Origins of Life and Biodiversity PDF

17.1 Origins of Life  Before the first cells could evolve, several fundamental conditions were required: Essential elements: to compose organic molecules Carbon nitrogenOxygenSulfur Continual source of energy: mainly nuclear fusion reactions within the Sun photosynethiss...

17.1 Origins of Life  Before the first cells could evolve, several fundamental conditions were required: Essential elements: to compose organic molecules Carbon nitrogenOxygenSulfur Continual source of energy: mainly nuclear fusion reactions within the Sun photosynethiss Temperature range permitting liquid water, but not too hot: because otherwise, https://www.the-scientist.com/news-opinion/on-the- metabolic reactions cease or macromoleculaes origins-of-life-35775 fall apart. 1  Early Life  The earliest forms of life for which we have clear fossil evidence are bacterial communities called stromatolites. Masses of sedimentary layers of limestone (CaCO3) that are 3.4 billion years old fossil 2 Earth’s Atmosphere  Volcanic activity releases gases like carbon dioxide and nitrogen. Formed first atmosphere, which was thin and primarily composed of CO2  Earth developed living organisms that filled the atmosphere with gaseous N2 and O2. https://en.wikipedia.org/wiki/Atmosphere_of_Earth 3 Geological Evidence for Early Life No life  Evidence for life in the ie ie geological record is called a biosignature, or biological signature. lipids in bacterial bacterwife membrane  Evidence of microbial life includes isotope ratios, stromatolites, and microfossils. 4 Geological Evidence for Early Life form of firstmicrobial very is life 5  Geological Evidence for Early Life  The most convincing evidence for early microbial life is the visual appearance of microfossils.  The earliest microfossils accepted as biogenic are dated at 2.0 Gyr ago. These include: ― Filamentous prokaryotes ― Colonial cyanobacteria  More recent strata, dated at 1.2 Gyr ago, contain larger fossil cells comparable to those of modern eukaryotes such as algae. 6 17.2 Forming the First Cells  Models for early life attempt to address the following questions: In what kind of environment did the first cells form? What kind of metabolism did the first cells use to generate energy? What was their hereditary material? liquidwater butnottoo hot Otherwise 1 Temperature range permitting metabolic reactions cease or macromolecules far apart 2 I would say an energy source like the sun causingmaybe photosynthesis to happen to be composed of organic 3 Their hereditary matteral had molecules Such as C N O S P 7 The Prebiotic Soup  Small organic molecules arose abiotically from simple reduced chemicals sparked by lightning.  These produced complex macromolecules that eventually acquired the apparatus for self-replication and membrane compartmentalization. 8 The RNA World  Prebiotic soup does not account for a biomolecule that encodes complex information.  The RNA world is a model in which RNA performed all the informational and catalytic roles of today’s DNA and proteins.  Catalytic RNA molecules called ribozymes have been shown to exhibit enzymatic properties analogous to those of proteins. 9 17.3 Evolution: Phylogeny  Clades are branching groups of related organisms. Each clade is a monophyletic group. ― A group of species that share a common ancestor not shared by organisms outside of that clade Each monophyletic group then branches into smaller groups and ultimately species.  The full description of branching divergence for a species is called its phylogeny. 10 https://genome.cshlp.org/content/12/7/1080/F2.expansion.html Divergence through Mutation and Natural Selection  Populations of organisms diverge from one another through several fundamental mechanisms of evolution: Random mutations: as the chromosome replicates Natural selection and adaptation: favors organisms that produce more offspring Reductive (degenerative) evolution: loss or mutation of DNA encoding unselected traits Simbions parasites Small genomes Diversity 11  Molecular Clocks  The molecular clock is the temporal information contained in a macromolecular sequence. Based on the acquisition of new random mutations in each round of DNA replication anew 00 00 2 new offspring offspring 00 0 2 new new new 12 Molecular Clocks  Genes that show the most consistent measures of evolutionary time are the ribosomal RNA and proteins, tRNA, and RNA polymerase.  The most widely used molecular clock is the gene that encodes the small subunit rRNA (SSU rRNA). 16S rRNA (bacteria) or 18S rRNA (eukaryotes) 13 Molecular Clocks 9 ample 3 14 Molecular Clocks  In practice, a much larger amount of sequence with multiple differences is needed to calculate a phylogenetic tree.  The data are calculated by computer programs, which may yield different results depending on their assumptions. 15 https://bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-6-99 Phylogenetic Trees  Phylogenetic trees can be drawn in different ways: rooted and unrooted. Rooted trees indicate position of the common ancestor; unrooted trees do not. same components just look different 16 Phylogenetic Trees  A phylogenetic tree can compare any set of organisms, even from multiple habitats. 17  17.4 Natural Selection and Adaptation  How does evolution help life survive in a new environment?  Variants that survive to leave offspring undergo natural selection.  We can study the mechanisms of natural selection by: Genomic analysis Comparing gene sequences Strongly selective environments study environment like antibiotics exposure and Experimental evolution evolution high rapid lab Spings mounts collectpopuation of bactera and is grown to survive adapt mutations 18  be repro g evolve 17.5 Microbial Species and Taxonomy resistance Phylogeny-based  Among macro-eukaryotes, a - SSU rRNA similarity ≥95% species is defined as a share the same genus group of individuals that - Average nucleotide identity are capable of (ANI) of interbreeding. orthologs ≥95%  Many microbes, however, reproduce asexually. Ecology-based - Shared ecotype between So what is a microbial organisms with 95% or species? greater identity 19 Classification and Nomenclature  Taxonomy is the description of distinct life forms and their organization into different categories with shared traits; it includes: Classification = the recognition of different classes of life Nomenclature = the naming of different classes Identification = the recognition of the class of a given microbe isolated in pure culture  Classification generates a hierarchy of taxa. 20 Emerging Clades: Unclassified and Uncultured Bacteria  As we discover new microorganisms, how do we decide what to call them?  “Incompletely described” new organisms are designated as follows: Unclassified/uncultured organism Environmental sample Candidate species 21  the 3 branches Luca is the one common ancestor to create of life Bacteria Eurhya archea The sequencing changed because everything had similar genes and make that suggested up came everything Luca from It was thought that animals that lived in hydrothermal vents andgenes were similar to lucas Therefore assuming they came fromthere global warming is happening causing microbes not have a sustainable way to keep way to keep producing due to temperme We don't know how it effects microbes Microbes are the most functionally important organisms on earth because they carry most of everythings genetic material