95 IB Biology IA ideas and Extended Essay topics

Leaf thickness along a light gradient

Two leaves of one species, one from full sun and one from deep shade, can be built very differently. Put a number on how.

SL ●●●HL ●●●Fieldwork

B4.1 Adaptation to environmentC1.3 Photosynthesis

Also works as an EEFull guide

Do plants really ignore green light?

Plants look green, so is green light wasted? Test it fairly, with the same number of photons in every colour.

SL ●●●HL ●●●Lab

C1.3 Photosynthesis

Also works as an EEFull guide

Plants that bend toward blue

Shine a light from one side and a seedling leans toward it. Change the colour and see who notices.

SL ●●●HL ●●●Lab

C2.1 Chemical signalling HLC2.2 Neural signalling

Also works as an EEFull guide

Stomata: sun leaves versus shade leaves

Count the pores a leaf breathes through, and find out whether light changes how many it grows.

SL ●●●HL ●●●Fieldwork + Lab

B3.1 Gas exchangeB4.1 Adaptation to environment

Also works as an EEFull guide

Transpiration and the air's real drying power

Relative humidity is a poor measure of how thirsty the air is. Test a better one, vapour pressure deficit.

SL ●●●HL ●●●Lab

B3.2 Transport in organismsD2.3 Water potential

Also works as an EEFull guide

One bad banana: ethylene and ripening

A ripe fruit speeds up the ripening of its neighbours. How strong is that effect, and how far does it carry?

SL ●●●HL ●●●Lab

C2.1 Chemical signalling HLC1.2 Cell respiration

Also works as an EE

How green is old? Chlorophyll along a stem

Leaves lose their green as they age. Measure how fast, from the tip of a stem to its base.

SL ●●●HL ●●●Lab

C1.3 PhotosynthesisB4.1 Adaptation to environment

Also works as an EE

Can a plant learn? Mimosa and the dropping test

A touch-sensitive plant folds its leaves when dropped. Drop it enough times and it may stop reacting.

SL ●●●HL ●●●Lab

C2.2 Neural signallingTI Tools and inquiry

How sweet should the pollen's bath be?

A pollen grain grows a tube when it lands in the right place. In a dish, it needs the right sugar level.

SL ●●●HL ●●●Lab

D3.1 ReproductionD2.3 Water potential

Also works as an EEFree full card

Pondweed and light: make the classic your own

Everyone counts bubbles from pondweed. Test whether the inverse-square law or something else sets the rate.

SL ●●●HL ●●●Lab

C1.3 Photosynthesis

Overused: needs a twist

How fast does a root find 'down'?

Turn a seedling on its side and its root curves back to the vertical. Time the turn, then change the starting angle.

SL ●●●HL ●●●Lab

C2.1 Chemical signalling HL

Also works as an EE

Enzyme beads: does size matter?

Trap an enzyme in a bead, then test whether bigger beads work more slowly. Diffusion will explain why.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolismA1.2 Nucleic acids

Also works as an EEFull guide

Does maltose slow down the enzyme that makes it?

Products can fight back against the enzyme that made them. Find out whether maltose slows down amylase.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolism

Also works as an EEFull guide

Pineapple versus jelly: how much heat can bromelain take?

Fresh pineapple stops jelly from setting. Tinned pineapple does not. Find the temperature at which the enzyme gives up.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolismB1.2 Proteins

Also works as an EE

Catalase and temperature: the classic, made your own

Every class does catalase and temperature. Go beyond 'it peaks then dies' and model how the enzyme actually loses activity.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolism

Overused: needs a twist

Seeds waking up: when does amylase switch on?

A dry seed holds starch. When it germinates it must unlock it. Measure when and how fast.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolismD3.1 Reproduction

Also works as an EE

Lactase in a bottle: find its Km

A lactose-free milk enzyme works faster with more lactose, but only up to a point. Find where the curve flattens.

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolismB1.1 Carbohydrates and lipids

Also works as an EE

Brown apples: what slows the colour change?

