Characteristics of Fungi

Definition: Fungi are members of the kingdom Fungi (pronounced FUN ji; singular: fungus).
Diversity: Over 10,000 species of fungi have been identified, including eating mushrooms and mold on bread.

Eukaryotic Nature:
- All fungi have eukaryotic cells, meaning they possess a true nucleus.
- Presence of membrane-bound organelles is characteristic of fungi.
Heterotrophic Lifestyle:
- Fungi are heterotrophs, which indicates that they cannot synthesize their own food.
- Nutrients are obtained from organic matter.

Multicellular Fungi:
- Multicellular fungi, such as mushrooms, consist of many cells and can resemble plants but belong in a distinct kingdom due to unique features.
Unicellular Fungi:
- Unicellular fungi are known as yeasts.
- Yeasts thrive in various environments, including soil, plant surfaces, sugary substances, and the human body.
- Yeasts are utilized in food production, notably in bread and beer.

Cell Walls:
- Differentiation from plants:
- Plant cell walls are primarily composed of cellulose.
- Fungal cell walls are made of chitin (KI tun), which is a polysaccharide consisting of multiple sugars.
Body Structure:
- Fungi consist of hyphae (HI fee; singular: hypha), which are tubular filaments.
- Hyphae expand from their tips and branched out to create a structure known as mycelium (mi SEE lee um; plural: mycelia).
- Mycelium grows underground and is essential for nutrient acquisition.
- Above ground, fungi present the fruiting body, responsible for reproduction and composed of hyphae.
Septate Structure:
- Many fungi feature cross-walls referred to as septa (singular: septum), which segment hyphae into cells.
- Septa possess pores to facilitate the flow of nutrients and cytoplasm amidst cells.
- Some fungi are aseptate, which allows free movement of materials through their hyphae.

Digestive Process:
- Fungi digest their food externally before assimilation.
- They release digestive enzymes that break down food into smaller molecules beyond their cell walls before absorption.
Decomposers:
- Saprophytic fungi are recognized as decomposers, recycling nutrients from decayed organisms and organic waste materials back into ecological food webs.

Parasitic Fungi:
- Parasitic fungi extract nutrients from a living host.
- They develop specialized hyphae known as haustoria (haws toh REE ah) that penetrate host tissues to absorb nutrients.
Mutualistic Fungi:
- Mutualists are fungi that coexist beneficially with other organisms.
- Example: A fungus enveloping a plant root, drawing sugars from the plant while assisting in mineral absorption.

Modes of Reproduction:
- Fungi can reproduce both sexually and asexually, employing methods such as budding and fragmentation for asexual reproduction.
Budding in Yeasts:
- Yeasts reproduce asexually through a process called budding, where new cells develop while remaining attached to the parent cell; the new cell separates once the plasma membrane pinches off.
Fragmentation:
- Occurs when a part of the mycelium breaks away, potentially leading to the formation of new mycelia under suitable conditions.
Spore Production:
- Spores are vital to both asexual and sexual reproduction, characterized as reproductive cells with protective outer coats.
- They develop into organisms without the requirement for egg and sperm fusion.
- In sexual reproduction, spores are produced via meiosis.
Survival Adaptations of Spores:
- Fungi produce trillions of spores to enhance chances of successful colonization in favorable environments.
- Due to their lightweight nature, spores readily disperse through wind and small animals.
- Hard outer coats serve as protection against harsh environmental conditions.

Fungi classification is primarily based on the type of fruiting body (sporophore) they produce.
Example of structures:
- Some fungi create spores within a protective structure called a sporangium (spuh RAN jee uhm; plural: sporangia), which ensures moisture retention until spore release.