Diversity of organisms

• Variation


  • Differences in traits between individuals
  • No two individuals are identical in all their traits
• Taxonomy


  The science of classifying organisms
• Morphology


  Classification by physical traits, done by Linnaeus
• Binomial system


  • Genus in capitals and italics
  • Species in lowercase and italics
• Biological species concept


  • Group of organisms that can breed and produce fertile offspring
  • Some special cases that are meant to be infertile are fertile
  • Speciation may occur due to reproductive isolation, splitting one species into two new ones
• Diversity in chromosome numbers

  • Humans have 46
  • Chimpanzees have 48
  • Diploid cells have an even number of chromosomes
  • Jack jumper ants have 2
  • Black mulberry plants have 308
• Karyotyping and karyograms


  • Number and type of chromosomes found in a cell
  • Autosome - non sex chromosomes (humans have 22 pairs)
  • Karyograms - diagram of the chromosomes found in a cell, arranged into homologous pairs
  • Homologous chromosomes have the same gene sequence and length
• XY - male


  XX - female
• Trisomal


  Extra chromosome
• Origin of human chromosome

  • Chimpanzees are our closest relative
  • Chromosome 2 may have been formed from two small chromosomes (12 and 13)
  • Genes on 2 match the 2 suspected fusion chromosomes in chimpanzees
  • Telomeric DNA usually found at the ends was found as the theorized fusion region
  • There are 2 centromere regions
  • The human chromosome matches the length of the two chimpanzee ones
  • Sequence matches
  • Banding patterns when dyed is the same
• Genome


  All the genetic material in the cell
• Proteome


  Proteins that are expressed
• Uses of genome sequencing


  • Personalized medicine for specific genomes
  • Diagnosis and treatment of genetic diseases, can focus on prevention
  • Prescribe more effective drugs with less side effects
  • Reduces trial and error prescription using targeted medications
  • Find misconceptions
• Polymorphism


  The existence of multiple forms of a particular trait or characteristic within a species
• Polymorphism can result from single nucleotide base substitution mutation
• Problems with the biological species concept

  • Asexual reproduction - do not interbreed (binary fission, hydra)
  • Horizontal gene transfer - transfer of genes between unrelated species of bacteria
  • Cross breeding between closely related species is very unlikely if the chromosome number is not the same
  • Chromosomes need to line up in homologous pairs during meiosis
• Dichotomous key


  • N-1 pairs where n is the number of different organisms
  • 1a animal has... go to...
  • 1b animal does not have... go to...
  • Paired statements
• Environmental DNA barcodes


  1. Unknown specimen

  2. DNA extraction and amplification

  3. DNA sequencing to produce a barcode

  4. Sample compared to database

  5. Match found

  6. Species identified
• Uses of DNA barcoding

  • Discover presence of a species
  • Measure biodiversity
  • Food testing
  • Identify stages of a life cycle
  • Analyze stomach contents
  • Identity species from partial specimens
• Difficulties with traditional tax hierarchy

  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Paradigm shift


  • Change from arbitrary taxa to clades with members that have a common ancestor
  • Reptiles used to be a taxa, does not correspond to divergence patterns in evolution
• Evolution


  Change in heritable characteristics of populations of a species over time