We explain what the fungi kingdom is, what its characteristics and classification are. In addition, we explain what its nutrition, reproduction and examples are.
What is the fungi kingdom?
The kingdom fungi is one of the groups in which biology classifies known life forms. It is composed of more than 144,000 different species of fungiwhich include yeasts, molds and fungi, and which share fundamental characteristics such as immobility, heterotrophic feeding and certain cellular structures.
Mushrooms They exist throughout the world and in different habitatsand they appear in different forms and presentations.
Of all the fungi that inhabit our planet, Only 5% has been studied and classifiedand it is estimated that there are around 1.5 million species still unknown. This is partly due to the fact that fungi were once classified as a type of plant, until they began to be distinguished as a separate biological kingdom in the 19th century.
The science that specializes in members of the fungi kingdom is called mycology.
See also: Kingdom Plantae
Characteristics of the fungi kingdom
Members of the kingdom Fungi share the following fundamental characteristics:
- They lack their own mobility. Fungi grow in soil, on surfaces, or on logs or decaying organic matter, depending on their preferences. Like plants, they remain in the same place throughout their lives, unable to move at will.
- They have a cell wall. Fungal cells are eukaryotes, meaning they have a cell nucleus. They also have a rigid cell wall, similar to that of plant cells, but instead of being made of cellulose, it is made of chitin, the same substance that gives insects their hard exoskeletons. In addition, they are elongated cells that can contain several nuclei and have vacuoles but not chloroplasts, since they do not perform photosynthesis.
- They grow like hyphaeFungal growth occurs in the form of hyphae, uniform, cylindrical structures that can range from a few micrometers to several centimeters in length, and can overlap in a branching or bifurcation process. As the hyphae grow, they form a tangled mass or tissue-like network called mycelium.
- They absorb food from the environmentFungi do not ingest food and then digest it in the body like animals do. Instead, they infiltrate a food source and secrete digestive enzymes into it. Digestion takes place outside the body. When complex molecules are broken down into smaller compounds, the fungi absorb the predigested food into their bodies.
- They reproduce by spores.Spores are microscopic reproductive cells that can develop into new organisms. They are usually produced on specialized aerial hyphae or fruiting structures. The structures where spores are produced are called sporangia. The aerial hyphae of some fungi produce spores on large, complex reproductive structures known as “fruiting” bodies. The familiar part of a mushroom is a large fruiting body.
Classification of the fungi kingdom
The classification of fungi has been reworked throughout the history of biology as better recognition techniques have been developed and fungi have been distinguished from other life forms that resemble them. The current classification of the kingdom is as follows:
- Basidiomycete fungi (Basidiomycota)They develop mushrooms (basidiocarps), from which the reproductive spores of the fungus are born.
- Ascomycete fungi (Ascomycota)Instead of mushrooms they have asci, spore-producing sex cells.
- Glomeromycete fungi (Glomeromycota)They are mycorrhizae, that is, symbiotic unions between a fungus and the roots of a plant. The fungus provides nutrients and water, and the roots provide carbohydrates and vitamins that the fungus cannot synthesize.
- Zygomycete fungi (Zygomycota)They are molds that form zygospores, that is, spores capable of withstanding adverse conditions for a long time until they can finally germinate.
- Chytridiomycota fungiThey are microscopic and primitive fungi, generally aquatic, that reproduce by flagellated spores (zoospores).
Nutrition of the fungi kingdom
The nutrition of fungi is always heterotrophic, that is, They cannot generate their own food like plants.but they must decompose organic matter from other forms of plant or animal life. Depending on their nutrition, there are different types of fungi:
- Saprophytic fungiThey feed on the decomposition of remains of organic matter from other organisms (corpses and body waste), whether specific or not, that is, from a certain exclusive type of organic matter or from any type in general.
- Mycorrhizal fungiThey feed through a symbiotic relationship with plants, colonizing their roots and exchanging water and different mineral nutrients, generated by the fungus, in exchange for carbohydrates and vitamins that the fungus is unable to synthesize on its own. This is known as mycorrhiza.
- LichenizedThey feed through symbiotic relationships resulting from the union of the fungus and an algae or cyanobacteria, which establish such a close relationship that they can be considered a single individual. They are similar to mycorrhizae.
- ParasitesThey feed directly on the bodies of other living beings, and to do so they can establish themselves on their surface or colonize the interior of their bodies, which causes these organisms various damages that can be mild or even lethal.
