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1. Why is biological classification considered essential for studying the diversity of living organisms?
ⓐ. It organizes organisms into groups that aid identification, study, and prediction of characteristics.
ⓑ. It ensures all organisms have identical body plans for easier comparison.
ⓒ. It removes the need for scientific names by using only local names.
ⓓ. It prevents evolutionary changes by keeping organisms in fixed categories.
Correct Answer: It organizes organisms into groups that aid identification, study, and prediction of characteristics.
Explanation: Classification arranges the vast diversity of organisms into manageable groups based on shared characteristics, which makes study and comparison systematic. It provides a standard framework for identification and avoids confusion in naming and communication. Grouping also helps in understanding patterns of similarities and differences across organisms. Once an organism is placed in a group, many of its features can often be inferred from the typical traits of that group. This supports organized learning of biodiversity and relationships. Therefore, classification is a core tool for understanding living organisms.
2. While classifying organisms into major groups, which criterion is most fundamental at the cellular level?
ⓐ. Presence or absence of locomotion
ⓑ. Type of habitat (aquatic or terrestrial)
ⓒ. Presence or absence of a membrane-bound nucleus and organelles
ⓓ. Body size and life span
Correct Answer: Presence or absence of a membrane-bound nucleus and organelles
Explanation: Cell structure is a primary basis of classification because it separates organisms into prokaryotes and eukaryotes at the most fundamental level. A membrane-bound nucleus and organelles indicate compartmentalized cellular organization, which supports higher complexity and specialized functions. In contrast, absence of these structures reflects a prokaryotic plan with different genetic control and cellular machinery. This distinction influences metabolism, reproduction, and overall organization. Because it is deeply conserved and stable across life forms, it is highly reliable for major grouping. Hence, presence or absence of a membrane-bound nucleus and organelles is the key criterion.
3. In the context of “basis of classification,” what does “body organization” primarily refer to?
ⓐ. The color and external appearance of the organism
ⓑ. The geographic region where the organism is found
ⓒ. The total number of cells present in the organism
ⓓ. The level of structural complexity (unicellular, tissue level, organ level, organ-system level)
Correct Answer: The level of structural complexity (unicellular, tissue level, organ level, organ-system level)
Explanation: Body organization refers to how cells are arranged and coordinated to form higher structural units in an organism. Some organisms remain unicellular, while others show division of labour through tissues, organs, and organ systems. As organization increases, specialization and functional efficiency generally increase as well. This criterion is helpful because it reflects fundamental structural plans and evolutionary complexity. It allows broad separation of major groups based on how their bodies are built and function. Therefore, “body organization” focuses on the level of structural complexity.
4. Why is “mode of nutrition” a useful basis for classification?
ⓐ. It always remains identical in all life stages of an organism
ⓑ. It reflects how an organism obtains carbon and energy, indicating major functional differences
ⓒ. It depends only on body size and not on cell structure
ⓓ. It is unrelated to the ecological role of organisms
Correct Answer: It reflects how an organism obtains carbon and energy, indicating major functional differences
Explanation: Mode of nutrition describes how an organism acquires energy and carbon to build biomolecules, so it reveals major functional differences among groups. Autotrophs synthesize organic compounds from inorganic sources, whereas heterotrophs depend on pre-formed organic matter. This difference reflects distinct metabolic pathways and levels of dependence on other organisms. It also connects directly to ecological roles such as producer, consumer, or decomposer in ecosystems. Because it is a stable and meaningful functional trait, it supports reliable grouping. Hence, mode of nutrition is an important basis for classification.
5. Which statement best represents the use of reproduction as a basis for classification, especially in plants?
ⓐ. Organisms are classified only by whether they are oviparous or viviparous
ⓑ. Reproduction is ignored because it varies too much within groups
ⓒ. Life-cycle pattern such as alternation between haploid and diploid phases helps classify plant groups
ⓓ. Only the number of offspring produced is used to classify organisms
Correct Answer: Life-cycle pattern such as alternation between haploid and diploid phases helps classify plant groups
Explanation: Reproductive features are often conserved and provide strong clues about evolutionary relationships and life-cycle strategies. In plants, alternation between haploid gametophyte and diploid sporophyte is a central theme, and the dominance or dependence of these phases differs across groups. Such differences reflect major evolutionary transitions in reproduction, dispersal, and development. Because these patterns are consistent within large plant groups, they become powerful criteria for classification. This is why life-cycle traits are commonly tested in plant diversity questions. Therefore, alternation of generations and related reproductive patterns help classify plant groups.
6. What is the main goal of a phylogenetic system of classification?
ⓐ. To reflect evolutionary history and common ancestry among organisms
ⓑ. To classify organisms only by habitat and geographical distribution
ⓒ. To group organisms using only one easily observable character
ⓓ. To avoid using genetic and fossil evidence in classification
Correct Answer: To reflect evolutionary history and common ancestry among organisms
Explanation: Phylogenetic classification aims to organize organisms according to their evolutionary history and shared ancestry. It focuses on descent with modification and branching relationships, rather than only superficial similarity. This approach uses multiple lines of evidence, including morphology, anatomy, development, and molecular data. Groups formed under this system are expected to represent natural evolutionary lineages. It also helps explain why organisms share certain traits—because they inherited them from common ancestors. Thus, the main goal is to reflect evolutionary relationships.
7. What is a major limitation of an artificial classification system based on a few superficial traits?
ⓐ. It always requires molecular data to be applied
ⓑ. It cannot be used for identifying organisms
ⓒ. It makes classification impossible for microscopic organisms
ⓓ. It may group unrelated organisms together due to similar-looking traits not based on ancestry
Correct Answer: It may group unrelated organisms together due to similar-looking traits not based on ancestry
Explanation: Artificial classification relies on a limited number of easily observable characters, which can sometimes be misleading. Unrelated organisms may independently evolve similar traits due to similar environmental pressures, a phenomenon that does not indicate common ancestry. When classification depends on such superficial similarities, it can incorrectly group unrelated organisms together. This reduces its value for understanding natural relationships and evolutionary history. It may still help with basic identification, but it does not reliably represent true relatedness. Hence, the key limitation is grouping unrelated organisms due to superficial similarity.
8. Why is “species” generally considered the basic unit of classification?
ⓐ. It is the largest category that includes all living organisms
ⓑ. It is the most specific natural grouping used as the starting point for building higher taxa
ⓒ. It is based only on the habitat where organisms are found
ⓓ. It changes daily with environmental conditions
Correct Answer: It is the most specific natural grouping used as the starting point for building higher taxa
Explanation: Classification proceeds from the most specific groups upward to broader categories, and species is the most specific commonly used taxonomic unit. It represents a natural grouping of organisms that share fundamental similarities and show evolutionary cohesion as a unit. Higher categories like genus and family are constructed by grouping related species based on shared traits and relationships. This makes species the foundational reference point on which the taxonomic hierarchy is built. It also supports accurate identification and meaningful comparison across organisms. Therefore, species is considered the basic unit of classification.
9. Which feature most strongly distinguishes a natural classification system from an artificial one?
ⓐ. It considers many characters together to reflect overall similarities and relationships
ⓑ. It uses only one trait such as leaf shape or body color
ⓒ. It ignores internal structure and development
ⓓ. It avoids grouping organisms into hierarchical categories
Correct Answer: It considers many characters together to reflect overall similarities and relationships
Explanation: Natural classification considers a wide range of characters together, including external morphology, internal anatomy, development, and other stable traits. Using multiple characters reduces the chance of error caused by misleading superficial similarities. This approach provides a more complete picture of overall similarity among organisms and tends to align better with true biological relationships. It also supports meaningful grouping that can be used to infer shared features within a group. Therefore, considering many characters together is the key feature distinguishing natural classification from artificial classification.
10. An organism with cellulose cell wall and chloroplasts would most directly support classification into which broad group?
ⓐ. Protozoa
ⓑ. Animalia
ⓒ. Plantae
ⓓ. Viruses
Correct Answer: Plantae
Explanation: A cellulose cell wall is a typical structural feature of plant cells, providing rigidity and support. Chloroplasts indicate the presence of photosynthetic machinery, enabling autotrophic nutrition through photosynthesis. Together, these features reflect the characteristic organization and function of plant cells among eukaryotes. Such cellular characters are stable and widely used to define broad groups in classification. Therefore, an organism showing both cellulose cell wall and chloroplasts is most directly placed in Plantae.
11. Which statement best defines vascular tissue in the context of plant classification?
ⓐ. A tissue system that performs photosynthesis and transpiration only
ⓑ. A conducting system made of xylem and phloem for transport of water/minerals and food
ⓒ. A protective outer covering made only of cork cells
ⓓ. A reproductive tissue that produces spores and gametes
Correct Answer: A conducting system made of xylem and phloem for transport of water/minerals and food
Explanation: Vascular tissue refers to specialized conducting tissues that transport materials within the plant body. Xylem mainly conducts water and minerals from roots to aerial parts, while phloem transports organic food from photosynthetic regions to growing or storage regions. This internal transport system supports larger size and efficient distribution of resources. Because it marks a major structural and functional advance in land plants, its presence or absence is a key criterion for classifying major plant groups. Therefore, vascular tissue is correctly defined as the xylem–phloem conducting system.
12. The absence of vascular tissue is a characteristic feature of which major plant group?
ⓐ. Bryophytes
ⓑ. Pteridophytes
ⓒ. Gymnosperms
ⓓ. Angiosperms
Correct Answer: Bryophytes
Explanation: Bryophytes lack true vascular tissues such as xylem and phloem, so they depend largely on diffusion and short-distance movement of water and nutrients. This limitation keeps them small and strongly tied to moist environments where external water films are available. Their dependence on water is also closely linked to their reproductive processes and habitat preference. The absence of vascular tissue is a fundamental feature that separates bryophytes from higher vascular plants. Hence, bryophytes are characterized by the absence of vascular tissue.
