Phaeophyceae - 1
1
The members of Phaeophyceae or brown algae are found primarily in which habitat?
Practice
A
Freshwater habitats
B
Marine habitats
C
Terrestrial habitats
D
Desert habitats
✅ Show Answer
✔ Correct Answer:
B
(Marine habitats)
💡 Explanation
Phaeophyceae: Dictionary meaning — a class of algae commonly known as brown algae.
Explanation — Phaeophyceae are predominantly marine algae and are commonly found in seas and oceans, especially in cooler marine regions.
Brown algae: Dictionary meaning — algae that are generally brown or olive-brown in colour because of the presence of the pigment fucoxanthin.
Explanation — Brown algae belong mainly to the class Phaeophyceae and are primarily found in marine habitats.
Marine habitat: Dictionary meaning — an environment associated with seas and oceans where marine organisms live.
Explanation — Most members of Phaeophyceae grow attached to rocks or other surfaces in marine environments.
Given Statement - The members of Phaeophyceae or brown algae are found primarily in marine habitats.
Explanation — Phaeophyceae are predominantly marine algae and are commonly found in seas and oceans, especially in cooler marine regions.
Brown algae: Dictionary meaning — algae that are generally brown or olive-brown in colour because of the presence of the pigment fucoxanthin.
Explanation — Brown algae belong mainly to the class Phaeophyceae and are primarily found in marine habitats.
Marine habitat: Dictionary meaning — an environment associated with seas and oceans where marine organisms live.
Explanation — Most members of Phaeophyceae grow attached to rocks or other surfaces in marine environments.
Given Statement - The members of Phaeophyceae or brown algae are found primarily in marine habitats.
🎯 Conclusion
The members of Phaeophyceae, commonly called brown algae, are found primarily in marine habitats. They are especially common in seas and oceans.
2
Which of the following correctly describes the variation in size and form of Phaeophyceae?
Practice
A
They are always unicellular and microscopic in size.
B
They range from simple branched, filamentous forms such as Ectocarpus to profusely branched kelps that may reach about 100 metres in height.
C
They are all non-branched and remain less than one metre in height.
D
They are mainly spherical colonies and never form large thalli.
✅ Show Answer
✔ Correct Answer:
B
(They range from simple branched, filamentous forms such as Ectocarpus to profusely branched kelps that may reach about 100 metres in height.)
💡 Explanation
Phaeophyceae: Dictionary meaning — a class of algae commonly known as brown algae.
Explanation — Members of Phaeophyceae show great variation in their size and form, ranging from simple filamentous forms to very large and profusely branched kelps.
Variation in size and form: Dictionary meaning — the occurrence of differences in body shape, branching pattern and size among organisms of the same group.
Explanation — Brown algae exhibit considerable diversity in thallus structure, ranging from simple branched filaments to large, complex and profusely branched forms.
Ectocarpus: Dictionary meaning — a genus of brown algae with a simple, branched and filamentous thallus.
Explanation — Ectocarpus represents a relatively simple form of Phaeophyceae and has a branched, filamentous body.
Filamentous form: Dictionary meaning — a body consisting of long, thread-like structures formed by cells arranged in a row or series.
Explanation — Ectocarpus has a filamentous thallus in which the cells form thread-like branched structures.
Kelps: Dictionary meaning — large brown algae belonging mainly to the order Laminariales, often forming extensive underwater forests.
Explanation — Kelps are among the largest algae and have profusely branched or highly developed thalli. Some kelps may reach a height of about 100 metres.
Profusely branched: Dictionary meaning — having numerous or extensively developed branches.
Explanation — Large kelps have highly developed bodies with extensive branching and can form very large underwater structures.
Given Statement - Phaeophyceae show great variation in size and form, ranging from simple branched, filamentous forms such as Ectocarpus to profusely branched kelps that may reach a height of about 100 metres.
Explanation — Members of Phaeophyceae show great variation in their size and form, ranging from simple filamentous forms to very large and profusely branched kelps.
Variation in size and form: Dictionary meaning — the occurrence of differences in body shape, branching pattern and size among organisms of the same group.
Explanation — Brown algae exhibit considerable diversity in thallus structure, ranging from simple branched filaments to large, complex and profusely branched forms.
