Unit 5 - Ch 21 - Origin Of Life Flashcards
Four theories of the origin of life
- Intelligent design
- Naturalistic
- Theistic naturalism
- Cosmozoic
Intelligent design
Some features of life are best explained by an intelligent cause instead of purely materialistic causes. This theory does not identify the cause agent. Some supporting scientists include: Behe, Minnich, Wells and Dembski.
Irreducible complexity
This is considered evidence for Intelligent Design. Structures with multiple components that only function as a whole are irreducibly complex.
=> bacterial flagellum
Design inference
From irreducibly complex structures, design is inferred.
Naturalistic
Life arose on earth by purely natural processes about 3.5 BYA.
Theistic naturalism
Life originated by divine intervention and natural processes produced the diversity. A compromise between creationism and naturalism.
Cosmozoic
Popular in the 1800’s and resurrected currently as Panspermia
Life on earth came from outer space. Evidence includes meteorites with organic residues. Crick and Pauling are scientists who support this theory.
Hypothetical Conditions For Naturalistic Origin of Life (6)
- Energy source
- Appropriate chemicals
- Absence of O2
- Time
- Aqueous environment
- Chemical selection
Explain why an “energy source” is a hypothetical condition for the naturalistic theory
Necessary to bring about change. Sunlight, geothermal, radiation, lightning.
Explain why “appropriate chemicals” are a hypothetical condition for the naturalistic theory
Water, inorganic ions and organics. Hydrogen rich conditions, like in our solar system, colide to create new molecules.
Explain why the “absence of O2” is a hypothetical condition for the naturalistic theory
No oxidation; organics break down unter O2.
Explain why “time” is a hypothetical condition for the naturalistic theory
Long time periods are required for extremely low probability events. Eons. From the time earth formed to the time life originated is roughly 1 billion years.
Explain why an “aqueous environment” is a hypothetical condition for the naturalistic theory
Temperature stable due to water’s high specific heat. Water is a source of dissolved materials, protects from UV, and encourages mixing.
Explain why “chemical selection” is a hypothetical condition for the naturalistic theory
Selection for abiotic systems. Selecting for chemicals with longevity and / or stability.
Hypothetical Steps in Naturalistic Origin (10)
- Organic monomers
- Formation of polymers
- Form aggregates
- Simple metabolism
- Heredity information
- First true organisms (prokaryotic)
- Photosynthesis
- Aerobic respiration
- Origin of eukaryotes
- Evolutionary tree
Hypothetical Steps in Naturalistic Origin:
Organic monomers
First Step
Miller and Urey test the Oparin and Haldore Hypothesis by simulating the hydrologic cycle (atmosphere and ocean). They filled the atmosphere with H rich compounds (reducing atmosphere). Nucleotides and amino acids will form.
Problems: living organisms only use L forms of AA’s but D and L are formed. Geochemists don’t think the early atomshpere was reducing.
Hypothetical Steps in Naturalistic Origin:
Formation of polymers
Second step
From monomers via condensation reactions. Endergonic.
Hydrolitic activity is favored.
Hypothetical Steps in Naturalistic Origin:
Form aggregates
Third step
The compartmentalization of polymers. Analagous to cells. Coaccervates (old) vs. proteinoid microspheres (newer). Compartments favor polymerization of monomers (concentrating reactants).
Hypothetical Steps in Naturalistic Origin:
Simple metabolism
Fourth step
Simple chemical reactions occur faster in aggregates because of the concentration gradient of reactants.
Hypothetical Steps in Naturalistic Origin:
Heredity information
Fifth step
Needed for precise reproduction. It is believed that RNA came first, then Protein, then DNA
Hypothetical Steps in Naturalistic Origin:
First true organisms
Sixth step
prokaryotic
About 3.5 BYA, probably heterotrophs, probably anaerobes.
Hypothetical Steps in Naturalistic Origin:
Photosynthesis
Seventh step
The first forms of life may have used H2S as an e- source. Cyanobacteria use water as e- source. Oxygen levels likely increased over time, ozone over time, creating proctective UV layer. Then terrestrial environments may have become available. Probably prokaryotic.
Hypothetical Steps in Naturalistic Origin:
Aerobic respiration
Eighth step
Organisms can take advantage of increasing O2 levels and become more efficient at ATP produciton. Still probably prokaryotic. Q: Where did the ATP come from required for glycolysis?
Hypothetical Steps in Naturalistic Origin:
Origin of eukaryotes
Ninth step
Endosymbiotic Theory - Chloroplasts and mitochondria may have been free-living organisms at one time. This is suggested because the both contain DNA and ribosomes. It is believed that they parasitized host cells to form eukaryotes.
Hypothetical Steps in Naturalistic Origin:
Evolutionary tree
Tenth step
Divergent evolution producing the various life forms.
