18.06 Kingdom Fungi

Overview

• The kingdom Fungi consists of eukaryotic organisms that differ significantly from plants, despite some similarities (e.g., having cell walls).
• Key Distinction: Fungi are heterotrophic and cannot photosynthesize. They obtain energy by decomposing dead matter or parasitizing living organisms.

Characteristic Features of Fungi

1. Eukaryotic:

• Cells have nuclei and membrane-bound organelles.

1. Lack Chlorophyll:

• Cannot perform photosynthesis.

1. Heterotrophic Nutrition:

• Obtain energy and organic compounds by:
  • Saprotrophic feeding: Breaking down dead/decaying matter.
  • Parasitic feeding: Extracting nutrients from living hosts.

1. Reproduction:

• Produce spores as reproductive units.
• Fruiting bodies (e.g., mushrooms) are large masses of hyphae that release spores.

1. Body Structure:

• Unicellular (e.g., yeasts) or multicellular.
• Multicellular fungi consist of hyphae:
  • Long, thread-like structures.
  • May have cross walls (septate) or lack them (aseptate).
  • Hyphae collectively form the mycelium (fungal body).
• Some produce compact fruiting bodies to disseminate spores.

1. Cell Wall Composition:

• Made of chitin or other substances (not cellulose).

1. Cilia Absent:

• Fungi never have cilia for movement.

Ecological Role

• Decomposers:
  • Play a crucial role in recycling nutrients by breaking down organic matter.
• Parasitism:
  • Some fungi cause diseases in plants, animals, and humans.

Examples

• Microscopic Fungi:
  • Yeasts: Unicellular fungi used in baking and fermentation.
• Macroscopic Fungi:
  • Honey Fungus (Armillaria bulbosa):
    • Possibly the world’s largest organism (spans 160,000 m² in Wisconsin).
    • Estimated mass: 100 tonnes; age: 1,500–10,000 years.
  • Puffball Fungus (Lycoperdon perlatum):
    • Produces fruiting bodies that release millions of spores (Figure B).

A) Honey Fungus (Armillaria bulbosa):

B) Puffball Fungus (Lycoperdon perlatum):

FIGURE

• Figure C: Depicts hyphae structure and formation of the mycelium.

Key Term

• Fungi: A kingdom of eukaryotic, heterotrophic organisms with cell walls made of chitin (not cellulose), reproducing by spores and having simple body forms.

Summary

• The kingdom Fungi encompasses diverse organisms with unique features:
• Eukaryotic, heterotrophic, spore-producing, and with chitin-based cell walls.
• Includes both microscopic (yeasts) and macroscopic species (e.g., mushrooms, puffballs).
• They are crucial to ecosystems as decomposers and sometimes act as parasites.