IB Biology

Unity and Diversity

Form and Function

Interaction and Interdependence

Continuity and Change

Molecules

Cells

Organisms

Ecosystems

Molecules

Cells

Organisms

Ecosystems

Molecules

Cells

Organisms

Ecosystems

Molecules

Cells

Organisms

Ecosystems

Water

Nucleic Acids

Origin of Cells

Cell Structure

Viruses

Diversity of Organisms

Classification and Cladistics

Evolution and Speciation

Conservation of Biodiversity

Carbohydrates and Lipids

Proteins

Membranes and Membrane Transport

Organelles and Compartmentalization

Cell Specialization

Gas Exchange

Transport

Muscle and Motility

Adaptation to Environment

Ecological Niches

Enzymes and Metabolism

Cell Respiration

Photosynthesis

Chemical Signaling

Neural Signaling

Integration of Body Systems

Defense Against Disease

Populations and Communities

Transfers of Energy

DNA Replication

Protein Synthesis

Mutations and Gene Editing

Cell and Nuclear Division

Gene Expression

Water Potential

Reproduction

Inheritance

Homeostasis

Natural Selection

Stability and Change

Climate Change

Water as the medium for life

Hydrogen bonds as a consequence of the polar covalent bonds within water molecules

Cohesion of water molecules due to hydrogen bonding and consequences for organisms

Adhesion of water to materials that are polar or charged and impacts for organisms

Solvent properties of water linked to its role as a medium for metabolism and for transport in plants and animals

Physical properties of water and the consequences for animals in aquatic habitats

Extraplanetary origin of water on Earth and reasons for its retention

Relationship between the search for extraterrestrial life and the presence of water

DNA as the genetic material of all living organisms

Components of a nucleotide

Sugar–phosphate bonding and the sugar–phosphate “backbone” of DNA and RNA

Bases in each nucleic acid that form the basis of a code

RNA as a polymer formed by condensation of nucleotide monomers

DNA as a double helix made of two antiparallel strands of nucleotides with two strands linked by hydrogen bonding between complementary base pairs

Differences between DNA and RNA

Role of complementary base pairing in allowing genetic information to be replicated and expressed

Diversity of possible DNA base sequences and the limitless capacity of DNA for storing information

Conservation of the genetic code across all life forms as evidence of universal common ancestry

Directionality of RNA and DNA

Purine-to-pyrimidine bonding as a component of DNA helix stability

Structure of a nucleosome

Evidence from the Hershey–Chase experiment for DNA as the genetic material

Chargaff’s data on the relative amounts of pyrimidine and purine bases across diverse life forms

Conditions on early Earth and the pre-biotic formation of carbon compounds

Cells as the smallest units of self-sustaining life

Challenge of explaining the spontaneous origin of cells

Evidence for the origin of carbon compounds

Spontaneous formation of vesicles by coalescence of fatty acids into spherical bilayers

RNA as a presumed first genetic material

Evidence for a last universal common ancestor

Approaches used to estimate dates of the first living cells and the last universal common ancestor

Evidence for the evolution of the last universal common ancestor in the vicinity of hydrothermal vents

Cells as the basic structural unit of all living organisms

Microscopy skills

Developments in microscopy

Structures common to cells in all living organisms

Prokaryote cell structure

Eukaryote cell structure

Processes of life in unicellular organisms

Differences in eukaryotic cell structure between animals, fungi and plants

Atypical cell structure in eukaryotes

Cell types and cell structures viewed in light and electron micrographs

Drawing and annotation based on electron micrographs

Origin of eukaryotic cells by endosymbiosis

Cell differentiation as the process for developing specialized tissues in multicellular organisms

Evolution of multicellularity

Structural features common to viruses

Diversity of structure in viruses

Lytic cycle of a virus

Lysogenic cycle of a virus

Evidence for several origins of viruses from other organisms

Rapid evolution in viruses

Variation between organisms as a defining feature of life

Species as groups of organisms with shared traits

Binomial system for naming organisms

Biological species concept

Difficulties distinguishing between populations and species due to divergence of noninterbreeding populations during speciation

Diversity in chromosome numbers of plant and animal species

Karyotyping and karyograms

Unity and diversity of genomes within species

Diversity of eukaryote genomes

Comparison of genome sizes

Current and potential future uses of whole genome sequencing

Difficulties applying the biological species concept to asexually reproducing species and to bacteria that have horizontal gene transfer

