The diversity of genomes and the tree of life Chapter 1 The diversity of genomes and the tree of life
Living organisms obtain energy in different ways - Organotrophic - Phototrophic - Lithotrophic - aerobic - anaerobic
Some Cells Fix Nitrogen and Carbon Dioxide for others
The greatest biochemical diversity is seen among procaryotic cells
The phototrophic bacterium Anabaena cylindrica
A lithotrophic bacterium, Beggiatoa, gets its energy by oxidizing H2S and can fix carbon even in the dark
The tree of life has three primary branches: Bacteria, Archaea, and Eucaryotes
The three - kingdom classification of organisms as proposed by Haeckel in 1866
Classification of organisms into five kingdoms first proposed by Whitaker in 1959. The five kingdoms were: Animalia, Planta, Fungi, Protista, and Monera
Since molecular structures and sequences (of bases in DNA/RNA and of amino acids in proteins) are more revealing of evolutionary relationships than classical phenotypes (particularly among microorganisms), beginning in the 1950s, the basis for the definition of taxa shifted from the organismal to the cellular to the molecular level
Universal phylogenetic tree in rooted form showing the three domains – Bacteria, Archaea, and Eucarya
Some genes evolve rapidly; others are highly conserved
Most Bacteria and Archaea have 1000 - 4000 genes
Aug 31, 2004
Microbial Genomes – August 30, 2005
Microbial Genomes – complete; August 30, 2005
As of September 5, 2007
Eukaryotic Genomes – August 30, 2005
As of September 5, 2007
As of September 5, 2007
New genes are generated from preexisting genes
47% of the genes in this bacterium have one or more obvious relatives Gene duplications give rise to families of related genes within a single cell Families of evolutionarily related genes in the genome of Bacillus subtilis 47% of the genes in this bacterium have one or more obvious relatives
different evolutionary pathways Paralogous genes and orthologous genes: two types of gene homology based on different evolutionary pathways Orthologs - genes in two separate species that derive from the same ancestral gene in the last common ancestor of those two species Paralogs - related genes that have resulted from a gene duplication event within a single genome, and are likely to have diverged in their function Homologs - genes that are related by descent in either way
different evolutionary pathways Paralogous genes and orthologous genes: two types of gene homology based on different evolutionary pathways
Genes can be transferred between organisms, both in the laboratory and in nature
Horizontal gene transfers in early evolution
The function of a gene can often be deduced from its sequence
More than 200 gene families are common to all three primary branches of the tree of life
Mutations reveal the functions of genes
Spotlight on E. coli We have a more thorough knowledge of the working of E. coli than of any other living organism, yet we hardly understand everything about this bacterium
The major features of eucaryotic cells
Eucaryotic cells may have originated as predators
Eucaryotic cells evolved from a symbiosis
Eucaryotes have hybrid genomes
Eucaryotic genomes are big