Ectocarpus: Dictionary meaning — a genus of brown algae with a simple, branched and filamentous thallus.
Explanation — Ectocarpus represents a relatively simple form of Phaeophyceae and has a branched, filamentous body.
Filamentous form: Dictionary meaning — a body consisting of long, thread-like structures formed by cells arranged in a row or series.
Explanation — Ectocarpus has a filamentous thallus in which the cells form thread-like branched structures.
Kelps: Dictionary meaning — large brown algae belonging mainly to the order Laminariales, often forming extensive underwater forests.
Explanation — Kelps are among the largest algae and have profusely branched or highly developed thalli. Some kelps may reach a height of about 100 metres.
Profusely branched: Dictionary meaning — having numerous or extensively developed branches.
Explanation — Large kelps have highly developed bodies with extensive branching and can form very large underwater structures.
Given Statement - Phaeophyceae show great variation in size and form, ranging from simple branched, filamentous forms such as Ectocarpus to profusely branched kelps that may reach a height of about 100 metres.
🎯 Conclusion
Phaeophyceae show great variation in size and form. Ectocarpus represents a simple branched, filamentous form, whereas kelps are large, profusely branched brown algae that may reach about 100 metres in height.
3
Which of the following photosynthetic pigments are present in Phaeophyceae or brown algae?
Practice
A
Chlorophyll a, chlorophyll c, carotenoids and xanthophylls
B
Chlorophyll a, chlorophyll b, phycocyanin and phycoerythrin
C
Chlorophyll b, chlorophyll d, carotenoids and anthocyanins
D
Only chlorophyll a and chlorophyll b
✅ Show Answer
✔ Correct Answer:
A
(Chlorophyll a, chlorophyll c, carotenoids and xanthophylls)
💡 Explanation
Phaeophyceae: Dictionary meaning — a class of algae commonly known as brown algae.
Explanation — Members of Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids and xanthophylls as their photosynthetic pigments. The xanthophyll fucoxanthin gives them their characteristic brown colour.
Chlorophyll a: Dictionary meaning — a primary photosynthetic pigment that absorbs light energy for photosynthesis.
Explanation — Chlorophyll a is present in Phaeophyceae and plays an important role in photosynthesis by capturing light energy.
Chlorophyll c: Dictionary meaning — an accessory chlorophyll pigment found in certain groups of algae.
Explanation — Chlorophyll c occurs in brown algae and functions as an accessory pigment that helps absorb light for photosynthesis.
Carotenoids: Dictionary meaning — yellow, orange or reddish accessory pigments involved in light absorption and protection of photosynthetic cells.
Explanation — Carotenoids are present in Phaeophyceae and contribute to their characteristic pigmentation and photosynthetic activity.
Xanthophylls: Dictionary meaning — a group of yellow accessory carotenoid pigments found in photosynthetic organisms.
Explanation — Xanthophylls are present in brown algae. Fucoxanthin, a characteristic xanthophyll, is mainly responsible for the brown colour of Phaeophyceae.
Fucoxanthin: Dictionary meaning — a brown-coloured xanthophyll pigment characteristic of brown algae.
Explanation — Fucoxanthin masks the green colour of chlorophyll and gives brown algae their characteristic brown or olive-brown appearance.
Given Statement - Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids and xanthophylls.
Explanation — Members of Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids and xanthophylls as their photosynthetic pigments. The xanthophyll fucoxanthin gives them their characteristic brown colour.
Chlorophyll a: Dictionary meaning — a primary photosynthetic pigment that absorbs light energy for photosynthesis.
Explanation — Chlorophyll a is present in Phaeophyceae and plays an important role in photosynthesis by capturing light energy.
Chlorophyll c: Dictionary meaning — an accessory chlorophyll pigment found in certain groups of algae.
Explanation — Chlorophyll c occurs in brown algae and functions as an accessory pigment that helps absorb light for photosynthesis.
Carotenoids: Dictionary meaning — yellow, orange or reddish accessory pigments involved in light absorption and protection of photosynthetic cells.
Explanation — Carotenoids are present in Phaeophyceae and contribute to their characteristic pigmentation and photosynthetic activity.
Xanthophylls: Dictionary meaning — a group of yellow accessory carotenoid pigments found in photosynthetic organisms.
