Please enable JavaScript.

Coggle requires JavaScript to display documents.

Evolution Any change in the heritable traits within a population across…

- - - - Variation
        
        Competition
        
        Survival, reproduction
        of fittest
        
        Adaptive radiation, accumulation of favourable traits
- - - - transformation of one into another
        splitting of ancestral species two descendant ones
      - distinctiveness between species at a single locality
        connection among diff pops at diff locations
    - - Reproductive isolation mechanisms
        
        prezygotic
        
        habitat isolation
        
        geographical (barriers like oceans, mountains)
        
        ecological (diff habitats of same area)
        
        temporal isolation (diff reproductive seasons)
        
        behavioural isolation (diff mating calls, dances, pheromones)
        
        mechanical isolation (body structure prevents mating)
        
        gametic isolation (gametes cannot fuse)
        
        postzygotic
        
        reduced hybrid viability
        (genetic incompatibility, abort development)
        
        reduced hybrid fertility
        (infertile/cannot backbreed)
        
        hybrid breakdown
        (next gens becomes feeble/sterile)
      - allopatric speciation
        geog barriers :arrow_down: gene flow
        genetic divergence
        reproductive isolation
      - Sympatric speciation
        divergence despite lack of geographic isolation
        
        Polyploidy
        
        Autopolyploidy
        extra sets of chromosomes from single species (meiosis failure)
        new viable and fertile species can arise from diff ploidy level
        
        Allopolyploidy
        two diff species contribute to a polyploid hybrid
        
        Sexual selection
        e.g. mate w same colour (reduce diversity, segregates genes)
        
        Habitat differentiation
        genetic factors allow new gen to exploit resource unused by parent gen
- - - - Selection is on existing variations
      - Limited by historical constraints (descent w mods)
      - Adaptations are often compromises
      - . Chance + the environment interact w nat sel
  - - - Sexual dimorphism
        
        difference in secondary sexual characteristics
      - Intrasexual selection
        
        mate choice
        
        good gene hypothesis (traits for survival)
        
        run away hypothesis (traits for appearance)
      - Intersexual selection
        
        (usually males) compete with each other
  - - - how are we protected from harmful alleles?
        
        nat selection
        
        not every mutation happens in exons
        
        silent mutations
        
        missense mutations can be conservative
        
        mutations must happen in gametes to pass to offspring
      - chromosomal aberration
        
        doesn't really change genes but rather the linking of genes
        
        sometimes may be beneficial
    - - Random fertilisation
      - Crossing over of bivalents
      - Independent assortment