Edexcel International A Level Biology (YBI11) revision notes

International A Level Biology video lessons · Revision notes · International A Level Biology past papers

Clear revision notes for every topic, each beside its video lesson.

1 Chemistry for biologists

• Water: the dipole and why it dissolves things notes
• Monosaccharides and disaccharides notes
• Starch and glycogen: storing energy notes
• Core practical 1: estimating sugar and starch concentrations notes
• Lipids: triglycerides, saturated and unsaturated notes
• Amino acids and peptide bonds notes
• Primary to quaternary structure notes
• Globular and fibrous: haemoglobin and collagen notes

2 Mammalian transport systems

• Why many animals need a heart and circulation notes
• Blood and haemoglobin: carrying oxygen and carbon dioxide notes
• The oxygen dissociation curve notes
• The Bohr effect and fetal haemoglobin notes
• Arteries, veins and capillaries notes
• The structure of the mammalian heart notes
• The cardiac cycle and the pressure graph notes
• Dissecting a mammalian heart notes
• How atherosclerosis develops notes
• Blood clotting and its role in CVD notes

3 Cardiovascular health and risk

• Risk, correlation and cause notes
• Reading illness and mortality data notes
• Evaluating studies of health risk notes
• Risk factors for cardiovascular disease notes
• Energy balance, BMI and waist-to-hip ratio notes
• Blood cholesterol, HDLs and LDLs notes
• Dietary antioxidants and CVD notes
• Core practical 2: vitamin C content of food and drink notes
• Treatments for CVD: benefits and risks notes

4 Membranes and transport

• The fluid mosaic model notes
• Core practical 3: beetroot and membrane permeability notes
• Diffusion and facilitated diffusion notes
• Active transport, endocytosis and exocytosis notes
• Osmosis and water potential notes
• Finding the water potential of plant tissue notes
• Gas exchange surfaces and Fick's law notes
• How the lung is adapted for gas exchange notes

5 Proteins and DNA

• Enzymes: biological catalysts notes
• Active sites, specificity and induced fit notes
• Core practical 4: measuring the initial rate of an enzyme reaction notes
• Temperature, pH, enzyme and substrate concentration notes
• Nucleotides, DNA and RNA notes
• Semi-conservative DNA replication notes
• Meselson and Stahl: proving semi-conservative replication notes
• The genetic code notes
• Transcription: DNA to mRNA notes
• Translation: mRNA to polypeptide notes

6 Gene expression and genetics

• Gene mutations: substitution, insertion, deletion notes
• Genetic terms and monohybrid crosses notes
• Codominance and pedigree diagrams notes
• Sex linkage and red-green colour blindness notes
• Cystic fibrosis notes
• Genetic screening: carriers, PGD and prenatal tests notes
• The ethics of genetic screening notes

7 Cell structure

• Light and electron microscopes: magnification and resolution notes
• Magnification calculations and units notes
• Core practical 5: the graticule and drawing animal cells notes
• The ultrastructure of an animal cell notes
• What each organelle does notes
• Recognising organelles in electron micrographs notes
• Protein transport: rough ER to Golgi to the outside notes
• Prokaryotic cells notes
• From cells to organ systems notes

8 Mitosis, meiosis and reproduction

• The cell cycle notes
• The stages of mitosis notes
• Core practical 6: the root tip squash notes
• Calculating the mitotic index notes
• Meiosis: two divisions, four haploid cells notes
• Independent assortment and crossing over notes
• Loci and linked genes notes
• Sperm and egg: specialised gametes notes
• Fertilisation in mammals notes
• Fertilisation in flowering plants notes
• Investigating pollen tube growth notes

9 Development of organisms

• How cells become specialised notes
• Phenotype: genotype plus environment notes
• Epigenetics: methylation and histones notes
• Multiple alleles, polygenic inheritance and continuous variation notes
• One gene, more than one protein notes
• Stem cells: totipotent and pluripotent notes
• Using stem cells: society and decisions notes

10 Plant structure and function

• Cellulose and the plant cell wall notes
• Plant cell ultrastructure notes
• Xylem, phloem and sclerenchyma notes
• Plant fibres, starch and sustainability notes
• Core practical 7: plan diagrams of roots, stems and leaves notes
• Water, nitrate, calcium and magnesium notes
• Investigating plant mineral deficiencies notes
• Core practical 8: tensile strength of plant fibres notes
• Conditions for bacterial growth and plant antimicrobials notes
• Core practical 9: antimicrobial plants and aseptic technique notes
• From digitalis soup to three-phase trials notes

11 Classification

• Classifying living things notes
• What is a species? notes
• The three-domain system notes

12 Biodiversity and conservation

• Biodiversity and endemism notes
• Species richness and the heterozygosity index notes
• The index of diversity notes
• Niches and adaptations notes
• The Hardy-Weinberg equation notes
• Changing allele frequencies: mutation and natural selection notes
• Reproductive isolation and new species notes
• Conservation: zoos and seed banks notes

13 Practical Skills in Biology I

• Variables, controls and a fair test notes
• Planning an experiment for Unit 3 notes
• Accuracy, precision, validity and repeatability notes
• Significant figures, units and results tables notes
• Evaluating results and suggesting improvements notes
• Drawing and reading graphs notes
• Percentage change, ratios and rates notes
• Mean, range, standard deviation and error bars notes

