Course web site

www.clas.ufl.edu/users/mcmack/2008

Module 1: Evolution

Month Day TopicAug 28 History of life on Earth

30 Timeline construction

Sept 1 Theory of evolution

4 Holiday

6 Evidence for evolution

8 Mechanisms of evolution I

11 Mechanisms of evolution II

13 Speciation

Outline

1. What is life?

2. How might it have arisen?

3. What has happened since then?

Time

Cosmological

Geological

Evolutionary

Ecological

Physiological

4.5 billion years ago, the earth was born

Life is...what?

Life shares...

1. Chemical composition – CHON(SP)CarbonHydrogenOxygenNitrogen

SulfurPhosphorus

Iron, Zinc, Calcium, Sodium...

Life shares...

2. Biochemistry in liquid water– Proteins– Lipids– Carbohydrates– Nucleic acids

Life shares...

3. Use of matter and energy– Energy stored and released by breaking

chemical bonds– Autotrophs– Heterotrophs– Metabolism– Enzymes– Homeostasis

Life shares...

4. Cells– Membranes– Cytoplasm– Organelles– Nucleus

A prokaryote cell...

Life shares...

5. Reproduction– Heredity– Variation

Life shares...

6. Ecology!!!!!

Life shares...

1. Chemical composition-CHON(SP)

2. Biochemistry

3. Use of matter and energy

4. Cells

5. Reproduction

6. Ecology

How did life start?

Causal mechanism

The biogenesis paradox

Life arises from life...

But what about the first organisms?

How did life start?

• In a very different earth environment– Reducing atmosphere—No O2!

– Lots of H2O

– Lightening, volcanoes, ultraviolet rays

The primordial soup hypothesis

1. Abiotic synthesis of simple organic molecules

The primordial soup hypothesis

1. Abiotic synthesis of simple organic molecules

2. ...complex organic molecules

The primordial soup hypothesis

1. Abiotic synthesis of simple organic molecules

2. ...complex organic molecules

3. Origin of self-replicating molecules

The primordial soup hypothesis

1. Abiotic synthesis of simple organic molecules

2. ...complex organic molecules

3. Origin of self-replicating molecules

4. Formation of pre-cells

The big leap

From pre-cells to life...

Lots of time for natural selection

Life first appears in the fossil record about 3.8 billion years ago

Changes on Earth that have shaped life…

• Atmosphere (O2, UV)

• Continental drift

• Climate

• Volcanoes

• Extraterrestrial bombardment

History has been punctuated by mass extinctions

1st mass extinction 440 mya: ~75% of species disappearSudden global cooling?

Predatory arthropod

2nd mass extinction 370 mya: ~75% of species disappearContinental collision or global climate change?

3rd mass extinction 245 mya: ~96% of species disappearThe greatest event of all time!

Extraterrestrial impact?

4th mass extinction 210 mya: ~65% of species5th mass extinction 65 mya: ~76% of speciesExtraterrestrial impact or volcanism?

The 6th mass extinction ...

• Last 10,000 years– 30% of earth’s species gone by year 2100