Biology
Genes, cells, bodies and ecosystems. 110 topics, from beginner to advanced.
Browse all 110 Biology topics →Featured
Visual showcases to start withCRISPR Gene Editing
A guide RNA directs the Cas9 enzyme to cut DNA at a precise location.
Polymerase Chain Reaction
Cycles of heating and cooling copy a DNA segment exponentially.
The Action Potential
A nerve cell fires an all-or-none electrical spike once its stimulus passes a threshold.
The Synapse
Neurons communicate across a tiny gap using chemical neurotransmitters.
The Heart and Circulation
A double circulation sends blood to the lungs for oxygen and then around the body.
Predator–Prey Cycles
Prey boom feeds predators; predators then crash the prey; the cycle repeats.
Food Chains and Webs
Energy and matter pass from producers to consumers and decomposers.
Epidemic Growth and R₀
The basic reproduction number sets whether an outbreak accelerates or fades.
The Immune Response
White blood cells recognise invaders, destroy them and remember them for next time.
Epigenetics
Chemical tags on DNA and histones switch genes on or off without changing the sequence.
Apoptosis: Programmed Cell Death
Cells dismantle themselves in an orderly way to shape tissues and remove damage.
Hormone Signalling
Glands release hormones into blood that bind receptors on target cells.
Popular
Classic topics most learners start withThe DNA Double Helix
Two antiparallel strands twist together, held by hydrogen bonds between A–T and G–C base pairs.
Natural Selection
Individuals better matched to their environment leave more offspring, shifting the population.
Mendel’s Monohybrid Cross
Crossing two heterozygous parents gives a 1:2:1 genotype ratio and 3:1 phenotypes.
Photosynthesis
Plants capture light energy to build glucose from carbon dioxide and water.
Cell Structure
Organelles divide up the work of a cell like departments in a factory.
Osmosis
Water crosses a semi-permeable membrane toward the side with more dissolved solute.
The Cell Cycle and Mitosis
A cell copies its DNA and divides into two identical daughter cells.
Meiosis
Two divisions produce four genetically unique gametes with half the chromosomes.
The Krebs Cycle
A cycle of reactions in the mitochondrion oxidises acetyl-CoA, loading electron carriers.
Antibiotic Resistance
Antibiotics kill susceptible bacteria and leave resistant mutants to multiply.
How Vaccines Work
A harmless piece of a pathogen trains memory cells before the real infection arrives.
The Carbon Cycle
Carbon moves between atmosphere, living things, oceans and rocks.
All 110 Biology topics
🌱 Beginner
- The DNA Double Helix
- DNA Replication
- The Central Dogma
- Codon Degeneracy
- Mutations
- Mendel’s Monohybrid Cross
- Punnett Squares
- Recessive Disorders
- The Hardy–Weinberg Principle
- Natural Selection
- Adaptation to a Changing Environment
- Antibiotic Resistance
- Speciation
- Polymerase Chain Reaction
- PCR Exponential Amplification
- Gel Electrophoresis
- Cell Structure
- Osmosis
- The Cell Cycle and Mitosis
- Cellular Respiration
- Homozygous Dominant × Recessive
- Test Cross
- Hardy–Weinberg with Rare Allele
- Hardy–Weinberg with Rare Dominant Allele
- Weak Selection
- Strong Selection
- Fast Predator–Prey Cycle
- Slow Predator–Prey Cycle
- Weak Stimulus to a Neuron
- Strong Stimulus to a Neuron
- Osmosis with Equal Concentrations
- Osmosis into a Concentrated Solution
- Logistic Growth with Low Capacity
- Enzyme with Competitive Inhibitor
- pH and Enzyme Activity
- Oxygen–Haemoglobin Dissociation Curve
- Bacterial Growth Curve
- Allometric Scaling of Metabolism
- Species–Area Relationship
- Stem Cell Differentiation
- Apoptosis: Programmed Cell Death
🔧 Intermediate
- Transcription
- Translation
- CRISPR Gene Editing
- Diffusion and Active Transport
- Meiosis
- Photosynthesis
- Light Response of Photosynthesis
- The Krebs Cycle
- ATP: The Energy Currency
- Temperature and Enzyme Activity
- The Action Potential
- The Synapse
- The Reflex Arc
- The Heart and Circulation
- Gas Exchange in the Lungs
- Digestion
- Kidney Filtration
- The Immune Response
- How Vaccines Work
- Plant Transpiration
- Phototropism
- Pollination and Seed Formation
- Predator–Prey Cycles
- Human Evolution Timeline
- Lineweaver–Burk Plot
- Mark and Recapture Estimate
- Heart Rate vs Exercise Intensity
- Drug Concentration after a Dose
- Repeated Dosing Reaches a Steady State
- Population Pyramid Growth Rates
- Hodgkin–Huxley Sodium Gate Idea
- Reaction Time and Distance
- DNA Repair Mechanisms
- Gene Regulation: The lac Operon
- Endosymbiosis Theory
- The Nervous System Pathway
- Menstrual Cycle Hormones
- Embryonic Development
- Blood Clotting
- Muscle Contraction
- Pandemic Response Timeline
- Heart Rates Across Animals
- Lifespans Across Animals
🚀 Advanced
- Michaelis–Menten Enzyme Kinetics
- Homeostasis and Negative Feedback
- Blood Glucose Regulation
- Logistic Population Growth
- Exponential Bacterial Growth
- Epidemic Growth and R₀
- Food Chains and Webs
- The Ecological Energy Pyramid
- The Carbon Cycle
- The Nitrogen Cycle
- Ecological Succession
- Symbiosis
- Biodiversity Across Biomes
- Brain Size Through Hominin History
- Nernst Potential for Potassium
- Epigenetics
- Cancer Development
- Hormone Signalling
- Bone Remodelling
- Thermoregulation
- Biofilm Formation
- Viral Replication
- Genome Sizes
- Chromosome Numbers
- Species Counts by Group
- Carbon Stored in Ecosystems
Frequently asked questions
What will I learn in Biology?
Genes, cells, bodies and ecosystems. Each topic has a live animation, a lesson and a quick quiz.
Where should I start?
Try “The DNA Double Helix” from the Popular list, or any beginner topic in Browse.
Are the topics in a set order?
Browse groups topics by level, with beginner topics first. Each topic’s FAQ names the topic to read before it.
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