Biology by Bradford
Dry lab
Separate the pigments
A paper chromatography bench: pencil line, leaf spot, solvent. Measure each band, work out Rf and name the pigments.
Photosynthetic pigmentsChromatography
Biology sims
Every bench, film, game and tool from the interactive guides, on one shelf. Tap a card to open the sim in its guide chapter; a card in more than one guide lists the others at the bottom, and Copy link on a card gives a class a link that opens that sim full screen.
Show
Course
Dry lab
Pondweed and the lamp
Count bubbles from a sprig or time floating leaf discs as you move the lamp, change the carbon dioxide or the temperature.
Limiting factorsRate of photosynthesis
Dry lab
Respirometer: seeds and dough
Germinating seeds over potassium hydroxide with a drop in a capillary, or yeast dough racing five sugars. Work out the rate.
Rate of respirationCell respiration
Dry lab
Catalase and hydrogen peroxide
Collect the oxygen from catalase breaking down peroxide in a gas syringe. Change temperature, pH, substrate or an inhibitor.
EnzymesRate of reaction
Dry lab
Wet wicks
Probes with wet cotton wicks in still air or a fan, water or ethanol, dry or humid air. Which cools most, and why?
Properties of waterCooling by evaporation
Find it in
IB A1.1 WaterDry lab
Getting DNA out
Pick a fruit and a method (mashing, detergent, salt, a warm bath, cold ethanol) and wind the DNA onto a stick. See what each step does to the yield.
Nucleic acidsDNA extraction
Find it in
IB A1.2 Nucleic acidsDry lab
Fats on the bench
Melting points of fats and oils in a capillary tube in a warming bath. Press when the first drop appears and when it clears.
LipidsSaturated and unsaturated fats
Find it in
IB B1.1 Carbohydrates and lipidsDry lab
The PCR and gel bench
Work a case through five stations: sample, PCR, gel, reading the bands and the verdict, with the chance of a false match.
DNA replicationPCR and gel electrophoresis
Find it in
IB D1.1 DNA replicationDry lab
Island finches
Dune finches with beak genes feed on seeds of different sizes. Set the islands and the food, run the generations and watch the beaks change.
EvolutionSpeciation
Find it in
IB A4.1 Evolution and speciationFilm
From light to sugar
A zoom from a plant to a thylakoid, then light caught, water split, oxygen out and carbon dioxide built into sugar.
Photosynthesis
Film
Follow one glucose
One glucose followed through a muscle cell, its carbon leaving as carbon dioxide and its energy passed to ATP. Cut the oxygen off and see.
Cell respiration
Film
The chain and the turbine
Electrons pump protons across a membrane and the protons turn ATP synthase. Mitochondrion or thylakoid; oxygen, light and a leak are switches.
Cell respirationPhotosynthesisATP synthase
Film
Engelmann's bacteria
The 1882 experiment: light split into colors falls on a green alga and oxygen-loving bacteria show where it works.
Action spectrum
Film
The carbon trail
One carbon atom followed from carbon dioxide in the air, into a leaf, into sugar and back out by respiration.
PhotosynthesisRespirationCarbon cycle
Find it in
IB C1.3 PhotosynthesisFilm
Respiration and photosynthesis on one map
Glycolysis, the Krebs cycle and the Calvin cycle on one tappable map: lines, cycles and where they meet.
Metabolic pathways
Film
Enzyme collisions
Enzymes and substrate meeting at random in solution: temperature, concentration and the active site.
Enzymes
Film
Water in a xylem vessel
Evaporation at the leaf pulls a column of water up a xylem vessel; hydrogen bonds hold it together and an air bubble breaks it.
Properties of waterTransport in plants
Find it in
IB A1.1 WaterFilm
The Goldilocks zone
Change the star and the planet's distance and size, and see which planets keep their water liquid.
WaterOrigins of life
Find it in
IB A1.1 WaterFilm
Hershey and Chase
The 1952 experiment with phages and radioactive labels that showed DNA is the genetic material.
