Terrestrialisation (Precambrian–Devonian)

Abstract

Abstract The emergence of plants and animals from the sea on to land – terrestrialisation – was one of the major advances in the history of life on Earth. Evidence for early colonisation is poor, but the fossil record reveals that by mid‐Palaeozoic times, complex terrestrial ecosystems had become established. The first phase of land colonisation by organisms may have started in the Precambrian, some 2.6 gigaannums (Ga) ago, in the form of microbially bound alluvial sands. The second phase began in earnest in Ordovician times, when early land plants, in the form of bryophyte‐like spores, first appear in the fossil record. By the Silurian, true vascular plants were present, and these green swards were inhabited by mainly detritivorous and predatory arthropods. By the late Devonian, true forests had developed, but it was not until the latest Palaeozoic that modern‐type terrestrial ecosystems, with abundant herbivores in the food chain. Key Concepts: Organisms need to be overcome many physiological barriers when colonising the land from the sea. Conditions on the early Earth (∼4.6–1.0 Ga) were inhospitable to terrestrial life. Microbial crusts were likely the earliest land life. Higher plants appeared on land in the Ordovician period; vascular plants in the Silurian. The first land animals (Silurian) were detritivorous and predatory arthropods. Modern‐type ecosystems, with abundant herbivory and vertebrates, came in the latest Palaeozoic.