From cells to evolution

Begin with the cell, move on to the DNA inside it and how it is passed on, then finish with evolution. Each concept comes before the concepts that build on it.

1. Step 1Concept

   Cell

   The basic structural and functional unit of all known living organisms. Every living thing is made of one or more cells, each bounded by a membrane and containing the machinery needed to grow, respond to its environment, and reproduce. Cells fall into two broad types: prokaryotic cells (such as bacteria), which lack a nucleus, and eukaryotic cells (such as those in plants, animals and fungi), which organise their DNA inside a membrane-bound nucleus.

2. Step 23D explorer

   Cell Explorer

   Explore the organelles of a generalised animal cell in an interactive 3D scene, with real, cited cell-biology function descriptions and an isolate mode for each organelle.

3. Step 3Hands-on activity

   Testing Variables in Seed Germination

   A hands-on activity with 5 materials and 5 steps.

4. Step 4Concept

   DNA

   Deoxyribonucleic acid: the molecule that carries the genetic instructions used in the growth, development and reproduction of all known living organisms. DNA is shaped as a double helix of two strands, each made of a sugar-phosphate backbone with attached bases — adenine (A), thymine (T), guanine (G) and cytosine (C) — that pair specifically (A with T, G with C) to hold the two strands together. Its structure was determined by James Watson and Francis Crick in 1953, building on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins.

5. Step 53D explorer

   DNA Structure Explorer

   Explore the DNA double helix in an interactive 3D scene showing real Watson-Crick base pairing and B-DNA structural geometry, with base-pair highlighting and a sequence view.

6. Step 6Simulation

   DNA Inheritance

   Explore Mendelian inheritance interactively with a real monohybrid Punnett square — choose each parent's alleles and see the offspring genotype and phenotype ratios recompute live.

7. Step 7Concept

   Evolution

   The process by which populations of living organisms change in their heritable characteristics over successive generations. Charles Darwin and Alfred Russel Wallace proposed natural selection as its principal mechanism: individuals with heritable traits better suited to their environment tend to survive and reproduce more successfully, so those traits become more common in the population over time.

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