Nucleic acidsEvidence for DNA
Find it in
IB A1.2 Nucleic acidsFilm
Natural selection
A population with variation meets a changing environment: who survives, who breeds, and what the next generation looks like.
Natural selection
Film
Speciation by splitting
One population, split by a river, becomes two species. Watch the differences build up and reproductive isolation arrive.
Speciation
Film
Building polymers
Small molecules joined by condensation with a water leaving at each link, then split again by hydrolysis.
Macromolecules
Film
A membrane that makes itself
Phospholipids in water arrange themselves into a bilayer, and the membrane behaves as a liquid, not a skin.
Membranes
Find it in
IB B1.1 Carbohydrates and lipidsFilm
Folding a protein
A chain of amino acids folds into the one shape its sequence sets, and heat or the wrong pH unfolds it.
ProteinsEnzymes
Find it in
IB B1.2 ProteinsFilm
Transcription
One gene copied into RNA: the polymerase, the template strand and the growing transcript.
Protein synthesis
Find it in
IB D1.2 Protein synthesisFilm
The ribosome
Translation as a film: tRNAs bring amino acids to the codons on mRNA and the chain grows.
Protein synthesis
Find it in
IB D1.2 Protein synthesisFilm
Diffusion across a membrane
Molecules crossing a membrane: concentration, permeability and what the membrane lets through.
MembranesTransport
Find it in
On the guides home pageGame
The ATP budget
Keep a muscle fiber running: respire each glucose the right way as the blood supply changes, and see where the ATP comes from.
Cell respirationATP
Game
The Rubisco race
Run a chloroplast's stroma: one Rubisco is hopeless, so make more until the stroma keeps up, then meet a hot day.
Calvin cycleRubisco
Game
Be the bird
Peppered moths on bark: you are the bird. Which moths do you find, and how does the next generation change?
Natural selection
Game
Run the fork
Be the replication machinery at one fork: unzip the helix, match the nucleotides and, at higher level, handle primers and mistakes.
DNA replication
Find it in
IB D1.1 DNA replicationGame
The protein factory
Make a protein from a gene: transcribe, translate and fix what the rules refuse, each refusal naming the rule.
Protein synthesis
Find it in
IB D1.2 Protein synthesisTool
The respiration map
The whole of respiration on one page: where each stage happens, what goes in and out, the totals and the ATP ledger.
Cell respiration
Tool
Water molecules
Water molecules tumbling in a box with hydrogen bonds forming and breaking, faster when hotter.
Properties of water
Find it in
IB A1.1 WaterTool
The bond builder
Join monomers by condensation, a water leaving at each bond, and split them again by hydrolysis.
MacromoleculesNucleic acidsProteins
Tool
Fold a protein
Type a name or a gene and watch the protein come off a ribosome and fold, then mutate it and fold the mutant beside it.
ProteinsProtein synthesis
Tool
Fold the chain
A puzzle: lay a chain of amino acids on a grid of water so the non-polar ones end up together inside.
Proteins
Find it in
On the guides home pageTool
The codon tool
The genetic code as a tool you can read and run: bases to codons to amino acids.
Protein synthesis
Find it in
IB D1.2 Protein synthesisFilm
ICE AGE
One population of ground beetles, one letter at a time: inherited variation, competition, an environmental pressure, adaptation, a genotype shift and, over generations, evolution.
Natural selection
Find it in
IB D4.1 Natural selectionGame
Run a population: ICE AGE
Set the pressure on a population of ground beetles and watch their jaw alleles answer back: drought, predator, cold snap, no variation, fed larvae and mate choice.
Natural selection
Find it in
IB D4.1 Natural selectionDry lab
Endler's guppies
A version of John Endler's guppy experiment: raise guppies in ponds with no predator, a weak one or a strong one, and watch how the number of spots on the males changes as predators and mate choice push against each other. The numbers are illustrative, not Endler's data.
