chapter 26 – early earth and the origin of life. history of earth on a clock… 1 23 4 billion...
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Chapter 26 – Early Earth and the Origin of Life
History of Earth on a clock…
1
2 3
4
Billion Years Ago
Origin of Earth (4.5 BYA)
- Earth Cools(3.9 BYA)
Origin of life (3.8 BYA)
Origin of Prokaryotes (3.5 BYA)
Oxygen in atmosphere (2.7 BYA)Endosymbiosis creates eukaryotic life (2.1 BYA)
Multicellular eukaryotic life begins in the sea (1.2 BYA)
Marine invertebrates evolve (.54 BYA)
Colonization of Land (.5 BYA)
Dinosaurs (.1 BYA) Humans (Today)
Origin of Earth
• 4.5 BYA, earth bombarded by rocks intense heat, no water (evaporated)
• Primordial atmosphere form due to volcanic activity– Gases released
• CO, CO2, H2, N2, S, HCL
• No O2
No oxygen = “reducing” power To create organic molecules
(Spontaneous Synthesis)
Back to clock
Primordial Seas
• Earth cools, crust solidifies
• Water is no longer vaporized, and seas form
Back to clock
Origin of LifeDue to non-oxygenated, reducing atmosphere and energy from lightening, heat, UV rays
small monomers (AA, nucleotides, etc.) randomly assemble (kinetics)
Polymerization occurs, forming macromolecules- RNA = 1st hereditary material
(single stranded)- RNA serves as 1st enzymes- Protobionts (membrane droplets) randomly packages organic
molecules inside (precursor to cells)
• Natural selection of protobionts favored those with primitive metabolism and inheritance
• DNA (double stranded) replaces RNA as hereditary material– DNA more stable– RNA take on more modern roles (translation)
Origin of Life
Back to clock
Origin of Prokaryotes
• 3.5 BYA
• 1st prokaryotes were – anaerobic (no O2) in atmosphere, and
– heterotrophic (abundant organic material to be used as food)
Back to clock
Oxygen in Atmosphere (2.7
BYA)• Mutation
heterotrophs gained ability to photosynthesize
• Oxygen gas generated, ends reducing power of atmosphere
• Ends of Spontaneous Generation Phase
Back to clock
Endosymbiosis Creates Eukaryotic Life
• Mutual symbiosis develop amongst autotrophic and heterotrophic prokaryotes
• Endocytosis of symbiotic prokaryotes occur
• Infolding of plasma membrane creates other membrane-bound organelles
Endosymbiosis Creates Eukaryotic Life
Chloroplasts and Mitochondria Support Endosymbiotic Theory because they
- have their own DNA and ribosomes
- are similar in size to prokaryotes
- self-replicate within eukaryotic cells by binary fission
- made up of double membranes, similar in structure to prokaryotes
Back to clock
Last 1.2 Billion Years
Multicellular life in oceans (1.2 BYA)
Colonization of Land (.5 BYA)
Dinosaurs (.1 BYA)
Humans Today
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