General Biology II · Module 1 · Evolution and natural selection

Evolution and Natural Selection Lab

Run a natural selection island and watch a population change over generations; practise predictions, S and R = h²S with animated worked solutions; sort the evidence; and read real data. Nothing here is graded.

Part 1: Selection Island

Each generation the animals live, some are removed by selection, and the survivors breed. The histogram and the line graph update as the population evolves.
Finch (beak depth varies) Beetle (pale to dark) This generation Survivors Removed by selection Mean Best value for this environment (dashed)
Live readouts
MeasureValue

How the model works: each individual has a heritable (additive genetic) value plus a random environmental part; h² sets how much of the variation is heritable at the start. Survival falls off with distance from the best value for the environment (seed size for finches, background colour for beetles), more steeply with stronger drought or more predators. Survivors always refill the island (soft selection), so the population never dies out here. Offspring get the average of their two parents' heritable values plus random reshuffling; mutation adds new variation each generation. With no mutation, strong selection slowly uses up variation. Heritability shown in the readout is the current value and can drift as variation changes. Population size is 60, so there is some chance wobble. Generations are shown far faster than real life.