Cut apples go brown because an enzyme meets oxygen. Which kitchen chemical stops it best, and how much do you need?

SL ●●●HL ●●●Lab

C1.1 Enzymes and metabolismB1.1 Carbohydrates and lipids

Also works as an EE

Yeast and sugar: what is on the menu and how much?

Yeast turns sugars into carbon dioxide, but not equally fast. Compare sugars and find where too much starts to hurt.

SL ●●●HL ●●●Lab

C1.2 Cell respirationD2.3 Water potential

Free full card

Garlic versus bacteria: dose and response

Plant extracts are said to kill bacteria. Put a dose on the effect and see where it stops.

SL ●●●HL ●●●Lab

C3.2 Defence against diseaseB1.1 Carbohydrates and lipids

Overused: needs a twist

Rising dough: how much salt is too much?

Salt flavours bread and also slows the yeast. Find out how much it takes to stall the rise.

SL ●●●HL ●●●Lab

C1.2 Cell respirationD2.3 Water potential

Free full card

Yeast growth curve: where does the lag phase end?

A tiny yeast sample in sugar water seems to do nothing, then explodes. Find the pattern and what shifts it.

SL ●●●HL ●●●Lab + Modelling

C4.1 Populations and communitiesC1.2 Cell respiration

Also works as an EE

Yoghurt: how warm is best?

Milk turns to yoghurt when bacteria make acid. How does the temperature change how fast it happens?

SL ●●●HL ●●●Lab

C1.2 Cell respirationB1.1 Carbohydrates and lipids

Practice and reaction time

Does a simple reaction test get better with practice? Turn a falling ruler into numbers and see whether the nervous system learns.

SL ●●●HL ●●●Lab

C2.2 Neural signallingC3.1 Integration of body systems

Full guide

Squeeze until it fades: modelling muscle fatigue

A strong squeeze cannot last. How fast does force fall, and does rest bring it back?

SL ●●●HL ●●●Lab + Modelling

B3.3 Muscle and movement HLC1.2 Cell respirationTI

Also works as an EE

How quickly does your heart settle after a climb?

A fitter heart returns to rest faster. How long is the recovery, and what does it depend on?

SL ●●●HL ●●●Lab

C3.1 Integration of body systemsD3.3 HomeostasisB3.2

Lung power and height: what does a class dataset show?

Taller people have bigger lungs. How tight is the link, and does age or sex matter?

SL ●●●HL ●●●Lab + Database

B3.1 Gas exchangeD3.3 Homeostasis

Also works as an EE

Can a phone camera count your pulse?

A phone flash can detect blood flow in a fingertip. How accurate is it against a pulse count?

SL ●●●HL ●●●Lab

B3.2 Transport in organismsC3.1 Integration of body systemsTI

Step tempo and heart rate: how fast must you go?

A metronome sets how quickly someone steps up and down. How does pulse follow the pace?

SL ●●●HL ●●●Lab

B3.2 Transport in organismsC3.1 Integration of body systems

A map of touch: how sharp is your skin?

Two nearby touches feel like one until they are far enough apart. Map that distance across the body.

SL ●●●HL ●●●Lab

C2.2 Neural signallingB2.3 Cell specialisation

Seeing in the dim: acuity against light level

Your eyes adapt, but only so far. Measure how fine a detail you can resolve as the room darkens.

SL ●●●HL ●●●Lab

C2.2 Neural signallingC3.1 Integration of body systems

Free full card

Duckweed: how fast does a population really grow?

A few tiny fronds turn into a green carpet in two weeks, then stop. Find out how hungry it is.

SL ●●●HL ●●●Lab + Modelling

C4.1 Populations and communitiesC4.2 Energy and matter transfers

Also works as an EEFull guide

Does mowing change what grows?

A lawn looks boring until you count it. How often it is cut decides who survives, and you can measure that.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communities

Also works as an EEFull guide

Species and area on a school field

Bigger areas hold more species. Find out by how much, and fit a number to it.

