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301. In Protista, an autotroph is best defined as an organism that:
ⓐ. Obtains food by ingesting solid particles
ⓑ. Depends only on dead organic matter for nutrition
ⓒ. Synthesizes its own organic food from inorganic substances
ⓓ. Produces methane under anaerobic conditions
Correct Answer: Synthesizes its own organic food from inorganic substances
Explanation: Autotrophs make their own food rather than depending on pre-formed organic matter. In protists, many autotrophs use inorganic carbon (mainly $CO_2$) to build organic compounds. This is a core nutritional basis for separating protists into major functional groups. The concept highlights their role as primary producers in aquatic ecosystems. It also links directly to energy capture mechanisms like photosynthesis. Hence, autotrophs synthesize organic food from inorganic substances.
302. Most autotrophic protists obtain energy primarily from:
ⓐ. Light (photosynthesis)
ⓑ. Oxidation of inorganic salts only in the dark
ⓒ. Ingestion of other cells
ⓓ. Absorption of dead organic matter only
Correct Answer: Light (photosynthesis)
Explanation: Autotrophic protists are mainly photosynthetic and use light energy to form organic compounds. They fix $CO_2$ into carbohydrates, acting as primary producers in aquatic habitats. This dependence on light explains their abundance in surface waters where sunlight penetrates. Their energy source differentiates them from heterotrophic protists that rely on organic food. Therefore, light is the primary energy source for most autotrophic protists. Hence, most autotrophic protists use light for photosynthesis.
303. The main ecological role of autotrophic protists in water bodies is as:
ⓐ. Primary producers forming the base of food chains
ⓑ. Predators that hunt fish
ⓒ. Decomposers that break only lignin
ⓓ. Parasites that always live inside humans
Correct Answer: Primary producers forming the base of food chains
Explanation: Autotrophic protists synthesize organic matter from inorganic sources using photosynthesis. This organic matter supports the energy needs of heterotrophic organisms in aquatic ecosystems. As a result, they form the base of many aquatic food chains, especially as planktonic producers. Their productivity influences the entire ecosystem’s biomass and energy flow. This producer role is a direct consequence of autotrophic nutrition. Hence, autotrophic protists act as primary producers in water bodies.
304. A protistan cell that prepares its own food from $CO_2$ and water using sunlight is best classified nutritionally as:
ⓐ. Heterotroph
ⓑ. Saprotroph
ⓒ. Parasite
ⓓ. Photoautotroph
Correct Answer: Photoautotroph
Explanation: Photoautotrophs use light energy to convert inorganic materials into organic food. In protists, this typically involves fixing $CO_2$ to form carbohydrates. This nutritional mode makes them producers and distinguishes them from heterotrophs that rely on organic food intake. The use of sunlight is the key energy feature in this classification. Such protists are common in aquatic environments with sufficient light. Therefore, the correct term is photoautotroph.
305. Which statement best distinguishes autotrophic protists from heterotrophic protists?
ⓐ. Autotrophs are always multicellular; heterotrophs are always unicellular.
ⓑ. Autotrophs synthesize organic food from inorganic sources; heterotrophs depend on pre-formed organic food.
ⓒ. Autotrophs lack a nucleus; heterotrophs have a nucleus.
ⓓ. Autotrophs live only on land; heterotrophs live only in water.
Correct Answer: Autotrophs synthesize organic food from inorganic sources; heterotrophs depend on pre-formed organic food.
Explanation: The key difference is the source of carbon and food. Autotrophic protists can build organic compounds using inorganic raw materials such as $CO_2$, typically powered by light. Heterotrophic protists cannot make their complete food this way and must obtain organic matter from other organisms or organic sources. This distinction is central to understanding nutritional diversity in Protista. It also links to ecological roles as producers versus consumers. Hence, autotrophs synthesize food from inorganic sources, while heterotrophs depend on pre-formed organic food.
306. Autotrophic protists are most likely to be abundant in:
ⓐ. Deep ocean zones with no light
ⓑ. Surface waters where sunlight is available
ⓒ. Completely dry deserts
ⓓ. Anaerobic rumen chambers
Correct Answer: Surface waters where sunlight is available
Explanation: Most autotrophic protists depend on photosynthesis, which requires sunlight. Therefore, they are more abundant in surface waters where light penetration supports photosynthetic activity. This explains their common association with planktonic communities near the water surface. Their distribution is closely tied to the availability of light for energy capture. As producers, they contribute significantly to primary productivity in these illuminated zones. Hence, surface waters with sunlight are most suitable for autotrophic protists.
307. The term “producer” applied to autotrophic protists mainly indicates that they:
ⓐ. Live only inside host organisms
ⓑ. Always break down dead organic matter only
ⓒ. Always feed by engulfing other cells
ⓓ. Convert inorganic carbon into organic matter for the ecosystem
Correct Answer: Convert inorganic carbon into organic matter for the ecosystem
Explanation: Producers synthesize organic substances from inorganic raw materials. Autotrophic protists fix $CO_2$ into carbohydrates and other organic compounds, adding new organic matter to the ecosystem. This organic matter becomes the food base for consumers in aquatic food webs. Their role is therefore fundamental to energy entry into the biological system. The producer label directly reflects their autotrophic nutrition. Hence, they convert inorganic carbon into organic matter for the ecosystem.
308. A correct inference about autotrophic protists is that they:
ⓐ. Cannot support aquatic food chains
ⓑ. Contribute to primary productivity in aquatic habitats
ⓒ. Are always anaerobic decomposers
ⓓ. Produce methane as the main end product
Correct Answer: Contribute to primary productivity in aquatic habitats
Explanation: Autotrophic protists carry out photosynthesis and produce organic matter. This production forms the primary productivity of many aquatic ecosystems, supplying energy to higher trophic levels. Their growth and photosynthetic activity influence biomass and nutrient cycles. Because they introduce organic carbon into food webs, they are essential to aquatic ecosystem functioning. This contribution is a direct result of their autotrophic mode of nutrition. Therefore, autotrophic protists contribute to primary productivity in aquatic habitats.
309. Which option best completes the statement: “Autotrophic protists differ from heterotrophic protists mainly in their _______”?
ⓐ. Cell type (prokaryotic vs eukaryotic)
ⓑ. Presence of a nucleus
ⓒ. Mode of nutrition (ability to synthesize food)
ⓓ. Being multicellular vs unicellular
Correct Answer: Mode of nutrition (ability to synthesize food)
Explanation: Both autotrophic and heterotrophic protists are eukaryotic and possess a nucleus. Their main difference lies in how they obtain food and energy. Autotrophic protists synthesize organic matter from inorganic sources, while heterotrophic protists rely on pre-formed organic nutrients. This nutritional distinction determines their ecological roles as producers or consumers. Therefore, mode of nutrition is the primary differentiating factor. Hence, they differ mainly in their mode of nutrition.
310. If a protist is autotrophic, the most appropriate description of its carbon source is:
ⓐ. Mainly inorganic carbon such as $CO_2$
ⓑ. Only complex organic matter from dead organisms
ⓒ. Only animal tissues inside a host
ⓓ. Only methane from marshes
Correct Answer: Mainly inorganic carbon such as $CO_2$
Explanation: Autotrophs build organic molecules using inorganic carbon, primarily $CO_2$. This is the defining carbon-source feature of autotrophic nutrition. In protists, this typically occurs through photosynthesis, which fixes $CO_2$ into carbohydrates. This distinguishes them from heterotrophs that require organic carbon sources already made by other organisms. The carbon source concept is central to nutritional classification. Therefore, an autotrophic protist mainly uses inorganic carbon such as $CO_2$.
311. A heterotrophic protist is best defined as one that:
ⓐ. Synthesizes its own food only from $CO_2$ using sunlight
ⓑ. Uses inorganic compounds only for both energy and carbon
ⓒ. Depends on pre-formed organic matter for nutrition
ⓓ. Produces methane as the main metabolic product
Correct Answer: Depends on pre-formed organic matter for nutrition
Explanation: Heterotrophs cannot meet their nutritional needs by synthesizing organic food solely from inorganic sources. They obtain carbon and energy by consuming or absorbing ready-made organic substances. In Protista, many organisms feed on smaller microbes, organic particles, or dissolved organic matter. This nutritional dependence defines them as consumers rather than producers. Their feeding strategies help regulate microbial populations in aquatic systems. Hence, a heterotrophic protist depends on pre-formed organic matter.
312. The term “mixotroph” in Protista refers to organisms that can:
ⓐ. Reproduce only sexually and never asexually
ⓑ. Live only in highly saline habitats
ⓒ. Form tissues and organs like higher plants
ⓓ. Show both autotrophic and heterotrophic nutrition depending on conditions
Correct Answer: Show both autotrophic and heterotrophic nutrition depending on conditions
Explanation: Mixotrophs combine nutritional strategies and can switch between them as needed. In favorable light conditions, they may photosynthesize and behave like autotrophs. When light is limiting or organic food is abundant, they can obtain nutrients heterotrophically. This dual mode provides flexibility in changing aquatic environments. It is an important concept to explain protistan survival and distribution. Therefore, mixotrophs show both autotrophic and heterotrophic nutrition.
