Evolution and Diversification of Life

OCN 201 Science of the Sea Steward

Biology Lecture 2The Handfish

-BBC Blue Planet1

2Phytoplankton Bacteria Viruses

Plankton Ecology

Grieg Steward, Professor Department of Oceanography

Plankton Ecology

When do you think life began?

A: > 3 billion years ago

B: about 6000 years ago

C: < 2000 years ago

D: around 1990

E: I’m still waiting

First Evidence of Life

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‣ Earth formed about 4.5 billion years ago (bya) and crust solidified 4.1 bya

‣ Mineral deposits, thought to be produced only by biological activity, dated at 3.8 bya

‣ Fossils resembling present-day mats of marine microorganisms found at about 3.5 bya

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Fossil Stromatolites Modern Stromatolites

Multicellular Lifeanimals, plants, fungi

Complexity appears gradually over timeEvolutionary History of Life

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BACTERIA & ARCHAEA

Prokaryotes Eukaryotes

EUKARYA

single-cellProtists

TIME

Protocell

photosynthesisevolves

colonial

A Fundamental Division

DNA

DNA

DNA

and other internal compartments7

‣ Prokaryotes (no nucleus)

• Bacteria

• Archaea

‣ Eukaryotes (with nucleus…)

….and other internal compartments

The Origins of the Eukaryotic Cell TypeSerial Endosymbiosis Theory

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Plants

Animals

Lynn Margulis

Pick the Prokaryote

B

D E

CA

Origins of Life

Not sure exactly how first self-replicating cell came into existence over 3.5 billion years ago

But once it did, it would be immediately subject to the process of evolution by natural selection

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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: More individuals with favorable traits will survive and reproduce than those with unfavorable traits

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When was the Theory of Evolution by Natural Selection first publicly presented?

A: 1776

B: 1858

C: 1903

D: 1918

E: 1982

…at the Linnean Society of London

Whose ideas were presented?

A: Charles Darwin

B: Alfred Russel Wallace

C: David Lee Roth

D: A &B

E: None of the above

On The Tendency of Varieties to Depart Indefinitely from the Original Type - Alfred Russel Wallace

On the Origin of Species - Charles Darwin

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Natural SelectionEvolution is not “just a theory”

Artificial Selection

Natural Selection

Incomplete Separations

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donkeyhorse

mule or hinny

Up to a two line subtitle, generally used to describe the takeaway for the slide

Incomplete Separations

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False Killer WhaleBottlenose

Dolphin

Wolphin

Keikaimalu

Pseudorca crassidens

Tursiops truncatus

Missing Links

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Discovered2006

Missing Links

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Discovered 2008 (Matt Friedman)Transitional flatfish fossils

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

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The Old Five Kingdom View of Life

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Prokaryotes

Protists

FungiPlants Animals

Multi-CellularEukaryotes

Single-CellEukaryotes

Prokaryotes

Incr

easi

ng C

ompl

exity

w

ith t

ime

New Understanding of the Diversity of Life

Early work relied on morphological differences - thus a focus on plants and animals

The evolutionary history of microbes was unclear

Molecular evidence (DNA Sequences) generally confirmed fossil evidence, but also revealed the deep history of the microbial world

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Morphology vs DNA sequences

compared to the very large genetic differences among bacteriaAll animals are quite closely related

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Look different, but close relatives Look similar, but very distance relatives

Florida Sea Grant Extension

Grieg Steward

Getty

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”

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Sequence ComparisonsDiversity and evolutionary relationships

Seq. A ATACGGTCAC..Seq. B ATTCGCTCAC..Seq. C ATGCGGTCAC..

1 2

2 G

A B C

A

B

C

A C BDistance matrix can then

be used to build aphylogenetic tree

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1

1

22

PlantsAnimals

Diversification of LifeBACTERIA EUKARYAARCHAEA

PhagotrophyNew mode of consumption

by engulfment

Photosynthesis

DOMAIN

Prokaryotes EukaryotesCELL TYPE

LUCA ?Last Universal Common Ancestor

Protists

Key Points

• Evolution is not uni-directional…but

• Simple things came first - complexity accumulates slowly through trial and error via many known mechanisms

• Eukaryotes arose through Serial Endosymbiosis

• The simple and the complex continue to co-exist

• As the earth changes, species die off and new ones emerge