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101. In the five-kingdom framework, phylogeny as a criterion refers to classification based on:
ⓐ. Similarity in habitat and lifestyle only
ⓑ. Body size and external appearance
ⓒ. Common ancestry and evolutionary relationships among organisms
ⓓ. Daily activity patterns such as nocturnal or diurnal
Correct Answer: Common ancestry and evolutionary relationships among organisms
Explanation: Phylogeny means the evolutionary history and relatedness of organisms. Using phylogeny in classification aims to group organisms that share a common ancestor and have evolved along related lineages. This makes classification more natural and biologically meaningful than grouping by superficial resemblance. It also helps explain similarities as inherited traits and differences as results of divergence. Thus, phylogeny-based grouping reflects evolutionary relationships. Therefore, common ancestry and evolutionary relationships define phylogeny as a criterion.
102. Why does incorporating phylogeny improve the biological value of a classification system?
ⓐ. It ensures organisms are grouped only by color and shape.
ⓑ. It reflects natural evolutionary relationships, making similarities explainable by descent.
ⓒ. It avoids using any characters and relies only on convenience.
ⓓ. It prevents organisms from being reclassified when new evidence appears.
Correct Answer: It reflects natural evolutionary relationships, making similarities explainable by descent.
Explanation: Phylogeny-based classification links groups through ancestry, providing a reason for shared characters. Similarities are interpreted as inherited traits from common ancestors rather than coincidental resemblance. This makes the system more explanatory and useful for understanding biodiversity. It also supports predicting inherited features and tracing evolutionary trends. Classification becomes a framework for studying evolution, not just organizing names. Hence, phylogeny improves value by reflecting natural evolutionary relationships.
103. Two organisms placed close together in a phylogeny-based classification are expected to:
ⓐ. Live in the same habitat always
ⓑ. Share fundamental traits due to recent common ancestry
ⓒ. Have identical size and body shape
ⓓ. Be unrelated but grouped for convenience
Correct Answer: Share fundamental traits due to recent common ancestry
Explanation: Phylogeny-based classification assumes that closer grouping indicates closer evolutionary relatedness. Organisms with a recent common ancestor are likely to share inherited fundamental traits. Differences may exist due to adaptation, but core similarities persist because of shared descent. This is why phylogenetic placement can be used to infer expected characters. Habitat and size are not reliable indicators of ancestry. Therefore, close placement suggests shared traits due to recent common ancestry.
104. Which statement best explains how phylogeny supports prediction of traits in classification?
ⓐ. Organisms with the same habitat must have the same traits.
ⓑ. Traits can be predicted because related groups inherit characters from common ancestors.
ⓒ. Traits can be predicted because classification is based only on one visible character.
ⓓ. Traits cannot be predicted because ancestry is irrelevant.
Correct Answer: Traits can be predicted because related groups inherit characters from common ancestors.
Explanation: Phylogeny connects organisms through descent, meaning traits can be inherited along lineages. When an organism is placed within a lineage, it is expected to share inherited features typical of that group. This provides a scientific basis for predicting certain characteristics before detailed study. Such inference is stronger when classification reflects ancestry rather than superficial similarity. Therefore, phylogeny supports prediction through inheritance from common ancestors. Hence, prediction works because related groups inherit characters from common ancestry.
105. Phylogeny as a criterion is most directly linked to which broad biological concept?
ⓐ. Uniformity of common names
ⓑ. Evolution and descent with modification
ⓒ. Climate and weather patterns
ⓓ. Daily feeding schedule of organisms
Correct Answer: Evolution and descent with modification
Explanation: Phylogeny is the study of evolutionary relationships, which are produced by descent with modification. Over generations, lineages change, leading to both shared traits and differences among descendants. Phylogeny-based classification places organisms in a way that reflects these evolutionary pathways. This makes the system directly connected to how biodiversity arose. It also helps interpret organismal similarity as evidence of shared descent. Therefore, phylogeny is most directly linked to evolution and descent with modification.
106. A classification system guided by phylogeny would primarily aim to:
ⓐ. Group organisms that look alike, even if unrelated
ⓑ. Arrange organisms according to their evolutionary branching relationships
ⓒ. Separate organisms only by where they live
ⓓ. Classify organisms only by their economic importance
Correct Answer: Arrange organisms according to their evolutionary branching relationships
Explanation: Phylogeny depicts evolutionary branching, where lineages split and diverge over time. A phylogeny-guided classification tries to reflect this branching order in grouping organisms. This arrangement provides insight into which organisms are more closely related. It also clarifies how major groups evolved from earlier forms. Such a system is more than convenience—it is an evolutionary map of relationships. Hence, it primarily aims to arrange organisms by evolutionary branching relationships.
107. Which situation best illustrates the phylogenetic basis of grouping?
ⓐ. Grouping dolphins with fishes because both swim in water
ⓑ. Grouping organisms with the same body size into one category
ⓒ. Grouping organisms based on common ancestry even if they differ in habitat
ⓓ. Grouping organisms only by their color patterns
Correct Answer: Grouping organisms based on common ancestry even if they differ in habitat
Explanation: Phylogenetic grouping prioritizes ancestry over superficial similarities. Organisms can adapt to different habitats but still share common descent and inherited characters. Therefore, habitat difference does not necessarily separate related organisms in phylogeny-based systems. This approach avoids misleading groupings that result from convergent adaptations. It explains similarities through inheritance rather than environment alone. Hence, grouping by common ancestry despite habitat differences best illustrates phylogenetic basis.
108. In evolutionary classification, shared characters among members of a group are primarily interpreted as:
ⓐ. Random coincidences without biological meaning
ⓑ. Traits acquired independently in each organism
ⓒ. Traits inherited from a common ancestor
ⓓ. Traits produced only by the same climate
Correct Answer: Traits inherited from a common ancestor
Explanation: Phylogeny-based classification treats shared characters as evidence of common origin. When organisms share fundamental traits, it suggests these traits were present in their common ancestor and passed down. This provides a coherent explanation for similarity across organisms. Environmental factors can influence traits, but inherited characters are key to establishing relatedness. This interpretation is central to evolutionary reasoning in classification. Therefore, shared characters are primarily viewed as inherited from a common ancestor.
109. Which statement best summarizes the role of phylogeny within the five-kingdom criteria?
ⓐ. It is used to group organisms only by their economic value.
ⓑ. It complements cell structure, organisation, nutrition, and reproduction by adding an evolutionary relationship perspective.
ⓒ. It replaces the need for all other criteria.
ⓓ. It depends only on habitat similarity.
Correct Answer: It complements cell structure, organisation, nutrition, and reproduction by adding an evolutionary relationship perspective.
Explanation: Phylogeny adds the evolutionary dimension to classification, explaining why certain groups share traits. While cell structure, body organisation, nutrition, and reproduction provide key observable criteria, phylogeny ties them to ancestry and evolutionary divergence. This makes classification more natural and interpretative rather than purely descriptive. It also strengthens prediction of inherited traits and understanding of biodiversity patterns. Therefore, phylogeny complements the other criteria by adding evolutionary relationship perspective.
110. A major advantage of using phylogeny as a basis of classification is that it:
ⓐ. Guarantees identical traits among all members of a kingdom
ⓑ. Always groups organisms by habitat first
ⓒ. Avoids any need to compare characters
ⓓ. Helps trace evolutionary trends and relationships among major groups
Correct Answer: Helps trace evolutionary trends and relationships among major groups
Explanation: Phylogeny-based classification allows scientists to interpret classification as an evolutionary framework. It helps trace how groups may have diverged and how traits evolved over time. This supports understanding of biodiversity as the result of evolutionary change rather than isolated categories. It also aids in predicting inherited features within lineages. Such a system is especially valuable for comparative biology and evolutionary studies. Hence, it helps trace evolutionary trends and relationships among major groups.
111. Which feature is the most reliable single basis to separate prokaryotic cells from eukaryotic cells?
ⓐ. Presence of ribosomes
ⓑ. Presence of cytoplasm
ⓒ. Presence of DNA
ⓓ. Presence of a true nucleus bounded by a nuclear membrane
Correct Answer: Presence of a true nucleus bounded by a nuclear membrane
Explanation: Eukaryotic cells have their genetic material enclosed within a well-defined nucleus surrounded by a nuclear membrane. This compartmentalization allows regulated transport between nucleus and cytoplasm and supports higher cellular complexity. In prokaryotes, genetic material is not enclosed by a nuclear membrane and lies in a nucleoid region. This difference is fundamental and consistent across groups. It also correlates with the presence of membrane-bound organelles in eukaryotes. Hence, a true nucleus is the most reliable separating feature.
112. Which statement correctly describes membrane-bound organelles in prokaryotes versus eukaryotes?
ⓐ. Prokaryotes lack membrane-bound organelles, while eukaryotes possess them.
ⓑ. Both prokaryotes and eukaryotes have membrane-bound mitochondria.
ⓒ. Only prokaryotes have membrane-bound Golgi bodies.
ⓓ. Only eukaryotes lack membrane-bound organelles.
Correct Answer: Prokaryotes lack membrane-bound organelles, while eukaryotes possess them.
Explanation: Eukaryotic cells are characterized by internal membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus. These organelles create compartmentalization, allowing specialized functions to occur efficiently in distinct regions. Prokaryotic cells do not have such membrane-bound compartments; most functions occur in the cytoplasm or at the plasma membrane. This distinction is a key part of the prokaryote–eukaryote separation. It also explains differences in complexity and cellular regulation. Therefore, the presence of membrane-bound organelles is a defining eukaryotic feature.
113. In prokaryotes, transcription and translation can occur simultaneously mainly because:
ⓐ. DNA is located inside mitochondria
ⓑ. Ribosomes are absent in the cytoplasm
ⓒ. There is no nuclear membrane separating DNA from ribosomes
ⓓ. Proteins are synthesized only during cell division
Correct Answer: There is no nuclear membrane separating DNA from ribosomes
Explanation: Prokaryotic cells do not have a nucleus, so DNA lies in the cytoplasm where ribosomes are also present. Because there is no nuclear membrane barrier, the mRNA being synthesized can be immediately used by ribosomes for protein synthesis. This coupling of transcription and translation is a characteristic functional consequence of prokaryotic organization. It reflects their simpler cellular compartmentalization. This feature helps explain the speed and efficiency of gene expression in prokaryotes. Hence, absence of a nuclear membrane enables simultaneous transcription and translation.
