What is the current idea about the age of the Earth?
4.6 billion years ago
The early Earth was primarily volcanic.
What gases were present in the early Earth’s atmosphere?
- Hydrogen sulfide
- Methane
- Carbon dioxide
The atmosphere had little to no atmospheric oxygen.
What is the significance of the reduced state of the early atmosphere?
No atmospheric oxygen
This prevented redox reactions from occurring.
What external energy sources provided activation energy for reactions in early Earth?
- Lightning
- Volcanic activity
These sources contributed to the formation of a ‘chemical soup’.
What was the purpose of the Miller-Urey experiment?
To demonstrate how early atmospheric gases could develop complex, life-forming molecules
It simulated conditions of early Earth.
In the Miller-Urey experiment, what did the upper chamber represent?
The atmosphere
It contained gases that simulated early Earth’s conditions.
What did the lower chamber of the Miller-Urey experiment represent?
The oceans
It contained boiling water and gases.
What was produced in the collection trap of the Miller-Urey experiment?
Amino acids
These are essential building blocks of life.
What evidence supports the idea that reducing environments led to complex molecules?
Existing deep ocean pockets inhabited by sulfur bacteria
These communities are models of early Earth conditions.
What is chemoautotrophy?
Organisms use inorganic compounds to drive ATP synthesis
This process could have contributed to the start of complex life.
What are the oldest known specimens of prokaryotes estimated to be?
32-34 billion years old
Many prokaryotes are found in stromatolites, which are formed by cyanobacteria that trap layers of sediment.
What process do cyanobacteria perform that contributes to the atmosphere?
Photosynthesize and produce oxygen
This process eventually leads to oxygen becoming part of the atmosphere, allowing oxidation to occur.
What significant event occurred 25 billion years ago related to oxygen?
Great Oxygenation Event
Oxygen accumulated in the atmosphere, with a significant increase occurring 850 million years ago.
What initially reacted with oxygen before it accumulated in the atmosphere?
The ocean, iron, and sulfur
This reaction explains the gap between the emergence of photosynthesis and the abundance of O2 in the atmosphere.
What type of photosynthesis was used for a long time before the Great Oxygenation Event?
Anoxygenic photosynthesis
This type of photosynthesis does not produce oxygen as a byproduct.
What is the leading theory regarding the origin of eukaryotes?
Endosymbiosis between two prokaryotes
An archaea-like organism is thought to have formed a mutualistic relationship with a bacteria-like organism.
What evidence supports the endosymbiotic theory regarding organelles?
- Single circular DNA (separate from nucleus)
- 70S ribosomes
- Binary fission
Organelles like chloroplasts and mitochondria share these properties with prokaryotic organisms.
What is the Cambrian Explosion characterized by?
Rapid appearance of many groups of organisms and emergence of features present in modern groups
This period marks a significant increase in the diversity of life forms.
Prior to the Cambrian, which period existed that featured organisms with vastly different structures from modern organisms?
Ediacaran period
Organisms from this period had unique characteristics compared to those that emerged later.
What ocean chemistry factor allowed organisms to have shells during the Cambrian period?
Ocean chemistry allowed for the formation of shells
This change contributed to the development of various hard-bodied organisms.
What type of preservation is noted for the Cambrian period?
Abnormally high amount of soft body preservation
This includes evidence of arthropods, echinoderms, and various extinct forms.
List some of the modern features that emerged during the Cambrian period.
- Heads
- Legs
These features are significant in the evolution of modern organisms.
Which groups of organisms are mentioned as emerging during the Cambrian period?
- Anthropoda
- Nematoda
- Mollusca
- Annelida
- Brachiopoda
- Chordata
- Echinodermata
- Ctenophora
- Hydrozoa
- Porifera
These groups represent a wide variety of life forms that appeared during this time.
What are some factors that caused the Cambrian Explosion?
- Hox genes
- O2 levels
- Genetic diversity
- Change in ocean chemistry
- Evolution of grazing and reduction of algal mats
These factors contributed to the rapid diversification of life.
