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History of Life Timeline Answers bya = billions of years ago, mya = millions of years ago 4.6 bya Earth forms 3.5 bya First bacteria 3.4 bya First photosynthetic organisms 2.1 bya First multicellular life 600 mya first jellyfish 425 mya first sharks 220 mya first dinosaurs 200 mya first mammals 180 mya first flowering plants 90 mya last dinosaurs 2.6 mya First Stone tools, human use - Homo genus been around for about 2.8 mya - stone tools used by Australopithecus dated to 3.3 mya!! History of Earth Timeline Billions of years (2016) What is Biological Evolution? Biological evolution is the genetic change in a population of an organism over time. All living organisms are thought to have descended from a single ancestor – a one celled species. Charles Darwin developed the Theory of Evolution to explain how this happened. He used scientific evidence collected in his travels. The process of evolution occurs on a small and a large scale. Evolution only occurs in a population NEVER in an individual. Example: Ladybug Evolution Would the number of dark coloured ladybugs change in future generations if they were better camouflaged? How long would this take? What does “survival of the fittest” mean? What shell colour alleles do ladybugs have? Micro-evolution Micro-evolution is genetic changes that occur over a small number of generations. It is also called evolution within a species. Micro-evolution is when there is adaptation as a result of natural selection of the fittest offspring. Micro-evolution is caused by changes in allele frequencies in a population. These changes occur to help species better adapt to their environment. Micro-evolution can happen in a few generations. Micro-evolution Moth evolution in England is an example of microevolution. During the industrial revolution black moths were less visible to predators than white moths. Therefore, they were more likely to survive and reproduce. Therefore, the black allele became more common than the white allele. Spot the black moth! Macro-evolution Macro-evolution is genetic change on a large scale and takes centuries or millennia. Macro-evolution is also known as evolution between species and is documented in the fossil record. Lots of small changes or mutations can lead to new designs like the development of the eye, or organisms surviving in new habitats or climates. Macro-evolution can also lead to the extinction of species or to the rise of new species. Macro-evolution of Whales This is an example of how numerous micro-evolutionary changes eventually result in the formation of a new species by macroevolution. There have been periods of great diversity of life on earth followed by mass extinctions. Some branches on the evolutionary tree have been dead ends and there are no modern descendants living today. PBS video about tuberculosis (TB) Why does evolution matter now? https://www.youtube.com/watch?v=W-WumllRPL (9 min) Complete the worksheets. Also the PBS site with other videos: www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html