114. Which statement correctly describes the main genetic material in typical bacterial (prokaryotic) cells?
ⓐ. It is linear DNA enclosed in a nuclear envelope.
ⓑ. It is usually a single circular DNA molecule located in the nucleoid region.
ⓒ. It is multiple linear chromosomes packed with histones in a nucleus.
ⓓ. It is absent and replaced entirely by RNA.
Correct Answer: It is usually a single circular DNA molecule located in the nucleoid region.
Explanation: In typical bacteria, the primary genetic material is a single circular, double-stranded DNA molecule. This DNA is not enclosed within a nuclear membrane; instead, it occupies a region called the nucleoid. This organization is a key feature of prokaryotic cells and contrasts with the nuclear chromosomes of eukaryotes. The circular chromosome carries essential genes needed for survival and reproduction. This arrangement supports simpler cell architecture and rapid replication. Therefore, bacterial genetic material is usually a single circular DNA molecule in the nucleoid.
115. Which cell wall component is characteristic of most bacterial prokaryotes?
ⓐ. Peptidoglycan
ⓑ. Cellulose
ⓒ. Chitin
ⓓ. Lignin
Correct Answer: Peptidoglycan
Explanation: The bacterial cell wall is primarily made of peptidoglycan, a polymer of sugars cross-linked by short peptides. This structure provides rigidity, protects against osmotic lysis, and helps maintain cell shape. It is a key structural feature used to recognize bacterial prokaryotes. Because cell wall composition is a stable cellular character, it is useful in classification and basic identification. The presence of peptidoglycan is strongly associated with bacteria among prokaryotes. Hence, peptidoglycan is the characteristic bacterial cell wall component.
116. Which process is directly involved in forming gametes and is therefore a clear eukaryotic feature (not found in prokaryotes)?
ⓐ. Binary fission
ⓑ. Budding
ⓒ. Fragmentation
ⓓ. Meiosis
Correct Answer: Meiosis
Explanation: Meiosis is a specialized cell division that reduces chromosome number by half and produces haploid cells used as gametes in sexual reproduction. This process requires organized chromosomes and complex division machinery typical of eukaryotic cells. It is closely associated with sexual life cycles and genetic recombination. Prokaryotes do not undergo meiosis; they primarily multiply through simple cell division. Meiosis also underpins variation by reshuffling genetic material across generations. Therefore, meiosis is a clear eukaryotic feature linked to gamete formation.
117. A eukaryotic cell is expected to have which type of ribosomes in its cytoplasm?
ⓐ. 50S ribosomes
ⓑ. 60S ribosomes
ⓒ. 80S ribosomes
ⓓ. 70S ribosomes only
Correct Answer: 80S ribosomes
Explanation: The cytoplasm of eukaryotic cells typically contains 80S ribosomes, which are formed by the association of 60S and 40S subunits. These ribosomes carry out protein synthesis in the cytosol and on the rough endoplasmic reticulum. Ribosome type is a useful cellular character for distinguishing broad groups of organisms. The 80S ribosome reflects the eukaryotic cellular organization and protein synthesis machinery. This feature is consistent across plants, animals, fungi, and protists. Hence, eukaryotic cytoplasm characteristically contains 80S ribosomes.
118. Which statement best describes the usual size comparison between prokaryotic and eukaryotic cells?
ⓐ. Prokaryotic cells are usually larger than eukaryotic cells.
ⓑ. Prokaryotic cells are generally smaller than eukaryotic cells.
ⓒ. Both are usually the same size because size is fixed by DNA amount.
ⓓ. Size cannot be compared because all cells have identical dimensions.
Correct Answer: Prokaryotic cells are generally smaller than eukaryotic cells.
Explanation: Prokaryotic cells are typically smaller and simpler in organization, commonly measuring a few micrometers in size. Their smaller size is consistent with lack of membrane-bound organelles and simpler internal compartmentalization. Eukaryotic cells are generally larger and more complex, supporting organelles and greater internal organization. This size difference is a broad trend used as supporting evidence in basic comparisons. It also influences surface-area-to-volume relationships and cellular efficiency. Therefore, prokaryotic cells are generally smaller than eukaryotic cells.
119. Which feature best supports calling eukaryotic DNA organization “chromosomal” in a true nucleus?
ⓐ. DNA is organized into multiple linear chromosomes within the nucleus.
ⓑ. DNA is always a single circular loop in the cytoplasm.
ⓒ. DNA is absent and replaced by proteins.
ⓓ. DNA is located only in the cell wall.
Correct Answer: DNA is organized into multiple linear chromosomes within the nucleus.
Explanation: In eukaryotes, genetic material is organized as multiple linear chromosomes. These chromosomes are housed inside a true nucleus, enabling regulated replication, transcription, and chromosome segregation. The linear chromosomal arrangement supports complex gene regulation and packaging mechanisms. This organization is a hallmark of eukaryotic cellular structure and contrasts with the nucleoid-based DNA arrangement of prokaryotes. It also aligns with mitosis and meiosis seen in eukaryotic life cycles. Hence, eukaryotic DNA is organized into multiple linear chromosomes within the nucleus.
120. Which statement correctly captures a key difference in cell division between prokaryotes and eukaryotes?
ⓐ. Prokaryotes divide by mitosis, while eukaryotes divide by binary fission.
ⓑ. Prokaryotes form tissues during division, while eukaryotes do not.
ⓒ. Prokaryotes typically divide by binary fission, while eukaryotic somatic cells divide by mitosis.
ⓓ. Both groups divide only by meiosis.
Correct Answer: Prokaryotes typically divide by binary fission, while eukaryotic somatic cells divide by mitosis.
Explanation: Prokaryotes usually multiply through binary fission, where the DNA replicates and the cell splits into two daughter cells. Eukaryotic somatic cells divide by mitosis, a process involving chromosome condensation, spindle formation, and organized segregation. This difference reflects the complexity of eukaryotic chromosomes and nuclear organization. Binary fission is simpler and matches the prokaryotic cell plan. Mitosis supports accurate distribution of multiple linear chromosomes in eukaryotes. Therefore, binary fission versus mitosis is a key division difference between prokaryotes and eukaryotes.
121. Which statement best distinguishes unicellular organisms from multicellular organisms?
ⓐ. Unicellular organisms perform all life functions within a single cell, while multicellular organisms show division of labour among many cells.
ⓑ. Unicellular organisms always have tissues and organs, while multicellular organisms never do.
ⓒ. Unicellular organisms are always visible to the naked eye, while multicellular organisms are microscopic.
ⓓ. Unicellular organisms do not carry genetic material, while multicellular organisms do.
Correct Answer: Unicellular organisms perform all life functions within a single cell, while multicellular organisms show division of labour among many cells.
Explanation: In unicellular organisms, one cell carries out nutrition, respiration, excretion, reproduction, and other life processes. Multicellular organisms consist of many cells that become specialized for different functions, creating division of labour. This specialization supports tissue and organ formation and improves efficiency. The distinction is foundational in body organisation criteria used in classification. It also explains why multicellular organisms can develop complex structures and functions. Hence, single-cell function versus division of labour is the key distinction.
122. Which outcome is most directly associated with multicellularity?
ⓐ. Absence of cellular specialization
ⓑ. Division of labour through specialized cells
ⓒ. Lack of coordination between parts
ⓓ. Inability to maintain internal balance
Correct Answer: Division of labour through specialized cells
Explanation: Multicellularity allows different cells to specialize for distinct roles, such as transport, protection, or secretion. This division of labour increases efficiency and supports complex body organisation. Specialized cells often form tissues and organs that work together in a coordinated manner. Such organization enables advanced physiological functions not possible in single-cell bodies. This is why multicellular groups are separated as distinct kingdoms in major classification. Therefore, division of labour is the most direct outcome of multicellularity.
123. In kingdom-level classification, unicellular eukaryotes are primarily placed under:
ⓐ. Plantae
ⓑ. Animalia
ⓒ. Protista
ⓓ. Fungi
Correct Answer: Protista
Explanation: Protista mainly includes organisms that are eukaryotic but typically unicellular or very simple in organization. They possess a true nucleus and membrane-bound organelles, yet lack the tissue-level complexity of plants and animals. This kingdom provides a place for unicellular eukaryotes that do not fit into multicellular kingdoms. Body organisation is a key criterion supporting this placement. Hence, unicellular eukaryotes are primarily placed under Protista.
124. Which statement correctly explains why unicellularity alone is not sufficient to place an organism in Monera?
ⓐ. Because unicellularity occurs only in plants
ⓑ. Because both Monera and Protista include unicellular organisms, but they differ in cell structure
ⓒ. Because all unicellular organisms are multicellular at some stage
ⓓ. Because unicellular organisms cannot reproduce
Correct Answer: Because both Monera and Protista include unicellular organisms, but they differ in cell structure
Explanation: Unicellularity is found in both prokaryotic and eukaryotic organisms. Monera includes unicellular prokaryotes, while Protista includes unicellular eukaryotes. Therefore, cell structure (prokaryotic vs eukaryotic) must be considered along with body organisation to classify correctly. Relying only on unicellularity would mix fundamentally different cellular plans. This is why multiple criteria are used in the five-kingdom approach. Hence, unicellularity alone is insufficient because cell structure differs between Monera and Protista.
125. Which feature best indicates multicellular organisation rather than a simple colony of cells?
ⓐ. Temporary clustering without specialization
ⓑ. All cells performing identical functions without coordination
ⓒ. Presence of specialized cells with coordinated division of labour
ⓓ. Cells separating easily and functioning independently all the time
Correct Answer: Presence of specialized cells with coordinated division of labour
Explanation: True multicellularity is characterized by specialization of cells and coordinated functioning among them. This creates division of labour, where different cell types perform different roles. In simple colonies, cells may remain similar and often have limited specialization. Coordination and specialization allow formation of tissues and more complex structures. Such organization supports greater physiological integration. Therefore, specialized and coordinated division of labour indicates multicellular organisation.
