Module 4.2.2- Classification and evolution

• Taxonomic group


  the hierarchical groups of classification - domain, kingdom, phylum, class, order, family, genus, species

  
• Domain


  A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya.
• Species


  A group of similar organisms that can breed and produce fertile offsprings.
• NAMING SPECIES - THE BINOMIAL SYSTEM

  
• Advantages of binomial system


  avoids confusion of common namesinternational in usename is descriptive and often shows relationships
• Five Kingdoms


  Prokaryotae -> Protista -> Plantae -> Fungi -> Animalia
• Prokaryotae Kingdom


  lack a nucleus and membrane-bound organelles, contain a nucleoid region where a loop of circular DNA is located, unicellular lack organelles
• Protoctist Kingdom


  Unicellular and multicellular

  have nuclei

  may contain chloroplasts
• Fungi Kingdom


  eukaryotic kingdom of heterotrophic decomposers with cell walls made of chitin

  eukaryotes, mainly multicellular, parasitic (saprophytic)symbiotic, no chloroplasts

  store food as glycogen
• Plantae Kingdom


  Kingdom of multicellular photosynthetic autotrophs that have cell walls containing cellulose

  All contain chlorophyll

  Store food as starch
• Animalia Kingdom

  kingdom of multicellular eukaryotic heterotrophs whose cells do not have cell walls

  no chloroplasts

  food stored as glycogen
• What happens in Woese's system for prokaryotae?


  It is split in 2 into Archaebacteria and Eubacteria.

  
• Archaebacteria


  kingdom of unicellular prokaryotes whose cell walls do not contain peptidoglycan

  can live in extreme environments
• Eubacteria


  Kingdom of unicellular prokaryotes whose cell walls are made up of peptidoglycan

  found in all environments

  common
• Phylogeny


  evolutionary relationships between organisms
• Phylogenetic tree


  A family tree that shows the evolutionary relationships thought to exist among groups of organisms

  
• How to interpret phylogenetic trees


  - earliest species found at the base

  - most recent species found at the tip of the branches

  - the closer the branches of the trees are, the closer the evolutionary relationships

  - two descendants that split off from the same node are called sister groups
• Advantages of phylogenetic classification


  - Produces continuous trees as opposed to discrete taxonomical groups, so scientists are forced to fit organisms into a group where it doesn't quite fit

  - The hierarchal nature of Linnaean classification can be misleading as it implies that different groups within the same rank are equivalent (e.g. older or more diverse)
• evidence for Evolution


  1. Fossil Record (paleontology)

  2. Comparative anatomy

  3. Comparative biochemistry
• How do fossils (paleontology) provide evidence for evolution

  - simple organisms found in old rocks and more complex organisms found in more recent rocks

  - plant fossils appear before animal fossils

  - studying similarities in anatomy

  - allow relationships between extinct and living organisms to be investigated
• Disadvantages to using fossils for evidence of evolution


  - they are incomplete

  - fossils destroyed

  - decompose quickly
• Comparative anatomy


  the study of similarities and differences in the anatomy of different species
• Homologous structures- comparative anatomy


  Structures in different species that are similar because of common ancestry. e.g. pentadactyl limb

  Have the same underlying structure

  
• What type of evolution do homologous structures provide evidence for?


  Divergent evolution
• Divergent evolution


  when two or more species sharing a common ancestor become more different over time
• Comparative biochemistry


  Study of similarities and differences in biochemical makeup of organisms
• What are the two most common molecules studies for comparative biochemistry


  Cytochrome c and ribosomal RNA
• How does comparative biochemistry provide evidence for evolution


  To discover how closely two species are related, the molecular sequence of a particular molecule is compared e.g. the order of DNA bases

  The number of differences are then plotted against the rate the molecule undergoes neutral base pair substitutions

  Ribosomal RNA has a very slow rate of substitution
• Variation


  The differences in characteristics between organisms
• Interspecific variation


  variation among members of different species
• Intraspecific variation


  variation among members of the same species
• Two types of variation


  Genetic and environmental
• Genetic causes of variation


  Alleles mutations meiosis sexual reproduction chance
• Environmental causes of variation


  Climate diet accidents culture lifestyle.
• Discontinuous variation


  the variation in phenotypic traits in which types are grouped into discrete categories with no in-between values. e.g. male and female
• How can discontinuous variation be represented graphically?


  Bar chart or pie chart
• Continuous variation


  Can take any value within a range e.g. height and mass
• How can continuous variation be represented graphically?


  Frequency table the can be plotted on a histogram

  Curve can be drawn to show the trend
• Normal distribution curve


  the bell-shaped curve that results from plotting continuous variation data on a graph.
• Features of normal distribution

  - mean, mode and median are the same

  - bell shaped- 50% below and above the mean

  - most values lie close to the mean