Lecture 1: Origin of Life Flashcards
How old is the Earth believed to be by geologists and astrophysicists?
What is their theory based on?
4.6 billion years old
Based on measurements of radioactive decay of uranium to lead in rocks
How is the geological time scale separated?
Separated into Eras
Eras separated into periods
Periods separated into epochs
What are the 4 eras and how long ago were they?
- Precambrian: 4.6 billion years ago to 541 million
- Paleozoic: 541 million to 252 million
- Mesozoic: 252 million to 66 million years ago
- Cenozoic: 66 million years ago to present
Notice each era gets smaller and smaller
Much more is known about the more recent past when compared to the distant past
How long ago did oxygen accumulate in the atmosphere?
2.5 to 2.3 billion years ago
When was the first fossil dated to?
3.5 billion years ago
Vast majority of earth’s history dominated by single-celled organisms
What was the earth originally and how long did it take to cool?
Earth was originally molten rock, with hot hydrogen gases volcanoes and lightning. It took about 600 million years for the earth to cool.
Known as the Hadean period
What are the five characteristics of life?
- Life uses energy
- Organisms consist of cells
- Living organisms contain and process information
- Life can replicate itself
- Life evolves
What are the 4 discrete steps that scientists say the origin of life must have occurred by?
- Abiotic synthesis of complex organic molecules (proved in Miller-Urey experiment)
- Formation of polymers (clay)
- Formation of protobionts (spheres made from proteins and/or lipids
- The origin of hereditary material: life must have replication of heredity material
What did Miller and Urey do?
They performed an experiment in which they mimicked the conditions of early abiotic Earth and proved that complex organic molecules can form without oxygen. (Literally does not form when oxygen is added)
What is the role of clay in the formation of polymers?
Clay acted as a gathering ground for concentrating organic compounds.
Clay contains many compounds with ionic charges that could attract organic molecules.
Clay contains iron and zinc which help facilitate polymerization reactions.
What is a protobiont and what is the most important protobiont?
Protobionts are spheres that are made spontaneously from macromolecules in solution.
The most important protobiont is likely the liposome made of lipid bilayers. (similar to cell membranes)
Can be made of proteins and/or lipids
The lipid bilayer can manipulate its environment which is an important characteristic of life.
How long ago was the first evidence of life/origin of life?
3.6 Billion Years ago
What did oxygen react with in early earth and what does this prove?
Oxygen reacted with hydrogen gas to make water as well as carbon to make CO2 and CO. This proved that early earth contained very little oxygen.
What did Miller and Urey do? What did they prove? What happens if you take away oxygen and where did the energy for abiotic synthesis come from?
Miller and urey performed an early experiment to mimic the conditions of early abiotic earth. They proved that it is possible to form organic molecules abiotically. Without oxygen, the experiment does not work. Energy probably came from the sun since there was no oxygen to block UV rays.
Why do many scientists believe that RNA was the original hereditary material?
- It can be formed in experiments, suggesting it was in the primordial soup
- It has been shown to replicate itself in thhe presence of zinc (in clay)
- It contains hereditary information like DNA
- It has catalytic properties that can help form macromolecules.