13. Why are vascular tissues considered an evolutionary advancement in land plants?
ⓐ. They completely eliminate the need for water in reproduction
ⓑ. They allow efficient transport, supporting greater height and better adaptation to terrestrial life
ⓒ. They ensure plants reproduce only by seeds
ⓓ. They make plants exclusively parasitic in nutrition
Correct Answer: They allow efficient transport, supporting greater height and better adaptation to terrestrial life
Explanation: Vascular tissues create an efficient internal transport network for water, minerals, and food, allowing plants to supply distant parts of the body effectively. This supports increased size, upright growth, and the development of more complex organs. Efficient internal transport also reduces reliance on constant surface moisture for moving substances within the plant. As a result, vascular plants can occupy a wider range of terrestrial habitats and compete more effectively for light and space. This innovation represents a major step in land plant evolution. Therefore, vascular tissues are considered an important evolutionary advancement.
14. Which plant body feature is most directly enabled by the presence of vascular tissue?
ⓐ. Formation of true roots, stems, and leaves with efficient conduction
ⓑ. Formation of chlorophyll in all cells
ⓒ. Production of flowers and fruits
ⓓ. Ability to live only in water
Correct Answer: Formation of true roots, stems, and leaves with efficient conduction
Explanation: Vascular tissue enables long-distance transport of water and nutrients, which supports the development of true roots, stems, and leaves as specialized organs. Roots can absorb water and minerals and deliver them upward through xylem, stems provide support and serve as main conduits, and leaves can receive water and export food through vascular bundles. These structures function efficiently because conducting tissues connect them into an integrated body plan. This level of organ differentiation is a key feature of vascular plants. Hence, vascular tissue directly enables formation of true roots, stems, and leaves.
15. In bryophytes, the main reason for restricted size is primarily due to:
ⓐ. Absence of chloroplasts
ⓑ. Absence of vascular tissue for long-distance transport
ⓒ. Absence of cell walls
ⓓ. Absence of alternation of generations
Correct Answer: Absence of vascular tissue for long-distance transport
Explanation: Bryophytes do not possess xylem and phloem, so they cannot transport water and nutrients efficiently over long distances. Instead, movement occurs largely through diffusion and short-range cell-to-cell conduction, which becomes ineffective as body size increases. This directly limits their height and thickness and keeps them as small, low-growing forms like mats and cushions. Their size restriction is therefore strongly tied to the lack of vascular tissues. This also contributes to their preference for moist habitats where external water is readily available. Hence, absence of vascular tissue is the primary reason for restricted size.
16. Which of the following correctly classifies plants based on presence of vascular tissue?
ⓐ. Bryophytes: vascular; Pteridophytes: non-vascular
ⓑ. Gymnosperms: non-vascular; Angiosperms: non-vascular
ⓒ. Bryophytes: non-vascular; Pteridophytes: vascular
ⓓ. All plant groups are non-vascular
Correct Answer: Bryophytes: non-vascular; Pteridophytes: vascular
Explanation: Bryophytes are classified as non-vascular because they lack specialized conducting tissues (xylem and phloem). Pteridophytes are classified as vascular plants because they possess well-developed xylem and phloem. This distinction reflects a major evolutionary step that supports increased size, true organ development, and improved adaptation to terrestrial habitats. It is a central criterion for separating non-vascular plants from vascular plants in plant kingdom classification. Therefore, the correct classification is bryophytes as non-vascular and pteridophytes as vascular.
17. Which statement best explains why vascular plants can colonize drier habitats more effectively than non-vascular plants?
ⓐ. Vascular plants do not require sunlight for photosynthesis
ⓑ. Non-vascular plants always produce seeds, which need water to germinate
ⓒ. Vascular plants lack stomata and therefore do not lose water
ⓓ. Vascular plants transport water internally, reducing dependence on constant surface moisture
Correct Answer: Vascular plants transport water internally, reducing dependence on constant surface moisture
Explanation: Vascular plants have xylem that transports water from roots to stems and leaves, allowing internal distribution even when external surfaces are not continuously wet. This reduces dependence on surface water films for movement of substances and supports survival in comparatively drier habitats. Internal transport also helps maintain leaf function and photosynthesis under variable moisture conditions. In contrast, non-vascular plants depend more heavily on external moisture for transport and sustained activity. This is why non-vascular plants are typically confined to moist environments. Therefore, internal water transport enables vascular plants to colonize drier habitats more effectively.
18. The first true vascular plants among land plants are represented by:
ⓐ. Algae
ⓑ. Bryophytes
ⓒ. Pteridophytes
ⓓ. Fungi
Correct Answer: Pteridophytes
Explanation: Pteridophytes are the earliest land plant group in which true vascular tissues appear, enabling efficient conduction of water and food. They also show true roots, stems, and leaves supported by vascular bundles, marking a clear shift from simpler non-vascular plants. This vascular organization allows larger body size and improved terrestrial adaptation. Because algae and bryophytes lack true vascular tissues, they do not represent the first vascular land plants. Therefore, pteridophytes are recognized as the first true vascular plants.
19. In plant classification, presence of vascular tissue most directly separates:
ⓐ. Thallophytes from bryophytes
ⓑ. Algae from fungi
ⓒ. Gymnosperms from angiosperms
ⓓ. Bryophytes from pteridophytes
Correct Answer: Bryophytes from pteridophytes
Explanation: Bryophytes are non-vascular plants that lack xylem and phloem, whereas pteridophytes are vascular plants with well-developed conducting tissues. This difference leads to major changes in size, organ differentiation, and terrestrial adaptation. It forms a clear boundary between the non-vascular and vascular plant groups in standard classification. Other separations, such as between gymnosperms and angiosperms, depend more on seeds, flowers, and fruit-related features rather than the presence of vascular tissue itself. Hence, vascular tissue most directly separates bryophytes from pteridophytes.
20. Which outcome is most directly linked to the evolution of vascular tissue in plants?
ⓐ. Shift from sporophyte dominance to gametophyte dominance
ⓑ. Ability to produce motile sperm in all plant groups
ⓒ. Development of efficient transport and support systems enabling upright growth
ⓓ. Loss of alternation of generations in land plants
Correct Answer: Development of efficient transport and support systems enabling upright growth
Explanation: The evolution of vascular tissue provided plants with an internal system for long-distance transport of water, minerals, and food, along with improved mechanical support through associated tissues. This enabled upright growth, greater plant height, and increased structural complexity. With better conduction and support, plants could expand into new terrestrial habitats and compete more effectively for light. These changes are direct outcomes of vascular tissue evolution and are central to understanding major transitions in plant evolution. Therefore, efficient transport and support enabling upright growth is the key linked outcome.
21. In the plant kingdom, the presence of seeds is the most direct criterion to separate which two major groups?
ⓐ. Algae and bryophytes
ⓑ. Bryophytes and pteridophytes
ⓒ. Pteridophytes and bryophytes
ⓓ. Pteridophytes and spermatophytes (gymnosperms + angiosperms)
Correct Answer: Pteridophytes and spermatophytes (gymnosperms + angiosperms)
Explanation: Seeds are a defining feature of spermatophytes (seed plants), which include gymnosperms and angiosperms. Pteridophytes are vascular but seedless plants, reproducing by spores instead of seeds. This seed-based separation is conceptually strong because a seed contains an embryo, stored food, and a protective coat. These features improve survival, dispersal, and establishment on land. Therefore, seed presence clearly marks the transition from seedless vascular plants to seed-bearing plants in classification.
22. Which statement best represents the concept of a “seed” as an evolutionary advantage in plants?
ⓐ. Seed is always formed without fertilization in all plants
ⓑ. Seed is a single-celled reproductive unit like a spore
ⓒ. Seed formation occurs only in bryophytes due to water dependence
ⓓ. Seed is a fertilized ovule containing an embryo with protective and nutritive support
Correct Answer: Seed is a fertilized ovule containing an embryo with protective and nutritive support
Explanation: A seed is formed after fertilization and develops from the ovule, carrying a young embryo plant inside. It typically includes protective coverings and stored food or nutritive tissue to support early growth. This package allows the plant to survive unfavorable conditions through dormancy. It also enhances dispersal to new habitats compared with delicate gametophytes. These advantages are key reasons seed habit is considered a major evolutionary step in land plants.
23. Which group is correctly identified as vascular but seedless, based on the “presence/absence of seeds” criterion?
ⓐ. Pteridophytes
ⓑ. Angiosperms
ⓒ. Bryophytes
ⓓ. Gymnosperms
Correct Answer: Pteridophytes
Explanation: Pteridophytes have vascular tissues and well-differentiated plant body with roots, stems, and leaves, but they do not form seeds. Their reproduction depends on spores, and fertilization still typically requires water for the motile male gametes. Because seeds are absent, they are grouped as seedless vascular plants. This distinction is central in classification of plant groups. Hence, pteridophytes are vascular yet seedless.
24. Which combination is correct regarding seed presence in major plant groups?
ⓐ. Bryophytes: present; Pteridophytes: present; Gymnosperms: absent; Angiosperms: absent
ⓑ. Bryophytes: absent; Pteridophytes: present; Gymnosperms: absent; Angiosperms: present
ⓒ. Bryophytes: absent; Pteridophytes: absent; Gymnosperms: present; Angiosperms: present
ⓓ. Bryophytes: present; Pteridophytes: absent; Gymnosperms: present; Angiosperms: absent
Correct Answer: Bryophytes: absent; Pteridophytes: absent; Gymnosperms: present; Angiosperms: present
Explanation: Seeds are absent in bryophytes and pteridophytes, which reproduce through spores and do not produce a seed-embedded embryo. Gymnosperms and angiosperms are seed plants (spermatophytes), where seeds develop after fertilization. The seed protects the embryo and helps it survive adverse conditions. This seed habit is strongly linked with better terrestrial adaptation. Therefore, the correct pattern is seeds absent in bryophytes and pteridophytes, but present in gymnosperms and angiosperms.
25. Which feature is most specifically associated with seed-bearing plants compared with seedless plants?
ⓐ. Dominant gametophyte generation in the life cycle
ⓑ. Reproduction only by fragmentation
ⓒ. Absence of pollen grains in reproduction
ⓓ. Formation of an embryo that remains protected and nourished within a seed
Correct Answer: Formation of an embryo that remains protected and nourished within a seed
Explanation: Seed plants develop an embryo after fertilization and retain it within a protective seed coat. The seed also provides nutritive support that helps the embryo establish as a seedling. This allows survival during unfavorable seasons through dormancy. It improves dispersal over long distances and increases chances of successful colonization. These advantages are not achieved to the same extent in spore-based seedless plants. Hence, protected and nourished embryo within a seed is a key seed-plant feature.