Explanation — Xanthophylls are present in brown algae. Fucoxanthin, a characteristic xanthophyll, is mainly responsible for the brown colour of Phaeophyceae.
Fucoxanthin: Dictionary meaning — a brown-coloured xanthophyll pigment characteristic of brown algae.
Explanation — Fucoxanthin masks the green colour of chlorophyll and gives brown algae their characteristic brown or olive-brown appearance.
Given Statement - Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids and xanthophylls.
🎯 Conclusion
Phaeophyceae possess chlorophyll a, chlorophyll c, carotenoids and xanthophylls. The xanthophyll fucoxanthin is especially important because it contributes to the characteristic brown colour of brown algae.
4
The colour of Phaeophyceae varies from olive green to various shades of brown depending mainly on the amount of which pigment present in them?
Practice
A
Chlorophyll a
B
Chlorophyll c
C
Fucoxanthin
D
Carotene
✅ Show Answer
✔ Correct Answer:
C
(Fucoxanthin)
💡 Explanation
Phaeophyceae: Dictionary meaning — a class of algae commonly known as brown algae.
Explanation — Phaeophyceae vary in colour from olive green to different shades of brown. This variation is mainly due to differences in the amount of the xanthophyll pigment fucoxanthin present in their cells.
Olive green: Dictionary meaning — a green colour with a brownish or yellowish shade.
Explanation — Some members of Phaeophyceae appear olive green when the amount of fucoxanthin is relatively lower and the green colour of chlorophyll is more visible.
Brown colour: Dictionary meaning — a colour produced by the combination of darker yellow, orange or reddish pigments with other pigments.
Explanation — Brown algae show various shades of brown because fucoxanthin is present in different amounts and masks the green colour of chlorophyll to different degrees.
Xanthophyll: Dictionary meaning — a yellow-coloured accessory carotenoid pigment found in photosynthetic organisms.
Explanation — Xanthophylls are accessory pigments that help in light absorption and contribute to the characteristic colour of certain algae.
Fucoxanthin: Dictionary meaning — a characteristic brownish xanthophyll pigment found in brown algae.
Explanation — Fucoxanthin is the major pigment responsible for the brown or olive-brown colour of Phaeophyceae. Differences in its amount cause variations in the colour of different brown algae.
Given Statement - Phaeophyceae vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment fucoxanthin present in them.
Explanation — Phaeophyceae vary in colour from olive green to different shades of brown. This variation is mainly due to differences in the amount of the xanthophyll pigment fucoxanthin present in their cells.
Olive green: Dictionary meaning — a green colour with a brownish or yellowish shade.
Explanation — Some members of Phaeophyceae appear olive green when the amount of fucoxanthin is relatively lower and the green colour of chlorophyll is more visible.
Brown colour: Dictionary meaning — a colour produced by the combination of darker yellow, orange or reddish pigments with other pigments.
Explanation — Brown algae show various shades of brown because fucoxanthin is present in different amounts and masks the green colour of chlorophyll to different degrees.
Xanthophyll: Dictionary meaning — a yellow-coloured accessory carotenoid pigment found in photosynthetic organisms.
Explanation — Xanthophylls are accessory pigments that help in light absorption and contribute to the characteristic colour of certain algae.
Fucoxanthin: Dictionary meaning — a characteristic brownish xanthophyll pigment found in brown algae.
Explanation — Fucoxanthin is the major pigment responsible for the brown or olive-brown colour of Phaeophyceae. Differences in its amount cause variations in the colour of different brown algae.
Given Statement - Phaeophyceae vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment fucoxanthin present in them.
🎯 Conclusion
The colour of Phaeophyceae ranges from olive green to various shades of brown. This variation mainly depends on the amount of the xanthophyll pigment fucoxanthin present in the algae.
5
In what form is food stored in Phaeophyceae or brown algae?
Practice
A
Starch and glycogen
B
Laminarin and mannitol
C
Floridean starch and glycogen
D
Cellulose and chitin
✅ Show Answer
✔ Correct Answer:
B
(Laminarin and mannitol)
💡 Explanation
Phaeophyceae: Dictionary meaning — a class of algae commonly known as brown algae.
Explanation — In Phaeophyceae, food is stored mainly as complex carbohydrates, particularly in the forms of laminarin and mannitol.
