We explain what the fungi kingdom is, what its characteristics and classification are. Also, what is its nutrition, reproduction and examples.
What is the fungi kingdom?
The fungi kingdom is one of the groups into which biology classifies known life forms. This composed of more than 144,000 different species of fungi which include yeasts, molds and mushrooms, and which share fundamental characteristics such as immobility, heterotrophic feeding and certain cellular structures.
The mushrooms exist all over the world and in different habitats and they appear in different forms and presentations.
Of all the fungi that inhabit our planet, only 5% has been studied and classified and it is estimated that there are around 1.5 million species still unknown. This is partly because fungi were previously classified as a type of plant, until in the 19th century they began to be distinguished as a separate biological kingdom.
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 fungi kingdom share the following fundamental characteristics:
- lack their own mobility. Mushrooms grow in soil, on surfaces, or on logs or decaying organic matter, depending on your preferences. Like plants, they remain in the same place all their lives, unable to move at will.
- have a cell wall. Fungal cells are eukaryotic, that is, they have a cell nucleus. In addition, they have a rigid cell wall, similar to that of plant cells, but instead of being composed of cellulose, it is composed of chitin, the same substance that gives to insects the hardness of their exoskeletons. In addition, they are elongated cells, which can contain several nuclei, and have vacuoles but not chloroplasts, since they do not carry out photosynthesis.
- grow as hyphae. The growth of fungi occurs in the form of hyphae, cylindrical and uniform 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.
- absorb food from the environment. Fungi do not ingest food and then digest it in the body like animals. 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, fungi absorb the predigested food into their body.
- reproduce through spores. Spores are microscopic reproductive cells that can develop into new organisms. They are generally produced in specialized aerial hyphae or fruiting structures. The structures where spores are produced are called sporangia. The aerial hyphae of some fungi produce spores in 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 are developed and fungi are distinguished from other life forms that resemble them. The current ranking 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 sexual 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.
- Chytridiomycete fungi (Chytridiomycota). They are microscopic and primitive fungi, generally aquatic, that reproduce by flagellated spores (zoospores).
Nutrition of the fungal kingdom
The nutrition of fungi is always heterotrophic, that is, cannot generate their own food like plants but rather they must decompose organic matter from other forms of plant or animal life. Depending on their nutrition, there are different types of mushrooms:
- Saprophytic fungi. They 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 in general.
- Mycorrhizogens. They are nourished through a symbiotic relationship with plants, colonizing their roots and exchanging with them 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.
- Lichenized. They are nourished through symbiotic relationships resulting from the union of the fungus and an algae or cyanobacteria, which establish a relationship so close that they can be considered the same individual. They are similar to mycorrhizogens.
- Parasites. They feed directly on the body of other living beings, and for that they can establish themselves on their surface or colonize the interior of their body, which causes various damages to these organisms that can be mild or even lethal.
Reproduction of the fungi kingdom
The mushrooms they reproduce sexually and asexually always through the production of spores: environmentally resistant forms that, when optimal conditions occur, germinate and create a new specimen of the fungus. The growth of the hyphae, once the spores have germinated, can be very rapid: a tropical mushroom 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 if it requires genetic variation, for which it will require exchange of genetic material with other individuals of the same species.
Asexual reproduction of fungi
Single-celled fungi, such as yeast, reproduce asexually through a process called budding: formation of buds that project from the parent cell.
In the case of multicellular fungi, asexual spores (called conidia) are produced by mitosis in specialized hyphae called conidiophores and are 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:
- The hyphae of two genetically compatible mating types are brought together, 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 through mitosis. At some point the two haploid nuclei fuse. This process, called karyogamy results 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 immediately follow. For a time the nucleus remains separated within the fungal cytoplasm.
Hyphae containing two genetically distinct but sexually compatible nuclei within each cell are described as dikaryotic. This condition is referred to as n + n instead of 2n, because there are two separate haploid nuclei.
Hyphae that only contain 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 diverse niches of appearance, because They help the decomposition and recycling of organic matter (dead animals or plants, defecation, 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 humans either 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 can be lethal 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 excreta or even decompensation of blood pressure, depending on the amount consumed.
These effects can cause necrotic damage to the liver and kidneys, which can cause death if not treated properly. In 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 mushroom (Agaricus bisporus). It is grown on farms and is part of the regular diet of many countries.
- Athlete's foot fungusTrichophyton rubrum). It is one of the 42 species of parasitic fungi that can infect human skin when it is constantly subjected to moisture.
- The 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.”
- The corn fungus (Ustilago maydis). Also called huitlacoche or cuitlacoche, it is a fungus that grows between the grains of corn, and generates edible structures that in Mexico and other countries are considered a delicacy.
Continue with: Kingdom protista
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.
