IB Biology Syllabus Checklist

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1: Molecules & Metabolism 2: Cells & Signalling 3: Organisms 4: Ecosystems

1 - Molecules & Metabolism

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Master IB Biology Topic 1: Molecules & Metabolism. Access comprehensive study notes on the foundational molecules of life, including water, nucleic acids, carbohydrates, lipids, and proteins. Dive deep into essential biological processes such as enzyme catalysis, cellular respiration, photosynthesis, DNA replication, protein synthesis, and genetic mutations for both SL and HL.

Subtopic

Understanding

A1.1: Water

The first cells originated in water and water remains the medium in which most processes of life occur.

The polarity of covalent bonding within water molecules is due to unequal sharing of electrons, and hydrogen bonding due to this polarity occurs between water molecules. Represent two or more water molecules with hydrogen bonds between them (showing polarity).

The cohesion of water molecules due to hydrogen bonding and the associated benefits for organisms.

Ahesion of water to materials that are polar or charged, and the impacts this has on organisms.

A1.1: Origin of water (HL)

The significance of water in evolution and the hypotheses for it's origin, including: asteroids, gravity and temperature changes.

The relationship between the search for extraterrestrial life and the presence of water, including the idea of the “Goldilocks zone”.

A1.2: Nucleic acids

DNA is the genetic material of all living organisms, but some viruses use RNA as their genetic material.

Draw diagrams of nucleotides using circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases.

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

The names and purpose of the nitrogenous bases.

Understand that RNA is a polymer formed by condensation of nucleotide monomers, and be able to draw and recognize diagrams of the structure of single nucleotides and RNA polymers.

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

Recall the differences between DNA and RNA, including displaying them visually.

The role of complementary base pairing in allowing genetic information to be replicated and expressed.

Explain the diversity of possible DNA base sequences and the limitless capacity of DNA for storing information.

10:

Understand that conservation of the genetic code across all life forms as evidence of universal common ancestry.

A1.2: Further nucleic acids (HL)

Recall the directionality of RNA and DNA.

Recall how purine-to-pyrimidine bonding contributes to DNA helix stability.

Recall the structure of a nucleosome.

Understand the evidence provided from the Hershey–Chase experiment for DNA as the source of genetic material.

Understand how the “problem of induction” is addressed by the “certainty of falsification” through Chargaff’s data on the relative amounts of pyrimidine and purine bases across diverse life forms.

B1.1: Carbohydrates and lipids

Understand the nature of a covalent bond, the diversity of carbon compounds, and examples of molecules with branched or unbranched chains and single or multiple rings.

The production of macromolecules by condensation reactions, includnig examples of polysaccharides, polypeptides and nucleic acids.

The digestion of polymers into monomers by hydrolysis reactions.

Recall the form and function of monosaccharides, including: pentoses, hexoses, and glucose.

Understand polysaccharides as energy storage compounds, including: starch in plants and glycogen in animals.

The structure of cellulose is related to its function as a structural polysaccharide in plants.

Explain the role of glycoproteins in cell–cell recognition, including ABO antigens as an example.

Recall the hydrophobic properties of lipids

Recall the formation of triglycerides and phospholipids by condensation reactions.

10:

State the difference between saturated, monounsaturated and polyunsaturated fatty acids.

11:

Understand the role of triglycerides in adipose tissues for energy storage and thermal insulation.

12:

Describe the formation of phospholipid bilayers as a consequence of the hydrophobic and hydrophilic regions. Use of the term “amphipathic”.

13:

Recall the ability of non-polar steroids to pass through the phospholipid bilayer, including oestradiol and testosterone as examples.

B1.2: Proteins

Describe and draw the generalized structure of an amino acid, including the alpha carbon atom with amine group, carboxyl group, R-group and hydrogen attached.

State and draw condensation reactions forming dipeptides and longer chains of amino acids.

State the dietary requirements for amino acids.

Understand the infinite variety of possible peptide chains and examples of polypeptides.

Explain the effect of pH and temperature on protein structure, including use of the term “denaturation”.

B1.2: Further proteins (HL)

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

Explain the impact of primary structure on the conformation of proteins.

Describe the pleating and coiling involved in the secondary structure of proteins.

Recall the dependence of tertiary structure on hydrogen bonds, ionic bonds, disulfide covalent bonds and hydrophobic interactions. Recall that pairs of cysteines form disulfide bonds.

Explain the effect of polar and non-polar amino acids on the tertiary structure of proteins.

Explain the quaternary structure of non-conjugated and conjugated proteins, including insulin, collagen, and haemoglobin.

Recall the relationship of form and function in globular and fibrous proteins, using insulin and collagen to exemplify how form and function are related.

C1.1: Enzymes & metabolism

Understand the role of enzymes as catalysts.

Understand the role of enzymes in metabolism.

Recall anabolic and catabolic reactions as the formation of macromolecules from monomers during protein synthesis, glycogen formation and photosynthesis, and the hydrolysis of macromolecules into monomers during digestion and respiration.

Explain the structure and function of the active site.

Explain the interactions that occur between substrates and active sites to allow induced-fit binding.

Recall the role of molecular motion and substrate-active site collisions in enzyme catalysis.

Explain the relationships between the structure of the active site, enzyme–substrate specificity and denaturation.

Explain the rffects of temperature, pH and substrate concentration on the rate of enzyme activity.

Record and interpret measurements in enzyme-catalysed reactions.

10:

Explain the rffect of enzymes on activation energy, including the analysis of related graphs.

C1.1: Further metabolism (HL)

Recall intracellular and extracellular enzyme-catalysed reactions, including: glycolysis, the Krebs cycle, and chemical digestion in the gut.

Understand the generation of heat energy by the reactions of metabolism.

Recall examples of cyclical and linear pathways in metabolism, including: glycolysis, the Krebs cycle and the Calvin cycle.

Understand the allosteric sites and process of non-competitive inhibition.

Understand competitive inhibition, using statins as an example, and contrast this process to non-competitive inhibition.

Understand the regulation of metabolic pathways by feedback inhibition, using isoleucine as an example of end-product inhibition.

Recall penicillin as an example of mechanism-based inhibition caused by the irreversible binding of an inhibitor.

C1.2: Respiration

Name ATP as the molecule that distributes energy within cells.