Food reserve: Dictionary meaning — substances stored by an organism for use as a source of energy and nutrients when required.
Explanation — Brown algae store the products of photosynthesis as reserve food instead of storing them mainly as ordinary starch.
Complex carbohydrates: Dictionary meaning — carbohydrates made up of larger or more complex molecules, often serving as storage or structural substances.
Explanation — Phaeophyceae store food in the form of complex carbohydrates such as laminarin.
Laminarin: Dictionary meaning — a storage polysaccharide characteristic of brown algae.
Explanation — Laminarin is an important reserve food material in Phaeophyceae and serves as a stored source of energy.
Mannitol: Dictionary meaning — a sugar alcohol that functions as a storage product in brown algae.
Explanation — Mannitol is another important reserve food material found in Phaeophyceae and is associated with carbohydrate storage.
Given Statement - Food in Phaeophyceae is stored as complex carbohydrates, which may be in the form of laminarin or mannitol.
Explanation — In Phaeophyceae, food is stored mainly as complex carbohydrates, particularly in the forms of laminarin and mannitol.
Food reserve: Dictionary meaning — substances stored by an organism for use as a source of energy and nutrients when required.
Explanation — Brown algae store the products of photosynthesis as reserve food instead of storing them mainly as ordinary starch.
Complex carbohydrates: Dictionary meaning — carbohydrates made up of larger or more complex molecules, often serving as storage or structural substances.
Explanation — Phaeophyceae store food in the form of complex carbohydrates such as laminarin.
Laminarin: Dictionary meaning — a storage polysaccharide characteristic of brown algae.
Explanation — Laminarin is an important reserve food material in Phaeophyceae and serves as a stored source of energy.
Mannitol: Dictionary meaning — a sugar alcohol that functions as a storage product in brown algae.
Explanation — Mannitol is another important reserve food material found in Phaeophyceae and is associated with carbohydrate storage.
Given Statement - Food in Phaeophyceae is stored as complex carbohydrates, which may be in the form of laminarin or mannitol.
🎯 Conclusion
Phaeophyceae store their food as complex carbohydrates, mainly in the forms of laminarin and mannitol. These substances act as reserve food materials in brown algae.
6
What is the nature of the cell wall in the vegetative cells of Phaeophyceae?
Practice
A
The cell wall is made only of chitin and lacks any outer coating.
B
The cell wall is made of cellulose and is usually covered externally by a gelatinous coating of algin.
C
The cell wall is made only of pectin and is covered by lignin.
D
The cell wall is absent and the cells are surrounded only by a protein layer.
✅ Show Answer
✔ Correct Answer:
B
(The cell wall is made of cellulose and is usually covered externally by a gelatinous coating of algin.)
💡 Explanation
Vegetative cells: Dictionary meaning — cells of an organism that perform normal growth and body functions rather than directly participating in reproduction.
Explanation — The vegetative cells of Phaeophyceae form the main body or thallus of the brown alga and possess a cellulosic cell wall.
Cell wall: Dictionary meaning — a rigid outer layer surrounding a cell that provides shape, support and protection.
Explanation — In Phaeophyceae, the cell wall of vegetative cells is mainly cellulosic and provides structural support to the thallus.
Cellulose: Dictionary meaning — a complex carbohydrate that forms an important structural component of plant and algal cell walls.
Explanation — Cellulose forms an important part of the cell wall of vegetative cells in brown algae and contributes to their structural strength.
Gelatinous coating: Dictionary meaning — a soft, jelly-like layer covering the surface of a structure.
Explanation — The cellulosic wall of brown algal cells is usually covered externally by a gelatinous coating, which helps protect and support the cells.
Algin: Dictionary meaning — a gelatinous polysaccharide found in the cell walls of brown algae.
Explanation — Algin forms the gelatinous outer coating of the cell wall in Phaeophyceae and is an economically important substance obtained from brown algae.
Given Statement - The vegetative cells of Phaeophyceae have a cellulosic wall that is usually covered on the outside by a gelatinous coating of algin.
Explanation — The vegetative cells of Phaeophyceae form the main body or thallus of the brown alga and possess a cellulosic cell wall.
Cell wall: Dictionary meaning — a rigid outer layer surrounding a cell that provides shape, support and protection.