126. Which kingdom is primarily multicellular and shows ingestive heterotrophic nutrition?
ⓐ. Animalia
ⓑ. Plantae
ⓒ. Monera
ⓓ. Protista
Correct Answer: Animalia
Explanation: Animals are generally multicellular organisms with complex body organisation. They obtain nutrition by ingestion, taking food into the body and digesting it internally. This mode of nutrition is closely linked to their structural complexity and active lifestyle. These features help separate animals from plants (primarily autotrophic) and fungi (absorptive heterotrophs). Body organisation and nutrition together strongly define Animalia. Hence, Animalia is primarily multicellular with ingestive heterotrophic nutrition.
127. Which statement best describes the functional limitation typically associated with unicellular organisation?
ⓐ. Unicellular organisms cannot respond to stimuli.
ⓑ. Unicellular organisms cannot reproduce.
ⓒ. Unicellular organisms cannot perform metabolism.
ⓓ. Unicellular organisms have limited division of labour because one cell must perform all functions.
Correct Answer: Unicellular organisms have limited division of labour because one cell must perform all functions.
Explanation: In unicellular organisms, a single cell must carry out all essential life processes. This limits the extent of specialization possible within the organism. While unicellular organisms can be highly efficient, they do not show tissue and organ-level division of labour. This is a key reason body organisation is used as a classification criterion. It explains why complexity increases with multicellularity. Therefore, limited division of labour is the typical functional limitation of unicellular organisation.
128. Multicellular organisms generally show better internal coordination mainly due to:
ⓐ. The absence of specialized structures
ⓑ. Communication and cooperation among specialized cells and tissues
ⓒ. The lack of cellular interactions
ⓓ. The inability to form organized structures
Correct Answer: Communication and cooperation among specialized cells and tissues
Explanation: Multicellularity allows cells to differentiate and form tissues and organs. These specialized units communicate and coordinate to maintain overall function and internal balance. Coordination enables complex processes like transport, regulation, and integrated responses. Such cooperation is a hallmark of higher body organisation and supports survival in varied conditions. This is why multicellular organisms can achieve higher complexity. Hence, communication and cooperation among specialized cells and tissues explain better internal coordination.
129. A key body-organisation distinction between Protista and Plantae is that:
ⓐ. Protista are mostly unicellular, while Plantae are predominantly multicellular with higher organisation
ⓑ. Protista are prokaryotic, while Plantae are prokaryotic
ⓒ. Protista are always multicellular, while Plantae are always unicellular
ⓓ. Both are identical in body organisation, so they cannot be separated
Correct Answer: Protista are mostly unicellular, while Plantae are predominantly multicellular with higher organisation
Explanation: Protista mainly consists of unicellular eukaryotes with simple body organisation. Plantae includes multicellular eukaryotes with higher structural complexity, often showing tissue-level organisation. This difference in body organisation is central to their separation in the five-kingdom system. It prevents mixing eukaryotic microorganisms with complex multicellular plants. Body organisation thus provides a clear basis for distinguishing these kingdoms. Therefore, Protista are mostly unicellular while Plantae are predominantly multicellular with higher organisation.
130. Which statement best supports the use of body organisation as a criterion in classification?
ⓐ. Body organisation is random and does not reflect biological complexity.
ⓑ. Body organisation stays constant across all organisms.
ⓒ. Body organisation reflects structural complexity and division of labour, helping separate major groups.
ⓓ. Body organisation depends only on the color of the organism.
Correct Answer: Body organisation reflects structural complexity and division of labour, helping separate major groups.
Explanation: Body organisation indicates how an organism is built, from single-cell forms to complex multicellular organisms. Increasing complexity often brings specialization and division of labour, which are biologically meaningful differences. This makes body organisation a strong criterion for grouping organisms at high taxonomic levels. It also supports understanding of functional capacity and evolutionary advancement in complexity. Because it reflects real structural and functional differences, it is useful in classification. Hence, body organisation is used because it reflects complexity and division of labour that separate major groups.
131. Which statement best defines an autotrophic mode of nutrition in classification?
ⓐ. Obtaining ready-made organic food by ingestion
ⓑ. Absorbing dissolved organic nutrients from dead matter
ⓒ. Feeding only on living host tissues
ⓓ. Synthesizing organic food from inorganic raw materials using light or chemical energy
Correct Answer: Synthesizing organic food from inorganic raw materials using light or chemical energy
Explanation: Autotrophs build their own organic molecules (like glucose) using inorganic substances such as $CO_2$, $H_2O$, and mineral ions. The energy for this synthesis comes either from sunlight (photoautotrophy) or from oxidation of inorganic compounds (chemoautotrophy). This nutritional strategy makes autotrophs primary producers in ecosystems. Because it is a fundamental life strategy, it is used as a major classification criterion. It also explains why autotroph-dominated groups occupy distinct positions in food chains. Hence, autotrophy is defined by self-synthesis of organic food from inorganic sources.
132. In the five-kingdom approach, which kingdom is primarily characterized by autotrophic nutrition in most of its members?
ⓐ. Plantae
ⓑ. Fungi
ⓒ. Animalia
ⓓ. Monera
Correct Answer: Plantae
Explanation: Members of Plantae are generally multicellular organisms that prepare their own food by photosynthesis. Their chlorophyll-based energy capture allows conversion of $CO_2$ and $H_2O$ into carbohydrates, making them primary producers. This dominant autotrophic strategy is a key reason plants are separated from heterotrophic kingdoms. It also correlates with ecological roles such as supporting higher trophic levels. While exceptions exist in nature, the kingdom-level trend remains primarily autotrophic. Therefore, Plantae is chiefly characterized by autotrophic nutrition.
133. Which mode of nutrition is most characteristic of animals and helps separate them from other heterotrophic kingdoms?
ⓐ. Absorptive nutrition after external digestion
ⓑ. Autotrophic nutrition by photosynthesis
ⓒ. Ingestive (holozoic) nutrition with internal digestion
ⓓ. Chemosynthetic autotrophy
Correct Answer: Ingestive (holozoic) nutrition with internal digestion
Explanation: Animals typically obtain food by ingestion, taking solid or liquid organic matter into the body. Digestion occurs internally, breaking food into simpler molecules that can be absorbed and used. This ingestive strategy is closely tied to animal body organization and active feeding behavior. It differs fundamentally from fungi, which digest externally and absorb nutrients. Because nutrition is a major criterion, this holozoic mode strongly supports placing animals in a separate kingdom. Hence, ingestive nutrition with internal digestion is characteristic of animals.
134. Fungi are separated as a distinct kingdom largely because their heterotrophic nutrition is mainly:
ⓐ. Ingestive, like most animals
ⓑ. Absorptive, involving external digestion followed by absorption
ⓒ. Autotrophic, using chlorophyll
ⓓ. Chemosynthetic, using inorganic oxidation as the main strategy
Correct Answer: Absorptive, involving external digestion followed by absorption
Explanation: Fungi secrete digestive enzymes onto the substrate (dead organic matter or host tissues). These enzymes break complex molecules into soluble products outside the body. The fungal cells then absorb these nutrients across their surface. This absorptive strategy is consistent across fungi and is fundamentally different from ingestive feeding in animals and autotrophy in plants. Because it is a defining functional feature, it is used as a major classification criterion. Therefore, fungi are characterized primarily by absorptive nutrition.
135. Which statement correctly explains why “mode of nutrition” is preferred over habitat for major grouping of organisms?
ⓐ. Habitat never overlaps between unrelated organisms.
ⓑ. Habitat is a cellular character, while nutrition is not.
ⓒ. Nutrition changes daily, so it is more flexible for grouping.
ⓓ. Nutrition reflects a fundamental biological strategy, while habitat similarity can occur in unrelated organisms.
Correct Answer: Nutrition reflects a fundamental biological strategy, while habitat similarity can occur in unrelated organisms.
Explanation: Mode of nutrition is a core functional trait that influences physiology, life strategy, and ecological role. Unrelated organisms can share the same habitat due to similar environmental demands, which can mislead grouping if habitat is used alone. Nutritional strategy, however, directly represents how energy and matter are obtained and processed. This makes it more stable and biologically informative at higher levels. It also helps distinguish major kingdoms such as plants, animals, and fungi. Hence, nutrition is preferred because it reflects fundamental strategy whereas habitat can converge across unrelated groups.
136. Which kingdom includes organisms that can be either autotrophic or heterotrophic, making nutrition highly diverse at the kingdom level?
ⓐ. Monera
ⓑ. Plantae
ⓒ. Animalia
ⓓ. Fungi
Correct Answer: Monera
Explanation: Monera includes prokaryotic organisms with a wide range of nutritional strategies. Some members are autotrophic, including photosynthetic and chemosynthetic forms, while many others are heterotrophic. This diversity is one reason multiple criteria (cell type, organization, and nutrition) are used together in classification. Nutritional flexibility in Monera reflects their metabolic versatility and ecological breadth. Despite nutritional differences, their prokaryotic cell structure provides the unifying basis for placement. Therefore, Monera shows high nutritional diversity with both autotrophs and heterotrophs.
137. Chemoautotrophic nutrition is best described as:
ⓐ. Absorbing nutrients from dead organic matter only
ⓑ. Ingesting food and digesting it internally
ⓒ. Synthesizing organic food using energy from oxidation of inorganic substances
ⓓ. Producing food only using sunlight and chlorophyll
Correct Answer: Synthesizing organic food using energy from oxidation of inorganic substances
Explanation: Chemoautotrophs do not depend on sunlight for energy. Instead, they obtain energy by oxidizing inorganic compounds such as ammonia, nitrites, hydrogen sulfide, or ferrous ions. This energy is then used to fix $CO_2$ into organic molecules. The process is a form of autotrophy because the carbon source is inorganic, even though the energy source is chemical. It is especially important in environments with little or no light. Hence, chemoautotrophy means synthesizing organic food using energy from inorganic oxidation.
