Biology module 4

• Biodiversity


  The variety of living organisms
• Over time the variety of life on Earth has become more extensive but now it is being threatened by human activity such as deforestation and agriculture as well as climate change
• Species richness


  The number of different species in a community
• Pathogens


  Bacteria and viruses are the main disease causing pathogens in humans
• Methods of sampling to measure species richness

  1. Random sampling

  2. Systematic sampling (transect)

  3. Opportunistic sampling

  4. Stratified sampling
• Species evenness


  A comparison of abundance of different species in a habitat
• Bacteria


  • Prokaryotic cells with no membrane bound organelles and circular DNA
  • Do not require a host to survive
• Genetic diversity


  The number of alleles in a gene pool, can be determined by calculating the heterozygosity index (H)
• Viruses


  • Consist of nucleic acid enclosed in a protein coat, can have DNA or RNA
  • Entirely dependent on their hosts and cannot survive without them
  • Significantly smaller than bacteria
  • Possess no cell membrane, cell wall, cytoplasm or organelles

  
• Index of diversity (D)

  D = Diversity index, N = total number of organisms, n = total number of organisms of each species
• Bacterial disease


  • Tuberculosis (TB)
• Viral disease


  • HIV/AIDS
  • Influenza
• Maintaining biodiversity is important for ecological, economic and aesthetic reasons such as protecting landscapes
• Methods of conserving biodiversity

  • In situ (marine conservation zones, wildlife reserves)
  • Ex situ (zoos, seed banks, botanic gardens)
• Methods used by zoos to conserve endangered species

  1. Scientific research

  2. Captive breeding programmes

  3. Reintroduction programmes

  4. Education programmes
• Other diseases


  • Athlete's foot (fungus)
  • Malaria (vector - female Anopheles mosquito)
• Seed banks


  Store a large number of seeds to conserve genetic diversity and prevent plant species from going extinct
• Plant diseases


  • Tobacco mosaic virus
  • Potato blight (fungus)
  • Black Sigatoka (banana fungus)
• Agreements for biodiversity conservation

  • Convention on International Trade in Endangered Species (CITES)
  • Rio Convention on Biological Diversity (CBD)
  • Countryside Stewardship Scheme (CSS)
• Plant physical defences


  • Cellulose cell walls
  • Lignin layer
  • Waxy cuticles
  • Blocked old vascular tissue
• Classification


  The process of naming and organising organisms into groups based on their characteristics

  
• Kingdoms of organisms


  • Animals
  • Plants
  • Fungi
  • Prokaryotes
  • Protoctists
• Plant response to pathogen detection

  1. Closing stomata

  2. Additional cell wall thickening

  3. Callose deposits

  4. Necrosis (cell death near infection site)

  5. Canker (necrosis of woody tissue)
• Plant chemical defences


  • Terpenoids (e.g. menthols)
  • Phenols (e.g. tannins)
  • Alkaloids (e.g. caffeine, morphine)
  • Defensins
  • Hydrolytic enzymes (e.g. chitinases)
• Binomial system


  The first part of the name is the genus and the second part is the species
• Animal physical defences


  • Skin (keratin)
  • Stomach acid
  • Gut and skin flora
• Molecular phylogeny


  The analysis of molecular differences in different organisms to determine the extent of their evolutionary relatedness
• Animal non-specific immune responses

  1. Inflammation

  2. Lysozyme action

  3. Interferon

  4. Phagocytosis

  5. Blood clotting
• Antigen presenting cells


  Phagocytes that display pathogen antigens to activate specific immune response
• Domains of life


  • Bacteria
  • Archaea
  • Eukaryota
• Cells involved in specific immune response

  • B cells
  • T cells
• Memory cells


  Replicate when exposed to pathogen, remain in lymph nodes to provide faster immune response

  
• Cells involved in humoral response

  • B effector/plasma cells
  • T helper cells
• Niche


  The role of a species within the environment
• T killer cells


  Destroy pathogen infected cells

  
• Species which share the same niche compete with each other and a better adapted species survive
• Antibodies


  Globular protein molecules produced by lymphocytes, complementary in shape to specific antigens
• Types of adaptations


  • Anatomical
  • Behavioural
  • Physiological
• Antibody structure


  • Four polypeptide chains linked by disulphide bridges
  • Constant region for phagocyte interaction
  • Variable region for antigen specificity
  • Hinge regions for flexibility
• Natural selection


  Fitter individuals who are better adapted to the environment survive and pass on the advantageous genes to future generations