Lichens - class-IX

Lichen is a symbiotic association of fungi ( Ascomycota or basidiomycete) with an alga (Chlorophyceae or Cyanophyceae). The term Lichen was coined by Theophrastus (370-285 BC).

Lichens are a symbiotic partnership of fungus and algae. The dominant partner is the fungus, which gives the lichen the majority of its characteristics from its thallus shape to its fruiting bodies. So, thallus is foliose in lichens. Lichens occur in one of four basic growth forms. crustose, squamulose, foliose and fruticose. So, the correct answer is 'Lichens'.

The fungal part of the lichens is known as mycobiont. Cyanobacteria have a special structure known as heterocyst which is specialised to perform nitrogen fixation. It has specific enzymes like nitrogenase which actively fixes the atmospheric nitrogen to a usable form. They are autotrophic so they also fix carbon during the dark reaction of photosynthesis into organic compounds. This conversion process of inorganic carbon (carbon dioxide) to organic compounds is also known as carbon assimilation.

• The algal component carries out photosynthesis and produces carbohydrate glucose during the dark reaction of photosynthesis.
• Minerals are provided to the algal part by fungal mycelium. It absorbs water and minerals from the substratum.
• Lipids and proteins are neither supplied by algal part nor fungal part but synthesized within the organism itself.
• So the correct answer is 'Carbohydrate'.

Lichens are found in odd places which includes areas in the Arctic and Antarctic, and mountain tops. Lichens are found on soil, rock or tree bark. Some will also grow on old wood (dead branches, fence rails, etc.), masonry and cemetery headstones. Lichens are often found in extreme environments where other organisms are sparse.

• Rhizobium is a genus of bacteria associated with the formation of root nodules on plants. These bacteria live in symbiosis with legumes. They take in nitrogen from the atmosphere and pass it on to the plant, allowing it to grow in soil low in nitrogen.
  
• A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi in a symbiotic relationship. 
  
• Mycorrhizal fungi colonize the plant's root system and develop a symbiotic association called “mycorrhiza” They form a network of fine filaments that associate with plant roots and draw nutrients and water from the soil that the root system would not be able to access otherwise.
  
• Lichens, Rhizobium and Mycorrhizae  have symbiotic relationships and follow same mode of nutrition.
• So the correct answer is " All the above".

Lichens are the symbiotic associations i.e; mutually useful associations between algae and fungi. The algal component is known as phycobiont and the fungal component is known as mycobiont. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner.  option C is the answer

• A lichen is a composite organism that emerges from algae living among the filaments (hyphae) of the fungi in a mutually beneficial symbiotic relationship.
• Fungi are Achlorophyllous organisms because they do not perform photosynthesis due to the absence of chlorophyll.
• Hence Lichens are composites consisting of algae and achlorophyllous organisms(fungi).
• So, the correct answer is 'Achlorophyllous organisms'.

• Mycorrhiza is the product formed by the symbiotic association between fungus and roots of higher plants, in which fungi protects the plant from pathogens and increases the surface area by which plants can absorb soil nutrients and water whereas plants provide the shelter and carbohydrates to fungi in which both get benefited.

Lichen can grow on barren rock and are the first living organisms or "pioneers" to colonize places, where no other living things can survive.

Foliose lichen is the most complex lichen. It is a lichen with leafy body parts or thallus and which generally have a cortex on each side of the leafy lichen body part thallus. Crustose lichens are lichens that grow like a crust of paint on their substrate, and especially sqamulose crustose lichens, may not be attached to the substrate at the edges, giving a leafy appearance similar to foliose lichens, but there is no lower cortex on the leafy part. Fruticose lichens are lichens that have a form similar to a tiny leafless, branching shrub that may have the branches flattened, so as to appear leafy, but foliose lichens have a single cortex wrapping around the branches, whereas foliose lichens generally have an upper and a lower cortex. Gelatinous lichens may appear leafy, but lack a cortex or internal structure, having the photobiotic component diffuse throughout the no fruiting part of the lichen body, whereas in foliose lichens the algae are in a layer. In foliose lichens, the layer of tissue containing the photosynthetic component has the algae more diffuse in the fungus than in foliose lichens, where the algal layer is generally very distinct.