138. A saprotrophic organism is best defined as one that:
ⓐ. Synthesizes food using sunlight
ⓑ. Lives only as a parasite inside hosts
ⓒ. Obtains food by ingestion and internal digestion
ⓓ. Obtains nutrients from dead and decaying organic matter through enzyme secretion and absorption
Correct Answer: Obtains nutrients from dead and decaying organic matter through enzyme secretion and absorption
Explanation: Saprotrophs feed on dead and decaying organic material, acting as decomposers. They release enzymes outside their body to break complex organic substances into simpler soluble molecules. These dissolved nutrients are then absorbed across the body surface. This strategy is a classic example of absorptive heterotrophy and is common in many fungi and some bacteria. It plays a critical role in nutrient recycling in ecosystems. Therefore, saprotrophy involves external digestion of dead matter followed by absorption.
139. Which statement best defines a heterotroph in nutritional classification?
ⓐ. An organism that produces its own organic food from $CO_2$ and $H_2O$
ⓑ. An organism that depends on pre-formed organic substances as a source of nutrition
ⓒ. An organism that uses only inorganic oxidation for energy but never uses organic carbon
ⓓ. An organism that obtains food only by photosynthesis
Correct Answer: An organism that depends on pre-formed organic substances as a source of nutrition
Explanation: Heterotrophs cannot synthesize all required organic molecules from inorganic raw materials as their primary strategy. Instead, they rely on organic food obtained from other organisms or organic matter. This dependence can occur through ingestion (as in animals), absorption (as in fungi), or other heterotrophic modes. Because it is a fundamental life strategy, heterotrophy is central in separating major kingdoms. It also determines ecological roles such as consumer or decomposer. Hence, a heterotroph depends on pre-formed organic substances for nutrition.
140. Which nutritional match is correctly paired and is commonly used in kingdom-level separation?
ⓐ. Animalia — ingestive heterotrophy
ⓑ. Plantae — absorptive heterotrophy
ⓒ. Fungi — autotrophy
ⓓ. Monera — only ingestive heterotrophy
Correct Answer: Animalia — ingestive heterotrophy
Explanation: Animals characteristically obtain food by ingestion and digest it internally, which is ingestive heterotrophy. This nutritional mode aligns with their complex body organization and active feeding behavior. It provides a clear functional basis to separate animals from fungi (absorptive heterotrophs) and plants (primarily autotrophs). While Monera shows multiple nutritional strategies, Animalia is consistently defined by ingestion at the kingdom level. Therefore, “Animalia — ingestive heterotrophy” is the correct match used for classification.
141. Which statement best describes the cellular nature of organisms placed in Kingdom Monera?
ⓐ. They are eukaryotic and always multicellular.
ⓑ. They possess a true nucleus and membrane-bound organelles.
ⓒ. They have tissue-level organisation with complex organs.
ⓓ. They are prokaryotic, lacking a true nucleus and membrane-bound organelles.
Correct Answer: They are prokaryotic, lacking a true nucleus and membrane-bound organelles.
Explanation: Organisms of Kingdom Monera have a prokaryotic cellular plan. Their genetic material is not enclosed by a nuclear membrane, so they do not have a true nucleus. They also lack membrane-bound organelles like mitochondria and Golgi bodies. Cellular functions occur in the cytoplasm and on the plasma membrane. This basic structural simplicity is a key criterion for their separate placement. Hence, Monera are prokaryotic without a true nucleus and membrane-bound organelles.
142. In Monerans, the region containing genetic material without a nuclear membrane is called:
ⓐ. Nucleolus
ⓑ. Nucleoid
ⓒ. Nucleoplasm
ⓓ. Chromatin body
Correct Answer: Nucleoid
Explanation: In prokaryotes, DNA is not enclosed within a nucleus. Instead, it lies in an irregular region of the cytoplasm known as the nucleoid. This region contains the main circular chromosome and is not bounded by a membrane. The nucleoid is a defining structural feature of prokaryotic cells. It reflects their simpler cellular organization compared to eukaryotes. Therefore, the DNA-containing region is called the nucleoid.
143. Which component is typically absent in Monerans but present in eukaryotic cells?
ⓐ. Cytoplasm
ⓑ. Ribosomes
ⓒ. Plasma membrane
ⓓ. Membrane-bound organelles
Correct Answer: Membrane-bound organelles
Explanation: Monerans are prokaryotic and lack internal membrane-bound compartments. They do not possess organelles such as mitochondria, endoplasmic reticulum, or Golgi apparatus. However, they do have cytoplasm, ribosomes, and a plasma membrane essential for basic life processes. Absence of membrane-bound organelles is central to the prokaryotic-eukaryotic distinction. This also explains why many metabolic functions in Monerans occur at the plasma membrane. Hence, membrane-bound organelles are typically absent in Monerans.
144. The most common mode of reproduction in Kingdom Monera is:
ⓐ. Budding
ⓑ. Fragmentation
ⓒ. Binary fission
ⓓ. Formation of seeds
Correct Answer: Binary fission
Explanation: Monerans primarily reproduce asexually. The most common method is binary fission, where a single cell replicates its DNA and divides into two genetically similar daughter cells. This process is efficient and matches their unicellular prokaryotic organization. It allows rapid population increase under favorable conditions. Because reproduction is a key biological character, this dominance is important for understanding the group. Therefore, binary fission is the most common reproductive mode in Monera.
145. Which statement correctly represents the ribosomes found in typical moneran cells?
ⓐ. 80S ribosomes in cytoplasm
ⓑ. 70S ribosomes in cytoplasm
ⓒ. 60S ribosomes only in nucleus
ⓓ. No ribosomes are present
Correct Answer: 70S ribosomes in cytoplasm
Explanation: Monerans possess ribosomes for protein synthesis, despite lacking membrane-bound organelles. Their ribosomes are typically 70S type, which are smaller than the 80S ribosomes of eukaryotic cytoplasm. These 70S ribosomes lie freely in the cytoplasm and carry out translation. Ribosome type is an important cellular character distinguishing prokaryotes from eukaryotes. Hence, moneran cells typically contain 70S ribosomes in the cytoplasm.
146. Which feature best supports the statement that monerans are structurally simpler than eukaryotes?
ⓐ. Presence of a nuclear membrane
ⓑ. Presence of mitochondria and Golgi bodies
ⓒ. Presence of DNA and ribosomes
ⓓ. Lack of membrane-bound organelles and true nucleus
Correct Answer: Lack of membrane-bound organelles and true nucleus
Explanation: Structural simplicity in monerans is due to absence of a true nucleus and internal membrane-bound organelles. Without compartmentalization, many processes occur directly in the cytoplasm or at the plasma membrane. This contrasts with eukaryotes, where organelles allow specialized cellular regions and higher complexity. The prokaryotic plan thus represents a fundamental level of organization. This criterion is central to their classification in Monera. Therefore, lack of true nucleus and membrane-bound organelles supports their simpler structure.
147. Which statement about the cell wall in many monerans is correct?
ⓐ. It is always made of cellulose.
ⓑ. It is absent in all monerans.
ⓒ. It is commonly made of peptidoglycan in bacteria.
ⓓ. It is always made of chitin.
Correct Answer: It is commonly made of peptidoglycan in bacteria.
Explanation: Many monerans, especially bacteria, possess a rigid cell wall that provides shape and protection. The common bacterial cell wall component is peptidoglycan, a unique structural polymer. This feature helps in recognizing bacterial prokaryotes and has major biological significance. It contributes to resistance against osmotic pressure and supports survival in varied habitats. Cell wall composition is a useful structural character in classification. Hence, peptidoglycan is commonly present in bacterial cell walls.
148. Which characteristic best explains why monerans can show very rapid population growth?
ⓐ. They have a slow reproductive cycle requiring gamete fusion.
ⓑ. They reproduce mainly by simple cell division that can occur frequently under favorable conditions.
ⓒ. They depend on seed formation for reproduction.
ⓓ. They reproduce only once in their lifetime.
Correct Answer: They reproduce mainly by simple cell division that can occur frequently under favorable conditions.
Explanation: Monerans reproduce chiefly by binary fission, a simple and efficient asexual method. Under favorable conditions, cell division can occur at short intervals, leading to exponential population increase. Because no complex reproductive structures or gamete fusion is required, the process is rapid. This explains why bacterial populations can expand quickly when nutrients and temperature are suitable. Such reproductive efficiency is linked to their unicellular prokaryotic organization. Therefore, frequent simple cell division supports rapid population growth.
149. Which statement correctly links Monera with cellular-level organisation?
ⓐ. Members show organ-system level organisation.
ⓑ. Members show tissue-level organisation.
ⓒ. Members show cellular level organisation, mostly as unicellular forms.
ⓓ. Members show embryo development with specialized organs.
Correct Answer: Members show cellular level organisation, mostly as unicellular forms.
Explanation: Monerans are primarily unicellular organisms, so their organization is at the cellular level. They do not form tissues or organs, which are features of multicellular eukaryotes. Each moneran cell independently performs all essential life processes. This cellular-level organization is a key criterion for placing them as a separate kingdom. It also explains their simpler structure and functional organization. Hence, Monera show cellular-level organisation, mostly as unicellular forms.
150. Which feature is most directly responsible for the absence of compartmentalized organelles in monerans?
ⓐ. Presence of a rigid cell wall
ⓑ. Presence of cilia and flagella in all members
ⓒ. Presence of chlorophyll in every moneran
ⓓ. Absence of internal membrane-bound organelles as part of the prokaryotic cell plan
Correct Answer: Absence of internal membrane-bound organelles as part of the prokaryotic cell plan
Explanation: Monerans follow a prokaryotic cellular plan that lacks internal membrane-bound organelles. Their cytoplasm does not have compartments like mitochondria or endoplasmic reticulum. As a result, many biochemical processes occur in the cytoplasm or are associated with the plasma membrane. This is a fundamental structural feature, not dependent on habitat or nutrition alone. It explains the simpler organization of prokaryotic cells. Therefore, the prokaryotic plan itself accounts for the absence of compartmentalized organelles.