Recall the life processes within cells that ATP supplies with energy, including: active transport, anabolism, and movement.

Recall and compare the energy transfers during interconversions between ATP and ADP.

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

Explain the differences between anaerobic and aerobic cell respiration in humans, including: respiratory substrates, oxygen requirement, yields of ATP, waste products, and reaction location. Write equations for both processes.

Recall the variables affecting the rate of cell respiration.

C1.2: Further respiration (HL)

Explain the role of NAD as a carrier of hydrogen during cell respiration.

Recall the stepwise conversion of glucose to pyruvate during glycolysis with a net yield of ATP and reduced NAD. Specific names of intermediates are not required.

Recall the conversion of pyruvate to lactate as a means of regenerating NAD in anaerobic cell respiration.

Understand anaerobic cell respiration in yeast and its use in brewing and baking.

Recall the oxidation and decarboxylation of pyruvate as a link reaction in aerobic cell respiration.

Recall the oxidation and decarboxylation of acetyl groups in the Krebs cycle with a yield of ATP and reduced NAD, including naming the intermediates citrate (6C) and oxaloacetate (4C).

Explain the transfer of energy by reduced NAD to the electron transport chain in the mitochondrion.

Understand the generation of a proton gradient by flow of electrons along the electron transport chain (ETC).

Recall chemiosmosis and the synthesis of ATP in the mitochondrion.

10:

Recall the role of oxygen as terminal electron acceptor in aerobic cell respiration.

11:

State the differences between lipids and carbohydrates as respiratory substrates, including: the yield of energy per gram, and the presence of glycolysis and anaerobic respiration.

C1.3: Photosynthesis

Understand the transformation of light energy to chemical energy when carbon compounds are produced in photosynthesis.

Recall the word and symbol equation for the conversion of carbon dioxide to glucose in photosynthesis using hydrogen obtained by splitting water.

Recall oxygen as a by-product of photosynthesis in plants, algae and cyanobacteria due to the splitting of water.

Describe the separation and identification of photosynthetic pigments by chromatography.

Explain the absorption of specific wavelengths of light by photosynthetic pigments, including: excitation of electrons, transformation of energy, and the reason that only some wavelengths are absorbed. Interpret absorption spectra.

Recall similarities and differences between absorption and action spectra.

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

Recall carbon dioxide enrichment experiments as a means of predicting future rates of photosynthesis and plant growth.

C1.3: Further photosynthesis (HL)

Recall the generation of oxygen by the photolysis of water in photosystem II.

Describe the advantages of the structured array of different types of pigment molecules in a photosystem.

Understand photosystems as arrays of pigment molecules that can generate and emit excited electrons.

Recall ATP production by chemiosmosis in thylakoids, including: the proton gradient, ATP synthase, and proton pumping by the chain of electron carriers.

Recall the reduction of NADP by photosystem I, using the terms “NADP and reduced NADP” or “NADP⁺ and NADPH”.

Appreciate thylakoids as systems for performing the light-dependent reactions of photosynthesis.

Explain carbon fixation by Rubisco, including use of the terms RuBP, CO₂,and glycerate 3-phosphate.

Recall the synthesis of triose phosphate using reduced NADP and ATP.

Understand the regeneration of RuBP in the Calvin cycle using ATP.

10:

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

11:

Explain the interdependence of the light-dependent and light-independent reactions.

D1.1: DNA replication

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

Explain the semi-conservative nature of DNA replication and role of complementary base pairing.

Explain the role of helicase and DNA polymerase in DNA replication.

Explain the polymerase chain reaction and gel electrophoresis as tools for amplifying and separating DNA.

Describe the applications of the polymerase chain reaction and gel electrophoresis, including DNA profiling for paternity and forensic investigations.

D1.1: Further DNA replication (HL)

Describe the rirectionality of DNA polymerases.

Explain the differences between replication on the leading strand and the lagging strand, including use of the terms “continuous”, “discontinuous”, and “Okazaki fragments”.

Recall the functions of DNA primase, DNA polymerase I, DNA polymerase III and DNA ligase in replication.

Understand DNA proofreading.

D1.2: Protein synthesis

Define transcription as the synthesis of RNA using a DNA template.

Describe the role of hydrogen bonding and complementary base pairing in transcription, including the pairing of adenine and uracil.

Explain the stability of DNA templates.

Understand transcription as a process required for the expression of genes.

Define translation as the synthesis of polypeptides from mRNA.

Recall the roles of mRNA, ribosomes and tRNA in translation.

Recall complementary base pairing between tRNA and mRNA, including use of the terms “codon” and “anticodon”.

Describe the features of the genetic code, including use of the terms “degeneracy” and “universality”.

Deduce the sequence of amino acids coded by an mRNA strand.

10:

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

11:

Recall mutations that change protein structure, including an an example of a point mutation affecting protein structure.

Explain the initiation of translation, including the attachment of the small subunit, movement to the start codon, tRNA, and attachment of the large subunit. Understand the binding sites for tRNA (A, P and E).

D1.2: Further protein synthesis (HL)

Recall the directionality of transcription and translation.

Describe the initiation of transcription at the promoter.

Understand that non-coding sequences in DNA do not code for polypeptides, including examples to regulators of gene expression, introns, telomeres and genes for rRNAs and tRNAs in eukaryotes.

Explain post-transcriptional modification in eukaryotic cells, including the removal of introns and splicing together of exons to form mature mRNA and also the addition of 5' caps and 3' polyA tails to stabilize mRNA transcripts.

Describe alternative splicing of exons to produce variants of a protein from a single gene.

Understand the modification of polypeptides into their functional state including the example of the two stage transformation of pre-proinsulin to insulin.

Describe the recycling of amino acids by proteasomes.

D1.3: Mutations

Define gene mutations as structural changes to genes at the molecular level. Distinguish between substitutions, insertions and deletions.

Describe the consequences of base substitutions, including single-nucleotide polymorphisms (SNPs).

Describe the consequences of insertions and deletions.

Describe the causes of gene mutation.

Understand the randomness of mutation.

Outline the consequences of mutation in germ cells and somatic cells, including inheritance of mutated genes and cancer.

Understand mutation as a source of genetic variation.

D1.3: Gene editing (HL)

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

Explain the use of the CRISPR sequences and the enzyme Cas9 in gene editing, including an example of the successful use of this technology.

