Sign up to access the complete lesson and track your progress!
Unlock This CourseFungi are fascinating organisms that are neither plants nor animals - they belong to their own special kingdom! You've probably seen mushrooms growing in your garden or noticed mould on old bread. These are all examples of fungi and they play crucial roles in our world that you might never have imagined.
Unlike plants, fungi cannot make their own food through photosynthesis. Instead, they have developed clever ways to obtain nutrients from their environment. This makes them incredibly important for breaking down dead material and recycling nutrients in nature.
Key Definitions:
Fungi are unique because they combine features from both plant and animal kingdoms whilst having their own distinct characteristics. They have cell walls like plants, but these walls are made of chitin (the same material found in insect shells) rather than cellulose. They cannot photosynthesise like plants, but they also don't move around and hunt for food like animals do.
To understand fungi properly, we need to look at their key features that make them different from all other living organisms. These characteristics help scientists classify organisms as fungi and understand how they survive and thrive in their environments.
Fungal cells have several distinctive features that set them apart from plant and animal cells. Understanding these structures helps explain how fungi live and feed.
Made of chitin, not cellulose like plants. This makes them strong but flexible, allowing fungi to grow through tough materials like wood and soil.
Fungi cannot photosynthesise because they lack chloroplasts. This is why they must obtain food from other sources rather than making it themselves.
Most fungi grow as thin threads called hyphae, which branch and spread to form a network called mycelium. This gives them a huge surface area for absorption.
The largest living organism on Earth is actually a fungus! The Armillaria ostoyae fungus in Oregon, USA, covers over 2,400 acres (nearly 10 square kilometres) and is estimated to be between 2,000-8,000 years old. Its mycelium network spreads underground, connecting trees across vast distances.
Since fungi cannot make their own food like plants do, they have evolved a unique method of nutrition called saprotrophic feeding. This process is essential for understanding how fungi survive and their role in ecosystems.
Saprotrophic nutrition is like having an external stomach! Fungi release powerful enzymes outside their bodies to break down complex organic materials into simpler substances that they can then absorb. This process happens in several stages and is crucial for nutrient cycling in nature.
1. Enzyme Release: Fungi secrete digestive enzymes onto dead organic matter
2. External Digestion: These enzymes break down complex molecules like proteins, carbohydrates and fats
3. Absorption: The simple molecules produced are absorbed through the cell wall
4. Distribution: Nutrients are transported throughout the mycelium network
Fungi come in many different forms, from tiny single-celled yeasts to massive mushrooms. Each type has adapted to specific environments and plays important roles in ecosystems and human society.
These are the reproductive structures of larger fungi. The main body (mycelium) grows underground or within rotting wood, whilst the mushroom appears above ground to release spores.
Single-celled fungi that reproduce by budding. They're essential for baking bread and brewing, as they ferment sugars to produce carbon dioxide and alcohol.
Fuzzy fungi that grow on food and damp surfaces. Whilst some cause food spoilage, others are useful - like Penicillium, which produces antibiotics.
Fungi are essential in food production worldwide. Saccharomyces cerevisiae (baker's yeast) has been used for thousands of years to make bread rise and ferment alcoholic beverages. In Asia, fungi like Aspergillus oryzae are used to ferment soybeans into soy sauce and miso. Even cheese production relies on fungi - Roquefort cheese gets its distinctive blue veins from Penicillium roqueforti fungus growing throughout it.
Fungi are nature's recyclers and play absolutely crucial roles in maintaining healthy ecosystems. Without fungi, dead material would pile up everywhere and many plants couldn't survive.
As saprotrophic organisms, fungi are primary decomposers in most ecosystems. They break down dead leaves, fallen trees, animal remains and other organic matter, releasing nutrients back into the soil where plants can use them again. This creates a continuous cycle of nutrients that keeps ecosystems healthy and productive.
Many fungi form beneficial partnerships with plant roots called mycorrhizae. The fungus helps the plant absorb water and nutrients (especially phosphorus) from the soil, whilst the plant provides the fungus with sugars from photosynthesis. About 90% of all plant species have these fungal partners!
Fungi have complex relationships with humans - some are incredibly beneficial, whilst others can cause problems. Understanding these relationships helps us use fungi effectively whilst protecting ourselves from harmful species.
Humans have used fungi for thousands of years, often without realising it. Today, we deliberately cultivate and use fungi in many industries, from food production to medicine and biotechnology.
Penicillin, discovered from Penicillium fungi, revolutionised medicine by treating bacterial infections. Many other antibiotics and medicines come from fungi.
Beyond bread and alcohol, fungi are used to make enzymes for food processing, single-cell proteins and even meat substitutes like mycoprotein (Quorn).
Fungi help plants grow better through mycorrhizal relationships and can be used as biological pest control agents instead of chemical pesticides.
In 1928, Alexander Fleming accidentally discovered penicillin when he noticed that a Penicillium mould had contaminated one of his bacterial cultures and killed the bacteria around it. This accidental discovery led to the development of antibiotics, which have saved millions of lives. The fungus produces penicillin as a natural defence mechanism to compete with bacteria for resources - humans simply learned to harness this natural process.
Whilst many fungi are beneficial, some can cause problems for humans, animals and plants. Understanding these harmful effects helps us take appropriate precautions and develop treatments.
Fungal problems can range from minor inconveniences like food spoilage to serious health issues and agricultural disasters. Most harmful effects occur when fungi grow in places where they're not wanted or when they infect living organisms.
Some fungi can cause infections in humans, particularly affecting the skin (like athlete's foot), nails, or respiratory system. People with weakened immune systems are especially vulnerable to fungal infections. However, serious fungal diseases are relatively rare in healthy individuals.