SL ●●●HL ●●●Fieldwork + Modelling

C4.1 Populations and communitiesA3.1 Diversity of organisms

Also works as an EEFull guide

Tea bags: how much soil moisture do decomposers need?

Bury a tea bag and come back in weeks. The soil has eaten part of it; the missing mass is your data.

SL ●●●HL ●●●Fieldwork

C4.2 Energy and matter transfersD4.2 Stability and change

Also works as an EEFull guide

Life in the leaf litter: depth and diversity

A handful of leaf litter hides a whole community. How does the depth of the litter change who lives there?

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communitiesA3.1

Also works as an EE

Where the sea leaves off: zonation on a rocky shore

Barnacles and limpets sort themselves by height up a shore. Measure the pattern and explain it.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communities

Also works as an EE

Do seedlings avoid their parents?

Seedlings under a parent tree may suffer from pests that target that species. Count them with distance.

SL ●●●HL ●●●Fieldwork

C4.1 Populations and communitiesB4.2 Ecological niches

Also works as an EE

Does soil pH set what grows?

Some plants love acid soil, others hate it. Sample a natural pH gradient and see how many species it supports.

SL ●●●HL ●●●Fieldwork + Lab

B4.2 Ecological nichesC4.1 Populations and communities

Also works as an EE

Walking the line: trampling and plant cover

A path across the grass shows a clear border. Measure how plants change as you move away from the track.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communities

Also works as an EEFree full card

Beetroot and freeze-thaw

Not another temperature test. Count how many freeze-thaw cycles beetroot membranes can take before they give up their pigment.

SL ●●●HL ●●●Lab

B2.1 Membranes and transportA1.1 Water

Also works as an EEFull guide

Capillary rise: can xylem lift a tree by itself?

Water climbs a narrow tube with nothing pushing it. How high does it go, and is that enough for a 100 m tree?

SL ●●●HL ●●●Lab + Database

B3.2 Transport in organismsA1.1 WaterD2.3

Also works as an EEFull guide

How far does a molecule diffuse in a gel?

Why can't a cell be the size of a football? A blob of dye in jelly gives a first answer.

SL ●●●HL ●●●Lab

B2.1 Membranes and transportA1.1 Water

Also works as an EEFull guide

Potato cores: does salt or sugar pull more water?

Same concentration of salt and sugar. Does the potato care? Predict where each one balances, then test it.

SL ●●●HL ●●●Lab

D2.3 Water potentialB2.1 Membranes and transport

Overused: needs a twistFull guide

Seeing water leave the cell: plasmolysis in onion

Under the microscope, cells shrink away from their walls in strong sugar. Find the concentration at which half have started to give.

SL ●●●HL ●●●Lab

D2.3 Water potentialB2.1 Membranes and transportA2.2

Free full card

How fast does a dry seed drink?

A dry bean swells in water. How quickly, and how much does the temperature of the water change the speed?

SL ●●●HL ●●●Lab

D2.3 Water potentialD3.1 ReproductionB2.1

Also works as an EE

Does a longer stem slow the flow?

Water pushed through a cut stem meets resistance. Test whether it follows the same rule as flow through a tube.

SL ●●●HL ●●●Lab

B3.2 Transport in organismsA1.1 Water

Also works as an EE

Corn ear: does counting more kernels change the 3 : 1?

Mendel's 3 : 1 shows up on a cob, but only if you count enough kernels. How many is enough?

SL ●●●HL ●●●Lab + Modelling

D3.2 InheritanceTI Tools and inquiry

Also works as an EEFull guide

Build a tree from protein sequences

Fossils and anatomy give one family tree; protein sequences give another. Do they agree?

SL ●●●HL ●●●Database

A3.2 Classification and cladistics HLA4.1 Evolution and speciationD4.1

Also works as an EEFull guide

Does heat-loving mean GC-rich?

G-C pairs have three hydrogen bonds, A-T pairs only two. Do microbes that live in hot springs pack in more G and C?

