Evolution and development

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Biological diversity - evolution+development

  • phylogenetic trees - express relationships between organisms
  • different body plans+but common traits - share common ancester
  • greater - evolutionary distance between organisms - greater, underlying differences - body plan 
  • Cambrian explosion - biggest radiation - all phyla present today+others no longer seen
  • Cambrian explosion  - 1st appearance, multicellular animals - radically different body architecture
  • evolutionary radiations still occurring - microevolution 
  • radiations involve changes - morphology+branching - new species 
  • extinction - dinosaurs (end of Cretaceous) opened up - ecological niches
  • human arm, feline leg, whale flipper+bat's wing = homologous structures, all derive forelimb - common ancestor
  • bones underline structures = same - modified, natural selection - increase/reduction - relative size
  • analogous structures don't share common ancestry 
  • eg wings - birds, pterosaurs+bats. all developed - Tetrapod forelimb - different evolutionary history = convergent evolution 
  • convergent evolution - hard - properly classify organisms - new methods - DNA sequencing circumvent problem
  • organisms change over evolutionary time scales - change body plan
  • changes = due - modifications - previously existing structures
  • change - shape/size/position - pre-existing structures
  • loss - pre-existing structure
  • duplication - pre-existing structure
  • mammalian middle ear bones derived - reptile jaw
  • snakes lost cervical vertebrae+multiplied thoracic vertebrae
  • all metazoans originate - single fertilised egg cell (zygote)
  • zygote - several rounds division - blastocyst
  • folding - layer endoderm cells causes formation - 3 cell layered gastrula
  • - chordate, notocord forms+lays down axis - development of neutral tube
  • details - gastrulation+neurulation differ across different phyla - bilateran animals. however all develop bilateral symmetry
  • bilateria = bilaterally symmetric along 1 axis - show differentiation - 2 axes (dorso - ventral+anterior - posterior)
  • show differentiation along dorso-ventral+anterior-posterior axes - embryonic development progresses
  • signals between cells = clues tell cells how - differentiate, rate to grow, which direction to grow+what proteins make
  • all cells - developing animal = complete complement - genes - behave differently - other cells - cell genes turned on+off = gene regulation 
  • DNA = polymerised nucleotides = adenine, cytosine, guanine, thymine
  • DNA sequence encodes genes - order nucleotides = arranged
  • genes = blueprint - make proteins 
  • genes arranged linearly - chromosome (most DNA…

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