Lecture 15 Flashcards
Phylogeny
Evolutionary history of organisms- how organisms / species are related
Demonstrated through trees
First trees were base on species appearances (morphological differences) and features and guesses about when they might have split phylogenetically
What organelle is present in all life and has its own DNA
Ribosome
Made of 2 subunits. Each composed of protein and ribosomal RNA (rRNA)
Tree of life Carl woese
Carl woese suggested using ribosomal RNA (rRNA) to investigate organismal differences to develop a more accurate tree of life
Showed life could be grouped into 3 domains:
Bacteria, archaea, Eukarya
This expanded to use of DNA and rRNA as key molecular tools
Genetic phylogenies are much more objective
Why are there likely only 2 domains
Samples from hydrothermal vents found a species of archaea that bridged the gap between eukaryoties and archaeans
Means eukaryotes must have branched from archaea
Luca
Last universal common ancestor
3+ billion years ago
Comparison of 1800 bacterial and 135 archaeal genomes yielded 355 common proteins. These are probably proteins that were in LUCA
Based on proteins found we can conclude LUCA was
Anerobic (lived without O2)
Fixed CO2 into organic molecules
Used reverse citric acid cycle
Used H2 as a source of hydrogen
Converted nitrogen into ammonia
Lived in a hot environment
Luca wasn’t the first form of life to develop so why is it important
All present day organisms on earth share a common set of features
Cells defined by a membrane composed of a bilayer of lipid molecules
Genetic system based on DNA
system of information transfer: DNA TO RNA TO protein
Ribosomes as central feature of a protein assembly machinery that uses the information in mRNA and tRNA to produce peptide chains from a pool of amino acids
Reliance on proteins as the major structural and catalytic molecule
Use of ATP as currency of chemical energy
Common pathways of energy transformation (glycolysis, substrate lvl phosphorylation, Chemiosmosis)
Where did oxygen come from
Original photosynthetic organisms used light to extract hydrogen from hydrogen sulfide. Which was used to fix co2 into carbohydrates
Cyanobacteria- able to oxidize water which is more available. Allowing the bacteria to thrive
-explosion of ^ turned the planet green
2H2O + light -> 4H+ + 4e- + O2
Once O2 was available aerobic respiration could evolve
Anerobic respiration provides 2ATP molecules per glucose. While Aerobic provides over 30
More energy available means cell can become larger and more complex
Theory of endosymbiosis
Energy transducing organelles. Chloroplasts. And mitochondria are thought to to have been derived from free living prokaryotic cells
Prokaryotic host cells engulfed the endosymbionts, becoming inseparable parts of the same single celled organism
Mitochondria descended from
Aerobic respiration
Chloroplast descended from
Cyanobacteria
Morphology endosymbiosis
Shape and size like that of prokaryotic cells
Reproduction endosymbiosis
Divide by binary fission in the same way as prokaryotic cells engulfed
Genetic information endosymbiosis
Contain their own DNA with protein coding and non coding genes essential for organelle function
Transcription and translation endosymbiosis
Contain complete transcription and translational material
Electron transport endosymbiosis
Like prokaryotic cells. Mitochondria and chloroplasts have electron transport chains
Sequence analysis endosymbiosis
Show that these organelles belong on the bacterial branch of the tree of life
Vertical gene transfer
Genetic inheritance from one generation to the next within a species
Horizontal gene transfer
Genetic inhertixande between unrelated species
Shaped evolution of eukaryotic cells