Chromosome number as a shared trait within a species

Engagement with local plant or animal species to develop a dichotomous key

Identification of species from environmental DNA in a habitat using barcodes

Need for classification of organisms

Difficulties classifying organisms into the traditional hierarchy of taxa

Advantages of classification corresponding to evolutionary relationships

Clades as groups of organisms with common ancestry and shared characteristics

Gradual accumulation of sequence differences as the basis for estimates of when clades diverged from a common ancestor

Base sequences of genes or amino acid sequences of proteins as the basis for constructing cladograms

Analysing cladograms

Using cladistics to investigate whether the classification of groups corresponds to evolutionary relationships

Classification of all organisms into three domains using evidence from rRNA base sequences

Evolution as change in the heritable characteristics of a population

Evidence for evolution from base sequences in DNA or RNA and amino acid sequences in proteins

Evidence for evolution from selective breeding of domesticated animals and crop plants

Evidence for evolution from homologous structures

Convergent evolution as the origin of analogous structures

Speciation by splitting of pre-existing species

Roles of reproductive isolation and differential selection in speciation

Differences and similarities between sympatric and allopatric speciation

Adaptive radiation as a source of biodiversity

Barriers to hybridization and sterility of interspecific hybrids as mechanisms for of preventing the mixing of alleles between species

Abrupt speciation in plants by hybridization and polyploidy

Biodiversity as the variety of life in all its forms, levels and combinations

Comparisons between current number of species on Earth and past levels of biodiversity

Causes of anthropogenic species extinction

Causes of ecosystem loss

Evidence for a biodiversity crisis

Causes of the current biodiversity crisis

Need for several approaches to conservation of biodiversity

Selection of evolutionarily distinct and globally endangered species for conservation prioritization in the EDGE of Existence programme

Chemical properties of a carbon atom allowing for the formation of diverse compounds upon which life is based

Production of macromolecules by condensation reactions that link monomers to form a polymer

Digestion of polymers into monomers by hydrolysis reactions

Form and function of monosaccharides

Polysaccharides as energy storage compounds

Structure of cellulose related to its function as a structural polysaccharide in plants

Role of glycoproteins in cell–cell recognition

Hydrophobic properties of lipids

Formation of triglycerides and phospholipids by condensation reactions

Difference between saturated, monounsaturated and polyunsaturated fatty acids

Triglycerides in adipose tissues for energy storage and thermal insulation

Formation of phospholipid bilayers as a consequence of the hydrophobic and hydrophilic regions

Ability of non-polar steroids to pass through the phospholipid bilayer

Generalized structure of an amino acid

Condensation reactions forming dipeptides and longer chains of amino acids

Dietary requirements for amino acids

Infinite variety of possible peptide chains

Effect of pH and temperature on protein structure

Chemical diversity in the R-groups of amino acids as a basis for the immense diversity in protein form and function

Impact of primary structure on the conformation of proteins

Pleating and coiling of secondary structure of proteins

Dependence of tertiary structure on hydrogen bonds, ionic bonds, disulfide covalent bonds and hydrophobic interactions

Effect of polar and non-polar amino acids on tertiary structure of proteins

Quaternary structure of non-conjugated and conjugated proteins

Relationship of form and function in globular and fibrous proteins

Lipid bilayers as the basis of cell membranes

Lipid bilayers as barriers

Simple diffusion across membranes

Integral and peripheral proteins in membranes

Movement of water molecules across membranes by osmosis and the role of aquaporins

Channel proteins for facilitated diffusion

Pump proteins for active transport

Selectivity in membrane permeability

Structure and function of glycoproteins and glycolipids

Fluid mosaic model of membrane structure

Relationships between fatty acid composition of lipid bilayers and their fluidity

Cholesterol and membrane fluidity in animal cells

Membrane fluidity and the fusion and formation of vesicles

Gated ion channels in neurons

Sodium–potassium pumps as an example of exchange transporters

Sodium-dependent glucose cotransporters as an example of indirect active transport

Adhesion of cells to form tissues

Organelles as discrete subunits of cells that are adapted to perform specific functions

Advantage of the separation of the nucleus and cytoplasm into separate compartments

Advantages of compartmentalization in the cytoplasm of cells

Adaptations of the mitochondrion for production of ATP by aerobic cell respiration

