Evolution

Evolution

1. Adaptation

   • a process that helps an organism survive an reproduce in an environment
   • structural
     • physical traits that helps survival & reproductive sucess
     • mimicry
       • one species resemble another species
       • katydid mimics a dead leaf to remain unseen
   • behavioural
     • actions/types of behavior that gives an organism the best chance to live
     • nocturnal animals are awake at night, conserve energy & avoid overheating during day
   • physiological
     • the systematic response of an individual to specific external stimulus in order to maintain homeostasis
     • metabolic adjustment with cell/tissues of an organism in response to an environmental stimulus
     • improved ability of an organism to cope with its changing environment
     • tanning of skin is a response to sunlight, skin releases melanin which absorbs UV rays therefore protecting skin
   • development
     • through mutations in DNA that are passed on & accumulate over generation
       • mutations are changes in DNA, can be harmful or provide organism genetic advantage

2. uses variation causes by meiosis & sexual reproduction

3. looks as how species change because of the environment

4. Natural Selection

   • Antibiotic Resistant Bacteria
     • bacteria produce fast, allowing large genetic variation in population
     • antibiotic introduced to bacteria's environment, bacteria has resistance to it & survive while bacteria without resistance die
     • surviving bacteria, multiply, produce offspring that have same resistance to antibiotic
   • variation
     • member a of population have slight differences among them & much of variation is heritable
     • some beetles are green and some are brown
   • selective pressure
     • population tend to create more progeny than can survive
       • not all survive due to competition for food, nesting sites, mates etc.
     • green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles
   • survival of the fittest
     • better adapted individuals survive & reproduce
     • the surviving brown beetles have brown baby beetles because this trait has genetic bases
   • gradual change
     • over course of many generations, the more advantageous traits become common in the population
     • brown coloration allows beetles to have more offspring, so becomes more common in population
       • if process continues, eventually all individuals in population will be brown
   • Peppered Moth (Biston Betularia)
     • occur in 2 forms (morphs)
       • grew with dark splotches (mottles)
       • completely dark (melanic)
     • dark moths rare in early 1800
       • white moths very abundant
     • dark moths in industrial regions because tree trunks darkened by soots
       • dark moths camouflaged by dark background;white moths were not
         • birds more likely to prey on white moth
           • 1895: 98% of moths dark
   • Darwin's finches
     • finch=small bird;13 species
     • finches on Galapagos descendants of finches from South America
     • finches morphologically similar but vary in beak size and shape
     • beak size influence feeding efficiency
       • large beaked finches break larger seeds easily
       • small beaked more efficient with smaller foods

5. Mechanisms

   • genetic drift
     • change in gene pool of small population due to chance
     • bottleneck effect
       • reduction of alleles
       • result from disaster that drastically reduces population size
         • earthquakes, volcanic eruption, hunting, asteroid hitting earth,
     • founder effect
       • resulting from colonization of new location by small number of individuals
       • results in random change of gene pool
       • colonization of Galapagos Islands by birds from mainland South America (first Darwin's Finches)
   • gene flow
     • gain/loss of alleles from population by movement of individuals/gametes
     • results from immigration/emmigration
     • increase variation within population by introducing new alleles that produced by mutation in another population
     • Praire dog colonies only allow new members to join group once a year, bringing new genetic information
   • mutation
     • change in organism's DNA that makes a new allele
     • inheritable mutations can be neutral, harmful or beneficial
     • beneficial: mutation becomes frequent within gene pool
     • lethal mutation: die because of natural selection (only if it prevents reproduction; then no die)
     • I950. warfarin used to control rat population. Few rats had mutations that made them resistant
       • 1960: many warfarin resistant rats
         • organisms become adapted due to toxic in body to be able to break down
   • non-random mating
     • selection of mates other than by chance
     • inbreeding
       • mating between close relatives
       • results in loss of genetic variation amongst population
     • assortive mating
       • individuals mate with those that have similar phenotype
         • tall people mate with tall people
     • sexual selection
       • occurs when males compete for right to reproduce
         • females choose to mate with males that have particular phenotype
   • natural selection
     • individuals with favourable traits, more likely to leave more offspring better suited for environment
     • stabilizing selection
     • directional selection
     • diversifying selection

