4.2 Classification and Evolution

• divergent evolution


  from a common ancestor different species evolve, each with a different set of adaptive features.

  • occur when closely related species diversify to adapt to new habitats.
• convergent evolution 


  when unrelated species begin to share similar traits due to adapting their similar habitats.

  • similarities evolve when the organisms adapt to similar environments or similar selection pressures.
• species

  a group of organisms that are able to produce fertile offspring
• phylogenetic classification

  arranges species into their groups according to their evolutionary origins and relationships.

  • tells us how closely relates species are and how recent their shared common ancestors are
• prokaryote

  • unicellular
  • no membrane bound organelles
  • small ribosomes
  • ring of DNA with no associated proteins
  • no feeding system, absorbs nutrients or some photosynthesise
  • autotrophic and heterotrophic
• protoctista

  • unicellular
  • has nucleus and membrane bound organelles
  • sometimes has chloroplasts
  • some have cilia or flagella
  • nutrients absorbed by photosynthesis, ingestion of other organisms or some are parasites
  • autotrophic and heterotrophic
• fungi

  • unicellular or multicellular
  • has nucleus and membrane bound organelles
  • no chloroplasts
  • cannot move
  • have a body made of threads or hyphae
  • heterotrophic
  • food can be stored as glycogen
• plantae

  • multicellular
  • have nucleus and membrane bound organelles
  • have chloroplasts
  • don't move
  • autotrophic
  • food stored as starch
• animalia

  • multicellular
  • have nucleus and membrane bound organelles
  • can move using cilia, flagella or muscles
  • heterotrophic
  • food can be stored as glycogen
• DNA/RNA evidence

  more closely related species have more similar DNA/RNA base sequences

  • more mutations accumulate over time, so evolved from a common ancestor longer ago
• protein evidence

  more closely related species have more similar amino acid sequences

  • not as accurate as genetic code is degenrate
• cytochrome C evidence

  a protein used in respiration which is often used as a specific protein comparison
• molecular evidence for the 3 domain system

  
  

  The prokaryote kingdom was split into archaea and bacteria domains:

  • archaea has histones similar to eukaryotes but bacteria do not
  • RNA polymerase in archaea has a more similar amino acid sequence to eukaryotes than bacteria
  • archaea and bacteria have different cell wall and membrane structure
  • the 70s ribosomes in archaea and bacteria have different structures
• interspecific variation

  variation between members of different species
• continuous variation

  controlled by many genes (polygenic) and can be influenced by environment.

  • no distinct categories
  • mostly give a normal distribution (bell-shaped curve) on graph
  • larger standard deviation = more variation
  • represented using histogram
  • e.g. height of plant
• discontinuous variation

  controlled by one or two genes and often not affected by environment

  • distinct categories
  • represented by bar chart
  • e.g. blood group, eye colour
• natural selection

  1. new alleles for a gene created by random mutations
  2. presence of an advantageous allele means an individual is better adapted to survive a selection pressure
  3. more likely to survive and pass allele on
  4. the new allele increases in frequency in the population
• phylogenetic classification


  arranges species into groups according to evolutionary origins and relationships
• what is a hierarchy?

  • smaller groups arranged within larger groups
  • no overlap between groups