Topics: Evolution, Plant, Bacteria Pages: 1 (311 words) Published: June 23, 2013
Darwin's theory of evolution explains how life on Earth has changed over geological time. Scientists believe this is the reason why all living things on Earth exist today. The theory is supported by evidence from fossils, and by the rapid changes that can be seen to occur in microorganisms such as antibiotic-resistant bacteria. Many species have become extinct in the past and the extinction of species continues to happen. The basic idea behind the theory of evolution is that different species have developed over time from simple life forms. These simple life forms first developed more than three billion years ago (as the Earth is believed to be about 4.5 billion years old).It explains how species are formed.

3,500,000,000 years ago-First bacteria (prokaryotes)
2,000,000,000 years ago-First cells with organelles (eukaryotes) 1,000,000,000 years ago-First multicellular organisms: algae, seaweeds, sponges, jellyfish worms 500,000,000 years ago-First fish
450,000,000 years ago-First land plants and fungi
390,000,000 years ago-First amphibians, insects and reptiles. Much of the land surface covered in fern forests which will eventually become coal 250,000,000 years ago-First mass extinction of life forms (the Permian-Triassic extinction) 220,000,000 years ago-Dinosaurs evolve

200,000,000 years ago-First mammals and birds
130,000,000-First flowering plants
65,000,000-Second mass extinction (cretaceous-Tertiary Extinction.) Dinosaurs die out. 45,000,000 years ago-First modern mammals
35,000,000 years ago-First grasses
3,000,000 years ago-First hominids (Australopithecus)
200,000 years ago-First Homo sapiens evolve. First Neanderthals evolve 100,000 years ago-Humans colonise all habitable land masses
20,000 years ago-Neanderthals die out, leaving Homo sapiens as the only species of human. 15,000 years ago-Agriculture begins
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