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Fungi (fungus) are eukaryotic organisms and include microorganisms such as yeasts, moulds and mushrooms. These organisms are classified under kingdom fungi and some of them are parasites. Most of these fungi are harmless recyclers but some such as, parasitic fungi, can cause significant damage to plants, animals and other fungi.
Also Read: Prokaryotic and Eukaryotic Cells
Key Terms: Fungi, Parasite, Pathogens, Kingdom Fungi, Eukaryotic, Saprophytic, Cytoplasm, Antibiotics, Prokaryotic
What are Fungi?
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Fungi are the organisms that are found in the fungi kingdom, contain a cell wall and are omnipresent. They are non-vascular, non-motile and heterotrophic organisms. Fungi lack chlorophyll and thus cannot perform photosynthesis. They reproduce by means of spores.
Fungi are classified into three groups:
- Saprophytic: obtain their nutrition by feeding on dead organic substances.
- Parasitic: obtain their nutrition by living on other living organisms.
- Symbiotic: live by having an interdependent relationship with other species in which both are mutually benefited.
Classification of Fungi
What are Parasitic Fungi?
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A parasite is an organism that obtains its nutrition from another living organism at that individual's expense. Fungi make good parasites. Unlike single-celled organisms such as bacteria, they are not confined to surfaces. Most groups of organisms, including humans, have fungal parasites. These range from ones that are barely detectable to others causing fatal diseases. These fungi cause various diseases such as ringworm, favus and many more.
In contrast with the saprophytic fungi, parasitic fungi attack living organisms, penetrate their outer defences, invade them, and obtain nourishment from living cytoplasm, thereby causing disease and sometimes death of the host.
Parasitic fungi can be classified into two sub-categories.
- Zoo-pathogenic fungi, meaning the ones that live on animals and
- Phytopathogenic fungi, meaning the ones that live on plants are called.
Plant Parasites
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Most pathogenic (disease-causing) fungi are parasites of plants and they generally enter the host through a natural opening, such as a stoma in a leaf, a lenticel in a stem, a broken plant hair or a hair socket in fruit, or a wound in the plant.
Among the most common and widespread diseases of plants caused by fungi are the various downy mildew, powdery mildew, smuts, rusts, apple scab, and various leaf spots, blights, and wilts.
Some parasitic fungi in plants are:
- Puccinia graminis
- Endothia Parasitica
- Ceratocystis Ulmi
- Puccinia Sparganioides
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Animal and Human Parasites
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Fungi affect animals, including humans, in several ways. They attack animals directly by colonizing and destroying tissues. Fungal infections are generally very difficult to treat because, unlike bacteria, fungi are eukaryotes. Antibiotics only target prokaryotic cells, whereas compounds that kill fungi also harm the eukaryotic animal host.
Many fungal infections are superficial; that is, they occur on the animal’s skin and can have devastating effects as described below.
- Mycosis is a fungal disease that results from infection and direct damage by the fungi from the genera Candida.
- Mycotoxicosis is the poisoning of humans (and other animals) by foods contaminated by fungal toxins (mycotoxins).
- Mycetismus describes the ingestion of preformed toxins in poisonous mushrooms.
- Fungi from the genera Sporotrichum and Blastomyces attack the cell tissues and internal organs of humans and animals.
Also Read:
| Chapter Related Topics | ||
|---|---|---|
| Multicellular Organisms | Unicellular Organisms | Algae |
| Phycology | Harmful Microorganisms | Microbiology |
Previous Years’ Questions
- Identify the odd one out... [KCET 2021]
- A hyphae which is multinucleated and asptate is known as… [WBJEE 1999]
- Puccinia forms uredia and… [NEET 1998]
- The imperfect fungi which are decomposers of litter and help in mineral… [NEET 2015]
- Match the storage products listed under Column-I with… [KCET 2014]
- Edible fungus is… [UPSEEE 2016]
- Mycology is related with… [BCECE 2004]
- Black rust of wheat is a fungal disease caused by… [JIPMER 2004]
- Cell wall of fungi is composed of… [JIPMER 2018]
- Clamp connections are observed in… [JIPMER 2009]
Things to Remember
- Fungi (fungus) are eukaryotic organisms and include microorganisms such as yeasts, and moulds and are classified under kingdom fungi.
- A parasite is an organism that obtains its nutrition from another living organism at that individual's expense.
- Parasitic fungi can be classified into two sub-categories: zoo-pathogenic fungi and phytopathogenic fungi.
- Among the most common and widespread diseases of plants caused by fungi are the various downy mildew, smuts, and rusts.
- Fungi attack animals directly by colonizing and destroying tissues.
Sample Questions
Ques: What are parasitic fungi? [2 marks]
Ans: Parasitic Fungi are fungi that can invade a living host and obtain nourishment, often causing damage to the function and structure of the host.
Ques: What are the two types of parasitic fungi? [2 marks]
Ans: The two types of parasitic fungi are: zoo-pathogenic fungi and phytopathogenic fungi.
The zoo-pathogenic fungi are the ones that live on animals while the phytopathogenic fungi live on plants.
Ques: How are saprotrophic and parasitic fungi different from each other? [3 marks]
Ans: Saprophytic fungi are responsible for breaking down and recycling dead plant and animal material. In contrast, parasitic fungi attack living organisms, penetrate their outer defences, invade them, and obtain nourishment from living cytoplasm, thereby causing disease and sometimes death of the host.
Ques: Name some parasitic fungi that attack plants. [2 marks]
Ans: Some parasitic fungi that attack plants are: puccinia graminis, endothia parasitica, ceratocystis ulmi, and puccinia sparganioides.
Ques: What are eukaryotic organisms? [2 marks]
Ans: Eukaryotic organisms possess a well-defined nucleus. Eukaryotic cells also contain organelles, including mitochondria, a Golgi apparatus (secretory device), an endoplasmic reticulum, and lysosomes.
Ques: Define mycotoxicosis. [2 marks]
Ans: Mycotoxicosis is the poisoning of humans (and other animals) by foods contaminated by fungal toxins (mycotoxins). Ozone can kill most mycotoxins, but the level needed is not safe for humans.
Ques: Are fungi heterotrophs or autotrophs? [2 marks]
Ans: Fungi are not obligate intracellular parasites. They do not contain chlorophyll and cannot synthesize macromolecules from carbon dioxide and energy derived from light rays. Therefore all fungi are heterotrophs, living on preformed organic matter.
Ques: Give some characteristics of fungi. [4 marks]
Ans: Characteristics of fungi are as follows:
- They are eukaryotic.
- Do not contain chlorophyll.
- They are absorptive heterotrophs – digest food first and then absorb it into their bodies.
- Release digestive enzymes to break down organic material or their host.
- They store food energy as glycogen.
- Most are saprobes – live on other dead organisms.
Ques: How are fungi classified? [3 marks]
Ans: Fungi are classified by their reproductive structures. The 4 phyla of fungi are Basidiomycota, Zygomycota, Ascomycota, and Deuteromycota.
Ques: List some uses of Fungi. [4 marks]
Ans: A few uses of fungi are given below:
- Fungal spores cause allergies
- Molds, mildew, rust, and smuts damage crops
- Yeasts are used to make beer and bread.
- They are used in the production of the antibiotic penicillin.
- Decomposers and recyclers of nutrients.
- Mushrooms are eaten as food.
- Aspergillus, a fungus, is used to make soy sauce.
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