Lecture 1: History of Life on Earth Flashcards
What are the subdivisions of “time” in the geologic record?
Eons > Eras > Periods > Epochs
Formation of Earth
Occur 4.6 bya (billion years ago)
Prokaryotes came first
3.6 bya
Conditions of early Earth
- How did the first living cells appear?
Hypothesis: chemical and physical processes could have produced simple cells
Conditions of early Earth
- What type of hypothesis deals with Synthesis of Organic Compounds of Early Earth?
Oparin- Haldane Hypothesis (1920)
- Earth’s early atmosphere was likely a reducing environment where organic compounds could have formed simpler molecules
How many stages had the hypothesis and what each represented?
4 stages
1) the abiotic synthesis of small organic molecules
2) joining of small molecules into macromolecules
3) packaging of macromolecules into protocells
4) origin of self-replicating molecules that eventually made inheritance possible
Conditions of Early Earth
- Who tested this hypothesis of Synthesis of Organic Compounds?
Miller & Urey’s Experiment (1953)
- AA found in modern organisms
- other organic compounds
How do we date fossils?
Measure half-life of radioactive isotopes
Archaean Eon
- First single-celled organisms
- sole inhabitants for more than 1.5 billion years
- oxygen levels increase
- Anaerobic
The oxygen revolution changed Earth’s environment dramatically. The presence of free oxygen in the oceans and atmosphere likely led to what?
Aerobic Respiration
Proterozoic Eon
First Eukaryotic Cells ~1.8 bya
Endosymbiont Theory
Mitochondria and plastids were formerly small prokaryotes that began living within larger cells
What is Endosymbiont?
a cell that lives within another cell (host cell)
Evidence that supported the Endosymbiont Theory
Evidence supporting the endosymbiotic origin of mitochondria and plastids
- inner membrane have enzymes and transport systems homologous to those in living prokaryotes
- Own DNA (Circular DNA)
- Replication similar to some prokaryotes
- Machinery for protein synthesis
- Ribosomes are more similar to prokaryotic ribosomes
Origin of Multicellularity
- Colonial Hypothesis (more leaning towards)
- Syncytial Hypothesis
What is Colonial Hypothesis?
Stick together, dependent, result to two radial ancestors
What is Syncytial Hypothesis?
only creates radial animals
Paleozoic Era
Colonization of land (~ 500 mya)
What did the Colonization of Land do the adaptations of the environment?
- They facilitated reproduction on land
- Minimized desiccation
- Requires eggs that don’t dry out
What animals had the Colonization of Land (Paleozoic Era)?
- Arthropods among first animals to colonize land
- Followed by tetrapods the evolved from lobe-finned fishes
Tetrapods= 4 foot
= Acanthostega- first to recognize limbs
= Tiktaalik- fish similar to tetrapods
Mesozoic Era
Age of Reptiles
“ Age of the Dinosaurs”
What plants had in the Mesozoic Era?
Cone-bearing plants dominant
Cenozoic Era
Age of Mammals
Mesozoic Era, Triassic Period
- Cone-bearing plants (gymnosperms) dominate landscape
- dinosaurs evolve and radiate
- origin of mammals
Mesozoic Era, Jurassic Period
- Gymnosperms continue to dominate plants
- dinosaurs abundant and diverse
Mesozoic Era, Cretaceous Period
- Flowering plants (angiosperms) appear and diversity
- many groups of organisms. including most dinosaurs, become extinct at end of period
Continental Drift
Movements in the mantle cause the plates to move over time
Rise and Fall of Flora and Fauna
What is related to speciation and extinction rates?
- Plate tectonics
- Mass extinctions
- Adaptive radiations
what are the consequences of the Continental Drift?
- Changes in climate
- Changes in coastal area vs. inner landmass area
- Water levels change
How many Mass Extinctions happend?
5
What are the names of the Mass Extinctions?
- Ordovician- Silurian Mass Extinction
- Late Devonian
- The Permian Extinction
- Triassic- Jurassic Mass Extinction
- The Cretaceous Extinction
What is the name of the mass extinction that was called the K-T Extinction?
the Cretaceous Extinction
Era/Period of Ordovician-Silurian Mass Extinction
- Paleozoic Era,
- Between Ordovician and Silurian Period
Year of Ordovician- Silurian Mass Extinction
455-430 MYA
Era/Period of Late Devonian
Paleozoic Era
End of Devonian Period
Year of Late Devonian
359 MYA
Era/Period of The Permian Extinction
- Paleozoic Era
- End of Permian Period
Year of Permian Extinction
251 MYA
Era/Period of Triassic-Jurassic Mass Extinction
Mesozoic Era
Between Triassic and Jurassic Period
Year of Triassic-Jurassic Mass Extinction
200 MYA
Era/Period of Cretaceous Extinction
Mesozoic Era
End of Cretaceous Period
Year of Cretaceous Extinction
65 MYA
Life forms affect during Ordovician-Silurian Mass Extin?
- Most life was aquatic
- Trilobites and early mollusks drastically reduced in number
Life forms affect during Late Devonian Mass Extin?
75% of all species dried out
- life in shallow seas affected more than other life forms
Life forms affect during The Permian Extinction?
“The Great Dying”
- 96% of marine animal species drastically altered life in ocean
- most extreme episode of volcanism
How can volcanism affect life forms?
- Produced enough CO2 to warm global climate by 6 C
- ocean become acidic
Life forms affect during Triassic- Jurassic Mass Extinc?
-50% of all species became extinct
- Marine reptiles
- some large amphibians
- reef-building creatures
- large numbers of cephalopod mollusks
- many species of plants survived
Life forms affect during Cretaceous Extinc?
- gone more than half of all marine species
- eliminate many families of terrestrial plants and animals
- including all dinosaurs
What type of events led to changes on Earth that may have influenced these extinction and subsequent adaptive radiation events?
- The Permian Extinc
- Triassic-Jurassic Mass Extinc
- Cretaceous Extinc
What led to the asteroid evidence of the K-T Extinction?
- Discovery of Chicxulub Crater (same age as K-T boundary)
- Finding tsunami deposits in the Brazos River Basin, Texas
- Discovering gravitational field anomalies on the Yucatan peninsula, from surveys done for oil exploration
- Identifying spherules and shocked quartz in Haiti
- Finding that an isotope of plutonium is not in the K-T boundary layer
What Period/Era/Epoch evolved in Humans?
Cenozoic Era
Quaternary Period
Holocene Epoch
