Fungi, Algae and Protists: Structure, Classification and Uses

Fungi, Algae and Protists

Fungi

Fungi are eukaryotes that can be unicellular or multicellular. Normally they are multicellular, although some forms are unicellular. Fungi are a group of cells that form filaments called hyphae, which join together to form a mycelium.

Fungi are heterotrophs, meaning they obtain nutrients from other organisms. They can be:

• Saprophytes: obtain organic nutrients from dead organic matter.
• Parasites: obtain nutrients from living organisms.

Fungi reproduce by means of spores. The spores are dispersed by the wind, water and animals, and can settle in very distant places.

Classification of Fungi

• Zygomycetes: have saprophytic or parasitic forms (for example, bread mold and fruit mold). Their members do not have caps.
• Ascomycetes: their members produce spores in sacs called asci. They can be unicellular (yeast) or multicellular (for example, truffles).
• Basidiomycetes: their members have caps. Examples include mushrooms, rusts and smuts. They cause diseases in plants.

Algae

Algae are living organisms that are eukaryotic and autotrophic. They can be multicellular or unicellular, and they carry out photosynthesis. They colonize land and both salt and fresh water, and they form part of the plankton. Algae can live independently or form algal colonies.

There are three main groups of algae: green algae, brown algae and red algae.

Uses of Algae and Fungi Today

• Food industry: used to make foods such as soups, among others.
• Cosmetic industry: used to manufacture lipsticks, creams, and other products.
• Pharmaceutical industry: used to manufacture medicine capsules and other drugs.
• Agar: a nutrient medium used to grow bacteria and yeasts in the laboratory.

Harmful and Beneficial Fungi

Some fungi are not safe to eat, and some are poisonous and can cause death. Others are useful: Penicillium produces antibiotics, which are extracted and used to control diseases caused by bacteria. However, some fungi also cause diseases and destroy stored food.

Symbiotic Relationships

• Mycorrhizae: fungi that live in the roots of some plants. They help the plant obtain minerals from the soil, while the plant provides organic nutrients to the fungus.
• Lichens: a relationship between a fungus and an alga. They grow on rocks, trees and other surfaces. Lichens are pioneer organisms in ecosystems: they break down rock, which allows other organisms to live there. They are sensitive to environmental pollution.

Prokaryotes and Eukaryotes

Prokaryotic cells lack a membrane-bound nucleus; their genetic material is free in the cytoplasm. Eukaryotic cells have a membrane-bound nucleus that contains their genetic material.

Protists

Protists are unicellular or simple multicellular eukaryotic organisms. They are mostly aquatic and can live in salt water as well as fresh water. Some are parasites living inside other organisms. Some are heterotrophs that feed on other organisms or on dead organic matter in water.

Locomotion Structures in Protists

• Cilia: short hair-like structures that cover the surface of the cell and move water around it.
• Flagella: long, single structures that produce movement and cause the organism to move.
• Pseudopodia: extensions of the cytoplasm that change the cell's shape and allow it to move.