2) Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature

(3) Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite

(4) Melatonin is secreted by the pineal gland to control circadian rhythms

(5) A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone

(6) Testosterone causes pre-natal development of male genitalia and both sperm production and development of male secondary sexual characteristics during puberty

(7) Estrogen and progesterone cause pre-natal development of female reproductive organs and female secondary sexual characteristics during puberty

(8) The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and pituitary hormones

(1) Causes and treatment of Type I and Type II diabetes

(2) Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease

(3) Causes of jet lag and use of melatonin to alleviate it

(4) The use in IVF of drugs to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce superovulation and establish a pregnancy

(5) William Harvey’s investigation of sexual reproduction in deer

(6) Annotate diagrams of the male and female reproductive system to show names of structures and their functions

Topic 7: Nucleic Acids (HL)

This section of the IB Biology syllabus explores the processes of DNA handling in great depth. It builds on the material included earlier in topic 2 of the IB Biology syllabus.



7.1: DNA structure and replication (Higher Level)

(1) Nucleosomes help to supercoil the DNA

(2) DNA structure suggested a mechanism for DNA replication

(3) DNA polymerases can only add nucleotides to the 3’ end of a primer

(4) DNA replication is continuous on the leading strand and discontinuous on the lagging strand

(5) DNA replication is carried out by a complex system of enzymes

(6) Some regions of DNA do not code for proteins but have other important functions

(1) Rosalind Franklin’s and Maurice Wilkins’ investigation of DNA structure by X-ray diffraction

(2) Use of nucleotides containing dideoxyribonucleic acid to stop DNA replication in preparation of samples for base sequencing

(3) Tandem repeats are used in DNA profiling

(4) Analysis of results of the Hershey and Chase experiment providing evidence that DNA is the genetic material

(5) Utilization of molecular visualization software to analyse the association between protein and DNA within a nucleosome

7.2: Transcription and gene expression (Higher Level)

(1) Transcription occurs in a 5’ to 3’ direction

(2) Nucleosomes help to regulate transcription in eukaryotes

(3) Eukaryotic cells modify mRNA after transcription

(4) Splicing of mRNA increases the number of different proteins an organism can produce

(5) Gene expression is regulated by proteins that bind to specific base sequences in DNA

(6) The environment of a cell and of an organism has an impact on gene expression

(1) The promoter as an example of non- coding DNA with a function

(2) Analysis of changes in the DNA methylation patterns

7.3: Translation (Higher Level)

(1) Initiation of translation involves assembly of the components that carry out the process

(2) Synthesis of the polypeptide involves a repeated cycle of events

(3) Disassembly of the components follows termination of translation

(4) Free ribosomes synthesize proteins for use primarily within the cell

(5) Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes

(6) Translation can occur immediately after transcription in prokaryotes due to the absence of a nuclear membrane

(7) The sequence and number of amino acids in the polypeptide is the primary structure

(8) The secondary structure is the formation of alpha helices and beta pleated sheets stabilized by hydrogen bonding

(9) The tertiary structure is the further folding of the polypeptide stabilized by interactions between R groups

(10) The quaternary structure exists in proteins with more than one polypeptide chain

(1) tRNA-activating enzymes illustrate enzyme–substrate specificity and the role of phosphorylation

(2) Identification of polysomes in electron micrographs of prokaryotes and eukaryotes

(3) The use of molecular visualization software to analyse the structure of eukaryotic ribosomes and a tRNA molecule

Topic 8: Respiration & Photosynthesis (HL)

This section of the IB Biology syllabus explores the two major metabolic reactions that occur in living organisms. It builds on the material included earlier in topic 2 of the IB Biology syllabus.



8.1: Metabolism (Higher Level)

(1) Metabolic pathways consist of chains and cycles of enzyme-catalysed reactions

(2) Enzymes lower the activation energy of the chemical reactions that they catalyse

(3) Enzyme inhibitors can be competitive or non-competitive

(4) Metabolic pathways can be controlled by end-product inhibition

(1) End-product inhibition of the pathway that converts threonine to isoleucine

(2) Use of databases to identify potential new anti-malarial drugs

(3) Calculating and plotting rates of reaction from raw experimental results

(4) Distinguishing different types of inhibition from graphs at specified substrate concentration

8.2: Respiration (Higher Level)

(1) Cell respiration involves the oxidation and reduction of electron carriers

(2) Phosphorylation of molecules makes them less stable

(3) In glycolysis, glucose is converted to pyruvate in the cytoplasm

(4) Glycolysis gives a small net gain of ATP without the use of oxygen

(5) In aerobic cell respiration pyruvate is decarboxylated and oxidized and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction

(6) In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide

(7) Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD

(8) Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping

(9) In chemiosmosis protons diffuse through ATP synthase to generate ATP

(10) Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water

(11) The structure of the mitochondrion is adapted to the function it performs

(1) Electron tomography used to produce images of active mitochondria

(2) Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur

(3) Annotation of a diagram of a mitochondrion to indicate the adaptations to its function