In lichens, a relationship occurs in which the fungus lives as a dominant organism and algae like a slave, the relationship is known as helotism. It is a form of symbiosis in which one species is forced to perform tasks for another, for their mutual benefit. Thus, the correct answer is option B. 

Most lichen fungi belong to Ascomycetes. The lichen fungi cultivate partners, that manufacture food by photosynthesis. Sometimes, the partners are algae (kingdom Protista), other times cyanobacteria (kingdom Monera), formerly called as blue-green algae.

The photobiont supplies the association organic carbon from photosynthesis, and the mycobiont ensures protection and regulates the supply of minerals and water. The nutritional exchange between partners is probably much more complex than exchange of water and minerals for organic carbon.

Lichens and mosses are used as the indicators of air pollution. These structures grow on damp areas. Air pollutants which are in the gaseous forms get dissolved in the rainwater, especially SO$ _2$ can damage these plants, and check them from growing. In places where these vegetation are not growing, it indicates that the air is heavily polluted with sulphur dioxide and other pollutants. 

A lichen is a composite organism that arises from algae or cyanobacteria (or both) living among filaments of a fungus in a symbiotic relationship. The combined life form has properties that are very different from the properties of its component organisms. The fungus benefits from the symbiotic relation because algae or cyanobacteria produce food by photosynthesis. The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungus, which also gather moisture and nutrients from the environment, and (usually) provide an anchor to it. Thus, the correct answer is option C.

Certaria is a kind of lichen which lives in close association with green algae. It is a very good source of laxative which makes bowel movement easy and loosen the stools. Most of these species are found at high latitudes, occurring on sand and shrub lands.

Lichens are used as the indicators of air pollution. These structures grow on tree bark and rocks. Air pollutants which are in the gaseous forms get dissolved in the rainwater, especially SO$ _2$ (sulfur dioxide) can damage lichens, and check them from growing. In places where lichens are not growing, it indicates that the air is heavily polluted with sulfur dioxide and other pollutants. In cities, SO$ _2$ is one of the most common air pollutants as it releases from the vehicles.

Lichens are used as the indicators of air pollution. These structures grow on tree bark and rocks. Air pollutants which are in the gaseous forms get dissolved in the rainwater, especially SO$ _2$ (sulphur dioxide) can damage lichens, and check them from growing. In places where lichens do not grow, it indicates that the air is heavily polluted with sulphur dioxide and other pollutants. 

Foliose lichen is a lichen thallus growth form that has a 2-dimensional, flat, leaf-like lobes and lifts up from the surface. Parmelia is a medium to large foliose lichen with ends of the leaf-like lobes often squarish-tipped.

Lichens are the symbiotic association between the fungi and algae. They obtain almost all their nutrients from the atmosphere through uptake over their entire surface and thus called as epiphytic lichens. They have no cuticle, nor means of controlling nutrient uptake, unlike vascular plants, and free exchange of both gasses and solutions occurs across cell surfaces. Lichens are therefore highly susceptible to changes in atmospheric composition and for this reason provide very sensitive indicators of such changes. Lichens are sensitive to sulphur, nitrogen, acidity, halogens (e.g., fluoride), heavy metals and ozone.

Lichens are used as the indicators of air pollution. These structures grow on tree bark and rocks. Air pollutants which are in the gaseous forms get dissolved in the rainwater, especially pollutants like SO$ _2$ can damage lichens, and check them from growing. In places where lichens are not growing, it indicates that the air is heavily polluted with sulphur dioxide and other pollutants. 

