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Life on Earth: Past and Present (History of Life on Earth (Body Changes…

- - - - Necessary methods for sustaining life may have been found in early vesicles
      - Early self-replicating and metabolic organisms
      - Some vescles may have a semi-permeable bilayer and be able to absorb montmorillonite particles
    - - Most likely the first genetic molecule on earth
        
        Plays a central role in protein synthesis
        
        Ribozymes
        
        Single Stranded, can assume a variety of 3D shapes from their nucleotide sequence
        
        Could have provided the template in which DNA was able to form for more complex cells
    - - First atmosphere was thick with water vapor, little to no oxygen
        
        Cooling of Earth lead to formation of oceans
      - Carbon Dioxide, Nitrogen, Ammonia, Methane and Hydrogen
        
        Hydrothermal Vents
        
        Organic compounds first produced in these areas on the sea floor that gushed heated water and minerals from inner Earth
        
        Alkaline Vents
        
        Release warm water at a high pH, making an environment suitable for early life
      - Scientist Theories
        
        1920's:A.I. Oparin and J.B.S. Haldane
        
        Hypothesized about Earth's early environment
        
        Reducing (adding electrons)
        
        Organic compounds formed simpler molecules
        
        Energy came from sunlight and UV radiation
        
        "Primitive/Primordial Soup"
        
        1953: Stanley Miller and Harold Urey
        
        Created laboratory conditions to support the Oparin-Haldane Hypothesis
        
        Yielded a variety of amino acids found today
  - - - Used to document the 'visible' history of life
        
        Favors species that were alive for longer periods of time
        
        Gaps in record are filled by more and more discoveries
      - Based primarily on the sequence in which fossils have accumulated in strata (sedimentary rock layers)
      - Incomplete evolutionary history, as some species may not have left fossils behind
    - - Radiometric Dating
        
        Based on the decay of radioactive isotopes
        
        Half life
        
        The time required for 50 percent of the parent isotope to decay
        
        Also known as Carbon Dating
        
        The rate at which carbon-14 decays into nitrogen
        
        Half life of carbon-14; 5,730 years
    - - Fossils can provide a detailed look at the origin of modern species
      - Illustrate how new features come along and how long it takes for new attributes to form
      - Ex: Mammals and other land animals stemmed from early tetrapods
  - - - A standard time scale that divides Earth's history into four eons and further subdivisions
        
        Archaean
        
        Began Approx. 4 Billion years ago
        
        3.5 billion years ago Oldest fossils of cells appear
        
        Proterozoic
        
        Approx.2.5 years ago
        
        Oldest fossils of eukaryotic cells appear
        
        Hadean
        
        Origin of Earth
        
        Approx. 4.6 Billion years ago
        
        Phanerozozic
        
        Mesozoic
        
        Jurassic
        
        Approx: 210 Million years ago
        
        Gymnosperms still in charge as plant overlords, Dinosaurs are the main hanchos in town, here come those apex species
        
        Cretaceous
        
        Approx: 145 Million Years ago
        
        Flowering plants appear, RIP Dinos at the end of the period along with a lot of other species
        
        Triassic
        
        Approx: 252 Million years ago
        
        Gymnosperms dominate land, Dinos become big bois, here come dem mammals
        
        Cenozoic
        
        Paleogene
        
        Approx: 66 Million years ago
        
        Major Radiation of mammals, birds, and pollinating insects, and the origin of primates
        
        Neogene
        
        Approx: 23 Million years ago
        
        Continued radiation of flower plants and mammals, earliest human ancestors appear (bipedal creatures)
        
        Quaternary
        
        Approx: 2.6 Million years ago
        
        Ice ages, Homo genus comes around, through present day and the entirety of human history (195,000 years)
        
