Three processes that have affected the history of life on Earth?

Answer 1

9a 1 ) High levels of UV light from the sun provided the energy for the formation of organic chemicals early in the life of the planet. UV may also have been responsible for the formation and dominance of RNA - as indicated in the first link. . 2) The formation of ozone by UV light acting on free oxygen produced by early life forms protected the surface from ultra violet radiation and allowed more stable forms and the colonization of the land surface. . 3) Bombardment of the Earth by meteors or asteroids created catastrophic events that made many species extinct but also provided the opportunity for other species to flourish - mammals did after the KT extinction 68 million years ago. 9b. 1) Continental drift (better referred to as plate tectonics) isolated some continents and islands - eg Australia and Madagascar and allowed unique life forms to evolve. . 2) Plate tectonics also resulted in changing climates. This was partly the result of continents changing latitude and thus moving closer or further from the poles - and partly the result of changing ocean configurations changing the climate of the whole planet. Climate change opened up new opportunities for the evolution of species and made others extinct.