Explanation — In Phaeophyceae, the cell wall of vegetative cells is mainly cellulosic and provides structural support to the thallus.
Cellulose: Dictionary meaning — a complex carbohydrate that forms an important structural component of plant and algal cell walls.
Explanation — Cellulose forms an important part of the cell wall of vegetative cells in brown algae and contributes to their structural strength.
Gelatinous coating: Dictionary meaning — a soft, jelly-like layer covering the surface of a structure.
Explanation — The cellulosic wall of brown algal cells is usually covered externally by a gelatinous coating, which helps protect and support the cells.
Algin: Dictionary meaning — a gelatinous polysaccharide found in the cell walls of brown algae.
Explanation — Algin forms the gelatinous outer coating of the cell wall in Phaeophyceae and is an economically important substance obtained from brown algae.
Given Statement - The vegetative cells of Phaeophyceae have a cellulosic wall that is usually covered on the outside by a gelatinous coating of algin.
🎯 Conclusion
The vegetative cells of Phaeophyceae possess a cellulosic cell wall, which is usually covered externally by a gelatinous coating of algin. Algin is an important characteristic component of brown algal cell walls.
7
What does the protoplast of the vegetative cells of Phaeophyceae contain in addition to plastids?
Practice
A
A centrally located vacuole and nucleus
B
Only a cell wall and algin
C
Only chlorophyll and carotenoids
D
A large number of small vacuoles and no nucleus
✅ Show Answer
✔ Correct Answer:
A
(A centrally located vacuole and nucleus)
💡 Explanation
Protoplast: Dictionary meaning — the living content of a cell enclosed by the plasma membrane, excluding the cell wall.
Explanation — In Phaeophyceae, the protoplast contains plastids along with a centrally located vacuole and nucleus.
Plastids: Dictionary meaning — membrane-bound cell organelles containing pigments or involved in the synthesis and storage of food materials.
Explanation — The plastids of brown algae contain photosynthetic pigments such as chlorophyll a, chlorophyll c, carotenoids and xanthophylls.
Vacuole: Dictionary meaning — a membrane-bound space within a cell that contains cell sap and helps in storage and maintenance of internal conditions.
Explanation — The protoplast of Phaeophyceae contains a centrally located vacuole.
Nucleus: Dictionary meaning — a membrane-bound organelle that contains the genetic material and controls the activities of the cell.
Explanation — The nucleus is present within the protoplast and contains the genetic material of the brown algal cell.
Centrally located: Dictionary meaning — positioned near or at the centre of a structure.
Explanation — The vacuole described in the vegetative cells of Phaeophyceae is located centrally within the cell.
Given Statement - The protoplast of Phaeophyceae contains plastids, a centrally located vacuole and a nucleus.
Explanation — In Phaeophyceae, the protoplast contains plastids along with a centrally located vacuole and nucleus.
Plastids: Dictionary meaning — membrane-bound cell organelles containing pigments or involved in the synthesis and storage of food materials.
Explanation — The plastids of brown algae contain photosynthetic pigments such as chlorophyll a, chlorophyll c, carotenoids and xanthophylls.
Vacuole: Dictionary meaning — a membrane-bound space within a cell that contains cell sap and helps in storage and maintenance of internal conditions.
Explanation — The protoplast of Phaeophyceae contains a centrally located vacuole.
Nucleus: Dictionary meaning — a membrane-bound organelle that contains the genetic material and controls the activities of the cell.
Explanation — The nucleus is present within the protoplast and contains the genetic material of the brown algal cell.
Centrally located: Dictionary meaning — positioned near or at the centre of a structure.
Explanation — The vacuole described in the vegetative cells of Phaeophyceae is located centrally within the cell.
Given Statement - The protoplast of Phaeophyceae contains plastids, a centrally located vacuole and a nucleus.
🎯 Conclusion
The protoplast of Phaeophyceae contains plastids, a centrally located vacuole and a nucleus. These structures are important components of the living cell.
8
Which of the following correctly describes the plant body of Phaeophyceae?
Practice
A
The plant body is attached by rhizoids and consists only of a leaf-like frond.
B
The plant body is usually attached to the substratum by a holdfast and has a stipe and a leaf-like photosynthetic organ called the frond.