        Paleozoic
        
        Silurian
        
        Approx: 444 Million years ago
        
        Diversification of early vascular plants
        
        Devonian
        
        Approx: 419 Million years ago
        
        Diversification of bony fish, tetrapods and insects appear
        
        Ordovician
        
        Approx. 485 Million years ago
        
        Marine algae abundant, colonization of land
        
        Carboniferous
        
        Approx: 359 Million years ago
        
        Forests appear and seed plants, reptiles, amphibians dominant
        
        Cambrian
        
        Approx. 541 Million years ago
        
        Cambrian Explosion: Increase in diversity of many animal phyla
        
        Permian
        
        Approx: 299 Million years ago
        
        Radiation of reptiles, origin of most present insects, extinction of a lot of life at the end of the period
    - - Five major extinctions, two major ones that are focused on
        
        Cretaceous
        
        Occurred 66 million years ago
        
        Wiped out more than half of all marine species and all the dinosaurs
        
        Thought to have been cause by a giant meteor colliding with earth, and creating such a large layer of debris it blocked sunlight
        
        Permian
        
        Defines the boundary between Paleozoic and Mesozoic eras
        
        252 million years ago
        
        Drastically altered life in the ocean and a large chunk of terrestrial life too
        
        Occurred during the most extreme episode of volcanism in the past 500 million years
    - - Plate Tectonics
        
        The continents are part of great plates of earth's crust that float on the mantle
      - Movements in the mantle cause the plates to move over time
        
        The moving plates create disturbances in earth's land masses such as earthquakes, volcanic eruptions, etc.
        
        Movements can cause big problems for life on the continents
        
        Can cause allopatric speciation
      - 250 million years ago, the continents were smooshed together to create the super continent Pangea
  - - - Heterochrony
        
        An evolutionary change in the rate or timing of developmental events
      - Changes to rates can change the adults of the species to look very different
      - Paedomorphosis
        
        Some species may retain features that were child structures in an ancestral species
    - - Homeotic genes
        
        Master regulatory genes that determine basic features on a species
    - - Can come from a disruption or change to the genetic sequence, and if beneficial/not effect the species it can oftentimes remain apart of the gene pool
    - - Changes can be limited to one cell type, creating variation within a species
- - - - Evolutionary Relationships through Phylogenies
        
        Binomial Nomenclature
        
        Naming system invented by Carolus Linnaues
        
        Genus species
        
        Latin names to classify the species
        
        Hierarchial Classification
        
        Taxon
        
        Named taxonomic unit at any level of the hierarchy
        
        Class
        
        Order
        
        Phylum
        
        Family
        
        Kingdom
        
        Genus
        
        Domain
        
        Species
        
        Phylogenetic Tree
        
        A branching diagram in which the evolutionary history of an organism can be sorted
        
        Another type is known as a Cladogram
        
        Branch Points
        
        Represents a common ancestor between two species
        
        Sister Taxa
        
        Groups of organisms that share an immediate common ancestor not shared by any other group
        
        Basal Taxon
        
        A lineage that diverges from all other members of its group early in the history of the group
      - Phylogenies inferred from Morphological and Molecular Data
        
        Homologies
        
        Phenotypic and genetic similarties due to shared similarities
        
        Analogy
        
        Convergent evolution that occurs when similar conditions force similar structures to form
        
        Species can be grouped by the different phenotype they express and how the attribute came to expressed in the species/organisms
      - Shared Characteristics to build phylogenetic trees
        
        Cladistics
        
        Common ancestry is the primary criterion used to classify organisms
        
        Clades
        
        Each of which includes an ancestral species and all of its descendants
        
        Paraphyletic
        
        Monophyletic
        
        Polyphyletic
        
        Shared Characteristics
        
        Ancestral
        
        Originated in an ancestor of the taxon
        
        Derived
        
        An evolutionary novelty unique to a clade
        
        Outgroup
        
        A species or group of species from an evolutionary lineage that is closely related to but not part of the group of species being studied
        
        Maximum Parsimony
        
        "Occam's razor", sometimes the simplest answer is the correct one
      - Molecular Clock
        
        An approach for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates
        
        Calibration of the molecular clock comes from genes that have an average and steady rate of change
        
        Irregular bursts of evolution can throw the rate of change in the clock off
        
        Cannot expand past the documented fossil records
        
        Large changes can throw off the clock numbers and graph