313. A key advantage of mixotrophy in protists is that it:
ⓐ. Eliminates the need for any nutrients
ⓑ. Allows survival in variable conditions by switching between food-making and food-taking
ⓒ. Prevents any form of reproduction
ⓓ. Makes them strictly dependent on sunlight always
Correct Answer: Allows survival in variable conditions by switching between food-making and food-taking
Explanation: Aquatic environments often change in light availability and organic nutrient supply. Mixotrophs can photosynthesize when light is sufficient, ensuring self-feeding. When light is low or during unfavorable seasons, they can shift to heterotrophic feeding to meet energy and carbon needs. This flexibility increases survival and competitive ability. It explains why mixotrophs can persist across diverse habitats. Hence, mixotrophy provides survival advantage by enabling switching between autotrophy and heterotrophy.
314. A heterotrophic protist that feeds by engulfing food particles is showing a mode of nutrition most similar to:
ⓐ. Ingestion (holozoic nutrition)
ⓑ. Photosynthesis
ⓒ. Chemosynthesis from inorganic salts
ⓓ. Nitrogen fixation in heterocysts
Correct Answer: Ingestion (holozoic nutrition)
Explanation: Some protists obtain food by ingesting particles or other organisms into food vacuoles. This feeding method is called holozoic nutrition and is typical of consumer-like behavior. It involves capture, ingestion, and internal digestion within the cell. This is a clear example of heterotrophic nutrition in Protista. It contrasts with autotrophy, which does not require ingestion. Therefore, engulfing food particles indicates ingestion (holozoic nutrition).
315. Which statement correctly distinguishes a heterotrophic protist from an autotrophic protist?
ⓐ. Heterotrophic protists are prokaryotic; autotrophic protists are eukaryotic.
ⓑ. Heterotrophic protists depend on organic food; autotrophic protists synthesize food from inorganic sources.
ⓒ. Heterotrophic protists have no nucleus; autotrophic protists have a nucleus.
ⓓ. Heterotrophic protists live only on land; autotrophic protists live only in water.
Correct Answer: Heterotrophic protists depend on organic food; autotrophic protists synthesize food from inorganic sources.
Explanation: Both heterotrophic and autotrophic protists are eukaryotic and possess a nucleus. The key difference is nutritional source: heterotrophs require pre-formed organic matter for carbon and energy. Autotrophs build organic food using inorganic carbon like $CO_2$, usually powered by light. This distinction determines their ecological roles as consumers versus producers. It is a core idea in protistan nutrition diversity. Hence, heterotrophs depend on organic food while autotrophs synthesize from inorganic sources.
316. A protist that photosynthesizes in light but feeds on organic matter in darkness is best termed:
ⓐ. Heterotroph only
ⓑ. Chemoautotroph only
ⓒ. Mixotroph
ⓓ. Saprophyte only
Correct Answer: Mixotroph
Explanation: A mixotroph can use more than one nutritional strategy depending on environmental conditions. Using photosynthesis in the presence of light indicates autotrophic behavior. Feeding on organic matter in darkness indicates heterotrophic behavior. The ability to shift between these two modes is precisely what defines mixotrophy in protists. This flexibility helps organisms survive fluctuating light conditions in aquatic habitats. Therefore, such a protist is best termed a mixotroph.
317. Heterotrophic protists contribute to aquatic ecosystems mainly by:
ⓐ. Serving as consumers that feed on microbes and organic particles
ⓑ. Fixing atmospheric nitrogen as their primary function
ⓒ. Producing methane in all habitats
ⓓ. Forming the only base of food chains as producers
Correct Answer: Serving as consumers that feed on microbes and organic particles
Explanation: Heterotrophic protists obtain nutrition from organic matter and often feed on bacteria, algae, and other small organisms. This consumer role helps regulate microbial populations and transfers energy to higher trophic levels. They are important links between primary producers and larger organisms in aquatic food webs. Their feeding also supports nutrient recycling by processing organic particles. This ecological role follows directly from heterotrophic nutrition. Hence, they act as consumers feeding on microbes and organic particles.
318. A mixotrophic protist is most likely to dominate when:
ⓐ. Both light availability and organic food availability vary across time or space
ⓑ. Only oxygen is present and no nutrients exist
ⓒ. Only extremely high salinity exists with no light
ⓓ. Only hot acidic conditions exist permanently
Correct Answer: Both light availability and organic food availability vary across time or space
Explanation: Mixotrophy is beneficial in environments where conditions are not constant. When light fluctuates, the ability to photosynthesize part-time is useful. When organic food is intermittently available, heterotrophic feeding can supplement nutrition. This flexibility gives mixotrophs a competitive advantage in variable aquatic ecosystems. The strategy allows survival during low-light periods and growth during favorable periods. Therefore, mixotrophs are likely to dominate when both light and organic food availability vary.
319. Which is the most accurate statement about nutritional diversity in Protista?
ⓐ. All protists are strictly photosynthetic.
ⓑ. All protists are strictly heterotrophic.
ⓒ. Protists show diverse nutrition, including heterotrophy and mixotrophy.
ⓓ. Protists lack any nutritional strategy.
Correct Answer: Protists show diverse nutrition, including heterotrophy and mixotrophy.
Explanation: Protista is a diverse kingdom with multiple modes of nutrition. Many protists are heterotrophic, feeding on organic matter through ingestion or absorption. Some protists are mixotrophic, combining photosynthesis with heterotrophic feeding depending on conditions. This diversity explains their wide distribution and varied ecological roles in aquatic ecosystems. Nutritional variety is a key reason Protista is treated as a broad, diverse kingdom. Hence, protists show nutritional diversity including heterotrophy and mixotrophy.
320. The best single criterion to identify a protist as heterotrophic rather than mixotrophic is that it:
ⓐ. Always makes food using light energy
ⓑ. Can switch between photosynthesis and feeding on organic matter
ⓒ. Has a true nucleus
ⓓ. Relies only on organic food and does not synthesize its own food from inorganic sources
Correct Answer: Relies only on organic food and does not synthesize its own food from inorganic sources
Explanation: Heterotrophy means dependence on pre-formed organic matter for nutrition. Mixotrophs, in contrast, can also synthesize food from inorganic sources via photosynthesis under suitable conditions. Therefore, the distinguishing criterion is whether the organism can perform autotrophy at all. Having a nucleus does not separate these nutritional types because both are eukaryotic. The key is exclusive reliance on organic food. Hence, a protist that relies only on organic food and does not synthesize its own food from inorganic sources is heterotrophic.
321. Chrysophytes are a major protistan group that includes:
ⓐ. Diatoms and golden algae (desmids)
ⓑ. Mushrooms and yeasts
ⓒ. Blue-green algae
ⓓ. Mosses and ferns
Correct Answer: Diatoms and golden algae (desmids)
Explanation: Chrysophytes are a subgroup within Protista that includes diatoms and golden algae, commonly represented by desmids. They are typically aquatic and many are photosynthetic, contributing to primary productivity in water bodies. This grouping is based on characteristic features and shared evolutionary relationships within protists. The inclusion of diatoms is a key identifying point for chrysophytes. This concept is frequently tested in classification-based questions. Hence, chrysophytes include diatoms and golden algae (desmids).
322. A common habitat feature of chrysophytes is that they are found mainly in:
ⓐ. Dry desert sands
ⓑ. Aquatic environments (freshwater and marine)
ⓒ. Hot acidic springs only
ⓓ. High-salt pans only
Correct Answer: Aquatic environments (freshwater and marine)
Explanation: Chrysophytes such as diatoms and golden algae are commonly found in aquatic habitats. They occur in both freshwater and marine ecosystems and often form part of the plankton community. Being protists, they frequently depend on water for life processes and dispersal. Their aquatic abundance links them strongly to food webs and primary productivity. This habitat association is a standard feature used to describe the group. Therefore, chrysophytes are mainly aquatic in freshwater and marine environments.
323. Dinoflagellates are best identified among protists by being:
ⓐ. Multicellular organisms with tissues
ⓑ. Prokaryotic decomposers
ⓒ. Eukaryotic unicellular organisms, mostly marine, often with flagella
ⓓ. Fungi-like absorbers living only on land
Correct Answer: Eukaryotic unicellular organisms, mostly marine, often with flagella
Explanation: Dinoflagellates are protists, so they are eukaryotic and mostly unicellular. They are commonly found in marine environments and many forms possess flagella for movement. This combination—unicellular eukaryotes with characteristic motility—helps distinguish them as a protistan subgroup. Their marine abundance makes them significant components of plankton. The presence of flagella supports their active movement in water columns. Hence, dinoflagellates are unicellular eukaryotes, mostly marine, often with flagella.
324. A key ecological significance of chrysophytes (especially diatoms) is that they:
ⓐ. Lack any photosynthetic capability
ⓑ. Produce methane in anaerobic marshes
ⓒ. Are parasites of higher plants only
ⓓ. Act as important primary producers in aquatic food chains
Correct Answer: Act as important primary producers in aquatic food chains
Explanation: Many chrysophytes are photosynthetic and form a major component of aquatic plankton. Diatoms, in particular, contribute significantly to primary productivity by converting inorganic carbon into organic matter. This organic matter supports higher trophic levels in aquatic ecosystems. Their abundance in water bodies makes them central to food web energy flow. This ecological role directly follows from autotrophic nutrition in many members. Therefore, chrysophytes act as important primary producers.