Adaptations of the chloroplast for photosynthesis

Functional benefits of the double membrane of the nucleus

Structure and function of free ribosomes and of the rough endoplasmic reticulum

Structure and function of the Golgi apparatus

Structure and function of vesicles in cells

Production of unspecialized cells following fertilization and their development into specialized cells by differentiation

Properties of stem cells

Location and function of stem cell niches in adult humans

Differences between totipotent, pluripotent and multipotent stem cells

Cell size as an aspect of specialization

Surface area-to-volume ratios and constraints on cell size

Adaptations to increase surface area-to-volume ratios of cells

Adaptations of type I and type II pneumocytes in alveoli

Adaptations of cardiac muscle cells and striated muscle fibres

Adaptations of sperm and egg cells

Gas exchange as a vital function in all organisms

Properties of gas-exchange surfaces

Maintenance of concentration gradients at exchange surfaces in animals

Adaptations of mammalian lungs for gas exchange

Ventilation of the lungs

Measurement of lung volumes

Adaptations for gas exchange in leaves

Distribution of tissues in a leaf

Transpiration as a consequence of gas exchange in a leaf

Stomatal density

Adaptations of foetal and adult haemoglobin for the transport of oxygen

Bohr shift

Oxygen dissociation curves as a means of representing the affinity of haemoglobin for oxygen at different oxygen concentrations

Adaptations of capillaries for exchange of materials between blood and the internal or external environment

Structure of arteries and veins

Adaptations of arteries for the transport of blood away from the heart

Measurement of pulse rates

Adaptations of veins for the return of blood to the heart

Causes and consequences of occlusion of the coronary arteries

Transport of water from roots to leaves during transpiration

Adaptations of xylem vessels for transport of water

Distribution of tissues in a transverse section of the stem of a dicotyledonous plant

Distribution of tissues in a transverse section of the root of a dicotyledonous plant

Release and reuptake of tissue fluid in capillaries

Exchange of substances between tissue fluid and cells in tissues

Drainage of excess tissue fluid into lymph ducts

Differences between the single circulation of bony fish and the double circulation of mammals

Adaptations of the mammalian heart for delivering pressurized blood to the arteries

Stages in the cardiac cycle

Generation of root pressure in xylem vessels by active transport of mineral ions

Adaptations of phloem sieve tubes and companion cells for translocation of sap

Adaptations for movement as a universal feature of living organisms

Sliding filament model of muscle contraction

Role of the protein titin and antagonistic muscles in muscle relaxation

Structure and function of motor units in skeletal muscle

Roles of skeletons as anchorage for muscles and as levers

Movement at a synovial joint

Range of motion of a joint

Internal and external intercostal muscles as an example of antagonistic muscle action to facilitate internal body movements

Reasons for locomotion

Adaptations for swimming in marine mammals

Habitat as the place in which a community, species, population or organism lives

Adaptations of organisms to the abiotic environment of their habitat

Abiotic variables affecting species distribution

Range of tolerance of a limiting factor

Conditions required for coral reef formation

Abiotic factors as the determinants of terrestrial biome distribution

Biomes as groups of ecosystems with similar communities due to similar abiotic conditions and convergent evolution

Adaptations to life in hot deserts and tropical rainforest

Ecological niche as the role of a species in an ecosystem

Differences between organisms that are obligate anaerobes, facultative anaerobes and obligate aerobes

Photosynthesis as the mode of nutrition in plants, algae and several groups of photosynthetic prokaryotes

Holozoic nutrition in animals

Mixotrophic nutrition in some protists

Saprotrophic nutrition in some fungi and bacteria

Diversity of nutrition in archaea

Relationship between dentition and the diet of omnivorous and herbivorous representative members of the family Hominidae

Adaptations of herbivores for feeding on plants and of plants for resisting herbivory

Adaptations of predators for finding, catching and killing prey and of prey animals for resisting predation

Adaptations of plant form for harvesting light

Fundamental and realized niches

Competitive exclusion and the uniqueness of ecological niches

Enzymes as catalysts

Role of enzymes in metabolism

Anabolic and catabolic reactions

Enzymes as globular proteins with an active site for catalysis

Interactions between substrate and active site to allow induced-fit binding

Role of molecular motion and substrate-active site collisions in enzyme catalysis

Relationships between the structure of the active site, enzyme–substrate specificity and denaturation

Effects of temperature, pH and substrate concentration on the rate of enzyme activity

