Algae (General) Questions in English

(C) Algae contain photosynthetic pigments such as chlorophyll,which allow them to synthesize their own food using sunlight,water,and carbon dioxide. This mode of nutrition,where an organism produces its own food through photosynthesis,is known as $holophytic$ or autotrophic nutrition.

(B) $Mastigocladus$ $laminosus$ is a thermophilic cyanobacterium.
It is characterized by having a true branched filament structure,which is a unique feature among many cyanobacteria that typically exhibit unbranched filaments.

(C) Chlorophyll $b$ is an accessory pigment found in green algae (Chlorophyceae) and higher plants.
Blue-green algae (Cyanobacteria) are prokaryotic organisms that contain chlorophyll $a$ but lack chlorophyll $b$.
Red algae (Rhodophyceae) contain chlorophyll $a$ and $d$,while brown algae (Phaeophyceae) contain chlorophyll $a$ and $c$.
Therefore,blue-green algae show the absence of chlorophyll $b$.

(A) $Nostoc$ is a genus of cyanobacteria (blue-green algae) that forms colonies.
These colonies are embedded in a mucilaginous or gelatinous sheath,which protects the filaments from desiccation and environmental stress.
This gelatinous matrix is a characteristic feature of many colonial cyanobacteria.

(C) $Anabaena$ is a cyanobacterium (often referred to as blue-green algae) that forms a symbiotic relationship with the water fern $Azolla$.
Within the cavities of $Azolla$ leaves,$Anabaena$ fixes atmospheric nitrogen $(N_2)$ into ammonia,which is then utilized by the plant for growth.
Therefore,$Anabaena$ is the correct answer as it is both symbiotic and nitrogen-fixing.

(C) During the rainy season,the high moisture content and favorable temperatures promote the rapid growth of green algae (such as $Chara$ or $Spirogyra$) on damp surfaces like ground,rocks,and walls. These organisms form a slimy,mucilaginous layer that makes the surface slippery. While cyanobacteria can also grow in such conditions,the primary cause of the characteristic slippery green layer on the ground is the dense growth of green algae.

(C) Hormogonia are short,motile or non-motile segments of filaments that break off from the parent filament to form new colonies.
These structures are characteristic of certain filamentous cyanobacteria (blue-green algae).
Among the given options,$Oscillatoria$ is a filamentous cyanobacterium that reproduces vegetatively through the formation of hormogonia.
$Ulothrix$,$Spirogyra$,and $Chlamydomonas$ are green algae and do not produce hormogonia.

(A) $Gelidium$ is a red alga $(Rhodophyceae)$ that is the primary source of agar-agar.
Agar-agar is a gelatinous substance used extensively in laboratories as a culture medium for growing microorganisms.
Due to its porous structure and ability to solidify,it is also used in the preparation of bacteriological filters to trap bacteria.

(C) . Red rust of tea is not a fungal disease; it is caused by the green alga $Cephaleuros$ $virescens$.

$(A)$ Prof. $M.O.P. Iyengar$ of Madras is regarded as the father of Indian phycology.
He made significant contributions to the study of algae and discovered $Fritschiella$, which is a heterotrichous terrestrial alga.

(A) The study of algae is known as algalogy or phycology $(Gr. phykos = \text{algae})$.
An expert in this field is referred to as a phycologist or algalogist.
Therefore, the correct option is $A$.

(A) $F.E. Fritsch$ $(1935)$ is widely recognized as the "Father of Phycology" due to his monumental work, "Structure and Reproduction of the Algae".
In this book, he classified algae into $11$ distinct classes.
His classification system was primarily based on pigmentation, reserve food materials, flagellation, thallus structure, modes of reproduction, and life cycles.
Therefore, the correct answer is $A$.

(D) The classification of algae into three main classes,namely $Chlorophyceae$,$Phaeophyceae$,and $Rhodophyceae$,is primarily based on the following criteria:
$1$. The type of photosynthetic pigments present (e.g.,chlorophyll $a$,$b$,$c$,$d$,$fucoxanthin$,$phycoerythrin$).
$2$. The nature of the stored food material (e.g.,starch,$mannitol$,$laminarin$,$floridean$ starch).
$3$. The composition of the cell wall (e.g.,cellulose,$pectin$,$algin$,$polysulphate$ esters).
Therefore,all the given options are correct.

