Macroevolution refers to evolutionary changes at or above the species level over large timescales. Speciation, the evolution of new species, occurs as reproductive barriers arise between populations, isolating them from interbreeding. Speciation can happen in isolated populations through allopatric speciation or within populations through sympatric speciation mechanisms like polyploidy. Mass extinctions, driven by events like meteorite impacts and continental drift, have punctuated the evolutionary history of life on Earth as revealed through the fossil record and phylogenetic analysis of anatomical and genetic similarities.

1. Lecture 6a: Macroevolution Macroevolution

17. Pangaea: its formation 250 mya was probably the cause of the Permian Extinction