325. Dinoflagellates are commonly associated with which type of habitat?
ⓐ. Only in saturated salt pans
ⓑ. Only dry soils
ⓒ. Only inside rumen of cattle
ⓓ. Mainly marine waters
Correct Answer: Mainly marine waters
Explanation: Dinoflagellates are widely distributed in marine environments and often form a major part of marine plankton. Their presence in oceans is a standard habitat association used in classification and ecology. Being aquatic protists, they thrive in water columns where they can move and access nutrients. This marine abundance contributes to their ecological importance in ocean productivity. Therefore, they are most commonly linked with marine waters. Hence, dinoflagellates are mainly marine.
326. Which pairing correctly matches protistan subgroup with a representative type?
ⓐ. Chrysophytes — diatoms
ⓑ. Chrysophytes — methanogens
ⓒ. Dinoflagellates — archaebacteria
ⓓ. Dinoflagellates — mycoplasma
Correct Answer: Chrysophytes — diatoms
Explanation: Chrysophytes include diatoms and golden algae as key representatives. Diatoms are therefore a correct example linked to chrysophytes. The other options list groups that belong to Monera (methanogens, mycoplasma) rather than Protista. Dinoflagellates are protists but not archaebacteria. Correct pairing depends on accurate subgroup membership within Protista. Hence, chrysophytes are correctly paired with diatoms.
327. Both chrysophytes and dinoflagellates are placed under Protista mainly because they are:
ⓐ. Prokaryotic organisms without a nucleus
ⓑ. Eukaryotic organisms, mostly unicellular and aquatic
ⓒ. Multicellular organisms with tissues
ⓓ. Seed-bearing organisms
Correct Answer: Eukaryotic organisms, mostly unicellular and aquatic
Explanation: Protista includes mainly unicellular eukaryotes that often live in aquatic or moist environments. Chrysophytes and dinoflagellates fit this description, as they are eukaryotic and commonly aquatic. They do not have tissue-level multicellularity, and they certainly are not seed-bearing. The presence of a true nucleus and organelles supports their eukaryotic placement. Their single-celled organization aligns with the protistan concept. Therefore, both are placed in Protista because they are eukaryotic, mostly unicellular and aquatic.
328. The term “golden algae” is most closely associated with which protistan subgroup?
ⓐ. Chrysophytes
ⓑ. Dinoflagellates
ⓒ. Cyanobacteria
ⓓ. Archaebacteria
Correct Answer: Chrysophytes
Explanation: Golden algae are included within chrysophytes along with diatoms. This association is a standard classification fact used to define chrysophytes as a protistan subgroup. Cyanobacteria are monerans and are not placed within Protista. Archaebacteria are a different prokaryotic group. Dinoflagellates are another subgroup of Protista but not termed golden algae in this context. Hence, “golden algae” is associated with chrysophytes.
329. A plankton sample from the ocean showing many unicellular eukaryotes with flagella is most consistent with:
ⓐ. Thermoacidophiles
ⓑ. Mycoplasma
ⓒ. Methanogens
ⓓ. Dinoflagellates
Correct Answer: Dinoflagellates
Explanation: Ocean plankton commonly includes dinoflagellates, which are unicellular eukaryotic protists. Many dinoflagellates possess flagella that aid in movement within the water column. The other options are prokaryotic groups under Monera and are not described as unicellular eukaryotes. The marine plankton context further supports dinoflagellates as the best match. This is a typical identification-style classification question. Therefore, the plankton sample is most consistent with dinoflagellates.
330. The most appropriate conclusion about chrysophytes and dinoflagellates, based on their grouping, is that they:
ⓐ. Are both prokaryotic bacteria
ⓑ. Are protists showing eukaryotic cell organization and mainly aquatic life
ⓒ. Are both multicellular fungi
ⓓ. Are both seed plants
Correct Answer: Are protists showing eukaryotic cell organization and mainly aquatic life
Explanation: Both chrysophytes and dinoflagellates belong to Protista, indicating eukaryotic cellular organization. They are mostly unicellular and typically associated with aquatic habitats, forming important components of plankton. This combination separates them from prokaryotes (Monera) and from multicellular eukaryotic kingdoms (Plantae, Fungi, Animalia). Their grouping reflects shared fundamental cell structure and ecological occurrence. Therefore, they are protists with eukaryotic organization and mainly aquatic life. Hence, the correct conclusion is that both are aquatic eukaryotic protists.
331. Euglenoids are protists that are commonly found in:
ⓐ. Dry desert rocks
ⓑ. Well-lit freshwater bodies such as ponds
ⓒ. Hot acidic springs only
ⓓ. Saturated salt pans only
Correct Answer: Well-lit freshwater bodies such as ponds
Explanation: Euglenoids are typically aquatic protists and are commonly seen in freshwater habitats, especially ponds. Their occurrence is closely linked to moist environments where movement and nutrient exchange are easy. Many euglenoids can photosynthesize in light, so well-lit waters support their growth. This habitat association is a standard identifying feature for euglenoids in classification. Their presence in pond water is frequently used as an example in protistan diversity. Hence, euglenoids are commonly found in well-lit freshwater bodies like ponds.
332. The most characteristic nutritional feature of many euglenoids is that they are:
ⓐ. Only autotrophic in all conditions
ⓑ. Only heterotrophic in all conditions
ⓒ. Strictly saprophytic decomposers
ⓓ. Mixotrophic, switching between autotrophy and heterotrophy
Correct Answer: Mixotrophic, switching between autotrophy and heterotrophy
Explanation: Euglenoids can photosynthesize when light is available, behaving like autotrophs. In the absence of light, they can obtain nutrition heterotrophically by using organic substances. This dual strategy is called mixotrophy and provides flexibility in changing aquatic environments. It helps euglenoids survive in conditions where light availability fluctuates. This nutritional versatility is a key point in their classification and ecology. Therefore, many euglenoids are mixotrophic.
333. Slime moulds are best described as organisms that:
ⓐ. Are prokaryotic photosynthetic bacteria
ⓑ. Are multicellular seed plants
ⓒ. Are fungus-like protists that feed on decaying organic matter
ⓓ. Are salt-loving archaebacteria
Correct Answer: Are fungus-like protists that feed on decaying organic matter
Explanation: Slime moulds are placed under Protista and are often described as fungus-like because they show saprophytic nutrition. They feed on decaying organic matter, contributing to decomposition in moist habitats. Despite their fungus-like role, they are treated under protists in this classification framework. Their lifestyle is strongly associated with damp places rich in organic debris. This feeding habit is a key basis for understanding their ecological importance. Hence, slime moulds are fungus-like protists feeding on decaying organic matter.
334. A typical habitat where slime moulds are commonly seen is:
ⓐ. Moist soil and rotting logs/leaves
ⓑ. Dry sand dunes
ⓒ. Open ocean surface waters only
ⓓ. High-temperature acidic springs
Correct Answer: Moist soil and rotting logs/leaves
Explanation: Slime moulds require moist conditions because their feeding and movement depend on a water film. They commonly occur on decaying leaves, rotting wood, and damp forest floors where organic matter is abundant. Such habitats provide a continuous supply of decomposing material for saprophytic nutrition. This environment also supports their growth and spread across surfaces. The association with moist, decaying substrates is a standard identification clue. Therefore, slime moulds are commonly seen in moist soil and rotting logs/leaves.
335. Euglenoids are placed under Protista primarily because they are:
ⓐ. Prokaryotic and lack a nucleus
ⓑ. Eukaryotic and mostly unicellular
ⓒ. Multicellular with tissue-level organisation
ⓓ. Seed-bearing organisms
Correct Answer: Eukaryotic and mostly unicellular
Explanation: Euglenoids possess a true nucleus and membrane-bound organelles, so they are eukaryotic. They are typically unicellular and perform all life functions within a single cell, matching the key definition of Protista. This distinguishes them from Monera (prokaryotes) and from multicellular eukaryotic kingdoms. Their classification is therefore based on cell type and level of organisation. This is the core reason they are included in Protista. Hence, euglenoids are eukaryotic and mostly unicellular.
336. The best explanation for calling euglenoids “mixotrophs” is that they:
ⓐ. Are always parasites and always producers
ⓑ. Can photosynthesize in light and shift to heterotrophic nutrition in darkness
ⓒ. Fix nitrogen using heterocysts
ⓓ. Produce methane under anaerobic conditions
Correct Answer: Can photosynthesize in light and shift to heterotrophic nutrition in darkness
Explanation: Mixotrophy means combining autotrophic and heterotrophic nutrition depending on environmental conditions. Euglenoids can prepare food through photosynthesis when light is present, showing autotrophic behavior. When light is not available, they can obtain nutrition from organic sources, showing heterotrophic behavior. This ability provides strong survival advantage in variable freshwater habitats. The concept is repeatedly used to distinguish euglenoids within protists. Therefore, euglenoids are mixotrophs because they photosynthesize in light and become heterotrophic in darkness.
337. Which statement correctly links slime moulds with their nutritional mode?
ⓐ. Slime moulds are mainly photosynthetic producers
ⓑ. Slime moulds are strict chemoautotrophs
ⓒ. Slime moulds feed on decaying organic matter like decomposers
ⓓ. Slime moulds depend only on $CO_2$ as their carbon source
Correct Answer: Slime moulds feed on decaying organic matter like decomposers
Explanation: Slime moulds obtain nutrition from dead and decaying organic material. They break down organic debris and absorb the simpler substances, showing a decomposer-like role. This saprophytic mode is why they are described as fungus-like protists. Their contribution to decomposition is a key ecological significance in moist terrestrial habitats. This concept directly connects their lifestyle to nutrient recycling. Hence, slime moulds feed on decaying organic matter like decomposers.