Understand hypotheses to account for conserved or highly conserved sequences in genes.

2 - Cells & Signalling

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Ace IB Biology Topic 2: Cells & Signalling. Discover the structural and functional units of life with detailed materials on cell origins, eukaryotic and prokaryotic structures, and viruses. Master complex concepts like lipid bilayers, membrane transport, organelle compartmentalisation, stem cell specialisation, neural and chemical signalling, and gene expression.

Subtopic

Understanding

A2.1: Origins of cells (HL)

Recall the conditions on early Earth and the pre-biotic formation of carbon compounds.

Recall that cells as the smallest units of self-sustaining life, and discuss the differences between something that is living and something that is non-living.

Explaining the spontaneous origin of cells, including: catalysis, self-replication of molecules, self-assembly and the emergence of compartmentalization as necessary requirements.

Evidence for the origin of carbon compounds and the Miller–Urey experiment.

Understand the spontaneous formation of vesicles by coalescence of fatty acids into spherical bilayers.

Explain why RNA is a presumed first genetic material.

Recall the evidence for a last universal common ancestor (LUCA), including: the universal genetic code and shared genes across all organisms.

The approaches used to estimate dates of the first living cells and the last universal common ancestor.

Recall the evidence for the evolution of the last universal common ancestor in the vicinity of hydrothermal vents.

A2.2: Cell structure

Cells are the basic structural unit of all living organisms.

Microscopy skills, including: making mounts, staining, using an eyepiece graticule, focusing, calculating actual size and magnification, producing a scale bar, and taking photographs.

Recall developments in microscopy, including: electron microscopy, freeze fracture, cryogenic electron microscopy, and the use of fluorescent stains.

State structures common to cells in all living organisms.

Recall Prokaryote cell structure, including: cell wall, plasma membrane, cytoplasm, naked DNA in a loop and 70S ribosomes.

Recall Eukaryote cell structure, including: plasma membrane, cytoplasm, 80S ribosomes; a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, microtubules and microfilaments.

Recall the processes of life in unicellular organisms: homeostasis, metabolism, nutrition, movement, excretion, growth, response to stimuli, and reproduction.

Provide differences in eukaryotic cell structure between animals, fungi and plant.

Recall an example of atypical cell structure in eukaryotes.

10:

Identify cell types and cell structures viewed in light and electron micrographs.

11:

Draw and annotate based on electron micrographs, including: nucleus, mitochondria, chloroplasts, sap vacuole, Golgi apparatus, rough and smooth endoplasmic reticulum, chromosomes, cell wall, plasma membrane, secretory vesicles, and microvilli.

A2.2: Further cell structure (HL)

Explain the origin of eukaryotic cells by endosymbiosis, including the relevant evidence.

Recall cell differentiation as the process for developing specialized tissues in multicellular organisms.

Recall the evolution of multicellularity and its advantages.

A2.3: Viruses (HL)

Recall the structural features common to viruses, including: size, nucleic acid, a capsid, no cytoplasm, and few or no enzymes.

Understand the diversity of structure in viruses.

Explain the lytic cycle of a virus using bacteriophage lambda as an example.

The Lysogenic cycle of bacteriophage lambda.

Recall the evidence for several origins of viruses from other organisms.

Explain the rapid evolution in viruses using two examples: evolution of influenza viruses and HIV.

B2.1: Membranes and transport

Recall lipid bilayers as the basis of cell membranes.

Understand lipid bilayers as barriers since hydrophobic hydrocarbon chains that form the core of a membrane have low permeability to large molecules and hydrophilic particles.

Recall simple diffusion across membranes using the movement of oxygen and carbon dioxide as examples.

Recall the structures, locations and functions of integral and peripheral proteins in membranes.

Describe the movement of water molecules across membranes by osmosis, and the role of aquaporins.

Understand the structure and function of channel proteins for facilitated diffusion.

Understand the functioning of pump proteins for active transport.

Explain selectivity in membrane permeability.

Describe the structure and function of glycoproteins and glycolipids.

10:

Draw and describe th fluid mosaic model of membrane structure, including: peripheral and integral proteins, glycoproteins, phospholipids and cholesterol.

B2.1: Further membranes and transport (HL)

Recall the relationships between fatty acid composition of lipid bilayers and their fluidity.

Understand cholesterol and its role in membrane fluidity in animal cells.

Explain membrane fluidity and the fusion and formation of vesicles by “endocytosis” and “exocytosis”, including examples of each process.

Understand gated ion channels in neurons, including nicotinic acetylcholine receptors and sodium and potassium channels.

Recall sodium–potassium pumps as an example of exchange transporters, outlining the importance of these pumps in generating membrane potentials.

State the importance of sodium-dependent glucose cotransporters as examples of indirect active transport in the intenstines and nephrons.

Describe the adhesion of cells to form tissues, including the term “cell-adhesion molecules” (CAMs).

B2.2: Organelles & compartmentalisation

Understand organelles as discrete subunits of cells that are adapted to perform specific functions.

State the advantage of the separation of the nucleus and cytoplasm into separate compartments.

Recall the advantages of compartmentalization in the cytoplasm of cells.

B2.2: Further organelles (HL)

State the adaptations of the mitochondrion for production of ATP by aerobic cell respiration.

Recall the adaptations of the chloroplast for photosynthesis, including: the large surface area, small volumes of fluid inside thylakoids, and compartmentalization of enzymes and substrates of the Calvin cycle in the stroma.

Describe the functional benefits of the double membrane of the nucleus.

Understand the structure and function of free ribosomes, and of the rough endoplasmic reticulum.

Recall the structure and function of the Golgi apparatus with regards to proteins.

Recall the structure and function of vesicles in cells, including clathrin.

B2.3: Cell specialisation

Describe the production of unspecialized cells following fertilization and their development into specialized cells by differentiation.

Recall the properties of stem cells.

State the location and function of stem cell niches in adult humans, using two examples.

Describe the differences between totipotent, pluripotent and multipotent stem cells.

Expplain cell size as an aspect of specialization, including: male and female gametes, red and white blood cells, neurons and striated muscle fibres.

Understand surface area-to-volume ratios and their constraints on cell size.

B2.3: Further cell specialisation (HL)

Describe adaptations to increase surface area-to-volume ratio, including: flattening of cells, microvilli and invagination. Appreciate erythrocytes and proximal convoluted tubule cells as examples.

