Exam 1 Essay

Submitted By apete29
Words: 983
Pages: 4

about 15 trillion cells make up a single adult human * about 180 thousand+ years ago was the first Homo sapiens to appear on earth * cell theory all cells come from preexisting cells theory of natural selection a hypotheses is not a theory but it is an explanation hypotheses how did life begin?
(theory/belief life is spontaneously generated) has not been proven so today we can state a fact that life is not spontaneously generated. a few centuries ago: people thought that new living things appeared all the time spontaneous generation refuted mid 1800s Louis Pasteur broth in flask is boiled to kill preexisting microorganisms as broth cools, condensing water collects, sealing the mouth of the flask if the neck is later broken off, outside air can carry microorganisms into broth conditions on early earth atmosphere: CO2; CH4; NH3; H2; N2; HCl; H2S; H2O similar to oxygen no free oxygen frequent storms with a lot of lightening frequent volcanic eruptions frequent meteor impacts
UV light from the sun no ozone layer earth before life arose earth is about 4.6 billion years old radiometric dating of meteorites and moon rocks life arose about 4.1 billion (4.1,000,000) years ago chemical traces in rocks 4 billion years old fossil bacteria in rocks 4 billion years old first single cell fossils – prokaryotes no spontaneous generation now, but must have happened then the experiment od miller and urey purified water gases of primeval atmosphere electric spark simulates lighting storm organic molecules appear after only a few days tried to create conditions of early life to determine how life began noticed water began to have pigment and determined it was the beginning of the building blocks of life organic molecules appeared but no life was successfully created how to assemble a living thing accumulation of organic molecules catalyze reactions (catalyze speeds up) proteins or RNA molecules reproduce from stored genetic information (DNA) separate the living thing from the outside environment the chicken or the egg? now: DNA RNA protein (central dogma of biology) need proteins to synthesize more DNA so how did earliest cells do it? ribozymes: means RNA enzymes
RNA molecule that can catalyze reactions, especially those involved in synthesis and processing of RNA itself conclusion: earliest cells used RNA to store information ribozymes to catalyze rxns viruses are NOT living things they can NOT reproduce on their own they use RNA hydrophobic hate (separate from each other) hydrophilic love (stick together) microshperes as proto-cells just add fat and protein to water then shake to mix water and fat add soap. in your body the soap figure is bile which is made in the liver and stored in the stomach. soap and bile
1 part hydrophilic
1 part hydrophobic proto = before protobionts systems that are considered to have possibly been the precursors to prokaryotic cells. if RNA is trapped inside, the system can use the RNA or select for it. * * water + elements + energy

* prebiotic soup * amino acids, mucleotides, lipids, sugars * microsphere like protocels surrounding more complex organic molecules like – RNA, carbohydrates, proteins, lipids

first prokaryotes

* ****only way we know how life came about on earth****
“family tree” of life phylogeny / evolutionary tree three groups(domains) of the tree eukarya archaea bacteria (prokarya) we as humans are in the eukarya domain because we are eukaryotes. as Homo sapiens we all share common ancestors prokaryotes cam first (about 2 billion years ago) single-celled – protists multicellular animals and fungi share the most common ancestors our most recent ancestor is ___________ possible test question are we closer related…