26. Why is heterospory considered an important step toward the evolution of the seed habit?
ⓐ. It ensures all spores are identical in size and function
ⓑ. It produces microspores and megaspores, promoting development and retention of the female gametophyte
ⓒ. It converts spore formation directly into fruit formation
ⓓ. It eliminates the need for meiosis in plants
Correct Answer: It produces microspores and megaspores, promoting development and retention of the female gametophyte
Explanation: Heterospory produces two kinds of spores: microspores (male) and megaspores (female), leading to separate male and female gametophytes. The female gametophyte can develop within the megaspore, offering protection and a controlled environment. Retention of the megaspore and female gametophyte inside the parent sporophyte is a crucial trend toward seed formation. This setup supports nourishment and protection of the developing embryo after fertilization. Therefore, heterospory is viewed as a significant evolutionary step toward seed habit.
27. Which plant examples best represent heterosporous pteridophytes showing tendencies toward seed habit?
ⓐ. Selaginella and Salvinia
ⓑ. Chlamydomonas and Spirogyra
ⓒ. Pteris and Dryopteris
ⓓ. Funaria and Marchantia
Correct Answer: Selaginella and Salvinia
Explanation: Selaginella and Salvinia are classic examples of heterosporous pteridophytes producing microspores and megaspores. This condition supports separate male and female gametophytes and promotes internal development of the female gametophyte. Such trends reduce vulnerability compared with free-living gametophytes. These features are considered evolutionary steps toward seed habit, even though true seeds are not formed in pteridophytes. Hence, Selaginella and Salvinia best represent this seed-habit tendency.
28. Which statement correctly contrasts a spore with a seed in terms of plant classification?
ⓐ. Spores always contain a multicellular embryo, while seeds do not
ⓑ. Seeds are produced by all pteridophytes, while spores are produced by all angiosperms
ⓒ. Spores are formed only after double fertilization, while seeds are formed without fertilization
ⓓ. Seeds contain an embryo with protective and nutritive support, while spores are generally single-celled dispersal units
Correct Answer: Seeds contain an embryo with protective and nutritive support, while spores are generally single-celled dispersal units
Explanation: A spore is typically a single-celled reproductive/dispersal unit that can germinate into a gametophyte or new plant stage depending on the group. A seed, in contrast, contains a developed embryo formed after fertilization, along with protection and stored nourishment. This makes seeds more resilient, allowing dormancy and better survival during unfavorable conditions. Seeds also improve the efficiency of reproduction on land by protecting early development. Therefore, embryo-bearing protected units define seeds, while spores are simpler dispersal units.
29. Which statement best explains how seed formation reduces dependence on water compared with seedless plants?
ⓐ. Seeds directly swim to new habitats using flagella
ⓑ. Seed plants completely stop using fertilization
ⓒ. Seed plants use pollen and protected embryo development, reducing the need for external water films
ⓓ. Seeds develop only in aquatic environments, so water dependence is reduced
Correct Answer: Seed plants use pollen and protected embryo development, reducing the need for external water films
Explanation: Seed plants commonly transfer male gametes via pollen, which does not require a film of water for reaching the female gametophyte. Fertilization and embryo development occur in protected structures, limiting exposure to external conditions. The resulting seed further protects the embryo and supports it nutritionally. These adaptations collectively reduce the reproductive dependence on free water seen in many seedless groups. This is a major reason seed plants dominate diverse terrestrial habitats. Hence, pollen-mediated transfer and protected embryo development reduce water dependence.
30. Based on seed presence, which is the most appropriate grouping of gymnosperms and angiosperms in plant classification?
ⓐ. Thallophytes
ⓑ. Bryophytes
ⓒ. Pteridophytes
ⓓ. Spermatophytes (phanerogams)
Correct Answer: Spermatophytes (phanerogams)
Explanation: Gymnosperms and angiosperms are both seed-bearing plants, and NCERT groups them under spermatophytes (also called phanerogams). Their defining feature is seed formation after fertilization, ensuring embryo protection and nourishment. This trait differentiates them sharply from bryophytes and pteridophytes, which are seedless. The seed habit supports successful reproduction and dispersal on land. Therefore, the correct seed-based grouping for gymnosperms and angiosperms is spermatophytes (phanerogams).
31. In plant classification, the presence of flowers is a defining feature of which group?
ⓐ. Bryophytes
ⓑ. Angiosperms
ⓒ. Pteridophytes
ⓓ. Gymnosperms
Correct Answer: Angiosperms
Explanation: Flowers are specialized reproductive structures that bear stamens and carpels, enabling efficient pollination and fertilization. This feature is characteristic of angiosperms and is used as a major classification criterion to separate them from other plant groups. In angiosperms, ovules are enclosed within the ovary, and the flower is the organ where sexual reproduction is organized. The presence of flowers is therefore directly linked to the angiosperm reproductive strategy and their wide adaptive success on land.
32. Which statement correctly describes gymnosperms with respect to flowers?
ⓐ. Gymnosperms produce true flowers with ovary and stigma
ⓑ. Gymnosperms show double fertilization inside the flower
ⓒ. Gymnosperms form fruits from the ovary after flowering
ⓓ. Gymnosperms do not have true flowers; they bear reproductive structures in cones (strobili)
Correct Answer: Gymnosperms do not have true flowers; they bear reproductive structures in cones (strobili)
Explanation: Gymnosperms are seed plants but they do not produce true flowers with an ovary enclosing ovules. Instead, they bear male and female reproductive structures typically arranged in cones (strobili). These cones produce pollen and ovules, enabling seed formation without the floral organization seen in angiosperms. This distinction is important in classification because it separates seed plants into flowering (angiosperms) and non-flowering (gymnosperms) lineages.
33. The most accurate definition of a “flower” in terms of plant reproduction is:
ⓐ. A modified shoot bearing specialized reproductive leaves (stamens and carpels)
ⓑ. A spore-producing structure found in all vascular plants
ⓒ. A vegetative bud that forms only leaves
ⓓ. A root structure that absorbs water for reproduction
Correct Answer: A modified shoot bearing specialized reproductive leaves (stamens and carpels)
Explanation: A flower is understood as a modified shoot in which the apical meristem forms specialized reproductive structures rather than only vegetative leaves. Stamens (male) and carpels (female) are considered modified leaves (sporophylls) arranged on a condensed axis, often with accessory whorls like sepals and petals. This organization concentrates reproduction, promotes pollination, and supports fertilization in a protected setting. Hence, the flower is a key reproductive innovation used in classification of flowering plants.
34. Which feature is most directly responsible for fruit formation and is therefore closely linked with flowering plants?
ⓐ. Presence of rhizoids
ⓑ. Dominant gametophyte generation
ⓒ. Presence of an ovary that encloses ovules
ⓓ. Presence of vascular tissue only
Correct Answer: Presence of an ovary that encloses ovules
Explanation: In flowering plants, ovules are enclosed within the ovary, which is a defining floral structure. After fertilization, the ovary develops into a fruit while the ovules develop into seeds. This enclosure provides protection to developing ovules and later helps in seed dispersal through fruit formation. Because gymnosperms lack an ovary, they do not form fruits in the same way. Therefore, the ovary enclosing ovules is the key feature tightly associated with flowers and fruit formation.
35. Which reproductive event is uniquely associated with flowering plants and occurs within the flower?
ⓐ. Conjugation
ⓑ. Fragmentation
ⓒ. Sporulation by sporangia on fronds
ⓓ. Double fertilization
Correct Answer: Double fertilization
Explanation: Double fertilization is a characteristic feature of angiosperms and takes place within the flower, inside the ovule. One male gamete fuses with the egg to form the zygote, while the other fuses with the polar nuclei to form endosperm. This process links embryo formation with the development of a nutritive tissue that supports the embryo. The flower provides the structural setting for pollen delivery, fertilization, and subsequent seed development. Hence, double fertilization is uniquely associated with flowering plants.
36. In classification, “non-flowering seed plants” refers to:
ⓐ. Algae
ⓑ. Gymnosperms
ⓒ. Bryophytes
ⓓ. Pteridophytes
Correct Answer: Gymnosperms
Explanation: Gymnosperms produce seeds but do not form true flowers; their reproductive organs are typically organized in cones. Since they are seed-bearing yet lack flowers, they are described as non-flowering seed plants. This distinction is important because seed plants are divided into gymnosperms (seeds without flowers and without fruits) and angiosperms (seeds produced within flowers and enclosed in fruits). Therefore, the term “non-flowering seed plants” aligns with gymnosperms.
37. Which statement best explains why flowers are considered an advanced feature in land-plant evolution?
ⓐ. Flowers ensure plants remain dependent on water for fertilization
ⓑ. Flowers prevent seed formation and promote only vegetative reproduction
ⓒ. Flowers promote efficient pollination and protect reproductive processes, increasing reproductive success
ⓓ. Flowers occur in all plant groups from algae to angiosperms
Correct Answer: Flowers promote efficient pollination and protect reproductive processes, increasing reproductive success
Explanation: Flowers improve reproductive efficiency by structuring the processes of pollen transfer, fertilization, and early seed development in a protected, specialized organ. They often attract pollinators and enhance targeted pollen delivery, which increases the chances of successful fertilization. Floral structures also protect the ovules and later support seed formation within enclosed tissues. These advantages reduce reproductive uncertainty and enhance adaptation to diverse terrestrial habitats. Hence, flowers are considered an advanced evolutionary feature.
38. Which term correctly identifies plants that bear flowers?
ⓐ. Angiosperms
ⓑ. Pteridophytes
ⓒ. Bryophytes
ⓓ. Thallophytes
Correct Answer: Angiosperms
Explanation: Angiosperms are defined by the presence of flowers as their reproductive organs. Flowers bear stamens and carpels, and ovules are enclosed within an ovary, leading to fruit formation after fertilization. This floral organization is used as a major classification criterion to identify flowering plants distinctly from gymnosperms and spore-producing groups. Because flowers are a consistent, defining trait, they provide a clear boundary in plant classification. Therefore, flowering plants are correctly identified as angiosperms.