Natural selectionSexual selectionEndler
Find it in
IB D4.1 Natural selectionFilm
Three kinds of selection
One population of finches, three kinds of selection: directional, stabilising and disruptive. Each changes the beak sizes in its own way, and each changes allele frequency.
Natural selectionAllele frequencies
Find it in
IB D4.1 Natural selectionTool
Hardy-Weinberg
Predict genotype frequencies from p and q, count a population against the prediction, switch off each Hardy-Weinberg condition to see what breaks, and work out carrier frequencies.
Allele frequenciesHardy-Weinberg
Find it in
IB D4.1 Natural selectionTool
Make a karyogram
Pair and order stained chromosomes into a karyogram, then weigh the evidence that human chromosome 2 formed from two ape chromosomes.
ChromosomesKaryotypes
Find it in
IB A3.1 Diversity of organismsTool
Build a key
Build a dichotomous key for eight invertebrates and test it by sending every card through, then use a given key on new specimens.
ClassificationDichotomous keys
Find it in
IB A3.1 Diversity of organismsDry lab
Genome size and complexity
Look up genome sizes and gene counts for twenty organisms, plot them on a log scale, and test whether complexity predicts genome size.
GenomesGenome size
Find it in
IB A3.1 Diversity of organismsFilm
Barcodes from pond water
From a bottle of pond water to a species list: filter, extract, PCR, sequence and match barcodes, finding a newt nobody saw.
BiodiversityDNA barcodes
Find it in
IB A3.1 Diversity of organismsTool
Build a cladogram
Join made-up beetles into a cladogram, mark where each trait changes, and check it against the tree with the fewest changes; or read a vertebrate cladogram for clades, nodes and closest relatives.
CladisticsCladograms
Find it in
IB A3.2 Classification and cladisticsFilm
The molecular clock
Two pairs of species collect mutations; a dated fossil calibrates the molecular clock, which then dates the other split. Change generation time, mutation rate, population size or selection and the estimate moves.
CladisticsMolecular clock
Find it in
IB A3.2 Classification and cladisticsFilm
Three domains
Woese compares ribosomal RNA: archaea differ from bacteria, and the tree of life splits into three domains, Archaea nearer to Eukarya.
ClassificationDomains
Find it in
IB A3.2 Classification and cladisticsDry lab
Grow a tree
Score all 105 possible trees for six made-up fish by parsimony, then see how adding traits, DNA or a different rule for counting changes moves the winner.
CladisticsParsimony
Find it in
IB A3.2 Classification and cladisticsTool
Make a cross
Choose two parents, predict the ratio, fill the Punnett grid, then breed batches of 30 and watch the counts scatter around the expectation. One gene, two genes (HL) or sex-linked.
InheritancePunnett grids
Find it in
IB D3.2 InheritanceTool
Read a family tree
Three made-up families: test autosomal and X-linked, dominant and recessive against each tree, see who rules each one out, then deduce genotypes and carriers.
InheritancePedigrees
Find it in
IB D3.2 InheritanceTool
Build a box plot
Drag 25 students' heights and watch the median, quartiles, IQR and 1.5 x IQR outlier fences move the box and whiskers; or type in your own data.
Continuous variationBox plots
Find it in
IB D3.2 InheritanceDry lab
Fly crosses: linked or not?
Cross flies carrying two invented genes, count each brood's offspring and use a chi-squared test to decide whether the genes assort independently or are linked; then try the mystery pairs.
Dihybrid crossesGene linkageChi-squared test
Find it in
IB D3.2 InheritanceFilm
Halve, then fuse
One cell makes four different haploid gametes through crossing over, a random line-up and two divisions, then a gamete fuses with another into a diploid zygote. At HL, follow two genes into the gametes and count the ratio.
MeiosisInheritanceDihybrid crossesGene linkage
Find it in
IB D3.2 InheritanceNothing on the shelf matches. Try a different word, Both courses or All.