General Biology

Units

1. 1

   Chemistry of life

   8 lessons

   1. Water and hydrogen bondingExplain how the polarity of water makes hydrogen bonds between molecules, and use them to account for cohesion, adhesion, surface tension, floating ice, high specific heat and evaporative cooling.
   2. Elements of life: C, H, N, O, P, SSay which of C, H, N, O, P and S build each class of biological molecule, explain why carbon makes such varied skeletons, and use the elements to choose a radioactive label.
   3. Dehydration synthesis and hydrolysisDescribe how dehydration synthesis joins monomers into polymers and hydrolysis cuts them, count the water molecules for a chain of n monomers, and balance the atoms of a reaction.
   4. CarbohydratesDescribe monosaccharides, disaccharides and polysaccharides, explain how branching and linkage give starch, glycogen, cellulose and chitin their functions, and read enzyme data on them.
   5. LipidsDescribe fats, phospholipids and steroids, explain why saturation changes how fats pack and melt, and explain why phospholipids form a bilayer in water.
   6. Nucleic acids: structure and directionalityDescribe a nucleotide and the 5' and 3' ends of a strand, build the antiparallel double helix with A-T and G-C pairs, write a complementary strand, and tell DNA from RNA.
   7. Amino acids and primary structureDescribe the structure of an amino acid and its R-group classes, explain the peptide bond and the direction of a polypeptide, and show how a change in the sequence can change a protein.
   8. Protein folding: secondary to quaternary structureName the interaction that holds each level of protein structure, say which proteins have quaternary structure, and explain denaturation from the weak interactions it breaks.
2. 2

   Cell structure and function

   13 lessons

   1. Ribosomes and the endomembrane systemExplain how ribosomes, the rough and smooth ER, the Golgi complex, vesicles and lysosomes work together to make, fold, modify and deliver proteins, and trace a protein's route from pulse-chase data.
   2. Mitochondria, chloroplasts, vacuoles and the cytoskeletonExplain how the structure of mitochondria, chloroplasts, vacuoles and lysosomes fits their jobs, and use membrane area and organelle counts to argue what a cell does.
   3. Surface area to volume ratioCalculate surface area to volume ratios (SA:V) with the AP formulas, show that the ratio falls as an object grows, and use it to explain why cells stay small, flat or folded.
   4. The fluid mosaic membraneDescribe how phospholipids and proteins are arranged in the plasma membrane, name the role of each component, and use the fluid mosaic model to interpret fusion and temperature data.
   5. Selective permeability and the cell wallExplain, with the hydrophobic interior of the bilayer, which molecules cross a membrane freely, slowly or only with a protein, and separate the cell wall from the plasma membrane.
   6. Passive and active transportExplain diffusion and dynamic equilibrium, separate passive from active transport by whether the cell spends direct energy, and read rate and uptake data to tell the types apart.
   7. Facilitated diffusion: channels, carriers and aquaporinsExplain why ions and polar molecules cross membranes through channel, carrier and aquaporin proteins without energy, separate these from pumps, and read a rate graph that levels off.
   8. Tonicity and osmosisPredict the direction of water movement between a cell and its surroundings from their solute concentrations, say how animal and plant cells respond, and use potato-core data to find the isotonic concentration.
   9. Water potential calculationsCalculate solute potential with ψS = −iCRT and water potential with ψ = ψP + ψS, and use the values to predict which way water moves.
   10. Active transport and the sodium-potassium pumpExplain that active transport moves a substance against its gradient using ATP and a membrane protein, describe the Na⁺/K⁺ pump and the gradients it builds, and interpret uptake data with and without a metabolic inhibitor.
   11. Endocytosis and exocytosisDescribe how a cell takes in large cargo by endocytosis in three forms and releases cargo by exocytosis, explain why both need energy and vesicles, and explain how a cell keeps its surface area steady.
   12. Why cells are compartmentalizedDescribe how membranes and organelles compartmentalize a eukaryotic cell, explain how internal membranes separate reactions, add surface area and concentrate reactants, and weigh these benefits against the costs.
   13. Origins of cell compartmentalization: endosymbiosisState the endosymbiotic theory, support it with evidence from organelles and data, and compare compartmentalization in prokaryotic and eukaryotic cells.
3. 3