Recall the adaptations of type I and type II pneumocytes in alveoli.

Recall the adaptations of cardiac muscle cells and striated muscle fibres.

Explain the adaptations of sperm and egg cells in humans.

C2.1: Chemical signalling (HL)

Recall receptors as proteins with binding sites for specific signalling chemicals, including use of the term “ligand” for the signalling chemical.

Recall cell signalling by bacteria in quorum sensing using the example of bioluminescence in the marine bacterium Vibrio fischeri.

Distinguish hormones, neurotransmitters, cytokines and calcium ions as examples of functional categories of signalling chemicals in animals.

Describe the chemical diversity of hormones and neurotransmitters, including: amines, proteins, steroids, amino acids, and nitrous oxide.

Contrast localized and distant effects of signalling molecules.

Outline the differences between transmembrane receptors in a plasma membrane and intracellular receptors in the cytoplasm or nucleus.

Understand the tnitiation of signal transduction pathways by receptors.

Recall transmembrane receptors and their association to neurotransmitters and changes to membrane potential.

Recall transmembrane receptors that activate G proteins.

10:

Explain the mechanism of action of epinephrine (adrenaline) receptors, including G protein and cyclic AMP (cAMP).

11:

Recall insulin as an example of a pathway involving transmembrane receptors with tyrosine kinase activity.

12:

Recall intracellular receptors that affect gene expression, including: oestradiol, progesterone, and testosterone as examples.

13:

Explain the effects of the hormones oestradiol and progesterone on target cells.

14:

Describe the regulation of cell signalling pathways by positive and negative feedback, including examples for each.

C2.2: Neural signalling

Describe neurons as cells within the nervous system that carry electrical impulses.

Explain the generation of the resting potential by pumping to establish and maintain concentration gradients of sodium and potassium ions.

Describe nerve impulses as action potentials that are propagated along nerve fibres.

Explain variation in the speed of nerve impulses by comparing giant axons of squid and smaller non-myelinated nerve fibres.

Recall synapses as junctions between neurons and between neurons and effector cells.

Explain the release of neurotransmitters from a presynaptic membrane.

Explain the generation of an excitatory postsynaptic potential using acetylcholine as an example.

C2.2: Further neural signalling (HL)

Explain depolarization and repolarization during action potentials.

Understand the propagation of an action potential along a nerve fibre/axon as a result of local currents.

Interpret oscilloscope traces showing resting potentials and action potentials.

Understand saltatory conduction in myelinated fibres to achieve faster impulses.

Describe the rffects of exogenous chemicals on synaptic transmission using neonicotinoids as an example.

Describe inhibitory neurotransmitters and their generation of inhibitory postsynaptic potentials.

Understand the summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron.

Explain the perception of pain by neurons with free nerve endings in the skin.

Understand consciousness as a property that emerges from the interaction of individual neurons in the brain.

D2.1: Cell division

Understand the generation of new cells in living organisms by cell division.

Define cytokinesis as splitting of cytoplasm in a parent cell between daughter cells.

Explain equal and unequal cytokinesis, including oogenesis in humans and budding in yeast as examples of unequal cytokinesis.

Explain the roles of mitosis and meiosis in eukaryotes.

Understand DNA replication as a prerequisite for both mitosis and meiosis.

Recall the phases of mitosis.

Recall condensation and movement of chromosomes as shared features of mitosis and meiosis.

Identify the phases of mitosis as viewed with a microscope or in a micrograph.

Describe and explain the stage of meiosis as a reduction division, including use of the terms “diploid” and “haploid”.

10:

Outline down syndrome and non-disjunction as an example of an error in meiosis.

11:

Describe meiosis as a source of variation.

D2.1: Cell cycle (HL)

Understand the process of cell proliferation for growth, cell replacement and tissue repair, including skin, plant meristems and early-stage animal embryos as examples.

Describe the phases of the cell cycle, including: G1, S and G2 as the stages of interphase, followed by mitosis and then cytokinesis.

Understand cell growth during interphase.

Describe the control of the cell cycle using cyclins. Specific examples are not required.

Describe the consequences of mutations in genes that control the cell cycle, including use of the terms: "proto-oncogenes", "oncogenes", and "tumour suppressor genes".

Outline the differences between tumours in rates of cell division and growth and in the capacity for metastasis and invasion of neighbouring tissue. Use the terms: “benign”, “malignant”, “primary tumour” and “secondary tumour”, and distinguish between tumours that do and do not cause cancer.

D2.2: Gene expression (HL)

Define gene expression as the mechanism by which information in genes has effects on the phenotype.

Describe the regulation of transcription by proteins that bind to specific base sequences in DNA, including: promoters, enhancers and transcription factors.

Understand the control of the degradation of mRNA as a means of regulating translation.

Define epigenesis as the development of patterns of differentiation in the cells of a multicellular organism.

Outline differences between the genome, transcriptome and proteome of individual cells.

Understand methylation of the promoter and histones in nucleosomes as examples of epigenetic tags.

Understand epigenetic inheritance through heritable changes to gene expression.

Recall examples of environmental effects on gene expression in cells and organisms, including alteration of methyl tags on DNA in response to air pollution.

Understand the consequences of removal of most but not all epigenetic tags from the ovum and sperm through differences in tigons and ligers (lion–tiger hybrids).

10:

Investigate the effects of the environment on gene expression within monozygotic twin studies.

11:

Recall the external factors impacting the pattern of gene expression, including one example of a hormonal and one biochemical factor.

D2.3: Water potential

Understand solvation with water as the solvent, including: hydrogen bond formation, and attractions between ions and polar water molecules.

Explain water movement from less concentrated to more concentrated solutions, including use of the terms “hypertonic”, “hypotonic” and “isotonic”.

Describe water movement by osmosis into or out of cells, including use of the terms: hypotonic, hypertonic, and isotonic.

Predict changes due to water movement in plant tissue bathed in hypotonic and those bathed in hypertonic solutions.

Describe the effects of water movement on cells that lack a cell wall, including swelling and bursting in a hypotonic medium, and shrinkage and crenation in a hypertonic medium.

Describe the effects of water movement on cells with a cell wall, including use of the terms "turgor" and "plasmolysis".

Recall the medical applications of isotonic solutions, including intravenous fluids and bathing of organs for transplantation.