Reproduction of the fungi kingdom
Mushrooms They reproduce sexually and asexuallyalways through the production of spores: forms resistant to the environment that, when optimal conditions are met, germinate and create a new specimen of the fungus. The growth of the hyphae, once the spores have germinated, can be very fast: a tropical fungus grows about 5 mm per minute.
Spores are formed as the last part of asexual (mitosis) or sexual (meiosis) reproduction processes, depending on whether the fungus needs to spread quickly, for which asexual replication is preferable, or whether it requires genetic variation, for which it will require the exchange of genetic material with other individuals of the same species.
Asexual reproduction of fungi
Unicellular fungi, such as yeasts, reproduce asexually through a process called budding: the formation of buds that project from the parent cell.
In multicellular fungi, asexual spores (called conidia) are produced by mitosis on specialized hyphae called conidiophores and then released into the air or water.
Sexual reproduction of fungi
Many fungal species reproduce sexually with various types of mating. In contrast to most animal and plant cells, most fungal cells contain haploid nuclei (nuclei with a single set of chromosomes). In sexual reproduction, the process consists of:
- Hyphae of two genetically compatible mating types meet, and their cytoplasms fuse in a process called plasmogamy.
- The resulting cell has two haploid nuclei: one from each fungus.
- This cell gives rise to other cells with two nuclei by mitosis. At some point the two haploid nuclei fuse. This process, called karyogamyresults in a cell containing a diploid nucleus known as the zygote nucleus. In some groups, the zygote nucleus is the only diploid nucleus.
In the two largest groups of fungi, the Ascomycetes and the Basidiomycetes, plasmogamy (fusion of hyphae) occurs, but karyogamy (fusion of the two different nuclei) does not follow immediately. For a time the nucleus remains separate within the fungal cytoplasm.
Hyphae containing two genetically distinct but sexually compatible nuclei within each cell are described as dikaryoticThis condition is referred to as n + n rather than 2n, because there are two separate haploid nuclei.
Hyphae that contain only one nucleus per cell are described as monokaryotes. The presence of a dikaryotic stage is an important defining characteristic of ascomycetes and basidiomycetes.
Importance of the fungi kingdom
Fungi play an important ecological role in their various niches of appearance, because They help in the decomposition and recycling of organic matter (dead animals or plants, feces, dry and fallen leaves, fallen tree trunks, etc.) along with bacteria and certain species of insects.
On the other hand, Many species of fungi are useful to humanseither as edible species, such as mushrooms, or as decorative species in gardening. Yeasts, for their part, are essential in the processes of making beer, bread and other products because they carry out the biochemical transformation of substances.
Toxic or poisonous mushrooms
There are species of fungi that secrete dangerous toxins, some even They can be fatal if ingested, or if their spores are breathed in.These toxic enzymes can induce conditions in humans or other animals such as tachycardia, vomiting, colic, cold sweat, thirst, bloody stools or even blood pressure imbalance, depending on the amount consumed.
These effects can lead to necrotic damage to the liver and kidneys, which can cause death if not treated properlyIn other cases the toxic effects are mild and may be hallucinogenic.
There is no simple rule to distinguish poisonous mushrooms from edible ones.
Examples of the fungi kingdom
Some common examples of fungi are:
- Brewer's yeast. (Saccharomyces cerevisiae)It is used in the manufacture of bread, beer and wine.
- The mushroom champignon (Agaricus bisporus)It is grown on farms and is part of the regular diet in many countries.
- Athlete's foot fungus (Trichophyton rubrum)It is one of the 42 species of parasitic fungi that can infect human skin when it is constantly exposed to moisture.
- Indian bread mushroom (Cyttaria harioti)It is a species that parasitizes the trunks of trees in South America (Chile and Argentina), and generates yellowish tumors or “knots” that obstruct the sap ducts, as well as edible fruits called “Indian bread.”
- Corn fungus (Ustilago maydis)Also called huitlacoche or cuitlacoche, it is a fungus that grows between corn kernels and generates edible structures that are considered a delicacy in Mexico and other countries.
Continue with: Protista Kingdom
References
- “Fungi” on Wikipedia.
- “Kingdom fungi” in BioEncyclopedia.
- “Fungi (kingdom Fungi): characteristics and classification or types” in Paradais Sphynx.
- “General characteristics of mushrooms” in asturnatura.com.
- “What is a fungus?” (video) at Naked Scientists.
- “Fungus (life-form)” in The Encyclopaedia Britannica.
- Biology: Solomon E., Berg L., Martin D. (2013) 9th Edition. Cengage Learning Publishing.