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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 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 A Fundamental Division • Prokaryotes (no nucleus) • • Archaea Bacteria • DNA DNA Eukaryotes (with nucleus and other internal compartments) DNA ADAPTATIONS TO DIFFERENT HABITATS Phylogenetic Tree Current Species Last Common Ancestor Classification of Life Classification of Life • The vast diversity of life makes sense when considered in the light of evolutionary history • The splitting of one species into two leads to a nested hierarchy of characteristics that can be shown as a branching tree Shared, derived characteristics 7 Hierarchical Classification Linnean Taxonomy • • • • • • • • Bottlenose dolphin Orca Common Octopus Species delphis Orcinus vulgaris Genus Delphinus orca Octopus Family Delphinidae Delphinidae Octopodidae Order Cetacea Cetacea Octopoda Class Mammalia Mammalia Cephalopoda Phylum Chordata Chordata Mollusca Kingdom Animalia Animalia Animalia Domain Eukarya Eukarya Eukarya How do we deal with microbes? Fossil vs Molecular Evidence ‣ Early work focused on plants and animals - detailed morphology easy to compare ‣ The evolutionary history of microbes was unclear ‣ Breaking of the genetic code changed everything! http://www.genome.gov/glossary/ 10 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 Summarize differences in a distance matrix Pairwise comparisons of sequences to count nucleotide differences Seq. A 1 2 Seq. B 2 Seq. C A B C A 2 1 B 2 2 C 1 2 ATACGGTCAC.. ATTCGCTCAC.. G ATGCGGTCAC.. A Build tree which satisfies the observed distance relationships C B 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 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 Image © Michael Vanden Berg 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 Diversification of Life CELL TYPE DOMAIN Prokaryotes BACTERIA ARCHAEA Eukaryotes EUKARYA Animals Plants Photosynthesis Phagotrophy New mode of consumption by engulfment LUCA ? Last Universal Common Ancestor 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 18 Origins of Animals Multicellular Colonial Unicellular Origins of Plants Multicellular marine alga Colonial Unicellular terrestrial moss Complexity Arises Over Time (lots of time!) 50 million 190 million 500 million 700 million 2 billion > 3.5 billion Whales Land mammals Fish-like animals ANIMALS Photosynthesis LAND PLANTS The Three Domains of Life and two cell types Domain Domain Prokaryotes Domain Eukaryota Eukaryotes 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 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
