Algae (General) Questions in English

(C) Floridean starch is the stored food material found in Rhodophyceae (red algae).
Its chemical structure is very similar to amylopectin and glycogen,as it is a branched polysaccharide composed of glucose units linked by $\alpha-1,4$ and $\alpha-1,6$ glycosidic bonds.

(A) Chlorella is a unicellular green alga. Spirulina is a unicellular cyanobacterium (often referred to as blue-green algae). Both are widely used as food supplements due to their high protein content. In contrast,Laminaria and Sargassum are multicellular brown algae,Gelidium and Gracilaria are multicellular red algae,and while Volvox is a colonial green alga,Anabaena is a filamentous cyanobacterium.

(B) Floridean starch is the stored food material found in Red Algae (Rhodophyceae).
Its structure is very similar to amylopectin and glycogen,as it is a branched polysaccharide composed of glucose units.
Therefore,the correct option is $B$.

(B) Unicellular algae are organisms that consist of a single cell.
$Chlorella$ is a well-known unicellular green alga.
$Spirulina$ is a unicellular cyanobacterium (often studied under algae in general contexts due to its photosynthetic nature).
$Laminaria$ and $Sargassum$ are multicellular brown algae.
$Volvox$ is a colonial alga.
$Gelidium$ and $Gracilaria$ are multicellular red algae.
Therefore,the correct pair is $Chlorella$ and $Spirulina$.

(C) Isogametes are gametes that are morphologically and physiologically similar,making it impossible to distinguish them as male or female.
In many species of algae,such as $Cladophora$ and $Ulothrix$,the gametes produced are isogametes.
Most animals,gymnosperms,and angiosperms typically produce heterogametes,where male and female gametes are distinct in size and structure.

(A) Red algae (Rhodophyceae) contain the pigment phycoerythrin,which allows them to absorb blue light. Blue light penetrates the deepest into the water column compared to other wavelengths of light. Therefore,red algae are capable of performing photosynthesis at greater depths than green or brown algae.

(B) Phycoerythrin is a red-colored accessory pigment found in Rhodophyceae,commonly known as red algae. It masks the green color of chlorophyll $a$ and gives these algae their characteristic red appearance.

(C) Based on the provided diagrams from the $NCERT$ textbook:
$(a)$ represents $Fucus$,which is a brown alga characterized by air bladders,a midrib,and a holdfast.
$(b)$ represents $Porphyra$,which is a red alga.
$(c)$ represents $Laminaria$,which is a brown alga showing a distinct frond,stipe,and holdfast.
$(d)$ represents $Polysiphonia$,which is a red alga showing a filamentous,branched structure.
Therefore,the correct sequence is $(a)$ - $Fucus$,$(b)$ - $Porphyra$,$(c)$ - $Laminaria$,$(d)$ - $Polysiphonia$.

(A) Based on the provided diagrams from the $NCERT$ textbook:
$(i)$ represents $Porphyra$,which is a red alga with a leafy thallus.
$(ii)$ represents $Polysiphonia$,which is a filamentous red alga.
$(iii)$ represents $Chara$,a green alga that shows a complex,plant-like structure.
$(iv)$ represents $Dictyota$,a brown alga characterized by a flattened,dichotomously branched thallus.
Therefore,the correct sequence is $(i) - Porphyra, (ii) - Polysiphonia, (iii) - Chara, (iv) - Dictyota$.

(C) Seaweeds,particularly members of brown algae known as kelps,are a rich and primary source of iodine. Examples include genera such as $Laminaria$,$Macrocystis$,and $Fucus$.

(B) Brown algae (Phaeophyceae) vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment,$Fucoxanthin$,present in them. $Fucoxanthin$ is the dominant accessory pigment that masks the green colour of chlorophyll $a$ and $c$.

(D) Green algae (Chlorophyceae) contain chlorophyll-$a$ and chlorophyll-$b$ as the primary photosynthetic pigments.
They also contain carotenoids,which are accessory pigments.
These pigments are located in the grana of the chloroplast,similar to land plants.
Additionally,the reserve food material in green algae is stored in the form of starch.

