lecture 19: fungi Flashcards
Morphology of fungi?
Mostly multicellular, some unicellular (yeast), some can change between
Cell wall?
Yes, made of CHITIN (unique in fungi)
Mode of nutrition?
Chemoheterotrophs —> extracellular digestion and absorptive feeding (release chemicals to break down organic material and then absorb them)
Oxygen requirement of fungi?
Mainly aerobic, some yeast are facultative anaerobes
Reproduction of fungi?
Asexually or sexually (using spores)
Motility?
Not motile, but tropism (grow in direction of food) & dispersed by spores
Unique characteristics of fungi?
- Body structures made of a network of thread-like filaments of cells called HYPHAE
- Cell walls made of chitin
- After mating, cells are heterokaryotic (contain 2 or more genetically distinct nuclei in one same cell) before fusion of nuiclei
- Can reproduce sexually, but most do not produce gametes/any flagellated cells
Are fungi more closely related to plants of animals? Why?
Before: considered plant-like
Now: actually more closely related to animals —> share recent common ancestor
- DNA sequence data
- Some animals and all fungi synthesize chitin
- Animal flagella and flagella in some fungi = similar in structure and function
- Both store glucose as glycogen
Where do you find fungi?
- Moist terrestrial ecosystems (large network of filaments undergound), some aquatic
- Fruiting bodies = aboveground (like mushrooms)
2 growth forms/bodies of fungi
- Yeast: single-celled forms
- Mycelia: multicellular, filamentous forms
Some fungi can adopt both forms during their lifecycle
What is hyphae? Types?
Form vegetative (non-reproductive = spaced out hyphae)) & reproductive structures (dense hyphae) of multicellular fungi
- Septate (divided) hyphae: each filament is separated into cell-like compartments by cross-walls called SEPTA with gaps called PORES that enable materials to flow between compartments
- Coenocytic hyphae: no division between cells —> produced by mitosis without cytokinesis —> multiple nucleus in a cell
What is the body of fungi composed of? What does this material give to fungi?
Mycelium: branching networks of very thin hyphae:
- Gives highest surface-area-to-volume ratio —> increases efficiency of absorption
- Allows fungal mycelia to penetrate tiny fissures in soil and absorb water and nutrients that are inaccessible to other organisms
Downside of mycelia?
Makes absorption extremely efficient, but makes fungi prone to desiccation —> Higher surface area so more water loss —> Fungi = restricted to moist, underground habitats
How does mycelia allow fungi to do?
- Allow fungi to absorb nutrients
- Mycelia = adaptation to the absorptive lifestyle of fungi
- Fungi secrete digestive enzymes & can absorb the products via the mycelium
What are spores?
Fundamental reproductive cell in most fungi
- Vehicles of dispersal of gametes
- Produced in huge number in specialized structures during both asexual and sexual reproduction phases
- Can germinate into new mycelia
How are fungal life cycles unusual? (3)
- Body cells = haploid (n), only diploid cell (2n) = short-lived zygotes
- Can form heterokaryotic cells (contain haploid nuclei from 2 different individuals) during sexual reproduction
- Most species reproduce sexually, but few produce gametes
How are fungi diverse? (2)
- Different ways to absorb food from environment
- Different ways to reproduce —> four types of distinctive reproductive structures —> ex: fruiting bodies aboveground —> thick, fleshy structures
Ecological roles of fungi (4)
- Important decomposers in terrestrial ecosystems
- Important mutualists with plants and other organisms
- Parasites of plants and animals
- Food for other organism
What do fungi do as decomposers? What fungal species is an important decomposer?
- Saprophytic fungi, in terrestrial ecosystems
- Dispersed via spores/grow towards dead tissue to digest & absorb nutrients
- Particularly important in digestion of WOOD
- Produce digestive enzymes that can hydrolyze:
1. Cellulose: structural polysaccharide in cell walls of plant cells
2. Lignin: extremely hard to break down, complex structural polymers in cell walls of some plant cells (ex: wood)
What is “mycorrhiza”? (FINAL)
Mutualism between fungi and plants
- Plants provides SUGARS from photosynthesis
- Fungi provide water & key nutrients from soil (nitrogen and phosphorus nutrients)
- Roots of virtually every land plant = colonized by mutualistic fungi —> have huge impact on their growth
Mutualism between fungi and lichen (FINAL)
Lichen = photosynthetic partner (cyanobacterium or algae)
- Lichen provides SUGARS
- Fungi provides protection from desiccation and nutrients that it traps from the air
- Lichen partners = so dependent on each other that most cannot survive if separated
Importance of lichens (3)
- Lichens = pioneers in barren areas and initiate soil production
- Primary food source of many animals
- Used in production of dyes and perfumes
How can fungi be parasites?
Cause illness in humans: athlete’s foot, diaper rash, ringworm, vaginitis, pneumonia
- Opportunistic pathogens: become parasites if our immune system is weaker —> fungal infections can be serious in immunocompromised human hosts and cause opportunistic infections
Impact on humans?
- Rot food
- Cause disease in plants and animals
- Produce important products
- Research, medicine, and biotechnology