Measurements in enzyme-catalysed reactions

Effect of enzymes on activation energy

Intracellular and extracellular enzyme-catalysed reactions

Generation of heat energy by the reactions of metabolism

Cyclical and linear pathways in metabolism

Allosteric sites and non-competitive inhibition

Competitive inhibition as a consequence of an inhibitor binding reversibly to an active site

Regulation of metabolic pathways by feedback inhibition

Mechanism-based inhibition as a consequence of chemical changes to the active site caused by the irreversible binding of an inhibitor

ATP as the molecule that distributes energy within cells

Life processes within cells that ATP supplies with energy

Energy transfers during interconversions between ATP and ADP

Cell respiration as a system for producing ATP within the cell using energy released from carbon compounds

Differences between anaerobic and aerobic cell respiration in humans

Variables affecting the rate of cell respiration

Role of NAD as a carrier of hydrogen and oxidation by removal of hydrogen during cell respiration

Conversion of glucose to pyruvate by stepwise reactions in glycolysis with a net yield of ATP and reduced NAD

Conversion of pyruvate to lactate as a means of regenerating NAD in anaerobic cell respiration

Anaerobic cell respiration in yeast and its use in brewing and baking

Oxidation and decarboxylation of pyruvate as a link reaction in aerobic cell respiration

Oxidation and decarboxylation of acetyl groups in the Krebs cycle with a yield of ATP and reduced NAD

Transfer of energy by reduced NAD to the electron transport chain in the mitochondrion

Generation of a proton gradient by flow of electrons along the electron transport chain

Chemiosmosis and the synthesis of ATP in the mitochondrion

Role of oxygen as terminal electron acceptor in aerobic cell respiration

Differences between lipids and carbohydrates as respiratory substrates

Transformation of light energy to chemical energy when carbon compounds are produced in photosynthesis

Conversion of carbon dioxide to glucose in photosynthesis using hydrogen obtained by splitting water

Oxygen as a by-product of photosynthesis in plants, algae and cyanobacteria

Separation and identification of photosynthetic pigments by chromatography

Absorption of specific wavelengths of light by photosynthetic pigments

Similarities and differences of absorption and action spectra

Techniques for varying concentrations of carbon dioxide, light intensity or temperature experimentally to investigate the effects of limiting factors on the rate of photosynthesis

Carbon dioxide enrichment experiments as a means of predicting future rates of photosynthesis and plant growth

Photosystems as arrays of pigment molecules that can generate and emit excited electrons

Advantages of the structured array of different types of pigment molecules in a photosystem

Generation of oxygen by the photolysis of water in photosystem II

ATP production by chemiosmosis in thylakoids

Reduction of NADP by photosystem I

Thylakoids as systems for performing the light-dependent reactions of photosynthesis

Carbon fixation by Rubisco

Synthesis of triose phosphate using reduced NADP and ATP

Regeneration of RuBP in the Calvin cycle using ATP

Synthesis of carbohydrates, amino acids and other carbon compounds using the products of the Calvin cycle and mineral nutrients

Interdependence of the light-dependent and light-independent reactions

Receptors as proteins with binding sites for specific signalling chemicals

Cell signalling by bacteria in quorum sensing

Hormones, neurotransmitters, cytokines and calcium ions as examples of functional categories of signalling chemicals in animals

Chemical diversity of hormones and neurotransmitters

Localized and distant effects of signalling molecules

Differences between transmembrane receptors in a plasma membrane and intracellular receptors in the cytoplasm or nucleus

Initiation of signal transduction pathways by receptors

Transmembrane receptors for neurotransmitters and changes to membrane potential

Transmembrane receptors that activate G proteins

Mechanism of action of epinephrine (adrenaline) receptors

Transmembrane receptors with tyrosine kinase activity

Intracellular receptors that affect gene expression

Effects of the hormones oestradiol and progesterone on target cells

Regulation of cell signalling pathways by positive and negative feedback

Neurons as cells within the nervous system that carry electrical impulses

Generation of the resting potential by pumping to establish and maintain concentration gradients of sodium and potassium ions

Nerve impulses as action potentials that are propagated along nerve fibres

Variation in the speed of nerve impulses

Synapses as junctions between neurons and between neurons and effector cells

Release of neurotransmitters from a presynaptic membrane

Generation of an excitatory postsynaptic potential

Depolarization and repolarization during action potentials

Propagation of an action potential along a nerve fibre/axon as a result of local currents

Oscilloscope traces showing resting potentials and action potentials

Saltatory conduction in myelinated fibres to achieve faster impulses

Effects of exogenous chemicals on synaptic transmission

Inhibitory neurotransmitters and generation of inhibitory postsynaptic potentials

Summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron

Perception of pain by neurons with free nerve endings in the skin

Consciousness as a property that emerges from the interaction of individual neurons in the brain

System integration

Cells, tissues, organs and body systems as a hierarchy of subsystems that are integrated in a multicellular living organism

Integration of organs in animal bodies by hormonal and nervous signalling and by transport of materials and energy

The brain as a central information integration organ

The spinal cord as an integrating centre for unconscious processes

Input to the spinal cord and cerebral hemispheres through sensory neurons

Output from the cerebral hemispheres to muscles through motor neurons

Nerves as bundles of nerve fibres of both sensory and motor neurons

Pain reflex arcs as an example of involuntary responses with skeletal muscle as the effector

Role of the cerebellum in coordinating skeletal muscle contraction and balance

Modulation of sleep patterns by melatonin secretion as a part of circadian rhythms

Epinephrine (adrenaline) secretion by the adrenal glands to prepare the body for vigorous activity

Control of the endocrine system by the hypothalamus and pituitary gland

Feedback control of heart rate following sensory input from baroreceptors and chemoreceptors

Feedback control of ventilation rate following sensory input from chemoreceptors

Control of peristalsis in the digestive system by the central nervous system and enteric nervous system

Observations of tropic responses in seedlings

Positive phototropism as a directional growth response to lateral light in plant shoots

Phytohormones as signalling chemicals controlling growth, development and response to stimuli in plants

Auxin efflux carriers as an example of maintaining concentration gradients of phytohormones

Promotion of cell growth by auxin

Interactions between auxin and cytokinin as a means of regulating root and shoot growth

Positive feedback in fruit ripening and ethylene production

Pathogens as the cause of infectious diseases

Skin and mucous membranes as a primary defence

Sealing of cuts in skin by blood clotting

Differences between the innate immune system and the adaptive immune system

Infection control by phagocytes

Lymphocytes as cells in the adaptive immune system that cooperate to produce antibodies

Antigens as recognition molecules that trigger antibody production

Activation of B-lymphocytes by helper T-lymphocytes

Multiplication of activated B-lymphocytes to form clones of antibody-secreting plasma cells

Immunity as a consequence of retaining memory cells

Transmission of HIV in body fluids

Infection of lymphocytes by HIV with AIDS as a consequence

Antibiotics as chemicals that block processes occurring in bacteria but not in eukaryotic cells

Evolution of resistance to several antibiotics in strains of pathogenic bacteria

Zoonoses as infectious diseases that can transfer from other species to humans

Vaccines and immunization

Herd immunity and the prevention of epidemics

Evaluation of data related to the COVID-19 pandemic

Populations as interacting groups of organisms of the same species living in an area

Estimation of population size by random sampling

Random quadrat sampling to estimate population size for sessile organisms

Capture–mark–release–recapture and the Lincoln index to estimate population size for motile organisms

Carrying capacity and competition for limited resources

Negative feedback control of population size by density-dependent factors

Population growth curves

Modelling of the sigmoid population growth curve

Competition versus cooperation in intraspecific relationships

A community as all of the interacting organisms in an ecosystem

Herbivory, predation, interspecific competition, mutualism, parasitism and pathogenicity as categories of interspecific relationship within communities

Mutualism as an interspecific relationship that benefits both species

Resource competition between endemic and invasive species

Tests for interspecific competition

Use of the chi-squared test for association between two species

Predator–prey relationships as an example of density-dependent control of animal populations

Top-down and bottom-up control of populations in communities

Allelopathy and secretion of antibiotics

Ecosystems as open systems in which both energy and matter can enter and exit

Sunlight as the principal source of energy that sustains most ecosystems

Flow of chemical energy through food chains

Construction of food chains and food webs to represent feeding relationships in a community

Supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms

Autotrophs as organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances

Use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs

Heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require

Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration

Classification of organisms into trophic levels

Construction of energy pyramids

Reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels

Heat loss to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration

Restrictions on the number of trophic levels in ecosystems due to energy losses

Primary production as accumulation of carbon compounds in biomass by autotrophs

Secondary production as accumulation of carbon compounds in biomass by heterotrophs

Constructing carbon cycle diagrams

Ecosystems as carbon sinks and carbon sources

Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and natural gas

Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion

Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration

Recycling of all chemical elements required by living organisms in ecosystems

DNA replication as production of exact copies of DNA with identical base sequences

