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1 The origin of birds has long been debated. 2 • The fossil of the earliest known bird, Archeaopteryx, was discovered in 1861 3 Fossils of feathered dinosaurs have been discovered. fossil of Caudipteryx (尾羽龍) 4 They provide evidence to support that birds evolved from fossil of dinosaurs. Caudipteryx (尾羽龍) 5 They provide evidence to support that birds evolved from reconstructed dinosaurs. Caudipteryx 6 1 How did life originate on earth 7 2 Why are there so many different kinds of organisms on earth today 8 3 What are fossils What is their importance in the study of evolution 9 30.1 The origins of life How did life originate? 10 Theories on the origin of life on Earth 1. Special creation 11 Theories on the origin of life on Earth 2. Spontaneous generation 12 Experiments that disapprove spontaneous generation of life Francesco Redi (1626-1697) •One of the men to dispute "Spontaneous Generation" Did experiment with meat and flies, if flies were prevented from landing on meat, it did not13 produce maggots Theories on the origin of life on Earth 4. Cosmic theory 14 Theories on the origin of life on Earth 3. Primodial soup – chemical evolution 15 30.1 The origins of life Maybe simple organic molecules were formed from inorganic substances present in early earth’s atmosphere by the action of UV radiation and lightning. 16 30.1 The origins of life The organic molecules then joined to form the first organism. 17 30.1 The origins of life Let me do an experiment to test this hypothesis. Stanley Miller 18 30.1 The origins of life electric spark gas mixture of H2, H2O, NH3, CH4 boiling water heat 19 30.1 The origins of life simulated lightning condenser boiling water heat gas mixture of H2, H2O, NH3, CH4 water out water in liquid containing organic molecules20 30.1 The origins of life This supports the idea that organic molecules can be made from inorganic substances under the conditions of early earth. Stanley Miller 21 30.1 The origins of life No one knows the exact origins of life. Scientists believe that the first organisms are formed by joining organic molecules together. The organic molecules are produced from simple inorganic substances present in early earth’s atmosphere. 22 30.2 Biological Evolution What is the origin of the diversified life forms on earth today? 23 Life evolves and our Earth has been changing 24 30.2 Evolution Evolution is defined as the development of complex • organisms from pre-existing simple organisms over the course of time. 25 30.2 Evolution • scientists generally accept the theory of evolution (進化論) - life on earth started from a common ancestor (共同祖先) - this ancestor developed into all the different species today over a long period of time 26 Biological evolution Biological evolution focuses mainly on the relationship between species and major phyla rather than the origin of life 27 Common ancestor of all living things 28 30.2 Evolution Evidence for evolution: fossils • preserved remains or traces of organisms 29 30.2 Evolution Evidence for evolution: fossils • most are formed from the hard parts of organisms bones 30 30.2 Evolution Evidence for evolution: fossils • most are formed from the hard parts of organisms bones shells 31 30.2 Evolution Evidence for evolution: fossils • most are formed from the hard parts of organisms bones shells teeth wood of trees 32 30.2 Evolution Evidence for evolution: fossils • eggs, footprints, dung and pollen can also become fossils dinosaur egg fossil 33 30.2 Evolution Evidence for evolution: fossils • eggs, footprints, dung and pollen can also become fossils dinosaur footprint 34 30.2 Evolution Evidence for evolution: fossils • eggs, footprints, dung and pollen can also become fossils dung fossil 35 30.2 Evolution Formation of fossils mud and sand fish skeleton bottom of a lake 36 30.2 Evolution Formation of fossils upper layer mud and sand of sediment great pressure fish skeleton bottom of a lake mud and sand become rock 37 30.2 Evolution Formation of fossils deposition of mineral salts mud and sand become rock 38 30.2 Evolution Formation of fossils skeleton becomes fossil mud and sand become rock 39 30.2 Evolution Formation of fossils skeleton becomes fossil mud and sand become rock 40 30.2 Evolution Formation of fossils rocks rise above water younger rock layer older rock layer earth movement 41 30.2 Evolution Formation of fossils younger rock layer older rock layer further earth movement or weathering 42 30.2 Evolution