IB Biology D - Continuity and Change

D1.1.1 DNA replication

D1.1.2 Semi-conservative nature of DNA replication

D1.1.3 Role of helicase and DNA polymerase in DNA replication

D1.1.4 Polymerase chain reaction and gel electrophoresis

D1.1.5 Applications of polymerase chain reaction and gel electrophoresis

D1.1.6 Directionality of DNA polymerases (HL)

D1.1.7 Differences between replication on the leading strand and the lagging strand (HL)

D1.1.8 DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication (HL)

D1.1.9 DNA proofreading (HL)

D1.2.1 Transcription as the synthesis of RNA using a DNA template

D1.2.2 Role of hydrogen bonding and complementary base pairing in transcription

D1.2.3 Stability of DNA templates

D1.2.4 Transcription as a process required for the expression of genes

D1.2.5 Translation as the synthesis of polypeptides from mRNA

D1.2.6 Roles of mRNA, ribosomes and tRNA in translation

D1.2.7 Complementary base pairing between tRNA and mRNA

D1.2.8 Features of the genetic code

D1.2.9 Using the genetic code expressed as a table of mRNA codons

D1.2.10 Stepwise movement of the ribosome along mRNA

D1.2.11 Mutations that change protein structure

D1.2.12 Directionality of transcription and translation (HL)

D1.2.13 Initiation of transcription at the promoter (HL)

D1.2.14 Non-coding sequences in DNA do not code for polypeptides (HL)

D1.2.15 Post-transcriptional modification in eukaryotic cells (HL)

D1.2.16 Alternative splicing of exons to produce variants of a protein from a single gene (HL)

D1.2.17 Initiation of translation (HL)

D1.2.18 Modification of polypeptides into their functional state (HL)

D1.2.19 Recycling of amino acids by proteasomes (HL)

D1.3.1 Gene mutations as structural changes to genes at the molecular level

D1.3.2 Consequences of base substitutions

D1.3.3 Consequences of insertions and deletions

D1.3.4 Causes of gene mutation

D1.3.5 Randomness in mutation

D1.3.6 Consequences of mutation in germ cells and somatic cells

D1.3.7 Mutation as a source of genetic variation

D1.3.8 Gene knockout (HL)

D1.3.9 Use of the CRISPR sequences and the enzyme Cas9 in gene editing (HL)

D1.3.10 Hypotheses to account for conserved or highly conserved sequences in genes (HL)

D2.1.1 Generation of new cells in living organisms by cell division

D2.1.2 Cytokinesis as splitting of cytoplasm in a parent cell between daughter cells

D2.1.3 Equal and unequal cytokinesis

D2.1.4 Roles of mitosis and meiosis in eukaryotes

D2.1.5 DNA replication as a prerequisite for both mitosis and meiosis

D2.1.6 Condensation and movement of chromosomes as shared features of mitosis and meiosis

D2.1.7 Phases of mitosis

D2.1.8 Identification of phases of mitosis

D2.1.9 Meiosis as a reduction division

D2.1.10 Down syndrome and non-disjunction

D2.1.11 Meiosis as a source of variation

D2.1.12 Cell proliferation for growth, cell replacement and tissue repair (HL)

D2.1.13 Phases of the cell cycle (HL)

D2.1.14 Cell growth during interphase (HL)

D2.1.15 Control of the cell cycle using cyclins (HL)

D2.1.16 Consequences of mutations in genes that control the cell cycle (HL)

D2.1.17 Differences between tumours (HL)

D2.2.1 Gene expression

D2.2.2 Regulation of transcription by proteins

D2.2.3 Control of the degradation of mRNA

D2.2.4 Epigenesis

D2.2.5 Differences between the genome, transcriptome and proteome of individual cells

D2.2.6 Methylation of the promoter and histones in nucleosomes as examples of epigenetic tags

D2.2.7 Epigenetic inheritance through heritable changes to gene expression

D2.2.8 Examples of environmental effects on gene expression in cells and organisms

D2.2.9 Consequences of removal of most but not all epigenetic tags from the ovum and sperm

D2.2.10 Monozygotic twin studies

D2.2.11 External factors impacting the pattern of gene expression

D2.3.1 Solvation with water as the solvent

D2.3.2 Water movement from less concentrated to more concentrated solutions

D2.3.3 Water movement by osmosis into or out of cells

D2.3.4 Changes due to water movement in plant tissue

D2.3.5 Effects of water movement on cells that lack a cell wall

D2.3.6 Effects of water movement on cells with a cell wall

D2.3.7 Medical applications of isotonic solutions

D2.3.8 Water potential as the potential energy of water per unit volume (HL)

D2.3.9 Movement of water from higher to lower water potential (HL)

D2.3.10 Contributions of solute potential and pressure potential to the water potential (HL)

D2.3.11 Water potential and water movements in plant tissue (HL)

D3.1.1 Differences between sexual and asexual reproduction

D3.1.2 Role of meiosis and fusion of gametes in the sexual life cycle

D3.1.3 Differences between male and female sexes in sexual reproduction

D3.1.4 Anatomy of the human male and female reproductive systems

D3.1.5 Changes during the ovarian and uterine cycles and their hormonal regulation

D3.1.6 Fertilization in humans

D3.1.7 Use of hormones in in vitro fertilization (IVF) treatment

D3.1.8 Sexual reproduction in flowering plants

D3.1.9 Features of an insect-pollinated flower

D3.1.10 Methods of promoting cross-pollination

D3.1.11 Self-incompatibility mechanisms to increase genetic variation within a species