SL ●●●HL ●●●Database

A1.2 Nucleic acidsD1.1 DNA replicationA3.1

Also works as an EEFull guide

How often does a mutation change a protein?

Change one letter of a gene and the protein may not notice, may swap one amino acid, or may stop dead. Count how often.

SL ●●●HL ●●●Database + Modelling

D1.3 Mutation and gene editingD1.2 Protein synthesisA1.2

Also works as an EEFull guide

Do heat-loving proteins have more charged residues?

Enzymes from hot springs survive where yours would unravel. Is there something on the inside that you can count?

SL ●●●HL ●●●Database

B1.2 ProteinsC1.1 Enzymes and metabolism

Also works as an EEFull guide

Is the active site the most conserved part?

Evolution lets the surface drift but guards the working core. Test it residue by residue.

SL ●●●HL ●●●Database

B1.2 ProteinsC1.1 Enzymes and metabolismA3.2 HL

Also works as an EE

Is a human gene pool in balance? Hardy-Weinberg on real data

A neutral gene should follow simple rules in a big mixing population. Test whether real SNPs do.

SL ●●●HL ●●●Database

D3.2 InheritanceD4.1 Natural selectionD4.2

Also works as an EE

Who can drink milk? Lactase persistence across populations

The ability to digest lactose in adults is a recent human adaptation. Does its frequency follow a dairy culture?

SL ●●●HL ●●●Database

D4.1 Natural selectionD3.2 InheritanceB1.1

Also works as an EE

Sickle cell and malaria: does the map agree?

A harmful allele can persist if it protects against something worse. Test whether it follows malaria across the world.

SL ●●●HL ●●●Database

D4.1 Natural selectionD3.2 InheritanceC3.2

Also works as an EEFree full card

Crossing over in a fungus: does temperature change it?

A fungus keeps its spores in order after meiosis. The order shows whether chromosomes crossed over.

SL ●●●HL ●●●Lab

D2.1 Cell and nuclear divisionD3.1 ReproductionD3.2

Also works as an EE

How fast do ants run on a hot path?

Ants are cold-blooded, so speed depends on how warm the ground is. Watch a trail and time them.

SL ●●●HL ●●●Fieldwork

B4.1 Adaptation to environmentC1.2 Cell respiration

Also works as an EE

Counting crickets: does the song follow the weather?

Cricket songs speed up as the evening warms. How well does a simple rule predict the temperature?

SL ●●●HL ●●●Fieldwork + Database

B4.1 Adaptation to environmentC2.2 Neural signallingD3.3

Also works as an EE

Water fleas in the light: which way do they swim?

Water fleas swim toward or away from light. Measure the response across a range of brightness, gently.

SL ●●●HL ●●●Lab

C2.2 Neural signallingB4.1 Adaptation to environment

Why do bees choose that patch?

Pollinators visit some flower patches far more than others. Count visits and test what matters.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communitiesD3.1

Also works as an EEFree full card

Woodlice and damp: how strong is the pull?

Woodlice crowd into damp spots. How much does a small change in humidity shift their choice?

SL ●●●HL ●●●Lab

B4.1 Adaptation to environmentC2.2 Neural signalling

Overused: needs a twist

Acid rain and young plants: where does damage begin?

Rain can be acidic. Water seedlings with acid solutions to find the pH at which growth suffers.

SL ●●●HL ●●●Lab

D4.2 Stability and changeD4.3 Climate changeB2.1

Overused: needs a twist

Green water: how much nitrate does an algal bloom need?

Fertiliser runoff can feed blooms in ponds. Grow algae at different nutrient levels and measure the response.

SL ●●●HL ●●●Lab

C4.2 Energy and matter transfersD4.2 Stability and changeC4.1

Also works as an EE

Warm water, less oxygen: what do river records show?

Warmer water holds less dissolved oxygen. Test the link on real river monitoring data.