151. Which statement best captures the significance of “no membrane-bound organelles” in Monera?
ⓐ. It proves monerans have no metabolism.
ⓑ. It means all monerans must be multicellular.
ⓒ. It implies monerans cannot synthesize proteins.
ⓓ. It indicates a prokaryotic cell plan where major functions occur in cytoplasm or at the plasma membrane.
Correct Answer: It indicates a prokaryotic cell plan where major functions occur in cytoplasm or at the plasma membrane.
Explanation: Monerans lack membrane-bound organelles such as mitochondria, ER, and Golgi bodies. Therefore, many biochemical processes that occur in organelles in eukaryotes take place in the cytoplasm or on the plasma membrane in monerans. This absence reflects their prokaryotic organization and simpler internal compartmentalization. It does not mean they lack metabolism; instead, it changes where reactions occur. This is a key structural basis for separating Monera from eukaryotic kingdoms. Hence, it signifies a prokaryotic plan with functions in cytoplasm or at the membrane.
152. In the absence of mitochondria, where does aerobic respiration mainly occur in many bacteria?
ⓐ. Nucleoid region
ⓑ. Plasma membrane (including its infoldings/enzymatic sites)
ⓒ. Cell wall layers
ⓓ. Ribosomes
Correct Answer: Plasma membrane (including its infoldings/enzymatic sites)
Explanation: Bacteria do not possess mitochondria, so the enzymes of the electron transport chain are located on the plasma membrane. This membrane serves as the site for oxidative phosphorylation and ATP generation in aerobic bacteria. The arrangement allows respiration to proceed despite lack of organelles. It demonstrates how key functions are associated with the cell membrane in prokaryotes. This is a direct consequence of having no membrane-bound organelles. Therefore, aerobic respiration mainly occurs on the plasma membrane.
153. The absence of Golgi apparatus in monerans most directly implies that:
ⓐ. They cannot secrete any substances
ⓑ. They cannot reproduce
ⓒ. They have no genetic material
ⓓ. They lack internal membrane-based packaging and modification compartments
Correct Answer: They lack internal membrane-based packaging and modification compartments
Explanation: The Golgi apparatus is a membrane-bound organelle involved in processing, packaging, and sorting cellular products in eukaryotes. Monerans lack such membrane-bound compartments, so they do not have a Golgi-based internal trafficking system. This does not prevent them from producing proteins or releasing substances, but the organization is simpler and not compartmentalized. The absence reflects the prokaryotic cell plan. It highlights why monerans are structurally simpler than eukaryotes. Hence, absence of Golgi implies lack of internal membrane-based packaging compartments.
154. Which statement is correct regarding lysosomes in monerans?
ⓐ. Lysosomes are present and help in intracellular digestion.
ⓑ. Lysosomes are absent because they are membrane-bound organelles.
ⓒ. Lysosomes replace ribosomes in monerans.
ⓓ. Lysosomes are present only in photosynthetic monerans.
Correct Answer: Lysosomes are absent because they are membrane-bound organelles.
Explanation: Lysosomes are membrane-bound organelles typically found in eukaryotic cells, containing digestive enzymes. Monerans lack membrane-bound organelles as part of their prokaryotic organization. Therefore, they do not have lysosomes as distinct compartments. This absence is consistent with the overall lack of internal membrane compartmentalization in Monera. Cellular breakdown and digestion-related processes, when present, occur without lysosomal structures. Hence, lysosomes are absent in monerans because they are membrane-bound organelles.
155. A direct consequence of lacking endoplasmic reticulum in Monera is that:
ⓐ. Protein synthesis cannot occur
ⓑ. Ribosomes cannot function
ⓒ. There is no membrane-based internal transport network like in eukaryotic cells
ⓓ. DNA cannot replicate
Correct Answer: There is no membrane-based internal transport network like in eukaryotic cells
Explanation: Endoplasmic reticulum is a membrane-bound organelle forming a network for synthesis and transport of proteins and lipids in eukaryotes. Monerans lack ER, so they do not have this internal compartmentalized transport system. However, they still synthesize proteins using ribosomes in the cytoplasm. The absence mainly reflects simpler cellular organization and different pathways of product handling. This is a hallmark of prokaryotic cells. Therefore, lacking ER means no membrane-based internal transport network as seen in eukaryotes.
156. In monerans, functions that are typically compartmentalized in eukaryotes are mainly performed by:
ⓐ. Plasma membrane and cytoplasm
ⓑ. Nucleus and nucleolus
ⓒ. Chloroplast and mitochondria
ⓓ. Golgi bodies and lysosomes
Correct Answer: Plasma membrane and cytoplasm
Explanation: Monerans do not possess membrane-bound organelles, so compartmentalization like mitochondria or Golgi is absent. Many essential biochemical reactions occur in the cytoplasm, while processes such as electron transport may be associated with the plasma membrane. This arrangement allows normal cellular functioning despite simpler structure. It is a key reason monerans are classified as prokaryotes. The plasma membrane becomes especially important for energy-related pathways. Hence, plasma membrane and cytoplasm carry out functions that are compartmentalized in eukaryotes.
157. Which feature best differentiates monerans from eukaryotes in terms of intracellular compartmentalization?
ⓐ. Presence of cytoplasm
ⓑ. Presence of DNA
ⓒ. Presence of ribosomes
ⓓ. Presence of membrane-bound organelles
Correct Answer: Presence of membrane-bound organelles
Explanation: Eukaryotic cells have membrane-bound organelles that create internal compartments for specialized functions. Monerans lack these organelles and therefore do not show such compartmentalization. Cytoplasm, DNA, and ribosomes occur in both groups, so they cannot separate them at this level. The presence or absence of membrane-bound organelles is therefore a fundamental distinguishing character. It influences where cellular processes occur and the overall complexity of the cell. Hence, membrane-bound organelles are the key differentiator for compartmentalization.
158. The absence of chloroplasts in photosynthetic monerans indicates that their photosynthetic pigments are located in:
ⓐ. Nucleoid region only
ⓑ. Plasma membrane-associated structures
ⓒ. Cell wall peptidoglycan layers
ⓓ. Ribosomal subunits
Correct Answer: Plasma membrane-associated structures
Explanation: Photosynthetic monerans (such as cyanobacteria) do not have chloroplasts because chloroplasts are membrane-bound organelles found in eukaryotes. Their photosynthetic pigments are associated with internal membrane systems derived from the plasma membrane. This allows capture of light energy and photosynthetic electron transport without chloroplasts. It reflects the prokaryotic plan where functions occur at membrane sites rather than in organelles. This is consistent with the “no membrane-bound organelles” character. Therefore, pigments are located in plasma membrane-associated structures.
159. Which statement is most accurate about protein synthesis in Monera despite lacking rough endoplasmic reticulum?
ⓐ. Protein synthesis is impossible without rough ER.
ⓑ. Proteins are synthesized on free ribosomes in the cytoplasm.
ⓒ. Proteins are synthesized inside mitochondria.
ⓓ. Proteins are synthesized only in the cell wall.
Correct Answer: Proteins are synthesized on free ribosomes in the cytoplasm.
Explanation: Monerans possess 70S ribosomes in their cytoplasm that carry out protein synthesis. Rough endoplasmic reticulum is a eukaryotic organelle and is absent in monerans. However, ribosomes do not require ER to synthesize proteins; ER mainly helps in compartmentalized processing and transport in eukaryotes. In monerans, proteins are produced in the cytosol and handled without ER-based pathways. This aligns with their simpler, non-compartmentalized structure. Hence, proteins are synthesized on free ribosomes in the cytoplasm.
160. Which option best explains why “no membrane-bound organelles” is considered a foundational character of Monera?
ⓐ. It directly indicates a prokaryotic organization that separates Monera from all eukaryotic kingdoms.
ⓑ. It proves monerans are always autotrophic.
ⓒ. It proves monerans cannot survive in extreme habitats.
ⓓ. It indicates monerans reproduce only sexually.
Correct Answer: It directly indicates a prokaryotic organization that separates Monera from all eukaryotic kingdoms.
Explanation: The defining cellular plan of Monera is prokaryotic, and absence of membrane-bound organelles is a core feature of this plan. This character separates monerans from eukaryotic kingdoms where organelles create compartmentalization and higher complexity. It influences major cellular functions, including energy production and internal processing of molecules. Because it is stable and fundamental, it is used as a primary classification criterion. It is not linked to a single nutrition type or reproductive mode. Therefore, it is foundational because it signals prokaryotic organization distinct from eukaryotes.
161. The ribosomes present in typical moneran cells are mainly:
ⓐ. 80S
ⓑ. 60S
ⓒ. 70S
ⓓ. 90S
Correct Answer: 70S
Explanation: Monerans are prokaryotic organisms and characteristically possess 70S ribosomes. These ribosomes are smaller than the 80S ribosomes found in the cytoplasm of eukaryotic cells. They are the sites of protein synthesis and occur freely in the cytoplasm. Ribosome type is a useful cellular character for distinguishing major groups. This feature remains consistent across most bacteria and cyanobacteria. Hence, moneran cells mainly have 70S ribosomes.
162. The “70S” ribosome in prokaryotes is formed by the association of:
ⓐ. 50S and 30S subunits
ⓑ. 60S and 40S subunits
ⓒ. 40S and 30S subunits
ⓓ. 80S and 70S subunits
Correct Answer: 50S and 30S subunits
Explanation: Prokaryotic ribosomes are 70S and are composed of two subunits: a larger 50S and a smaller 30S. These subunits assemble on mRNA during translation to synthesize proteins. The S value refers to sedimentation behavior and reflects size and shape, not simple addition. This subunit composition is a standard prokaryotic feature and supports their cellular distinction from eukaryotes. It is therefore a key concept under Monera cell biology. Hence, 70S ribosomes consist of 50S and 30S subunits.
163. A correct statement about 70S ribosomes that supports monerans being prokaryotic is:
ⓐ. 70S ribosomes are enclosed within a nuclear membrane.
