IB Biology Mind Map Year 12 SL and HL

Annotations:

• https://blog.prepscholar.com/the-complete-ib-biology-syllabus-standard-level-sl-and-higher-level-hl

1. Topic 1: Cells
   1. Introduction to cells
      1. Prokaryotic cells
         1. Plasma membrane
            1. Cytoplasm
               1. Site of biochemical reactions
            2. Controls entry and exit of substances
         2. Pili
            1. Hair- like structure
               1. Connect bacteria together
         3. Flagella
            1. Propels cells
         4. Ribosomes
            1. Synthesize proteins
               1. Translation of messenger RNA
                  1. 70 s
         5. Nucleoid
            1. Naked DNA
         6. Binary fission
         7. ''Before the nucleus''
         8. Cell wall
            1. Prevents damage
               1. Retains structure
      2. Eukaryotic cells
         1. Free ribosomes
            1. Synthesize proteins for use in the cytoplasm
               1. 80 s
         2. Plasma membrane
            1. Controls entry and exit of substances
         3. Golgi apparatus
            1. Processes proteins before secretion
         4. Rough endoplasmic reticulum
            1. Synthesise proteins for secretion from cell
         5. Lysosome
            1. Store digestive enzymes
         6. Mitochondria
            1. Carry out aerobic respiration
         7. Nucleus
            1. Stores genetic information
               1. Chromosomes
                  1. Strands of DNA associated with protein
                     1. 4+
         8. The origin of eukaryotic cells can be explained by the endosymbiotic theory.
      3. Stem Cells
         1. Retain ability to differentiate along different pathways
         2. Small number of embryonic cells still retained by adult body
            1. Potential for tissue repair
               1. Heart regeneration
               2. Skin grafts
               3. Cord blood for leukaemia
               4. Therapeutic use: bone marrow transplant as a result of chemotheralpy
   2. Ultrastructure of cells
      1. Prokaryotes have a simple cell structure without compartmentalization.
      2. Eukaryotes have a compartmentalized cell structure.
   3. Membrane structure
      1. Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.
      2. Membrane proteins are diverse in terms of structure, position in the membrane and function.
      3. Cholesterol is a component of animal cell membranes.
   4. Membrane transport
      1. Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.
      2. The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.
   5. The origin of cells
      1. Cell Theory
         1. 1. All living organisms are composed of cells
            1. 2. Cells are the smallest unit of life
               1. 3. Cells come from pre- existing cells
                  1. 4. The first cells must have arisen from non-living material.
         2. Proof
            1. One sealed soup container: no decay
            2. Bacteria in air
            3. Other open soup container: decay
   6. Cell division
      1. Mitosis is division of the nucleus into two genetically identical daughter nuclei.
      2. Chromosomes condense by supercoiling during mitosis.
      3. Cytokinesis occurs after mitosis and is different in plant and animal cells.
      4. Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
      5. Cyclins are involved in the control of the cell cycle
      6. Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
2. Topic 2: Molecular Biology
   1. Molecules to metabolism
      1. Molecular biology explains living processes in terms of the chemical substances involved.
      2. Carbon atoms can form four covalent bonds allowing a diversity of stable compounds to exist.
      3. Life is based on carbon compounds including carbohydrates, lipids, proteins and nucleic acids.
      4. Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism.
      5. Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions.
      6. Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers.
   2. Water
      1. H2O
         1. Hydrophobic substances are those that are nonpolar and therefore don't dissolve in water
         2. Hydrophilic substances are those that are polar, are attached to water, and dissolve in it
         3. Properties
            1. Thermal: high specific heat which makes it difficult to change the temperature of the water and high heat of vaporisation which causes difficulty in changing the state of the water
            2. Cohesive: weak H bond give water strong cohesive forces causing water molecules to stick together which makes the molecules resistant to objects penetrating the surface i.e. surface tension
            3. Adhesion: water molecules stick to other charged or polar molecules
            4. Solvent: positive atoms are attracted to the negative oxygen region while negative atoms are attracted to the positive hydrogen region meaning water can dissolve substances with polar and charged regions.
   3. Carbohydrates and lipids
      1. contain carbon, hydrogen and oxygen
      2. it's building block is a simple sugar
      3. commonly ring shaped molecules
   4. Proteins
      1. Amino acids are linked together by condensation to form polypeptides.
      2. There are 20 different amino acids in polypeptides synthesized on ribosomes.
      3. Amino acids can be linked together in any sequence giving a huge range of possible polypeptides.
      4. The amino acid sequence of polypeptides is coded for by genes.
      5. A protein may consist of a single polypeptide or more than one polypeptide linked together.
      6. The amino acid sequence determines the three-dimensional conformation of a protein.
      7. Living organisms synthesize many different proteins with a wide range of functions.
      8. Every individual has a unique proteome.
   5. Enzymes
      1. Enzymes have an active site to which specific substrates bind.
      2. Enzyme catalysis involves molecular motion and the collision of substrates with the active site.
      3. Enzymes can be denatured.
      4. Temperature, pH and substrate concentration affect the rate of activity of enzymes.
      5. Immobilized enzymes are widely used in industry.
   6. Structure of DNA and RNA
      1. The nucleic acids DNA and RNA are polymers of nucleotides.
      2. DNA differs from RNA in the number of strands present, the base composition and the type of pentose.
      3. DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
   7. DNA replication, transcription and translation
      1. The replication of DNA is semi-conservative and depends on complementary base pairing.
      2. Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds.