39. A botanist finds a plant that produces seeds but has no flowers and forms no fruits. It should be classified as:
ⓐ. Bryophyte
ⓑ. Pteridophyte
ⓒ. Angiosperm
ⓓ. Gymnosperm
Correct Answer: Gymnosperm
Explanation: Seed production indicates the plant belongs to seed plants, but absence of flowers and fruits rules out angiosperms. In gymnosperms, seeds develop without floral structures and are not enclosed in an ovary, so fruit formation does not occur. Their reproductive organs are typically cones, and ovules are exposed (“naked”) relative to angiosperms. This combination of seed presence with absence of flowers and fruits is a classic classification indicator for gymnosperms.
40. Which character combination best supports classification of a plant as a flowering plant?
ⓐ. Presence of flowers and ovules enclosed within an ovary
ⓑ. Presence of rhizoids and thallus body
ⓒ. Presence of motile sperm and dependence on water for fertilization
ⓓ. Presence of spores as the only reproductive unit
Correct Answer: Presence of flowers and ovules enclosed within an ovary
Explanation: Flowering plants are identified by flowers as reproductive organs and by ovules enclosed within an ovary, which later develops into a fruit. This enclosure and floral organization are defining criteria used to separate angiosperms from other plant groups. The flower integrates pollination, fertilization, and early seed development in a specialized structure. These traits collectively support efficient sexual reproduction and wide ecological success. Hence, flowers along with an ovary enclosing ovules best indicate a flowering plant.
41. In bryophytes, which phase is dominant and independent, forming the main plant body?
ⓐ. Sporophyte
ⓑ. Gametophyte
ⓒ. Zygote
ⓓ. Embryo sac
Correct Answer: Gametophyte
Explanation: In bryophytes, the gametophyte is the dominant, photosynthetic, free-living phase that forms the main plant body. The sporophyte remains attached to the gametophyte and is nutritionally dependent on it. This dominance pattern is a key basis for classification because it reflects how the life cycle is organized. The bryophyte gametophyte bears sex organs and produces gametes, which after fertilization give rise to the sporophyte. Thus, bryophytes are correctly characterized by dominant gametophyte generation.
42. Which statement correctly describes the sporophyte in bryophytes?
ⓐ. It is the dominant, long-lived, free-living plant body.
ⓑ. It is absent because bryophytes reproduce only asexually.
ⓒ. It is dependent on the gametophyte and remains attached to it.
ⓓ. It produces flowers and seeds directly.
Correct Answer: It is dependent on the gametophyte and remains attached to it.
Explanation: The bryophyte sporophyte develops from the zygote and remains physically attached to the gametophyte. It depends on the gametophyte for nutrition because it is not fully independent in most bryophytes. Although it may perform limited photosynthesis in some cases, it still relies largely on the gametophyte for sustenance. The sporophyte’s main role is spore production through meiosis, enabling dispersal and continuation of the life cycle. This dependency is a defining feature used when comparing dominant phases across plant groups.
43. In pteridophytes, which phase is dominant and forms the conspicuous plant body?
ⓐ. Sporophyte
ⓑ. Gametophyte
ⓒ. Protonema
ⓓ. Thallus only
Correct Answer: Sporophyte
Explanation: Pteridophytes have a dominant sporophyte that is well-differentiated into roots, stems, and leaves. This sporophyte is independent and long-lived, making it the conspicuous plant body commonly observed. The gametophyte is comparatively small (often a prothallus) and short-lived, though usually free-living. This shift from gametophyte dominance (bryophytes) to sporophyte dominance (pteridophytes) is a major evolutionary step in land plants. Therefore, sporophyte dominance is a key classification basis for pteridophytes.
44. The small, generally free-living gametophyte of many ferns is called:
ⓐ. Sporophyll
ⓑ. Strobilus
ⓒ. Prothallus
ⓓ. Coleoptile
Correct Answer: Prothallus
Explanation: In many ferns, the gametophyte is a small, flat, green structure known as the prothallus. It develops from spores and bears the male and female sex organs (antheridia and archegonia). Even though it can photosynthesize and live independently, it is short-lived compared with the dominant sporophyte. Fertilization on the prothallus leads to the formation of a new sporophyte, which soon becomes the main plant body. Hence, “prothallus” correctly identifies the fern gametophyte.
45. Which feature best explains why seed plants show extreme reduction of the gametophyte?
ⓐ. The gametophyte becomes dependent and develops within sporophytic tissues for protection and efficiency.
ⓑ. The gametophyte becomes the main photosynthetic plant body in seed plants.
ⓒ. The gametophyte replaces the sporophyte completely in seed plants.
ⓓ. The gametophyte disappears because meiosis stops occurring.
Correct Answer: The gametophyte becomes dependent and develops within sporophytic tissues for protection and efficiency.
Explanation: In seed plants, the gametophytes are highly reduced and are retained within the tissues of the dominant sporophyte. This retention provides protection from desiccation and mechanical damage and allows more controlled reproduction on land. The male gametophyte is typically the pollen grain, and the female gametophyte develops within the ovule. Such reduction also supports efficient fertilization and embryo development without requiring a free-living gametophyte stage. Therefore, internal, dependent gametophytes are a key evolutionary trend in seed plants.
46. In angiosperms, the dominant generation is the sporophyte, while the male gametophyte is represented by:
ⓐ. Ovule
ⓑ. Pollen grain
ⓒ. Embryo
ⓓ. Endosperm
Correct Answer: Pollen grain
Explanation: Angiosperms exhibit a dominant sporophyte plant body with true roots, stems, leaves, and flowers. The male gametophyte is highly reduced and is represented by the pollen grain, which carries the cells that ultimately deliver male gametes. This reduction is part of the broader evolutionary pattern where the gametophyte becomes dependent on the sporophyte. The pollen grain is produced in the anther and functions in pollination and fertilization. Hence, pollen grain correctly represents the male gametophyte in angiosperms.
47. Which life-cycle trend is correctly arranged from bryophytes to angiosperms?
ⓐ. Sporophyte dominance decreases and gametophyte dominance increases.
ⓑ. Both sporophyte and gametophyte become equally dominant in all groups.
ⓒ. Gametophyte becomes dominant again in gymnosperms.
ⓓ. Gametophyte dominance decreases while sporophyte dominance increases.
Correct Answer: Gametophyte dominance decreases while sporophyte dominance increases.
Explanation: Bryophytes show dominant gametophytes with dependent sporophytes, reflecting early land-plant life-cycle organization. In pteridophytes, the sporophyte becomes dominant and independent, while the gametophyte is relatively small. In gymnosperms and angiosperms, the sporophyte remains dominant and the gametophytes become extremely reduced and dependent. This trend supports better terrestrial adaptation by protecting reproductive stages and improving efficiency. Therefore, the correct overall trend is increasing sporophyte dominance with progressive reduction of the gametophyte.
48. Which statement correctly describes alternation of generations in land plants in terms of phases?
ⓐ. Only the gametophyte exists, and the sporophyte is always absent.
ⓑ. Only the sporophyte exists, and the gametophyte is always absent.
ⓒ. Both phases occur, but meiosis does not occur in any phase.
ⓓ. Both gametophyte (haploid) and sporophyte (diploid) phases alternate, linked by fertilization and meiosis.
Correct Answer: Both gametophyte (haploid) and sporophyte (diploid) phases alternate, linked by fertilization and meiosis.
Explanation: Alternation of generations means plants pass through two multicellular phases: a haploid gametophyte and a diploid sporophyte. Fertilization converts haploid gametes into a diploid zygote that develops into the sporophyte. Meiosis in the sporophyte produces haploid spores that develop into the gametophyte. The relative dominance and independence of these phases varies across plant groups and is used for classification. Thus, both phases alternate and are connected by fertilization and meiosis.
49. In bryophytes, which structure typically bears the sex organs and directly participates as the main reproductive plant body?
ⓐ. Capsule
ⓑ. Sporophyte axis
ⓒ. Gametophyte thallus/leafy plant
ⓓ. Sporangium of fern frond
Correct Answer: Gametophyte thallus/leafy plant
Explanation: The bryophyte gametophyte is the main plant body and bears the sex organs (antheridia and archegonia). Because the sporophyte is attached and nutritionally dependent, the gametophyte directly supports and sustains the reproductive cycle. After fertilization on the gametophyte, the zygote develops into the sporophyte, which produces spores. This organization is central to the concept of gametophyte dominance in bryophytes. Therefore, the gametophyte thallus or leafy body is the structure that bears sex organs in bryophytes.
50. Which pair correctly matches the plant group with its dominant phase?
ⓐ. Bryophytes – Sporophyte dominant
ⓑ. Pteridophytes – Gametophyte dominant
ⓒ. Gymnosperms – Gametophyte dominant
ⓓ. Bryophytes – Gametophyte dominant
Correct Answer: Bryophytes – Gametophyte dominant
Explanation: Bryophytes are characterized by a dominant, free-living gametophyte that forms the main plant body. Their sporophyte remains attached to and dependent on the gametophyte for nutrition, making it non-dominant. In contrast, pteridophytes and seed plants show dominant sporophytes with reduced gametophytes. This difference in dominance is a standard NCERT basis for comparing major plant groups. Hence, the correct match is bryophytes with gametophyte dominance.
51. Which statement best describes the typical habitat of most algae?
ⓐ. Algae are predominantly aquatic and also occur in moist places like damp soil and tree trunks.
ⓑ. Algae are strictly terrestrial and cannot survive in water.
ⓒ. Algae are found only in deserts because they require very little water.
ⓓ. Algae are exclusively parasitic and live only inside animal bodies.
Correct Answer: Algae are predominantly aquatic and also occur in moist places like damp soil and tree trunks.
Explanation: Algae are primarily aquatic organisms found in freshwater and marine habitats, and they also occur in moist terrestrial microhabitats such as damp soil, wet rocks, and tree trunks where a thin water film persists. Their simple thallus body lacks specialized transport tissues, so surrounding moisture supports diffusion of nutrients and gases. Such conditions also provide adequate light for photosynthesis and continuous metabolic activity. This is why algal films and patches commonly appear on wet surfaces after rain or in humid, shaded areas. Hence, algae are mainly aquatic but can also thrive in moist places.