ⓑ. 70S ribosomes are absent from the cytoplasm.
ⓒ. 70S ribosomes are characteristic of prokaryotic cytoplasm for protein synthesis.
ⓓ. 70S ribosomes are larger than 80S ribosomes.
Correct Answer: 70S ribosomes are characteristic of prokaryotic cytoplasm for protein synthesis.
Explanation: Monerans synthesize proteins using ribosomes that are present freely in the cytoplasm. The characteristic ribosome type is 70S, which is typical of prokaryotes. This supports their placement as prokaryotic organisms distinct from eukaryotes. Ribosome type is stable and widely used as a cellular character in broad classification. The 70S ribosome performs translation by reading mRNA and assembling amino acids into polypeptides. Therefore, 70S ribosomes being characteristic of prokaryotic cytoplasm supports monerans as prokaryotes.
164. The “S” in 70S refers to:
ⓐ. Surface area of the ribosome
ⓑ. Size measured in micrometers
ⓒ. Speed of protein synthesis
ⓓ. Sedimentation coefficient determined by ultracentrifugation
Correct Answer: Sedimentation coefficient determined by ultracentrifugation
Explanation: The S value stands for Svedberg unit, which represents sedimentation rate in an ultracentrifuge. It depends on particle size, shape, and density rather than only mass. This is why 50S + 30S forms a 70S ribosome and not an arithmetic sum. The sedimentation coefficient is a standard physical basis for naming ribosomal subunits. This concept is important for interpreting why ribosomes are classified as 70S or 80S. Hence, “S” refers to the sedimentation coefficient measured by ultracentrifugation.
165. Which cellular process occurs on 70S ribosomes in monerans?
ⓐ. Protein synthesis (translation)
ⓑ. DNA replication
ⓒ. Photosynthesis pigment formation
ⓓ. Cell wall peptidoglycan cross-linking
Correct Answer: Protein synthesis (translation)
Explanation: Ribosomes are the cellular structures responsible for translation, the process of building proteins from mRNA templates. In monerans, this function is carried out by 70S ribosomes present in the cytoplasm. They bind mRNA and tRNA and catalyze peptide bond formation through coordinated subunit activity. This role is universal for ribosomes across all life forms, though ribosome type differs between groups. The 70S ribosome is therefore central to moneran protein production. Hence, protein synthesis (translation) occurs on 70S ribosomes.
166. A key comparison of ribosomes that helps separate monerans from eukaryotic cytoplasm is:
ⓐ. Monerans have 80S ribosomes, eukaryotes have 70S ribosomes.
ⓑ. Monerans lack ribosomes, eukaryotes have ribosomes.
ⓒ. Monerans have 70S ribosomes, while eukaryotic cytoplasm typically has 80S ribosomes.
ⓓ. Both have only 60S ribosomes in cytoplasm.
Correct Answer: Monerans have 70S ribosomes, while eukaryotic cytoplasm typically has 80S ribosomes.
Explanation: Ribosome type is a classic cellular character distinguishing prokaryotes from eukaryotes. Monerans, being prokaryotic, possess 70S ribosomes in their cytoplasm. Eukaryotic cytoplasm typically contains 80S ribosomes, reflecting a different subunit composition. This difference supports the separation of Monera from eukaryotic kingdoms in broad classification. It also aligns with the prokaryotic plan of simpler cellular organization. Therefore, monerans have 70S ribosomes while eukaryotic cytoplasm has 80S ribosomes.
167. In monerans, 70S ribosomes are most commonly found:
ⓐ. Free in the cytoplasm
ⓑ. Inside the nucleus
ⓒ. Inside mitochondria
ⓓ. Inside chloroplasts
Correct Answer: Free in the cytoplasm
Explanation: Monerans lack a true nucleus and membrane-bound organelles such as mitochondria and chloroplasts. Their ribosomes therefore occur freely in the cytoplasm, where they carry out protein synthesis. This free distribution matches the non-compartmentalized prokaryotic cell plan. The presence of cytoplasmic 70S ribosomes is a consistent structural feature of bacteria and cyanobacteria. It supports their placement under Monera as prokaryotes. Hence, 70S ribosomes are most commonly free in the cytoplasm.
168. Which statement correctly explains why 70S ribosomes are an important feature in classifying Monera?
ⓐ. They indicate the organism is multicellular with tissues.
ⓑ. They show that the organism lacks DNA.
ⓒ. They prove the organism is always autotrophic.
ⓓ. They reflect the prokaryotic cellular organization typical of Monera.
Correct Answer: They reflect the prokaryotic cellular organization typical of Monera.
Explanation: Ribosome type is a stable cellular characteristic linked to fundamental cell organization. The presence of 70S ribosomes is typical of prokaryotic cells and supports separating Monera from eukaryotic kingdoms. This feature aligns with other prokaryotic traits, such as absence of a true nucleus and membrane-bound organelles. Because it is consistent and widely observed in monerans, it is useful as supportive evidence in classification. It also relates directly to the protein synthesis machinery of prokaryotes. Therefore, 70S ribosomes reflect the prokaryotic organization typical of Monera.
169. Which option best links 70S ribosomes with moneran gene expression?
ⓐ. 70S ribosomes enable translation to occur in the cytoplasm without nuclear separation.
ⓑ. 70S ribosomes prevent protein synthesis in monerans.
ⓒ. 70S ribosomes store hereditary material in monerans.
ⓓ. 70S ribosomes form a nuclear envelope during division.
Correct Answer: 70S ribosomes enable translation to occur in the cytoplasm without nuclear separation.
Explanation: Monerans do not have a nuclear membrane, so the genetic material and ribosomes are in the same cellular space. Their 70S ribosomes carry out translation directly in the cytoplasm. This organization supports efficient protein synthesis and is a hallmark of prokaryotic gene expression. It also explains why transcription and translation can be closely linked in prokaryotes. The 70S ribosomes are therefore central to moneran protein production in a non-compartmentalized cell. Hence, 70S ribosomes enable cytoplasmic translation without nuclear separation.
170. A student claims “70S means 50S + 30S must equal 80S, so the term is incorrect.” The best correction is:
ⓐ. 70S is used only for eukaryotic ribosomes.
ⓑ. S values are not additive; they depend on shape and sedimentation behavior.
ⓒ. 50S and 30S are actually 40S and 30S in prokaryotes.
ⓓ. 70S ribosomes are made of 60S and 10S subunits.
Correct Answer: S values are not additive; they depend on shape and sedimentation behavior.
Explanation: The Svedberg unit (S) measures how fast a particle sediments during ultracentrifugation. It depends on size, shape, and density, so it is not an arithmetic sum. Therefore, the association of 50S and 30S subunits forms a 70S ribosome, not 80S. This physical basis explains the naming of ribosomes and is important for understanding prokaryote–eukaryote differences. The student’s mistake is assuming simple addition of S values. Hence, S values are not additive because they reflect sedimentation behavior.
171. The most common asexual method of reproduction in Kingdom Monera is:
ⓐ. Binary fission
ⓑ. Fragmentation
ⓒ. Spore formation as the only method
ⓓ. Seed formation
Correct Answer: Binary fission
Explanation: Monerans are mainly unicellular prokaryotes and typically multiply by binary fission. In this process, the DNA replicates and the cell divides into two genetically similar daughter cells. It is a simple, efficient method suited to their cellular-level organization. Under favorable conditions, binary fission can occur rapidly, leading to quick population increase. This method is therefore considered the dominant reproductive strategy in Monera. Hence, binary fission is the most common asexual method.
172. In binary fission, the immediate result of one division is:
ⓐ. Three daughter cells
ⓑ. Two daughter cells similar to the parent cell
ⓒ. A multicellular embryo
ⓓ. Formation of gametes
Correct Answer: Two daughter cells similar to the parent cell
Explanation: Binary fission is an asexual process where one parent cell splits into two. Before division, the genetic material is replicated so that each daughter cell receives a copy. Because there is no fusion of gametes, the daughter cells are typically genetically similar to the parent. This suits unicellular organisms that reproduce quickly. It also explains rapid numerical increase in bacterial populations. Therefore, the immediate result is two daughter cells similar to the parent.
173. A key reason binary fission enables rapid increase in moneran population is that it:
ⓐ. Requires formation of specialized reproductive organs
ⓑ. Depends on pollination
ⓒ. Needs fusion of gametes each time
ⓓ. Is a simple cell-division process that can repeat frequently under suitable conditions
Correct Answer: Is a simple cell-division process that can repeat frequently under suitable conditions
Explanation: Binary fission is structurally simple and does not require complex reproductive structures. When nutrients and conditions are favorable, a moneran cell can divide repeatedly at short intervals. Each division doubles the number of cells, leading to exponential growth. This efficiency is linked to their unicellular organization and asexual reproduction. Because the process is straightforward, it supports rapid population expansion. Hence, frequent repetition of simple cell division explains rapid increase.
174. Which statement best describes the genetic similarity expected among offspring produced by binary fission?
ⓐ. Offspring are usually genetically identical to the parent cell except for occasional variations.
ⓑ. Offspring are produced only after meiosis, so they are genetically different.
ⓒ. Offspring always contain half the genetic material of the parent.
ⓓ. Offspring are genetically unrelated to the parent.
Correct Answer: Offspring are usually genetically identical to the parent cell except for occasional variations.
Explanation: Binary fission is an asexual reproductive method with no gamete fusion. The DNA is replicated and distributed into daughter cells, so the genetic makeup is typically the same as the parent. However, small variations can arise due to errors during DNA replication or other changes in genetic material. This is why bacterial populations can be largely uniform yet still show variation over time. The core expectation remains high similarity among offspring. Therefore, offspring are usually genetically identical except for occasional variations.
175. In monerans, what is the relationship between cell division and reproduction?
ⓐ. Cell division does not produce new individuals.
ⓑ. Cell division is typically the same process as reproduction in many unicellular monerans.
ⓒ. Cell division occurs only in multicellular tissues.
ⓓ. Cell division happens only during sexual reproduction.
