Origin of Life Flashcards
likely contained hydrogen (H₂) and helium (He), similar to the composition of other planets in the solar system. However, these gases were lost early in Earth’s history because:
● Earth’s gravity was too weak to retain such light gases.
● The planet lacked a magnetic field, so solar winds stripped away most of the atmosphere.
Earth’s first atmosphere
formed primarily through volcanic outgassing. Large amounts of gases were released from Earth’s interior, including:
- Water vapor (H₂O)
- Carbon dioxide (CO₂)
- Sulfur dioxide (SO₂)
- Carbon monoxide (CO)
- Sulfur (S₂)
- Chlorine (Cl₂)
- Nitrogen (N₂)
- Hydrogen (H₂)
- Ammonia (NH₃)
- Methane (CH₄)
Earth’s second atmosphere
Ocean Formation:
Geological evidence of early oceans includes:
_________ - which form when lava cools rapidly underwater.
_________ - indicating ancient ocean environments.
Pillow basalts
Deep marine sediments in greenstone belts
Atmospheric Structure
- Lowest layer, where weather occurs.
- Temperature decreases with altitude.
Troposphere
Atmospheric Structure
- Contains the ozone layer, which absorbs UV radiation.
- Temperature increases with altitude due to ozone absorption.
Stratosphere
Atmospheric Structure
- Coldest atmospheric layer, where meteors burn up.
- Temperature decreases with altitude.
Mesosphere
Atmospheric Structure
- Absorbs high-energy radiation from the Sun.
- Contains the ionosphere, which is important for radio communication.
- Temperature increases with altitude.
Thermosphere
Atmospheric Structure
- Outermost layer, where atmospheric gases gradually escape into space.
Exosphere
This theory suggests that early Earth’s atmosphere contained gases like methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O). These gases reacted in the presence of lightning or ultraviolet (UV) radiation, forming simple organic molecules.
Primordial Soup Hypothesis (Oparin-Haldane Theory)
In 1953, Stanley Miller and Harold Urey tested the Primordial Soup Hypothesis by simulating early Earth conditions in a laboratory. They exposed a mixture of water, methane, ammonia, and hydrogen to electric sparks, mimicking lightning. After a few days, they found amino acids, which are essential for life, proving that organic molecules could form naturally under early Earth conditions.
Miller-Urey Experiment
Another theory suggests that organic molecules originated in deep-sea hydrothermal vents, where mineral-rich, hot water provides energy for chemical reactions. The presence of compounds like hydrogen sulfide (H₂S) and iron could have facilitated the formation of amino acids and other organic molecules, potentially leading to the development of early life.
Hydrothermal Vent Hypothesis
Some scientists propose that organic molecules were delivered to Earth by comets, asteroids, or meteorites. The discovery of amino acids in the Murchison meteorite, which landed in Australia in 1969, supports this idea. If organic molecules formed in space and were transported to Earth, life may have had an extraterrestrial component in its origin.
Panspermia Hypothesis (Extraterrestrial Origin)
Key Organic Molecules and Their Roles:
Proteins (which perform cellular functions and provide structure)
Amino Acids
Key Organic Molecules and Their Roles:
RNA & DNA (which store and transmit genetic information)
Nucleotides
Key Organic Molecules and Their Roles:
Cell Membranes (which create barriers and protect cellular contents)
Lipids
Key Organic Molecules and Their Roles:
Energy Storage (which provide energy for cellular processes)
Carbohydrates
are large, complex, biological molecules and most of them are polymers.
Macromolecules
are formed by monomers, or single molecules, joined together in a long chain by covalent bonds.
Polymers
