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Evolution of Prokaryotic Cells and Early Life Forms

This text provides insights into the evolution of prokaryotic cells and early life forms, including the appearance of bacterial capsules, cell walls, and various cellular structures. It also explores the origin of photosynthetic cells and the potential earliest appearance in the fossil record. The text covers important concepts such as self-assembly, reproduction, and absorption of RNA.

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Evolution of Prokaryotic Cells and Early Life Forms

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  1. 20 200 Number of amino acids Mass of amino acids (mg) 10 100 0 0 1953 2008 1953 2008

  2. 0.4 Precursor molecules plus montmorillonite clay Relative turbidity, an index of vesicle number 0.2 Precursor molecules only 0 40 0 60 20 Time (minutes) (a) Self-assembly 1 m Vesicle boundary 20 m (b) Reproduction (c) Absorption of RNA

  3. 30 m 5 cm 10 m Stromatolites Nonphotosynthetic bacteria Possible earliest appearance in fossil record Cyanobacteria 1 4 3 2 0 Time (billions of years ago)

  4. 1 m 1 m 3 m (a) Spherical (b) Rod-shaped (c) Spiral

  5. Bacterial capsule Bacterial cell wall Tonsil cell 200 nm

  6. Fimbriae 1 m

  7. Flagellum 20 nm Filament Hook Motor Cell wall Peptidoglycan layer Plasma membrane Rod

  8. 1 m 0.2 m Respiratory membrane Thylakoid membranes (a) Aerobic prokaryote (b) Photosynthetic prokaryote

  9. Chromosome Plasmids 1 m

  10. Photosynthetic cells Heterocyst 20 m

  11. 1 2 3 4 5 Phage DNA Phage infects bacterial donor cell with A and B alleles. A B Donor cell Phage DNA is replicated and proteins synthesized. A B Fragment of DNA with A allele is packaged within a phage capsid. A Crossing over Phage with A allele infects bacterial recipient cell. A A− B− Recipient cell Recombinant cell Incorporation of phage DNA creates recombinant cell with genotype AB. A B−

  12. 1 m Sex pilus

  13. 1 2 3 4 Bacterial chromosome F plasmid F cell (donor) F cell Mating bridge F cell F− cell (recipient) Bacterial chromosome Recipient cell is now a recombinant F cell. Broken strand peels off and enters F− cell. One strand of F cell plasmid DNA breaks at arrowhead. Donor and recipient cells synthesize complementary DNA strands.

  14. Domain Eukarya Eukaryotes Korarchaeotes Euryarchaeotes Domain Archaea Crenarchaeotes UNIVERSAL ANCESTOR Nanoarchaeotes Proteobacteria Chlamydias Spirochetes Domain Bacteria Cyanobacteria Gram-positive bacteria

  15. 2 m

  16. 1.0 0.8 0.6 Uptake of K by plants (mg) 0.4 0.2 Seedlings growing in the lab 0 No bacteria Strain 3 Strain 1 Strain 2 Soil treatment

  17. 5 m

  18. (b) (a)

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