In a highly industrialized area, lichens will be virtually absent as these area will be highly polluted and lichens are useful bioindicators for air and water pollution specially for sulphur dioxide pollution. Their efficient absorption systems results in rapid accumulation of sulphur when exposed to high levels of sulphur dioxide pollution and the algal partner are most affected by the sulphur dioxide as chlorophyll is destroyed and photosynthesis is inhibited.

Lichens have a symbiotic relationship. In this type of relationship, lichens live symbiotically. there is a symbiotic relationship between algae and fungi in lichens. Algae perform photosynthesis and provide with carbon compounds. Fungi provide protection and nutrition to algae. Thus, 2 organisms are involved in a lichen. 

Algae are green photosynthetic organisms. They are autotropic as they perform the process of photosynthesis to prepare their own food. Lichens cannot prepare their own as they are non-photosynthetic. So, inn absence of lichens , algae can survive as they can prepare their own food. But lichens will starve and ultimately die. 

• The weathering of rocks is responsible for the formation of soil. It occurs due to a variety of reasons like under the effect of lichens. 
• Lichens cause the breakdown of rock materials and organic minerals. Thus they breakdown the surface of rocks.
• Mosses also release different gases and cause the breakdown of rocks they grow on.
• Roots of plants that grow on rocks cause cracks on the surface of rocks.
• Thus, all these factors are responsible for the weathering of rocks.

The species of the lichen Rocella is used for the extraction of the dye which serves in the formation of litmus. The litmus papers are used for testing of the pH. The litmus paper turns blue at alkaline pH and red at acidic pH. The change in the pH can be analysed using the litmus papers. 

Reindeer moss is a type of lichen. It grows in arctic regions and is a bluish-grey organism. In winters, it provides food for reindeer. Apple moss, peat moss and club moss are typical mosses. 

Cyphella are aerating organs in the form of organised breaks, which occur in the lower cortex and appear as concave circular depression where white medulla is exposed.

The correct answer is 'lichens'

The photobiont supplies the association of organic carbon from photosynthesis, and the mycobiont ensures protection, and regulates the supply of minerals and water. The nutritional exchange between partners is probably much more complex than exchange of water and minerals for organic carbon.

The teacher was explaining the advent of lichen formation. A lichen is made up of a simple photosynthesising organism, usually green algae or cyanobacteria, surrounded by filaments of a fungus. Generally, most of lichens bulk is made of interwoven fungal filaments, although in filamentous and gelatinous lichens this is not the case. The fungus is called as a mycobiont. The photosynthesizing organism is called as a photobiont. Algal photobionts are called as phycobionts. Cyanobacteria photobionts are called as cyanobionts. The part of a lichen that is not involved in reproduction, the "body" or vegetative tissue" of a lichen, is called as the thallus. The thallus form is very different from any form, where the fungus or alga are growing separately. The thallus is made up of filaments of the fungus called as hyphae. The filaments grow by branching then rejoining to create a mesh, which is called being. The mesh of fungal filaments may be dense or loose.

Lichen is a stable symbiotic association between a fungus and algae. The combined life form has properties that are very different from the properties of its component organisms. Lichens come in many colors, sizes, and forms. The properties are sometimes plant-like, but lichens are not plants. 

Lichens usually reach maturity and produce ascocarps at 4-8 years of age. The age of some lichens in alpine-arctic area is 1000-4500 years. Their longevity can be partially attributed to their ability to survive long periods of drought unharmed.

The lichen fungi (kingdom Fungi-ascomycetes) cultivate partners that manufacture food by photosynthesis. Sometimes, the partners are algae (kingdom Protista), other times cyanobacteria (kingdom Monera), formerly called as blue-green algae.

Lichen's can photosynthesis at a very low temperature.
i.e.,−20C−240C

In hot season, Usnea get dry and become highly inflammable. It easily catches fire and causes forest fire.

In biology that lives in dead wood, leaves, or sticks, or organic debris is called as lignicolous. Lichens which grow on wood are called lignicolous, e.g., Cephalium.

Graphis scripta is a crustose lichen in Graphidaceae family.

