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Lecture 16
Department
Biological SciencesCourse Code
BIO SCI 94Professor
Brad HughesLecture
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2/11/19
Introduction
● Fungi- mostly multicellular eukaryotes
● Feeding method-absorb nutrients from living/dead organisms
○ Feed on dead=most important decomposers
■ Unique ability-absorb cellulose/lignin that make up wood
● Some fungi parasites
○ Absorb host’s nutrients→ lower host’s fitness
● Mutualists-fungi live with other organisms, benefit hosts
● Mutualistic fungi colonize roots of land plants
○ Fungi get sugar from plants→ give plant water/nutrients
● Fungi produce toxic compounds→ repel herbivores
● Fungi live in guts of insect→ help with digestion
● Insects grow fungi→ cultivate/feed on fungi
● Fungi-master traders/recyclers
○ Some release nutrients from dead plants/animals
○ Some transfer to plants
● Recycle/transfer nutrients→ influence productivity/biodiversity
Why Do Biologists Study Fungi?
● Some fungi cause horrible diseases in humans/crop plants
● Some fungi nourish plants we eat
● Fungi important to carbon cycle→ affect climate change
Fungi Have Important Economic Impacts
● 2000 parasitic fungi species- cause human illness
○ Includes athlete’s foot, vaginitis, diaper rash, ringworm, pneumonia, thrush
○ Fungal infections uncommon compared to other illnesses caused by other
organisms
● Major destructive impact on food supply
○ Fungi cause fruit/vegetable spoilage
○ Fungi-rusts, smuts, mildews, wilts, blights-cause billions of dollars of crop
losses each year
● Fungi-cause of epidemics
○ Killed 4 billion chestnut trees
○ Tens of millions of American Elm Trees
● Fungi- many beneficial impacts too
○ Source of antibiotics, including penicillin
○ Many cultures eat mushroom
○ Yeast used to make bread, cheese, soy sauce, tofu, beer, wine, other food
○ Fungi ferment cacao seeds to make chocolate
○ Fungi enzymes improve foods like fruit juice, candy,
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Fungi Provide Nutrients for Land Plants
● Mycorrhizal association between fungi and plants roots help plant growth
○ Experiments reveal without fungi plant growth suffers
● Plants grow better alongside mycorrhizal fungi
Fungi Accelerate the Carbon Cycle on Land
● Saprophytes-fungi digest dead plant material
● Carbon cycle- two basic components:
○ Fixation of carbon by land plants
○ Release of CO2 from plants, animals, fungi from cellular respiration
● Fungi connect two components
○ Fungi digest lignin/cellulose→ carbon atoms recycle into glucose/CO2
■ Without fungi, carbon atoms stuck in wood for millennia
How Do Biologists Study Fungi?
● 110,000 fungi species discovered
○ Hundreds more found every year
● Known species tiny fraction of estimated total of 1.5 millions species
○ 650 fungi species found in guts of 27 species of beetle
Analyzing Morphological Traits
● Fung- simple bodies
● Two growth forms exist
○ Single celled forms- yeasts
○ Multicellular filamentous forms mycelia
● Some species have both forms
The Nature of the Fungal Mycelium
● Mycelium are dynamic
○ Grow in food sources, die when food runs out
● Hyphae- long, narrow, branching filaments that make up mycelium
● Septa- cross walls separating filaments into cells
○ Pores-gaps in septa, allows materials to flow between compartments
■ Nutrients move through pores- from regions of uptake to regions of
growth
● Some fungi coenocytic-lack septa
○ Species are single, gigantic, multinucleate cell
Mycelia Have a Large Surface Area
● Hyphae thin→ mycelium penetrate tiny fissure in soil→ absorb nutrients plant
roots can’t get
● Mycelia made of network of thin hyphae
○ Fungi-largest area to volume ratio in multicellular organisms
○ Efficient nutrient/water absorption
○ Fungi prone to dying out
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