2.1

• Phylogenetic tree


  Shows how organisms are related by showing their common ancestors
• Biological classification


  • Phylogenetic: reflects the evolution of organisms
  • Hierarchical: smaller groups placed into larger ones with no overlaps, called taxa
• Domains


  • Archaea
  • Eubacteria
  • Eukarya
• Kingdoms


  • Plantae (plants)
  • Animalia (animals)
  • Fungi
  • Prokaryotes (bacteria)
  • Protoctista
• Protoctists


  • Mainly unicellular eukaryotic microorganisms that do not form tissues
  • Many are photosynthetic, e.g. algae
• Phyla


  • All members have certain things in common, e.g. chordates all have a spinal cord
• Classes


  • Sub-groups of a phylum, e.g. mammals are a class within chordates
• Orders


  • Sub-division of a class, e.g. humans belong to the order of primates
• Families


  • Sub-division of an order
• Genera


  • A group of organisms with a large number of similarities, but members of different species within a genus are usually unable to interbreed successfully
• Species


  • A group of similar individuals that can interbreed and produce fertile offspring
• Binomial system


  Naming system introduced by Carl Linnaeus in 1735, where each organism has two names: genus and species
• Classifying organisms helps infer evolutionary relationships and manage the large number of organisms
• Classification is tentative and may change as new species are discovered that do not fit neatly into current groups
• Five kingdom system


  • Plantae
  • Animalia
  • Fungi
  • Prokaryotes
  • Protoctista
• Plantae


  • Multicellular eukaryotic organisms that photosynthesise
  • Reproduce using spores or seeds
  • Possess cellulose cell walls
• Animalia


  • Multicellular, heterotrophic, eukaryotic organisms
  • Lack cell walls
  • Show nervous coordination
• Fungi


  • Multicellular or single celled eukaryotic organisms
  • Cell wall made of chitin
  • Heterotrophic, either saprophytic or parasitic
  • Reproduce by spores or budding
• Prokaryotes


  • Microscopic, unicellular organisms including bacteria and cyanobacteria
  • Cell wall made of peptidoglycan
  • Lack membrane-bound organelles and true nucleus
  • Ribosomes smaller than eukaryotes
• Protoctista


  • Includes algae and slime moulds
  • Some unicellular and resemble animal cells, others colonial and plant-like
  • Contain membrane-bound organelles and a nucleus
• Homologous structures


  Similar structures that have evolved from a common ancestor, e.g. pentadactyl limb in vertebrates
• Analogous structures


  Structures with the same function but very different shape/structure, e.g. wings of birds and butterflies
• Comparing DNA sequences confirms evolutionary relationships, e.g. chimpanzee is our closest ancestor
• Non-coding regions in eukaryotic DNA


  Contain short DNA sequences that repeat, forming the basis of genetic fingerprinting
• Species richness


  Measure of the number of different species in a community
• Biodiversity


  Combination of species richness and the number of organisms within each species
• Biodiversity increases from poles to equator, due to higher light intensity and water availability
• Factors affecting biodiversity


  • Succession
  • Natural selection
  • Human activity (pollution, overfishing, deforestation, monoculture)
• Simpson's diversity index


  Measures the number of individuals of each species and the number of species
• Polymorphic loci


  Gene positions on chromosomes that have two or more alleles, resulting in different phenotypes
• Natural selection is the process by which new species are formed from pre-existing ones over time
• Adaptations


  • Anatomical, e.g. beak shape
  • Physiological, e.g. haemoglobin affinity
  • Behavioural, e.g. nocturnal
• What are the three domains?

  Eubacteria

  Archaea

  Eukarya
• Five kingdoms


  • Prokaryotae
  • Animalia
  • Plantae
  • Fungi
  • Protoctista
• It is important to learn how to spell these kingdoms correctly, especially Protoctista
• Prokaryotae


  • Cells without a membrane-bound nucleus or membrane-bound organelles
  • Have 70S ribosomes and a cell wall of peptidoglycan (murein)
  • Unicellular
  • Some are heterotrophic while others are autotrophic
• Animalia


  • Multicellular eukaryotic organisms
  • Cells do not have cell walls
  • All heterotrophic and have holozoic nutrition, digesting food internally
  • Have nervous co-ordination
• Plantae


  • Multicellular eukaryotic organisms
  • Have cell walls made of cellulose
  • Autotrophs, using sunlight as a source of energy to make organic molecules by photosynthesis
• Fungi


  • Can be multicellular or unicellular, but they are all eukaryotes
  • Have cell walls made of chitin
  • All heterotrophic and feed saprophytically by secreting enzymes extracellularly onto food
  • Multicellular fungi grow in long threads called hyphae (all the hyphae together are a mycelium)
  • All fungi reproduce by spores
• Protoctista


  • Unicellular eukaryotic organisms
  • Cells may gather to form a functioning unit like a seaweed but there is no tissue differentiation
  • May be heterotrophic, autotrophic or both
  • Very diverse grouping