Algae (General) Questions in English

(B) In a diplontic life cycle,the diploid sporophyte is the dominant,photosynthetic,and independent phase of the plant.
- The gametophytic phase is represented by the single to few-celled haploid gametophyte.
- Among the given options,$Fucus$ is a brown alga that exhibits a diplontic life cycle.
- $Spirogyra$,$Ulothrix$,and $Polysiphonia$ exhibit haplontic or haplo-diplontic life cycles.

(D) $Volvox$ is a green alga that exists as a colony of cells.
Each colony is spherical and consists of hundreds to thousands of cells embedded in a gelatinous matrix.
These cells possess flagella,which allow the entire colony to move through the water,making it colonial and motile.

(C) Brown algae (Phaeophyceae) exhibit a great variation in size and form. They range from simple branched,filamentous forms to profusely branched forms. They are primarily marine organisms and are found in great abundance in temperate sea water,although some species can also be found in tropical regions.

(D) Red algae (Rhodophyceae) store food as floridean starch,which is very similar to amylopectin and glycogen in structure.
They are also characterized by the complete absence of flagella at any stage of their life cycle,making them nonflagellate.

(B) In Spirogyra,conjugation is of two types: lateral and scalariform.
Lateral conjugation occurs between adjacent cells of the same filament,resulting in empty cells alternating with zygospores.
Scalariform conjugation occurs between cells of two different filaments,resulting in zygospores in one of the filaments while the other becomes empty.
Since the question specifies that zygospores alternate with empty cells within the same filament,it refers to lateral conjugation.
Each zygospore undergoes meiosis to produce $4$ haploid nuclei. Out of these $4$ nuclei,$3$ degenerate and only $1$ remains functional to form a germ tube,which develops into a new daughter filament.
Therefore,$100$ zygospores will produce $100$ new daughter filaments.

(D) Algin is a phycocolloid (hydrocolloid) found in the cell wall of brown algae (Phaeophyceae).
Examples of brown algae that produce algin include $Macrocystis$,$Fucus$,and $Laminaria$.
Therefore,among the given options,$Macrocystis$ and $Fucus$ are the correct representatives.

(D) Red algae (Rhodophyceae) typically appear red due to the presence of the pigment $r$-phycoerythrin. However,some species do not exhibit a red color. Among the given options,$Batrachospermum$ is a freshwater red alga that appears bluish-green or violet-brown rather than red. Therefore,it is a red alga that is not red.

(B) In $Chlorophyceae$ (green algae),the flagella are of the whiplash type. These flagella are typically equal in number and apical in position.

(A) Sea kelps are rich sources of iodine $(I_2)$ and bromine $(Br_2)$. Iodine is an essential trace element required for the synthesis of thyroid hormones,and its deficiency leads to goitre. Therefore,sea kelps are useful for curing goitre.

(B) In the division $Rhodophyta$ (red algae),the life cycle is characterized by the complete absence of flagellated stages. Both male and female gametes are non-motile. The male gamete is known as a spermatium,which is carried by water currents to the female reproductive organ,the carpogonium. Therefore,non-motile gametes are a characteristic feature of $Rhodophyta$.

(B) In red algae (Rhodophyceae),the female sex organ is a specialized structure called the carpogonium. It is flask-shaped and consists of a swollen basal portion containing the egg and an elongated neck-like structure known as the trichogyne,which receives the male gametes (spermatia).

(B) $Laminaria$ is a member of Phaeophyceae (brown algae).
Its characteristic features include:
- $c.$ Alginic acid (present in the cell wall of brown algae).
- $d.$ Trumpet hyphae (specialized cells found in the medulla of large brown algae like $Laminaria$).
- $e.$ Haplodiplontic life cycle (common in most brown algae).
- $g.$ Fucoxanthin (the pigment responsible for the brown color).
Therefore,the correct set is $c, d, e, g$.

(A) Thallophytes (primarily Algae) are characterized by a simple,undifferentiated plant body known as a thallus.
They lack specialized vascular tissues ($Xylem$ and $Phloem$),which makes them non-vascular.
They do not possess archegonia (female sex organs found in Bryophytes,Pteridophytes,and Gymnosperms),making them non-archegoniate.
They lack a true root,stem,and leaf system,which makes them non-cormophytic.
Since the Reason accurately explains the structural characteristics that define the Thallophytes mentioned in the Assertion,both are correct and the Reason is the correct explanation.

(B) Pyrenoids are proteinaceous storage bodies found in the chloroplasts of many algae. They often contain starch,which may be present as a sheath around the protein core. In higher plants,specialized plastids called amyloplasts are responsible for the storage of starch,effectively serving a similar storage function as pyrenoids in algae. Therefore,both the Assertion and the Reason are scientifically correct statements.

