Transcript Chap 15 – Three Domain System
Chapter 15
Tracing Evolutionary History
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
MAJOR EVENTS IN THE HISTORY OF LIFE
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Life’s Calendar
Figure 15.4
Archaean eon Origin of Earth 4.6
4 Proterozoic eon Phanerozoic eon Colonization of land Animals Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen Prokaryotes 3 Billions of years ago 2 1 Present
15.4 The origins of single-celled and multicelled organisms and the colonization of land were key events in life’s history
Prokaryotes lived alone on Earth for 1.5 billion years, from 3.5 to 2 billion years ago.
– During this time, prokaryotes transformed the atmosphere.
– Prokaryotic photosynthesis produced oxygen that enriched the water and atmosphere of Earth.
– Anaerobic and aerobic cellular respiration allowed prokaryotes to flourish.
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15.4 The origins of single-celled and multicelled organisms and the colonization of land were key events in life’s history
The oldest fossils of eukaryotes are about 2.1 billion years old.
The common ancestor of all multicellular eukaryotes lived about 1.5 billion years ago.
The oldest fossils of multicellular eukaryotes are about 1.2 billion years old.
The first multicellular plants and fungi began to colonize land about 500 million years ago.
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15.4 The origins of single-celled and multicelled organisms and the colonization of land were key events in life’s history
Humans diverged from other primates about 6 to 7 million years ago.
Our species,
Homo sapiens
, originated about 195,000 years ago.
If the Earth’s history were compressed into an hour, humans appeared less than 0.2 seconds ago!
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Larger Cells and Organisms Need More Oxygen
More O 2 allows for CR and aerobic metabolism = greater ATP yield!!
Molecular Homologies Provide Greatest Evidence for Life’s Common Ancestor
All living organisms share many biochemical and developmental pathways: DNA --> RNA --> Protein Same genetic code Transcription/translation/replication processes same Glycolysis and cellular respiration similar Many genes are amazingly similar – About 99% of the genes of humans and mice are homologous.
– About 50% of human genes are homologous with those of yeast.
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Three Domain System
Molecular homologies have unveiled a new organization to life’s history.
Comparison of rRNA gene sequences by
Carl Woese
Remember, rRNA gene sequences allow for comparison of long-distance relationships Biologists currently recognize a
three-domain system
consisting of – two domains of prokaryotes: Bacteria and Archaea, and – one domain of eukaryotes called Eukarya including – fungi, protists, plants, animals © 2012 Pearson Education, Inc.
Figure 15.19A
1 Most recent common ancestor of all living things 2 Gene transfer between mitochondrial ancestor and ancestor of eukaryotes 3 Gene transfer between chloroplast ancestor and ancestor of green plants Bacteria 3 2 1 Eukarya 4 3 2 Billions of years ago 1 0 Archaea
Figure 1.4 The Tree of Life
Implications of Updated Tree of Life
Bacteria and Archaea diverged very early in the evolutionary history of life Archaea are more closely related to eukaryotes than to bacteria.
Eukarya diverged from line of Archaea Several endosymbiotic events lead to evolution of eukaryotes Mitochrondria acquired from aerobic bacteria Chloroplast from photosynthetic bacteria Mitochondria acquired first; 1st eukaryotes heterotrophic Multicellularity in eukaryotes arose multiple times (convergent evolution) © 2012 Pearson Education, Inc.
Endosymbiosis theory
Mitochondria & chloroplasts were once free living bacteria
engulfed by ancestral eukaryote
Endosymbiont
cell that lives within another cell (host)
as a partnership Honors Biology
evolutionary advantage for both
one supplies energy the other supplies raw materials & protection Lynn Margulis U of M, Amherst
Endosymbiosis theory
Evolution of eukaryotes Honors Biology