Lecture 16: Life on Earth PDF

Lecture 16: Life on Earth Helicolenus lengerichi Austrarchaea andersoni Charadrius seebohmi Hylomis dorsalis Fona herzogae How many species? Origin of Species proposed universal common descent for all life on earth For every combination of species, there is a most recent common anc...

Lecture 16: Life on Earth Helicolenus lengerichi Austrarchaea andersoni Charadrius seebohmi Hylomis dorsalis Fona herzogae How many species? Origin of Species proposed universal common descent for all life on earth For every combination of species, there is a most recent common ancestor (MRCA) Last Universal Common Ancestor LUCA  Reverse tour of evolutionary history Start at present day and climb down the tree of life 8.7 million other species doing the same thing Branching points on tree of life à rendezvous points (speciations) At each point, meet our evolutionary cousins, and our collective most recent common ancestor How many ancestors do you have? number should double each generation – 2 parents – 22 grandparents – 23 great-grandparents… – 35 generations back (~1000 AD), 235 ancestors (> 34 billion)??! – at some point, pedigrees collapse. Some of your ancestors on mom’s side are also ancestors on your dad’s side. – if we go back far enough in time, any two individuals will share a common ancestor  “Rendezvous Zero” MRCA of all humans How far back in time would we have to go to find an individual who’s a direct ancestor of all people alive today? Nature 2004 Almost every human on earth is your 50th cousin or closer Rendezvous 1: Chimps & bonobos “If we are descended from chimpanzees, why are there still chimpanzees around?” Rendezvous 2: Gorillas MRCA of African great apes Rendezvous 3: Orang utans MRCA of all great apes Rendezvous 4: Gibbons MRCA of all apes  Rendezvous 5, 6: Old World & New World monkeys  Rendezvous 7: Tarsiers Rendezvous 8: Lemurs and Lorises 5 species tarsier 50 species lemurs, lorises etc 58 mya 63 mya; MRCA of all primates Rendezvous 10: Rodents & rabbits >2,000 rodent species Rendezvous 11: Laurasiatheres Bats, Insectivora, Carnivora, Perissodactyls… Rendezvous 14: Marsupials Rendezvous 15: Monotremes MRCA of all mammals Rendezvous 16: Reptiles  Other vertebrates Rendezvous 17: Amphibians – MRCA of all tetrapods 340 mya Rendezvous 18-22: Lungfish; Coelacanths; Ray-finned fish; Sharks; Jawless fish – these ‘fish’ are no more closely related to each other than they are to us – MRCA of all vertebrates 530 mya Rendezvous 26: Protostomes >1 million described species “To a first approximation, all animals are insects”  Rendezvous 34, 35, 36: Fungi, Amoebozoans, Plants Multi-cellularity has evolved separately in animals, plants, fungi, amoebozoans Rendezvous 38: Archaea Adaptations to extreme environments Rendezvous 39: Bacteria Summary: Life on Earth