   Cellular energetics

   10 lessons

   1. Enzyme structure and catalysisExplain how an enzyme lowers activation energy through its active site without changing the energy difference between reactants and products, and calculate an initial rate from a time course.
   2. Temperature, pH and inhibitors: reading enzyme dataExplain how temperature, pH, substrate and enzyme concentration and inhibitors change an enzyme's rate, read the graph of each, and tell a competitive inhibitor from a noncompetitive one by its plateau.
   3. ATP, energy coupling and thermodynamicsExplain how living cells stay ordered without breaking the laws of thermodynamics, how ATP hydrolysis is coupled to energy-requiring reactions, and why conserved metabolic pathways point to common ancestry.
   4. Light-dependent reactionsDescribe where the light reactions happen in the chloroplast, trace the electrons from water to NADPH and the protons that make ATP at ATP synthase, and use labelling, spectrum and dye data as evidence.
   5. The Calvin cycleDescribe the three stages of the Calvin cycle in the stroma, count the CO₂, ATP and NADPH needed for G3P and glucose, explain why the cycle stops without the light reactions, and say where the carbon goes.
   6. Photosynthesis experiments and dataDesign a photosynthesis investigation with variables and controls, calculate a rate, compare means using error bars, and calculate Rf from a pigment chromatogram.
   7. Glycolysis and pyruvate oxidationState where glycolysis and pyruvate oxidation happen, what goes in and comes out of each, and follow the six carbons of glucose to pyruvate, acetyl groups and CO₂.
   8. The Krebs cycleDescribe where the Krebs cycle happens, what one turn and one glucose produce, why its main output is reduced carriers and not ATP, and why it stops without oxygen.
   9. Electron transport and chemiosmosisExplain how electrons passed down the chain build a proton gradient across the inner mitochondrial membrane, how ATP synthase uses the gradient to make ATP, and how oxygen, inhibitors and uncouplers change the result.
   10. Fermentation and comparing ATP yieldsExplain why fermentation lets glycolysis continue without oxygen, name the two types and their products, compare ATP yields, and calculate and compare respiration rates measured with a respirometer.
4. 4

   Cell communication and cell cycle

   8 lessons

   1. Types of cell signallingDescribe how cells communicate by contact and by chemical signals over short and long distances, and explain why only cells that have the right receptor respond.
   2. Receptors and signal transductionDescribe the components of a signal transduction pathway, say what each does, and explain how a cascade amplifies a signal and is switched off.
   3. Second messengers and cellular responsesFollow the epinephrine pathway from receptor to glucose, explain how enzymes end a second-messenger signal, and describe responses that change gene expression or end in apoptosis.
   4. When pathways change: mutations and drugsPredict how a mutation or a drug at one step changes a signalling pathway, name it as loss of function, gain of function, agonist, antagonist or inhibitor, and use mutant experiments to place a defect.
   5. Positive and negative feedbackExplain how negative feedback keeps a variable near a set point and how positive feedback amplifies a change to an endpoint, name the parts of a loop, and identify the type from a graph.
   6. Interphase and the cell cycleDescribe what happens in G1, S, G2 and G0, count chromosomes, chromatids and DNA content through the cycle, and calculate the time a cell spends in each phase from cell counts.
   7. Mitosis and cytokinesisDescribe the stages of mitosis and cytokinesis, state the chromosome and DNA counts in the daughter cells, and use cell counts to estimate the time in each phase and the mitotic index.
   8. Regulation of the cell cycle: checkpoints, cyclins and cancerDescribe the three checkpoints and how cyclins and Cdks drive the cycle, and predict how mutations in proto-oncogenes and tumor suppressors lead to cancer or apoptosis.
5. 5

