Week 3

• biodiversity

  biological diversity

  • the whole range of life on earth
  • includes different organizational levels, genes, individuals, populations, and ecosystems
• species concepts

  morphological, biological, phylogenetic
• systematic biology

  study of classification
• taxonomy

  science of describing, naming, and classifying species
• phylogenetics


  science studying evolutionary relationships among species
• species

  types/kinds of organisms

  • new species can arise from existing species through evolution
• morphological species concept (MSC)

  defines species as organisms sharing distinct anatomical features that distinguish them from others
• biological species concept


  defines species as organisms that can breed with each other in the wild and produce fertile offspring
• reproductive isolation


  lack of gene flow and genetic changes accumulate until interbreeding is not possible

  • habitat isolation
  • temporal isolation
  • mechanical isolation
  • behavioral isolation
  • chemical isolation
• reproductive barriers

  either pre-zygotic or post-zygotic (before or after a zygote is formed)
• phylogenetic species concept (PSC)

  a species is the smallest group with a distinct evolutionary lineage that can be distinguished from others
• allopatric speciation

  • a barrier physically separates a population into two groups that cannot interbreed
  • with no gene transfer between the two populations, each proceeds down its own evolutionary line
• parapatric speciation

  • part of a population enters a new habitat bordering the range of the parent species
  • expanding population evolve traits that suit the bordering habitat
  • mating can occur between populations, but most individuals mate within their own population
  • characterized by hybrid zone
• sympatric speciation

  • populations diverge genetically while sharing a habitat
  • seen to occur in 2 ways: each species specializes in a unique micro-environment, leading to reproductive isolation; hybridization of 2 species form polyploid offspring with more chromosomes than either parent
• Carl Linnaeus

  proposed a hierarchical, binomial system where each species has a unique combination of Latin paired names which provides ancestry
• phylogenetics


  the study of evolutionary relationships among different groups of organisms
• cladistics

  one method of constructing a tree based on common ancestry
• clade

  a group of organisms that share one or more defining derived traits inherited from a common ancestor
• phylograms

  trees where branch lengths correspond to inferred evolutionary change or genetic distance
• three domains

  bacteria, archaea, eukarya
• four kingdoms

  protista, plantae, fungi, animalia
• bacteria

  • found everywhere
  • important in many natural processes
  • prominent in human medicine
  • reproduce asexually
• domain archaea

  • extremophiles: first found in extremely hot, acidic, or salty environments
  • reproduce asexually
• domain eukarya

  organisms with membrane-bound organelles
• kingdom protista

  • primarily unicellular
  • metabolically diverse
  • structurally complex
  • live mostly in water
• kingdom fungi

  • cell walls with chitin
  • heterotrophs: obtain food by absorption
  • reproduce asexually and by sexual spores
  • classified by reproductive structures
• kingdom plantae

  • cellulose cell walls
  • autotrophic: perform photosynthesis
  • terrestrial plants classified by: tissue structure (non-vascular and vascular), reproductive characteristics
• animalia

  • no cellulose cell walls
  • heterotrophs: obtain energy from other organisms
  • some have complex organ systems
  • able to move about and respond rapidly to stimuli
• viruses


  • replicate inside living cells of other organismal life forms
  • classification based on morphology, type of nucleic acid, host organisms, type of infections/diseases, etc.
• how many species are there

  around 2 million species have been described; estimated to be 7-100 million species in total
• tropical rainforests are believed to be home to ___ of the world's existing species, most of which have yet to be named

  2/3rds
• monocultures lead to

  disease susceptibility
• bio-prospecting

  extracting active compounds for medication
• problems with MSC

  wide variation in appearance in the same "species"
• problems with BSC

  excludes artificial breeding by humans; only applies to sexually reproducing organisms; mating can occur in closely related organisms
• problems with PSC

  level of difference to separate species is not well-defined
• extinction

  extinction is a natural process

  • five mass extinctions in the past
  • fossil record shows that species diversity has been increasing but not steadily
  • periods of high speciation as well as extinction
• Linnaeus

  • Swedish botanist who developed the scientific naming system still in use today
  • unique binomial name for each species
  • taxonomic hierarchy of classification
  • rules set and standardized by scientific associations
• scientific name

  genus + species (italicized) last name, year published

  
• clade


  a group of organisms that share one or more defining derived traits inherited from a common ancestor