(B) The correct answer is $B$ (Myxophyceae).
Myxophyceae,also known as Cyanophyceae or blue-green algae,consists of prokaryotic organisms.
Due to their prokaryotic nature,they lack organized nuclei,membrane-bound organelles,and complex sexual reproduction mechanisms involving meiosis or gamete fusion.
Furthermore,they do not possess flagellated or motile cells at any stage of their life cycle.

(B) $Postelsia$ is a genus of brown algae commonly known as the sea palm. It is found on the rocky shores of the northeastern Pacific Ocean. It is characterized by a stipe that resembles the trunk of a palm tree,topped with leaf-like blades.

(D) $Agar-agar$ is a jelly-like substance.
It is a non-nitrogenous carbohydrate consisting of two polysaccharides,namely $agarose$ and $agaropectin$.
It is obtained from several red algae (Rhodophyceae),such as $Gracillaria$,$Gelidium$,and $Gigartina$.
It was discovered by Lady Hesse and was famously used by Robert Koch to solidify culture media in microbiology.

(B) Kelps like $Fucus$ and $Laminaria$ (members of $Phaeophyceae$ or Brown algae) are a rich source of iodine.
Approximately $25$% of the total iodine is obtained from kelps,which also contain other elements like bromine,$Cu$,$Zinc$,$Fe$,$Boron$,$Mn$,and $Mo$.
Due to the presence of iodine,dried kelps are used to treat goiter.

(A) coenocytic thallus is a multinucleate cell that is not divided into separate cells by septa.
In $Vaucheria$,the vegetative body is siphonaceous and multinucleate because there are no cross-walls (septa) formed,except during the formation of reproductive structures.
Therefore,$Vaucheria$ is a classic example of coenocytic algae.

(C) In the life cycle of members of the class $Rhodophyceae$ (red algae),both spores and gametes are non-motile.
They lack flagella at any stage of their life cycle.
In contrast,members of $Chlorophyceae$ and $Phaeophyceae$ produce flagellated motile spores and gametes.

(A) $coenobium$ is a specific type of algal colony where the number of cells is fixed at the time of formation and does not change during the life of the colony. Examples include $Volvox$,$Eudorina$,and $Pandorina$. These are often organized as hollow spherical structures.

(C) $Cephaleuros \text{ } virescens$ is a member of the class $Chlorophyceae$. It acts as a parasitic alga and causes the disease known as 'red rust of tea' in tea leaves $(Thea \text{ } sinensis)$.

(C) The cell wall of algae is primarily composed of cellulose,galactans,and mannans,along with minerals like calcium carbonate in some species.
Among the given options,cellulose is the primary structural polysaccharide found in the cell wall of algae.
Chitin is found in the cell walls of fungi,while cutin and suberin are waxy substances found in higher plants.

(D) . $Gelidium$ is a red alga (Rhodophyceae) which is commercially used to produce agar-agar. Agar is a gelatinous substance used in laboratories for culturing microorganisms and in food industries as a thickening agent.

(A) $Volvox$ is a colonial green alga that forms a spherical,motile colony known as a coenobium.
Each colony consists of numerous flagellated cells arranged in a single layer at the periphery of a gelatinous matrix.
The flagella allow the entire colony to move through the water,making it a motile colony.
$Nostoc$ forms non-motile colonies,$Spirogyra$ is a filamentous,non-motile alga,and $Chlamydomonas$ is a unicellular,motile alga.

(B) In $Chlamydomonas$,the life cycle is haplontic. In this type of life cycle,the dominant phase is the free-living haploid gametophyte. The sporophytic generation is represented only by the single-celled zygote,which undergoes meiosis to produce haploid spores. Therefore,the zygote is the only diploid stage in its life cycle.

