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History of life notes
Early Earth
4.6 bya
- VERY (colliding meteorites, erupting volcanoes)
- Atmosphere was mostly nitrogen, carbon dioxide, water vapor, methane,
ammonia but ___ no oxygen__!!!
4.4 bya
- Earth _cools__
- water vapor condenses into ___rain__ creates oceans (where the first life will form)
Evidence that we do have!
Fossils = evidence of an organism that lived long ago and show the great diversity of life
(Examples:
A person who studies fossils is called a _paleontologists__ (just like Ross on Friends!)
How is a fossil made?
- after an organism is buried, the sand and clay around it harden to form
___sedimentary rock___. Then erosion brings the fossil to the surface
Dating Fossils
1. Relative Dating- older rocks/fossils are on the _bottom__ younger ones are on top
2. Absolute Dating (also called radiometric dating)- measures the amount of
__radioactive___ substance left in the rock or organism and determines its actual
age
By examining rock layers and dating the fossils, scientists have been able to put together
a chronology, or calendar of Earth’s history called the ____GEOLOGIC TIME
SCALE____. (see left page)
Origin of Life
Cell Theory
1. all living things are made of ___cells_____
2. cells are basic unit of _______structure________ &
_______function_________
3. All cells come from pre-existing cells.
What is the big question this theory raises?
1. Where did the first cell come form
2. What can be observed now if it happened so long ago
- The initial belief was that life was created through __________spontaneous
generation____ (abiogenesis).
Example: a piece of decaying meat produces maggots
Disproving Spontaneous Generation
1.
Francesco Redi was the first to disprove spontaneous generation in the 1600s.
History of life notes
Although Redi was able to disprove that large organisms did not simply appear,
many scientists thought that microorganisms (bacteria) were so numerous and
widespread that they must arise spontaneously- probably from a vital force in the air.
2. Louis Pasteur in the mid 1800’s designed an experiment that disproved the
spontaneous generation of ___microorganisms___.
From this time on ___BIOGENSIS___ , the idea life comes from life holds true.
(Ex. Humans give birth to humans, mice to mice, etc.)
But…. How did the very first life form that start this chain reaction?!!!
The current theory is that life began in the ___oceans___.
Oparin’s hypothesis: Energy from the __sun and lightening_____ triggered chemical
reactions with the vapors that were present in the early atmosphere to produce
____________small organic molecules______________________________ . Then, the
rain washed the molecules into the _____ocean__ to create what is called the
___primordial soup___ (place of the origin of life).
History of life notes
PROOF??
1953- Stanley Miller and Harold Urey tested the hypothesis by simulating the conditions
of early Earth in a lab.
Simple Molecules to Complex molecules?
- experiments were done to prove that simple molecules like ___________amino
acids_________ when heated without oxygen link up to form
________proteins_________ (complex molecules)
Complex Molecules to Cells?
- Sidney Fox showed how amino acid chains will form __protocells___
Evolution of Cells
1st cells = prokaryotic, anaerobic and heterotrophic
2nd cells = autotrophic prokaryotes
3rd cells = photosynthesizing prokaryotes
First organisms were prokaryotes
2 types
– Archaebacteria – bacteria that live in ___harsh environments_, and more
closely related to early prokaryotes
– Eubacteria- all other bacteria
Endosymbiotic theory
Pre-eukaryotic bacteria engulfed another
– (similar to mitochondria or chloroplast)
History of life notes
Eukaryotic organisms formed much ___later_______________ than prokaryotes
Summary