(A) In $Chlorophyceae$ (green algae),sexual reproduction exhibits significant diversity. It can occur through the fusion of gametes that are similar in size (isogamous),dissimilar in size (anisogamous),or through the fusion of a large non-motile female gamete and a smaller motile male gamete (oogamous). Since the variation in the type and formation of sex cells is directly explained by the occurrence of these three modes of reproduction,the Reason correctly explains the Assertion.

(A) Isogamy refers to the fusion of morphologically similar gametes.
In $Spirogyra$,the gametes are non-flagellated (non-motile) and morphologically similar,representing a condition of isogamy.
$Volvox$ and $Fucus$ exhibit oogamy (fusion of large non-motile egg and small motile sperm).
$Chlamydomonas$ exhibits isogamy,but its gametes are flagellated (motile).

(C) The most common asexual reproductive structures in algae are zoospores. Zoospores are microscopic,motile structures that possess flagella,which allow them to swim in water to find suitable conditions for germination.

(D) Chara is a green alga that exhibits a complex reproductive structure.
It possesses multicellular and jacketed sex organs, which is a characteristic feature.
The male sex organ is known as the Globule $( male )$, and the female sex organ is known as the Nucule $( female )$.
Therefore, both statements $(b)$ and $(c)$ are correct.

(A) In $Chara$,the plant body is monoecious,meaning both male (antheridium) and female (oogonium) sex organs are present on the same plant.
However,$Chara$ exhibits a condition known as protandry,where the male sex organs (antheridia) mature earlier than the female sex organs (oogonia).
Because the male gametes are released before the female gametes are ready for fertilization,self-fertilization is prevented,and the plant undergoes cross-fertilization.
Therefore,both the Assertion and the Reason are correct,and the Reason is the correct explanation for the Assertion.

(A) $Fucus$ is a genus of brown algae (Phaeophyceae) that exhibits oogamy.
Oogamy is a form of sexual reproduction where a large,non-motile (or less motile) female gamete (egg) fuses with a smaller,motile male gamete (sperm/antherozoid).
Since the female gamete is significantly larger and non-motile compared to the male gamete,the definition of oogamy is satisfied.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for why $Fucus$ exhibits oogamy.

(C) $Volvox$ is an alga that exhibits oogamy,which is a type of heterogamy where the male gamete is small and motile (flagellated) and the female gamete is large and non-motile.
Since the male gametes are motile and swim to reach the female gamete,the statement that non-motile gametes are transferred by water is incorrect.
Therefore,the Assertion is correct,but the Reason is incorrect.

(A) The distribution of algae in the ocean depends on the penetration of light at different depths.
$1.$ Green algae (Chlorophyceae) are found at the shallowest depths because they require high light intensity for photosynthesis.
$2.$ Brown algae (Phaeophyceae) are found at intermediate depths.
$3.$ Red algae (Rhodophyceae) are found at the greatest depths because they can perform photosynthesis even in low light conditions using their accessory pigments (phycoerythrin).
Therefore,the correct matching is $a(i), b(ii), c(iii)$.

(C) Carrageen is a type of phycocolloid,which is a gelatinous substance extracted from the cell walls of certain marine algae.
Specifically,carrageen is obtained from the cell walls of red algae (Rhodophyceae).
These substances are widely used in the food and pharmaceutical industries as thickening and stabilizing agents.
Therefore,the correct option is $C$.

(B) The reserve food material in algae varies according to the class:
$1$. Phaeophyceae (Brown algae) store food as complex carbohydrates,usually in the form of mannitol or laminarin.
$2$. Ectocarpus belongs to the class Phaeophyceae.
$3$. Gracilaria belongs to Rhodophyceae (Red algae),which stores food as floridean starch.
$4$. Volvox and Ulothrix belong to Chlorophyceae (Green algae),which store food as starch.

(B) Hydrocolloids are water-holding substances.
Carrageen is a specific type of hydrocolloid obtained from the cell wall of red algae,which belong to the class $Rhodophyceae$.
Brown algae $(Phaeophyceae)$ produce algin,while red algae $(Rhodophyceae)$ produce carrageen.
Therefore,the correct option is $B$.

(A) $Ullothrix$ is a green alga (Chlorophyceae),and its stored food is starch,not mannitol. Mannitol is the stored food in brown algae (Phaeophyceae).
$Porphyra$ is a red alga (Rhodophyceae),and its stored food is Floridean starch,which is correctly matched.
$Volvox$ is a green alga (Chlorophyceae),and its stored food is starch,which is correctly matched.
$Ectocarpus$ is a brown alga (Phaeophyceae),and it contains the pigment Fucoxanthin,which is correctly matched.
Therefore,the incorrect match is $Ullothrix - Mannitol$.