Correct Answer: Cell division is typically the same process as reproduction in many unicellular monerans.
Explanation: Most monerans are unicellular, so when a cell divides, it directly produces new individuals. This makes cell division and reproduction essentially the same event in many monerans. The process is rapid and does not require specialized reproductive organs. This is a key reason monerans can multiply quickly under favorable conditions. It also aligns with their cellular-level organization. Hence, cell division commonly serves as reproduction in unicellular monerans.
176. Which process is NOT a typical asexual division method in monerans?
ⓐ. Binary fission
ⓑ. Simple cell division
ⓒ. Mitosis with spindle apparatus
ⓓ. Asexual multiplication without gamete fusion
Correct Answer: Mitosis with spindle apparatus
Explanation: Monerans are prokaryotic and do not have the eukaryotic nuclear division machinery. Mitosis involves a spindle apparatus and organized chromosome segregation within a nucleus, which is characteristic of eukaryotic cells. Monerans instead reproduce mainly by simple division such as binary fission. Their DNA replication and segregation occur without a mitotic spindle. Therefore, mitosis with spindle apparatus is not typical of monerans.
177. A consequence of asexual division as the main reproductive method in monerans is that:
ⓐ. Variation is impossible in moneran populations
ⓑ. Populations can expand quickly while maintaining largely similar genetic makeup
ⓒ. Reproduction always requires two parent cells
ⓓ. Offspring always have half the chromosome number
Correct Answer: Populations can expand quickly while maintaining largely similar genetic makeup
Explanation: Asexual division like binary fission is quick and efficient, so populations can increase rapidly. Because there is no gamete fusion, the genetic makeup of offspring remains largely similar to the parent cell. This supports stability of successful traits across generations. Occasional variations may still occur, but the overall genetic similarity remains high. Rapid multiplication is therefore a key ecological advantage of monerans. Hence, quick expansion with largely similar genetic makeup is a major consequence.
178. During binary fission, equal distribution of genetic material is ensured mainly because:
ⓐ. The nucleus divides by mitosis
ⓑ. Chromosomes pair and cross over
ⓒ. Gametes are formed and fuse
ⓓ. DNA is replicated before cell division and then segregated into the two forming cells
Correct Answer: DNA is replicated before cell division and then segregated into the two forming cells
Explanation: Binary fission involves replication of the DNA so that two copies are produced. As the cell prepares to divide, these copies are separated and positioned so each daughter cell receives one. This ensures that both daughter cells inherit genetic material necessary for survival. The process is simpler than mitosis but still achieves accurate distribution. It is central to asexual reproduction in prokaryotes. Therefore, replication followed by segregation ensures equal distribution.
179. Which statement best reflects why asexual division is sufficient for many monerans?
ⓐ. Their unicellular body plan allows multiplication through simple division without specialized reproductive organs.
ⓑ. They must always form flowers for reproduction.
ⓒ. They require complex embryonic development to produce new individuals.
ⓓ. They cannot reproduce under any condition.
Correct Answer: Their unicellular body plan allows multiplication through simple division without specialized reproductive organs.
Explanation: Monerans are mostly unicellular organisms where one cell represents the whole individual. Therefore, simple division produces new independent individuals without needing reproductive tissues or organs. This makes asexual reproduction highly efficient and well-suited to their structure. It supports rapid multiplication and colonization of habitats. The process is also energetically less demanding than complex sexual reproduction. Hence, unicellular organization makes asexual division sufficient for many monerans.
180. A student concludes: “Because monerans reproduce mainly by asexual division, they cannot increase in number quickly.” The correct concept is:
ⓐ. Asexual division is slow, so population growth is limited.
ⓑ. Asexual division prevents any multiplication.
ⓒ. Asexual division like binary fission can be very rapid, enabling fast population increase.
ⓓ. Asexual division occurs only once in a lifetime.
Correct Answer: Asexual division like binary fission can be very rapid, enabling fast population increase.
Explanation: Binary fission is a simple and efficient asexual process that can occur frequently under favorable conditions. Each division doubles the number of cells, so populations can grow exponentially. This is why bacterial populations can rise quickly when nutrients are available. Asexual division does not limit growth; instead, it often accelerates it due to low complexity. This rapid multiplication is a key biological advantage of monerans. Therefore, asexual division can be very rapid and supports fast population increase.
181. Archaebacteria are best known for their ability to:
ⓐ. Live only as parasites inside animals
ⓑ. Form true tissues and organs
ⓒ. Survive and grow in extreme habitats
ⓓ. Perform seed-based reproduction
Correct Answer: Survive and grow in extreme habitats
Explanation: Archaebacteria are a group of prokaryotes adapted to environments that are hostile for many other organisms. They can thrive in conditions such as very high salinity, high temperature, or anaerobic marshy habitats. Their survival is linked to distinctive cellular and biochemical features that allow stability under such extremes. This ecological specialization is a key reason they are discussed separately within Monera. It also highlights their unique evolutionary adaptations. Hence, archaebacteria are best known for thriving in extreme habitats.
182. Halophiles (a group of archaebacteria) are typically found in:
ⓐ. Hot sulfur springs
ⓑ. Highly saline environments like salt lakes
ⓒ. Acidic forest soils only
ⓓ. Freshwater ponds only
Correct Answer: Highly saline environments like salt lakes
Explanation: Halophiles are archaebacteria adapted to live in high-salt conditions. They occur in salt lakes, salt pans, and other hypersaline habitats where many organisms cannot survive. Their cellular machinery is adapted to maintain osmotic balance and stability in salty surroundings. This extreme habitat preference is a defining ecological trait of halophiles. It also explains why they are grouped as a specialized archaebacterial form. Therefore, halophiles are found in highly saline environments.
183. Thermoacidophiles are archaebacteria that typically thrive in:
ⓐ. Cold oceans and polar ice
ⓑ. Neutral pH freshwater streams
ⓒ. High temperature and acidic conditions
ⓓ. Dry deserts with low humidity
Correct Answer: High temperature and acidic conditions
Explanation: Thermoacidophiles are adapted to two extremes simultaneously—high heat and low pH. They are commonly associated with hot acidic habitats such as certain hot springs. Their enzymes and cell components remain functional despite conditions that denature proteins in many organisms. This adaptation demonstrates the extremophilic nature of many archaebacteria. It is an important example under “archaebacteria in extreme habitats.” Hence, thermoacidophiles thrive in hot and acidic conditions.
184. Methanogens are archaebacteria commonly found in:
ⓐ. Aerobic mountain air
ⓑ. Chlorinated swimming pools
ⓒ. Desert sand dunes
ⓓ. Anaerobic habitats like marshes and the rumen of cattle
Correct Answer: Anaerobic habitats like marshes and the rumen of cattle
Explanation: Methanogens live in oxygen-free environments and carry out anaerobic metabolism. They are commonly present in marshy areas where decomposition occurs without oxygen. They also inhabit the rumen of cattle and similar digestive tracts, where conditions are anaerobic. Their activity results in the production of methane gas as a metabolic end product. This habitat preference is a key feature of methanogens among archaebacteria. Therefore, methanogens are found in anaerobic habitats like marshes and rumen.
185. The term “extremophiles” is most appropriately used for many archaebacteria because they:
ⓐ. Cannot tolerate any change in environment
ⓑ. Grow best under conditions lethal to many other organisms
ⓒ. Live only in moderate temperature and pH
ⓓ. Are always multicellular
Correct Answer: Grow best under conditions lethal to many other organisms
Explanation: Extremophiles are organisms that thrive in extreme environmental conditions. Many archaebacteria are extremophiles, growing in very salty, very hot, highly acidic, or strictly anaerobic habitats. These conditions are often harmful or lethal to most organisms. Their survival reflects specialized biochemical and cellular adaptations. This property makes archaebacteria a notable group within prokaryotes. Hence, they are called extremophiles because they grow best under conditions lethal to many others.
186. Which group of archaebacteria is associated with methane production?
ⓐ. Halophiles
ⓑ. Thermoacidophiles
ⓒ. Methanogens
ⓓ. Cyanobacteria
Correct Answer: Methanogens
Explanation: Methanogens are archaebacteria that produce methane as a metabolic by-product. They function in anaerobic conditions where they help break down organic matter. This methane production is the basis of their name and is an important ecological process in wetlands and animal digestive systems. Their specialized metabolism distinguishes them from other archaebacterial groups like halophiles and thermoacidophiles. This is a core concept under archaebacteria in extreme habitats. Therefore, methane producers are methanogens.
187. A salt pan with very high salinity is most likely to support the growth of:
ⓐ. Halophilic archaebacteria
ⓑ. Methanogens only
ⓒ. Typical green algae only
ⓓ. Flowering plants only
Correct Answer: Halophilic archaebacteria
Explanation: Extremely saline habitats create strong osmotic stress that most organisms cannot tolerate. Halophilic archaebacteria are specifically adapted to survive and grow under such high-salt conditions. Their cellular systems maintain stability and function despite the salt concentration. This makes them common inhabitants of salt pans and salt lakes. Their presence illustrates the “extreme habitat” specialization of archaebacteria. Hence, halophilic archaebacteria are most likely to grow in salt pans.
188. Hot acidic springs are most suitable for archaebacteria known as:
ⓐ. Halophiles
ⓑ. Thermoacidophiles
ⓒ. Methanogens
ⓓ. Mycoplasma
Correct Answer: Thermoacidophiles
Explanation: Hot acidic springs combine high temperature with low pH, creating a harsh environment. Thermoacidophiles are adapted to such conditions and can maintain enzyme activity and membrane stability despite heat and acidity. This specialization is typical of certain archaebacterial groups. Their habitat preference is a clear example of archaebacterial extremophily. Such organisms often dominate where other microbes fail to survive. Therefore, thermoacidophiles are most suited for hot acidic springs.
189. Which statement best explains why methanogens are common in the rumen of cattle?
ⓐ. The rumen is highly oxygenated, favoring aerobic archaea.
ⓑ. The rumen provides a cold, salty environment needed by halophiles.