In lichens, a relationship occurs in which the fungus lives as a dominant organism and algae like a slave, the relationship is known as helotism. It is a form of symbiosis in which one species is forced to perform tasks for another, for their mutual benefit. 

A lichen is a composite organism that arises from algae or cyanobacteria (or both) living among filaments of a fungus in a symbiotic relationship. The combined life form has properties that are very different from the properties of its component organisms. The fungus benefits from the symbiotic relation because algae or cyanobacteria produce food by photosynthesis. The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungus, which also gather moisture and nutrients from the environment, and (usually) provide an anchor to it. 

Lichens are known for their extremely slow growth rates, often growing only a few millimeters per year, not 2 cm per day.

Lichens reproduce vegetatively by soredia formation. It is the most common form of reproduction where small protuberances are formed on the thallus. They may have a definite pustule or appear as greyish dust. Many lichens reproduce asexually, either by vegetative reproduction or through dispersal of diaspores, which contain a few algal cells surrounded by fungal cells. 

Lichens are symbiotic organisms consisting of a fungal partner (mycobiont) and an algal or cyanobacterial partner (phycobiont). In the vast majority of lichens, the fungal partner is an ascomycete, and the photosynthetic partner is either green algae or blue-green algae (cyanobacteria).

Lichens exhibit the symbiotic association between algae and fungi. In this plant, algae is the photosynthetic partner involved in food preparation and the fungal partner increases the surface area for the absorption of water and minerals. Also, the fungal partner is involved in sexual reproduction with the help of reproductive structures called apothecia. 

Lichens with a branched system but small base are Fruticose.

Reindeer moss is lichen that is a fruticose lichen found in great abundance in Arctic lands. It is an erect, many branched plant that grows up to 8 cm hight covers immense areas and serves as pasture for reindeer, moose, caribou, and musk oxen.

Letharia vulpina, commonly known as the wolf lichen, is considered toxic or harmful because it contains vulpinic acid, which was historically used to poison wolves and foxes.

Cyphellae are small, cup-like depressions on the lower surface of certain lichens that facilitate gas exchange, serving a function analogous to stomata in plants.

Symbiosis in lichen is the mutually helpful symbiotic relationship of green algae living among the filaments of a fungus, forming a lichen. Example, Usnea

The majority of lichens are formed by the association of an ascomycete fungus and a photosynthetic partner, which is frequently a green alga or a blue-green alga (cyanobacterium).

A lichen is a long living composite organism that arises from green algae or cyanobacteria  living among filaments of a fungus in a mutually beneficial relationship (symbiotic relationship). The algal component of a lichen is known as phycobiont and the fungal component is called mycobiont.

In lichens, rhizines are multicellular root-like structures, arising mostly from the lower surface.Rhizines serve only to anchor the lichen to their substrate; they do not absorb nutrients as do plant roots.

• In biology that lives in dead wood, leaves, or sticks, or organic debris is called as lignicolous. 
• Lichens which grow on wood are called lignicolous, e.g., Cephalium.
• Hence the correct answer is option B. 

The term helotism refers to a master-slave relationship in symbiosis, where the fungus is often considered to dominate or 'enslave' the algal partner, a concept frequently applied to the lichen association.

Lichens are composite organisms containing algae and fungus. They live in symbiotic association. In this, algae provides food and nutrition obtained by photosynthesis. In turn, fungus provides protection, anchorage and absorption of water and nutrition from soil for algae.

• Lichens are widely used as environmental indicators or bio-indicators. If the air is clean, shrubby, hairy and leafy, the lichens become abundant. 
• Only a few lichen species can tolerate quite high levels of pollution.

Lichens are classified by their substrate: saxicolous lichens grow on rocks, corticolous on bark, lignicolous on wood, and terricolous on soil.

Lichen is a symbiotic association between blue-green algae and fungus. In this, blue-green algae provide food and nutrition obtained by photosynthesis. In turn, fungus provides protection, anchorage and absorption of water and nutrition from soil for algae.

