Classification and biodiversity

• Classification

  The process of naming and organising organisms into groups based on their characteristics and evolutionary history
• The classification of an organism may change as new information becomes available
• Hierarchy of taxons, from largest to smallest

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Five kingdom classification system

  The classification of organisms into five major kingdoms: Animalia, Fungi, Plantae, Prokaryotae and Protoctista
• Three domain classification system

  A method of classification in which organisms are categorised into three groups; Archaea, Bacteria and Eukarya
• How the three domain system of classification was developed

  1. By analysing molecular differences between organisms to determine their evolutionary relationships

  2. Evidence showed that the kingdom 'prokaryotae' could be divided into two groups. All other organisms are eukaryotes
• Organisms in the same domain


  Share a distinctive pattern of ribosomal RNA
• Bacteria

  One of the three domains, consists of 'true' bacteria, also known as Eubacteria
• Archaea


  One of the three domains, made up of primitive bacteria existing in extreme environments, e.g. extremophile prokaryotes, also known as Archaebacteria
• Eukarya


  One of the three domains, consists of all eukaryotic organisms
• Kingdom Prokaryotae


  • Unicellular prokaryotes
  • Lack a true nucleus and membrane-bound organelles
  • Rigid cell wall
• Kingdom Plantae

  • Multicellular eukaryotes
  • Photoautotrophs
  • Cellulose cell walls
• Kingdom Animalia


  • Multicellular eukaryotes
  • No cell wall
  • Heterotrophic
  • Nervous coordination
• Kingdom Fungi


  • Eukaryotes
  • Heterotrophic
  • Chitin cell walls
  • Grow by producing branching filaments, hyphae
  • Asexual reproduction via spores
• Kingdom Protoctista


  • Mainly unicellular eukaryotes
  • No differentiation into tissues
• How different types of evidence are used in classification

  1. Observations (e.g. fossils) - organisms grouped based on similar physical characteristics

  2. Biochemical methods (e.g. DNA genetic fingerprinting)
• DNA profiling


  • Method of determining the characteristics of an individual's DNA
  • Percentage of DNA or proteins shared between species is used to estimate relatedness
• Advantage of using biochemical methods of classification

  Biochemical methods reduce mistakes made from observing physical features alone (due to morphological convergence)
• Homologous features


  Have evolved from the same structure for different functions, indicating a common ancestor
• Analogous features


  Structures that have evolved independently for the same function
• Homologous feature

  • Pentadactyl limb (found in mammals, birds and reptiles)
• Analogous feature


  • The wings of birds and insects
• Homologous features

  Evolved from the same structure for different functions, indicating a common ancestor
• Homologous feature

  • Pentadactyl limb (found in mammals, birds and reptiles)
• Analogous feature


  • The wings of birds and insects
• Species


  A group of organisms that can interbreed to produce fertile offspring
• Binomial name

  Generic name (Genus) + Specific name (species)
• The advantage of the binomial naming system is that it is universal; an organism's binomial name is the same everywhere in the world
• Biodiversity


  The number and variety of living organisms in a given region, affected by environmental, genetic and human factors
• Natural selection has generated biodiversity
• Species richness


  The number of different species found within an area
• Species evenness


  The number of individuals of each species living together in a community
• Simpson's Diversity Index


  A measurement of diversity that considers both species richness and evenness, with a value between 0 and 1, the greater the value, the greater the biodiversity
• Calculating genetic diversity within a species

  Proportion of polymorphic gene loci = number of polymorphic gene loci / total number of loci
• Polymorphism

  The presence of different phenotypes among members of a single species
• DNA sequencing


  Determining the entire DNA nucleotide base sequence of an organism
• DNA sequencing can be used to measure biodiversity by comparing variations in base sequences between members of the same species to estimate genetic diversity
• Adaptation


  A feature of an organism that increases its chance of survival in its environment
• Types of adaptation

  • Anatomical (changes to physical features)
  • Physiological (changes to bodily processes)
  • Behavioural (changes to actions)
• Biodiversity and atrad Jelether are the driving force bene