SL ●●●HL ●●●Database

D4.3 Climate changeC4.2 Energy and matter transfersA1.1

Also works as an EE

Dust on the leaves: how far does traffic reach?

Leaves catch particles from the air. Wash them and weigh what comes off to map pollution from a road.

SL ●●●HL ●●●Fieldwork + Lab

D4.2 Stability and changeC4.2 Energy and matter transfers

Also works as an EE

Lichens as air-quality sensors: what happens by the road?

Lichens are sensitive to air pollution. Measure how they change with distance from a busy road.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesD4.2 Stability and changeC4.1

Also works as an EE

Plastic in the sand: how far up the beach?

Tiny plastic fragments wash up on beaches. Count them in a measured volume of sand and see where they gather.

SL ●●●HL ●●●Fieldwork + Lab

D4.2 Stability and changeD4.3 Climate changeC4.2

Also works as an EE

Reading a stream by its small animals

Some water animals only live in clean water. Sample a stream or pond and score how healthy it is.

SL ●●●HL ●●●Fieldwork

B4.2 Ecological nichesC4.1 Populations and communitiesD4.2

Also works as an EE

How salty can a seed stand?

Salty soil threatens crops and coasts. Find the point where germination starts to fail.

SL ●●●HL ●●●Lab

D2.3 Water potentialD4.3 Climate changeB2.1

Also works as an EEFree full card

Herd immunity in a simulation

You cannot run an outbreak in a classroom, but you can model one. How many people must be vaccinated?

SL ●●●HL ●●●Simulation + Modelling

C3.2 Defence against diseaseC4.1 Populations and communities

Also works as an EEFull guide

Does metabolic rate really scale with mass to the three-quarters?

An elephant is 10,000 times heavier than a mouse but uses nowhere near 10,000 times the energy. Check the famous rule.

SL ●●●HL ●●●Database

B4.1 Adaptation to environmentC1.2 Cell respirationTI

Also works as an EEFull guide

Natural selection vs chance: will a helpful allele win?

A mutation makes an organism fitter, and it still vanishes more often than not. Build a population and watch.

SL ●●●HL ●●●Simulation + Modelling

D4.1 Natural selectionD3.2 InheritanceD4.2

Also works as an EEFull guide

How noisy can enzyme data get before the fit fails?

Textbook linear plots look neat. Test how well they recover the true constants when real-life noise is added.

SL ●●●HL ●●●Simulation + Modelling

C1.1 Enzymes and metabolismTI Tools and inquiry

Also works as an EE

How heavy is a longer fish? Length-weight data

A fish twice as long should be eight times as heavy, but real fish are not so tidy. Test the rule.

SL ●●●HL ●●●Database + Modelling

B4.1 Adaptation to environmentTI Tools and inquiry

Also works as an EE

Do bigger animals live longer?

Larger mammals tend to live longer, but bats and mole rats refuse to follow. Test the pattern and find the exceptions.

SL ●●●HL ●●●Database

B4.1 Adaptation to environmentC1.2 Cell respirationD4.1

Also works as an EE

How good is mark and recapture? A bead-bag test

Ecologists estimate population size by marking some and catching some again. Test how accurate the method is with a population you can count.

SL ●●●HL ●●●Simulation + Modelling

C4.1 Populations and communitiesTI Tools and inquiry

Free full card

Hares and lynx: can two equations draw the cycle?

Predator and prey numbers rise and fall in cycles. Build the classic model and see how far it can match the record.

SL ●●●HL ●●●Simulation + Modelling + Database

C4.1 Populations and communitiesD4.2 Stability and change

Also works as an EE

Onion roots: does the mitotic index vary by time?

Everyone counts dividing cells at one time of day. Does it matter when you look?

SL ●●●HL ●●●Lab

D2.1 Cell and nuclear divisionA2.2 Cell structure

Also works as an EEFull guide

Cytoplasm on the move: how warm does streaming need?

In pondweed cells, chloroplasts ride a current of cytoplasm. It speeds up when it is warm. By how much?

