General Biology II · Module 3 · Speciation

Speciation Lab

Split a population with a river, mountains, rising seas or a polyploidy event and watch two gene pools drift apart while hybrid fertility falls; practise naming barriers and counting polyploid chromosomes with animated worked solutions; sort barriers and species concepts; and read real speciation data. Nothing here is graded.

Part 1: Speciation Island Bench

Population 1Population 2Genetic distance Trait differenceHybrid fertilityTest cross result
Speciation bench readouts
MeasureValue

Simplified model. Genetic distance is a 0 to 1 index of how different the two gene pools are; with gene flow it levels off near 1 / (1 + 4Nm), the classic result for migrants per generation (Nm). Hybrid fertility falls as incompatible gene combinations pile up, slowly at first and then faster (the "snowball" pattern), and gene flow slows that build-up. Time is in thousands of generations and the scale is illustrative. A polyploidy event makes 4n plants whose crosses with 2n plants give mostly sterile 3n offspring.