Origin and History of Life Where it came from and how it got here

Chapter Outline Primitive Earth Primitive Earth Origin of First Cells Origin of First Cells Fossils Fossils The Precambrian The Precambrian The Paleozoic The Paleozoic The Mesozoic The Mesozoic The Cenozoic The Cenozoic Continental Drift Continental Drift Mass Extinctions Mass Extinctions

Beginnings The Universe (maybe) The Universe (maybe) Primitive Earth—Not paradise as we know it—much different than Earth today Primitive Earth—Not paradise as we know it—much different than Earth today

Simple to complex Question: How could these simple molecules be made into more complex ones? Question: How could these simple molecules be made into more complex ones? Answer: Abundant energy sources, lots of time. Answer: Abundant energy sources, lots of time.

Origin of organic molecules Alexander Oparin (1938) — a Russian biochemist with vision Alexander Oparin (1938) — a Russian biochemist with vision Stanley Miller (1953) – tested the hypothesis Stanley Miller (1953) – tested the hypothesis

Miller Apparatus

Other models Carbonaceous chondrites Carbonaceous chondrites Panspermia Panspermia

Panspermia Life brought in on asteroids and comets Life brought in on asteroids and comets EX. Deinococcus radiodurans EX. Deinococcus radiodurans

Abiotic Chemical Evolution Synthesis and accumulation Synthesis and accumulation Polymerization Polymerization Aggregation Aggregation Origin of heredity Origin of heredity

Origin of First Cells

Keep in mind!!! Chemical natural selection Chemical natural selection Conditions of primitive earth Conditions of primitive earth Timescale Timescale

Evolution of Macromolecules RNA first hypothesis RNA first hypothesis Protein first hypothesis Protein first hypothesis Clay hypothesis Clay hypothesis

RNA first hypothesis RNA contains information like DNA RNA contains information like DNA RNA is catalytic-- -- ribozymes. RNA is catalytic-- -- ribozymes.

Protein First Hypothesis Most enzymes are proteins Most enzymes are proteins Proteinoids Proteinoids Proteinoid microspheres Proteinoid microspheres Faithful replication? Faithful replication?

Clay hypothesis Unique chemical properties of clay. Unique chemical properties of clay. Combines parts of the RNA first and protein first ideas. Combines parts of the RNA first and protein first ideas.

Protocell Evolves Protocells -- precursors to the first true cells. Protocells -- precursors to the first true cells. lipid-protein membrane lipid-protein membrane Proteinoid microspheres Proteinoid microspheres Coacervates Coacervates Liposomes Liposomes

Protocell Anatomy

Energy Management Were the first protocells heterotrophs or autotrophs?

Origin of First Cells

The Origin of Life 2

Fossils Fossils are remains and traces of past life Fossils are remains and traces of past life Why are they so rare? Why are they so rare?

Fossils

Dating Fossils Relative Dating Absolute dating Combination

Strata

The Precambrian Age of microbes 570 mya bya 570 mya bya The First Cells —3.5-4 billion years ago The First Cells —3.5-4 billion years ago What were they like? What were they like? Energy management? Energy management? Aquatic or terrestrial? Aquatic or terrestrial? Prokaryote or eukaryote? Prokaryote or eukaryote?

Evolution of Autotrophs Life as Energy Management Life as Energy Management Chemoautotrophs Chemoautotrophs Photoautotrophs Photoautotrophs Atmospheric O 2 ~2 BYA Atmospheric O 2 ~2 BYA

Atmospheric O 2 —SO WHAT? O 2 is very reactive—Poison. Cells had to deal with this AerobicAnaerobic Facultative anaerobes Changes in atmosphere– O 2 and ozone. So? Consequences for energy acquisition

Circle of Life Carbon compounds, O 2 CO 2, H 2 O Respiration Photosynthesis Energy

Eukaryotes evolve More complex More complex Origin? Endosymbiont hypothesis Origin? Endosymbiont hypothesis

ribosomes cell wall plasma membrane food granule prokaryotic flagellum cytoplasm nucleoid (DNA)

flagellum cytoplasm rough endoplasmic reticulum ribosome microtubules lysosome mitochondrion Golgi complex plasma membrane intermediate filaments vesicle smooth endoplasmic reticulum free ribosome vesicle nuclear pore chromatin (DNA) nucleolus nuclear envelope nucleus

1. Anaerobic, predatory prokaryotic cell engulfs an aerobic bacterium. 2. Descendants of engulfed bacterium evolve into mitochondria. 3. Mitochondria-containing cell engulfs a photosynthetic bacterium. 4. Descendants of photosynthetic bacterium evolve into chloroplasts. aerobic bacterium

Multicellularity Evolves Examples?Volvox—Simple,multicellularAdvantages?