(D) The 'Red Sea' gets its characteristic red colour due to the presence of a cyanobacterium (blue-green algae) known as $Trichodesmium$ $erythreum$. This organism contains a red pigment that blooms in the water,giving it a reddish appearance.

(A) The reserve food material in different classes of algae is as follows:
$1$. Rhodophyceae (Red algae): Floridean starch.
$2$. Phaeophyceae (Brown algae): Laminarin and mannitol.
$3$. Chlorophyceae (Green algae): Starch.
Therefore,floridean starch is the characteristic reserve food material of Rhodophyceae.

(A) Brown algae (Phaeophyceae) contain chlorophyll-$a$,chlorophyll-$c$,carotenoids,and xanthophylls.
Fucoxanthin is the specific xanthophyll pigment responsible for the brown color in these algae.
Chlorophyll-$b$ is absent in brown algae; it is a characteristic pigment of green algae (Chlorophyceae).
Therefore,the statement that chlorophyll-$a$ and $b$ are present in brown algae is incorrect.

(A) $Acetabularia$ is a genus of single-celled marine green algae belonging to the class $Chlorophyceae$.
It is famous for its large size and for being a model organism in cell biology experiments,particularly those conducted by Joachim $H$ämmerling to demonstrate the role of the nucleus in controlling cellular morphogenesis.

(C) $Chlorella$ is a unicellular green alga that is used in space research for oxygen regeneration and air purification. It consumes carbon dioxide produced by astronauts and releases oxygen through photosynthesis,making it ideal for closed-loop life support systems in space ships.

(A) The cells of $Spirogyra$ are longer than their breadth. The cell wall is two-layered. The inner wall is made up of cellulose and the outer of pectose. When pectose comes in contact with water,it makes the filament slimy or slippery. Hence,this alga is commonly called pond silk.

(A) Green algae store food in the form of starch in specialized structures called pyrenoids located in the chloroplast.
Each pyrenoid consists of a central protein core and a surrounding starch sheath.

(B) Brown algae (Phaeophyceae) show great variation in size and form.
They range from simple branched,filamentous forms (e.g.,Ectocarpus) to profusely branched forms as represented by kelps,which may reach a height of $100 \, m$.
Sargassum is a well-known genus of brown algae.
The giant brown algae are called kelps.
Therefore,both Kelp and Sargassum belong to the class Phaeophyceae,commonly known as brown algae.

(D) Agar-agar is a gelatinous substance obtained from certain species of red algae (Rhodophyceae),primarily $Gelidium$ and $Gracilaria$.
These algae are commercially important because they produce agar,which is widely used in laboratories as a culture medium for growing microorganisms and in the food industry for thickening and stabilizing products.

(C) The fusion of morphologically dissimilar gametes,which may be motile or non-motile,is called $ANISOGAMY$.
In $OOGAMY$,there is a fusion of dissimilar gametes where the female gamete is usually larger and non-motile,while the male gamete is smaller and motile.
In $ISOGAMY$,there is a fusion of morphologically similar gametes (motile or non-motile).
Therefore,the correct term for the fusion of morphologically dissimilar gametes is $ANISOGAMY$.

(A) $Chlamydomonas$,$Volvox$,$Ulothrix$,$Spirogyra$,and $Chara$ are well-known examples of the class-$Chlorophyceae$,commonly referred to as green algae.
These organisms possess chlorophyll $a$ and $b$ as their primary photosynthetic pigments,which gives them their characteristic green color.

(C) Sexual reproduction involves the formation of gametes and their fusion during the process called fertilisation.
Depending upon the structure and behavior of gametes,there are different types of sexual reproduction:
$(i)$ Isogamy: Fusion of morphologically alike gametes which look and behave similarly.
$(ii)$ Anisogamy: Fusion of morphologically dissimilar gametes,which may be motile or non-motile.
$(iii)$ Oogamy: Fusion of a large non-motile egg or ovum with a smaller motile sperm (except in Rhodophyceae).
Since all these processes involve the fusion of gametes,the correct answer is Gametes.

(D) Members of the class $Chlorophyceae$,commonly known as green algae,exhibit a diverse range of body structures. They can be unicellular (e.g.,$Chlamydomonas$),colonial (e.g.,$Volvox$),or filamentous (e.g.,$Ulothrix$ and $Spirogyra$). Therefore,all the given options are correct.

