Transcript Starr/Taggart PowerPoint

The Origin and Evolution of Life
Starr/Taggart’s
Biology:
The Unity and Diversity of Life,
Chapter 21
9e
Key Concepts:
Life originated more than 3.8 billion years
ago
All of the compounds necessary for life
could have formed spontaneously under
conditions that existed on the early Earth
The history of life spans five intervals of
geologic time
Key Concepts:
Divergence led to two prokaryotic
lineages and to the eukaryotic divergence
A theory of endosymbiosis helps explain
the profusion of specialized organelles
All of the kingdoms are characterized by
persistence, extinctions, and radiations
Certain environmental insults have had
profound impacts on the direction of
evolution
Conditions on the Early Earth
4.5 billion years ago
“Cloud” began to condense
4 billion years ago
Crust and mantle formed
Primitive atmosphere
H2, N2, CO, CO2 , probably no O2
Hot temperatures
Early Earth
 Primitive atmosphere
H2
N2
CO
CO2
Probably no O2
Synthesis of
Organic Compounds
Stanley Miller’s experiment
Methane, hydrogen, ammonia and water in a
reaction chamber
Simulated lightning
Amino acids and small organic compounds
formed
Synthesis of
Organic Compounds
Emergence of the
First Living Cells
Metabolism
Natural assembly of enzymes, ATP and other
organic compounds
Chemical interactions
A + B -------> C -------> D
enzyme
enzyme
Origin of Porphyrin Ring
Structure
In chlorophyll and cytochromes
In energy-yielding pathways
Emergence of the
First Living Cells
Self Replicating
Systems
RNA
DNA
Plasma Membranes
Proto-cells
Origin of Prokaryotic
and Eukaryotic Cells
Where Did
Organelles Come From ?
Membranous enclosures
Nucleus
ER
Endosymbiosis
Mitochondria
Chloroplasts
Both have self-replicating DNA, divide
independently of cell
Endosymbiosis
Life In the Paleozoic Era
Periods
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
All six kingdoms in the seas
Land plants and animals arise
Life in the Paleozoic
Cambrian 550-500 mya
Land masses dispersed near equator
Simple marine communities
Origin of animals with hard parts
Ordovician 500-435 mya
Gondwana drifts south
Major radiations of marine inverbrates and
fishes
Life in the Paleozoic
Ordovician-Silurian boundary
435 mya
First known ice age
First known global mass extinction
Silurian and Devonian eras
Vascular plants arise
Origin of amphibians
Life in the Paleozoic
Silurian swamp
Dominated by nonvascular plants
Forerunners of
modern ferns and
club mosses
Life in the Paleozoic
Devonian-Carboniferous boundary
Sea levels change dramatically
Mass extinction
Carboniferous 360-290 mya
Radiations of insects, amphibians
Origins of reptiles
Spore-bearing plants dominant
Life in the Paleozoic
Permian 290-240 mya
Radiation of reptiles and gymnosperms
Closed with greatest mass extinction
Land masses collided to form Pangea
More than 50% of families disappeared
Only 5% of known species survived
Life in the Mesozoic Era
Periods
Triassic
Jurassic
Cretaceous
Pangea began to break up
Continental drift
Divergence and Speciation
Major adaptive radiations
Life in the Mesozoic
Angiosperms arose in
the late Jurassic or
early Cretaceous.
Adaptive radiation
made them dominant
plants in land
environments
Rise of the Ruling Reptiles
Dinosaurs
Arose early in the Triassic
Weren’t dominant until after mass extinction
Adaptive radiation
Two Hypotheses for Dinosaur Extinction
Asteroid Impact Theory
Global Broiling Theory
Last Few Seconds of the
Cretaceous
Life in the Cenozoic Era
Present era
Geological shift
Shifts in climate
Adaptive radiation of mammals
Tropical forests
Woodlands
Grasslands
Species diversity
In Conclusion
 The Big Bang is a model of the origin of the
universe
 Every element of the solar system and of
life is a product of the physical and
chemical evolution of the universe
 Four billion years ago, the Earth formed
 The primitive atmosphere consisted of H2,
N2 , CO, and CO2
In Conclusion
 After the crust cooled, water accumulated
and seas developed
 Many experiments have yielded indirect
evidence that life originated under
conditions prevalent on the early Earth
 Life originated about 3.8 billion years ago
 Major changes in the Earth’s crust,
atmosphere, and oceans have influenced
life
In Conclusion
 Discontinuities in the fossil record mark the
time of global mass extinction
 The first living cells were prokaryotes
 Divergence led to the evolution and to the
ancestor of the Archaebacteria and
Eukaryotes
 Ozygen began to accumulate in the
atmosphere during the Proterozoic
In Conclusion
 Oxygen in the atmosphere served as a
selective pressure, bringing about the
spontaneous formation of organic
molecules
 Aerobic respiration was a key step towards
the origin of eukaryotic cells
 Mitochondria and chloroplasts probably
evolved as an outcome of endosymbiosis
In Conclusion
 Ozone developed as a product of an O2 rich
atmosphere.
 Ozone protects against ultraviolet
radiation
 Many events brought on pulses of mass
extinctions and adaptive radiations

developed by M. Roig