Endocrinology

What Is Fungus? What Are Fungi?

Fungi (Singular: fungus) are classified within their own kingdom - The Kingdom Fungi, while some are in The Kingdom Protista. A fungus is neither a plant nor an animal. It is similar to a plant, but it has no chlorophyll and cannot make its own food like a plant can through photosynthesis. They get their food by absorbing nutrients from their surroundings. Kingdom Fungi includes mushrooms, rusts, smuts, puffballs, truffles, morels, molds, and yeasts, and thousands of other organisms and microorganisms. They range from microscopic single-celled organisms, such as yeast, to gigantic multicellular organisms. Many fungi play a crucial role in decomposition (breaking things down) and returning nutrients to the soil. They are also used in medicine, an example is the antibiotic penicillin, as well as in industry and food preparation. Interesting articles What is ringworm? What is body ringworm? What is scalp ringworm? What is nail fungal infection? What causes nail fungal infection? What are bacteria? What is a virus? What is yeast infection or candidiasis? What is vaginal thrush? For a long time fungi were classified as plants, mainly because of their similar lifestyles - both are seen to grow in soil and are sessile (permanently attached; not moving). Plant and fungal cells both have a cell wall, while cells from the animal kingdom don"t. Fungi are thought to have diverged from the plant and animal kingdoms about one billion years ago. What is Mycology? Mycology is the study of fungi - it is a branch of biology. A mycologist studies fungi"s genes, biochemical properties, their use to us as a of food, their hallucinogenic, poisonous and pathogenic (ability to cause disease) properties. It was not until the 16th century, when the microscope was developed, that mycology became a well established science. What is the difference between a mushroom and a toadstool? Most reputable scientific reference s indicate that there is no scientific difference. People tend to refer to toadstools as the toxic (poisonous) ones and mushrooms as the edible ones. However, many mushrooms are poisonous too. A number of non-scientefic dictionaries state that a toadstool is an inedible mushroom. So, the safest answer is "There is no scientific difference, but people refer to toadstools as the inedible or toxic ones." The word toadstool is commonly used in children"s stories to indicate a poisonous or colorful mushroom. Where do fungi exist? Fungi exist in various habitats, including deep down in the ocean, lakes, rocks, deserts, very salty environments, and areas of extremely high or low temperatures. Some can prevail even after being exposed to intense UV and cosmic radiation as one would encounter during space travel. During the 13 years the Mir space station was in orbit, a great deal of equipment was continuously being damaged by mutated fungi that had been breeding in the space station. At first technicians were puzzled and thought the problems must have been due to faulty workmanship. The majority of fungi live on land. Fungi and bacteria are the main decomposers of organic matter in virtually all ecosystems on Earth. Taxonomists have classified approximately 70,000 types of fungi. Experts say there are many more - possibly 1.5 million. Fungi used to be classified according to their shape, structure, biological and biochemical characteristics. Advances in DNA sequencing have helped extend the classification of different species of fungi. Taxonomy is the classification of organisms. How do fungi feed? Although fungi are similar to plants in many ways, they do not have chlorophyll, the green pigment that enables plants to make their own food with the aid of sunlight (photosynthesis). Fungi release digestive enzymes that decompose things around them, turning them into food. The fungus then absorbs the dissolved foods through the walls of its cells. Fungi have adapted various ways of doing this: *Parasitic fungi - several species of fungi exist as parasites, feeding on live hosts, which might be animals, plants or even other fungi. Some of these parasitic fungi damage our crops, sicken farm animals, and harm or completely destroy trees. Dutch elm disease, caused by the fungus Ophiostoma ulmi destroyed hundreds of millions of elm tress worldwide. The rice blast fungus Magnaporthe oryzae can devastate rice crops. The following fungi can cause serious diseases to humans: aspergilloses, candidoses, coccidioidomycosis, cryptococcosis, histoplasmosis, mycetomas, and paracoccidioidomycosis. An example is vaginal yeast infection. *Saprobes or saprophytes - these break down dead organisms and substances that contain organic compounds and feed on them when they have rotted. Humans welcome saprobes and also fear them. They are useful decomposers of organic material, but also damage wood products and spoil our food. When ships used to be made of wood they were often rendered unusable by wood-digesting saprobes (polypores). *Symbiosis - this is when one living thing builds up a relationship with another for the mutual survival of both. Some fungi form mycorrhizae which enhance a plant-root"s capacity to absorb nutrients. The plant synthesizes nutrients the fungus needs and exchanges these nutrients for minerals the fungus absorbs from the soil - i.e. the plant and the fungus trade nutrients. Some leaf-cutting ants eat nothing but a type of fungi that lives in their nests. The fungi live on nothing but the leaves the ants carry in for them. If the ant starved the fungi and killed them the ant would have no food and would die; if the fungi found a way of poisoning the ants and killing them off, the fungi would have no food and would die. They both depend on each other for survival. The structure of fungi The majority of fungi - except for the one-celled oranisms - are composed of hyphae; threadlike tubular filaments. Hyphae is the plural of hypha. A hypha has a rigid wall around it generally made of chitin. The outer skeletons (exoskeletons) of insects are also made of chitin. The hyphae may be partitioned by dividing cross walls called septate hyphae - and are called septate hyphae, while those without cross walls are called nonseptate, or coenocytic hyphae. The cells of all species of fungi contain cytoplasm - a mixture of nutrients and fluids. The cytoplasm flows inside the hyphae and nourishes any part that requires it. The tips of a hypha grow by elongation and branch out to form an interwoven mat known as the mycelium. As the mycelium gets bigger it may produce structures (fruiting bodies) that contain spores. The fruiting bodies generally grow above the soil or other surfaces so that the spores can blow in the wind and spread. The mycelium is generally beneath the surface of whatever the fungus is decomposing. The umbrella-like structure of a mushroom is its fruiting body and is typically above the surface of whatever animal, plant or substance it is decomposing, while its mycelium is below the surface. How do fungi reproduce? Most fungi reproduce by making spores. A puffball may contain trillions of spores. *Sexual reproduction - fungi generally undergo a reproductive cycle that includes the production of sexual spores. A sexual spore contains one nucleus that has set of chromosomes; just half of the total set of the fungal-cell chromosomes - they are haploid. Human sperm and eggs are haploid; they contain 23 chromosomes each, half of the 46 that exist in human cells. Some spores contain two or more nuclei. When a spore germinates it eventually develops into a mycelium that produces fruiting bodies with sexual spores - and so the reproductive cycle starts all over again. *Asexual reproduction - asexual spores may be produced directly from the hypha in some fungi - without the need for fruiting bodies. The spores then germinate and produce additional mycelium, which spreads rapidly. Experts say this allows more rapid dispersal than sexual reproduction. *The dikaryon stage - There are two mating strains of hyphae which exist in the mycelium - the plus and the minus strain. They both look the same, but are different. Sexual reproduction occurs when the plus and minus strains fuse. Their nuclei will remain separate during the initial stages - this intermediate stage is called the dikaryon. Dikaryon means a pair of associated but unfused haploid nuclei of a fungus cell capable of participating in repeated cell division as separate entities before their eventual fusion - i.e. two nuclei, each with one half of the chromosome pairs, participating in cell division, but with nuclei not fusing yet, before the nuclei eventually fuse. With some species the dikaryon stage may last for several years, while with others it may be just a question of weeks. Eventually the two nuclei fuse and become one nucleus with the pairs of chromosomes joined up (two sets containing half the total chromosomes each), forming a diploid cell. The diploid cell then divides producing daughter cells with half the parent cell"s genetic material - this process is called meiosis. Usually four genetically unique haploid spores are produced, and the cycle restarts. This form of procreation using genetically different spores helps fungi adapt more effectively to novel diseases and environmental changes. If all the fungi were genetically identical they could all be destroyed by a single disease or a significant environmental change. *Fragmentation - in some types of fungi the hyphae fragment, with each fragment developing into a new separate organism. With the single cell of yeast, a bump forms on the cell which eventually breaks off and ultimately becomes a new yeast cell. How are fungi classified? The classification of fungi has long been a subject of controversy among experts. Pier Antonio Micheli, an Italian botanist, was the first to describe fungi in scientific terms we are used to today. He classed them as plants. For a long time the study

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