Eukaryotic Evolution Flashcards
What is LECA?
Last eukaryotic common ancestor- a complex cell with numerous compartments, organelles and at least 3000 new gene families
When did the eukaryotic cell arise?
Only once, 4 billion years ago
What are archezoa?
We’re thought to be evolutionary intermediates, but are actually ecological intermediates that became simpler
-> reductive evolution
Where do mitochondria derive from?
Facultatively anaerobic bacteria, eg:
• Rickettsia- close sequence similarity to aerobic mitochondria, but anaerobic
• Rhodobacter, Rhodopseudomonas, Rhodospirillin- more similar in physiology
What was the host cell for eukaryotes?
An archaeon- complex one- dynamic Actin cytoskeleton
This means there are only two primary domains
What is Lokiarchaeota?
Hydrogen-dependant autotroph
What caused reductive evolution of endosymbioant genomes?
They take longer to divide, so shorter genomes are selected for
-> unnecessary genes are lost
What is the defining signature of eukaryotes?
Genomic assymetry
Why are there only two sexes in reproduction?
Only the mother passes on mitochondria, ensuring mtDNA homoplasmy
What is the mechanism of selection for mtDNA homoplasmy?
• If genomes don’t match, respiration pathway doesn’t work:
- high reactive oxygen species (ROS) leak (superoxide, hydrogen peroxide)
- low ATP
- loss of cytochrome c
- > apoptosis
How could the effect of heteroplasmy on fitness led to speciation?
Hybrids between isolated populations lead to mitonuclear incompatibilities-> loss of fitness
What are the characteristics of a high apoptosis threshold?
Low aerobic capacity
High fertility
Fast ageing
Eg. Rats
What’s an example of a species with a low apoptosis threshold?
Pigeons