Semi-conservative nature of DNA replication and role of complementary base pairing

Role of helicase and DNA polymerase in DNA replication

Polymerase chain reaction and gel electrophoresis as tools for amplifying and separating DNA

Applications of polymerase chain reaction and gel electrophoresis

Directionality of DNA polymerases

Differences between replication on the leading strand and the lagging strand

Functions of DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication

DNA proofreading

Transcription as the synthesis of RNA using a DNA template

Role of hydrogen bonding and complementary base pairing in transcription

Stability of DNA templates

Transcription as a process required for the expression of genes

Translation as the synthesis of polypeptides from mRNA

Roles of mRNA, ribosomes and tRNA in translation

Complementary base pairing between tRNA and mRNA

Features of the genetic code

Using the genetic code expressed as a table of mRNA codons

Stepwise movement of the ribosome along mRNA and linkage of amino acids by peptide bonding to the growing polypeptide chain

Mutations that change protein structure

Directionality of transcription and translation

Initiation of transcription at the promoter

Non-coding sequences in DNA do not code for polypeptides

Post-transcriptional modification in eukaryotic cells

Alternative splicing of exons to produce variants of a protein from a single gene

Initiation of translation

Modification of polypeptides into their functional state

Recycling of amino acids by proteasomes

Gene mutations as structural changes to genes at the molecular level

Consequences of base substitutions

Consequences of insertions and deletions

Causes of gene mutation

Randomness in mutation

Consequences of mutation in germ cells and somatic cells

Mutation as a source of genetic variation

Gene knockout as a technique for investigating the function of a gene by changing it to make it inoperative

Use of the CRISPR sequences and the enzyme Cas9 in gene editing

Hypotheses to account for conserved or highly conserved sequences in genes

Generation of new cells in living organisms by cell division

Cytokinesis as splitting of cytoplasm in a parent cell between daughter cells

Equal and unequal cytokinesis

Roles of mitosis and meiosis in eukaryotes

DNA replication as a prerequisite for both mitosis and meiosis

Condensation and movement of chromosomes as shared features of mitosis and meiosis

Phases of mitosis

Identification of phases of mitosis

Meiosis as a reduction division

Down syndrome and non-disjunction

Meiosis as a source of variation

Cell proliferation for growth, cell replacement and tissue repair

Phases of the cell cycle

Cell growth during interphase

Control of the cell cycle using cyclins

Consequences of mutations in genes that control the cell cycle

Differences between tumours in rates of cell division and growth and in the capacity for metastasis and invasion of neighbouring tissue

Gene expression as the mechanism by which information in genes has effects on the phenotype

Regulation of transcription by proteins that bind to specific base sequences in DNA

Control of the degradation of mRNA as a means of regulating translation

Epigenesis as the development of patterns of differentiation in the cells of a multicellular organism

Differences between the genome, transcriptome and proteome of individual cells

Methylation of the promoter and histones in nucleosomes as examples of epigenetic tags

Epigenetic inheritance through heritable changes to gene expression

Examples of environmental effects on gene expression in cells and organisms

Consequences of removal of most but not all epigenetic tags from the ovum and sperm

Monozygotic twin studies

External factors impacting the pattern of gene expression

Solvation with water as the solvent

Water movement from less concentrated to more concentrated solutions

Water movement by osmosis into or out of cells

Changes due to water movement in plant tissue bathed in hypotonic and those bathed in hypertonic solutions

Effects of water movement on cells that lack a cell wall

Effects of water movement on cells with a cell wall

Medical applications of isotonic solutions

Water potential as the potential energy of water per unit volume

Movement of water from higher to lower water potential

Contributions of solute potential and pressure potential to the water potential of cells with walls

Water potential and water movements in plant tissue

Differences between sexual and asexual reproduction

Role of meiosis and fusion of gametes in the sexual life cycle

Differences between male and female sexes in sexual reproduction

Anatomy of the human male and female reproductive systems

Changes during the ovarian and uterine cycles and their hormonal regulation

Fertilization in humans

Use of hormones in in vitro fertilization (IVF) treatment

Sexual reproduction in flowering plants

Features of an insect-pollinated flower

Methods of promoting cross-pollination

Self-incompatibility mechanisms to increase genetic variation within a species

Dispersal and germination of seeds

Control of the developmental changes of puberty by gonadotropin-releasing hormone and steroid sex hormones