52. Which group of algae is most characteristically dominant in marine habitats, especially in colder seas?
ⓐ. Chlorophyceae (green algae)
ⓑ. Cyanobacteria (blue-green algae)
ⓒ. Charophytes
ⓓ. Phaeophyceae (brown algae)
Correct Answer: Phaeophyceae (brown algae)
Explanation: Brown algae are strongly associated with marine environments and are especially abundant in cooler coastal waters, where they often form large seaweeds and kelp forests. Their thallus is adapted to wave-swept shores with features like holdfasts for attachment and flexible bodies for withstanding water movement. Their pigment system is efficient for capturing light in marine conditions, supporting their dominance in many cold seas. This habitat association is a classic way to differentiate major algal groups in exam questions. Therefore, brown algae are most characteristically dominant in marine habitats.
53. Which statement about Chlorophyceae (green algae) habitat is most aligned with standard textbook concepts?
ⓐ. Green algae are exclusively marine and absent from freshwater.
ⓑ. Green algae are mainly found in freshwater, though some occur in marine conditions.
ⓒ. Green algae are restricted only to hot springs.
ⓓ. Green algae occur only in dry sand dunes.
Correct Answer: Green algae are mainly found in freshwater, though some occur in marine conditions.
Explanation: Green algae are commonly found in freshwater habitats such as ponds, lakes, and slow-moving streams, and they also occur on moist surfaces where water is available as a film. While freshwater dominance is typical, some green algae can also survive in marine or brackish waters. This broad ecological distribution helps in understanding algal diversity and habitat-based grouping. The freshwater association is also why many commonly observed algae in local environments are green. Hence, green algae are mainly freshwater with some marine representatives.
54. Red algae (Rhodophyceae) are primarily associated with which habitat pattern?
ⓐ. Strictly terrestrial deserts
ⓑ. Only freshwater marshes
ⓒ. Mostly marine, often found at greater depths compared to many other algae
ⓓ. Only inside plant roots as parasites
Correct Answer: Mostly marine, often found at greater depths compared to many other algae
Explanation: Red algae are predominantly marine, and many species occur at greater depths because their pigment composition allows efficient absorption of the wavelengths that penetrate deeper water. This depth-related distribution is a standard ecological point used to distinguish red algae from many other algal groups. Although a few red algae can occur in freshwater, the group is largely marine in overall diversity and abundance. Their marine adaptation also supports roles in coastal ecosystems and reef-associated communities. Therefore, red algae are mainly marine and often found at greater depths.
55. Why do algae commonly grow on damp rocks, wet soil, and tree bark in addition to water bodies?
ⓐ. Because moisture films provide enough water for diffusion of nutrients and metabolic activities in their simple thallus.
ⓑ. Because algae require complete dryness to prevent decay.
ⓒ. Because algae can only reproduce in air without water.
ⓓ. Because algae need vascular tissues to transport water internally.
Correct Answer: Because moisture films provide enough water for diffusion of nutrients and metabolic activities in their simple thallus.
Explanation: Algae generally lack complex vascular tissues, so they rely on surrounding water for nutrient absorption, gas exchange, and normal cellular activity. On damp rocks, wet soil, and moist bark, thin water films act like miniature aquatic habitats that support diffusion of minerals and gases into the thallus. These moist surfaces also provide light for photosynthesis and can remain wet for long periods in shaded or humid conditions. This explains the common green patches seen on walls, stones, and tree surfaces after rain. Hence, moisture films allow algae to colonize wet land surfaces successfully.
56. Which habitat-based statement correctly distinguishes many brown algae from many green algae?
ⓐ. Brown algae are mainly freshwater, while green algae are mainly marine.
ⓑ. Brown algae are mainly marine, while green algae are mainly freshwater.
ⓒ. Both brown and green algae are strictly terrestrial.
ⓓ. Both brown and green algae are strictly parasitic.
Correct Answer: Brown algae are mainly marine, while green algae are mainly freshwater.
Explanation: Brown algae are typically described as predominantly marine forms, often seen as large seaweeds along coasts, while green algae are commonly associated with freshwater habitats like ponds and lakes. Although there are exceptions, this broad habitat tendency is a frequent basis for quick conceptual classification questions. The difference reflects ecological specialization, including tolerance to salinity and coastal environmental conditions. This is why brown algae are strongly linked with marine habitats and green algae with freshwater habitats in many exam contexts. Therefore, brown algae are mainly marine whereas green algae are mainly freshwater.
57. A student observes heavy algal growth in a pond after nutrient enrichment. This habitat is best described as:
ⓐ. Xeric terrestrial habitat
ⓑ. Alpine dry habitat
ⓒ. Marine pelagic habitat
ⓓ. Freshwater aquatic habitat
Correct Answer: Freshwater aquatic habitat
Explanation: A pond is a freshwater aquatic ecosystem where algae can multiply rapidly when nutrients such as nitrates and phosphates increase. Algal thalli absorb dissolved nutrients directly from water, so enrichment commonly triggers dense growth or blooms. Such blooms are most typically observed in freshwater bodies like ponds and lakes where water is stagnant or slow-moving and light is available. This observation fits standard habitat concepts for algal distribution and growth responses. Hence, the pond environment is a freshwater aquatic habitat.
58. Which is the most appropriate match of algal habitat with a common example-like description?
ⓐ. Desert dunes — large kelp forests
ⓑ. Dry air — submerged seaweeds
ⓒ. Moist surfaces — green films on damp walls or wet rocks
ⓓ. Deep underground — photosynthetic algal mats
Correct Answer: Moist surfaces — green films on damp walls or wet rocks
Explanation: Algae often appear as green films on damp walls, wet stones, and shaded moist places because these surfaces provide persistent moisture essential for diffusion-based absorption and metabolism. Such sites also provide enough light for photosynthesis, allowing algae to grow even outside permanent water bodies. This is a common real-world observation used in exam questions to connect algae with “aquatic and moist” habitats. The growth pattern also reinforces that algae do not need true roots or vascular tissues to colonize these microhabitats. Therefore, moist surfaces with green films are a correct habitat-description match for algae.
59. Which habitat condition most strongly limits algal abundance in a location?
ⓐ. Prolonged dryness with lack of available water film
ⓑ. Presence of sunlight
ⓒ. Availability of dissolved minerals
ⓓ. Presence of carbon dioxide
Correct Answer: Prolonged dryness with lack of available water film
Explanation: Most algae depend on water around their thallus for nutrient uptake, gas exchange, and overall metabolic functioning because they lack specialized internal transport systems. When a location becomes dry for long periods, the water film needed for diffusion disappears, severely restricting algal growth and survival. Even if sunlight and carbon dioxide are present, the absence of moisture prevents normal physiological processes and reproduction. This is why algal growth concentrates in aquatic habitats or persistently moist terrestrial microhabitats. Hence, prolonged dryness is the strongest limiting factor for algal abundance.
60. “Moist habitat” for algae most accurately includes which set of locations?
ⓐ. Only deep ocean trenches
ⓑ. Damp soil, wet rocks, and tree trunks with water film
ⓒ. Completely dry sand and barren rocks under strong sun
ⓓ. Only inside animal tissues
Correct Answer: Damp soil, wet rocks, and tree trunks with water film
Explanation: Moist habitats include places where a thin layer of water persists long enough to support algal life processes. Damp soil, wet rocks, and tree trunks in humid areas commonly maintain such water films, allowing algae to absorb nutrients and carry out photosynthesis. These locations function as micro-aquatic environments, which is why algal patches are frequently seen on shaded walls, moist stones, and bark. This also shows how algae can extend beyond permanent water bodies without needing vascular tissues. Therefore, damp soil, wet rocks, and tree trunks with water film correctly represent moist habitats for algae.
61. The term “thallus” in algae most accurately refers to:
ⓐ. A plant body differentiated into true roots, stems, and leaves
ⓑ. A seed-bearing reproductive structure
ⓒ. A plant body not differentiated into true roots, stems, and leaves
ⓓ. A body made only of vascular tissues (xylem and phloem)
Correct Answer: A plant body not differentiated into true roots, stems, and leaves
Explanation: In algae, the plant body is commonly called a thallus because it lacks true roots, stems, and leaves. Instead of organ-level differentiation, most algae show simple structural organization such as unicellular, colonial, filamentous, or sheet-like forms. This simplicity is closely linked to their habitat, because direct contact with water allows absorption of minerals and gases across the body surface. Since they do not require complex transport tissues, a thallus form is efficient in aquatic or moist environments. Therefore, “thallus” correctly indicates an undifferentiated plant body typical of algae.
62. Why is a thalloid body plan especially suitable for algae in aquatic habitats?
ⓐ. Water directly surrounds the body, enabling diffusion-based uptake of minerals and gases across the thallus surface.
ⓑ. The thallus produces seeds that float long distances without any dispersal mechanism.
ⓒ. The thallus contains deep vascular bundles that pump water upward like a tree.
ⓓ. The thallus is always covered by a thick cuticle that prevents water entry.
Correct Answer: Water directly surrounds the body, enabling diffusion-based uptake of minerals and gases across the thallus surface.
Explanation: A thallus has a large surface area relative to volume, which supports direct exchange with the surrounding medium. In water, dissolved minerals, carbon dioxide, and oxygen can be absorbed or exchanged across the entire body surface without specialized organs. This is why algae can maintain simple body organization and still perform efficient photosynthesis and metabolism. The aquatic environment naturally provides continuous moisture and a medium for diffusion. Hence, the thalloid plan is particularly effective for algae in water-based habitats.
63. In many large marine algae, the structure that anchors the thallus to rocks is called:
ⓐ. Rhizoid
ⓑ. Root hair
ⓒ. Stolon
ⓓ. Holdfast
Correct Answer: Holdfast
Explanation: Large marine algae often possess a holdfast that attaches the thallus to a hard surface like rocks, preventing it from being swept away by waves. The holdfast functions mainly for anchorage and does not act like true roots in absorption and conduction. Since the entire thallus can absorb water and dissolved nutrients directly from seawater, an absorptive root system is not necessary. This reflects how thallus organization fits aquatic life. Therefore, “holdfast” is the correct anchoring structure in many seaweeds.
64. Which statement best distinguishes a thallus from a true plant body with organs?
ⓐ. A thallus always has flowers and fruits, but true plant body does not.
ⓑ. A thallus lacks true roots, stems, and leaves, while an organ-level plant body has them.
ⓒ. A thallus is always multicellular, while true plant body is always unicellular.
ⓓ. A thallus can survive only in deserts, while organ-level plants need water.
Correct Answer: A thallus lacks true roots, stems, and leaves, while an organ-level plant body has them.
