Evolution of the biosphere. Biogenesis
Vernadsky divided biosphere evolution into three stages: first – the origin of life and the primary biosphere; second – the growing complexity of the biosphere as multicellular organisms diversified; third – the age of human society. Because the first two stages ran only by biological laws they are called biogenesis, the third noogenesis. The Earth formed about 4.5 billion years ago, with traces of life at least 3.5 billion years old; the first organisms were unicellular prokaryotes living without oxygen. Natural selection brought chemosynthetic and photosynthetic bacteria and cyanobacteria; photosynthesis led to the accumulation of oxygen in the atmosphere (the «Great Oxidation» beginning about 2.4 billion years ago). Oxygen built the ozone layer, and aerobic respiration, which releases much energy, opened the way to eukaryotes and ever more complex multicellular organisms. From the sea, first prokaryotes, then about 470–450 million years ago plants, followed by arachnids and other animals, colonised the land, and amphibians appeared about 370 million years ago.
On a paper strip let 4.5 billion years equal 45 cm (1 cm = 100 million years). Place the origin of life, oxygen build-up, move to land, dinosaurs and humans. Safety: take care if you use scissors.