Spermatogenesis and oogenesis in humans

Mechanisms to prevent polyspermy

Development of a blastocyst and implantation in the endometrium

Pregnancy testing by detection of human chorionic gonadotropin secretion

Role of the placenta in foetal development inside the uterus

Hormonal control of pregnancy and childbirth

Hormone replacement therapy and the risk of coronary heart disease

Production of haploid gametes in parents and their fusion to form a diploid zygote as the means of inheritance

Methods for conducting genetic crosses in flowering plants

Genotype as the combination of alleles inherited by an organism

Phenotype as the observable traits of an organism resulting from genotype and environmental factors

Effects of dominant and recessive alleles on phenotype

Phenotypic plasticity as the capacity to develop traits suited to the environment experienced by an organism, by varying patterns of gene expression

Phenylketonuria as an example of a human disease due to a recessive allele

Single-nucleotide polymorphisms and multiple alleles in gene pools

ABO blood groups as an example of multiple alleles

Incomplete dominance and codominance

Sex determination in humans and inheritance of genes on sex chromosomes

Haemophilia as an example of a sex-linked genetic disorder

Pedigree charts to deduce patterns of inheritance of genetic disorders

Continuous variation due to polygenic inheritance and/or environmental factors

Box-and-whisker plots to represent data for a continuous variable such as student height

Segregation and independent assortment of unlinked genes in meiosis

Punnett grids for predicting genotypic and phenotypic ratios in dihybrid crosses involving pairs of unlinked autosomal genes

Loci of human genes and their polypeptide products

Autosomal gene linkage

Recombinants in crosses involving two linked or unlinked genes

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

Homeostasis as maintenance of the internal environment of an organism

Negative feedback loops in homeostasis

Regulation of blood glucose as an example of the role of hormones in homeostasis

Physiological changes that form the basis of type 1 and type 2 diabetes

Thermoregulation as an example of negative feedback control

Thermoregulation mechanisms in humans

Role of the kidney in osmoregulation and excretion

Role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion

Role of the loop of Henle

Osmoregulation by water reabsorption in the collecting ducts

Changes in blood supply to organs in response to changes in activity

Natural selection as the mechanism driving evolutionary change

Roles of mutation and sexual reproduction in generating the variation on which natural selection acts

Overproduction of offspring and competition for resources as factors that promote natural selection

Abiotic factors as selection pressures

Differences between individuals in adaptation, survival and reproduction as the basis for natural selection

Requirement that traits are heritable for evolutionary change to occur

Sexual selection as a selection pressure in animal species

Modelling of sexual and natural selection based on experimental control of selection pressures

Concept of the gene pool

Allele frequencies of geographically isolated populations

Changes in allele frequency in the gene pool as a consequence of natural selection between individuals according to differences in their heritable traits

Differences between directional, disruptive and stabilizing selection

Hardy–Weinberg equation and calculations of allele or genotype frequencies

Hardy–Weinberg conditions that must be maintained for a population to be in genetic equilibrium

Artificial selection by deliberate choice of traits

Stability as a property of natural ecosystems

Requirements for stability in ecosystems

Deforestation of Amazon rainforest as an example of a possible tipping point in ecosystem stability

Use of a model to investigate the effect of variables on ecosystem stability

Role of keystone species in the stability of ecosystems

Assessing sustainability of resource harvesting from natural ecosystems

Factors affecting the sustainability of agriculture

Eutrophication of aquatic and marine ecosystems due to leaching

Biomagnification of pollutants in natural ecosystems

Effects of microplastic and macroplastic pollution of the oceans

Restoration of natural processes in ecosystems by rewilding

Ecological succession and its causes

Changes occurring during primary succession

Cyclical succession in ecosystems

Climax communities and arrested succession

Anthropogenic causes of climate change

Positive feedback cycles in global warming

Change from net carbon accumulation to net loss in boreal forests as an example of a tipping point

Melting of landfast ice and sea ice as examples of polar habitat change

Changes in ocean currents altering the timing and extent of nutrient upwelling

Poleward and upslope range shifts of temperate species

Threats to coral reefs as an example of potential ecosystem collapse

Afforestation, forest regeneration and restoration of peat-forming wetlands as approaches to carbon sequestration

Phenology as research into the timing of biological events

Disruption to the synchrony of phenological events by climate change

Increases to the number of insect life cycles within a year due to climate change

Evolution as a consequence of climate change