The evolutionary ideas of Ch. Darwin
Charles Darwin (1809–1882) travelled round the world on the ship Beagle in 1831–1836 and observed the species of the Galápagos Islands (finches with different beaks on each island – “Darwin’s finches”), South American fossils and geographic distribution. After long work he published “On the Origin of Species” in 1859 (A. Wallace had independently reached a close conclusion). Darwin studied breeding: in artificial selection people choose and breed individuals with useful traits (unconscious and methodical selection); modern breeds and varieties were made this way. He divided variation into definite (group, not inherited) and indefinite (individual, inherited), corresponding in modern terms to modification and hereditary variation. In nature organisms produce many offspring while resources are limited, so there is a struggle for existence: within a species (the most intense), between species, and against unfavourable environmental conditions. Individuals with useful hereditary traits survive and leave more offspring – this is natural selection. Over long time natural selection accumulates adaptations, species change and new species arise. Darwin did not know the mechanism of heredity; genetics (Mendel’s laws) later completed the teaching, and the modern synthetic theory of evolution was formed on this basis. The theory of evolution is a scientific theory confirmed by an enormous number of observations and lines of evidence.
“Selection game”: paper “moths” of two colours (light and dark) are scattered on a coloured background; students act as “birds” and count which colour they find more easily.