C
The plant body is attached by roots and consists of a stem and true leaves.
D
The plant body is free-floating and lacks any specialized structures.
✅ Show Answer
✔ Correct Answer:
B
(The plant body is usually attached to the substratum by a holdfast and has a stipe and a leaf-like photosynthetic organ called the frond.)
💡 Explanation
Plant body: Dictionary meaning — the main body or thallus of a plant-like organism.
Explanation — The plant body of many Phaeophyceae is differentiated into specialized parts such as the holdfast, stipe and frond.
Substratum: Dictionary meaning — the surface or material to which an organism is attached or on which it grows.
Explanation — Brown algae are usually attached to a suitable substratum such as rocks or other solid surfaces in marine habitats.
Holdfast: Dictionary meaning — a specialized structure that attaches an alga firmly to the substratum.
Explanation — The holdfast anchors the brown algal plant body to the substratum and helps prevent it from being carried away by water movements.
Stipe: Dictionary meaning — a stalk-like structure that supports the frond of an alga.
Explanation — The stipe is the stalk-like portion of the brown algal body that supports and connects the holdfast with the frond.
Frond: Dictionary meaning — a leaf-like photosynthetic structure of an alga.
Explanation — The frond is the leaf-like portion of the brown algal body that performs photosynthesis.
Photosynthetic organ: Dictionary meaning — a structure specialized for carrying out photosynthesis.
Explanation — The frond functions as the main photosynthetic region of the plant body in many brown algae.
Given Statement - The plant body of Phaeophyceae is usually attached to the substratum by a holdfast and has a stalk called the stipe and a leaf-like photosynthetic organ called the frond.
Explanation — The plant body of many Phaeophyceae is differentiated into specialized parts such as the holdfast, stipe and frond.
Substratum: Dictionary meaning — the surface or material to which an organism is attached or on which it grows.
Explanation — Brown algae are usually attached to a suitable substratum such as rocks or other solid surfaces in marine habitats.
Holdfast: Dictionary meaning — a specialized structure that attaches an alga firmly to the substratum.
Explanation — The holdfast anchors the brown algal plant body to the substratum and helps prevent it from being carried away by water movements.
Stipe: Dictionary meaning — a stalk-like structure that supports the frond of an alga.
Explanation — The stipe is the stalk-like portion of the brown algal body that supports and connects the holdfast with the frond.
Frond: Dictionary meaning — a leaf-like photosynthetic structure of an alga.
Explanation — The frond is the leaf-like portion of the brown algal body that performs photosynthesis.
Photosynthetic organ: Dictionary meaning — a structure specialized for carrying out photosynthesis.
Explanation — The frond functions as the main photosynthetic region of the plant body in many brown algae.
Given Statement - The plant body of Phaeophyceae is usually attached to the substratum by a holdfast and has a stalk called the stipe and a leaf-like photosynthetic organ called the frond.
🎯 Conclusion
The plant body of Phaeophyceae is usually differentiated into a holdfast, stipe and frond. The holdfast attaches the alga to the substratum, the stipe provides support, and the frond is the leaf-like photosynthetic region.
9
How does vegetative reproduction take place in Phaeophyceae?
Practice
A
By fragmentation
B
By budding
C
By binary fission
D
By spore formation
✅ Show Answer
✔ Correct Answer:
A
(By fragmentation)
💡 Explanation
Vegetative reproduction: Dictionary meaning — a type of asexual reproduction in which new individuals are produced from vegetative parts of the parent body.
Explanation — In Phaeophyceae, vegetative reproduction takes place mainly by fragmentation, in which a part of the thallus separates from the parent body and develops into a new individual.
Fragmentation: Dictionary meaning — a method of reproduction in which an organism breaks into two or more pieces, with each piece capable of developing into a complete individual.
Explanation — When the thallus of a brown alga breaks into fragments, the separated fragments can grow and develop into new thalli under suitable conditions.
Thallus: Dictionary meaning — the vegetative body of an alga that is not differentiated into true roots, stems and leaves.
Explanation — The thallus forms the main plant body of Phaeophyceae, and its fragments can give rise to new individuals during vegetative reproduction.
Given Statement - Vegetative reproduction in Phaeophyceae takes place by fragmentation.
