origins of life, the kingdoms + evolution

• entropy is a measure of disorder which must always increase as physical systems decay
• life creates order since biological systems organise and maintain themselves through growth and reproduction
• life needs energy to combat entropy
• abiogenesis - generating life from scratch
• endosymbiosis - an organism (endosymbiont) living inside a cell of another host organism for mutual benefit
• evolution explains:

  • the diversity of life
  • the relatedness of life
  • the complexity of living organisms
  • how life can change over time
• theories of evolution:

  • genetic diversity
  • selection pressure
  • survival of the fittest
• selection pressure causes three different types of outcome:

  • stabilising
  • disruptive
  • directional
• evolution evidence - the fossil record

  remains of organisms preserved in sedimentary rock, hard tissue (bones and shells) are best preserved, carbon dating
• a punctuated equilibrium model of evolution suggests there were periods of rapid change
• the gradualist theory of evolution suggests change happened little by little over time and is ongoing
• evolution evidence - comparative genetics

  the genetic code is universal coding for similar proteins in related species, gene families and the molecular clock
• evolution evidence - comparative anatomy

  similar homologous structures (eg. bone structure) or convergent analogous function (eg. having wings) suggesting common ancestory
• evolution evidence - speciation

  isolation resulting in the production of different species, can be allopatric or sympatric isolating mechanisms
• evolution evidence - microevolution

  antibiotic resistance in bacteria, pesticide resistance in insects, heavy metal tolerance in plants in lead mining areas
• evolution evidence - artificial selection

  humans are the selection pressure controlling crop plants, food, domesticating animals as pets etc.
• synteny - similar gene sequences found on chromosomes between different species
• types of isolation:

  geographical - allopatric speciation

  temporal - different breeding times

  ecological - same area different habitats

  behavioural - courtship rituals differ

  mechanical - anatomical difference prevents mating

  gametic - gametes cannot unite

  hybrid - sympatric speciation (infertile offspring)
• chimpanzees are our closest relative in a genetic sense
• neanderthal -> denisovan -> homo sapiens