Lecture 10: Evolution of Eukaryotes
All morphologically complex organisms are eukaryotic - why?
- Morphology, cellular structure, processes are all complex.
- Bigger cells
o PM (plasma membrane) is not site of ox phos.
o Mitochondria is site of ox phos – generates ATP – lots of energy - can support larger
o Gene replication – low energy.
o Protein coding/synthesis – high energy – many more proteins.
- Show no tendency to form organelles – no complexity.
- Bacteria have stayed simple over evolution.
- Why don’t they if evolution is shown to be gradual?
o Cell grows bigger – need more ATP needed.
o Ox phos happens on plasma membrane – as bacterium grows – need more centers of
ox phos and electron transport chains on plasma membrane. Need centers for energy
b.c. as V of cell increases – protein and energy demand increases.
o Problem: as cell gets bigger - V increases much faster than SA. Can’t fill plasma
membrane with enough ox phos centers to fulfill ever-increasing V. Therefore,
bacteria size stays small.
- Bacteria: High PM SA/V – constrains size.
- Euk: Low PM SA/V
- Energy constrains complexity – need energy to synthesize proteins for complex functioning.
- Genome size is low energy so simple organisms can have very large genomes however it
takes energy to maintain genome size so proks keep genome size small.
- All morphological complex life is eukaryotic.
- All eukaryotes share common complex traits.
o Nucleus, trafficking, cytoskeleton, sex, phagocytosis, organelles, etc.
meaning of endosymbiosis, cyanobacteria, lateral gene transfer
- Mitochondrion and chloroplasts are derived from free-living prok cells (aerobic bacterium).
- Not derived from same place nuclear envelope is derived.
Cyanobacterium - Chloroplasts with which plants make food for themselves is actually a cyano living within
the plant’s cells.
- Endosymbiosis: cyano began to live in euk cells, making food for euk host in return for a
home – origin of euk mitochondria.
- Descendent for chloroplasts - identical photosynthetic structure to chloroplasts.
- Small, unicellular, oldest known fossil, oxygen atmosphere generated by numerous
cyanobaterium in archaean era.
origin of endomembrane system, nuclear membrane, ER etc.
- Includes nuclear envelope and ER
- Derived from infolding of plasma membrane
- Nucleus separates genomic info.
o Nuclear envelope – regulates transcription and replication of DNA. Eg. Transcription
- Nuclear envelope and ER are distinct from Endosymbiosis
origin of mitochondria and chloroplasts
evidence supporting theory of endosymbiosis
- 1. Morphology – looked the same - mitochondria and ch