Download Evolution: Diversification of Life

11/10/2008
Evolution: Diversification of Life
OCN201 Fall 2008
OCN201 Fall 2008
Zackary Johnson
University of Hawaii
Department of Oceanography
v20081110
Major Concepts
• Evolution involves three processes
– reproduction (heritability and over‐production)
reproduction (heritability and over production)
– variation
– “selection”
• Natural selection and genetic drift drive evolution
• Not a linear or directed process
• Extant diversity is a result of >3.5 billion years of E t t di
it i
lt f >3 5 billi
f
evolution
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Nothing in biology makes sense except in the light of evolution
‐Theodosius Dobzhansky
I am a creationist and an evolutionist. Evolution is God'ss, or Nature
Evolution is God
or Nature'ss method of 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. y
‐ Theodosius Dobzhansky
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Evolution
• Life has a history
• Different species share common ancestors
recent
past
Phylogeny: “family tree”, or how organisms are related http://evolution.berkeley.edu/
Evolution: descent with modification
• small scale changes (gene frequency in a population from one generation to another, “microevolution”)
• large scale changes (descent of different species from a l
l h
(d
t f diff
t
i f
common ancestor over many generations, “macroevolution”)
http://evolution.berkeley.edu/
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Evolution requires three processes:
• Reproduction (heritability and over‐production)
• Variation
• “Selection” (natural selection and genetic drift)
Evolution: Reproduction
• Heritability: traits are passed to offspring
– Recognized early in history, but Gregor Mendel (“father of genetics”) formalized its study using peas (29,000!) ti ”) f
li d it t d
i
(29 000!)
– 50 years later DNA indentified (Watson and Crick) as the carrier of genetic information
– Many many more details…
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Evolution: Reproduction
• Over‐production: more offspring produced than survive to reproduce (typically)
to reproduce (typically)
Evolution: Variation
• Offspring are not identical to parent or each other
• Mechanisms: – Mutations: changes in the DNA caused by the Mutations: changes in the DNA caused by the
environment or the lack of 100% fidelity in replication
– Gene flow: movement of genes from one population to another (i.e. new genes or alleles (different forms of a gene) introduced, or taken away)
– Sex: new combinations of genes Sex: new combinations of genes
or alleles
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Evolution: “Selection”
• Natural selection: favorable heritable traits become more common in successive generations of a population of reproducing organisms
~10,000 years (generations)
Evolution: “Selection”
• Genetic Drift (allelic drift): accumulation of random events that change the makeup of a gene pool slightly, but often compound over time
N = 10
Iwi
N = 100
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Evolution: in process
Origin of Species, Darwin (1859)
Evolution is not directed (“trees not ladders”)
Realm of Being
Being
God
Angels
Demons
Realm of Beecoming
Man
Non‐Being
Animals
Plants
Minerals
Aristotle’s “Chain of being”
Many aborted paths…
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Evolution: Key Events
Evolution: Key Events
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Evolution: Key Events
Evolution: Timing of Key and Selected Events
Organism
First Appearance (mya)
Prokaryotes
>3500
y
y
Photosynthetic Prokaryotes
2500
Eukaryotes
1000
Invertebrates
700
Vertebrates
500
Land Plants
430
Mammals
190
Apes
7
Humans
2.5
You
0.00002
Aquatic
(i.e. ocean
dominated)
Most of evolution (historically) occurred in the oceans
Organisms that we are familiar with (higher organisms) are relatively recent
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Major Concepts
• Evolution involves three processes
– reproduction (heritability and over‐production)
reproduction (heritability and over production)
– variation
– “selection”
• Natural selection and genetic drift drive evolution
• Not a linear or directed process
• Extant diversity is a result of >3.5 billion years of E t t di
it i
lt f >3 5 billi
f
evolution
10