HL A2.1 The Common Ancestry of Life
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What is LUCA?
The Last Universal Common Ancestor from which all current life evolved.
What evidence supports LUCA?
Universal genetic code, ATP usage, ribosomes, and shared genes.
What does “genetic code is universal” mean?
The same codons code for the same amino acids in all organisms.
How many genes are thought to be shared with LUCA?
Approximately 355 conserved genes.
What domains of life exist today?
Bacteria, Archaea, Eukarya.
Why are hydrothermal vents a likely origin for LUCA?
They provide chemical energy, hydrogen, carbon dioxide, minerals, and stable temperatures.
What evidence supports hydrothermal vent origins?
Genetic analysis of protein-coding genes and modern extremophiles.
How do scientists date early life and LUCA?
Fossils (stromatolites), carbon isotope ratios, and molecular clocks.
What are stromatolites?
Layered sedimentary structures formed by cyanobacteria, evidence of early life.