Explanation: Thallus organization means there is no clear division into roots, stems, and leaves, and the body performs multiple functions without distinct organs. In organ-level plants, roots, stems, and leaves show specialization for absorption, support, conduction, and photosynthesis. This structural differentiation is typically linked to efficient transport and terrestrial adaptation. Algae generally do not require such differentiation because they live in water or very moist habitats where diffusion and surface absorption are sufficient. Hence, absence versus presence of true organs is the key distinguishing point.
65. A key habitat advantage of the thallus body in algae is that it:
ⓐ. Requires seeds for survival during unfavorable conditions
ⓑ. Prevents photosynthesis by blocking light entry
ⓒ. Needs vascular tissue to transport water from roots to leaves
ⓓ. Allows the whole body surface to participate in absorption and photosynthesis
Correct Answer: Allows the whole body surface to participate in absorption and photosynthesis
Explanation: In thalloid algae, there is no strict separation of functions into specialized organs, so the entire surface can contribute to absorption of minerals and gases. This also allows much of the body to photosynthesize wherever light is available, improving efficiency in aquatic environments. The surrounding water supplies dissolved nutrients directly, making surface-based uptake highly effective. This arrangement supports simple yet successful lifestyles in water bodies and moist areas. Therefore, whole-surface absorption and photosynthesis is a major advantage of the thallus plan.
66. Which body form is correctly matched with “thallus” organization in algae?
ⓐ. Filamentous strands made of repeated cells forming a simple plant body
ⓑ. A woody stem with secondary growth
ⓒ. A plant body with true roots and leaf veins
ⓓ. A seed-bearing cone structure
Correct Answer: Filamentous strands made of repeated cells forming a simple plant body
Explanation: Filamentous algae are classic examples of thallus organization, where the body is a chain of cells forming threads without true roots, stems, or leaves. This structural simplicity is enough for aquatic survival because the filaments remain in direct contact with water for nutrient exchange. Such thalli can be free-floating or attached, but still rely on surface absorption rather than internal transport. The form is efficient for capturing light and exchanging gases in water. Hence, filamentous strands represent a correct thallus body form.
67. Which statement best explains why most algae do not need true roots?
ⓐ. True roots are replaced by flowers in algae.
ⓑ. Because water and minerals are absorbed directly through the thallus surface from the surrounding medium.
ⓒ. Because algae obtain minerals only by eating other organisms.
ⓓ. Because algae live only inside soil and never contact water.
Correct Answer: Because water and minerals are absorbed directly through the thallus surface from the surrounding medium.
Explanation: In aquatic and moist habitats, algae are surrounded by water that contains dissolved minerals and gases. Their thallus surface can absorb these materials directly, so specialized absorptive organs like true roots provide little additional benefit. Even when algae attach to a substrate, attachment structures mainly help anchorage rather than absorption. This matches the basic functional logic of a thalloid body plan. Therefore, direct surface absorption is the primary reason true roots are generally unnecessary in algae.
68. A major ecological limitation of thallus organization is that it:
ⓐ. Cannot perform photosynthesis in any habitat
ⓑ. Produces only seeds and never spores
ⓒ. Is strongly dependent on water or moisture for efficient exchange and survival
ⓓ. Can grow tall like trees due to strong vascular bundles
Correct Answer: Is strongly dependent on water or moisture for efficient exchange and survival
Explanation: Because algae have a thallus body without complex internal transport systems, they rely heavily on external water for diffusion of minerals and gases. When moisture is absent, diffusion-based exchange becomes inefficient and metabolic activity is constrained. This is why algal growth is abundant in aquatic environments and damp terrestrial microhabitats, but limited under prolonged dry conditions. Their structural simplicity is an advantage in water, yet becomes a limitation in arid habitats. Hence, dependence on water or moisture is a key ecological constraint of thallus organization.
69. In many seaweeds, “stipe” and “blade” are best described as:
ⓐ. True stem and true leaf with vascular tissues
ⓑ. True root and true stem
ⓒ. Flower parts that produce seeds
ⓓ. Thallus regions that resemble stem and leaf but are not true organs
Correct Answer: Thallus regions that resemble stem and leaf but are not true organs
Explanation: Many seaweeds show body regions called stipe and blade that look like stem and leaf, respectively. However, these are not true organs because they typically lack the same structural differentiation and vascular tissues found in higher plants. They are parts of the thallus that contribute to support, flexibility, and light capture while maintaining surface-based exchange with seawater. This illustrates how thallus organization can become complex in appearance without becoming truly organ-differentiated. Therefore, stipe and blade are thallus regions rather than true stem and leaf.
70. The concept “thallus body” is most directly connected to which classification idea in algae?
ⓐ. Presence of flowers
ⓑ. Dominance of sporophyte phase only
ⓒ. Simple body organization without true organs, commonly linked with aquatic/moist habitats
ⓓ. Formation of fruits enclosing seeds
Correct Answer: Simple body organization without true organs, commonly linked with aquatic/moist habitats
Explanation: Thallus body describes a simple plant body lacking true roots, stems, and leaves, which is a major basis for understanding algal organization. This simplicity is functionally compatible with aquatic and moist habitats because water supports direct surface absorption and diffusion. The classification discussion often links body organization to habitat and adaptation, showing why algae can remain thalloid yet diverse and successful. The idea also helps differentiate algae from higher plants that evolved organ differentiation for terrestrial life. Hence, thallus organization is directly tied to simple body plan and aquatic/moist adaptation in algae.
71. The main photosynthetic pigment that gives green algae their characteristic colour is:
ⓐ. Chlorophyll a and chlorophyll b
ⓑ. Chlorophyll a and phycocyanin
ⓒ. Chlorophyll a and phycoerythrin
ⓓ. Chlorophyll a and fucoxanthin
Correct Answer: Chlorophyll a and chlorophyll b
Explanation: Green algae appear green primarily because they contain chlorophyll a and chlorophyll b as their major photosynthetic pigments. These chlorophylls absorb light effectively in the red and blue regions, and the reflected green light gives the visible green colour. This pigment combination is a key “deeper split” feature used to distinguish green algae from brown and red algae, which have different accessory pigments. The dominance of these chlorophylls also aligns green algae more closely with higher plants in pigment profile. Therefore, chlorophyll a and b best explain the characteristic green colour.
72. Which accessory pigment is most responsible for the brown colour of brown algae?
ⓐ. Xanthophylls and carotene only
ⓑ. Fucoxanthin
ⓒ. Phycoerythrin
ⓓ. Phycocyanin
Correct Answer: Fucoxanthin
Explanation: Brown algae contain chlorophyll a and c, but their brownish appearance is mainly due to the accessory pigment fucoxanthin. Fucoxanthin masks the green colour of chlorophyll by absorbing light in wavelengths that are abundant in marine environments, improving photosynthetic efficiency under water. This pigment is therefore a major diagnostic feature separating brown algae from green and red algae. It also helps explain why many brown algae thrive in marine habitats where light quality changes with depth. Hence, fucoxanthin is the key pigment responsible for the brown colour.
73. Red algae are characteristically rich in which pigment that imparts a red colour and supports photosynthesis at greater depths?
ⓐ. Chlorophyll b
ⓑ. Fucoxanthin
ⓒ. Phycoerythrin
ⓓ. Phycocyanin
Correct Answer: Phycoerythrin
Explanation: Red algae possess chlorophyll a (and often chlorophyll d in some forms), but the dominant pigment giving them a red appearance is phycoerythrin. This pigment efficiently absorbs blue-green light, which penetrates deeper into seawater, allowing red algae to photosynthesize in relatively deeper regions compared with many other algae. The pigment can mask chlorophyll’s green colour, leading to the characteristic red or reddish-brown appearance. Pigment composition is a central basis for splitting algal groups. Therefore, phycoerythrin is the most characteristic pigment of red algae.
74. The usual reserve food material in green algae is:
ⓐ. Floridean starch
ⓑ. Laminarin and mannitol
ⓒ. Glycogen
ⓓ. Starch
Correct Answer: Starch
Explanation: Green algae typically store reserve food mainly in the form of starch, often in association with their chloroplasts. This storage pattern is significant because it resembles the reserve food strategy of higher plants, supporting the conceptual link between green algae and plant-like metabolism. Reserve food type is used as a biochemical criterion for deeper classification within algae. In contrast, brown and red algae store different reserve materials. Hence, starch is the correct reserve food for green algae.
75. The characteristic reserve food in brown algae is:
ⓐ. Starch and oils
ⓑ. Laminarin and mannitol
ⓒ. Floridean starch
ⓓ. Glycogen and proteins
Correct Answer: Laminarin and mannitol
Explanation: Brown algae store reserve food mainly as laminarin (a carbohydrate) and mannitol (a sugar alcohol). This combination is a distinctive biochemical feature used to separate brown algae from green algae (starch) and red algae (floridean starch). Reserve food materials reflect metabolic pathways and adaptations to habitat, especially marine conditions. Because these compounds are repeatedly highlighted as characteristic of brown algae, they become common exam targets. Therefore, laminarin and mannitol are the correct reserve food materials for brown algae.
76. The reserve food material commonly stored in red algae is:
ⓐ. Floridean starch
ⓑ. Laminarin
ⓒ. Mannitol
ⓓ. Starch
Correct Answer: Floridean starch
Explanation: Red algae characteristically store their reserve food as floridean starch, which differs structurally and storage location from the typical plant starch in green algae. This reserve material is an important biochemical marker used in classifying red algae as a distinct group. Reserve food type is especially useful because it is relatively stable and reflects the organism’s fundamental metabolic organization. It also helps in distinguishing algal groups even when external appearance is confusing. Hence, floridean starch is the correct reserve food for red algae.
77. Which set correctly matches algal group with major pigments?
ⓐ. Green algae: chlorophyll a, c; Brown algae: chlorophyll a, b; Red algae: chlorophyll a, b
ⓑ. Green algae: chlorophyll a, b; Brown algae: chlorophyll a, c with fucoxanthin; Red algae: chlorophyll a with phycoerythrin
ⓒ. Green algae: phycoerythrin; Brown algae: phycocyanin; Red algae: fucoxanthin
ⓓ. Green algae: chlorophyll d only; Brown algae: chlorophyll b only; Red algae: chlorophyll c only
Correct Answer: Green algae: chlorophyll a, b; Brown algae: chlorophyll a, c with fucoxanthin; Red algae: chlorophyll a with phycoerythrin
Explanation: Green algae are characterized mainly by chlorophyll a and b, giving them a typical green colour. Brown algae contain chlorophyll a and c along with a strong masking accessory pigment, fucoxanthin, which produces the brown colour and improves underwater light capture. Red algae contain chlorophyll a and are rich in phycobilin pigments, especially phycoerythrin, which supports photosynthesis in deeper marine conditions. These pigment sets are standard classification markers for deeper splits in algae. Therefore, option B correctly matches major pigment profiles across the three groups.
