Learn biology
This page is a staged plan for learning biology from scratch, built for someone whose last biology class was in school. It moves in a fixed order: first the vocabulary a textbook or a paper assumes you already have, then the sub-disciplines that group the work together, then the individual biologists and the papers and books they wrote, and finally those primary texts themselves. Biology is unusual among the sciences in that its founding documents are readable without mathematics, so the last stage is genuinely open to a beginner who has done the first three. Every concept, field, and biologist here links to real sources, mostly English Wikipedia, the Stanford Encyclopedia of Philosophy for the conceptual disputes, and NIH and Nature reference pages for the molecular material, so you can check any claim and read further.
Stage 1. Learn the vocabulary
Finish this stage able to define about eighteen core biological terms in your own words and explain, in two sentences, why each one matters.
Work through the concepts one at a time. Read the definition here, then read one cited source linked to that concept. Close both and write a two-sentence explanation from memory. Pay particular attention to the pairs that beginners collapse together: gene and allele, genotype and phenotype, natural selection and genetic drift, adaptation and fitness.
Stage 2. Map the fields
Finish this stage able to name each field's period, its core claims, and which biologists worked in it.
Read each field summary and its core claims, then read at least one cited source. Read them in the order given: it runs from the organism outward and downward, from whole-organism physiology and classification to populations, then to genes and molecules, and ends with the two fields that stitch the others back together. Notice where fields overlap rather than treating them as separate subjects.
Stage 3. Meet the biologists
Finish this stage with a working map of fifteen biologists: their dates, what they established, and which of their texts to read first.
Read each overview and note the recommended starting text. Read at least one cited source per biologist before moving on. The list is roughly chronological, which is also the order in which the ideas depend on each other: classification before evolution, evolution before genetics, genetics before molecular biology.
Stage 4. Go to the sources
Finish this stage having read one complete primary text, not a summary of one.
Start with Darwin's On the Origin of Species. It was written for the general reader of 1859, it assumes no mathematics, and the first four chapters carry the whole argument. Wallace's Contributions to the Theory of Natural Selection is the shorter route to the same idea from the other discoverer. Mendel's paper is about forty pages and is the clearest example in biology of a result reached by counting. All of these, plus Bernard on experimental method and Pasteur on fermentation, are free and complete on Project Gutenberg; Darwin Online holds every edition and manuscript Darwin produced. Later texts by Fisher, Dobzhansky, Mayr, and Carson are still in copyright and need a library.