(D) Algae are chlorophyll-bearing,simple,thalloid,autotrophic,and largely aquatic organisms.
They occur in a variety of habitats:
$1$. They are found in moist stones,soils,and wood.
$2$. Some algae form symbiotic associations with fungi (e.g.,lichens) and animals (e.g.,on sloth bears).
$3$. They are also found in marine and freshwater environments.
Therefore,all the given options represent habitats or associations where algae can be found.

(B) Algae are chlorophyll-bearing,simple,thalloid,autotrophic,and largely aquatic organisms.
They do not possess true roots,stems,or leaves; instead,their plant body is a thallus.
Therefore,the statement that they are 'root,stem,and leaf-bearing' is incorrect.

(D) The correct matching is based on the body forms of algae:
$P$. Unicellular: $Chlamydomonas$ is a unicellular green alga $(P-II)$.
$Q$. Colonial: $Volvox$ forms spherical colonies $(Q-I)$.
$R$. Filamentous: $Ulothrix$ and $Spirogyra$ have a filamentous body structure $(R-III)$.
$S$. Massive plant body: Kelps are large, massive brown algae $(S-IV)$.
Therefore, the correct sequence is $(P-II), (Q-I), (R-III), (S-IV)$.

(D) Asexual reproduction in algae commonly occurs by the production of different types of spores,the most common being zoospores. These are flagellated (motile) and on germination give rise to new plants. Fragmentation is also a common method of vegetative reproduction in algae,where the thallus breaks into fragments,each of which grows into a new individual. Fusion of gametes is a characteristic of sexual reproduction,not asexual reproduction. Therefore,both fragmentation and spore formation are modes of asexual/vegetative reproduction in algae.

(B) In algae,sexual reproduction occurs through the fusion of two gametes. These gametes can be flagellated (similar in size) or non-flagellated (similar in size) as in $Isogamous$ (e.g.,$Spirogyra$,$Chlamydomonas$).
Anisogamous reproduction involves the fusion of two gametes dissimilar in size,as seen in some species of $Chlamydomonas$.
Oogamous reproduction involves the fusion of one large,non-motile (static) female gamete and a smaller,motile male gamete,as seen in $Volvox$ and $Fucus$.
Therefore,the correct matching is: $P-II, Q-III, R-I$.

(A) Algae are photosynthetic organisms that play a crucial role in the ecosystem.
$1$. Algae perform at least $50\%$ of the total carbon dioxide fixation on Earth through photosynthesis,not $20\%$. Therefore,option $A$ is incorrect.
$2$. Being photosynthetic,they release oxygen into the water,increasing the level of dissolved oxygen in their immediate environment.
$3$. They serve as primary producers,forming the base of food chains for all aquatic animals.
Thus,the statement in option $A$ is factually incorrect.

(B) Hydrocolloids are water-holding substances.
Red algae (Rhodophyceae) produce carrageen.
Brown algae (Phaeophyceae) produce algin.
Therefore,the correct sequence is Carrageen from red algae and Algin from brown algae.

(D) Agar is a commercial product obtained from certain marine red algae.
Specifically,the red algae $Gelidium$ and $Gracilaria$ are the primary sources used to extract agar.
Agar is widely used in laboratories as a culture medium for the growth of microorganisms and in the food industry for the preparation of ice creams and jellies.
Therefore,both $Gelidium$ and $Gracilaria$ are correct sources.

(B) In the classification of the plant kingdom,the suffix '-phyceae' is used to denote a $Class$.
Chlorophyceae (green algae),Phaeophyceae (brown algae),and Rhodophyceae (red algae) are the three major classes under the division Thallophyta (Algae).
Therefore,these are examples of the taxonomic category $Class$.

(A) The classification of algae is based on their pigments and stored food:
$1$. Phaeophyceae are commonly known as brown algae due to the presence of fucoxanthin.
$2$. Chlorophyceae are commonly known as green algae due to the dominance of chlorophyll $a$ and $b$.
$3$. Rhodophyceae are commonly known as red algae due to the presence of phycoerythrin.
Therefore, the correct matching is: $P-II, Q-III, R-I$.

(B) The members of Chlorophyceae (green algae) contain chlorophyll $a$ and $b$ as the primary photosynthetic pigments. Option $B$ mentions chlorophyll $c$,which is incorrect because chlorophyll $c$ is found in Phaeophyceae (brown algae). Therefore,option $B$ is the incorrect statement.

(D) Pyrenoids are specialized storage bodies found in the chloroplasts of many algae.
They are composed of a central core of protein surrounded by starch plates.
Therefore,the correct location is the chloroplast,and the composition is protein and starch.