(D) Pyrenoids are proteinaceous storage bodies found in the chloroplasts of algae.
$Ulothrix$ typically contains a single,large,girdle-shaped chloroplast with one or more pyrenoids.
$Spirogyra$ contains ribbon-shaped,spiral chloroplasts that possess multiple pyrenoids.
$Oedogonium$ has a reticulate chloroplast with many pyrenoids.
Therefore,all the mentioned algae contain more than one pyrenoid.

(A) . Hypnospores are thick-walled,non-motile spores formed to survive unfavourable conditions.
They germinate upon the arrival of favourable conditions.
Examples include $Chlamydomonas$ and $Ulothrix$.

(C) The statement 'All algae are filamentous' is incorrect.
Algae exhibit a wide range of body forms,including unicellular (e.g.,$Chlamydomonas$),colonial (e.g.,$Volvox$),and filamentous (e.g.,$Ulothrix$ and $Spirogyra$).
Since not all algae are filamentous,this statement is false.
Most algae are photosynthetic,they are classified into three main classes based on their pigments (Chlorophyceae,Phaeophyceae,and Rhodophyceae),and $Spirogyra$ reproduces sexually via conjugation and does not produce motile zoospores.

(D) The presence of the same type of photosynthetic pigments is considered the most reliable indicator of evolutionary relationship among algae.
In algal classification,the type of pigments (such as chlorophyll $a$,$b$,$c$,$d$,fucoxanthin,phycoerythrin,etc.) is a fundamental criterion used to distinguish between major groups like Chlorophyceae,Phaeophyceae,and Rhodophyceae.
Respiration and asexual reproduction are common physiological and reproductive processes found across almost all algae and do not indicate close phylogenetic relatedness.
Habitat can be influenced by environmental factors and does not necessarily reflect genetic or evolutionary proximity.

(D) Pyrenoids are specialized proteinaceous structures found within the chloroplasts of many algae.
They serve as the primary sites for the synthesis and storage of starch.
In these structures,glucose produced during photosynthesis is converted into starch for storage,making them the centre of starch formation.

(C) . Algae are considered important because they have the potential to serve as a significant source of human food in the future. They are rich in proteins,lipids,carbohydrates,and vitamins,and can be cultivated efficiently. Examples include $Chlorella$ and $Ulva$.

(C) The simplest green plants are $Algae$.
$Algae$ are chlorophyll-bearing, simple, thalloid, autotrophic, and largely aquatic organisms.
$Yeast$ is a fungus, while $Bacteria$ and $Lactobacillus$ are prokaryotic organisms that lack chlorophyll and are not classified as plants.

(B) Thermal algae (thermophytes) are specialized organisms capable of growing and surviving in extremely high-temperature environments.
These algae are typically found in hot water springs where the water temperature remains consistently high, often ranging between $70^{\circ}C$ and $80^{\circ}C$.
Examples of such algae include $Oscillatoria$, $Heteroharmogonium$, $Hapalosiphon$, and $Synechococcus \text{ } elongatus$.
Therefore, the correct option is $B$.

(C) Members of Rhodophyceae are commonly known as red algae because of the predominance of the red pigment,$r$-phycoerythrin,in their body.
$r$-phycoerythrin is a water-soluble phycobiliprotein that masks the green colour of chlorophyll $a$ and $d$,giving these algae their characteristic red appearance.

(B) In $Chlorophyta$ (green algae),the storage bodies located in the chloroplasts are known as $Pyrenoids$.
These structures consist of a central core of protein surrounded by a sheath of starch.
$Paramylum$ is the reserve food found in $Euglenoids$.
$Volutin$ granules are storage bodies found in bacteria and fungi.
An $Eye$ $spot$ (stigma) is a photoreceptive organelle found in some algae.

(C) $Zygospore$ is formed by the fusion of two haploid gametes during sexual reproduction in many algae and fungi.
Since the fusion of two haploid $(n)$ gametes results in a cell with two sets of chromosomes,the $Zygospore$ is diploid $(2n)$.

(B) The $Palmella$ stage is a survival mechanism observed in certain algae like $Chlamydomonas$.
During unfavourable conditions,such as drought or lack of water,the flagella of the zoospores are withdrawn,and the cells become non-motile.
These cells secrete a mucilaginous sheath around themselves,and they may divide to form a colony-like structure embedded in the mucilage.
This aggregation is known as the $Palmella$ stage.
When favourable conditions return,these cells are released and develop into new individual plants.

