Classification and Evolution

• Classification - the process where living organisms are organised into groups based on similar features
• Taxonomic groups: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Domain - the highest taxonomic rank in the hierarchical biological classification system
• Species - a group of organisms that can breed to produce fertile offspring
• Binomial nomenclature - the naming of organisms using the genus and species name
• Prokaryotae:

  • unicellular
  • no nucleus or membrane bound organelles
  • no visible feeding mechanism
• Protoctista:

  • (mainly) unicellular
  • nucleus and membrane bound organelles
  • can be sessile, or move by unduly podia or ameboid mechanisms
  • nutrients required by photosynthesi, ingestion or both
• Fungi:

  • unicellular or multicellular
  • nucleus and membrane bound organelles, cell wall made of chitin
  • no chloroplasts or chlorophyll
  • no mechanisms for locomotion
  • body/mycelium made of hyphae
  • saprotrophic nutrition
  • Store food as glycogen
• Plantae:

  • multicellular
  • nucleus and membrane bound organelles, cell wall made of cellulose
  • chlorophyll and chloroplasts
  • do not move; some gametes have cilia
  • autotrophic nutrition
  • store food as starch
• Animalia:

  • multicellular
  • nucleus and membrane bound organelles
  • no chloroplasts
  • move by undulipodia, contractile proteins
  • nutrients acquired by ingestion (heterotrophs)
  • Store food as glycogen
• Biological evidence for classifying organisms:

  • haemoglobin in different animals differs by a number of amino acids
• Carl Woese 3 domain system:

  • sequences of nucleotides in ribosomal RNA differ
  • cell membrane lipid structure
  • sensitivity to antibiotics
• Eukarya:

  • 80s ribosomes
  • RNA polymerase has 12 proteins
• Archaea:

  • 70s ribosomes
  • RNA polymerase has 8-10 proteins and is similar to Eukarya
• Bacteria:

  • 70s ribosomes
  • RNA polymerase has 5 proteins
• Archaebacteria:

  • ancient bacteria
  • live in extreme environments
  • more closely related to eukarya than bacteria
• Eubacteria:

  • true bacteria
  • found in all environments
• Phylogeny - the evolutionary relationship between organisms
• Phylogenetic tree - A diagram that shows the evolutionary relationships between organisms.
• Phylogenetics - the study of evolutionary relationships among organisms.
• Advantages of phylogenetic classificatio:

  • can be done without using the Linnaean classification, and thus can be used to check the correctness of Linnaean classification
  • phylogeny produces a continuous data set, whereas classification forces organisms into discrete groups
• Evolution - the theory that organisms change over many years due to natural selection
• Darwin:

  • noticed differences in finches in the Galapagos
  • their beaks were related to the food available
  • birds with more suitable beaks survived longer, and would have more offspring
• Evidence for evolution:

  • palaeontology
  • comparative anatomy
  • comparative biochemistry
• Palaeontology:

  • fossils allow us to see how organisms have changed over time
  • simpler organism fossils are found in older rocks, more complex ones in newer rock
  • plant fossils appear before animal fossils
  • disadvantages:
  • organisms decompose before they can fossilise
  • conditions needed are not always present
  • fossils have been destroyed by earths movements
  • many fossils are undiscovered
• Comparative anatomy:

  • the study of the similarities and differences in the anatomy of different organisms
  • the basic structure of all vertebrae limbs are similar
  • therefore all vertebrae come from a common ancestor
• Homologous structures:

  • structure appears superficially different but has same underlying structure
• Pendactyl limb:

  • limb with five digits, seen on tetrapod vertebrae
• Comparative biochemistry:

  • study of similarities and differences in the proteins and other biological molecules
  • important molecules that perform specific roles in life remain highly conserved between species e.g. cytochrome C
• Neutral evolution:

  • the structure of a molecule that is varied does not affect its function and therefore natural selection has no effect
• Interspecific variation:

  • variation between numbers of different species
  • widest type of variation
• Intraspecific variation:

  • variation between organisms in the same species
• Genetic variation:

  • differences in the organisms genetic materials inherited from its parents
• Environmental variation:

  • the environment causes variation
• Genetic causes of variation:

  • cause by genes and alleles
  • alleles cause genetic variation within a population, as well as mutations, meiosis, sexual reproduction and chance
• Mutations:

  • changes to DNA can lead to changes in the proteins that are coded for
  • mutations in gametes can be passed onto the offspring
• Meiosis:

  • variation is caused due to independent assortment and crossing over
  • gametes receive half of the genetic material Of each parent cell
• Chance:

  • random gametes meet and fertilisation occurs
• Discontinuous variation:

  • a characteristic can only result in certain values
  • no inbetween values
  • determined purely by genetic factors
  • represented by bar charts
  • controlled by one gene
• Continuous variation:

  • characteristic that can take any value within a range
  • cause by a number of genes
  • influenced by environmental factors
  • gives a normal distribution curve on a graph; mean, mode and median are the same