Summary of Precambrian Earth forms Earth forms Prokaryotes evolved Prokaryotes evolved Photosynthesis Photosynthesis Eukaryotes Eukaryotes Multicellularity Multicellularity Sexual reproduction Sexual reproduction

Paleozoic

Paleozoic 2 Mass extinction---Disappearance of a large number of species within a relatively small time interval. Mass extinction---Disappearance of a large number of species within a relatively small time interval. opportunities for speciation opportunities for speciation

PALEOZOIC- MAJOR EVENTS What were the major events of the Paleozoic? What were the major events of the Paleozoic? 1. three mass extinctions 2. Invertebrates dominated – exoskeleton 3. Primitive plants invaded land

PALEOZOIC- MAJOR EVENTS 1. Vertebrates appeared (jawless fishes) -- internal skeleton 2. Insects and amphibians invaded the land evolution of flight, evolution of lungs, evolution of stronger limbs, strengthened internal skeleton

PALEOZOIC- MAJOR EVENTS 1. Reptiles appear a) Shelled egg b) Scaly skin c) Reptiles diversify amphibians declined 2. Coal forming forests 3. Conifers appear

Invasion of Land Plants Plants Invertebrates Invertebrates Vertebrates Vertebrates

Mesozoic

MESOZOIC- MAJOR EVENTS The age of reptiles The age of reptiles Angiosperms evolve-insects diversify Angiosperms evolve-insects diversify Mammals and birds Mammals and birds Evolution of endothermy Evolution of endothermy

QUESTIONS From what to did dinosaurs evolve? From what to did dinosaurs evolve? From what to do to mammals evolve? From what to do to mammals evolve? From what did birds evolve? From what did birds evolve? What caused the mass extinction of dinosaurs? What caused the mass extinction of dinosaurs? Were the dinosaurs endothermic? Were the dinosaurs endothermic?

Endothermy vs Ectothermy Endothermy Warm –blooded Requires a high use of energy High metabolic rate Disadvantages?Ectothermy Cold blooded Less energy necessary Regulation?behavioralstructural inertial ectothermy

Cretaceous Mass Extinction Bolide theory the most widely accepted theory of the Cretaceous Mass extinction. Bolide theory the most widely accepted theory of the Cretaceous Mass extinction. Bolide and exploding asteroid. Bolide and exploding asteroid.

Cenozoic

CENOZOIC- MAJOR EVENTS Three mass extinctions Three mass extinctions Decline of reptiles Decline of reptiles Diversification of Diversification of Angiosperms Angiosperms Insects Insects Birds Birds Mammals Mammals

Factors That Influence Evolution Continental Drift Continental Drift Positions of continents and oceans are not fixed. Positions of continents and oceans are not fixed. How does this explain the presence of marsupials and monotremes in Australia? How does this explain the presence of marsupials and monotremes in Australia?

Continental Drift

Plate Tectonics Plate Tectonics Movements of Earth’s crust which is fragmented into slablike plates that float on a lower hot mantle layer. Movements of Earth’s crust which is fragmented into slablike plates that float on a lower hot mantle layer.

Plate Tectonics

Mass extinctions A mass extinction occurs when a large fraction of all living species becomes rapidly extinct. The fossil record shows that at least five major mass extinctions have occurred in the past 500 million years. Impacts of asteroids on Earth are suspected as a primary cause of mass extinction.

Mass Extinctions Mass extinctions have occurred throughout history. At the ends of: Mass extinctions have occurred throughout history. At the ends of: Ordovician Ordovician Continental Drift Continental Drift Devonian Devonian Bolide Event Bolide Event Loss of 70% of marine invertebrates Loss of 70% of marine invertebrates

Mass Extinctions Permian Permian Excess carbon dioxide. Excess carbon dioxide. Loss of 90% of ocean species. Loss of 90% of ocean species. Triassic Triassic Meteorite Collision Meteorite Collision Cretaceous—probably a bolide. Cretaceous—probably a bolide.

Permian Mass Extinction At the end of the Permian period (about 245 mya), destroyed 90-95% of marine and 70% of land species. Possibilities? The glaciation of Gondwanaland The glaciation of Gondwanaland the increased fluctuation of global temperatures the increased fluctuation of global temperatures volcanic eruptions occurring in Siberia volcanic eruptions occurring in Siberia

Mass Extinctions Intrinsic gradualism Extinction caused primarily by climate change or other gradual processes. EX. Global warming Extrinsic catastrophism Extinction caused by a catastrophe Ex. Asteroid collision with Earth

Review Primitive Earth Primitive Earth Origin of First Cells Origin of First Cells Fossils Fossils The Precambrian The Precambrian The Paleozoic The Paleozoic The Mesozoic The Mesozoic The Cenozoic The Cenozoic Continental Drift Continental Drift Mass Extinctions Mass Extinctions