37 terms

History of Life

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Fossil Record
Where evidence for the history of life is found
Two Types of Fossil Dating
Relative Dating
Radiometric Dating
Relative Dating
Comparative dating (based on layers of rock)
Uses index fossils
Doesn't give a specific age in years
Radiometric Dating
Measures radioactive isotopes
Dates rocks and therefore the fossils it contains
Half-Life
Period of time that it takes for ½ of the radioactive isotope to decay
Geologic Time Scale
Why can't divine creation be considered?
Divine creation cannot be tested by science, so it falls outside the realm of science`
Most important fact about early atmosphere
Next to no oxygen
4-Stage Hypothesis of Life
1.) Inorganic chemicals form simple organic molecules in the primitive ocean
2. Formation of complex organic molecules
3. Formation of self-replicating molecules that make inheritance possible
4. Membrane formation
Oparin's Primordial Soup
Inorganic compounds, using sun or lightning (energy), bonded to create organic molecules
Miller and Urey's Experiment
Tested Oparin's Primordial Soup

Set up a flask with gases representing the primitive atmosphere
Electric sparks represented lightning
After several days amino acids formed
1995: experiment done- cytosine and uracil formed
Problems with the Primordial Soup Model
1. Takes too long for molecules to form
2. No oxygen means no ozone-
UV light would destroy gases needed to produce molecules needed for life
Lerman's Bubble Theory
Chemical reactions occurred in bubbles in the ocean
How did the bubble theory solve the Primordial Soup Model?
1. Reactions faster since molecules concentrated in bubbles
2. Gases protected from UV light
RNA may have evolved before DNA because...
1. can act like enzymes
2. can form simple proteins
3. can replicate
4. stores genetic information
5. has been found to form as water is frozen and nucleotides
are pushed into spaces between water crystals
Hypotheses for formation of the membrane
Lipid membrane hypothesis
Protenoid microspheres
Lipid membrane hypothesis
Liposomes- lipid molecules - form spheres around other molecules
Microspheres
tiny bubbles
Protenoid microspheres
Tiny bubbles form diluted solutions with organic compounds that are dropped onto hot sand, rock, or clay.
Name of the first Photosynthesizing Autotrophic Prokaryotes
Cyanobacteria
Early Cellular Evolution
Heterotrophic Anaerobic Prokaryote (Heterotroph Hypothesis)
to
Chemosynthesizing Anaerobic Autotrophs
to
Photosynthesizing Autotrophic Prokaryotes
What did Photosynthesizing Autotrophic Prokaryotes create?
oxygen
What did introduction of oxygen lead to?
Formation of ozone

More complex life

Mass Extinction of the anaerobic bacterium (except those that found an anaerobic habitat or are able to survive with oxygen)
Possible Explanations for Evolution of Eukaryotes
Endosymbiosis
Autogenous theory
Horizontal gene transfer theory
Endosymbiosis example
A large, prokaryotic predator cell ate aerobic bacteria, which weren't digested. The aerobe created excess energy and the large bacteria offered protection and resources. The small aerobe eventually became one with the other cell, resulting in the mitochondria.
Evidence for Endosybiosis
Mitochondrion and Chloroplasts have similar characteristics to those of bacteria

1.) Membranes
2.) DNA (in a circle)
3.) Ribosome (size, amongst other things)
4.) Reproduction (by binary fission)
5.) Cell Size
Autogenous Theory
folds in the membrane formed Eukaryotic organelles
Horizontal Gene Transfer Theory
Transfer of genetic material between cells led to more complex organelles
Conjugation
Transfer of genetic material between cells
Prokaryotic organiusms reproduce by...
Binary Fission
The very oldest eukaryotes reproduced...
asexually
Sexual Reproduction Advantage
Genetic diversity
Origin of Sexual reproduction
The transfer of genetic material between cells eventually lead to the formation of sex cells
Multicellular Organism Advantage
Allows for specialization and complexity
Possible -precursor to multicellular organisms
Unicellular organisms that live in large groups (ex. algae)
Ozone
O3 (So then what happened to create Ozone?)
Colonial Organisms and Aggregations
Unicellular organisms that live in large groups (ex. algae)