Post on 25-May-2020
Evolution and Diversification of Life
OCN 201 Science of the SeaBiology Lecture 2
Frogfish
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
• A more complex cell type develops (eukaryotes)
• 2 billion years ago
• Multicellular life built from complex cells appears
• 0.7 billion years ago
Photosynthesis!
still single cells (microbes)
Animals and Plants
Fossil Stromatolites Modern Stromatolites
Banded Iron FormationsIndependent evidence of photosynthesis beginning about 3 billion years ago
Microbial Fossils
Some Early Evidence of Life and Photosynthesis (there is more!)
• Prokaryotes (no nucleus)
• Bacteria
• Archaea
• Eukaryotes (with nucleus
A Fundamental Division
DNA
DNA
DNA
and other internal compartments)
Origin of the Eukaryotic Cell
• A new cell type that can consume prey (phagotrophy)
• Leads to specialized organelles
• Provided freedom for extraordinary morphological diversification (first single- then multicellular)
This changed everything!
The Origins of the Eukaryotic Cell TypeSerial Endosymbiosis Theory
6
Plants
Animals
Modern day evidence of organelle acquisitionKleptoplasty
7
Ciliate
A ciliate steals chloroplasts from its prey (a cryptomonad)Geminigera cryophila
Flagellate
Origins of Animals
Unicellular
Colonial
Multicellular
Origins of Plants
Unicellular
Colonial
Multicellularmarine alga terrestrial moss
Protista
Prokaryotae
Single CellEukaryotes
Prokaryotes
MulticellularEukaryotes
Animalia
Plantae Fungi
The Traditional Five Kingdoms
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
• 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
Basis of Evolution by Natural Selection
Biological Diversity Arises through Selection
This is not “just a theory”. It is a fact.
Incomplete Species Separations
donkeyhorse
mule
Incomplete Species Separations
False Killer WhaleBottlenose Dolphin
“Keikaimalu”
= Wolphin
+
Missing Links
Missing Links
Discovered 2008 (Matt Friedman)
Life is a Messy BusinessSymbioses 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
• 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
Fossil vs Molecular Evidence
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 ComparisonsDiversity and evolutionary relationships
Seq. A ATACGGTCAC..Seq. B ATTCGCTCAC..Seq. C ATGCGGTCAC..
A
C
B
1 22 G
A B CA 2 1B 2 2C 1 2
Pairwise comparisons of sequences to count nucleotide differences
Summarize differences in a distance matrix
Build tree which satisfies the observed distance relationships
Eukaryota
The Three Domains of Life
Prokaryotes Eukaryotes
and two cell types
Domain
Domain Domain
Time Line
First Prokaryotes >3500
Photosynthetic Prokaryotes 2500
Eukaryotes 1000
Invertebrates 700
Vertebrates 500
Land Plants 430
Mammals 190
Apes 7
Humans 2.5
You 0.00002
(millions of years ago)OrganismFirst appeared