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

Petter Bøckman

Vertebrates

• 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