8.3: Photosynthesis (Higher Level)

(1) Light-dependent reactions take place in the intermembrane space of the thylakoids

(2) Light-independent reactions take place in the stroma

(3) Reduced NADP and ATP are produced in the light-dependent reactions

(4) Absorption of light by photosystems generates excited electrons

(5) Photolysis of water generates electrons for use in the light-dependent reactions

(6) Transfer of excited electrons occurs between carriers in thylakoid membranes

(7) Excited electrons from Photosystem II are used to contribute to generate a proton gradient

(8) ATP synthase in thylakoids generates ATP using the proton gradient

(9) Excited electrons from Photosystem I are used to reduce NADP

(10) In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate

(11) Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP

(12) Triose phosphate is used to regenerate RuBP and produce carbohydrates

(13) Ribulose bisphosphate is reformed using ATP

(14) The structure of the chloroplast is adapted to its function in photosynthesis

(1) Calvin’s experiment to elucidate the carboxylation of RuBP

(2) Annotation of a diagram to indicate the adaptations of a chloroplast to its function

Topic 9: Plant Biology (HL)

This section of the IB Biology syllabus explores the structures, functions and processes of plants on earth. The material within this topic is not covered elsewhere on the IB Biology syllabus.



9.1: Transport in the xylem of plants (Higher Level)

(1) Transpiration is the inevitable consequence of gas exchange in the leaf

(2) Plants transport water from the roots to the leaves to replace losses from transpiration

(3) The cohesive property of water and the structure of the xylem vessels allow transport under tension

(4) The adhesive property of water and evaporation generate tension forces in leaf cell walls

(5) Active uptake of mineral ions in the roots causes absorption of water by osmosis

(1) Adaptations of plants in deserts and in saline soils for water conservation

(2) Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots, and capillary tubing

(3) Drawing the structure of primary xylem vessels in sections of stems based on microscope images

(4) Measurement of transpiration rates using potometers (Practical 7)

(5) Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates

9.2: Transport in the phloem of plants (Higher Level)

(1) Plants transport organic compounds from sources to sinks

(2) Incompressibility of water allows transport along hydrostatic pressure gradients

(3) Active transport is used to load organic compounds into phloem sieve tubes at the source

(4) High concentrations of solutes in the phloem at the source lead to water uptake by osmosis

(5) Raised hydrostatic pressure causes the contents of the phloem to flow towards sinks

(1) Structure–function relationships of phloem sieve tubes

(2) Identification of xylem and phloem in microscope images of stem and root

(3) Analysis of data from experiments measuring phloem transport rates using aphid stylets and radioactively labelled carbon dioxide

9.3: Growth in plants (Higher Level)

(1) Undifferentiated cells in the meristems of plants allow indeterminate growth

(2) Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves

(3) Plant hormones control growth in the shoot apex

(4) Plant shoots respond to the environment by tropisms

(5) Auxin efflux pumps can set up concentration gradients of auxin in plant tissue

(6) Auxin influences cell growth rates by changing the pattern of gene expression

(1) Micropropagation of plants using tissue from the shoot apex, nutrient agar gels and growth hormones

(2) Use of micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing varieties and propagation of orchids and other rare species

9.4: Reproduction in plants (Higher Level)

(1) Flowering involves a change in gene expression in the shoot apex

(2) The switch to flowering is a response to the length of light and dark periods in many plants

(3) Success in plant reproduction depends on pollination, fertilization, and seed dispersal

(4) Most flowering plants use mutualistic relationships with pollinators in sexual reproduction

(1) Methods used to induce short-day plants to flower out of season

(2) Drawing internal structure of seeds

(3) Drawing of half-views of animal-pollinated flowers

(4) Design of experiments to test hypotheses about factors affecting germination

Topic 10: Genetics & Evolution (HL)

This section of the IB Biology syllabus further details the processes associated with the genetic code during reproduction. It builds on the material included earlier in topic 3 of the IB Biology syllabus.



10.1: Meiosis (Higher Level)

(1) Chromosomes replicate in interphase before meiosis

(2) Crossing over is the exchange of DNA material between non-sister homologous chromatids

(3) Crossing over produces new combinations of alleles on the chromosomes of the haploid cells

(4) Chiasmata formation between non- sister chromatids can result in an exchange of alleles

(5) Homologous chromosomes separate in meiosis I

(6) Sister chromatids separate in meiosis II

(7) Independent assortment of genes is due to random orientation of pairs of homologous chromosomes in meiosis I

(1) Drawing diagrams to show chiasmata formed by crossing over

10.2: Inheritance (Higher Level)

(1) Gene loci are said to be linked if on the same chromosome

(2) Unlinked genes segregate independently as a result of meiosis

(3) Variation can be discrete or continuous

(4) The phenotypes of polygenic characteristics tend to show continuous variation

(5) Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant

(1) Morgan’s discovery of non-Mendelian ratios in Drosophila

(2) Completion and analysis of Punnett squares for dihybrid traits

(3) Polygenic traits such as human height may also be influenced by environmental factors

