Evolution and Diversification of Life

Transcription

1 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

2 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

3 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

4 A Fundamental Division Prokaryotes (no nucleus) Bacteria Archaea DNA DNA Eukaryotes (with nucleus and other internal compartments) DNA

5 ADAPTATIONS TO DIFFERENT HABITATS

6 Phylogenetic Tree Current Species Last Common Ancestor

7 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

8 Hierarchical Classification Linnean Taxonomy Bottlenose dolphin Orca Common Octopus Species Genus Family Order Class Phylum Kingdom Domain delphis Delphinus Delphinidae Cetacea Mammalia Chordata Animalia Eukarya Orcinus orca Delphinidae Cetacea Mammalia Chordata Animalia Eukarya vulgaris Octopus Octopodidae Octopoda Cephalopoda Mollusca Animalia Eukarya

9 How do we deal with microbes?

10 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! 10

11 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

12 Sequence Comparisons Diversity and evolutionary relationships 1 2 Pairwise comparisons of sequences to count nucleotide differences Seq. A ATACGGTCAC.. Seq. B ATTCGCTCAC.. 2 Seq. C ATGCGGTCAC.. G Build tree which satisfies the observed distance relationships A C B Summarize differences in a distance matrix A B C A 2 1 B 2 2 C 1 2

13 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

14 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

15 Evolutionary History of Life Simple singe cell organisms (prokaryotes) appear first and diversify their metabolism over billions of years billion years ago Photosynthesis! A more complex cell type develops (eukaryotes) still single cells (microbes) 2 billion years ago Multicellular life built from complex cells appears 0.7 billion years ago Animals and Plants

16 Diversification of Life CELL TYPE DOMAIN BACTERIA Prokaryotes ARCHAEA Eukaryotes EUKARYA Animals Plants Photosynthesis Phagotrophy New mode of consumption by engulfment LUCA? Last Universal Common Ancestor

17 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)

18 Serial Endosymbiosis Theory The Origins of the Eukaryotic Cell Type Plants Animals 18

19 Origins of Animals Colonial Multicellular Unicellular

20 Origins of Plants Multicellular marine alga terrestrial moss Colonial Unicellular

21 Complexity Arises Over Time (lots of time!) 50 million Whales 190 million Land mammals 500 million Fish-like animals LAND PLANTS 700 million ANIMALS 2 billion Photosynthesis > 3.5 billion

22 The Three Domains of Life and two cell types Domain Domain Eukaryota Domain Prokaryotes Eukaryotes

23 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

24 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 7 Humans 2.5 You