D3.1.12 Dispersal and germination of seeds

D3.1.13 Control of the developmental changes of puberty (HL)

D3.1.14 Spermatogenesis and oogenesis in humans (HL)

D3.1.15 Mechanisms to prevent polyspermy (HL)

D3.1.16 Development of a blastocyst and implantation in the endometrium (HL)

D3.1.17 Pregnancy testing by detection of human chorionic gonadotropin secretion (HL)

D3.1.18 Role of the placenta in foetal development inside the uterus (HL)

D3.1.19 Hormonal control of pregnancy and childbirth (HL)

D3.1.20 Hormone replacement therapy and the risk of coronary heart disease (HL)

D3.2.1 Production of haploid gametes in parents

D3.2.2 Methods for conducting genetic crosses in flowering plants

D3.2.3 Genotype as the combination of alleles inherited by an organism

D3.2.4 Phenotype

D3.2.5 Effects of dominant and recessive alleles on phenotype

D3.2.6 Phenotypic plasticity

D3.2.7 Phenylketonuria

D3.2.8 Single-nucleotide polymorphisms and multiple alleles in gene pools

D3.2.9 ABO blood groups as an example of multiple alleles

D3.2.10 Incomplete dominance and codominance

D3.2.11 Sex determination in humans and inheritance of genes on sex chromosomes

D3.2.12 Haemophilia as an example of a sex-linked genetic disorder

D3.2.13 Pedigree charts to deduce patterns of inheritance of genetic disorders

D3.2.14 Continuous variation due to polygenic inheritance and/or environmental factors

D3.2.15 Box-and-whisker plots to represent data for a continuous variable such as student height

D3.2.16 Segregation and independent assortment of unlinked genes in meiosis (HL)

D3.2.17 Punnett grids for predicting genotypic and phenotypic ratios in dihybrid crosses (HL)

D3.2.18 Loci of human genes and their polypeptide products (HL)

D3.2.19 Autosomal gene linkage (HL)

D3.2.20 Recombinants in crosses involving two linked or unlinked genes (HL)

D3.2.21 Use of a chi-squared test on data from dihybrid crosses (HL)

D3.3.1 Homeostasis

D3.3.2 Negative feedback loops in homeostasis

D3.3.3 Regulation of blood glucose as an example of the role of hormones in homeostasis

D3.3.4 Physiological changes that form the basis of type 1 and type 2 diabetes

D3.3.5 Thermoregulation as an example of negative feedback control

D3.3.6 Thermoregulation mechanisms in humans

D3.3.7 Role of the kidney in osmoregulation and excretion (HL)

D3.3.8 Role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion (HL)

D3.3.9 Role of the loop of Henle (HL)

D3.3.10 Osmoregulation by water reabsorption in the collecting ducts (HL)

D3.3.11 Changes in blood supply to organs in response to changes in activity (HL)

D4.1.1 Natural selection as the mechanism driving evolutionary change

D4.1.2 Roles of mutation and sexual reproduction

D4.1.3 Overproduction of offspring and competition for resources

D4.1.4 Abiotic factors as selection pressures

D4.1.5 Differences between individuals in adaptation, survival and reproduction

D4.1.6 Requirement that traits are heritable for evolutionary change to occur

D4.1.7 Sexual selection as a selection pressure in animal species

D4.1.8 Modelling of sexual and natural selection

D4.1.9 Concept of the gene pool (HL)

D4.1.10 Allele frequencies of geographically isolated populations (HL)

D4.1.11 Changes in allele frequency in the gene pool (HL)

D4.1.12 Differences between directional, disruptive and stabilizing selection (HL)

D4.1.13 Hardy–Weinberg equation and calculations of allele or genotype frequencies (HL)

D4.1.14 Hardy–Weinberg conditions (HL)

D4.1.15 Artificial selection by deliberate choice of traits (HL)

D4.2.1 Stability as a property of natural ecosystems

D4.2.2 Requirements for stability in ecosystems

D4.2.3 Deforestation of Amazon rainforest

D4.2.4 Use of a model to investigate the effect of variables on ecosystem stability

D4.2.5 Role of keystone species in the stability of ecosystems

D4.2.6 Assessing sustainability of resource harvesting from natural ecosystems

D4.2.7 Factors affecting the sustainability of agriculture

D4.2.8 Eutrophication of aquatic and marine ecosystems due to leaching

D4.2.9 Biomagnification of pollutants in natural ecosystems

D4.2.10 Effects of microplastic and macroplastic pollution of the oceans

D4.2.11 Restoration of natural processes in ecosystems by rewilding

D4.2.12 Ecological succession and its causes (HL)

D4.2.13 Changes occurring during primary succession (HL)

D4.2.14 Cyclical succession in ecosystems (HL)

D4.2.15 Climax communities and arrested succession (HL)

D4.3.1 Anthropogenic causes of climate change

D4.3.2 Positive feedback cycles in global warming

D4.3.3 Change from net carbon accumulation to net loss in boreal forests

D4.3.4 Melting of landfast ice and sea ice as examples of polar habitat change

D4.3.5 Changes in ocean currents altering the timing and extent of nutrient upwelling

D4.3.6 Poleward and upslope range shifts of temperate species

D4.3.7 Threats to coral reefs as an example of potential ecosystem collapse

D4.3.8 Afforestation, forest regeneration and restoration of peat-forming wetlands

D4.3.9 Phenology as research into the timing of biological events (HL)

D4.3.10 Disruption to the synchrony of phenological events by climate change (HL)

D4.3.11 Increases to the number of insect life cycles within a year due to climate change (HL)

D4.3.12 Evolution as a consequence of climate change (HL)