14 Photosynthesis

• Photosynthesis: the overall reaction notes
• ATP: the immediate energy supply notes
• Chloroplast structure and function notes
• Absorption and action spectra notes
• Separating leaf pigments by chromatography notes
• The light-dependent reactions notes
• Cyclic and non-cyclic photophosphorylation notes
• The Calvin cycle notes
• What the plant makes from GALP notes
• Core practical 10: measuring the rate of photosynthesis notes
• Limiting factors: light, carbon dioxide, temperature and wavelength notes

15 Ecology

• Population, community, habitat and ecosystem notes
• Succession: from colonisation to climax notes
• Abiotic factors and population size notes
• Biotic factors: predation, competition and disease notes
• How the niche explains distribution and abundance notes
• Core practical 11: random sampling with quadrats notes
• Core practical 11: transects and abiotic measurements notes
• Null hypotheses and choosing a statistical test notes
• Spearman's rank correlation coefficient notes
• Student's t-test notes
• The chi-squared test notes

16 Environment and climate change

• Energy transfer between trophic levels notes
• Gross and net primary productivity notes
• The carbon cycle notes
• Using the carbon cycle to reduce atmospheric CO₂ notes
• The greenhouse effect and anthropogenic climate change notes
• Evidence for climate change: CO2 and temperature records notes
• Evidence for climate change: pollen in peat bogs and dendrochronology notes
• The climate debate: correlation, causation and who concludes notes
• Extrapolating data: climate models and their limitations notes
• How climate change affects plants and animals notes
• Temperature, enzymes and Q10 notes
• Core practical 12: temperature and the development of organisms notes
• Evolution: a change in allele frequency notes
• Allopatric and sympatric speciation notes

17 Microbiology

• Bacteria and viruses compared notes
• Lytic and latent infections notes
• The bacterial growth curve notes
• Calculating exponential growth and the growth rate constant notes
• Culturing microorganisms with aseptic technique notes
• Measuring growth: cell counts and dilution plating notes
• Measuring growth: turbidity and mass notes
• Core practical 13: growth of microorganisms in liquid culture notes
• How pathogens enter and how the body keeps them out notes
• Tuberculosis: how Mycobacterium tuberculosis causes disease notes
• HIV: how the virus infects and leads to AIDS notes

18 Immunity

• Non-specific responses: inflammation, lysozyme and interferon notes
• Phagocytosis notes
• Antigens, antibodies and antigen-presenting cells notes
• The specific response: B cells and antibodies notes
• The specific response: T helper, T killer and T memory cells notes
• Natural, artificial, active and passive immunity notes
• The evolutionary race between pathogens and hosts notes
• Antibiotics: bacteriostatic and bactericidal notes
• Core practical 14: the effect of antibiotics on bacteria notes
• Antibiotic resistance and hospital-acquired infections notes

19 Decomposition and forensics

• Microorganisms, decomposition and the carbon cycle notes
• Time of death: body temperature and rigor mortis notes
• Time of death: decomposition, succession and forensic entomology notes
• The polymerase chain reaction (PCR) notes
• Gel electrophoresis notes
• DNA profiling: identification and relationships notes

20 Cellular respiration

• Aerobic respiration: the overall reaction notes
• Glycolysis notes
• Anaerobic respiration and what happens to lactate notes
• The link reaction and the Krebs cycle notes
• Oxidative phosphorylation and chemiosmosis notes
• The respiratory quotient (RQ) notes
• Core practical 15: a redox indicator and respiration in yeast notes
• Core practical 16: the respirometer and RQ notes

21 Muscles, movement and the heart

• How muscles, tendons, ligaments and the skeleton produce movement notes
• The structure of a skeletal muscle fibre notes
• Fast and slow twitch muscle fibres notes
• The sliding filament theory notes
• The myogenic heartbeat: SAN, AVN, bundle of His notes
• Reading ECGs notes
• Negative and positive feedback notes
• Cardiac output notes
• Controlling heart rate: the cardiovascular control centre notes
• Controlling breathing: the ventilation centre notes
• Core practical 17: spirometer traces and exercise notes

22 Control of the internal environment

• How hormones switch genes on and off notes
• The gross and microscopic structure of the kidney notes
• Urea production and ultrafiltration notes
• Selective reabsorption in the proximal tubule notes
• The loop of Henle as a countercurrent multiplier notes
• ADH and the control of plasma concentration notes
• Homeostasis and thermoregulation during exercise notes

23 The nervous system and neurones

• Sensory, relay and motor neurones notes
• From stimulus to response notes
• The spinal reflex arc notes
• The resting potential notes
• The action potential notes
• How an impulse travels: local circuits and saltatory conduction notes
• How a synapse works notes
• How the pupil dilates and contracts notes
• How drugs affect nerve transmission notes
• How rods detect light notes
• Habituation notes

24 Coordination in animals and plants

• The regions of the human brain notes
• Nervous and hormonal coordination notes
• Imaging the brain: MRI, fMRI, PET and CT notes
• Brain chemicals: dopamine, serotonin and new drugs notes
• Plant responses: auxin and gibberellins notes
• Phytochrome and flowering notes
• Phytochrome, transcription and plant responses notes
• Core practical 18: amylase production in germinating cereal grains notes

25 Gene technology

• Producing recombinant DNA notes
• Getting recombinant DNA into cells notes
• Drugs from genetically modified organisms notes
• Microarrays and bioinformatics notes
• Genetically modified organisms: risks and benefits notes

26 Practical Skills in Biology II

• Planning an investigation for Unit 6 notes
• Controlling variables: saying exactly how notes
• Recording and analysing data: tables, logs and tests notes
• Limitations, improvements and extensions notes
• The Unit 5 pre-release article notes