# Biology study guides

Canonical: https://duckyhelper.com/learn/biology/
Updated: 2026-10-01

Plain-language biology guides for high school and AP Biology students. Each one explains the idea, works through real examples like Punnett crosses and codon charts, lists the mistakes teachers see most, and ends with practice questions. Facts are checked against OpenStax Biology 2e, and every computable answer was recomputed in code.

- [Cell organelles and their functions](https://duckyhelper.com/learn/biology/cell-organelles/): Cell organelles and what they do: nucleus, ribosomes, ER, Golgi, mitochondria, chloroplasts and more, plus plant vs animal vs bacteria cells and practice.
- [Enzymes](https://duckyhelper.com/learn/biology/enzymes/): How enzymes work: activation energy, the active site, induced fit, and how temperature, pH and inhibitors change enzyme activity. Data examples and practice.
- [Cellular respiration](https://duckyhelper.com/learn/biology/cellular-respiration/): Cellular respiration step by step: glycolysis, the citric acid cycle and the electron transport chain, where each happens, fermentation and practice.
- [Photosynthesis](https://duckyhelper.com/learn/biology/photosynthesis/): Photosynthesis explained step by step: the overall equation, light-dependent reactions, the Calvin cycle, where each happens, and worked counting examples.
- [Mitosis vs meiosis](https://duckyhelper.com/learn/biology/mitosis-vs-meiosis/): Mitosis vs meiosis compared: purpose, phases, chromosome numbers and genetic variation, with a side-by-side chart, counting examples and 5 practice questions.
- [DNA replication](https://duckyhelper.com/learn/biology/dna-replication/): DNA replication step by step: helicase, primase, DNA polymerase and ligase, leading vs lagging strands, base pairing and semiconservative copying.
- [Transcription and translation](https://duckyhelper.com/learn/biology/transcription-and-translation/): Transcription and translation step by step: DNA to mRNA to protein, reading codons, the codon chart and mutations. Worked examples and practice questions.
- [How to do Punnett squares](https://duckyhelper.com/learn/biology/punnett-squares/): How to do Punnett squares: monohybrid, test cross, dihybrid 9:3:3:1 and sex-linked crosses, with genotype and phenotype ratios explained and practice.
- [Natural selection](https://duckyhelper.com/learn/biology/natural-selection/): Natural selection explained: variation, inheritance, overproduction and survival, with antibiotic resistance, population data and Hardy-Weinberg practice.
- [Food webs and energy pyramids](https://duckyhelper.com/learn/biology/food-webs-and-energy-pyramids/): Food chains, food webs, trophic levels and energy pyramids explained, with the 10% rule, trophic level transfer efficiency calculations and practice questions.
- [The immune system basics](https://duckyhelper.com/learn/biology/immune-system/): Immune system basics: barriers, inflammation and phagocytes (innate), B cells, T cells and antibodies (adaptive), memory and vaccines, with a comparison table.

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