Biology Ladder · Free, age 5 to college
Climb from seeds and tadpoles to cells, genes and evolution
Learn how living things work, from what a plant needs to how a cell reads its DNA. Short lessons build each idea from the ground up, interactive pictures let you label a cell, fill a Punnett square, follow a food web and watch natural selection at work, and practice checks your answers and shows every step. Start with a grown-up at age five, or begin wherever you like. No sign-up, nothing to pay.
The ladder
Each rung is a full course. Start where you are; topics from earlier rungs come back when you need them.
How the Biology Ladder works
- Find your rung. A short check, at most 30 questions, skips what you already know and finds your starting point.
- Learn from first principles. Each topic is one small idea. The lesson shows why it works, then walks through worked examples one step at a time.
- Master it before moving on. Three right answers, the last two in a row, pass a topic. If a topic gets hard, we point you to the skill underneath it.
- Review, spaced out. Passed topics come back after 1 day, then 3, 7, 16 days and longer, for two quick problems each. Harder topics that use an older one count as practice for it.
- Mix it up. Reviews and checkpoint quizzes mix problems from different topics, so you learn to tell which method a problem needs.
- Earn XP. About one point per minute of focused work. Set a daily goal and keep your streak going.
- One climb across subjects. Every ladder shares your XP, streak and reviews. When a topic needs a skill from another ladder, such as the algebra behind a formula, that skill comes first, labeled with its ladder.
Why these steps: the U.S. Institute of Education Sciences practice guide Organizing Instruction and Study to Improve Student Learning (Pashler and others, NCER 2007-2004) recommends spacing reviews out over time, alternating worked examples with problems students solve on their own, pairing pictures with words, and using quizzes to bring key content back. The Biology Ladder is built around those ideas.
Try it in the Science Lab
Simulations to play with alongside the lessons.
- Predators and PreyGrass, rabbits and foxes rise and fall in turns. Overhunt, add a refuge, ride out a hard …
- Nature StudyAnna Botsford Comstock's Handbook of Nature-Study, with a guide for each of her lessons on birds, insects, plants and trees
- Food Garden PlannerGrow food from a windowsill to a backyard: what to plant, when, and how much it might yield
- Chemistry LadderAtoms, bonds and reactions, the chemistry under every cell
- Earth & Space LadderFossils, rock layers, the water cycle and climate
The other ladders
- Math LadderFrom counting in Kindergarten to calculus, linear algebra and differential equations. 27 courses.
- Physics LadderMotion, forces and energy, then fluids, heat, electricity, light, atoms and the stars, from grade 8 to college. 8 courses.
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- Economics LadderHow people, firms and whole economies choose: microeconomics, macroeconomics and calculus-based micro. 3 courses.
- Earth & Space LadderRocks, plates and volcanoes, oceans, weather and climate, and Earth's place among the planets and stars. 3 courses.
- Logic LadderClear thinking, from arguments and fallacies to syllogisms, truth tables and formal proofs, grade 7 to college. 3 courses.
- Etiquette LadderManners as kindness made into habits: please and thank you, the table, conversation, notes and hard moments, age 4 to adult. 3 courses.
- Egyptology LadderAncient Egypt from the Nile and the pyramids to reading hieroglyphs: history, Middle Egyptian, religion and art, and archaeology, age 8 to college. 6 courses.
- Ancient Scripts LadderHow ancient scripts work and how they were read again, beginning with Linear A and Linear B of the Bronze Age Aegean, high school to college. 1 courses.
- Vocabulary LadderOne thousand advanced words, each with a picture and a memory hook, plus the Greek and Latin roots that unlock them, grade 6 to adult. 2 courses.
- American History & Civics LadderThe American story and how its government works, from the flag and the Pilgrims to AP U.S. History, civics and the citizenship test, and on to law school courses in constitutional law. 7 courses.
- Writing & Grammar LadderFrom a first sentence to the persuasive essay: grammar and diagramming, usage and punctuation, paragraphs and essays, sources and citations, and rhetoric, age 6 to college. 6 courses.
All the ladders share one progress: XP, your streak and your reviews.
Your progress is saved in this browser
No account needed. To move to another device, or to keep a backup, copy your save code and paste it in on the other device.
See your progress · The site's My Progress page backs up everything at once.