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1.4 Cell Theory Part 2 - Origin of Cells - Coggle Diagram
1.4 Cell Theory
Part 2 - Origin of Cells
Cells can only be formed by division of pre-existing cells
Evidence: Reproduction through "binary fission" (Remak, Virchow, Kolliker)
"Omnis cellula e cellula" (Virchow)
Evidence: Pasteur's swan-neck flask experiments show no cells produced in a dead broth
The first cell must have come from non-living material
Bilayer membranes would have naturally formed from phosophilids and other
amphipathic
carbon compounds
Inheritance from genes requires DNA that may have evolved from RNA
Basic building blocks like sugars and amino acids can be made from methane, hydrogen and ammonia with electricity
Miller and Urey experiment
Polymers can be formed from these carbon-based compounds
Endosymbiosis theory
Eukaryotic cells evolved from prokaryotic organisms
Different evolutionary pathways for plant and animal cells
Mitochondria are thought to once have been free-living prokaryotic organisms that developed aerobic respiration
Have their own genes in plasmid (circular) DNA like prokaryotes
Have 70S ribosomes with prokaryote-like sizes and shapes
Reproduce by division, transcribing the DNA and mRNA to make their own proteins
Some larger anaerobic prokaryotes took in smaller mitochondria with endocytosis and combined with them to breathe, rather than killing and digesting them
Formed a symbiotic (mutualistic) relationship - the smaller prokaryotes were fed via the larger one and the smaller ones supplied energy that the larger one could use in return
Chloroplast evolution fits this model too, initially a prokaryote that could photosynthesis taken in by another prokaryote; they have prokaryote-like genes, ribosomes, etc.
First known eukaryote and multicellular organism is Bangiomorpha pubescens, a red algae discovered in 1.2 billion year old rocks from Northern Canada. Reproduces sexually too with male/female gametes.