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Mechanism - Coggle Diagram

- - - - change in DNA sequence
        
        within chromosome
        
        within a gene
      - no harm no benefit
      - harm
        
        Thalassemia
        
        Cystic Fibrosis
      - benefit
        
        Low cholesterol mutation
        
        Super sleeper mutation
      - impact of mutation on allele frequencies is not large
    - - Gene mutation
        
        change in sequence of nucleotides
      - Chromosome mutation
        
        change in arrangement/structure of chromosomes
      - Genome mutation
        
        change in number of chromosomes in genome
  - - - random change in allele frequency
      - may cause some allele disappear completely
      - due to chance
      - important for formation of new species
    - - Bottleneck Effect
        
        sharp decline in population size
        
        due to environmental factor: natural disasters
        
        random event
        
        some genes are extinguished from the population
        
        drastic reduction of total genetic diversity in original
        
        Importance
        
        a population may just disappear tgt with certain allele
        
        species that don't adapt well to environment may survive to (because selective advantage doesn't matter in natural disaster) (based on lucky)
        
        newly evolved species may increase in number vry fast
      - Founder Effect
        
        new population- small no of individuals
        
        cleaved from original population
        
        does not have genetic diversity/ reduction of variation
        
        may or may not form new species - due to selection pressure , adapted to new environment
  - - - struggle for existance
      - selection pressure
        
        food
        
        shelter
        
        life necessities
      - survival of fittest
      - more offspring
      - may result in changes of inherited characteristics
    - - Stabilising
        
        population stabilizing on a particular trait (selective advantage)
        
        genetic diversity decrease
        
        Eg: human birth weight - average birth weight survive more
      - Disruptive
        
        intermediate traits produce less
        
        extreme traits produce more
        
        Eg: gray and white rabbit - white rabbit population decrease
      - Directional
        
        bell curve that shift left /right
        
        greater fitness=selective advantage - increase population
        
        Eg: peppered moth(industrial revolution)
    - - Antibiotic Resistance Bacteria
        
        non resistant strain-selective disadvantage
        
        resistant strain- selective advantage
      - Sickle cell anemia
        
        Homozygote with normal allele(NN)
        
        susceptible to death from malaria
        
        because plasmodium attack normal RBC
        
        Homozygote with sickle cell allele(SS)
        
        resistant to malaria
        
        susceptible to death from sickle cell anemia
        
        Heterozygote (NS)
        
        selective advantage
        
        refrain from malaria and sickle cell anemia
- - - - evolutionary process of formation of new species from existing species
      - species : a grp of organism capable of interbreeding to produce fertile offspring
      - occur when species lose ability to interbreed(isolation)
    - - Allopatric
        
        geographical isolation
        
        prevent interbreeding
        
        no gene flow
        
        environment different give rise to changes in inherited characteristics
        
        when population come into contact, they are reproductively isolated
        
        genetic drift occured
        
        Eg : Kaibab and Abert Squirrels
      - Sympatric
        
        same habitat
        
        no geographically separated
        
        isolation
        
        form new species
        
        maintain reproductive isolation within a population once new species introduced
    - - Pre-zygotic
        
        Temporal
        
        different times of year
        
        Ecological
        
        different habitats
        
        Behavioural
        
        different courtship behaviours
        
        Mechanical
        
        physical differences prevent copulation/ pollination
      - Post-zygotic
        
        hybrid inviability
        
        fail to develop to reproductive maturity
        
        hybrid infertility
        
        fail to produce functional gamete(infertility)
        
        hybrid breakdown
        
        F1 hybrids are fertile so F2 generation fail to develop properly
  - - - changes in O2 level in seawater
      - global warming
      - global cooling
      - comopetition among species
    - - cutting rainforest
      - destroy natural habitat
      - pollution
      - over harvesting