338. In classification discussions, slime moulds are often termed “fungus-like” because they:
ⓐ. Have peptidoglycan cell walls
ⓑ. Show saprophytic feeding on decaying matter
ⓒ. Possess chloroplasts for photosynthesis
ⓓ. Are prokaryotic extremophiles
Correct Answer: Show saprophytic feeding on decaying matter
Explanation: The label “fungus-like” is used because slime moulds behave like decomposers, feeding on dead and decaying organic material. This saprophytic nutrition resembles the ecological role commonly associated with fungi. The comparison is based on lifestyle and function rather than being true fungi. Their occurrence on rotting leaves and logs supports this description. This is a standard way to understand slime moulds within Protista. Therefore, slime moulds are called fungus-like because they show saprophytic feeding.
339. Which pairing correctly matches protistan subgroup with a key concept?
ⓐ. Euglenoids — mixotrophy
ⓑ. Euglenoids — methane production in rumen
ⓒ. Slime moulds — strict photoautotrophy
ⓓ. Slime moulds — salt-loving extremophily
Correct Answer: Euglenoids — mixotrophy
Explanation: Euglenoids are commonly highlighted for mixotrophy, meaning they can photosynthesize in light and feed heterotrophically in darkness. This nutritional flexibility is a defining concept for them in protistan subgroups. The other options incorrectly assign traits related to archaebacteria or unrelated nutritional modes. Correct matching depends on linking the subgroup with its characteristic feature taught in classification. Hence, euglenoids correctly match with mixotrophy.
340. A protist is found in pond water, shows a true nucleus, and can switch from photosynthesis to heterotrophy when light is absent. The most likely subgroup is:
ⓐ. Chrysophytes
ⓑ. Slime moulds
ⓒ. Dinoflagellates
ⓓ. Euglenoids
Correct Answer: Euglenoids
Explanation: Euglenoids are freshwater protists commonly found in ponds and are known for mixotrophic nutrition. The ability to photosynthesize in light and become heterotrophic in darkness is a hallmark of euglenoids. Their eukaryotic nature is confirmed by the presence of a true nucleus. The habitat and nutritional flexibility together strongly point to euglenoids rather than other protistan subgroups. This is a classic identification pattern in biological classification. Therefore, the most likely subgroup is euglenoids.
341. Protozoans are best described as protists that are primarily:
ⓐ. Photosynthetic autotrophs with rigid cell walls
ⓑ. Multicellular eukaryotes with tissue organisation
ⓒ. Heterotrophic, animal-like unicellular eukaryotes
ⓓ. Prokaryotic decomposers
Correct Answer: Heterotrophic, animal-like unicellular eukaryotes
Explanation: Protozoans are unicellular eukaryotic organisms, so they possess a true nucleus and organelles. They are termed “animal-like” because they are primarily heterotrophic and often feed on other organisms or organic particles. This consumer-like nutrition distinguishes them from many photosynthetic protists. Their unicellular organization and heterotrophy together define them as protozoans in classification. This is the key trait used to recognize protozoans within Protista. Hence, protozoans are heterotrophic, animal-like unicellular eukaryotes.
342. A common example-style identification of protozoans in pond water is a unicellular organism that:
ⓐ. Prepares food only by photosynthesis
ⓑ. Feeds on other microorganisms by ingestion
ⓒ. Produces methane in anaerobic conditions
ⓓ. Thrives only in saturated brine
Correct Answer: Feeds on other microorganisms by ingestion
Explanation: Many protozoans obtain nutrition by engulfing food particles or other microorganisms. This ingestion-based feeding reflects their heterotrophic, animal-like nature. Such feeding is common in aquatic habitats where bacteria and small algae are abundant. The behavior distinguishes protozoans from photosynthetic protists that synthesize food. It also explains their ecological role as consumers in microbial food webs. Therefore, feeding by ingestion is a typical protozoan identification trait.
343. Protozoans are placed under Protista mainly because they are:
ⓐ. Prokaryotic organisms without a true nucleus
ⓑ. Eukaryotic organisms that are mostly unicellular
ⓒ. Multicellular organisms with organs
ⓓ. Seed-bearing organisms
Correct Answer: Eukaryotic organisms that are mostly unicellular
Explanation: Protista includes primarily eukaryotic organisms that are unicellular or simple. Protozoans have a true nucleus and membrane-bound organelles, confirming eukaryotic organization. They are generally unicellular and carry out all life functions within one cell. This combination matches the core definition of Protista. Therefore, they are classified in Protista due to being unicellular eukaryotes. Hence, protozoans are placed in Protista because they are eukaryotic and mostly unicellular.
344. In aquatic ecosystems, protozoans contribute most directly to planktonic life as:
ⓐ. Only producers at the base of food chains
ⓑ. Consumers that feed on bacteria and other small organisms
ⓒ. Seed-forming dispersal units
ⓓ. Extremophiles of hot acidic springs
Correct Answer: Consumers that feed on bacteria and other small organisms
Explanation: Many protozoans are part of plankton and act as heterotrophic consumers. They feed on bacteria, microscopic algae, and organic particles, transferring energy to higher levels. This positions them as important links in aquatic food webs. Their consumer role complements photosynthetic plankton that act as producers. Because plankton includes drifting organisms, protozoans commonly fit within it due to their aquatic, microscopic nature. Hence, protozoans contribute to plankton mainly as consumers feeding on microbes.
345. The term “plankton” refers to organisms that:
ⓐ. Live attached permanently to rocks at the bottom
ⓑ. Can always swim against water currents strongly
ⓒ. Are strictly terrestrial and live in soil
ⓓ. Drift in water and are largely unable to resist currents effectively
Correct Answer: Drift in water and are largely unable to resist currents effectively
Explanation: Plankton are organisms that float or drift in water, moving largely with currents. They may have limited movement but generally cannot oppose water flow strongly. This category includes both microscopic producers and consumers, depending on their nutrition. The key idea is their drifting habit in aquatic environments. This concept is important for understanding aquatic food chains and organism distribution. Therefore, plankton are drifting organisms that cannot effectively resist currents.
346. A correct “example style” statement for a protozoan is:
ⓐ. A unicellular eukaryote that engulfs bacteria for food in pond water
ⓑ. A prokaryote with peptidoglycan wall that fixes nitrogen
ⓒ. A salt-loving archaebacterium found in brine
ⓓ. A fungus-like decomposer growing on rotting logs
Correct Answer: A unicellular eukaryote that engulfs bacteria for food in pond water
Explanation: Protozoans are defined by being unicellular eukaryotes with heterotrophic, animal-like nutrition. Engulfing bacteria is a typical ingestion-based feeding behavior seen in many protozoans. Pond water is a common habitat where such feeding interactions occur. This description matches both their cell type (eukaryotic, unicellular) and their nutritional mode (heterotrophic ingestion). It is therefore a correct example-style statement. Hence, a unicellular eukaryote engulfing bacteria in pond water is a protozoan example.
347. Protozoans are “animal-like” mainly because they:
ⓐ. Possess chlorophyll and photosynthesize
ⓑ. Are heterotrophic and often show ingestion-based feeding
ⓒ. Have cellulose cell walls like plants
ⓓ. Produce methane in anaerobic habitats
Correct Answer: Are heterotrophic and often show ingestion-based feeding
Explanation: The “animal-like” label reflects consumer-like nutrition rather than body complexity. Protozoans generally cannot synthesize their own food from inorganic sources and instead obtain organic matter by feeding. Many show ingestion, forming food vacuoles and digesting internally within the cell. This feeding style resembles animals more than plants. It also explains their ecological role as microscopic consumers. Therefore, protozoans are called animal-like because they are heterotrophic and often ingest food.
348. In a plankton community, photosynthetic protists and protozoans together primarily represent:
ⓐ. Only decomposers
ⓑ. Only producers
ⓒ. Producers and consumers that form a basic aquatic food web
ⓓ. Only organisms living on land
Correct Answer: Producers and consumers that form a basic aquatic food web
Explanation: Photosynthetic protists contribute as primary producers by synthesizing organic matter. Protozoans contribute as consumers by feeding on microbes and organic particles. Together they establish energy flow within aquatic ecosystems, forming the foundation of food webs. Their interaction supports higher trophic levels like small aquatic animals and fish larvae. This producer-consumer pairing is central to the concept of plankton-based ecology. Hence, they represent producers and consumers forming a basic aquatic food web.
349. Which statement best captures the role of protozoans in nutrient cycling in aquatic systems?
ⓐ. They convert $CO_2$ into carbohydrates as the main process
ⓑ. They are inactive and do not interact with microbes
ⓒ. They directly form seeds for dispersal
ⓓ. They graze on microbial populations, helping transfer energy and recycle nutrients
Correct Answer: They graze on microbial populations, helping transfer energy and recycle nutrients
Explanation: Protozoans feed on bacteria and other microorganisms, which helps regulate microbial population levels. This grazing transfers energy from microbes to higher trophic levels and supports the flow of matter through the ecosystem. By processing organic material, protozoans also contribute to nutrient recycling in aquatic habitats. Their role is therefore both ecological and functional within plankton communities. This concept connects their heterotrophic nutrition to ecosystem processes. Hence, protozoans help transfer energy and recycle nutrients by grazing on microbes.