D2.3: Further water potential (HL)

Define water potential as the potential energy of water per unit volume.

Understand the reasons for movement of water from higher to lower water potential with regards to potential energy.

Understand the contributions of solute potential and pressure potential to the water potential of cells with walls, including use of the equation ψw = ψs + ψp.

Explain water potential and water movements in plant tissue when bathed in either a hypotonic or hypertonic solution.

3 - Organisms

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Excel in IB Biology Topic 3: Organisms. Explore diverse biological systems with in-depth resources covering organism classification, cladistics, and biodiversity. Understand vital physiological mechanisms, including plant and animal gas exchange, internal transport, muscle motility, immune defence against disease, reproduction, monogenic and polygenic inheritance, and human homeostasis.

Subtopic

Understanding

A3.1: Diversity of organisms

Understand the variation between organisms as a defining feature of life.

Recall that species are groups of organisms with shared traits according to Linnaeus.

Use the Binomial system for naming organisms.

Understand the biological species concept: a group of organisms that can breed and produce fertile offspring. Recall challenges associated with this definition.

State the difficulties distinguishing between populations and species due to divergence of non- interbreeding populations during speciation.

Appreciate diversity in chromosome numbers of plant and animal species, specifically in humans and chimpanzees.

Classify chromosomes invovled in Karyotyping and karyograms and analyse the evidence for the hypothesis that chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 with a shared primate ancestor.

Understand that the genome is all the genetic information of an organism, and variations give diversity within species.

Recall the diversity of eukaryote genomes and that variation between species is much larger than variation within a species.

10:

Be able to compare genome sizes from a database.

11:

State current and potential future uses of whole genome sequencing.

A3.1: Further diversity (HL)

State the difficulties applying the biological species concept to asexually reproducing species and to bacteria that have horizontal gene transfer.

Explain how chromosome numbers are a shared trait within a species.

Engage with local plant or animal species to develop a dichotomous key.

Identify species from environmental DNA in a habitat using barcodes.

A3.2: Classification & cladistics (HL)

Understand the need for classification of organisms.

Recall the difficulties of classifying organisms into the traditional hierarchy of taxa.

State the advantages of classification corresponding to evolutionary relationships, including predictions within clades.

Recall clades as groups of organisms with common ancestry and shared characteristics.

Understand the use of the gradual accumulation of sequence differences as the basis for estimates of when clades diverged from a common ancestor (molecular clock).

Use example base sequences of genes or amino acid sequences of proteins to construct cladograms.

Analyse cladograms to deduce evolutionary relationships, common ancestors and clades. Understand the terms “root”, “node” and “terminal branch”.

Use cladistics to investigate whether the classification of groups corresponds to evolutionary relationships.

Understand the classification of all organisms into three domains using evidence from rRNA base sequences.

B3.1: Gas exchanges

Recall gas exchange as a vital function in all organisms and link this to surface area-to-volume ratio.

State the properties of gas-exchange surfaces, including: permeability, thin tissue layer, moisture and large surface area.

Outline the maintenance of concentration gradients at exchange surfaces in animals.

Recall the adaptations of mammalian lungs for gas exchange.

Explain the ventilation of the lungs, including: the diaphragm, intercostal muscles, abdominal muscles and ribs.

Understand measurement of lung volumes, including: tidal volume, vital capacity, and inspiratory and expiratory reserves.

Recall adaptations for gas exchange in leaves.

Describe the distribution of tissues in a leaf using a drawn diagram.

Explain transpiration as a consequence of gas exchange in a leaf and state the impacting factors.

10:

Determine stomatal density using micrographs or leaf casts.

B3.1: Further gas exchange (HL)

Recall the adaptations of foetal and adult haemoglobin for the transport of oxygen.

Understand the Bohr shift.

Explain the shape of oxygen dissociation curves as a means of representing the affinity of haemoglobin for oxygen.

B3.2: Transport

Recall the adaptations of capillaries for the exchange of materials between blood and the internal and external environment.

Describe the structure of arteries and veins in micrographs.

Explain the adaptations of arteries for the transport of blood away from the heart.

Perform measurement of pulse rates.

State the adaptations of veins for the return of blood to the heart.

Outline the causes and consequences of occlusion of the coronary arteries, and study related epidemiolgical data.

Explain the transport of water from roots to leaves during transpiration due to cohesion.

Recall the adaptations of xylem vessels for the transport of water.

Draw and identify the distribution of tissues in a transverse section of the stem of a dicotyledonous plant.

10:

Draw and identify the distribution of tissues in a transverse section of the root of a dicotyledonous plant.

B3.2: Further transport (HL)

Explain the release and reuptake of tissue fluid in capillaries due to pressure differences.

Outline the composition of, and exchange of substances between. tissue fluid and cells.

Understand the drainage of excess tissue fluid into lymph ducts.

Describe the differences between the single circulation of bony fish and the double circulation of mammals.

Recall the adaptations of the mammalian heart for delivering pressurized blood to the arteries, including the: cardiac muscle, pacemaker, atria, ventricles, valves, septum and coronary vessels. Identify these structures on visual diagrams.

Recall the stages in the cardiac cycle and interpret systolic and diastolic blood pressure measurements from data and graphs.

Explain the generation of root pressure in xylem vessels by active transport of mineral ions.

Describe the adaptations of phloem sieve tubes and companion cells for translocation of sap, including: sieve plates, reduced cytoplasm and organelles, no nucleus for sieve tube elements and presence of many mitochondria.

B3.3: Muscle & motility (HL)

Understand the adaptations for movement as a universal feature of living organisms, including one motile and one sessile species as examples.

Understand the sliding filament model of muscle contraction.

Explain the role of the protein titin and antagonistic muscles in muscle relaxation.

Explain the structure and function of motor units in skeletal muscle, including: the motor neuron, muscle fibres, and neuromuscular junctions.

Appreciate the roles of skeletons as anchorage for muscles and as levers.

Describe the movement at a synovial joint, including the roles of: bones, cartilage, synovial fluid, ligaments, muscles and tendons. Name the femur and pelvis.

Compare the range of motion of different joints.

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

State the reasons for locomotion.

10:

State the adaptations for swimming in marine mammals, including: streamlining, flippers, a tail, and changes to the airways.