The majority of lichen photobionts belong to the green algal class Chlorophyceae, with the most common genera being Trebouxia.

A lichen is a composite organism consisting of a fungus (the mycobiont) and a photosynthetic partner (the photobiont) growing together in a symbiotic relationship. 

Ochrolechia (such as O. tartarea) has historically been used in the production of dyes and in cosmetic or perfumery applications due to its chemical properties.

Lichens can reproduce, do not need nitrogen source to live and is a symbiotic relationship between fungi and cyanobacteria. They are able to live in extreme conditions like on a bare rock. 

The process of community development over time, which involves species in one stage being replaced by other species, is called ecological succession. It is divided as primary succession and secondary succession. An area is initially colonized by certain early-successional species such as Lichens, they are often the first organism to colonize an area that will undergo primary succession. Once new soil has formed in an area it gives way over time to mild-successional species, such as mosses and grasses, which in turn give way much later to late-successional species.

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.

Lichens represent mutualism, not commensalism (i is incorrect). They are pioneer species in xerosere (rock succession), not hydrosere (vi is incorrect).

Mutualism is a positive interaction in which both partners are benefited. Lichens are the mutualistic association of fungi and cyanobacteria in which both are benefited. 

In lithosere (xerosere or xerarch), the pioneer community is usually constituted by crustose lichens(e.g., Graphis, Rhizocarpon). Foliose lichens(e.g., Dermatocarpon, Parmelia) kill the crustose lichens by shading them, cause deeper depressions and accumulate more soil particles and organic matter. Foliose lichens make the conditions favourable for the growth of hardy mosses(e.g., Tortula, Grimmia).

Lichen forms a crust over bare rocks and starts forming soil from their organic remains by secreting carbonic acid which results in the chemical breakdown of rocks. 

Litmus is a natural dye with a water-soluble mixture extracted from lichens, it is used as a pH indicator.

Lichens are association (mutually beneficial) between fungus and alga.
The fungal partner is mycobiont and algal partner is phycobion. The
mycobiont is usually an ascomycete and phycobiont is usually green algae
Lichens can grow in extremely inhospitable conditions In many
ecosystems they are the pioneer species. The role of mycobiont is
providing body structure and anchorage and absorption of minerals and
water. The role of phycobiont is mainly in providing food through
photosynthesis. So, the correct answer is 'Fungus and algae'.

Symbiosis in lichens is the mutually helpful symbiotic relationship of green algae and/or blue-green algae (cyanobacteria) living among filaments of a fungus. The fungus benefits from the algae or cyanobacteria, because they produce food by photosynthesis. The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungus, which also gather moisture and nutrients from the environment, and provide an anchor to it.

Lichen is a symbiotic partnership between fungus and alga. It has algal and fungal partners in its thallus. In this, the fungus is a dominant partner. Hence, lichen has majority of characteristics of fungus. It absorbs sulphur dioxide from the atmosphere. Hence, it is widely used as indicator of air pollution. It grows very slowly.  It is eaten by snails, squirrels and some species of monkeys and reindeers during winter. They grow at 1 mm per day.

 According to Crombic, the relation between an algae and a fungi is helotism. Which is a kind of master-slave relationship, where the algal partner acts as a slave to the fungal partner, because, algae is an autotroph  however, the fungal partner may hinder the reproduction and nutrition of the algae.

Lichens are the symbiotic association of algae and fungi. Lichens are autotrophic, they can make their own food with the help of sunlight and provide food to the fungi and in return fungi provide protection to the lichen. Lichens always reproduce asexually. It is the most controversial organism, it possesses the characters of algae and fungi both. It is placed in ascomycetes.

Fruticose lichen ususally round in cross secetion (terete), and most are branched. They can be like little shrubs growing upward, or they can hang down in long strands. The fruticose lichens have much branched cylindrical, ribbon-like, flattened or sometimes filamentous thalli. 