      3. DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a template.
      4. Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase.
      5. Translation is the synthesis of polypeptides on ribosomes.
      6. The amino acid sequence of polypeptides is determined by mRNA according to the genetic code.
      7. Codons of three bases on mRNA correspond to one amino acid in a polypeptide.
      8. Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA.
   8. Cell Respiration
      1. Cell respiration is the controlled release of energy from organic compounds to produce ATP.
      2. ATP from cell respiration is immediately available as a source of energy in the cell.
      3. Anaerobic cell respiration gives a small yield of ATP from glucose.
      4. Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
   9. Photosynthesis
      1. Photosynthesis is the production of carbon compounds in cells using light energy.
      2. Visible light has a range of wavelengths with violet the shortest wavelength and red the longest.
      3. Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours.
      4. Oxygen is produced in photosynthesis from the photolysis of water.
      5. Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide.
      6. Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
3. Topic 3: Genetics
   1. Genes
      1. A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.
      2. A gene occupies a specific position on a chromosome.
      3. The various specific forms of a gene are alleles.
      4. Alleles differ from each other by one or only a few bases.
      5. New alleles are formed by mutation.
      6. The genome is the whole of the genetic information of an organism.
      7. The entire base sequence of human genes was sequenced in the Human Genome Project.
   2. Chromosomes
      1. Prokaryotes have one chromosome consisting of a circular DNA molecule.
      2. Some prokaryotes also have plasmids but eukaryotes do not.
      3. Eukaryote chromosomes are linear DNA molecules associated with histone proteins.
      4. In a eukaryote species there are different chromosomes that carry different genes.
      5. Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes.
         1. Diploid nuclei have pairs of homologous chromosomes.
         2. Haploid nuclei have one chromosome of each pair.
      6. The number of chromosomes is a characteristic feature of members of a species.
      7. A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length.
      8. Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex.
   3. Meiosis
      1. One diploid nucleus divides by meiosis to produce four haploid nuclei.
      2. The halving of the chromosome number allows a sexual life cycle with fusion of gametes.
      3. DNA is replicated before meiosis so that all chromosomes consist of two sister chromatids.
      4. The early stages of meiosis involve pairing of homologous chromosomes and crossing over followed by condensation.
      5. Orientation of pairs of homologous chromosomes prior to separation is random.
      6. Separation of pairs of homologous chromosomes in the first division of meiosis halves the chromosome number.
      7. Crossing over and random orientation promotes genetic variation.
      8. Fusion of gametes from different parents promotes genetic variation.
   4. Inheritance
      1. Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed.
      2. Gametes are haploid so contain only one allele of each gene.
      3. The two alleles of each gene separate into different haploid daughter nuclei during meiosis.
      4. Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles.
      5. Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects.
      6. Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles.
      7. Some genetic diseases are sex-linked. The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes.
      8. Many genetic diseases have been identified in humans but most are very rare.
      9. Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer.
   5. Genetic modification and biotechnology
      1. Gel electrophoresis is used to separate proteins or fragments of DNA according to size.
      2. PCR can be used to amplify small amounts of DNA.
      3. DNA profiling involves comparison of DNA.
      4. Genetic modification is carried out by gene transfer between species.
      5. Clones are groups of genetically identical organisms, derived from a single original parent cell.
      6. Many plant species and some animal species have natural methods of cloning.
      7. Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
      8. Methods have been developed for cloning adult animals using differentiated cells.
4. Topic 4: Ecology
   1. Species, communities and ecosystems
      1. Species are groups of organisms that can potentially interbreed to produce fertile offspring.
      2. Members of a species may be reproductively isolated in separate populations.
      3. Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
      4. Consumers are heterotrophs that feed on living organisms by ingestion.
      5. Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
      6. Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
      7. A community is formed by populations of different species living together and interacting with each other.
      8. A community forms an ecosystem by its interactions with the abiotic environment.
      9. Autotrophs obtain inorganic nutrients from the abiotic environment.
      10. The supply of inorganic nutrients is maintained by nutrient cycling.
      11. Ecosystems have the potential to be sustainable over long periods of time.
   2. Energy flow
      1. Most ecosystems rely on a supply of energy from sunlight.
      2. Light energy is converted to chemical energy in carbon compounds by photosynthesis.
      3. Chemical energy in carbon compounds flows through food chains by means of feeding.
      4. Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
      5. Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.
      6. Living organisms cannot convert heat to other forms of energy.
         1. Heat is lost from ecosystems.
   3. Carbon cycling
      1. Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds.
      2. In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions.
      3. Carbon dioxide diffuses from the atmosphere or water into autotrophs.
      4. Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.
      5. Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground.
      6. Methane is oxidized to carbon dioxide and water in the atmosphere.
      7. Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks.