C3.1: Body systems

Understand system integration as a necessary process in living systems.

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

Distinguish between the roles of the nervous system and endocrine system in sending messages.

Understand the brain as a central information integration organ.

Describe the spinal cord as an integrating centre for unconscious processes and distinguish between conscious and unconscious processes.

Understand the input to the spinal cord and cerebral hemispheres through sensory neurons.

Understand the output from the cerebral hemispheres to muscles through motor neurons.

Recall nerves as bundles of nerve fibres of both sensory and motor neurons, including their structure.

Understand pain reflex arcs as an example of involuntary responses with skeletal muscle as the effector.

10:

Recall the role of the cerebellum in coordinating skeletal muscle contraction and balance.

11:

Understand the modulation of sleep patterns by melatonin secretion as a part of circadian rhythms.

12:

Describe epinephrine (adrenaline) secretion by the adrenal glands to prepare the body for vigorous activity.

13:

Describe the control of the endocrine system by the hypothalamus and pituitary gland.

14:

Recall feedback control of heart rate following sensory input from baroreceptors and chemoreceptors. Understand the role of the medulla in coordinating responses and sending nerve impulses to the heart to change the heart’s stroke volume and heart rate.

15:

Understand feedback control of ventilation rate following sensory input from chemoreceptors.

16:

Explain the control of peristalsis in the digestive system by the central nervous system and enteric nervous system (ENS).

C3.1: Plant systems (HL)

Interpret and record observations of tropic responses in seedlings.

Define positive phototropism as a directional growth response to lateral light in plant shoots.

Define phytohormones as signalling chemicals controlling growth, development and response to stimuli in plants.

Explain auxin efflux carriers as an example of maintaining concentration gradients of phytohormones.

Explain the promotion of cell growth by auxin, including the promotion of hydrogen ion secretion into the apoplast.

Recall the interactions between auxin and cytokinin as a means of regulating root and shoot growth.

Exlain positive feedback in fruit ripening and ethylene production.

C3.2: Defence against infectious disease

Recall pathogens as the cause of infectious diseases.

Describe skin and mucous membranes as a primary defence.

Explain the sealing of cuts in skin by blood clotting, including the release of clotting factors, the cascade pathway, and trapping of erythrocytes to form a clot.

Explain the differences between the innate immune system and the adaptive immune system.

Describe infection control by phagocytes, including amoeboid movement from blood to sites of infection.

Understand lymphocytes as cells in the adaptive immune system that cooperate to produce antibodies.

Define antigens as recognition molecules that trigger antibody production.

Explain the activation of B-lymphocytes by helper T-lymphocytes.

Explain the multiplication of activated B-lymphocytes to form clones of antibody-secreting plasma cells.

10:

Undesrtand immunity as a consequence of retaining memory cells.

11:

Describe transmission of HIV in body fluids, including examples.

12:

Understand the infection of lymphocytes by HIV with AIDS as a consequence.

13:

Define antibiotics as chemicals that block processes occurring in bacteria but not in eukaryotic cells.

14:

Describe the evolution of resistance to several antibiotics in strains of pathogenic bacteria.

15:

Define zoonoses as infectious diseases that can transfer from other species to humans, including the examples of tuberculosis, rabies and Japanese encephalitis, and COVID-19.

16:

Explain vaccines and the process of immunization.

17:

Describe herd immunity and the prevention of epidemics.

18:

Evaluate data related to the COVID-19 pandemic

D3.1: Reproduction

Recall the differences between sexual and asexual reproduction, and the comparative advantages of either.

Describe the role of meiosis and fusion of gametes in the sexual life cycle.

Distinguish between male and female sexes in sexual reproduction with regards to: gamete location, size, food reserves, the numbers of gametes and the reproductive strategies.

Draw and identify the anatomy of the human male and female reproductive systems.

Recall the changes during the ovarian and uterine cycles and their hormonal regulation including reference to: oestradiol, progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and both positive and negative feedback.

Describe the process of fertilization in humans, including: fusion, entry, dissolution of nuclear membranes, and joint mitosis to produce two diploid nuclei.

Explain the use of hormones in in vitro fertilization (IVF) treatment.

Explain sexual reproduction in flowering plants, including: production of gametes, pollination, pollen development and fertilization.

Draw and identify the features of an insect-pollinated flower.

10:

Recall the methods of promoting cross-pollination.

11:

Understand self-incompatibility mechanisms to increase genetic variation within a species.

12:

Describe the dispersal and germination of seeds, including the utilisation of food reserves.

D3.1: Further reproduction (HL)

Explain the control of the developmental changes of puberty by gonadotropin-releasing hormone and steroid sex hormones.

Explain spermatogenesis and oogenesis in humans, including: mitosis, cell growth, two divisions of meiosis and differentiation.

Explain the mechanisms to prevent polyspermy.

Describe the development of a blastocyst and subsequent implantation into the endometrium.

Describe pregnancy testing by detection of human chorionic gonadotropin secretion.

Understand the role of the placenta in foetal development inside the uterus, including the exchange processes that occur.

Recall the hormonal control of pregnancy and childbirth.

Outline hormone replacement therapy and the risk of coronary heart disease.

D3.2: Monogenic inheritance

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

Perform methods for conducting genetic crosses in flowering plants, including use of the terms: “P generation”, “F1 generation”, “F2 generation” and “Punnett grid”.

Define the genotype as the combination of alleles inherited by an organism and understand the terms “homozygous” and “heterozygous”, and appreciate the distinction between genes and alleles.

Define the phenotype as the observable traits of an organism resulting from genotype and environmental factors and suggest related traits.

Understand the effects of dominant and recessive alleles on phenotypes.

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

Recall phenylketonuria (PKU) as an example of a human disease due to a recessive allele.

Understand single-nucleotide polymorphisms and multiple alleles in gene pools.

Recall ABO blood groups as an example of multiple alleles and use IA, IB and i to denote the alleles.

10:

Understand the differences between incomplete dominance and codominance, including the AB blood type (I^AI^B) and four o'clock flower (Mirabilis jalapa) as examples.

11:

Understand sex determination in humans and inheritance of genes on sex chromosomes.

12:

Recall haemophilia as an example of a sex-linked genetic disorder.

13:

Understand and interpret pedigree charts to deduce patterns of inheritance of genetic disorders.