   Heredity

   10 lessons

   1. MeiosisExplain how one round of DNA copying and two divisions turn a diploid cell into four haploid cells, count chromosomes and chromatids at each stage, and compare meiosis with mitosis.
   2. Crossing over and independent assortmentExplain how crossing over, independent assortment and random fertilization shuffle alleles, calculate the number of gamete and zygote combinations, and pose a testable question about recombination.
   3. Nondisjunction and chromosomal disordersExplain how nondisjunction in meiosis I or II gives gametes with the wrong chromosome number, predict the zygotes they make, read a karyotype, and say why most Down syndrome is not inherited.
   4. Monohybrid and dihybrid crossesUse Mendel's laws and Punnett squares to predict genotypic and phenotypic ratios of monohybrid and dihybrid crosses, find expected counts, and use a test cross to reveal an unknown genotype.
   5. Probability rules in geneticsUse the product rule for independent events and the sum rule for mutually exclusive events to find the chance of genotypes and phenotypes, solve many-gene crosses one gene at a time, and explain why past children do not change the next chance.
   6. The chi-square testState a null hypothesis for a genetic cross, calculate expected counts and chi-square from observed counts, and decide whether to reject the null using degrees of freedom and the critical value.
   7. Linked genes and recombination frequencyShow that a test cross of linked genes departs from 1 : 1 : 1 : 1, identify parental and recombinant classes, calculate recombination frequency as map distance, and order genes on a map.
   8. Sex-linked traits and pedigreesPredict the children of X-linked crosses, explain why X-linked recessive traits are more common in males, read a pedigree to infer its mode of inheritance, and compare XY, ZW and haplodiploid sex systems.
   9. Incomplete dominance, codominance, pleiotropy and non-nuclear inheritanceTell incomplete dominance from codominance from the heterozygote and the ratios, work ABO blood-type crosses with three alleles, separate pleiotropy from polygenic traits, and explain maternal inheritance of mitochondrial genes.
   10. Environmental effects on phenotypeExplain how one genotype can give different phenotypes in different environments, interpret an experiment on genetically identical organisms with error bars, and separate plasticity from inheritance, evolution and heritability.
6. 6

   Gene expression and regulation

   10 lessons

   1. DNA and RNA structureDescribe how DNA and RNA store hereditary information, how chromosomes and plasmids package it, why base pairing makes DNA a good genetic material, and which experiments showed that DNA carries heredity.
   2. DNA replication: leading and lagging strandsExplain why replication is semiconservative using the Meselson-Stahl data, say what each enzyme at the fork does, and use the 5' to 3' rule to explain leading and lagging strands and the effect of a missing enzyme.
   3. Transcription and RNA processingExplain how RNA polymerase copies one template strand into RNA, 5' to 3', write the mRNA and the coding strand for a template, and describe how a eukaryotic pre-mRNA is capped, tailed and spliced, including alternative splicing.
   4. Translation and the genetic codeRead an mRNA in codons with the genetic code chart, describe initiation, elongation and termination on the ribosome with codon-anticodon pairing, and explain why the universal code is evidence of common ancestry and how retroviruses add reverse transcription.
   5. Operons in prokaryotesDescribe an operon as a promoter, an operator and structural genes under one control, explain why the lac operon is inducible and the trp operon repressible, and predict expression from the glucose and lactose supply and from mutants.
   6. Eukaryotic gene regulationExplain how enhancers, promoters and transcription factors control transcription, how methylation, acetylation and small RNAs change expression without changing the sequence, and predict the effect of a change in a regulatory element.
   7. Gene expression and cell specializationExplain that cells of one organism share a genome and differ by which genes they express, read expression data to support that claim, and predict what a break in a transcription factor cascade does to differentiation.
   8. Mutations and genetic variationClassify point mutations and frameshifts from a codon chart, explain how a change in genotype becomes a change in phenotype that selection can act on, and name the sources of variation in prokaryotes and chromosomes.
   9. PCR and gel electrophoresisExplain the three steps of a PCR cycle and why copies double, calculate copy number as 2 to the power n, explain how a gel sorts DNA by size and charge, and read a gel with a ladder.
   10. Sequencing, cloning and CRISPRExplain how a gene is cut, joined into a plasmid and put into bacteria, design and read the controls of a transformation experiment, calculate transformation efficiency, and describe sequencing and CRISPR-Cas9 editing.
7. 7

