Learn biology properly in five months
A free video series to fall in love with the subject, a free college-level textbook to give it rigor, and a free problem bank to make it stick — about 110 hours over a season. It ends with real foundational understanding: how a cell works, how genes become traits, how evolution ties every living thing together. Not memorized vocabulary you forget by summer, but a working model of life.
5 months · ~110 hours · a working understanding of life from cells to evolution
1.Crash Course Biology — Dr. Sammy Ramsey
Start here to get the whole shape of the subject before you grind any of it. This is the rebuilt 2024 series — 50 tight episodes covering an intro-college and AP Biology curriculum, hosted by entomologist Sammy Ramsey. Watch it fast, in order, without taking notes the first time through. The goal isn't mastery yet; it's to walk into the textbook already knowing roughly where everything fits — what a mitochondrion is for, why DNA matters, what natural selection actually claims. The series is free on the official Crash Course YouTube channel.
Free
Crash Course Biology →2.Biology 2e — OpenStax
This is the spine, and it's genuinely free — full web version and PDF, written and peer-reviewed for a two-semester majors course. Read one chapter a week, in sequence: chemistry of life, the cell, genetics, evolution, the diversity of organisms, ecology. Do not skim. Read the figures as carefully as the prose — in biology the diagram usually carries more than the paragraph. Where a chapter overlaps an episode you've already watched, you'll find it locks in fast; where it goes deeper, that's the point. The print edition is cheap if you prefer paper.
Free online; ~$50 for the optional print edition
OpenStax Biology 2e →3.Khan Academy Biology — problem practice
Reading biology feels like learning it; answering questions proves whether you did. After each OpenStax chapter, work the matching unit on Khan Academy — short videos plus practice questions on genetics, cellular respiration, molecular biology, and more. The Punnett-square and biochemistry problems are where most people discover the gap between recognizing a term and being able to use it. Free, no account required to practice, and it tells you immediately when you've fooled yourself.
Free
Khan Academy Biology →If this doesn't fit you
If you're a pre-med, biology major, or anyone who needs the canonical reference rather than a free survey, buy Campbell Biology (Pearson) and use it in place of OpenStax. It's the standard text in serious undergraduate courses for a reason — deeper, more current, and the one your professors will assume you've read. The trade-off is real money (often $100+) and a steeper, less gentle ramp, so keep the Crash Course videos as your on-ramp either way.
Why this path
The bottleneck in biology isn't difficulty — it's volume. The subject is an ocean of terms, and beginners drown trying to memorize them with no map. This sequence fixes that by giving you the map first: Crash Course shows you the whole landscape before you commit a single fact to memory, so every term in OpenStax has somewhere to attach. Then Khan Academy forces the active recall that converts recognition into knowledge. Most people who "studied biology and forgot it all" only ever did the passive half. The order here — overview, then depth, then practice — is what makes it stick, and it costs nothing.