ISC 11>DIVERSITY OF LIFE>KINGDOM FUNGI
- Kingdom Fungi: General characters of each zygomycetes, ascomycetes, basidomycetes and deuteromycetes - Three characteristics with two examples.
- Economic importance of fungi.
- Definition and explanation of lichens and mycorrhiza.
- All are eukaryotic: Possess membrane-bound nuclei (containing chromosomes) and a range of membrane-bound cytoplasmic organelles (e.g. mitochondria, vacuoles, endoplasmic reticulum).
- FORM: Most are filamentousComposed of individual microscopic filaments called hyphae, which exhibit apical growth and which branch to form a network of hyphae called a mycelium.
- Some are unicellular e.g. yeasts.
- Protoplasm of a hypha or cell is surrounded by a rigid wall Composed primarily of chitin and glucans, although the walls of some species contain cellulose.
- Many reproduce both sexually and asexually: Both sexual and asexual reproduction often result in the production of spores.
- Their nuclei are typically haploid and hyphal compartments are often multinucleate
- Although the Oomycota and some yeasts possess diploid nuclei.
- All are achlorophyllous: They lack chlorophyll pigments and are incapable of photosynthesis.
- All are chemoheterotrophic (chemo-organotrophic)They utilise pre-existing organic sources of carbon in their environment and the energy from chemical reactions to sythesise the organic compounds they require for growth and energy.
- Possess characteristic range of storage compoundse.g. trehalose, glycogen, sugar alcohols and lipids.
- May be free-living or may form intimate relationships with other organismsi.e. may be free-living, parasitic or mutualistic (symbiotic).
- They are cosmopolitan in distribution and can occur in any habitat where life is possible.
- Some fungi occur in fresh water or marine water, other are terrestrial and still others are air borne.
- Many species are parasitic, infecting plants, animal and human beings.
- Some may form intimate relationships with other organism.(symbiotic)
FUNGI: GROWTH FORMS
- Many of us are familiar with the appearance of mushrooms and toadstools. But these structures are simply the large, macroscopic fruiting bodies produced by some groups of fungi.
- The main fungal body consists of branched and filamentous hyphae, which form a net-like structure, known as mycelium.
1. Unicellular : Yeasts
2. Mycelial: filamentous
- Mycelial fungi can be septate or aseptate.
- The hyphae are aseptate and coenocytic : Phycomycetes
- Septate and uni or bi or multinucleate (as in ascomycetes, basidiomycetes & deuteromycetes)
- Electron microscopy has revealed that several different types of septa exist among the major taxonomic groups of fungi.
- TYPES OF SEPTA : (DETAILS OF SEPTA)
- The higher fungi (Ascomycetes, Basidiomycetes and deuteromycetes) are non-motile, i.e. motile cells do not occur in their life-cycle at any stage .
- In lower fungi (Phycomycetes) the reproductive cells and asexual zoospores are uni or bi flagellate.
- The flagella are of two types :
- Whiplash (acronematic) flagella are smooth on their surface
- Tinsel (pantonematic) flagella are with numerous minute hair- like mastigonemes on their surface.
MODIFICATION OF HYPHAL STRUCTURE
- In majority of fungi the hyphae form a felt like structure, but in some advanced fungi they may undergo certain modification in response to functional needs.
- The hyphal structure can be modified into following forms:
- Prosenchyma: When the component hyphae lie more or less parallel to one another, they unite to form a rather loosely interwoven structure where individuality of hyphae is not lost.
- Pseudo-parenchyma : When the hyphae are completely fused to each other and lose their individuality the mass is called pesudo-parencyma.
- Sclerotium : The interwoven hyphae becomes so much compact that the mass becomes rounded and cushion like.
- Rhizomorph : In this the hyphae of the mass fuse to each other and forming rope like structure
running parallel to each other.
- Haustoria : They are intracellular absorbing structure of obligate parasitic fungi, meant for absorbing food materials from the host.They secrete specific enzymes to penetrate in host cell.
- Parasitic fungi:
- Fungi that take their food from host plants and die with the death of host are called obligate parasites.
- Some parasitic fungi after the death of host plant are able to absorb food from their decaying body and are called facultative saprophytes
- Fungi parasitic on plants have specialised hyphae called haustoria, - which penetrate host cells and absorb nutrients present there. Haustoria may be knob-like or branched.
- It is normally saprophytic or lives freely but can become parasitic on certain occasions.
- Fungi which take their food from decaying organic matter only are called obligate saprophytes.
- An organism, usually parasitic, that occasionally may live and grow as a saprophyte.
- Mycorrhiza: Some fungi occur in a long-lasting beneficial association with roots of higher plants. This association is termed as mycorrhiza.
- Lichen : A symbiotic association between green or blue-green algal cells and fungal hyphae.
VIDEO: MODE OF NUTRITION
- In most of the fungi only a part of the vegetative mycelium form reproductive unit and the rest remains vegetative. Such fungi are known as eucarpic.
- However, in unicellular fungi whole vegetative cell transformed into a reproductive unit, such as they are known as holocarpic.
- They reproduce by vegetative, asexual and sexual stage.
A. VEGETATIVE REPRODUCTION
B. ASEXUAL REPRODUCTION
C. SEXUAL REPRODUCTION
CLASSIFICATION (Details in PPT)
- Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont, which are autotrophic and heterotrophic, respectively.
- Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. So close is their association that if one saw a lichen in nature one would never imagine that they had two different organisms within them.
- Lichens are found growing in all sorts of habitats.
- They grow on on bare rocks, barks of trees, dead wood, leaves, branches or on open ground.
- They are adapted to survive under great extreme of heat, cold and drought.
- In India, lichens are found all over Himalayas and higher hills of the peninsula.
TYPES OF LICHEN (Based on morphology)
- Lichen may be bluish-green, greyish green, yellow, orange, reddish, brownish or black coloured.
- Based on their external form, they are of the following types.
- Crustose : These are found as incrustations on rocks and barks. They remain closely attached to the substratum in the form of crust and cannot be isolated easily. Eg. Rhizocarpon, Graphis
- Foliose : These are flat and leaf -like with lobed margins. Attached to the substratum with the help of rhizoids. Eg. Parmelia, Peltigera
- Fruiticose : These are branched, ribbon like filamentous and shrub like, attached to the substratum by their basal end. Eg. Usnea
Rhizocarpon Parmelia Usnea
ANATOMY OF LICHEN THALLUS
- The major part of lichen body is composed of closely interwoven hyphae of the fungus in association with the algal component.
- A transverse section of foliose lichen shows four distinct zones:
- Upper cortex
- Algal layer
- Lower cortex
REPRODUCTION IN LICHEN
Lichens reproduce by two methods:
- Asexual reproduction
- Sexual reproduction
2. Sexual reproduction
LICHEN: ECONOMIC IMPORTANCE
- Ecological values
- Food and fodder
- Dyes and minerals
- Organic acid
- Indicators of air pollution
KINGDOM FUNGI: SUMMARY VIDEO