BIO

• Fungi


  A monophyletic group, spore-producing eukaryotic heterotrophs with chitinous cell walls
• Fungi are vastly diverse organisms
• Fungi

  • Eukaryotes -true nucleus and other organelles are present
  • Distinct from other kingdoms of life due to their traits: the way they obtain nutrition and their body structure
  • Reproduces sexually and asexually
  • Lives on the food
  • Presence of mycelium
  • Presence of arbuscules (specialized branching hyphae) that are used to exchange nutrients between fungi and their plant hosts —mostly occurs in mutually beneficial relationships (mycorrhizae)
• Mycelium


  An interwoven mass of fungal hyphae
• Mycelium


  • Infiltrates the food source, making a very efficient feeding by increasing the surface-to-volume ratio
• Unicellular (single-celled) fungi


  Yeasts often grow and thrive in moist environments where there is abundant supply of soluble nutrients, such as sugars and amino acids
• Multicellular (multi-celled) fungi


  • Have enhanced ability to absorb nutrients from their environment due to the presence of hypha (a network of tiny filaments)
  • Such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms)
• Heterotrophic nutrition


  Fungi can't make their own food, dependent on other food sources
• Types of heterotrophy in fungi

  • Saprophytes or saprobes - feed on tissues or organic waste (decomposers)
  • Symbionts - mutually beneficial relationship between a fungus and another organism
  • Parasites - feeding on living tissue of a host
• Heterotrophic absorption

  1. Fungi get carbon from organic sources

  2. Hyphal tips release enzymes

  3. Enzymatic breakdown of substrate (hydrolytic)

  4. Products diffuse back into hyphae
• Fungal body structure

  • Has two types of body structures: multicellular and unicellular (yeasts)
  • Most grow only as filaments, others grow as both filaments and unicellular, and few grow only as unicellular
• Hyphae


  • Consists of chitinous tubular cell walls that enclose the cell membrane and cytoplasm of the cells
  • The component chitin strengthens the cell walls and enhances absorption of nutrients from the surroundings
  • Tubular
  • Cell wall made of chitin
  • Multinucleate (more than 1 nucleus)
  • Cross Walls may form compartments
• Hyphal growth


  • Mycelium - extensive, feeding web of hyphae; aggregation of hyphae
  • Hyphae grow from their tips
• Types of hyphae

  • Septate hyphae - Presence of cross-walls called septa that divide a hypha into cells (thus, segmented)
  • Coenocytic (aseptate, does not have comportments) hyphae - Has a continuous cytoplasmic mass due to the absence or lack of septa
• Septate hyphae


  • The septa serves as: Have pores that allow the flow of nutrients throughout the entire mycelium, Increase the stability of a hypha, and preserve the rest of the hypha when one of its cells is injured
• Coenocytic hyphae


  • The absence of septa allows a quick transport of nutrients throughout the entire hypha
• Mycorrhizal fungi


  • Improve the delivery of nutrients from the soil to the plants (plants supply the fungi with organic nutrients in return)
  • Contains specialized branching hyphae such as arbuscules that are used to exchange nutrients between fungi and their plant hosts
  • Mutualism between: Fungus (nutrient & water uptake for plant) and Plant (carbohydrate for fungus)
• Types of mycorrhizal fungi

  • Ectomycorrhizal fungi - Hyphae does not penetrate the root cells, Forms a network of hyphae over the surface of the plant roots
  • Arbuscular Mycorrhizal fungi - Also known endomycorrhizal fungi, Hyphae penetrates root cells, Extends their hyphae through the cell wall of the plant roots
• Major groups of fungi

  • Phylum Chytridiomycota (Chytrids)
  • Phylum Zygomycota (Zygomycetes)
  • Phylum Glomeromycota (Glomeromycetes)
  • Phylum Ascomycota (Ascomycetes)
  • Phylum Basidiomycota (Basidiomycetes)
• Phylum Chytridiomycota (Chytrids)


  • Earliest lineage (most primitive) of fungi
  • Only phylum with members with flagellated spores and have a coenocytic hyphae
  • Reproduce asexually by zoospores that are produced in zoosporangia
  • Common in lakes, ponds, and soils
• Phylum Zygomycota (Zygomycetes)


  • Hyphae invade root cells (endo)
  • Zygomycetes have coenocytic hyphae
  • Presence of protective zygosporangium as sexual stage (where zygotes produce haploid spores through meiosis
  • Commonly known as Bread Molds or common molds that grow on meat, cheese, and bread
• Phylum Glomeromycota (Glomeromycetes)


  • Glomeromycetes form arbuscular mycorrhizae with plants
  • Have coenocytic hyphae
• Biodiversity


  The number and variety of living things to be found in the world/ecosystem/habitat
• Biodiversity is essential in maintaining a balanced ecosystem for all organisms
• Biodiversity is a global perspective
• Organisms need to diversify as it is essential for organisms to evolve
• Measuring Biodiversity


  Plays an important role in conservation
• Environmental Impact Assessments (EIA)

  Undertaken to predict the positive and negative effects of a project on the biodiversity of an area
• Levels of biodiversity


  • Habitat diversity (y diversity/gamma diversity)
  • Species biodiversity (diversity of flora and fauna found in specific habitats)
  • Genetic biodiversity
• Habitat Biodiversity


  Number of different habitats in an area
• The greater the habitat diversity, the greater the species diversity
• Natural habitats


  • UK - large number of habitat types (e.g Meadow, woodland, stream, sand dune) —large habitat biodiversity
  • Antarctica - low number of habitat types (e.g ice sheet - low habitat biodiversity) —low habitat biodiversity
• Species Biodiversity


  Number of different species and the abundance of each species in an area
• Species richness (a diversity)

  Number of species present in a habitat
• Species evenness


  Measure of abundance of individuals in each species (ACFOR) —a useful tool in ecology for quickly gauging the abundance of species in an area and helping to monitor changes in biodiversity over time
• The greater the species richness and evenness, the higher the biodiversity
• Genetic Biodiversity


  Genetic variation between individuals of the same species (variation of alleles)
• The greater the genetic biodiversity within a species, the more adaptable it is to changing environments
• Simpson's Index of Diversity

  Measures the biodiversity of a habitat, taking the species richness and species evenness into account
• Formula for Simpson's Index of Diversity

  n = number of individuals of a particular species (or percentage cover for plants)

  N = total number of all individuals of all species (or percentage cover for plants)