(D) Agar-agar is a gelatinous substance commercially extracted from red algae,specifically $Gelidium$ and $Gracilaria$.
It is widely used in laboratories for solidifying culture media.
Additionally,it serves as a stabilizer or thickener in the food industry for products like jellies,puddings,creams,cheese,and bakery items.

(C) Algae reproduce asexually by the production of different types of spores.
The most common type of spore is the $Zoospore$.
$Zoospores$ are motile,flagellated structures that germinate to give rise to a new plant body.

(A) In a haplontic life cycle,the dominant,photosynthetic phase is the free-living gametophyte $(n)$.
The zygote $(2n)$ is the only diploid stage,which undergoes meiosis to produce haploid spores $(n)$.
These spores divide mitotically to form the gametophyte.
This type of life cycle is characteristic of many algae,such as $Volvox$ and $Spirogyra$,and some species of $Chlamydomonas$.

(A) Carrageenin is a phycocolloid,which is a polysaccharide extracted from the cell walls of certain red algae (Rhodophyceae).
Specifically,it is commercially obtained from the red alga known as $Chondrus$ $crispus$,commonly referred to as Irish moss.

(B) In class-$Phaeophyceae$ (brown algae),the food is stored as complex carbohydrates,in the forms of laminarin or mannitol.
Laminarin is a polysaccharide (a type of carbohydrate),and mannitol is a sugar alcohol derived from mannose.

(B) $Volvox$,$Spirogyra$,and $Chlamydomonas$ are all green algae belonging to the class $Chlorophyceae$.

(D) Algae exhibit a wide range of body forms.
$1$. Unicellular forms: These are single-celled organisms,for example,$Chlamydomonas$.
$2$. Filamentous forms: These consist of cells arranged in a thread-like structure,for example,$Ulothrix$ and $Spirogyra$.
$3$. Colonial forms: These consist of groups of individuals living together in a colony,for example,$Volvox$.
Therefore,$A$ refers to $Chlamydomonas$,$B$ refers to $Ulothrix$,and $C$ refers to $Volvox$.

(A) $Chara$ is a green alga that belongs to the class $Charophyceae$. It is known for its characteristic calcium carbonate deposits on its surface,which is referred to as calcium encrustation. Additionally,$Chara$ is known to possess larvicidal properties,meaning it can kill mosquito larvae,and is often used in biological control to reduce mosquito populations in stagnant water bodies.

(D) The given characteristics describe the class $Rhodophyceae$ (Red Algae).
$1$. $Rhodophyceae$ members reproduce asexually by non-motile spores and sexually by non-motile gametes.
$2$. Sexual reproduction is oogamous,and it is characterized by complex post-fertilization developments.
$3$. Common examples of this class include $Polysiphonia$,$Porphyra$,$Gracilaria$,and $Gelidium$.

(C) Oogamy is a form of sexual reproduction involving the fusion of a large,non-motile female gamete (egg or ovum) with a smaller,motile male gamete (sperm).
These gametes differ both morphologically and physiologically.
This process is observed in various algae such as $Chlamydomonas$,$Fucus$,$Chara$,and $Volvox$.

(A) Statement $I$ is correct: In red algae (Rhodophyceae),vegetative reproduction occurs primarily through fragmentation.
Statement $II$ is correct: The stored food material in red algae is floridean starch,which is structurally very similar to amylopectin and glycogen.
Statement $III$ is incorrect: The cell wall of red algae is composed of cellulose,pectic compounds,and phycocolloids (such as agar and carrageenan),not chitin. Chitin is typically found in the cell walls of fungi.
Therefore,statements $I$ and $II$ are correct.

(A) Algae are chlorophyll-bearing,simple,thalloid,autotrophic,and largely aquatic organisms.
Statement $I$ is correct: The plant body of algae is thalloid,meaning it is not differentiated into roots,stems,and leaves.
Statement $II$ is correct: Most algae are aquatic (both fresh water and marine).
Statement $III$ is correct: Algae reproduce by vegetative (fragmentation),asexual (various types of spores),and sexual (fusion of gametes) methods.
Statement $IV$ is incorrect: While $Volvox$ is a colonial form,$Ulothrix$ is a filamentous form of algae. Therefore,the correct statements are $I, II,$ and $III$.