78. Which statement best explains why pigment composition is used to classify algae into major groups?
ⓐ. Pigments are randomly produced and change every day
ⓑ. Pigments are only decorative and unrelated to photosynthesis
ⓒ. Pigment sets are stable biochemical features that affect light absorption and ecological distribution
ⓓ. Pigments depend only on water temperature and not on genetics
Correct Answer: Pigment sets are stable biochemical features that affect light absorption and ecological distribution
Explanation: Pigment composition is a fundamental biochemical character that reflects how algae capture and use light for photosynthesis. Different pigment combinations absorb different wavelengths, which strongly influences where algae can thrive, especially in aquatic environments where light quality changes with depth. Because pigment sets are genetically controlled and relatively stable, they provide reliable criteria for grouping and identifying algae. This approach also helps explain ecological patterns such as red algae occurring at greater depths and brown algae dominating many marine habitats. Hence, pigment composition is used because it is stable and ecologically meaningful.
79. A marine alga showing fucoxanthin and storing laminarin is most likely classified as:
ⓐ. Green alga
ⓑ. Red alga
ⓒ. Brown alga
ⓓ. Cyanobacterium
Correct Answer: Brown alga
Explanation: Fucoxanthin is a hallmark accessory pigment of brown algae and is responsible for their brown colour by masking chlorophyll. Laminarin is also a characteristic reserve food material of brown algae, often stored along with mannitol. When both fucoxanthin and laminarin are present together, the biochemical signature strongly points to brown algae rather than green or red algae. This kind of combined pigment-plus-reserve-food reasoning is a common deeper-concept classification approach. Therefore, the alga is most likely a brown alga.
80. Which combination correctly matches red algae with pigment and reserve food?
ⓐ. Chlorophyll a and b; starch
ⓑ. Chlorophyll a and c; laminarin
ⓒ. Chlorophyll b with fucoxanthin; mannitol
ⓓ. Chlorophyll a with phycoerythrin; floridean starch
Correct Answer: Chlorophyll a with phycoerythrin; floridean starch
Explanation: Red algae contain chlorophyll a and are particularly rich in phycoerythrin, a phycobilin pigment that gives a red colour and supports light absorption in deeper water. Their reserve food is floridean starch, which is a characteristic storage product used as an identification marker. This pigment–reserve pairing is important because it distinguishes red algae from green algae (chlorophyll b and starch) and brown algae (fucoxanthin and laminarin/mannitol). Using both pigment and reserve food together provides a high-confidence classification. Hence, chlorophyll a with phycoerythrin and floridean starch correctly matches red algae.
81. Which cell wall component is most characteristically associated with brown algae and contributes to their flexible, leathery thallus?
ⓐ. Peptidoglycan
ⓑ. Chitin
ⓒ. Lignin
ⓓ. Algin (alginic acid/alginates)
Correct Answer: Algin (alginic acid/alginates)
Explanation: Brown algae commonly have cell walls rich in algin, a colloidal polysaccharide that provides flexibility and high water-binding capacity. This is especially advantageous in marine habitats where thalli face wave action, desiccation during low tide, and mechanical stress. Algin helps maintain a tough yet pliable body form, allowing the thallus to bend without breaking. It is therefore a useful biochemical marker for deeper classification of algae. Along with cellulose, algin forms an important structural framework in many brown algae. Hence, algin is the characteristic wall component linked with brown algae.
82. The primary structural component of the cell wall in many green algae is:
ⓐ. Cellulose
ⓑ. Algin
ⓒ. Agar
ⓓ. Sporopollenin
Correct Answer: Cellulose
Explanation: In many green algae, the cell wall is mainly composed of cellulose microfibrils, which provide mechanical strength and maintain cell shape. This wall structure supports turgor pressure while still allowing exchange with the surrounding aquatic medium. Cellulose-based walls are also a plant-like feature that helps connect green algae with broader plant-type structural organization. Although additional materials may be present, cellulose remains the most consistent primary structural component. This makes it a common classification clue in questions comparing algal groups. Therefore, cellulose is the correct answer.
83. Red algae are best known for cell wall polysaccharides that are commercially important as gelling agents, mainly:
ⓐ. Algin and mannitol
ⓑ. Cellulose and lignin
ⓒ. Agar and carrageenan
ⓓ. Pectin and suberin
Correct Answer: Agar and carrageenan
Explanation: Red algae have cell walls that commonly contain unique polysaccharides such as agar and carrageenan, which can form gels and are widely used as thickening or stabilizing agents. These substances are part of the broader biochemical identity of red algae and serve as strong differentiators from brown algae (algin) and many green algae (cellulose-dominant walls). Their presence also reflects marine adaptation and distinct wall chemistry. In classification-based reasoning, such cell wall components are treated as stable and informative characters. Hence, agar and carrageenan are the correct wall-related markers for red algae.
84. Which option correctly matches an algal group with its typical pigment profile and a key cell wall component?
ⓐ. Green algae — chlorophyll a, c; algin-rich wall
ⓑ. Brown algae — chlorophyll a, c with fucoxanthin; algin-rich wall
ⓒ. Red algae — chlorophyll a, b; cellulose-only wall
ⓓ. Green algae — phycoerythrin; agar-rich wall
Correct Answer: Brown algae — chlorophyll a, c with fucoxanthin; algin-rich wall
Explanation: Brown algae are distinguished by chlorophyll a and c along with the accessory pigment fucoxanthin, which strongly influences their colour and light-harvesting in marine waters. A key wall feature is the presence of algin, contributing to flexibility and toughness of the thallus. This combination (pigments plus wall chemistry) is used in deeper splitting because it links physiology (light capture) with structure (wall composition). The pairing is consistent and commonly used to differentiate brown algae from green and red algae. Therefore, the correctly matched option is brown algae with fucoxanthin-related pigments and algin-rich walls.
85. Which statement best explains why algal cell wall composition is useful in classification?
ⓐ. Cell wall components are relatively stable biochemical traits that help distinguish major algal groups.
ⓑ. Cell wall composition changes randomly each day depending on sunlight.
ⓒ. Cell wall components are identical in all algae and therefore have no value.
ⓓ. Cell walls are absent in algae, so composition cannot be compared.
Correct Answer: Cell wall components are relatively stable biochemical traits that help distinguish major algal groups.
Explanation: Cell wall chemistry is controlled by genetic and metabolic pathways that remain fairly consistent within major algal lineages. Because different groups synthesize different dominant polysaccharides, wall composition becomes a reliable marker for grouping and identification. It also connects with ecological adaptation, such as flexibility in marine wave zones or gel-forming properties in certain marine algae. When combined with pigments and reserve food, cell wall components strengthen classification accuracy. This makes wall composition a high-value criterion in deeper comparative questions. Hence, stable biochemical differences in cell wall materials help distinguish algal groups.
86. A marine alga with chlorophyll a and c, fucoxanthin, and a cell wall rich in algin is most likely:
ⓐ. Chlorophyceae (green algae)
ⓑ. Rhodophyceae (red algae)
ⓒ. Charophyte alga
ⓓ. Phaeophyceae (brown algae)
Correct Answer: Phaeophyceae (brown algae)
Explanation: Fucoxanthin is a signature accessory pigment that is strongly associated with brown algae and often masks chlorophyll’s green colour. Chlorophyll a and c further support the brown-algal pigment set rather than green algae (which typically have chlorophyll b) or red algae (which are rich in phycobilins like phycoerythrin). The presence of algin in the wall is another strong indicator because it is commonly associated with the flexible thallus of brown seaweeds. Using pigment profile together with wall chemistry provides high-confidence identification. Therefore, the organism is best classified as Phaeophyceae (brown algae).
87. Which match correctly identifies red algae using both pigment category and cell wall chemistry?
ⓐ. Fucoxanthin dominant; algin-rich wall
ⓑ. Chlorophyll a and b dominant; cellulose-only wall
ⓒ. Phycobilins (especially phycoerythrin); agar/carrageenan in wall
ⓓ. Chlorophyll a and c dominant; lignin-rich wall
Correct Answer: Phycobilins (especially phycoerythrin); agar/carrageenan in wall
Explanation: Red algae are characterized by phycobilin pigments, particularly phycoerythrin, which helps them capture blue-green wavelengths in marine environments. Their walls often contain agar and carrageenan, polysaccharides known for gel-forming properties and used as key biochemical identifiers. This pigment–wall pairing distinguishes them from brown algae (fucoxanthin and algin) and many green algae (chlorophyll b and cellulose-dominant walls). Such combined traits reduce confusion when colour alone is not reliable. Hence, phycobilins with agar/carrageenan correctly identifies red algae.
88. Which cell wall feature most strongly differentiates many brown algae from many red algae?
ⓐ. Brown algae have peptidoglycan, red algae have lignin
ⓑ. Brown algae commonly have algin-rich walls, while red algae commonly have agar/carrageenan-rich walls
ⓒ. Brown algae have chitin walls, red algae have cellulose walls
ⓓ. Brown algae lack walls, red algae have thick cellulose walls
Correct Answer: Brown algae commonly have algin-rich walls, while red algae commonly have agar/carrageenan-rich walls
Explanation: Brown algae are widely associated with algin, which contributes to flexibility and toughness of the marine thallus. Red algae, on the other hand, commonly contain agar and carrageenan, wall polysaccharides with gel-forming properties. These differences are not minor; they reflect distinct biochemical pathways and produce functionally different wall behaviors. Because these wall components are comparatively stable within major groups, they are commonly used in classification and identification. Therefore, algin versus agar/carrageenan is a strong differentiating wall feature between brown and red algae.
