Lecturer 16: Mendel Theory

Key Developments in Evolutionary Biology

• Mutation theory emerged as a rival to Darwin’s theory of natural selection, challenging the idea of natural selection as the sole source of variation in species.
• In 1903, Walter Sutton and Theodor Boveri proposed the Chromosome Theory of Inheritance, suggesting that chromosomes are the hereditary units and genes are located on them.
• Thomas Hunt Morgan's experiments with fruit flies in 1910 demonstrated that genes are located on chromosomes, leading to the integration of Mendel's theories with the Chromosome Theory of Inheritance in 1915.
• This integration initially challenged Darwinism, as Morgan believed that natural selection could only eliminate the unfit, not create novelty, contrary to Darwin's view that natural selection generates novelty.
• The modern synthesis, from 1936 to 1947, reconciled Mendelian genetics and Darwinian natural selection, affirming genetics as a powerful confirmation of evolution by natural selection.
• The discovery of the structure of DNA by Watson and Crick in 1953 revolutionized molecular genetics and provided a deeper understanding of the actual molecule in cells.
• The age of the earth was a major point of contention, with physicist Ernest Rutherford's application of radiometric dating, using radioactivity to estimate the age of the earth, leading to the discovery that the earth is approximately 4.5 billion years old.
• The mystery of the Wallace line, a distinct boundary between Asian and Australian species, was explained by the movement of tectonic plates, with the Australian plate pushing up materials from within the earth and leading to the separation of species.
• The theory of continental drift, first proposed by Alfred Wegener, was initially ridiculed but gained support with evidence such as identical rocks and fossils on either side of the ocean.
• Plate tectonics, accepted in the 1950s and 1960s, integrated evidence such as palaeomagnetism and the discovery of the mid-Atlantic ridge, leading to a better understanding of the movement of tectonic plates and the earth's magnetic field reversals.
• The integration of mutation theory, chromosome theory, the modern synthesis, the structure of DNA, radiometric dating, and plate tectonics contributed to a comprehensive understanding of evolutionary biology and the age of the earth.
• These key developments in evolutionary biology challenged and expanded foundational theories, leading to a more nuanced understanding of the mechanisms driving species variation, inheritance, and the history of the earth.

Test your knowledge of key developments in evolutionary biology with this quiz. Explore the integration of mutation theory, chromosome theory, the modern synthesis, the structure of DNA, radiometric dating, and plate tectonics, and their impact on our understanding of species variation, inheritance, and the earth's history.