Lecture 20 Flashcards
What did Lord Rutherford discover about the Earth’s age?
The recorded rate of Earth’s heat loss and found the minimum and maximum age of the Earth was between 20-400 million years old.
What is radioactive decay?
Some isotopes are stable, others are not. All elements have isotopes. Each wants to be more stable. Transformed spontaneously into a more stable isotope.
What is a half-life?
The time it takes for one half of the atoms of the original unstable parent element to decay into atoms of a new and more stable daughter element.
What was the margin of error after we added numerical ages to geological time?
A few thousand to one million years.
What are the dominant elements in life forms?
Carbon, Hydrogen, Oxygen, and Nitrogen (CHON). Sulphur and phosphorous are present in small amounts
What is the only element that remains after degradation?
Carbon.
What dominates in the composition of organisms?
H2O. Demonstrates that life evolved in water and began inorganically (small size, single-celled organisms)
What did Alexandr Ivanovic Oparin discover?
CHON molecules could have been formed before life begun to give rise to the first cells. Cells are too complex to have been formed without inorganic evolution first. Earth;s original atmosphere was reducing
What is a reducing atmosphere?
No free molecular oxygen. Toxic for animals and plants, Solar wind stripped away lighter elements, leaving heavier ones CHON molecules accumulated.
How were the first lifeforms produced?
Through inorganic molecules combining to form larger, organic molecules.
What was Primordial Soup?
Mix of water and larger organic/inorganic molecules that gave birth to first lifeforms. Primordial soup is not ALIVE.
What is the Isua Supercrustal Group?
Area of Greenland that contains the oldest sedimentary rocks on earth (3.8-3.7 billion years old). Rare oxides and carbonates that do not form layers. Not affected by metamorphism.
What do the graphite levels and calcium carbonate levels indicate in the Isua Supercrustal Group?
Graphite: Indicate organic origin, and vestiges of fossilized primordial soup. Substances of organic nature (not alive). Indicates that molecular oxygen existed
Calcium- Higher level of molecular oxygen in atmosphere.
When did the first life forms appear on Earth according to the Isua Supercrustal group?
3.8-3.7 billion years ago.
What did Miller and Urey demonstrate in 1953?
Simulated original conditions on Earth. Demonstrated that simple elements can react chemically to form simple organic CHON molecules. Obtained seven amino acids (organic compounds that aren’t alive)