SL ●●●HL ●●●Lab

A2.2 Cell structureB2.2 Organelles and compartmentsC1.1

Also works as an EE

Many small or few large: a trade-off in guard cells

Plants can make lots of small stomata or a few large ones. Test whether that trade-off is real.

SL ●●●HL ●●●Lab + Fieldwork

B3.1 Gas exchangeB2.3 Cell specialisationA3.1

Also works as an EEFree full card

Power stations: mitochondria in different cells

Cells that burn more energy should pack in more mitochondria. Check it with published electron micrographs.

SL ●●●HL ●●●Database

B2.3 Cell specialisationC1.2 Cell respirationA2.2

Also works as an EE

A whole growing season: modelling crop growth under five treatments

Grow a fast crop in plots through a full season with 5 levels of one treatment, and fit a growth model to the whole series.

SL ●●●HL ●●●Fieldwork + Lab + Modelling

C1.3 PhotosynthesisC4.2 Energy and matter transfersD4.3

Antibiotic resistance over time: what do surveillance data show?

Resistance rates change country by country and year by year. What is the link with antibiotic use?

SL ●●●HL ●●●Database + Modelling

C3.2 Defence against diseaseD4.1 Natural selectionD4.2

What shapes resting heart rate? A national health survey

A huge public survey records pulse, age, size and habits. Which of these explains resting rate best?

SL ●●●HL ●●●Database + Modelling

B3.2 Transport in organismsC3.1 Integration of body systemsD3.3

Why are there more species near the equator?

Species richness rises toward the tropics. Test the pattern with open data, and test an explanation.

SL ●●●HL ●●●Database + Modelling

A3.1 Diversity of organismsB4.2 Ecological nichesC4.1TI

Does a warmer spring bring flowers earlier?

Plants open their buds when the weather lets them. How closely do records of first flowering follow temperature?

SL ●●●HL ●●●Database + Modelling

D4.3 Climate changeC4.1 Populations and communitiesTI

A year in the school grounds: a biodiversity time series

Survey the same plots every month for a year and ask how the community changes with the seasons.

SL ●●●HL ●●●Fieldwork + Database

C4.1 Populations and communitiesB4.2 Ecological nichesA3.1

Are species moving? Range shifts from open records

Observations of a species at different latitudes across decades can show whether it has moved.

SL ●●●HL ●●●Database

D4.3 Climate changeB4.2 Ecological nichesA4.2TI

Do abundant proteins use favourite codons?

Many codons code for the same amino acid but are not used equally. Does the choice track how much protein a cell makes?

SL ●●●HL ●●●Database + Modelling

D1.2 Protein synthesisD2.2 Gene expression HLA3.1

Which genes are under pressure? dN/dS across mammals

Changes that alter a protein are rarer than silent ones when a gene matters. Measure the pressure across genes.

SL ●●●HL ●●●Database + Modelling

D4.1 Natural selectionD1.3 Mutation and gene editingA3.2 HL

How hot is too hot for a reef? Bleaching and sea temperature

Corals bleach when the sea stays warm. Find out how long and how hot it must be.

SL ●●●HL ●●●Database + Modelling

D4.3 Climate changeC4.2 Energy and matter transfersB4.1

Does phosphorus predict algae? Long lake series

Decades of lake records show phosphorus and chlorophyll side by side. How closely do they move together?

SL ●●●HL ●●●Database + Modelling

C4.2 Energy and matter transfersD4.2 Stability and changeTI

Can a simple model fit a real outbreak?

Real epidemics have waves, delays and changing behaviour. See how far a simple model can follow a real curve.

SL ●●●HL ●●●Database + Modelling

C3.2 Defence against diseaseC4.1 Populations and communitiesTI

Does a bigger genome mean a bigger cell?

Genome size varies hugely between species. Test whether it tracks the size of the nucleus and cell.

SL ●●●HL ●●●Database + Modelling

A1.2 Nucleic acidsA2.2 Cell structureD2.1TI