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45 Cards in this Set
- Front
- Back
Earth is thought to have formed how many years ago? |
4.5 billions of years, or gigaannum (Ga) |
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Six stages for the evolution of life |
-Earth forms from interstellar material -Earth cools; early atmosphere and ocean forms -prebiotic chemical reactions -RNA evolves -First cellular life-forms evolve -The process of diversification begins |
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What is unique about Earth's history? |
Large bodies of water formed |
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Six stages of Earth History |
-Hadean Era -Archean Era -Proterozoic Era -Paleozoic Era -Mesozoic Era -Cenozoic Era |
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Hadean Era |
The solar system was still coming together; all sorts of stuff was flying around. Earth was bombarded by large, ET objects which repeatedly sterilized the surface, making life impossible (4.55 Ga to 4 Ga) |
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Archean Era |
First clear fossil evidence that life existed. Little oxygen, all life is prokaryotic (4 Ga to 2 Ga) |
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Proterozoic Era |
We see oxygen building in the ocean and then in rock sediments. Proliferation of organisms, eukaryotes appear: sans hard parts such as bone and teeth (2 Ga to 550 million years ago) |
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Paleozoic Era |
Hard-bodied fossils appear, complex multicellular organisms, invasion of the land by plants and animals (550 to 250 million years ago) --> HUGE extinction event where Earth almost lost life completely, possibly due to volcanic activity |
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Mesozoic Era |
Mammals and flowering plants arise; but the land is dominated by dinosaurs, gymnosperms, ferns and lycopods (250 to 65 million years ago) --> Asteroid extinction event |
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Cenozoic Era |
Land dominated by mammals and flowering plants (65 million years to present) |
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Pre-Cambrian Era |
Includes the Hadean, Archean, and Proterozoic Eras |
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Macromolecules of life |
Nucleic acid, DNA, RNA, proteins (vital) AND lipids & carbohydrates (less important) |
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Murchison Meteorite |
Contained tens of thousands of different organic compounds including 70 amino acids |
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Panspermia |
Extraterrestrial Sources of Organic "Seed" Material |
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Directed Panspermia |
Life on Earth was seeded intentionally |
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Crick and Orgel |
Came up with Directed Panspermia Theory |
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Autotrophy |
An organism capable of synthesizing its own food from inorganic substances |
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Isua, Greenland |
A 3.7 billion year old rock was discovered |
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Stromatolites |
Layered mats of sediment trapped within bacterial biofilms; some of the oldest fossil evidence of life |
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William Schopf |
Big name in ancient microfossil discoveries |
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Archaean Era was dominated by... |
Anaerobes |
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Unambiguous cyanobacterial fossils arise at... |
2.5 Ga |
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Cyanobacteria |
Produce oxygen |
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4 Stages of oxygenation on Earth |
- No atmospheric oxygen -Oxygenic photoautotrophy; oxygen absorbed by oceans -Oceans saturated with oxygen, terrestrial sediments begin to absorb oxygen -Sedimentary sinks saturated; oxygen accumulates in the atmosphere |
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Great Oxygenation Event |
-2 Ga to 2.5 Ga -An assumed (no evidence) catastrophic extinction of anaerobes -Methane is oxidized and the earth's climate starts to cool |
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Huronian Glaciation |
-2 Ga to 2.5 Ga -Earth cools as methane is oxidized -AKA Snowball Earth -Nearly the entire earth was covered in ice |
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LUCA |
Last universal common ancestor of all currently extant life; not the first living thing |
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Definition of life |
-Ability to store and transmit information -Ability to express stored information -Ability to evolve --> information can be altered and these alterations permit differential survival |
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Abiogenesis |
The original evolution of life or living organisms from inorganic or inanimate substances. |
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Abiogenesis Challenges (4 requirements for it to occur) |
-Information-containing molecules come from inorganic compounds -The chemical reactions involved must be favored by environmental conditions -Self-assembly is a crucial feature of the macromolecules -Processes that degrade macromolecules must be thwarted in some fashion |
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Montmorillonite (AlSi clay) |
An example of how minerals may have "nursed" oligonucleotides into macromolecule status. It could be an incubator by protecting molecules from UV light, temperature extremes, and degradation. |
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Heritable variation |
Variation that is able to be handed down to offspring |
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Oparin-Haldane Model (Replicator First) |
-Assemble simple molecules into building blocks for complex polymers -Assemble polymers that can store information and catalyze reactions -Add membranes and an energy source to make a living organism |
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Stanley Miller |
Miller was the first to actually experiment with "origin of life" conditions. He did his famous experiment as a first year graduate student. |
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Miller & Urey experiment |
Created a reducing environment rich in methane, ammonia, and hydrogen. After a spark of electricity and some time, amino acids had formed. |
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Possible energy sources for life |
Lightning, UV light, cosmic rays, volcanic eruptions, and Earth's own internal heat. |
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Environment of early Earth |
The environment was not as oxidizing as we thought. It was rich in carbon dioxide and nitrogen, which favors the formation of aldehydes rather than amino acids. |
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RNA World |
The idea the RNA was formed first, and eventually led to the DNA world |
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Spiegelman |
Experimented on the origins of life: Transferred an RNA template to an RNA primordial soup; showed the RNA got smaller as a result of competition |
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Self-assembly and Autocatalytic |
The holy grail of RNA world research |
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Metabolism First |
Idea that the metabolic pathways occurred before RNA; metabolic pathways can be disassembled and re-assembled sequentially |
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"Black Smokers" |
-Smoke billows out of deep sea vent; contains organic materials -The temperature differential is likely too high to be conducive to chemical evolution |
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Alkaline smokers |
More recent discovering; alkalinity allows for pH gradient; smaller thermal gradient; can have carbonate chimneys which have eukaryotic-cell sized pores |
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Black smokers |
Acidic, large temperature gradient |
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Chemiosmosis |
The movement of ions across a semipermeable membrane, down their electrochemical gradient. An example of this would be the generation of adenosine triphosphate (ATP) |