(4) Calculation of the predicted genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked autosomal genes

(5) Identification of recombinants in crosses involving two linked genes

(6) Use of a chi-squared test on data from dihybrid crosses

10.3: Gene pools and speciation (Higher Level)

(1) A gene pool consists of all the genes and their different alleles, present in an interbreeding population

(2) Evolution requires that allele frequencies change with time in populations

(3) Reproductive isolation of populations can be temporal, behavioural, or geographic

(4) Speciation due to divergence of isolated populations can be gradual

(5) Speciation can occur abruptly

(1) Identifying examples of directional, stabilizing, and disruptive selection

(2) Speciation in the genus Allium by polyploidy

(3) Comparison of allele frequencies of geographically isolated populations

Topic 11: Animal Physiology (HL)

This section of the IB Biology syllabus spans the physiological processes that occur in animals. It discusses linked but unique themes to earlier topics in the IB Biology syllabus.



11.1: Antibody production and vaccination (Higher Level)

(1) Every organism has unique molecules on the surface of its cells

(2) Pathogens can be species-specific although others can cross species barriers

(3) B lymphocytes are activated by T lymphocytes in mammals

(4) Activated B cells multiply to form clones of plasma cells and memory cells

(5) Plasma cells secrete antibodies

(6) Antibodies aid the destruction of pathogens

(7) White cells release histamine in response to allergens

(8) Histamines cause allergic symptoms

(9) Immunity depends upon the persistence of memory cells

(10) Vaccines contain antigens that trigger immunity but do not cause the disease

(11) Fusion of a tumour cell with an antibody-producing plasma cell creates a hybridoma cell

(12) Monoclonal antibodies are produced by hybridoma cells

(1) Smallpox was the first infectious disease of humans to have been eradicated by vaccination

(2) Monoclonal antibodies to HCG are used in pregnancy test kits

(3) Antigens on the surface of red blood cells stimulate antibody production in a person with a different blood group

(4) Analysis of epidemiological data related to vaccination programmes

11.2: Movement (Higher Level)

(1) Bones and exoskeletons provide anchorage for muscles and act as levers

(2) Synovial joints allow certain movements but not others

(3) Movement of the body requires muscles to work in antagonistic pairs

(4) Skeletal muscle fibres are multinucleate and contain specialized endoplasmic reticulum

(5) Muscle fibres contain many myofibrils

(6) Each myofibril is made up of contractile sarcomeres

(7) The contraction of the skeletal muscle is achieved by the sliding of actin and myosin filaments

(8) ATP hydrolysis and cross bridge formation are necessary for the filaments to slide

(9) Calcium ions and the proteins tropomyosin and troponin control muscle contractions

(1) Antagonistic pairs of muscles in an insect leg

(2) Annotation of a diagram of the human elbow

(3) Drawing labelled diagrams of the structure of a sarcomere

(4) Analysis of electron micrographs to find the state of contraction of muscle fibres

11.3: The kidney and osmoregulation (Higher Level)

(1) Animals are either osmoregulators or osmoconformers

(2) The Malpighian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes

(3) The composition of blood in the renal artery is different from that in the renal vein

(4) The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration

(5) The proximal convoluted tubule selectively reabsorbs useful substances by active transport

(6) The loop of Henle maintains hypertonic conditions in the medulla

(7) ADH controls reabsorption of water in the collecting duct

(8) The length of the loop of Henle is positively correlated with the need for water conservation in animals

(9) The type of nitrogenous waste in animals is correlated with evolutionary history and habitat

1) Consequences of dehydration and overhydration

(2) Treatment of kidney failure by haemodialysis or kidney transplant

(3) Blood cells, glucose, proteins, and drugs are detected in urinary tests

(4) Drawing and labelling a diagram of the human kidney

(5) Annotation of diagrams of the nephron

11.4: Sexual reproduction (Higher Level)

(1) Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation

(2) Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm

(3) Fertilization in animals can be internal or external

(4) Fertilization involves mechanisms that prevent polyspermy

(5) Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy

(6) HCG stimulates the ovary to secrete progesterone during early pregnancy

(7) The placenta facilitates the exchange of materials between the mother and fetus

(8) Estrogen and progesterone are secreted by the placenta once it has formed

(9) Birth is mediated by positive feedback involving estrogen and oxytocin

(1) The average 38-week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development of the young at birth for other mammals

(2) Annotation of diagrams of seminiferous tubule and ovary to show the stages of gametogenesis

(3) Annotation of diagrams of mature sperm and egg to indicate functions

Enjoyed our IB Biology question bank, topic notes, flashcards and useful resources?

Sign up to our mailing list to find out when we have released our next major Tiber Tutor update. Here's a sneak peak at what IB Biology and other IB science resources we have planned for our IB question bank:


IB Biology, IB Chemistry and IB Physics topic and sub-topic animated videos

IB Physics, IB Biology and IB Chemistry practice exams

Sign up