Evolution

Evolution

1. Evolution theories

   • The two contrasting theories
     • Charles Darwin
       • Survival of the fittest
       • Natural section
       • Book of origin
     • John Baptist Lamarck
       • Inheritance of aquired characteristics
         • Passed onto offspring
       • Laws of Use and disuse
   • Factors that drive evolution
     • Mutation
       • Random change of DNA
       • Possibility of new alleles
       • Increases genetic diversity
     • Genetic Drift
       • Change in gene pool due random/ chance events
         • Population bottle neck
           • Occurs when an event drastically reduces population size
             • Bottle neck event
               • Forest fire
               • Flood
               • Drought
               • Tornado
           • The bottle neck effect is genetic drift that occurs after a bottle neck event
             • May cause complete loss of certain allele
       • Reduces genetic diversity
         • Most common in small polulations
     • Gene flow
       • Occurs when individuals migrate in or out of a population and reproduce
         • A green beetle migrates into a purple beetle population and breeds with one of the purple beetles
       • Keeps neighboring populations similar
         • Low gene flow would cause the species to split into two
           • Prevents speciation
     • Natural selection
       • Selects best alleles for survival
       • The individuals who had better survival abilities in a population are more likely to breed, extinguishing weaker ones
       • Types of natural selection
         • Directional
           • Allele frequencies shift to favor those at one extreme of the normal range
             • Only one side of the population reproduces
               • Population may change entirely
         • Stabilizing
           • Allele frequencies shift to favor those with an average genetic makeup
             • Only those in the middle reproduce
             • Clutch size
               • Too little will easily be wiped out
               • Too much would not be able to afford
         • Disruptive
           • Allele frequencies shift to favor those at both ends of the genetic spectrum
             • Intermediate forms are eliminated
               • May cause speciation
       • Adaptation
         • Structural
           • physical change to help survive
             • Fur coats of arctic foxes
         • Behavoural
           • Action done by choice to help survive
             • Squirrel bury nuts
         • Physiological
           • automatic actions of the body to survive

2. Evidence of evolution

   • Fossils
     • Fossil Dating
       • Absolute
         • Makes out precise dates by testing radioactive material in the fossils
       • Relative
         • Fossils in older layers are more primitive
     • Extinct fossils resemble modern animals
       • Shows common ancestry
     • Types of fossils
       • Amber-preserved
       • Insects
     • Formation of fossils
       • Organisms die in water and were covered in sediment
         • Soft tissues quickly decompose, leaving hard structures behind
           • Organisms with hard structures are more likely to turn into fossils
           • Over time, sediment that covers it hardens
     • Preserved ancestral species
   • Geographical Distribution
     • Island species most closely resemble nearest mainland species
       • Founder effect
         • Darwin's finches
       • Populations can show variation on different islands
   • Embryology
     • Compares early stage of different species
       • Identical larvae, different adult body forms
       • Similar embryos related but diverse organisms
         • Mammals, fish and bird embryos all have gills, however they have disappeared in adult forms
   • Comparative Anatomy
     • Homologous structures
       • Similar in structure but different in function
         • Hands
           • Claws
           • Flippers
           • Wings
       • Evidence of common ancestry
   • Molecular & Genetic
     • Biochemical evidence
       • Compares genetic information of different species
         • Closely related species will have similar DNA, RNA & amino acid sequences
           • Hippo
             • TCC TGGCA GTCCA GTGGT
           • Whale
             • CCC TGGCA GTGCA GTGCT
     • Evidence of common ancestry