14:

Understand continuous variation due to polygenic inheritance and/or environmental factors, using skin colour in humans as an example.

15:

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

D3.2: Polygenic inheritance (HL)

Understand segregation and independent assortment of unlinked genes in meiosis.

Utilise punnett grids for predicting genotypic and phenotypic ratios in dihybrid crosses involving pairs of unlinked autosomal genes, and understand how the 9:3:3:1 and 1:1:1:1 ratios are derived.

Appreciate Loci of human genes and their polypeptide products.

Explain autosomal gene linkage and use appropriate symbols to denote them.

Understand recombinants in crosses involving two linked or unlinked genes.

Use the chi-squared test on data from dihybrid crosses and understand statistical significance, null/alternative hypothesis, and the idea of observed versus expected results.

D3.3: Homeostasis

Define homeostasis as the maintenance of the internal environment of an organism.

Explain negative feedback loops in homeostasis.

Recall the regulation of blood glucose as an example of the role of hormones in homeostasis.

Explain the physiological changes that form the basis of type 1 and type 2 diabetes.

Explain thermoregulation as an example of negative feedback control, including: the roles of peripheral thermoreceptors, the hypothalamus, pituitary gland, thyroxin and muscle and adipose tissue as effectors.

Outline thermoregulation mechanisms in humans including: vasodilation, vasoconstriction, shivering, sweating, uncoupled respiration in brown adipose tissue and hair erection.

D3.3: Further homeostasis (HL)

Understand the role of the kidney in osmoregulation and excretion.

Describe the role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion.

Describe the role of the loop of Henle.

Explain osmoregulation by water reabsorption in the collecting ducts, including: osmoreceptors, antidiuretic hormone (ADH) secretion, and aquaporins.

Describe the changes in blood supply to organs in response to changes in activity using the examples of skeletal muscles, gut, brain and kidneys during sleep, vigorous physical activity and wakeful rest.

4 - Ecosystems

Mark Complete

Navigate IB Biology Topic 4: Ecosystems with our comprehensive study guides. Learn about the intricate interactions between organisms and their environments, covering evolution, speciation, and biodiversity conservation. Master core ecological concepts including energy and matter transfer, population dynamics, natural selection, ecological niches, stability, and the biological impacts of climate change.

Subtopic

Understanding

A4.1: Evolution & speciation

Define evolution as the change in the heritable characteristics of a population.

State the evidence for evolution from base sequences in DNA or RNA and amino acid sequences in proteins.

Recall the evidence for evolution from selective breeding of domesticated animals and crop plants.

Recall the evidence for evolution from homologous structures, including the example of pentadactyl limbs.

Recall convergent evolution as the origin of analogous structures, including one example.

Understand speciation, the splitting of pre-existing species, as the only way in which new species have appeared.

Explaine the roles of reproductive isolation and differential selection in speciation, using the separation of bonobos and common chimpanzees by the Congo River as a specific example.

A4.1: Further speciation (HL)

State the differences and similarities between sympatric and allopatric speciation.

Recall adaptive radiation as a source of biodiversity.

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

Recall the abrupt speciation in plants by hybridization and polyploidy, using knotweed or smartweed (genus Persicaria) as an example.

A4.2: Conservation of biodiversity

Defined biodiversity as the variety of life in all its forms, levels and combinations. Define ecosystem diversity, species diversity and genetic diversity.

Make comparisons between the current number of species on Earth and past levels of biodiversity.

Recall the causes of anthropogenic species extinction.

Recall two case studies of the causes of ecosystem loss,including the loss of mixed dipterocarp forest in Southeast Asia.

Recall evidence for a biodiversity crisis through examples.

Recall human population growth as a major cause of the current biodiversity crisis, as well as: hunting, urbanization, deforestation, pollution, diseases and invasive alien species.

Appreciate the need for several approaches to the conservation of biodiversity.

Appreciate the selection of evolutionarily distinct and globally endangered species for conservation prioritization in the EDGE of Existence programme.

B4.1: Adaptations

Define a habitat as the place in which a community, species, population or organism lives.

Recall adaptations of organisms to the abiotic environment of their habitat, including a grass species and tree species.

Outline abiotic variables affecting species distribution for both plants and animals.

Use transect data to correlate the distribution of plant or animal species with an abiotic variable.

Recall the conditions required for coral reef formation, including: water depth, pH, salinity, clarity, and temperature.

Understand abiotic factors as the determinants of terrestrial biome distribution and illustrate this using a graph.

Define biomes as groups of ecosystems with similar communities due to similar abiotic conditions and convergent evolution.

Explain adaptations to life in hot deserts and tropical rainforests, including examples in named species of plants and animals.

B4.2: Ecological niches

Understand the ecological niche as the role of a species in an ecosystem, and the interactions that influence growth, survival and reproduction.

State differences between organisms that are obligate anaerobes, facultative anaerobes and obligate aerobes.

Recall photosynthesis as the mode of nutrition in plants, algae and several groups of photosynthetic prokaryotes.

Understand holozoic nutrition in animals.

Explain mixotrophic nutrition in some protists, includng Euglena as a well-known freshwater example.

State that saprotrophic nutrition occurs in some fungi and bacteria (decomposers).

Understand the diversity of nutrition in archae.

Explain the relationship between dentition and the diet of omnivorous and herbivorous representative members of the family Hominidae.

Recall the adaptations of herbivores for feeding on plants and of plants for resisting herbivory.

10:

State the adaptations of predators for finding, catching and killing prey and of prey animals for resisting predation.

11:

Explain the adaptations of plants for harvesting light, including examples from forest ecosystems.

12:

Appreciation fundamental niches as the potential of a species based on adaptations and tolerance limits, and realized niches as the actual extent of a species niche when in competition with other species.

13:

Explain competitive exclusion and the uniqueness of ecological niches using an example.

C4.1: Populations & communities

Define populations as interacting groups of organisms of the same species living in an area.

Estimate population size by random sampling.

Describe random quadrat sampling as a process to estimate population size for sessile organisms.

Use of the capture–mark–release–recapture method, and the Lincoln index, to estimate population size for motile organisms.

Define carrying capacity and competition for limited resources, using examples.

Explain negative feedback control of population size by density-dependent factors.

Interpret population growth curves through at least one case study in an ecosystem.

Model sigmoidal population growth curves by collecting data regarding population growth.

