Lecture 3: Origin of Life
Age of the Earth.
- 4.6 billion years old
Age of start of life on Earth.
- 4 billion years – stromatolites – type of bacteria
Domains of life.
Characteristics of LUCA
- LUCA was not first form of life, just ancestor of every living thing on planet
- Many branches 4 million years ago before LUCA
- Perhaps things that came before died out early
Characteristics shared by all domains of life.
- 1. Cells made of lipids
- 2. Genetic system based on DNA
- 3. DNA to RNA to Protein transfer
- 4. Common system of protein assembly
- 5. ATP
- 6. Glucose and Glycolysis
Reason why the term “prokaryote” is inappropriate.
- This is a bad term because it says that bacteria and archaea are evolutionary
related and they are not
- Also pro means before which means prokaryotes means” before nucleus” but
there is no evidence to suggest LUCA didn't’t have nucleus
Reductive evolution explanation for rise of bacteria and archaea.
- LUCA proto-eukaryote? Had nucleus – fair amount of complexity
- Complexity lost in bacteria and archaea – reductive evolution – advantage to
get rid of things – streamlining
Advantages of evolutionary simplification (streamlining).
- Bacteria can then reproduce faster and evolve faster
- This is why bacteria and archaea are found in extreme conditions –
Relationship between homochirality and life
- All life: use L amino acids and D sugars
- Essential to life because of specificity ; eg. For