evolution

• Natural selection: 

  1.        Variation (mutation): variation for DNA, different physical traits

  2.        Struggle for survival: new mutation has to survive to pass on (more successful food + environment=more offspring)

  3.        Reproduction of these best adapted: survived mutation needs to be able to reproduce

  4.        Best adapted trait becomes more common: needs to become successful to be dominant 
• Selection pressure: the environmental factors that affect an organism’s ability to survive (causes variations to survive and others to die – including environmental factors)

  Gene pool: all the genes or alleles in a population
• Speciation: process resulting in formation of new species 

  -              Some species can reproduce (may produce fertile offspring)

  -              Over time, can lead to the formation of new species (also known as natural selection)

  Allopatric speciation – geographical separation

  Sympatric speciation – isolating factors – b/h differences (e.g. bird songs), breeding times/season, habitat differences, infertile offspring (genetic incompatibility)
• Homologus structure: structure similar in species because they evolved from a common ancestor. The structure may not be used for same function

  Convergent evolution: process on why very different species evolve to have similar traits (result of adaptation)

  Analogous structure: structure in organisms that serve similar function but have different structure (evolved independently)

   

   

   

   

   

   

   
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  Fossil: remains or traces of an organism that existed in the past (early evidence for evolution and identified new species

  Fossilised faeces –embedded in rocks/other substances

  Fossilisation: processof an organism becoming a fossil (organism buried from oxygen quickly can beaffected by weather and decompose, while skeletal structures fossilise as theytake longer to decompose)
• Transitional fossil:fossil/organism that shows intermediate state between ancestral + descendants(missing link-space between two fossils evolution)

  Darwin Theory: lifeoriginated in sea, crawled on land and skies and grew fur. 

  Transitional fossilsoften display characteristics of 2 species (e.g Archaeopteryx – earliest birdand transition between bird and reptile)

  Living fossil: modernspecies identical to ancient species

  Trace fossil: evidenceof living thing (faeces, footprint)
• Absolute dating: method of measuring age of fossil through radioactivity (half life)

  Relative dating: methodof determining age via events (before+after) (through layer of sedimentaryrock: older the fossil, deeper in layers)

  Comparative dating:using similar fossils to determine age

   
• Evolution: life forms change with environmental pressures