   Natural selection

   14 lessons

   1. Natural selectionName the conditions for natural selection, explain a population's change with variation, heredity and differential reproduction, define fitness as reproductive success, and calculate a percent change in a trait mean.
   2. Selection on phenotypes in changing environmentsExplain that selection acts on phenotypes and changes allele frequencies, tell directional, stabilizing and disruptive selection apart, and use fitness data to explain why a harmful allele can persist.
   3. Artificial selectionExplain that artificial selection is natural selection with humans as the selective agent, calculate the response to selection from generation data, and explain how it reduces genetic diversity.
   4. Population genetics: drift, bottlenecks, gene flowExplain how mutation, genetic drift, bottleneck and founder effects and gene flow change allele frequencies, calculate allele frequencies after a bottleneck, and classify a change as chance or selection.
   5. The Hardy-Weinberg equationsState the two Hardy-Weinberg equations and their five conditions, calculate allele and genotype frequencies from the frequency of a recessive phenotype, and explain why the model is a null hypothesis and not a claim that populations are static.
   6. Testing for evolution with Hardy-Weinberg dataState the Hardy-Weinberg null hypothesis, calculate p, q, expected genotype counts and chi-square from observed counts, decide with 1 degree of freedom, and identify which condition fails when the null is rejected.
   7. Evidence of evolutionDescribe the kinds of data that support evolution, calculate a fossil's age from carbon-14, tell homologous from analogous structures, and interpret sequence differences as evidence of common ancestry.
   8. Common ancestryDescribe the structural and molecular features that all eukaryotes, and all life, share, explain why shared features indicate common ancestry, and predict the features of a newly found organism.
   9. Continuing evolution: resistance and emerging diseaseExplain how resistance to antibiotics, pesticides and drugs evolves by natural selection, calculate how the resistant share of a population rises, and design a test of resistance evolution.
   10. Reading phylogenetic treesName the parts of a phylogenetic tree, read relatedness from nodes and not from the order of tips, and say what a cladogram shows and what a scaled tree adds.
   11. Building a cladogram from dataBuild a cladogram from a table of traits using an outgroup and shared derived traits, build a tree from DNA differences, and estimate divergence time with a molecular clock.
   12. Speciation and reproductive isolationApply the biological species concept, classify reproductive barriers as pre-zygotic or post-zygotic by timing, contrast allopatric and sympatric speciation, and describe the tempo and pattern of evolution.
   13. Variation, extinction and survivalExplain why genetic diversity makes a population resilient, calculate how a bottleneck lowers expected heterozygosity, and justify that an allele's value depends on the environment.
   14. Origins of life on EarthUse geological dates to bound the origin of life, state what the Miller-Urey experiment did and did not show, and evaluate the RNA world hypothesis and its assumptions.
8. 8

   Ecology

   11 lessons

   1. Behavioural and physiological responsesClassify a response as kinesis, taxis, a physiological change or a signal, explain how responses and cooperation raise fitness, and test a choice experiment with chi-square.
   2. Energy flow through ecosystemsPlace organisms in a food web with arrows from eaten to eater, calculate net primary productivity and the energy reaching each trophic level, and predict how a loss of producer energy changes every level.
   3. Biogeochemical cyclesName the levels of ecological organization, explain why matter cycles while energy flows, and trace water, carbon, nitrogen and phosphorus through their reservoirs, with the microbes that run them.
   4. Population growth and exponential growthCalculate the change in a population from births and deaths, find the per capita growth rate, recognize exponential growth as a J-shaped curve, and explain why it cannot last.
   5. Population ecology dataCalculate survivorship from a life table, classify survivorship curves and age structures, and connect them to r-selected and K-selected life histories.
   6. Logistic growth and carrying capacityExplain carrying capacity and the S-shaped logistic curve, substitute into dN/dt = r_max N (K − N)/K, find where growth is fastest, and interpret what happens above K.
   7. Density-dependent and independent factorsSort limiting factors by whether their effect changes with crowding, explain how density-dependent factors hold a population near carrying capacity as negative feedback, and read birth rate, death rate and survival data.
   8. Community interactions and Simpson's diversity indexDescribe a community by its species composition, richness and evenness, calculate Simpson's diversity index, and explain how competition, predation, symbioses and niche partitioning shape which species live together.
   9. Biodiversity and ecosystem resilienceExplain how keystone species and trophic cascades hold an ecosystem together, use grassland data to show that diversity buffers an ecosystem against disruption, and predict the short-term and long-term effects of removing a component.
   10. Disruptions to ecosystems: adaptation and invasive speciesExplain that a disruption selects among variation that already exists and does not direct mutation, show how heterozygote advantage keeps two alleles in a population, and use data and error bars to judge whether an invasive species harms natives.
   11. Disruptions to ecosystems: human impact and geological eventsCalculate and explain biomagnification, trace the chain of eutrophication from nutrient runoff to a dead zone, and sort ecosystem disruptions into human and natural causes, including climate change.