Introduction to the ecology of fungi
Fungi differ from plants since they cannot manufacture their own food from sunlight and they differ from animals since they do not consume their food directly but absorb nutrients through their cell walls. Their nutrition is thus absorptive and the process normally includes the release of enzymes which break down materials and the subsequent absorption of nutrients in solution. For most species of fungi the cells are arranged in long strands called hyphae. These have the ability to grow over large areas and into tiny spaces and are the functionional living unit of the fungus. The things we see as fungi are only the fruiting structures and their sole purpose is to release spores and propagate te fungus.
Because they cannot manufacture their own food fungi have to survive by using any of three basic strategies:
- they may break down dead organic matter
- they may be parasitic on other living organisms
- they may be mutually symbiotic with other organisms.
These various activities of fungi have an enormous impact on the natural world as well as human affairs. Fungi are the primary decomposers in natural ecosystems and without their activities much dead material would accumulate and nutrient recycling would be limited. In particular, one major component of plant cell walls known as lignin, which is responsible for the hardness of wood, is only significantly broken down by some fungi.
Fungi assist plant growth in other ways. The roots of most plants have intimate relationships with fungi known as mycorrhizae in which the fungus provides important nutrients such as phosphorous and nitrogen without which the plant could not grow. In these cases the fungus is better at securing nutrients than plant roots because it can efficiently scavenge a greater volume of soil with its fine hyphae and it is able to actively break down materials. In return the fungus gains simple sugars produced by the plant by photosynthesis.
Many fungi are parasitic on plants and other organisms though and as crop pests fungi have sometimes had disastrous effects on our food supplies. It is estimated that approximately 10% of world food production is lost on account of fungal pests. On the other hand the antibiotic revolution which has saved millions of lives first started with the discovery of the antibacterial properties of penicillin. We also use fungi extensively in food manufacture to produce alcohol, bread, cheeses and much besides.
In summary, fungi have an enormous impact on the world but this is largely overlooked simply because they are mostly microscopic or their activities are hidden from us.