Lesson 6

• Scientific classification


  A method by which biologists organize living things into groups. It is also called taxonomy.
• Taxa


  Groups of organisms in taxonomy
• Examples of taxa include kingdom and species
• Why biologists classify organisms

  • To make sense of the incredible diversity of life on Earth
  • Scientists have identified millions of different species of organisms
  • The most diverse group of organisms is the insects
• Linnaean system of classification


  The most influential early classification system, developed by Carolus Linnaeus
• Linnaeus was a Swedish botanist who lived during the 1700s and is known as the "father of taxonomy"
• Linnaeus tried to describe and classify the entire known natural world, publishing his classification system in 1735 in a work called Systema Naturae ("System of Nature")
• Taxa in the Linnaean system

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Kingdom


  The highest taxon in Linnaean taxonomy, representing major divisions of organisms
• Phylum


  A division of a kingdom, e.g. chordates and arthropods in the animal kingdom
• Class


  A division of a phylum, e.g. mammals and birds in the chordate phylum
• Order


  A division of a class, e.g. rodents and primates in the mammal class
• Family


  A division of an order, e.g. hominids and hylobatids in the primate order
• Genus


  A division of a family, e.g. Homo and Pan in the hominid family
• Species


  The lowest taxon in Linnaeus' system, e.g. Pan troglodytes and Pan paniscus in the Pan genus
• Thomas Malthus was an English economist who wrote an essay called "On Population" arguing that human populations have the potential to grow faster than the resources they need, leading to disease and famine controlling population size
• Catastrophism


  A theory developed by Georges Cuvier based on paleontological evidence, stating that natural history has been punctuated by catastrophic events that altered the way life developed and rocks were deposited
• Gradualism


  A theory developed by James Hutton and applied to paleontology, stating that species appeared by the gradual transformation of ancestral species
• According to the gradualism theory, the population of a species is transformed slowly and progressively into a new species by the accumulation of micro-evolutionary changes in the genetic heritage
• Lamarck's theory of use and disuse


  The law of use and disuse states that when certain organs become specially developed as a result of some environmental need, then that state of development is hereditary and can be passed on to progeny
• Evolution of Darwin's theory

  1. Darwin assumed species can change over time based on fossils

  2. Darwin saw Earth and its life were very old, allowing time for evolution

  3. Darwin knew populations could grow faster than resources, leading to a "struggle for existence"

  4. Darwin knew offspring have variations that can be inherited, and nature selects the most useful variations through natural selection

  5. Darwin inferred that natural selection could change species over time, potentially evolving into new species
• Uniformitarianism


  Charles Lyell's theory stating that the processes by which current geological features were created were slow, steady, and constant
• Natural selection


  • Occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation
  • Requires variation among individuals, heritability of variation, and variation in fitness