TOPIC 5 IB BIOLOGY

• Natural selection


  1. Variation

  2. Advantage

  3. Increase in population
• Taxonomic levels


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Domains of life


  • Bacteria
  • Archaea
  • Eucharia
• Bacteria


  • Prokaryotic cells
  • No true nucleus
• Archaea


  • Prokaryotic cells
  • No true nucleus
• Eucharia


  • Eukaryotic cells
  • Plant / animal/ fungus
• Plant phyla


  • Bryophyte (e.g. moss)
  • Fillcinophyte (e.g. Ferns)
  • Coniferophyte (e.g. conifers and pines)
  • Angiospermophyte (e.g flowering plants and grasses)
• Bryophyte


  • No true leaves or roots
  • Reproduce - spores
  • Anchored by rhizoids
• Fillcinophyte


  • Has leaves
  • Vascularized
  • Reproduce - spores
• Coniferophyte


  • Have leaves
  • Vascularised
  • Reproduce - seeds
• Angiospermophyte


  • Vascularised
  • Reproduce - seeds found in fruit
  • Flowers / fruit
• Animal phyla


  • Porifera (e.g. sponges)
  • Cnidaria (e.g. Jelly fish/ Corals)
  • Platyhelminth (e.g. flatworms and tapeworms)
  • Annelida (e.g. earthworm and leaches)
  • Mollusca (e.g. squids, slugs and snails)
  • Arthropoda (e.g. spider and insects and crustaceans)
  • Chordata (e.g backbones)
• Porifera


  • Sponge
  • Asymmetrical
  • No mouth or anus
  • Pores through body
• Cnidaria


  • Jelly fish, coral
  • Radial body symmetry
  • Mouth but no anus
  • Stinging cells
• Platyhelminth


  • Mouth but no anus
  • Flat and softened body
  • Bilateral
  • Unsegmented
• Annelida


  • Bilateral
  • Mouth and anus
  • Segmented body
• Mollusca


  • Bilateral
  • Mouth and anus
  • May have muscular foot or a shell
• Arthropoda


  • Segmented body
  • Bilateral
  • Mouth and anus
  • Jointed appendages and exoskeletons
• Chordata


  • Post anal tail at some point in time
  • Bilateral symmetry
• Chordata subgroups


  • Fish
  • Amphibians
  • Reptiles
  • Birds
  • Mammals
• Mechanisms by which genetic variation within a population is maintained

  • Mutations - changes to the gene sequence
  • Sexual reproduction - new gene combinations
  • Gene flow - immigration and emigration
• Mechanisms by which population variety can be altered (⬇ biodiversity)

  • Random chance (genetic drift)
  • Directed intervention (natural or artificial selection)
• The impact of a change is greater

  If the population is small (this may occur via population bottlenecks or founder effect)
• Evolution


  The cumulative change in the heritable characteristic of a population (i.e. biological change over time)
• Alleles


  Genes and their variants that are transferred between generations
• Evolution


  A change in the allele frequency of a population's gene pool over successive generations
• Mechanisms of evolution


  • Mutation
  • Sex
  • Gene Flow
  • Genetic Drift
  • Natural Selection
• Speciation


  Occurs when populations diverge to the extent that they can no longer interbreed and produce fertile, viable offspring
• Continuous variation across a geographical range of related populations matches the concept of gradual divergence