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Evolution

Evolution. Fundamental Question. How does the ever increasing “organized complexity” of living organisms come about?. Stages of Evolution. Physical formation of Universe: 10-15 BYA cosmology, Big Bang, … formation of Solar System: 4.5 BYA Chemical amino acids, nucleotides, polymers, …

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Evolution

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  1. Evolution

  2. Fundamental Question How does the ever increasing “organized complexity” of living organisms come about?

  3. Stages of Evolution • Physical • formation of Universe: 10-15 BYA • cosmology, Big Bang, … • formation of Solar System: 4.5 BYA • Chemical • amino acids, nucleotides, polymers, … • Biological • requires long time (began 3.5-4 BYA) • heritable variation and natural selection • also “self-organization” (complex systems theory)

  4. Biological Classification • prokaryotes vs. eukaryotes • prokaryotes: mostly bacteria (single cells) • eukaryotes: have membrane-bound organelles (nuclei, mitochondria, chloroplasts, …) • originated about 1.5 BYA

  5. Nucleus CellMembrane Rough ER Smooth ER Golgi Complex Mitochondrion Lysosome AnimalCell

  6. p. 603 Endosymbiotic Hypothesis • Organelles (including mitochondria, chloroplasts, and cilia) evolved from bacteria that, once upon a time, were ingested by cells. • These organelles have • double membranes • their own DNA & do their own protein synthesis • rRNA more like that of bacteria than eukaryotes endocytosis

  7. Animals Fungi Plants Protists Monera Traditional 5-Kingdom Scheme • Monera ~ prokaryotes (bacteria) • Other 4 kingdoms ~ eukaryotes • Protists (e.g. Paramecium) • Note: this “textbook” scheme, based on appearances, is in trouble …

  8. EUKARYA BACTERIA ARCHAEA UNIVERSAL ANCESTOR Modern Phylogenetic Tree • This new 3-kingdom scheme is based on molecular biology data: • sequencing of so-called 16S rRNA from ribosomes • – “molecular evolution” • (see Sci. Am. 4/97, p. 87; link)

  9. Biological Evolution • Charles Darwin • Alfred Russel Wallace • Evolution ~ greatest unifying theory in biology!

  10. Two Major Components of Evolution • heritable variation (random) • mutation • recombination (sex, etc.) • natural selection (nonrandom) • exerts itself on individuals • but evolution applies to populations

  11. A Proposed Third Component “Self-Organization” • promoted by Stuart Kauffman (U Penn & Santa Fe Institute) • 2 books: Origins of Order & At Home in the Universe • derived from “chaos” and “complexity theory” (computer models) • spontaneous order (like crystallization) • works best at “the edge of chaos” • important for origin of life, cell differentiation, etc. • implies “inevitability” of life under primordial conditions

  12. Theodosius Dobzhansky • “Nothing in Biology Makes Sense Except in the Light of Evolution” “Seen in the light of evolution, biology is perhaps, intellectually, the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts—some of them interesting or curious but making no meaningful picture as a whole.”

  13. Darwin Fan “If I were to give an award for the single best idea anyone has ever had, I’d have to give it to Darwin, ahead of Newton and Einstein and everyone else.” … Daniel C. Dennett

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