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The Tree of Life: What is a Phylogenetic Tree?
Transcript of The Tree of Life: What is a Phylogenetic Tree?
Genetic Sequences (RNA Analysis) Using genetic sequencing, we can make really big trees that represent the diversity of all life on Earth Starting from the first split
between species of single-celled organisms: Eubacteria and
Archaea/Eukarya <-- Bacteria that way <-- Archaea/Eukarya that way Eukarya that way --> <-- Archaea that way Plants and algae go that way Amoebae, fungi, and animals go that way Do we look like the pinnacle of the evolutionary ladder now? Or are we just a single bud on the tree of life? We can move up (or down) the tree of life Encountering split after split... Each split represents An ancient speciation event Where one species
went one way... ...and the other went another Each point of intersection or "node" represents a real species that existed in the past that is, the "most recent common ancestor" of the two lines of descent So far, almost every branch has led to groups of protists. We're about to get to our first major multicellular group. Every branch leads to a group of organisms that still exists That said, 99% of the species that have ever lived on Earth are now extinct Think of all the species that have existed that don't show up on any tree! Only just now have we arrived at the vertebrates We've finally made it to land! <-- Mammals are that way <--Reptiles and birds are that way Almost there! and almost all the species here are fish <--Amphibians <--Reptiles/Birds/Mammals This course is about exploring & organizing the vast diversity of organisms that share your world Every species that still exists has been evolving just as long as we have. No species is more "highly evolved" than any other. Evolution only cares about survival, which every species on earth has found a highly successful way to do. [1.4 billion years ago] [600 million years ago] [360 million years ago] [320 million years ago] (Just 100 million years to go--dinosaurs still rule!) [3.5 billion years ago] This is the tree Darwin drew in his notebook while on the voyage of the Beagle.