10- classification and evolution

• Fossils


  Animal and plant remains preserved in rocks
• Formation of fossils


  1. Sediment is deposited on the earth to form layers (strata) of rock

  2. Different layers correspond to different geological eras

  3. Fossils found in different rock strata are quite different, forming a sequence from oldest to youngest
• Fossil record


  Sequence of fossils showing that organisms have gradually changed over time
• Evolutionary theory


  Simple life forms gradually evolved over an extremely long time period into more complex ones
• Fossil record is not complete- many organisms are soft bodied and decompose quickly before they have a chance to fossilise
• Comparative anatomy


  • The study of similarities and differences in the anatomy of different living species
• As the fossil record is incomplete, scientists look for other sources of evidence to determine evolutionary relationships
• Homologous structure


  A structure that appears superficially different (and may perform different functions) in different organisms, but has the same underlying structure
• Homologous structure


  • The pentadactyl limb of vertebrates
• Divergent evolution


  • From a common ancestor, different species have evolved, each with a different set of adaptive features
  • This type of evolution will occur when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat
• Comparative biochemistry is the study of similarities and differences in the proteins and other molecules that control life processes
• Although these molecules can change over time, some important molecules are conserved
• Variations


  Differences in characteristics between organisms
• Types of variation


  • Interspecific variation
  • Intraspecific variation
• Interspecific variation


  • Differences between members of different species
  • Example: a mouse has four legs, teeth, and fur whereas a bird has two legs, two wings, a beak and feathers
• Every organism in the world is different - even identical twins differ in some ways
• Intraspecific variation


  • Differences between organisms within a species
  • Example: people vary in height, build, hair colour, and intelligence
• Adaptations 


  = characteristics which increases an organism’s chance of survival and reproduction in its environment
• Anatomical 


  Body coverings

  camouflage

  teeth

  mimicry
• behavioural 


  Survival behaviours

  courtship

  seasonal behaviours

  migration

  hibernation

  • innate or learned behaviour
• Physiological 


  Poison production

  antibiotic production

  water holding
• Analogous structures 


  Adapted to perform the same function but have different genetic origin