6. Evidence

   • fossil record
     • shows preserved remains/traces of organisms/its activity
     • amber
       • fossilized sap of trees holds well-preserved insects
     • fossilized shell of trilobite, Modocia typical, dominant life-form in early years
   • biographical distribution
     • compares past &present geographical distribution of species
       • closely related species found in same region
   • comparative anatomy
     • study of similarities and differences in anatomy of organisms
     • homologous structure
       • body parts have similar structure, different function
     • analogous structure
       • body parts have similar functions, different anatomy
     • vestigal structures
       • have no current function
   • embryology
     • pre-birth staged of organism's development
   • DNA
     • similar in DNA indicates common ancestor
     • amino acid comparison
       • percent of amino acid that are identical to amino acid in Human hemoglobin, polypeptide
   • example
     • artifical selection
       • rapid, heritable changes have been produced in domestic animals & plants by selectively breeding organisms with desired features
     • industrial mechanisms
       • evolution of black coloration among peppered moths in response to darkening of their environment by industrial pollutants

7. Speciation

   • formation of new species due to evolution
     • new species come from existing one
   • modes
     • new species created when 2 populations are reproductively isolated
     • Sympatric speciation
       • when population slit into separate gene pools & continue to share similar geographic location
       • new species originate within same geographic are of parent species
       • two frogs in same area (one is diploid; other is tetraploid)
       • mutation
     • Allopatric speciation
       • induces when ancestral population is separated by geographical barrier
       • genetic drift
       • Ecological niche
         • ecological role &physical distribution of species in its environment
       • Adaptive radiation
         • diversification of common ancestral species into a variety of differently adapted species
   • reproductive barriers
     • any mechanism that impedes two species from producing fertile/ viable hybrid offspring
     • Pre-zygotic
       • occurs before formation of zygote takes place
       • most cases mating doesn't occur
       • temporal isolation (sympatric)
         • breeding occurs at different times for different species
       • habitat isolation (allopatric)
         • species breed if different habitats
       • behavioural isolation (both)
         • little or no sexual attraction between species
       • mechanical isolation
         • structural differences prevent gamete exchange
       • gametic isolation
         • gametes die before uniting with gametes of other species
     • Post-zygotic
       • when fertilization occurs successfully between closely related species,
         • some incompatibility results in zygotic mortality
       • hybrid inviability
         • unlikely to live long
       • hybrid sterility
         • infertile (cannot produce gamete)
       • hybrid breakdown
         • hybrids of crossed species are viable &fertile BUT it two hybrids mate, offspring is sterile/weak
   • Pathways of evolution
     • divergent
       • evolution in which 2 or more species evolve different traits resulting in diversifying selection/ genetic drift
       • evidence: homologous feature
     • convergent
       • evolution in which unrelated species become very similar in phenotype if they live in similar area
       • evidence: analogous features
     • coevolution
       • evolutionary change in which one species evolves in response to evolution of another
       • evidence: predator-prey; parasite &host

8. changes in gene population from 1 generation to another

9. Pace of Evolution

   • gradualistt model (Neo-Darwinian)
     • evolution occurs slowly, at a steady pace where changes overtime accumulate in population
   • punctured equilibriam
     • evolution occurs quickly in rapid bursts

10. Microevolution

    • change in population's gene pool over succession on generations
    • evolutionary changes in species over relatively brief periods of geological time

11. Macroevolution

    • origin of taxonomic groups higher than species level

12. symbiosis

    • one's harmed
    • predator/prey
    • pollutant/flower

13. Phylogenetics

    • history of how organisms evolvesd
    • trees
      • diagrams that show evolutionary relationships between species
        • taxa joined together in tree are implies to have descended from common ancestor

14. By: Raman Chung

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