350. A plankton-rich pond ecosystem is likely to show protozoans because protozoans are:
ⓐ. Terrestrial seed plants
ⓑ. Large animals that live only on land
ⓒ. Aquatic unicellular eukaryotes that can drift and feed on microbes
ⓓ. Prokaryotic organisms with peptidoglycan walls only
Correct Answer: Aquatic unicellular eukaryotes that can drift and feed on microbes
Explanation: Protozoans are unicellular eukaryotic organisms commonly found in aquatic habitats. Many drift in water as part of plankton and feed heterotrophically on bacteria and small organisms. Their small size makes them well-suited to planktonic life, where drifting with currents is common. This explains why they are regularly present in plankton-rich ponds. The combination of aquatic habitat, unicellularity, and heterotrophic feeding supports their role. Therefore, protozoans occur because they are aquatic unicellular eukaryotes that drift and feed on microbes.
351. In fungi, hyphae are best defined as:
ⓐ. Root-like structures of plants
ⓑ. Thread-like filamentous structures forming the fungal body
ⓒ. Photosynthetic leaf-like structures
ⓓ. Bacterial colonies without nuclei
Correct Answer: Thread-like filamentous structures forming the fungal body
Explanation: Hyphae are long, thread-like filaments that make up the vegetative body of most fungi. They spread through the substrate and absorb nutrients over a large surface area. These filaments interweave to form a network, providing structure and support. Hyphae represent the basic structural unit of many fungi. This concept is central to understanding fungal body organization. Hence, hyphae are thread-like filamentous structures forming the fungal body.
352. The term “mycelium” refers to:
ⓐ. A single fungal spore
ⓑ. A fungal fruiting body only
ⓒ. A network/mass of hyphae forming the vegetative body
ⓓ. A bacterial cell wall component
Correct Answer: A network/mass of hyphae forming the vegetative body
Explanation: Mycelium is the collective, branched network formed by many hyphae. It constitutes the main vegetative part of a fungus and spreads through the nutrient source. This extensive network increases surface area for absorption, supporting fungal nutrition. The mycelium is therefore fundamental to fungal growth and colony expansion. Understanding mycelium helps connect hyphal structure to fungal lifestyle. Hence, mycelium is the mass of hyphae forming the vegetative body.
353. Septate hyphae are characterized by:
ⓐ. Absence of cross walls throughout the filament
ⓑ. Being made only of bacterial cells
ⓒ. Presence of chloroplasts in each segment
ⓓ. Presence of cross walls (septa) dividing the hypha into compartments
Correct Answer: Presence of cross walls (septa) dividing the hypha into compartments
Explanation: Septate hyphae possess internal cross walls called septa. These septa divide the hypha into compartments, often with pores that allow cytoplasmic continuity. This compartmentalization is an important structural feature used in classification and description of fungal groups. It also influences how materials move within the fungal filament. The presence of septa is therefore the defining feature of septate hyphae. Hence, septate hyphae have cross walls dividing them into compartments.
354. Aseptate (coenocytic) hyphae are best described as hyphae that:
ⓐ. Have many cross walls and separate cells
ⓑ. Lack septa, forming a continuous multinucleate cytoplasm
ⓒ. Are unicellular and non-filamentous
ⓓ. Contain a true vascular system
Correct Answer: Lack septa, forming a continuous multinucleate cytoplasm
Explanation: Aseptate hyphae do not have cross walls (septa) dividing the filament. As a result, the cytoplasm forms a continuous mass containing many nuclei. This condition is termed coenocytic and is a key structural description in fungi. It helps distinguish certain fungal groups based on hyphal organization. The concept links fungal body structure to classification. Hence, aseptate hyphae lack septa and are continuous multinucleate filaments.
355. The best structural relationship between hyphae and mycelium is that:
ⓐ. Hyphae are made from mycelium
ⓑ. Mycelium is formed by an interwoven network of hyphae
ⓒ. Mycelium is a type of spore produced by hyphae
ⓓ. Hyphae and mycelium are unrelated terms
Correct Answer: Mycelium is formed by an interwoven network of hyphae
Explanation: Hyphae are the individual filamentous units of a fungal body. When many hyphae grow and branch together, they form a mass or network called mycelium. This network constitutes the main vegetative body responsible for nutrient absorption and growth. The relationship is therefore part-to-whole: hyphae build the mycelium. This linkage is essential for understanding fungal body organization. Hence, mycelium is formed by an interwoven network of hyphae.
356. A fungus with hyphae divided by septa is correctly described as having:
ⓐ. Prokaryotic filaments
ⓑ. Aseptate hyphae
ⓒ. No hyphae at all
ⓓ. Septate hyphae
Correct Answer: Septate hyphae
Explanation: Septa are cross walls that partition hyphae into segments. When hyphae show these partitions, they are termed septate hyphae. This is a direct structural classification based on presence of septa. It is commonly used to describe the body organization of many fungi. The feature is fundamental and easy to test conceptually. Therefore, hyphae divided by septa are septate hyphae.
357. The term “coenocytic” in fungi is most directly linked to:
ⓐ. Hyphae lacking septa and containing many nuclei in a continuous cytoplasm
ⓑ. Hyphae with numerous septa and single nucleus per compartment
ⓒ. Presence of chlorophyll pigments
ⓓ. Formation of seeds
Correct Answer: Hyphae lacking septa and containing many nuclei in a continuous cytoplasm
Explanation: Coenocytic describes a condition where a hyphal filament is not divided into compartments by septa. This results in a continuous cytoplasm with multiple nuclei distributed along the hypha. Such hyphae are therefore called aseptate or coenocytic. This feature is an important structural descriptor in fungal classification. It links directly to the internal organization of the fungal body. Hence, coenocytic refers to aseptate, multinucleate continuous hyphae.
358. A major advantage of a mycelial network for fungi is that it:
ⓐ. Reduces surface area for absorption
ⓑ. Increases surface area for absorption of nutrients from the substrate
ⓒ. Enables photosynthesis like green plants
ⓓ. Produces peptidoglycan cell walls
Correct Answer: Increases surface area for absorption of nutrients from the substrate
Explanation: Fungi are absorptive heterotrophs and rely on efficient nutrient uptake from their surroundings. A mycelium spreads extensively through the substrate, greatly increasing contact area. This large surface area allows more efficient secretion of enzymes and absorption of digested nutrients. The networked growth pattern is therefore well-suited to their lifestyle. This is a key functional reason the mycelial form is emphasized. Hence, the mycelium increases surface area for nutrient absorption.
359. If a fungus is described as “filamentous,” the most accurate implication is that its body is mainly composed of:
ⓐ. Hyphae forming mycelium
ⓑ. Leaves and stems
ⓒ. Single bacterial cells only
ⓓ. Animal tissues
Correct Answer: Hyphae forming mycelium
Explanation: “Filamentous” indicates a body made of thread-like filaments. In fungi, these filaments are hyphae, which collectively form the mycelium. This structural organization is typical of many fungi and supports absorptive nutrition. The term directly points to hyphal growth rather than plant or animal structures. It is a core descriptor in fungal morphology. Therefore, filamentous fungi are mainly composed of hyphae forming mycelium.
360. The most accurate statement about septate versus aseptate hyphae is that the distinction is based on:
ⓐ. Presence or absence of a true nucleus
ⓑ. Presence or absence of chloroplasts
ⓒ. Presence or absence of cross walls (septa) in hyphae
ⓓ. Presence or absence of seeds
Correct Answer: Presence or absence of cross walls (septa) in hyphae
Explanation: Septate hyphae possess cross walls called septa that divide the hypha into compartments. Aseptate hyphae lack these cross walls and show continuous cytoplasm, often multinucleate. This criterion is purely structural and is widely used to describe fungal body organization. It does not depend on chloroplasts, seeds, or nucleus presence because fungi are eukaryotic and non-photosynthetic. Therefore, the distinction rests on whether septa are present. Hence, septate versus aseptate is based on presence or absence of cross walls (septa).
361. The chief structural component of the fungal cell wall is:
ⓐ. Chitin
ⓑ. Peptidoglycan
ⓒ. Cellulose
ⓓ. Lignin
Correct Answer: Chitin
Explanation: Fungi possess a rigid cell wall that is characteristically made of chitin. Chitin is a nitrogen-containing polysaccharide that provides strength and support to fungal cells. This feature is a key structural criterion used to distinguish fungi from plants (cellulose walls) and most true bacteria (peptidoglycan walls). Because it is stable and fundamental, it is frequently used in classification and identification. The presence of chitin aligns with the fungal body plan and lifestyle. Hence, the fungal cell wall is chiefly composed of chitin.
362. The presence of chitin in the cell wall is most useful for recognizing fungi as:
ⓐ. Prokaryotic organisms
ⓑ. A distinct eukaryotic kingdom with characteristic wall chemistry
ⓒ. Seed-bearing plants
ⓓ. Photosynthetic algae
Correct Answer: A distinct eukaryotic kingdom with characteristic wall chemistry
Explanation: Fungi are eukaryotic but differ from other eukaryotic kingdoms in key structural traits. One major distinguishing trait is their cell wall composition, which includes chitin. This chemical character is stable and thus valuable for classification. It helps separate fungi from plants (cellulose) and many bacterial groups (peptidoglycan). Wall chemistry reflects deep cellular organization and is not a superficial trait. Therefore, chitin supports fungi being a distinct eukaryotic kingdom with characteristic wall chemistry.
