Kingdom Fungi BIOL 1110

Q1. How do fungi obtain their nutrients?

Fungi are heterotrophic by absorption — they secrete digestive enzymes into their environment and absorb the small organic molecules that result.

Q2. How is this nutritional mode related to fungal ecological roles?

A2. Because they absorb nutrients from organic matter, fungi act as decomposers, mutualists, and parasites, recycling nutrients and sustaining ecosystem energy flow.

Q3. What is meant by the term yeast?

A3. Yeast refers to unicellular fungi that reproduce asexually by budding and live in moist, sugar-rich environments (e.g., Saccharomyces cerevisiae).

Q4. What is the basic body structure of a multicellular fungus?

A4. The fungal body consists of a network of hyphae (filaments) that form a mycelium — a feeding structure with a large surface area for absorption.

Q5. How does the fungal cell wall compare in composition with bacterial and plant cell walls?

A5. - Fungal cell walls: contain chitin (a strong nitrogen-containing polysaccharide).
 - Bacterial cell walls: contain peptidoglycan.
 - Plant cell walls: contain cellulose.

Q6. Do mushrooms represent most of the fungal body? Explain.

A6. ❌ No — the visible mushroom is only the reproductive structure (fruiting body); most of the fungus is the hidden mycelium in the substrate.

Q7. What kind of organism is considered the common ancestor of fungi and animals?

A7. A unicellular, flagellated protist (choanoflagellate-like organism) is thought to be the common ancestor of fungi and animals.

Q8. What evidence supports this hypothesis?

A8. - Molecular data: DNA sequence comparisons show fungi and animals share more genes with each other than with plants or protists.
 - Morphological evidence: Both fungi and animals use chitin (structural or exoskeletal) and store glycogen as energy reserve.
 - Flagellated spores (zoospores) in some fungi resemble animal flagellated cells, indicating a shared ancestor.

Q1. How do fungi form mutualistic relationships with other organisms?

a) With Plants – Mycorrhizae

A1.

• Mycorrhizal fungi form associations with plant roots.

• Fungus benefits: Gains carbohydrates from the plant.

• Plant benefits: Receives minerals (especially phosphorus) and water absorbed by the fungus.

• Types:

  • Ectomycorrhizae: Surround root cells.

  • Arbuscular mycorrhizae: Penetrate root cell walls.

b) With Animals

A2.

• Fungi form mutualistic relationships with some animals, especially insects.

• Example: Leaf-cutter ants cultivate fungal gardens;

  • Fungus benefits: Fed plant material.

  • Ants benefit: Feed on the fungus’ nutrient-rich structures.

• Some fungi also help animals digest cellulose in their guts.

c) With Photosynthetic Microorganisms – Lichens

A3.

• Lichens = fungus + photosynthetic partner (alga or cyanobacterium).

• Fungus benefits: Gains organic carbon (food) from the photosynthetic partner.

• Alga/cyanobacterium benefits: Gains protection, moisture retention, and mineral nutrients from the fungus.

• Lichens are important pioneer species, initiating soil formation on bare surfaces.

Q2. What are examples of pathogenic fungi?

A4.

Host Type	Example	Effect on Host
Plant	Claviceps purpurea (ergot fungus on rye)	Produces toxins → reduced yield and poisoning in animals/humans.
Animal (Human)	Candida albicans or Aspergillus	Causes infections (yeast infections, respiratory illness); can be fatal in immunocompromised hosts.

Q3. What are three ways in which humans benefit from fungi?

A5.

1. Decomposers & Nutrient Cycling:

   • Break down organic matter → release nutrients → enrich soil and sustain ecosystems.

2. Food & Beverage Production:

   • Used in making bread, beer, wine, cheese, and soy products (Saccharomyces cerevisiae).

   • Edible mushrooms as food sources.

3. Medicine & Biotechnology:

   • Antibiotics (e.g., Penicillium → penicillin).

   • Immunosuppressants (e.g., cyclosporine).

   • Used in research, genetic engineering, and bioremediation.