Author: FLVS
Last saved by: Windows User

Biology Notebook: 01.03 Earth’s Early Atmosphere 
Objectives:
•	Describe the conditions on Earth billions of years ago
•	Summarize theories of how life began on Earth
•	Describe the relationship between organic compounds, nucleotides, RNA, and a universal genetic code
•	Explain the connection between the beginning of life and the universal genetic code of almost all organisms

Key Questions and Terms | Notes
Describe early Earth. | It had primordial atmosphere with vast pieces of landmasses and ocean with bacteria as the only living organism.
What was Earth’s early atmosphere made of? | Mostly carbon dioxide and no oxygen.
Compare and contrast early Earth and modern Earth. | Both contained large landmasses and oceans. The early earth’s atmosphere had no oxygen unlike the modern earth.
What are organic molecules? | Molecules with carbon atoms attached to hydrogen atoms.
Why are scientists interested in the origin of organic molecules? | It explains the origin of life.
What are two examples of organic molecules that scientists think first formed? | Nucleic acids and carbohydrates
Miller and Urey
What hypothesis did Miller and Urey want to test? | Organic molecules needed to support life formed from inorganic compounds.
What did their experiment produce? | It found earth atmosphere was able to produce amino acids that are life’s building blocks.
What did they add to make it like Earth’s early atmosphere? | Hydrogen, steam, methane, and ammonia as well as electrical discharge
Where did they think that the energy came from to cause this process to occur? | Lightening
What was formed? | Amino acids
What is the most important reason that these theories work? (What was missing in Earth’s early atmosphere that we have lots of in our current atmosphere?) | Oxygen
Multiple Hypotheses
What is another way that organic molecules might have arrived on Earth? | The Big Bang theory
How did large organic molecules form without the presence of enzymes? | Lightning sparked chemical reactions
What do all living organisms contain? | Carbon
What are the functions of DNA and RNA? | They carry genetic information
What is the RNA world hypothesis? | RNA was primarily a living substance based on its ability to function as both enzymes and genes
RNA World Hypothesis
Explain the importance of RNA molecules able to self-replicate. | It helps in the construction of identical copies of organisms.
Formation of Microspheres
What is a microsphere? | An environment formed by mixing water and salt to form proteinoids.

Microspheres are not cells, but they do share the following characteristics:

1. Permeable membranes
2. Microscopic

How do microspheres grow and what happens when it reaches an unstable size? | They grow when hot aqueous solutions of polypeptides are cooled.
How does the hypothesis of microspheres build off of the RNA world hypothesis? | Replicating RNA molecules transformed into DNA within the microspheres. When microspheres split, the genetic coding in self-replicating RNA would pass to the newly formed microspheres.
Life of Earth
How old do scientists believe was the earliest cell on Earth? | 3.22 billion years
What were the earliest types of cells? | Microbes
What caused the oxygen to accumulate in the atmosphere? | Microbes such as cyanobacteria and blue-green algae carried out photosynthesis to produce oxygen.

The four major processes needed for the origin of life on Earth (put each one in 5 words or less):

1. Synthesis of simple organic molecules
2. Assembly of these molecules (polymers)
3. Polymers start to replicate
4. Packaging of these molecules

Sample questions:
According to the RNA Hypothesis it is believed that all living things came from a common ancestor.  What evidence supports this theory? B
A.	The RNA molecule has the same molecule controlling its replication in all living things.
B.	The RNA molecule is able to self-replicate.
C.	The RNA molecule is an inorganic molecule.
D.	The RNA molecule is considered the master copy of all living things.
Which best describes the atmosphere of the early Earth?   A
A. Little or no oxygen, mostly carbon dioxide, water vapor and nitrogen
B. Little or no carbon dioxide, mostly oxygen, water vapor and nitrogen
C. Little or no water vapor, mostly oxygen and carbon dioxide with some nitrogen
D. Large amounts of hydrogen cyanide with low amounts of carbon dioxide and oxygen