Explain competition versus cooperation in intraspecific relationships through a range of real examples.

10:

Define a community as all of the interacting organisms in an ecosystem.

11:

Understand herbivory, predation, interspecific competition, mutualism, parasitism and pathogenicity as categories of interspecific relationship within communities, using examples for each.

12:

Define mutualism as an interspecific relationship that benefits both species, including the examples of: root nodules in Fabaceae (legume family), mycorrhizae in Orchidaceae (orchid family) and zooxanthellae in hard corals.

13:

Describe resource competition between endemic and invasive species using examples.

14:

Recall tests for interspecific competition.

15:

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

16:

Define predator–prey relationships as an example of density-dependent control of animal populations, including a real case study.

17:

Understand both top-down and bottom-up control of populations in communities.

18:

Understand allelopathy and secretion of antibiotics, including one specific example of each.

C4.2: Energy & matter transfer

Define ecosystems as open systems in which both energy and matter can enter and exit.

Describe sunlight as the principal source of energy that sustains most ecosystems. Include exceptions such as ecosystems in caves.

Describe the flow of chemical energy through food chains.

Construct food chains and food webs to represent feeding relationships in a community.

Describe the supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms.

Define autotrophs as organisms that use external energy sources to synthesize carbon compounds from simple inorganic substances.

Understand the use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs, using iron-oxidizing bacteria as an example of a chemoautotroph.

Define heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesize the carbon compounds that they require.

Describe the release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration.

10:

Classify organisms into trophic levels, including use of the terms: “producer”, “primary consumer”, “secondary consumer” and “tertiary consumer”.

11:

Construct energy pyramids.

12:

Explain the reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels.

13:

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

14:

Explain restrictions on the number of trophic levels in ecosystems due to energy losses.

15:

Explain primary production as the accumulation of carbon compounds in biomass by autotrophs.

16:

Define secondary production as the accumulation of carbon compounds in biomass by heterotrophs.

17:

Construct carbon cycle diagrams.

18:

Outline ecosystems as carbon sinks and carbon sources.

19:

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

20:

Analyse the Keeling Curve in terms of photosynthesis, respiration and combustion.

21:

Explain the dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration.

22:

Understand the recycling of all chemical elements required by living organisms in ecosystems.

D4.1: Natural selection

Define natural selection as the mechanism driving evolutionary change.

Describe the roles of mutation and sexual reproduction in generating the variation on which natural selection acts.

Explain the overproduction of offspring and competition for resources as factors that promote natural selection, including examples.

Reacll abiotic factors as selection pressures, including examples of density-independent factors.

Understand the differences between individuals in adaptation, survival and reproduction as the basis for natural selection.

Understand the requirement that traits are heritable for evolutionary change to occur.

Recall sexual selection as a selection pressure in animal species and illustrate this using suitable examples such as the evolution of the plumage of birds of paradise.

Model sexual and natural selection based on experimental control of selection pressures.

D4.1: Further natural selection (HL)

Understand the concept of the gene pool.

Appreciate allele frequencies of geographically isolated populations, including one example in humans.

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

Explain differences between directional, disruptive and stabilizing selection.

Recall the Hardy–Weinberg equation in calculations of allele or genotype frequencies: p² + 2pq + q² = 1.

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

Understand artificial selection by the deliberate choice of traits.

D4.2: Stability & change

Illustrate stability as a property of natural ecosystems.

Recall the requirements for stability in ecosystems including: the supply of energy, recycling of nutrients, genetic diversity and climatic variables remaining within tolerance levels.

Recall the deforestation of Amazon rainforest as an example of a possible tipping point in ecosystem stability. Understand the importance of transpiration, cooling, air flows and rainfall to global sustainability.

Understand the use of a Mesocosm model to investigate the effect of variables on ecosystem stability.

Understand the role of keystone species in the stability of ecosystems.

Assess the sustainability of resource harvesting from natural ecosystems including one terrestrial plant species and one species of marine fish as examples.

Recall the factors affecting the sustainability of agriculture, including: soil erosion, leaching of nutrients, supply of fertilizers, pollution due to agrochemicals, and carbon footprint.

Explain the eutrophication of aquatic and marine ecosystems due to leaching, including use of the term biochemical oxygen demand (BOD).

Understand the biomagnification of pollutants in natural ecosystems including DDT and mercury as examples.

10:

Explain the effects of microplastic and macroplastic pollution of the oceans, including examples.

11:

Describe restoration of natural processes in ecosystems by rewilding, specifically the example of Hinewai Reserve in New Zealand.

D4.2: Ecological stability (HL)

Describe ecological succession and its causes.

Describe the changes occurring during primary succession using any suitable terrestrial example to illustrate: increases in size of plants, amount of primary production, species diversity, complexity of food webs and amount of nutrient cycling.

Understand cyclical succession in ecosystems through an example.

Understand climax communities and arrested succession through use of the examples of grazing by farm livestock and drainage of wetlands.

D4.3: Climate changes

Recall the anthropogenic causes of climate change with regards to carbon dioxide and methane concentrations.

Explain positive feedback cycles in global warming, including: release of CO₂ from oceans, loss of reflective snow and ice, accelerating rates of decomposition in permafrost, release of methane and increases in droughts and forest fires.

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

Describe melting of landfast ice and sea ice as examples of polar habitat change, including the loss of breeding grounds of the emperor penguin (Aptenodytes forsteri).

Explain changes in ocean currents altering the timing and extent of nutrient upwelling.

Understand poleward and upslope range shifts of temperate species, including tropical-zone montane bird species and North American tree species.

Recall threats to coral reefs as an example of potential ecosystem collapse.

Outline afforestation, forest regeneration and restoration of peat-forming wetlands as approaches to carbon sequestration.

D4.3: Further climate change (HL)

Define phenology as research into the timing of biological events.

Understand disruption to the synchrony of phenological events by climate change, including spring growth of the Arctic mouse-ear chickweed and arrival of migrating reindeer as an example. Recall a further local example, or use the breeding of the great tit and peak biomass of caterpillars in north European forests in its place.

Outine the increases to the number of insect life cycles within a year due to climate change through use of the spruce bark beetle as an example.

Recall evolution as a consequence of climate change, including changes in the fitness of colour variants of the tawny owl (Strix aluco) as an example.