363. Which statement best describes chitin in the context of fungal structure?
ⓐ. It is the main storage carbohydrate in fungi
ⓑ. It forms the nuclear membrane of fungi
ⓒ. It is the pigment required for photosynthesis
ⓓ. It is a nitrogen-containing polysaccharide providing rigidity to the fungal cell wall
Correct Answer: It is a nitrogen-containing polysaccharide providing rigidity to the fungal cell wall
Explanation: Chitin is a polysaccharide that contains nitrogen and is used as a structural material in fungi. Its primary role is to provide mechanical strength and rigidity to the fungal cell wall. This supports the fungus in maintaining shape and resisting external stresses. Because it is part of the wall, it is a defining structural component of fungal cells. This feature is widely used in classification discussions of fungi. Hence, chitin is a nitrogen-containing polysaccharide that gives rigidity to the fungal wall.
364. A cell wall made mainly of chitin is most consistent with an organism belonging to:
ⓐ. Kingdom Fungi
ⓑ. Kingdom Monera (true bacteria)
ⓒ. Kingdom Plantae
ⓓ. Kingdom Animalia
Correct Answer: Kingdom Fungi
Explanation: The chemical composition of the cell wall is a key identifying character at kingdom level. Fungal walls are characteristically composed of chitin, unlike plants which have cellulose and animals which lack cell walls. True bacteria typically have peptidoglycan walls. Therefore, chitin-based wall composition strongly supports fungal identity. This is a standard structural hallmark of fungi in biological classification. Hence, an organism with a chitin-rich cell wall belongs to Kingdom Fungi.
365. Why is “cell wall composition” an important criterion while studying fungi?
ⓐ. It changes randomly every day, so it is a quick differentiator
ⓑ. It is a stable structural feature that helps distinguish fungi from other kingdoms
ⓒ. It depends only on whether the organism lives in water
ⓓ. It is unrelated to classification
Correct Answer: It is a stable structural feature that helps distinguish fungi from other kingdoms
Explanation: Cell wall composition is a deep structural character that remains consistent within major groups. In fungi, the presence of chitin is a reliable hallmark that helps differentiate them from plants (cellulose walls) and bacteria (peptidoglycan walls). Because it reflects fundamental cellular organization, it is more dependable than many superficial traits. This is why it is emphasized as a major classification criterion. It also connects structure with functional strength and protection. Hence, wall composition is important because it is stable and distinguishes fungi from other kingdoms.
366. Which option correctly matches organism group with its characteristic wall component?
ⓐ. Fungi — chitin
ⓑ. Animals — cellulose
ⓒ. True bacteria — cellulose
ⓓ. Plants — peptidoglycan
Correct Answer: Fungi — chitin
Explanation: Fungal cell walls are characteristically made of chitin, providing rigidity and support. This pairing is a standard classification fact used to identify fungi. Cell wall materials are fundamental structural markers across kingdoms. Recognizing the correct wall component helps quickly differentiate fungi from plants and bacteria. This concept is frequently tested in exam questions on biological classification. Therefore, fungi correctly match with chitin.
367. The most accurate inference from “fungal cell wall contains chitin” is that fungi are:
ⓐ. Exactly identical to plants in all structural traits
ⓑ. Prokaryotes with peptidoglycan walls
ⓒ. Eukaryotes with a distinct wall chemistry supporting their separate kingdom status
ⓓ. Organisms without any cell wall
Correct Answer: Eukaryotes with a distinct wall chemistry supporting their separate kingdom status
Explanation: Fungi are eukaryotic organisms but they have unique structural traits. Chitin in their cell wall is a distinguishing chemical feature not typical of plants or animals. Because cell wall chemistry is stable and fundamental, it supports separating fungi into their own kingdom. This trait reflects a characteristic fungal body plan and structural support system. It is therefore an important basis for classification at higher taxonomic ranks. Hence, fungi are eukaryotes with distinct wall chemistry supporting separate kingdom status.
368. A student wants one high-confidence feature to separate fungi from plants at the basic structural level. The best feature is:
ⓐ. Fungi store food
ⓑ. Fungi have a cell wall made of chitin (plants have cellulose)
ⓒ. Fungi are found in moist places
ⓓ. Fungi are larger than plants
Correct Answer: Fungi have a cell wall made of chitin (plants have cellulose)
Explanation: Both fungi and plants possess cell walls, so the mere presence of a wall is not sufficient to separate them. The chemical composition is the most reliable structural difference: fungi have chitin, while plants have cellulose. This feature is stable and directly reflects fundamental biology. Because it is a clear, kingdom-level trait, it is widely used for identification. It avoids confusion caused by habitat or size variation. Therefore, chitin versus cellulose is the best separating feature.
369. Chitin provides fungal cells with:
ⓐ. A rigid supportive wall structure
ⓑ. Photosynthetic capability
ⓒ. A true nucleus
ⓓ. Seed coat formation
Correct Answer: A rigid supportive wall structure
Explanation: Chitin is a structural polysaccharide that strengthens the fungal cell wall. Its main function is to provide rigidity, support, and protection to the cell. This helps fungi maintain their shape and withstand environmental stresses. Because fungi rely on absorptive nutrition, a strong wall supports extensive hyphal growth. The role of chitin is therefore primarily mechanical and protective. Hence, chitin provides a rigid supportive wall structure.
370. The best statement summarizing the significance of chitin for fungal classification is:
ⓐ. Chitin proves fungi are bacteria
ⓑ. Chitin is a defining wall component that helps identify fungi as a separate kingdom
ⓒ. Chitin is the main pigment of fungi
ⓓ. Chitin indicates the presence of chloroplasts
Correct Answer: Chitin is a defining wall component that helps identify fungi as a separate kingdom
Explanation: Chitin is a characteristic cell wall component of fungi and is not typical of plants or animals. Because cell wall chemistry is stable and fundamental, it is a reliable basis for identifying fungi. This structural trait supports treating fungi as a distinct kingdom among eukaryotes. It is repeatedly emphasized in classification because it separates fungi from other major groups with different wall composition. The significance is therefore taxonomic and structural. Hence, chitin is a defining wall component that helps identify fungi as a separate kingdom.
371. In fungi, saprophytic nutrition means the fungus:
ⓐ. Synthesizes food from $CO_2$ using sunlight
ⓑ. Obtains food by ingesting solid particles into a gut
ⓒ. Feeds on dead and decaying organic matter by absorption
ⓓ. Fixes atmospheric nitrogen using heterocysts
Correct Answer: Feeds on dead and decaying organic matter by absorption
Explanation: Saprophytes obtain nutrients from non-living organic material such as dead leaves, wood, or organic wastes. Fungi secrete enzymes onto the substrate to break complex substances into simpler soluble molecules. These soluble products are then absorbed through the fungal hyphae. This absorptive feeding is a hallmark of fungal nutrition and explains their role as decomposers. It also links directly to nutrient recycling in ecosystems. Hence, saprophytic fungi feed on dead and decaying matter by absorption.
372. The best description of parasitic nutrition in fungi is that they:
ⓐ. Live on living hosts and derive nutrients from them
ⓑ. Always make food using photosynthesis
ⓒ. Depend only on inorganic salts for nutrition
ⓓ. Obtain food only from dead remains
Correct Answer: Live on living hosts and derive nutrients from them
Explanation: Parasitic fungi obtain nourishment from living organisms, called hosts. They draw nutrients from the host’s tissues and can cause disease or harm. This mode of nutrition differs from saprophytic feeding, which uses dead organic matter. The key idea is dependence on a living host for nutrition. This nutritional strategy is important in understanding fungal pathogenicity. Hence, parasitic fungi live on living hosts and derive nutrients from them.
373. A fungus growing on a dead log and absorbing nutrients from it is showing:
ⓐ. Autotrophic nutrition
ⓑ. Saprophytic nutrition
ⓒ. Parasitic nutrition
ⓓ. Chemoautotrophic nutrition
Correct Answer: Saprophytic nutrition
Explanation: A dead log represents non-living organic matter. Saprophytic fungi feed on such dead and decaying materials by secreting enzymes and absorbing the digested nutrients. This is the typical decomposer role of many fungi in forests. The process supports nutrient recycling by breaking down complex plant remains. Because the substrate is dead, the nutrition is saprophytic, not parasitic. Therefore, the fungus is showing saprophytic nutrition.
374. The ecological importance of saprophytic fungi is best explained by their role in:
ⓐ. Primary production in aquatic ecosystems
ⓑ. Producing methane in rumen
ⓒ. Fixing atmospheric nitrogen into nitrates
ⓓ. Breaking down organic matter and recycling nutrients
Correct Answer: Breaking down organic matter and recycling nutrients
Explanation: Saprophytic fungi decompose dead plants, animals, and organic wastes. They release extracellular enzymes that break complex molecules into simpler compounds. These compounds are absorbed and also returned to the environment as recycled nutrients. This decomposition maintains soil fertility and supports nutrient cycles. Their role is therefore essential for ecosystem functioning. Hence, saprophytic fungi are important for breaking down organic matter and recycling nutrients.