(D) $Cephaleuros$ is a genus of green algae that acts as a parasite. It is well-known for causing the disease known as 'red rust' in economically important crops such as tea and coffee.

(D) Volvox is a freshwater green alga. It exists in colonies known as coenobium,which are surrounded by a gelatinous layer. Each cell in the colony is pyriform (pear-shaped) and possesses two long,similar,and smooth flagella. Therefore,the statement that Volvox is non-flagellated is incorrect.

(C) Based on the $NCERT$ textbook diagrams for the chapter 'Plant Kingdom':
$A$ represents $Fucus$,a brown alga characterized by air bladders,a midrib,and a holdfast.
$B$ represents $Dictyota$,a brown alga with a distinct main axis and branches.
$C$ represents $Porphyra$,a red alga with a leaf-like frond.
$D$ represents $Polysiphonia$,a red alga showing a branched thallus structure with a stipe and fronds.
Therefore,the correct sequence is $A-Fucus, B-Dictyota, C-Porphyra, D-Polysiphonia$.

(C) In class-$Chlorophyceae$,asexual reproduction occurs mainly through flagellated zoospores that are produced within structures called zoosporangia.
Sexual reproduction in this class exhibits significant variation in the type and formation of sex cells (gametes).
It can be classified into three types: isogamous (gametes are similar in structure),anisogamous (gametes are dissimilar in size),and oogamous (large non-motile egg and small motile sperm).
Therefore,both statement $I$ and statement $II$ are correct.

(A) In the plant kingdom,most algae exhibit a haplontic life cycle,where the dominant phase is the haploid gametophyte.
However,certain algae exhibit a haplo-diplontic life cycle,where both haploid and diploid phases are multicellular and often free-living.
Examples of such algae include $Ectocarpus$,$Polysiphonia$,and various species of $Kelps$ (large brown algae).
Therefore,the correct set representing haplo-diplontic algae is $A-Ectocarpus, B-Polysiphonia, C-Kelps$.

(A) Plants that lack a well-differentiated body structure,such as roots,stems,and leaves,are known as thallophytes.
Algae belong to the group Thallophyta,which is characterized by a simple,undifferentiated plant body called a thallus.
In contrast,Pteridophytes,Gymnosperms,and Angiosperms possess well-differentiated plant bodies with true roots,stems,and leaves.

(D) The cell wall of $Spirogyra$ (a green alga) consists of an inner layer of cellulose and an outer layer of pectin. Therefore,both cellulose and pectin are present in its cell wall structure.

(A) Kelps belong to the class $Phaeophyceae$,which are commonly known as brown algae. They are known for their massive size and can reach heights of up to $100 \ m$.

(A) Laminarin and mannitol are the characteristic stored food materials found in Phaeophyceae,commonly known as brown algae.
Among the given options,$Dictyota$ belongs to the class Phaeophyceae (brown algae).
$Volvox$ and $Chlamydomonas$ are green algae (Chlorophyceae),which store food as starch.
$Polysiphonia$ is a red alga (Rhodophyceae),which stores food as floridean starch.

(C) Sexual reproduction in red algae $(Rhodophyceae)$ is oogamous.
$Gracilaria$ and $Gelidium$ are examples of red algae that exhibit oogamous sexual reproduction.

(B) $Ectocarpus$ is a type of brown algae $(Phaeophyceae)$ that exhibits a branched,filamentous body structure.

(C) In algae,the photosynthetic pigments are contained within specialized organelles called chloroplasts. These organelles are the sites of photosynthesis,where light energy is captured by pigments such as chlorophyll to synthesize organic compounds.

(A) In a haplontic life cycle,the sporophytic generation is represented only by the one-celled zygote. There are no free-living sporophytes. Meiosis in the zygote results in haploid spores,which divide to form the gametophyte. The dominant photosynthetic phase in such plants is the free-living gametophyte. This pattern is characteristic of many algae,such as $Volvox$ and $Spirogyra$.