Explanation — In Phaeophyceae, vegetative reproduction takes place mainly by fragmentation, in which a part of the thallus separates from the parent body and develops into a new individual.
Fragmentation: Dictionary meaning — a method of reproduction in which an organism breaks into two or more pieces, with each piece capable of developing into a complete individual.
Explanation — When the thallus of a brown alga breaks into fragments, the separated fragments can grow and develop into new thalli under suitable conditions.
Thallus: Dictionary meaning — the vegetative body of an alga that is not differentiated into true roots, stems and leaves.
Explanation — The thallus forms the main plant body of Phaeophyceae, and its fragments can give rise to new individuals during vegetative reproduction.
Given Statement - Vegetative reproduction in Phaeophyceae takes place by fragmentation.
🎯 Conclusion
Vegetative reproduction in Phaeophyceae takes place by fragmentation. The separated fragments of the thallus can grow into new individuals under suitable conditions.
10
Which of the following correctly describes asexual reproduction in most brown algae?
Practice
A
It takes place by non-motile spores that have no flagella.
B
It takes place by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella.
C
It takes place only by fragmentation of the thallus.
D
It takes place by spherical spores having four equal flagella.
✅ Show Answer
✔ Correct Answer:
B
(It takes place by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella.)
💡 Explanation
Asexual reproduction: Dictionary meaning — reproduction in which new individuals are produced without the fusion of male and female gametes.
Explanation — In most brown algae, asexual reproduction occurs through zoospores. These zoospores are motile and can swim using their flagella.
Zoospore: Dictionary meaning — a motile asexual reproductive cell that moves with the help of flagella.
Explanation — The zoospores of most brown algae are biflagellate, meaning they possess two flagella that help them move through water.
Biflagellate: Dictionary meaning — having two flagella.
Explanation — Brown algal zoospores are biflagellate because they possess two flagella used for locomotion.
Pear-shaped: Dictionary meaning — having a body shape resembling a pear, with one end broader than the other.
Explanation — The zoospores of most brown algae are pear-shaped, which is one of their characteristic structural features.
Flagella: Dictionary meaning — long, slender, whip-like structures used by certain cells for movement.
Explanation — The two flagella of brown algal zoospores help them move through the surrounding water.
Unequal flagella: Dictionary meaning — two flagella that differ in their length or structure.
Explanation — The two flagella of brown algal zoospores are unequal in size and are attached laterally to the zoospore.
Laterally attached: Dictionary meaning — attached to the side of a cell or structure.
Explanation — The two unequal flagella of brown algal zoospores are attached to the lateral or side region of the pear-shaped zoospore.
Given Statement - Asexual reproduction in most brown algae occurs by biflagellate zoospores that are pear-shaped and possess two unequal, laterally attached flagella.
Explanation — In most brown algae, asexual reproduction occurs through zoospores. These zoospores are motile and can swim using their flagella.
Zoospore: Dictionary meaning — a motile asexual reproductive cell that moves with the help of flagella.
Explanation — The zoospores of most brown algae are biflagellate, meaning they possess two flagella that help them move through water.
Biflagellate: Dictionary meaning — having two flagella.
Explanation — Brown algal zoospores are biflagellate because they possess two flagella used for locomotion.
Pear-shaped: Dictionary meaning — having a body shape resembling a pear, with one end broader than the other.
Explanation — The zoospores of most brown algae are pear-shaped, which is one of their characteristic structural features.
Flagella: Dictionary meaning — long, slender, whip-like structures used by certain cells for movement.
Explanation — The two flagella of brown algal zoospores help them move through the surrounding water.
Unequal flagella: Dictionary meaning — two flagella that differ in their length or structure.
Explanation — The two flagella of brown algal zoospores are unequal in size and are attached laterally to the zoospore.
Laterally attached: Dictionary meaning — attached to the side of a cell or structure.
Explanation — The two unequal flagella of brown algal zoospores are attached to the lateral or side region of the pear-shaped zoospore.
Given Statement - Asexual reproduction in most brown algae occurs by biflagellate zoospores that are pear-shaped and possess two unequal, laterally attached flagella.
🎯 Conclusion
Asexual reproduction in most brown algae occurs by biflagellate zoospores. These zoospores are pear-shaped and possess two unequal flagella that are attached laterally and help in movement.