89. If an alga shows phycoerythrin and its cell wall yields agar-like gel on processing, it most likely belongs to:
ⓐ. Green algae
ⓑ. Brown algae
ⓒ. Diatoms
ⓓ. Red algae
Correct Answer: Red algae
Explanation: Phycoerythrin is a hallmark pigment of red algae and supports efficient photosynthesis in marine conditions by capturing blue-green light. Agar-like gel production indicates the presence of wall polysaccharides such as agar, which are strongly associated with red algal walls. When both traits appear together—phycobilin pigment profile plus gel-forming wall chemistry—the classification inference becomes highly robust. This combined-character approach is standard for deeper-level grouping questions. Hence, the organism most likely belongs to red algae.
90. Which option correctly matches green algae with a key pigment category and typical wall component?
ⓐ. Chlorophyll a and b; cellulose-rich wall
ⓑ. Chlorophyll a and c; algin-rich wall
ⓒ. Phycobilins; agar-rich wall
ⓓ. Fucoxanthin; lignin-rich wall
Correct Answer: Chlorophyll a and b; cellulose-rich wall
Explanation: Green algae are defined by chlorophyll a and b as major pigments, which produce the characteristic green appearance and align with a plant-like pigment system. Their cell walls in many cases are primarily cellulose-based, providing structural support while allowing diffusion and exchange in aquatic environments. This pigment–wall combination helps separate green algae from brown algae (chlorophyll a, c with fucoxanthin and algin) and red algae (phycobilins with agar/carrageenan). Using both pigment category and wall component makes identification more reliable than using colour alone. Therefore, chlorophyll a and b with a cellulose-rich wall correctly matches green algae.
91. In Chlorophyceae, the green colour is mainly due to which pigment combination?
ⓐ. Chlorophyll a and chlorophyll c
ⓑ. Chlorophyll a and chlorophyll d
ⓒ. Chlorophyll a and chlorophyll b
ⓓ. Chlorophyll a and fucoxanthin
Correct Answer: Chlorophyll a and chlorophyll b
Explanation: Chlorophyceae contain chlorophyll a and chlorophyll b as their major photosynthetic pigments, and this pigment pair strongly reflects green light, giving the characteristic green appearance. These chlorophylls are embedded in thylakoid membranes where they capture light energy for photosynthesis. While carotenoids may be present as accessory pigments, they do not dominate the colour the way fucoxanthin does in brown algae. Because pigment composition is stable and diagnostic, chlorophyll a and b is a key criterion used to identify and separate Chlorophyceae from other algal groups.
92. Which statement best explains why chlorophyll b is an important “deeper split” character for Chlorophyceae?
ⓐ. It is a stable accessory pigment that broadens light absorption and is characteristic of green algae compared with many other algal groups.
ⓑ. It converts atmospheric nitrogen directly into nitrates for plant growth.
ⓒ. It forms the cell wall by combining with cellulose fibers.
ⓓ. It is produced only during sexual reproduction and disappears afterward.
Correct Answer: It is a stable accessory pigment that broadens light absorption and is characteristic of green algae compared with many other algal groups.
Explanation: Chlorophyll b acts as an accessory photosynthetic pigment that expands the range of light wavelengths captured for photosynthesis, transferring energy to chlorophyll a. Its consistent presence in Chlorophyceae makes it a reliable biochemical character to distinguish green algae from groups where chlorophyll b is absent and other accessory pigments dominate. This pigment-based approach is powerful because it connects directly to photosynthetic strategy and ecology. Therefore, chlorophyll b is not just “extra pigment”; it is a key classification marker that supports deeper splitting within algae.
93. Which pigment is typically absent in Chlorophyceae but common in brown algae, often masking the green colour of chlorophyll?
ⓐ. Phycoerythrin
ⓑ. Phycocyanin
ⓒ. Chlorophyll b
ⓓ. Fucoxanthin
Correct Answer: Fucoxanthin
Explanation: Fucoxanthin is a characteristic accessory pigment of brown algae that can dominate the visible colour by masking chlorophyll, giving a brownish appearance. Chlorophyceae, in contrast, show chlorophyll a and b as the primary pigment set, so they retain a green colour rather than brown. This pigment difference is not cosmetic; it reflects different light-harvesting strategies in aquatic environments. Hence, fucoxanthin is the pigment generally absent in Chlorophyceae but prominent in brown algae.
94. The chlorophyll a and b pigments in Chlorophyceae are located mainly in:
ⓐ. Cell wall matrix
ⓑ. Thylakoid membranes of chloroplasts
ⓒ. Cytosol dissolved freely
ⓓ. Nucleus attached to chromosomes
Correct Answer: Thylakoid membranes of chloroplasts
Explanation: Chlorophyll molecules are embedded in the thylakoid membranes where photosystems and electron transport components are organized. This location is essential because light energy captured by chlorophyll must be rapidly transferred into photochemical reactions that generate ATP and NADPH. In Chlorophyceae, chloroplasts house these thylakoid systems, enabling efficient photosynthesis in aquatic or moist habitats. Therefore, the correct cellular location for chlorophyll a and b is the thylakoid membranes inside chloroplasts.
95. Which statement correctly relates pigment composition of Chlorophyceae to their typical habitat preference?
ⓐ. Chlorophyll a and b allows Chlorophyceae to survive only in deserts.
ⓑ. Chlorophyll a and b prevents any photosynthesis in freshwater.
ⓒ. Chlorophyll a and b is found only in marine kelp forests.
ⓓ. Chlorophyll a and b supports efficient photosynthesis in well-lit freshwater and shallow-water conditions where many green algae commonly occur.
Correct Answer: Chlorophyll a and b supports efficient photosynthesis in well-lit freshwater and shallow-water conditions where many green algae commonly occur.
Explanation: Many green algae are abundant in freshwater ponds, lakes, and shallow water where light availability is high and the spectrum strongly supports chlorophyll-based absorption. The chlorophyll a and b system is effective in these conditions and allows rapid photosynthetic growth when nutrients and light are sufficient. While some green algae occur in marine or brackish habitats, their common association with well-lit freshwater environments aligns with their pigment profile. Hence, the chlorophyll a and b pigment system supports strong photosynthesis in typical habitats where Chlorophyceae are frequently found.
96. Which pigment pair best distinguishes Chlorophyceae from Rhodophyceae at the level of major photosynthetic pigments?
ⓐ. Chlorophyll a and chlorophyll c
ⓑ. Chlorophyll a and chlorophyll d
ⓒ. Chlorophyll a and chlorophyll b
ⓓ. Chlorophyll a and phycobilins (phycoerythrin/phycocyanin)
Correct Answer: Chlorophyll a and chlorophyll b
Explanation: Chlorophyceae are defined by the presence of chlorophyll a and b as major pigments, whereas red algae are notable for chlorophyll a along with prominent phycobilin pigments that influence colour and light absorption in marine environments. This difference is a core biochemical basis for separating these groups. The chlorophyll a and b pair is therefore a strong diagnostic feature for Chlorophyceae in classification and exam-style identification. Hence, chlorophyll a and b is the correct distinguishing pigment pair for Chlorophyceae.
97. Which example best fits Chlorophyceae that clearly shows chlorophyll a and b as major pigments?
ⓐ. Chlamydomonas
ⓑ. Laminaria
ⓒ. Polysiphonia
ⓓ. Sargassum
Correct Answer: Chlamydomonas
Explanation: Chlamydomonas is a classic green alga representative of Chlorophyceae and is characterized by chlorophyll a and b as major pigments. It is commonly used as an example because it clearly demonstrates typical green-algal features such as chloroplast-based photosynthesis and simple body organization. In contrast, Laminaria and Sargassum are brown algae, and Polysiphonia is a red alga, each with different dominant accessory pigments. Therefore, Chlamydomonas is the best Chlorophyceae example aligned with chlorophyll a and b.
98. Which additional pigment group is commonly present in Chlorophyceae along with chlorophyll a and b, functioning mainly in photoprotection and accessory light capture?
ⓐ. Tannins
ⓑ. Lignins
ⓒ. Phycobilins
ⓓ. Carotenoids (carotenes and xanthophylls)
Correct Answer: Carotenoids (carotenes and xanthophylls)
Explanation: Chlorophyceae typically contain carotenoids in addition to chlorophyll a and b, and these pigments help in accessory light harvesting and protection against photo-oxidative damage. Carotenoids can dissipate excess energy and protect chlorophyll and membranes from reactive oxygen species formed under strong light. They complement the chlorophyll system without dominating the visible colour the way fucoxanthin does in brown algae. Hence, carotenoids are the correct additional pigment group commonly present in Chlorophyceae.
99. Which statement is most accurate about how chlorophyll b contributes to photosynthesis in Chlorophyceae?
ⓐ. It replaces chlorophyll a and becomes the only pigment used in photosynthesis.
ⓑ. It blocks light absorption to reduce photosynthesis.
ⓒ. It expands the usable light spectrum and transfers captured energy to chlorophyll a in the photosystems.
ⓓ. It directly forms starch granules as reserve food.
Correct Answer: It expands the usable light spectrum and transfers captured energy to chlorophyll a in the photosystems.
Explanation: Chlorophyll b acts as an accessory pigment that absorbs light wavelengths not captured as efficiently by chlorophyll a, thereby broadening the effective absorption spectrum. The energy captured by chlorophyll b is transferred to chlorophyll a, which plays the central role in the reaction centers of photosystems. This improves overall photosynthetic efficiency, especially under variable light conditions in aquatic habitats. Therefore, chlorophyll b’s key role is to expand light capture and funnel energy to chlorophyll a.
100. In pigment-based classification, Chlorophyceae are best identified by the presence of:
ⓐ. Fucoxanthin as the dominant masking pigment
ⓑ. Chlorophyll a and b as major pigments
ⓒ. Phycoerythrin as the dominant pigment
ⓓ. Chlorophyll c as the major chlorophyll along with algin-rich walls
Correct Answer: Chlorophyll a and b as major pigments
Explanation: Pigment composition is a stable biochemical character used to separate major algal groups, and Chlorophyceae are consistently identified by chlorophyll a and chlorophyll b as their primary pigment set. This pigment profile explains their green appearance and supports a classification boundary with brown algae (fucoxanthin with chlorophyll a and c) and red algae (prominent phycobilins such as phycoerythrin). Because pigments directly reflect photosynthetic machinery and ecological adaptation, they provide strong diagnostic value. Hence, Chlorophyceae are best identified by chlorophyll a and b as major pigments.