      8. Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.
      9. Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.
      10. Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone.
   4. Climate change
      1. Carbon dioxide and water vapour are the most significant greenhouse gases.
      2. Other gases including methane and nitrogen oxides have less impact.
      3. The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in the atmosphere.
      4. The warmed Earth emits longer wavelength radiation (heat).
      5. Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
      6. Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
      7. Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
      8. There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
5. Topic 8: Metabolism, cell respiration and photosynthesis
   1. Metabolism
      1. Metabolic pathways consist of chains and cycles of enzyme-catalysed reactions.
      2. Enzymes lower the activation energy of the chemical reactions that they catalyse.
      3. Enzyme inhibitors can be competitive or non-competitive.
      4. Metabolic pathways can be controlled by end-product inhibition.
   2. Cell respiration
      1. Cell respiration involves the oxidation and reduction of electron carriers.
      2. Phosphorylation of molecules makes them less stable.
      3. In glycolysis, glucose is converted to pyruvate in the cytoplasm.
      4. Glycolysis gives a small net gain of ATP without the use of oxygen.
      5. In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
      6. In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
      7. Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
      8. Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
      9. In chemiosmosis protons diffuse through ATP synthase to generate ATP.
      10. Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
      11. The structure of the mitochondrion is adapted to the function it performs.
   3. Photosynthesis
      1. Light-dependent reactions take place in the intermembrane space of the thylakoids.
      2. Light-independent reactions take place in the stroma.
      3. Reduced NADP and ATP are produced in the light-dependent reactions.
      4. Absorption of light by photosystems generates excited electrons.
      5. Photolysis of water generates electrons for use in the light-dependent reactions.
      6. Transfer of excited electrons occurs between carriers in thylakoid membranes.
      7. Excited electrons from Photosystem II are used to contribute to generate a proton gradient.
      8. In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate.
      9. Triose phosphate is used to regenerate RuBP and produce carbohydrates.
      10. Excited electrons from Photosystem I are used to reduce NADP.
      11. ATP synthase in thylakoids generates ATP using the proton gradient.
      12. Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP.
      13. Ribulose bisphosphate is reformed using ATP
      14. The structure of the chloroplast is adapted to its function in photosynthesis.
6. Topic 7: Nucleic acids
   1. DNA structure and replication
      1. Nucleosomes help to supercoil the DNA.
      2. DNA structure suggested a mechanism for DNA replication.
      3. DNA polymerases can only add nucleotides to the 3' end of a primer.
      4. DNA replication is continuous on the leading strand and discontinuous on the lagging strand.
      5. DNA replication is carried out by a complex system of enzymes.
      6. Some regions of DNA do not code for proteins but have other important functions.
   2. Transcription and gene expression
      1. Nucleosomes help to regulate transcription in eukaryotes.
      2. Transcription occurs in a 5' to 3' direction.
      3. Eukaryotic cells modify mRNA after transcription.
      4. Splicing of mRNA increases the number of different proteins an organism can produce.
      5. Gene expression is regulated by proteins that bind to specific base sequences in DNA.
      6. The environment of a cell and of an organism has an impact on gene expression.
   3. Translation
      1. The sequence and number of amino acids in the polypeptide is the primary structure.
      2. The secondary structure is the formation of alpha helices and beta pleated sheets stabilized by hydrogen bonding.
      3. The tertiary structure is the further folding of the polypeptide stabilized by interactions between R groups.
      4. The quaternary structure exists in proteins with more than one polypeptide chain.
      5. Initiation of translation involves assembly of the components that carry out the process.
      6. Synthesis of the polypeptide involves a repeated cycle of events.
      7. Disassembly of the components follows termination of translation.
      8. Free ribosomes synthesize proteins for use primarily within the cell.
      9. Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes.
      10. Translation can occur immediately after transcription in prokaryotes due to the absence of a nuclear membrane.
7. Topic 10: Genetics and evolution
   1. Meiosis
      1. Chromosomes replicate in interphase before meiosis.
      2. Crossing over is the exchange of DNA material between non-sister homologous chromatids.
      3. Crossing over produces new combinations of alleles on the chromosomes of the haploid cells.
      4. Chiasmata formation between non-sister chromatids can result in an exchange of alleles.
      5. Homologous chromosomes separate in meiosis I.
      6. Sister chromatids separate in meiosis II.
      7. Independent assortment of genes is due to the random orientation of pairs of homologous chromosomes in meiosis I.
   2. Inheritance
      1. Gene loci are said to be linked if on the same chromosome.
      2. Unlinked genes segregate independently as a result of meiosis.
      3. Variation can be discrete or continuous.
      4. The phenotypes of polygenic characteristics tend to show continuous variation.
      5. Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant.
   3. Gene pools and speciation
      1. A gene pool consists of all the genes and their different alleles, present in an interbreeding population.
      2. Speciation due to divergence of isolated populations can be gradual.
      3. Evolution requires that allele frequencies change with time in populations.
      4. Reproductive isolation of populations can be temporal, behavioural or geographic.
      5. Speciation can occur abruptly.