ⓒ. The rumen is anaerobic, supporting methane-producing metabolism.
ⓓ. The rumen is strongly acidic like hot springs.
Correct Answer: The rumen is anaerobic, supporting methane-producing metabolism.
Explanation: Methanogens require oxygen-free conditions to carry out their characteristic metabolism. The rumen of cattle is an anaerobic environment where microbial digestion of cellulose and other materials occurs without oxygen. This supports methanogenic pathways that release methane gas. The availability of organic substrates and anaerobic conditions makes the rumen a suitable niche. This ecological association is a standard example of methanogen habitat. Hence, methanogens are common in rumen because it is anaerobic and supports methane production.
190. The best overall match of archaebacterial group with its extreme habitat is:
ⓐ. Halophiles—oxygen-rich mountain peaks
ⓑ. Methanogens—well-aerated freshwater lakes
ⓒ. Thermoacidophiles—hot, acidic environments
ⓓ. Thermoacidophiles—high-salinity salt pans
Correct Answer: Thermoacidophiles—hot, acidic environments
Explanation: Thermoacidophiles are defined by their ability to thrive at high temperatures and low pH. This directly matches hot, acidic environments such as certain thermal springs. The other pairings mismatch the required conditions for the groups mentioned. Archaebacterial groups are strongly associated with specific extreme habitats that suit their adaptations. Correct matching therefore depends on recognizing the defining environmental extremes. Hence, thermoacidophiles are correctly matched with hot, acidic environments.
191. A key feature that helps archaebacteria survive extreme environments is their:
ⓐ. Cell wall that differs from typical bacterial cell wall
ⓑ. Presence of chloroplasts for photosynthesis
ⓒ. Multicellular tissue organization
ⓓ. Seed-based reproduction
Correct Answer: Cell wall that differs from typical bacterial cell wall
Explanation: Archaebacteria possess cell wall structures that are chemically distinct from those of typical bacteria. This difference contributes to stability and protection under extreme conditions such as high salinity, high temperature, or acidic environments. Their wall composition is an important cellular adaptation that supports survival where many organisms fail. This feature also helps in distinguishing archaebacteria from eubacteria within prokaryotes. Because it is a fundamental structural character, it is emphasized in classification. Hence, the distinct cell wall is a key survival feature.
192. The cell wall of archaebacteria is distinct mainly because it:
ⓐ. Is made of cellulose
ⓑ. Is always absent
ⓒ. Lacks peptidoglycan typical of many bacteria
ⓓ. Is made of lignin
Correct Answer: Lacks peptidoglycan typical of many bacteria
Explanation: Typical bacterial cell walls commonly contain peptidoglycan, which provides rigidity and shape. Archaebacterial cell walls do not contain this typical peptidoglycan composition, making them chemically distinct. This difference is important in understanding their unique physiology and adaptations. It also supports their separate identity among prokaryotes. The distinction is a standard basis for discussing archaebacteria in classification. Therefore, archaebacterial walls lack typical bacterial peptidoglycan.
193. Which statement best explains the classification significance of archaebacterial cell wall differences?
ⓐ. Cell wall differences are superficial and have no biological value.
ⓑ. Cell wall composition is a stable structural character that helps distinguish major prokaryotic groups.
ⓒ. Cell wall differences depend only on daily nutrition and are unreliable.
ⓓ. Cell wall differences occur only in multicellular organisms.
Correct Answer: Cell wall composition is a stable structural character that helps distinguish major prokaryotic groups.
Explanation: Cell wall composition is a fundamental and relatively stable cellular feature. Differences in wall chemistry reflect deeper evolutionary and functional distinctions between groups. In prokaryotes, such structural characters are especially important because overall body form may be simple. The distinct wall of archaebacteria helps separate them from typical bacteria and supports their recognition as a unique group. This also relates to their ability to tolerate extreme conditions. Hence, stable cell wall composition is significant for distinguishing major prokaryotic groups.
194. A student observes a prokaryote from a hot acidic spring and wants a cell-wall clue supporting archaebacterial nature. The best clue is:
ⓐ. Presence of peptidoglycan-rich wall typical of bacteria
ⓑ. Cellulose wall like plants
ⓒ. Chitin wall like fungi
ⓓ. Cell wall lacking typical bacterial peptidoglycan
Correct Answer: Cell wall lacking typical bacterial peptidoglycan
Explanation: Hot acidic springs are typical habitats for thermoacidophilic archaebacteria. A major structural feature supporting archaebacterial identity is the absence of typical bacterial peptidoglycan in the cell wall. This distinctive wall chemistry contributes to stability and survival under extreme conditions. It also distinguishes them from eubacteria, which commonly show peptidoglycan walls. Such a clue is directly relevant when identifying prokaryotes from extreme environments. Therefore, a wall lacking typical bacterial peptidoglycan is the best clue.
195. Which comparison most accurately reflects a standard cell-wall distinction between many eubacteria and archaebacteria?
ⓐ. Eubacteria: cellulose; Archaebacteria: lignin
ⓑ. Eubacteria: peptidoglycan commonly present; Archaebacteria: peptidoglycan absent in typical form
ⓒ. Eubacteria: chitin; Archaebacteria: cellulose
ⓓ. Eubacteria: no wall; Archaebacteria: always no wall
Correct Answer: Eubacteria: peptidoglycan commonly present; Archaebacteria: peptidoglycan absent in typical form
Explanation: Many eubacteria have a cell wall that contains peptidoglycan, providing rigidity and support. Archaebacteria have a different wall composition and do not contain peptidoglycan in the typical bacterial form. This difference is a key textbook distinction used to separate these two major prokaryotic groups. It reflects deep biochemical divergence and relates to their unique adaptations. Because the cell wall is fundamental, it is reliable for classification discussion. Hence, eubacteria commonly have peptidoglycan while archaebacteria lack typical peptidoglycan.
196. Why are archaebacterial cell walls considered important for survival in extreme habitats?
ⓐ. They make archaebacteria strictly photosynthetic.
ⓑ. They enable development of true tissues and organs.
ⓒ. They provide chemical stability and protection under harsh conditions.
ⓓ. They allow formation of seeds resistant to drought.
Correct Answer: They provide chemical stability and protection under harsh conditions.
Explanation: Extreme habitats can damage cellular structures through heat, acidity, or high salt. Archaebacterial cell walls are chemically distinct and contribute to maintaining structural integrity in such conditions. This stability supports cellular survival and functioning where many organisms would be disrupted. The wall acts as a protective boundary and helps maintain cell shape and resilience. Such adaptations are part of why archaebacteria are major extremophile groups. Therefore, their cell walls provide chemical stability and protection in harsh environments.
197. Which option best states what you should NOT expect in a typical archaebacterial cell wall?
ⓐ. A chemically distinct wall compared to many bacteria
ⓑ. Structural adaptation supporting survival in extremes
ⓒ. Typical bacterial peptidoglycan as the main wall component
ⓓ. A stable outer covering supporting cell shape
Correct Answer: Typical bacterial peptidoglycan as the main wall component
Explanation: A key point about archaebacteria is that their cell wall composition differs from typical bacteria. The standard bacterial wall component peptidoglycan is commonly associated with eubacteria, not archaebacteria. Archaebacterial walls are distinct and contribute to their stability and survival in extreme habitats. They still provide shape and protection, but through different chemical composition. This difference is repeatedly used to separate them in classification discussions. Hence, typical bacterial peptidoglycan as the main component should not be expected in archaebacteria.
198. The cell wall difference between archaebacteria and eubacteria is best treated as:
ⓐ. A minor, unreliable trait that changes daily
ⓑ. A fundamental biochemical character supporting separation of major prokaryotic groups
ⓒ. A feature found only in multicellular organisms
ⓓ. A feature that depends only on habitat and not on cell chemistry
Correct Answer: A fundamental biochemical character supporting separation of major prokaryotic groups
Explanation: Cell wall chemistry is a deep biochemical feature tied to cell structure and function. Such characters are stable and informative for distinguishing major groups, especially in prokaryotes where morphological variation may be limited. The distinct wall composition in archaebacteria supports their separation from typical bacteria at a broad level. It also connects to their unique physiological resilience. Therefore, it is treated as a fundamental biochemical character. Hence, it supports separation of major prokaryotic groups.
199. A prokaryote is found in a high-salt lake. If it belongs to archaebacteria, a correct structural expectation is:
ⓐ. A cell wall with typical bacterial peptidoglycan
ⓑ. A cell wall composition distinct from typical bacteria
ⓒ. A nucleus with nuclear membrane
ⓓ. Presence of chloroplasts
Correct Answer: A cell wall composition distinct from typical bacteria
Explanation: High-salt lakes are classic habitats for halophilic archaebacteria. Archaebacteria, as a group, are characterized by cell walls that differ chemically from typical bacterial peptidoglycan walls. This distinct wall contributes to resilience and survival in extreme conditions like high salinity. As prokaryotes, they also lack a nucleus and chloroplasts, so those are not correct expectations. The most appropriate structural expectation is the distinct wall composition. Therefore, an archaebacterial prokaryote in a salt lake is expected to have a cell wall distinct from typical bacteria.
200. Which statement best summarizes the role of cell wall differences in recognizing archaebacteria in biological classification?
ⓐ. They help confirm archaebacteria as eukaryotes.
ⓑ. They are the sole criterion for placing organisms into Plantae.
ⓒ. They provide a key structural basis to distinguish archaebacteria from typical bacteria within prokaryotes.
ⓓ. They show archaebacteria cannot live in extreme habitats.
Correct Answer: They provide a key structural basis to distinguish archaebacteria from typical bacteria within prokaryotes.
Explanation: Archaebacteria are prokaryotes but differ from typical bacteria in important biochemical features, including cell wall composition. This structural difference is a standard basis for distinguishing them within the broader prokaryotic world. It is reliable because cell wall chemistry is fundamental and relatively stable. It also relates to their capacity to withstand harsh environments. Thus, cell wall differences help identify archaebacteria as a distinct prokaryotic group. Therefore, they provide a key structural basis to distinguish archaebacteria from typical bacteria.