375. A key feature of fungal saprophytic nutrition is that digestion is:
ⓐ. Intracellular, inside food vacuoles only
ⓑ. Extracellular, followed by absorption
ⓒ. Absent because fungi do not digest food
ⓓ. Performed only by chloroplasts
Correct Answer: Extracellular, followed by absorption
Explanation: Fungi secrete digestive enzymes onto the substrate outside their body. These enzymes break down complex organic materials into simpler soluble molecules. The fungi then absorb these molecules through the hyphal surface. This is called extracellular digestion and is characteristic of saprophytic fungal feeding. It explains why fungi can grow on solid organic substrates like wood or leaf litter. Therefore, digestion in saprophytic fungi is extracellular followed by absorption.
376. A fungus causing disease in a living plant is most appropriately categorized nutritionally as:
ⓐ. Saprophyte
ⓑ. Autotroph
ⓒ. Parasite
ⓓ. Producer
Correct Answer: Parasite
Explanation: Disease-causing fungi draw nutrients from living plant tissues, making the plant the host. This dependence on living organisms for nutrition defines parasitism. The fungal growth can harm the host by damaging tissues and reducing normal functioning. This nutritional mode is therefore described as parasitic. It contrasts with saprophytes that feed on dead organic matter. Hence, a disease-causing fungus in a living plant is a parasite.
377. Which statement best contrasts saprophytes and parasites in fungi?
ⓐ. Saprophytes feed on living hosts; parasites feed on dead matter
ⓑ. Both depend only on inorganic carbon
ⓒ. Both feed only by photosynthesis
ⓓ. Saprophytes feed on dead matter; parasites feed on living hosts
Correct Answer: Saprophytes feed on dead matter; parasites feed on living hosts
Explanation: Saprophytes obtain nutrients from non-living organic material such as dead remains and wastes. Parasites obtain nutrients from living organisms, using them as hosts. This contrast is a standard nutritional classification for fungi. It also explains differences in ecological role: decomposers versus disease-causing agents. The distinction depends on whether the nutrient source is living or non-living. Therefore, saprophytes feed on dead matter while parasites feed on living hosts.
378. A correct example-style statement for parasitic fungi is:
ⓐ. A fungus absorbing nutrients from rotting leaves
ⓑ. A fungus obtaining nutrients from a living host organism
ⓒ. A fungus synthesizing food from $CO_2$ using sunlight
ⓓ. A fungus oxidizing ammonia to gain energy
Correct Answer: A fungus obtaining nutrients from a living host organism
Explanation: Parasitic fungi derive nourishment from living hosts such as plants, animals, or humans. Their nutrition depends on host tissues, and this interaction can cause harm or disease. This is the defining idea of parasitism and is commonly tested in classification. It separates parasites from saprophytes, which depend on dead and decaying matter. The focus is the living host as nutrient source. Hence, a fungus obtaining nutrients from a living host is a correct example of parasitic fungi.
379. Many fungi are effective decomposers mainly because:
ⓐ. They ingest food like animals
ⓑ. They have chloroplasts for photosynthesis
ⓒ. They secrete enzymes for extracellular digestion of complex organic matter
ⓓ. They fix nitrogen in heterocysts
Correct Answer: They secrete enzymes for extracellular digestion of complex organic matter
Explanation: Decomposition requires breaking down complex materials like cellulose and other plant components. Fungi accomplish this by releasing enzymes outside their body onto the substrate. The enzymes digest the material into simpler soluble substances. These substances are then absorbed by the fungal hyphae. This extracellular enzyme secretion is the core mechanism behind their decomposer efficiency. Therefore, fungi are effective decomposers because they secrete enzymes for extracellular digestion.
380. A fungus that obtains nutrients from a host while harming it is best described as showing:
ⓐ. Mutualism
ⓑ. Commensalism
ⓒ. Saprophytism
ⓓ. Parasitism
Correct Answer: Parasitism
Explanation: Parasitism involves one organism benefiting while the other (the host) is harmed. A parasitic fungus draws nutrients from living host tissues, often causing disease or weakening the host. The key idea is nutrient dependence on a living host with negative impact on the host’s health. This is distinct from saprophytism, which uses dead matter. It is also distinct from mutualism, where both benefit. Hence, a fungus harming its host while feeding shows parasitism.
381. In fungi, “symbiotic nutrition” most correctly means:
ⓐ. The fungus makes food by photosynthesis
ⓑ. The fungus feeds only on dead organic matter
ⓒ. The fungus always harms the host to obtain food
ⓓ. The fungus lives in close association with another organism for mutual benefit
Correct Answer: The fungus lives in close association with another organism for mutual benefit
Explanation: Symbiotic nutrition in fungi refers to living in an intimate association with another organism where both partners benefit. The fungus typically gains organic nutrients like sugars, while providing services such as water absorption, mineral uptake, or protection. This relationship is stable and often essential for survival of one or both partners. It is a key ecological strategy distinct from saprophytism and parasitism. Common fungal symbioses include lichens and mycorrhiza. Hence, symbiosis in fungi is mutual-benefit association.
382. Mycorrhiza is a symbiotic association between:
ⓐ. Fungus and roots of higher plants
ⓑ. Fungus and blue-green algae only
ⓒ. Fungus and bacteria in rumen
ⓓ. Fungus and insect wings
Correct Answer: Fungus and roots of higher plants
Explanation: Mycorrhiza refers to the mutualistic association of a fungus with the roots of higher plants. The fungal hyphae spread through soil and increase the effective surface area for absorption. This helps the plant obtain water and minerals efficiently, especially from poor soils. In return, the fungus receives organic food (carbohydrates) from the plant. This association is widespread and important for plant growth and survival. Therefore, mycorrhiza is fungus–plant root symbiosis.
383. In a mycorrhizal association, the fungus primarily benefits by obtaining:
ⓐ. Oxygen directly from the soil
ⓑ. Carbohydrates/organic food from the plant
ⓒ. Chlorophyll from the plant cells
ⓓ. Seeds for reproduction
Correct Answer: Carbohydrates/organic food from the plant
Explanation: The plant partner produces carbohydrates through photosynthesis. In mycorrhiza, a portion of these organic compounds is transferred to the fungal partner. This provides the fungus with a dependable energy and carbon source. The exchange is central to why the relationship is mutualistic. Without this organic supply, the fungus would not gain its key nutritional advantage. Hence, the fungus benefits by receiving carbohydrates from the plant.
384. A major advantage to plants in mycorrhiza is improved:
ⓐ. Ability to photosynthesize in darkness
ⓑ. Production of methane in roots
ⓒ. Uptake of water and minerals from the soil
ⓓ. Formation of true seeds by roots
Correct Answer: Uptake of water and minerals from the soil
Explanation: Fungal hyphae extend far beyond the root surface into the soil. This increases the area available for absorbing water and mineral nutrients. The association is especially effective for improving mineral uptake in nutrient-poor conditions. The plant therefore gains better nourishment and growth support. This benefit explains why many plants commonly form mycorrhiza. Hence, mycorrhiza improves water and mineral uptake in plants.
385. Lichen is best described as a symbiotic association between:
ⓐ. A fungus and an alga/cyanobacterium
ⓑ. A fungus and a plant root
ⓒ. A fungus and a protozoan
ⓓ. A fungus and an earthworm
Correct Answer: A fungus and an alga/cyanobacterium
Explanation: Lichen is a stable mutualistic association of a fungal partner with a photosynthetic partner. The photosynthetic partner may be a green alga or a cyanobacterium. This partnership allows the lichen to survive in habitats where independent partners might struggle. The combination is treated as a classic example of symbiosis involving fungi. The association is therefore defined by fungus plus alga/cyanobacterium. Hence, lichen = fungus with alga/cyanobacterium.
386. In lichens, the photosynthetic partner mainly provides:
ⓐ. Water absorption through hyphae
ⓑ. Anchoring to rocks and bark
ⓒ. Mineral uptake from soil
ⓓ. Organic food (carbohydrates) produced by photosynthesis
Correct Answer: Organic food (carbohydrates) produced by photosynthesis
Explanation: The photosynthetic partner in lichens synthesizes carbohydrates using light energy. These organic compounds serve as the food source for the fungal partner. This exchange is the nutritional foundation of the lichen relationship. The fungal partner depends on this carbon supply to grow and maintain the association. Therefore, the photosynthetic partner’s major contribution is food production. Hence, it provides organic food made by photosynthesis.
387. In lichens, the fungal partner mainly contributes:
ⓐ. Chlorophyll-based photosynthesis
ⓑ. Protection and support, including water retention for the photosynthetic partner
ⓒ. Seed formation for dispersal
ⓓ. Nitrogen fixation using heterocysts
Correct Answer: Protection and support, including water retention for the photosynthetic partner
Explanation: The fungal partner forms the main body of the lichen and provides structural support. It helps in retaining moisture and offers protection from harsh environmental conditions. This allows the photosynthetic partner to function effectively even in challenging habitats. The fungus also aids in anchoring the lichen to surfaces like rocks or tree bark. These protective and supportive roles maintain stability of the association. Hence, the fungal partner contributes protection and water retention support.
388. The term “symbiont” in fungal context most directly refers to fungi forming associations like:
ⓐ. Only saprophytic growth on dead matter
ⓑ. Only parasitic infection of crops
ⓒ. Lichens and mycorrhiza
ⓓ. Only free-living unicellular forms
Correct Answer: Lichens and mycorrhiza
Explanation: Symbiont refers to an organism living in a close association with another organism. In fungi, the most standard examples of symbiotic life are lichens and mycorrhiza. These associations involve mutual benefit and stable coexistence. They are emphasized because they show how fungi obtain nutrition through partnership rather than only decomposition or parasitism. This concept is central to fungal ecological roles. Hence, lichens and mycorrhiza represent fungal symbiosis.