• A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.
  
• If air is very badly polluted with sulfur dioxide($SO _2$) there may be no lichens present, just green algae may be found. If the air is clean, shrubby, hairy and leafy lichens become abundant
  
• Hence Lichens are important in the studies on atmospheric pollution because they are very sensitive to pollutants like sulfur dioxide. 
• So, the correct answer is ' Are very sensitive to pollutants like $SO _2$.

Lichens are a small group of curious plants, they are curious because they are the composite or dual organism. They are the association between fungi and green algae or blue-green bacteria.

Mosses are flowerless plants that grows as dense green tufts or mats in damp and shady locations. Lichens on the other hand though, they appear similar to mosses, are not related to these are are a composite organism of algae, cyanobacteria and living in a symbiotic relationship in a fungus. The medulla which is found below the cortex in lichens and is made up of loosely woven layer of fungal filaments. Hadrome refers  to collection of hydroids or vascular tissue that occur in some bryophytes or mosses and help in transporting water and minerals drawn from the soil.

• Slime moulds are Saprophytic Protists.
• They move along decaying twigs and leaves engulfing organic material. 
• Under a suitable condition, they form aggregation called Plasmodium.
• During unfavourable condition, the plasmodium differentiates and form fruiting bodies bearing spores at their tips.
• The spores possess true walls.
• They are extremely resistant and survive for many years even under adverse conditions. 
• The spores are dispersed by air currents.
• So, the correct answer is 'Air currents'.

Lichens are formed by the physical association between fungal partner and the algal partner. The fungal partner acts as a mycobiont and algal partner acts as a phycobiont. In lichens, fungus grow around algae and provide bulk for their growth. The algae and fungus association is must for lichens to reproduce. So, they are physically dependent on each other. Here, both fungus and algae are in their thalloid forms.

a) The phycobiont part of lichen is the autotrophic part which constitutes algae. The function of autotrophic algae is to provide nutrition. It synthesizes organic food by the process of photosynthesis.
b) If the algal component is blue-green algae, then apart from photosynthesis phycobionts also carry out nitrogen fixation. Nostoc, blue-green algae consist of heterocysts that have the enzyme nitrogenase. Nitrogenase converts atmospheric nitrogen into a usable form of nitrogen.

• The components of lichen include fungi and algae.
• Algae may be cyanobacteria or green algae.
• Cyanobacteria belong to the kingdom monera as they are prokaryotic organisms.
• Green algae belong to Thallophyta of kingdom Plantae.
• Fungi belong to kingdom fungi.
• So the correct answer is " Any of the above".

Lichens are used as the indicators of air pollution. These structures grow on tree bark and rocks. Air pollutants which are in the gaseous forms get dissolved in the rainwater, especially SO$ _2$ (sulphur dioxide) can damage lichens, and check them from growing. In places where lichens are not growing, it indicates that the air is heavily polluted with sulphur dioxide and other pollutants. 

Reindeer moss is a common name for the lichen Cladonia rangiferina.

• The function of fungal part of a lichen is the absorption of water and minerals from the substratum and providing protection for the phycobiont.
• Food production is done by phycobiont.
• So, the correct answer is 'Absorption of minerals and Protection'.

• Mosses are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations.
  
• Lichens are multicellular, eukaryotic but they have symbiosis as their mode of nutrition where algal component provides nutrition and fungal component helps in mineral absorption and protection.
• Lichens contain unicellular cyanobacteria if the algal component contains cyanobacteria but all cells are not unicellular as fungal myceliae are multicellular.
• So the correct answer is 'A composite organism made up of a fungus, that grows symbiotically with an algae or a cyanobacterium.'

Algae are photosynthetic organisms, while fungi are saprophytic organisms.

Lichens are not a single organism, but, rather, an example of a mutualism in which a fungus usually a member of the Ascomycota or Basidiomycota phyla lives in close contact with a photosynthetic organism