(A) In $Algae$, the sex organs are typically unicellular and non-jacketed.
Every cell within these simple sex organs is fertile and capable of producing gametes.
In contrast, in $Bryophyta$, $Pteridophyta$, and $Gymnosperm$, the sex organs are multicellular and possess a sterile jacket layer surrounding the gamete-producing cells.
Therefore, only $Algae$ exhibit the condition where all cells of the sex organs form gametes.

(C) Pyrenoids are specialized storage bodies found in the chloroplasts of many algae.
They consist of a central proteinaceous core,which is often surrounded by a sheath of starch.
Therefore,they are described as having a proteinaceous centre and a starchy sheath.

(B) The correct answer is $B$. In $Rhodophyceae$ (red algae),the stored food material is in the form of $Floridean$ starch,which is very similar to amylopectin and glycogen in structure. It stains red with iodine solution. Additionally,they also contain a soluble sugar called floridoside.

(B) Pyrenoids are specialized proteinaceous structures found within the chloroplasts of many algae.
They are involved in the storage of starch and are associated with the mechanism of carbon-concentrating,which enhances the efficiency of the enzyme $RuBisCO$ during photosynthesis.
Therefore,pyrenoids are a characteristic feature of algal chloroplasts.

(A) The giant algae,commonly known as kelps,belong to the class $Phaeophyceae$ (brown algae).
These organisms are large,multicellular,and often form dense underwater forests in marine environments.
They are referred to as 'seaweeds' or 'forests of the sea' due to their massive size and complex body structure.

(C) $Chlorella$ is considered one of the most important algae in research centers.
It is widely studied because it can be used to provide $O_2$ during space flight missions.
This alga efficiently reuses $CO_2$ produced by astronauts during the process of photosynthesis and releases $O_2$,which is essential for their survival in space.

(A) The classification of $Algae$ is primarily based on the types of photosynthetic pigments present in them,such as $Chlorophyll$ $a$,$b$,$c$,$d$,$f$,$Carotenoids$,and $Phycobilins$. Based on these pigments,$Algae$ are divided into three main classes: $Chlorophyceae$ (green algae),$Phaeophyceae$ (brown algae),and $Rhodophyceae$ (red algae). Therefore,the correct option is $A$.

(A) The red rust of tea is caused by the parasitic green alga $Cephaleuros$ $virescens$.
This alga infects the leaves of the tea plant,leading to the formation of reddish-brown patches.
The characteristic red color is due to the presence of a pigment called $haematochrome$ within the algal cells.
Similarly,$Cephaleuros$ $coffeae$ is known to attack coffee leaves.

(D) In the class $Xanthophyceae$ (yellow-green algae),the stored food material is primarily in the form of oil droplets and leucosin (a type of carbohydrate similar to starch).
Chlorophyceae stores food as starch.
Phaeophyceae stores food as complex carbohydrates like laminarin or mannitol.
Rhodophyceae stores food as floridean starch.

(A) Chlorophyll-$a$ is the primary photosynthetic pigment found in all groups of algae,including Chlorophyceae,Phaeophyceae,and Rhodophyceae. It acts as the primary electron donor in the electron transport chain during photosynthesis.

(C) Brown algae (Phaeophyceae) are characterised by the presence of chlorophyll $a$,$c$,carotenoids,and xanthophylls.
Fucoxanthin is the dominant pigment that gives them their characteristic brown color.
Examples include $Fucus$ and $Sargassum$.

(A) Thyroxin is a hormone produced by the thyroid gland,and its synthesis requires iodine.
$Laminaria$ is a type of brown algae (kelp) that is a rich natural source of iodine.
Therefore,the element present in thyroxin is obtained from $Laminaria$.

(D) is the correct answer. Carrageenan is a phycocolloid obtained from the cell wall of red algae,specifically $Chondrus$ $crispus$. It belongs to the class $Rhodophyceae$.