389. Lichens are commonly used as indicators of air pollution because they are:
ⓐ. Always found only in polluted cities
ⓑ. Strictly parasites of humans
ⓒ. The only organisms that can fix nitrogen
ⓓ. Sensitive to pollutants in the atmosphere
Correct Answer: Sensitive to pollutants in the atmosphere
Explanation: Lichens absorb water and dissolved substances directly from the air and rainfall over their surface. Because of this direct exposure, they respond strongly to atmospheric pollutants. Their presence, absence, or poor growth can reflect air quality in a region. This sensitivity makes them useful biological indicators of pollution. The concept is widely used in environmental biology. Hence, lichens indicate air pollution due to their pollutant sensitivity.
390. A correct statement about symbiotic nutrition in fungi is:
ⓐ. It allows fungi to obtain nutrients through mutual exchange with a partner organism
ⓑ. It means fungi always kill the host to obtain food
ⓒ. It means fungi can produce food only by photosynthesis
ⓓ. It means fungi can live only on dead remains
Correct Answer: It allows fungi to obtain nutrients through mutual exchange with a partner organism
Explanation: In fungal symbiosis, nutrition is achieved through exchange rather than one-sided exploitation. The fungus typically gains organic food, while providing benefits like mineral absorption, water retention, or protection. This mutual exchange supports survival in difficult environments and improves growth of the partners. Such associations are ecologically significant and common in nature. They represent a distinct nutritional strategy compared with saprophytes and parasites. Hence, symbiotic nutrition enables mutual nutrient exchange with a partner organism.
391. Vegetative reproduction in fungi by fragmentation means:
ⓐ. A single hypha or mycelium breaks into pieces and each piece grows into a new fungus
ⓑ. Formation of seeds inside a fruit
ⓒ. Fusion of two gametes to form a zygote
ⓓ. Production of spores only in sporangia
Correct Answer: A single hypha or mycelium breaks into pieces and each piece grows into a new fungus
Explanation: Fragmentation is a vegetative method where the fungal body (mycelium) breaks into smaller fragments. Each fragment has the ability to grow and develop into a complete new mycelium. This works effectively because fungal hyphae can regenerate and extend rapidly. It does not require gamete formation or fertilization. The method is common in filamentous fungi where mycelium spreads widely. Hence, fragmentation is breaking of mycelium into pieces that each form a new fungus.
392. Budding as a vegetative method in fungi is best described as:
ⓐ. Splitting of mycelium into equal fragments
ⓑ. Formation of a small outgrowth (bud) that separates to form a new individual
ⓒ. Formation of a zygospore after fusion
ⓓ. Spore production inside asci only
Correct Answer: Formation of a small outgrowth (bud) that separates to form a new individual
Explanation: Budding involves the development of a small projection on the parent cell. The nucleus divides and one copy moves into the bud as it enlarges. The bud may detach and live independently as a new organism. This is a typical vegetative reproduction method in unicellular fungi such as yeast. It is distinct from fragmentation, which involves breaking of mycelium. Therefore, budding is formation of a small outgrowth that separates to form a new individual.
393. Which pairing correctly matches vegetative reproduction method with its description in fungi?
ⓐ. Fragmentation — outgrowth from a parent cell
ⓑ. Budding — breaking of mycelium into pieces
ⓒ. Fragmentation — breaking of fungal body into pieces that grow into new individuals
ⓓ. Budding — formation of spores after fertilization
Correct Answer: Fragmentation — breaking of fungal body into pieces that grow into new individuals
Explanation: Fragmentation is a vegetative process where the fungal body (usually mycelium) breaks into parts. Each part retains the ability to grow into a complete fungus because hyphae regenerate efficiently. Budding, in contrast, is an outgrowth method typical of yeast. Fertilization-related processes are sexual, not vegetative. Therefore, the correct match is fragmentation with mycelial breaking and regrowth. Hence, fragmentation is correctly paired with breaking into pieces that form new individuals.
394. Budding is most commonly associated with:
ⓐ. Yeast-like unicellular fungi
ⓑ. Filamentous fungi forming large mycelium only
ⓒ. Cyanobacteria in ponds
ⓓ. Archaebacteria in salt pans
Correct Answer: Yeast-like unicellular fungi
Explanation: Budding is a common vegetative reproduction method in unicellular fungi, especially yeast. In this process, a bud forms on the parent cell and grows into a new cell. This method suits unicellular body organization rather than large mycelial networks. It allows rapid population increase in favorable conditions. This association is a standard, frequently tested point in fungal reproduction. Hence, budding is most commonly associated with yeast-like unicellular fungi.
395. In vegetative reproduction, fungi generally form new individuals:
ⓐ. Only by producing seeds
ⓑ. Only after fusion of two gametes
ⓒ. Without gamete formation and fertilization
ⓓ. Only by meiosis in a fruiting body
Correct Answer: Without gamete formation and fertilization
Explanation: Vegetative reproduction involves formation of new individuals from somatic (body) parts. It does not involve formation of gametes or their fusion. Methods like fragmentation and budding are based on mitotic division and regeneration. This allows rapid multiplication when conditions are favorable. The process is therefore simpler and faster than sexual reproduction. Hence, vegetative reproduction occurs without gamete formation and fertilization.
396. A correct feature of fragmentation in fungi is that it is most effective because:
ⓐ. Fragmentation requires fertilization to occur
ⓑ. Fungal cells contain chloroplasts to rebuild tissues
ⓒ. Fungi form seeds that germinate quickly
ⓓ. Fungal mycelium has high regenerative capacity and can grow from pieces
Correct Answer: Fungal mycelium has high regenerative capacity and can grow from pieces
Explanation: Fungal hyphae can extend and regenerate rapidly, allowing a small fragment to establish a new mycelium. This regenerative capacity makes fragmentation an efficient vegetative method. Because the mycelium is already adapted for absorption and growth, fragments can quickly colonize new substrates. The process does not involve chloroplasts or seed formation, and it does not require fertilization. This explains why fragmentation is a common reproductive strategy in filamentous fungi. Hence, fragmentation is effective due to high regenerative capacity of mycelium.
397. In budding, the new individual originates as:
ⓐ. A spore formed after meiosis
ⓑ. A bud-like outgrowth from the parent cell
ⓒ. A broken piece of mycelium
ⓓ. A zygote formed by gamete fusion
Correct Answer: A bud-like outgrowth from the parent cell
Explanation: Budding begins with the formation of a small outgrowth on the parent fungal cell. This bud enlarges as the nucleus divides and one daughter nucleus enters it. The bud may remain attached briefly or separate to form a new individual. This is a vegetative method and does not involve zygote formation. The bud origin is the defining feature of budding. Therefore, the new individual originates as a bud-like outgrowth from the parent cell.
398. Which statement best distinguishes budding from fragmentation in fungi?
ⓐ. Budding involves outgrowth from a single cell; fragmentation involves breaking of mycelium into parts
ⓑ. Budding occurs only after fertilization; fragmentation never occurs
ⓒ. Budding produces seeds; fragmentation produces flowers
ⓓ. Budding occurs only in plants; fragmentation occurs only in animals
Correct Answer: Budding involves outgrowth from a single cell; fragmentation involves breaking of mycelium into parts
Explanation: Budding is typically a unicellular process where a new cell forms as an outgrowth from the parent cell. Fragmentation is a filamentous process where the mycelium breaks into pieces and each piece grows independently. This difference is based on the structure involved in forming the new individual. Both are vegetative and do not require gamete fusion. The distinction is therefore clear and conceptually important in fungal reproduction. Hence, budding is outgrowth-based while fragmentation is mycelial breaking.
399. Vegetative reproduction in fungi is best regarded as a strategy for:
ⓐ. Creating seeds for dispersal
ⓑ. Increasing chromosome number by gamete fusion
ⓒ. Producing genetic variation only through meiosis
ⓓ. Rapid multiplication under favorable conditions
Correct Answer: Rapid multiplication under favorable conditions
Explanation: Vegetative methods like budding and fragmentation allow fungi to increase their numbers quickly. They rely on mitotic division and regeneration, making them efficient and fast. This helps fungi colonize substrates rapidly when resources are abundant. The emphasis is on speed and simplicity rather than genetic reshuffling. Therefore, vegetative reproduction is a strategy for rapid multiplication. Hence, it supports rapid increase in fungal population under favorable conditions.
400. A fungus spreading quickly on a substrate through pieces of mycelium developing into new growth most directly indicates:
ⓐ. Vegetative reproduction by fragmentation
ⓑ. Sexual reproduction by gamete fusion
ⓒ. Photosynthetic reproduction
ⓓ. Seed-based reproduction
Correct Answer: Vegetative reproduction by fragmentation
Explanation: When the mycelium breaks into fragments and each fragment develops into a new growth, the method is fragmentation. This is a classic vegetative reproduction process in filamentous fungi. It explains rapid colonization because each fragment can independently expand into a new mycelial network. No gamete fusion or seed formation is involved in this process. The observation directly matches the definition of fragmentation. Therefore, the spread is due to vegetative reproduction by fragmentation.