BIOL 1202 : EXAM 1
Origins of Life
• as far as we know, life exists only on Earth
• life first appeared on earth about 4 billion years ago
• earth about 4.6 billion years old
• Earth cooled, rocks and water formed, life began to arise
◦ hypothesis as to how life arose
• Miller and Urey replicated conditions of early earth
◦ water boiled in bunsen burner and vaporized
◦ vapor passed through an electric spark chamber (simulated lightning)
◦ goes into chamber with gases present on early earth
◦ a few days later, the water that was condensing into a flask had a pigment to it
due to organic molecules
◦ did not create life, but organic molecules were an important discovery
• spontaneous generation of life - random emergence of life
• ~100 million species on Earth
History of life on earth
• people originally thought that living things appeared all the time
◦ theory of spontaneous generation of life
• Louis Pasteur refuted spontaneous generation in mid 1800s
◦ sterilized broth in a flask
◦ sealed off flask
◦ life did not appear in the sterilized flask
◦ when it was exposed to the air, life began to appear
• cell theory - all existing cells come from previously existing cells
Conditions on earth earth
• atmosphere lacked O2 and O3
• sources of energy included:
◦ frequent storms
◦ volcanoes
◦ meteors
◦ UV light from the sun
• Earth determined to be about 4.6 billion years old
◦ radiometric dating of meteorites and moon rocks
• life arose about 4 billion years ago
◦ found from chemical traces in rocks
◦ fossilized bacteria in rocks found from about 3.5 billion years ago
◦ no spontaneous generation now, must have happened at some point
Rate of Decay of 40K to 40Ar
• Potassium 40 naturally decays to 40Ar
• half life is 1.25 billion years
◦ half life is the amount of time for 50% of a substance to decay
• If you start with 20 lbs of 40K, after 1.25 billion years, 10 lbs remain, after 2.5 billion 5
remain, etc.
How to assemble a living thing
• accumulation of organic molecules
• catalyze reactions
◦ done by enzymes and RNA molecules
• reproduce from genetically stored information
• separate the living thing from the outside environment
◦ membrane composed of phospholipid bilayer
RNA
• DNA --> RNA --> proteins
◦ RNA thought to have arisen first
• ribozymes - RNA that acts an enzyme
◦ especially acts in reactions involving the synthesis and processing of RNA itself
◦ earliest cells used RNA to store info
Rise of life
• life evolved from one original species
1. water + elements + energy
2. probiotic soup of amino acids, nucleotides, lipids, and sugars
3. microsphere like protocells surrounding more complex organic molecules like
RNA, carbohydrates, proteins, and lipids
4. first prokaryotes
5. evolution by natural selection to other species
Family tree of life
• domains: Eukarya, Bacteria, and Archaea
• bacteria arose first
◦ lead to Eukarya and Archaea
• all life is related to one another through a common ancestor
• man has been around for ~200,000 years
• diversity is due to evolution by natural selection
Science
• explanation, observation, identification, and experimentation in regards to phenomena
• activities restricted to a class of natural phenomena
• theory - a general explanation of natural phenomena developed through extensive and
reproducible observations
• hypothesis - tentative explanation of observations
◦ "educated guess"
Charles Darwin
• first to publish the current theory of evolution by natural selection
• wrote On The Origin of Species by Natural Selection
• sailed around the world in his early 20s collecting data
• two main points in book:
◦ evolution occurs in populations (individuals do not evolve)
Document Summary
History of life on earth: people originally thought that living things appeared all the time, louis pasteur refuted spontaneous generation in mid 1800s, cell theory - all existing cells come from previously existing cells. Conditions on earth earth: atmosphere lacked o2 and o3, sources of energy included, earth determined to be about 4. 6 billion years old, life arose about 4 billion years ago. Uv light from the sun theory of spontaneous generation of life radiometric dating of meteorites and moon rocks half life is the amount of time for 50% of a substance to decay remain, etc. membrane composed of phospholipid bilayer. How to assemble a living thing: accumulation of organic molecules, catalyze reactions done by enzymes and rna molecules, reproduce from genetically stored information, separate the living thing from the outside environment. Rna: dna --> rna --> proteins, ribozymes - rna that acts an enzyme. Rise of life: life evolved from one original species.