(A) The members of Chlorophyceae (green algae) have a rigid cell wall.
This cell wall is made up of an inner layer of cellulose and an outer layer of pectose.
Cellulose provides structural strength,while the outer pectose layer is gelatinous in nature.

(D) The figure on the left shows a colonial form of green algae known as $Volvox$. It consists of a spherical colony of numerous cells.
The figure on the right shows a filamentous form of green algae known as $Ulothrix$.
Therefore,the correct identification is $Volvox$ and $Ulothrix$.

(B) The classification of algae based on flagellar characteristics is as follows:
$1$. Chlorophyceae $(P)$: They possess $2-8$ equal flagella which are apical in position. Thus, $P-III$.
$2$. Phaeophyceae $(Q)$: They possess $2$ unequal flagella which are lateral in position. Thus, $Q-I$.
$3$. Rhodophyceae $(R)$: They are characterized by the complete absence of flagella in their life cycle. Thus, $R-II$.
Therefore, the correct matching is $(P-III), (Q-I), (R-II)$.

(C) The organisms listed are all algae.
$Laminaria$,$Fucus$,and $Dictyota$ belong to the class $Phaeophyceae$ (brown algae).
$Chara$ belongs to the class $Chlorophyceae$ (green algae).
Therefore,$Chara$ is the odd one out.

(B) Brown algae (Phaeophyceae) exhibit the following characteristics:
$(I)$ They contain chlorophyll $a$,$c$,carotenoids,and xanthophylls (specifically fucoxanthin). Statement $(I)$ is incorrect because it mentions chlorophyll $d$ instead of $c$.
$(II)$ They vary in color from olive green to various shades of brown depending upon the amount of the xanthophyll pigment,fucoxanthin,present in them. This is correct.
$(III)$ Food is stored as complex carbohydrates,which may be in the form of laminarin or mannitol. This is correct.
$(IV)$ The cell wall is composed of cellulose and is covered on the outside by a gelatinous coating of algin. This is correct.
$(V)$ The cell wall is covered on the outside by a gelatinous coating of algin. This is correct.
Therefore,statements $(II), (III), (IV),$ and $(V)$ are correct.

(D) The body of algae (specifically brown algae) consists of three main parts:
$1$. Holdfast: This part serves to attach the algae to a rock or other substratum.
$2$. Stipe: This is a stalk-like structure that connects the holdfast to the frond.
$3$. Frond: This is a leaf-like photosynthetic organ that performs the function of food production.
Therefore,all the given options are correct.

(C) Brown algae (Phaeophyceae) are characterized by the presence of pear-shaped (pyriform) gametes.
These gametes typically have two laterally attached flagella.
In contrast,green algae and red algae generally do not exhibit this specific pear-shaped morphology for their gametes.

(C) The provided image shows three different types of brown algae (Phaeophyceae) as described in the $NCERT$ textbook:
$1$. The first figure on the left is $Laminaria$.
$2$. The middle figure is $Fucus$.
$3$. The third figure on the right is $Dictyota$.
Therefore,the correct sequence is Laminaria,Fucus,Dictyota.

(D) Rhodophyceae,commonly known as red algae,contain chlorophyll $a$ and $d$ as photosynthetic pigments. However,the characteristic red color is due to the predominance of the water-soluble red pigment $r$-phycoerythrin. This pigment masks the green color of chlorophyll,giving the algae their distinct red appearance.

(C) Red algae (Rhodophyceae) are found at greater depths in the oceans compared to green and brown algae.
This is because red algae contain the pigment phycoerythrin,which can absorb blue light that penetrates deeper into the water column.
Green and brown algae are typically found in shallower waters where more sunlight is available for photosynthesis.

(D) The classification of algae is based on their pigments and stored food materials:
$1$. Green Algae (Chlorophyceae) include organisms like $Ulothrix$ and $Spirogyra$. Thus,$P-I$.
$2$. Red Algae (Rhodophyceae) include organisms like $Gracilaria$ and $Gelidium$. Thus,$Q-II$.
$3$. Brown Algae (Phaeophyceae) include organisms like $Ectocarpus$ and $Sargassum$. Thus,$R-III$.
Therefore,the correct matching is $(P-I), (Q-II), (R-III)$.

(B) In the kingdom $Plantae$,specifically within the algae group,the members of $Rhodophyceae$ (Red algae) are characterized by the absence of flagellated or motile stages in their life cycle.
They reproduce sexually by non-motile gametes.
In contrast,Green algae $(Chlorophyceae)$ and Brown algae $(Phaeophyceae)$ typically produce motile (flagellated) gametes or zoospores.