Formation of fossils Video fossil exposed further earth movement or weathering 43 30.2 Evolution Fossil record • fossils are usually preserved in sedimentary rocks (沉積 岩) 44 30.2 Evolution Fossil record • fossils are usually preserved in sedimentary rocks (沉積岩) uppermost layer lowest layer 45 30.2 Evolution Fossil record • fossils are usually preserved in sedimentary rocks (沉積岩) youngest rock most recent fossil oldest rock earliest fossil 46 47 30.2 Evolution Fossil record • a sequence of fossils • from it, the evolutionary history can be traced • shows a developmental change from simple prokaryotic organisms to complex eukaryotic organisms agree with modern classification system 48 30.2 Evolution Fungi Animalia Plantae eukaryotes Protista prokaryotes Archaebacteria Eubacteria common ancestor 49 30.2 Evolution Fossil record • estimate age of fossils by radioisotope dating (放射性同位素定年法) time of existence of organisms 50 30.2 Evolution Fossil record • first appearance of different groups of organisms: land plants 490 humans reptiles mammals birds 420 440 350 250 200 fish amphibians dinosaurs 0.2 time (million of years ago) 51 30.2 Evolution Evolution of horse 60 million years ago today forelimb 0.4 m 1m 1.6 m body size 52 30.2 Evolution Evolution of horse • from the comparison of their structures: horses became larger in size forelimb 0.4 m 1m 1.6 m body size 53 30.2 Evolution Evolution of horse • from the comparison of their structures: legs became longer forelimb 0.4 m 1m 1.6 m body size 54 30.2 Evolution Evolution of horse • from the comparison of their structures: number of toes reduced forelimb 0.4 m 1m 1.6 m body size 55 Reconstruction of the evolution of horse from fossil record horses became larger legs became longer number of toes reduced 56 30.2 Evolution Limitations of fossil record • a continuous fossil record is seldom found gaps or missing links (缺少的環節) 57 30.2 Evolution Limitations of fossil record i) Unable to form fossils • dead bodies may be eaten by other organisms or may decay before fossilization occurs • conditions may not be suitable for fossilization 58 30.2 Evolution Limitations of fossil record i) Unable to form fossils • some organisms may not be fossilized e.g. soft-bodied organisms 59 30.2 Evolution Limitations of fossil record ii) Unable to find a complete set of fossils • some fossils are located in inaccessible areas • most fossils are incomplete and may be damaged • chance of discovery is low 60 Evidence for evolution: comparative anatomy 61 Evidence for evolution: comparative anatomy – vestigial structure 62 Pelvis and hind limb bones in whale cormorant Erector muscle in human skin Flightless cormorant 63 Evidence for evolution: artificial selection 64 • Artificial selection has produced dramatic change in domesticated species 65 Evidence for evolution: comparing key proteins 66 30.2 Evolution Evidence for evolution: genetic similarities • body characteristics are determined by the base sequence of DNA G A C G T A A G C G 67 30.2 Evolution Evidence for evolution: genetic similarities • organisms with closer evolutionary relationship would have accumulated less genetic differences 68 69 30.2 Evolution Evidence for evolution: genetic similarities • the more similar the base sequence, the closer the evolutionary relationship 98% 85% similarity in base sequence 70 Homology of molecules 71 72 30.2 Evolution Evidence for evolution: genetic similarities • the more similar the base sequence, the closer the evolutionary relationship more closely related 73 1 How did life originate on earth? The origins of life is still unknown today. It is generally believed that organic molecules were first formed from simple inorganic substances present in early earth’s atmosphere. 74 1 How did life originate on earth? The organic molecules then joined to form the first organisms. 75 2 Why are there so many different kinds of organisms on earth today? Most biologists believe that the different kinds of organisms on earth today evolved from a common ancestor over a long period of time. 76 3 What are fossils? What is their importance in the study of evolution? Fossils are the preserved remains or traces of organisms. They provide evidence for evolution. 77 Evolution can explain diversified life forms come from a common ancestor 78 Evolution supported by evidence like genetic similarities fossil record 79 fossil record found in sedimentary rock lower layers contain simpler life forms upper layers contain more complex life forms 80