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Evolution and Diversification of Life Frogfish OCN 201 Science of the Sea Biology Lecture 2 Grieg Steward (Oceanography) Office: CMORE Hale 121 Phone: x6-6775 Evolutionary History of Life • Simple singe cell organisms (prokaryotes) appear first and diversify their metabolism over billions of years • 3.5-3.8 billion years ago Photosynthesis! • A more complex cell type develops (eukaryotes) • 2 billion years ago still single cells (microbes) • Multicellular life built from complex cells appears • 0.7 billion years ago Animals and Plants Some Early Evidence of Life and Photosynthesis (there is more!) Microbial Fossils Banded Iron Formations Independent evidence of photosynthesis beginning about 3 billion years ago Fossil Stromatolites Modern Stromatolites A Fundamental Division • Prokaryotes (no nucleus) • • Archaea Bacteria • DNA DNA Eukaryotes (with nucleus and other internal compartments) DNA Origin of the Eukaryotic Cell This changed everything! • A new cell type that can consume prey (phagotrophy) • Leads to specialized organelles • Provided freedom for extraordinary morphological diversification (first singlethen multicellular) Serial Endosymbiosis Theory The Origins of the Eukaryotic Cell Type Plants Animals 6 Kleptoplasty Modern day evidence of organelle acquisition Flagellate Ciliate A ciliate steals chloroplasts from its prey (a Geminigera cryptomonad) cryophila 7 Origins of Animals Multicellular Colonial Unicellular Origins of Plants Multicellular marine alga Colonial Unicellular terrestrial moss The Traditional Five Kingdoms Multicellular Eukaryotes Plantae Fungi Animalia Single Cell Eukaryotes Protista Prokaryotes Prokaryotae Evolution Nothing in biology makes sense except in the light of evolution - Theodisius Dobzhansky I am a creationist and an evolutionist. Evolution is God's, or Nature's method of creation. Creation is not an event that happened in 4004 BC; it is a process that began some 10 billion years ago and is still under way. - Theodisius Dobzhansky Basis of Evolution by Natural Selection • Heritability of traits from parent to offspring • Variability among offspring (mutations, recombination) • Over-production of offspring • Selection by the environment: Individuals with favorable traits will survive and reproduce more Biological Diversity Arises through Selection This is not “just a theory”. It is a fact. Incomplete Species Separations donkey horse mule Incomplete Species Separations False Killer Whale + Bottlenose Dolphin = Wolphin “Keikaimalu” Missing Links Missing Links Discovered 2008 (Matt Friedman) Life is a Messy Business Symbioses and Horizontal Gene transfer Contribute to the Diversity We See It is a web of life as much as a tree of life Evolution • Evolution is not uni-directional • Simple things came first • Complexity accumulates slowly through trial and error via many known mechanisms • The simple and the complex continue to co-exist • As the earth changes, some species adapt or die off and new ones emerge Vertebrates Petter Bøckman Fossil vs Molecular Evidence • Early work relied on fossils - focus on plants and animals • The evolutionary history of microbes was unclear • Molecular evidence generally confirmed fossil evidence and revealed the deep history and diversity of the microbial world The History of an Organism is Written in its DNA • But how do we interpret it? • Can use changes in DNA sequence over time as a “molecular clock” Sequence Comparisons Diversity and evolutionary relationships Pairwise comparisons of sequences to count nucleotide differences Seq. A 1 2 Seq. B 2 Seq. C ATACGGTCAC.. ATTCGCTCAC.. G ATGCGGTCAC.. Summarize differences in a distance matrix A B C A 2 1 B 2 2 C 1 2 A Build tree which satisfies the observed distance relationships C B The Three Domains of Life and two cell types Domain Domain Prokaryotes Domain Eukaryota Eukaryotes Time Line Organism First appeared (millions of years ago) First Prokaryotes >3500 Photosynthetic Prokaryotes 2500 Eukaryotes 1000 Invertebrates 700 Vertebrates 500 Land Plants 430 Mammals 190 Apes Humans You 7 2.5 0.00002
