Examkin

Variety of Organisms

256 questions

All types256Multiple choice140True / False19Matching64Ordering33
Question 121Question →

Match each fungal representative with its characteristic structural organization and spore-bearing mechanism.

Click a left item, then click its matching right item

Items

*Rhizopus stolonifer* (Bread mould)
*Saccharomyces cerevisiae* (Yeast)
*Agaricus bisporus* (Mushroom)
*Penicillium chrysogenum* (Blue-green mould)

Matches

Show answer & explanation

Answer

The correct pairings match *Rhizopus stolonifer* with aseptate coenocytic hyphae and terminal sporangia; *Saccharomyces cerevisiae* with non-filamentous unicellular thallus reproducing by budding; *Agaricus bisporus* with dikaryotic septate mycelium forming a basidiocarp with gills; and *Penicillium chrysogenum* with septate hyphae producing brush-like conidiophores.
Each fungal representative is accurately matched to its defining cellular architecture and spore generation structure: *Rhizopus stolonifer* exhibits coenocytic hyphae with terminal sporangia; *Saccharomyces cerevisiae* exists as a unicellular thallus reproducing by budding; *Agaricus bisporus* builds a macroscopic basidiocarp with gill lamellae; and *Penicillium chrysogenum* forms septate hyphae with brush-like conidiophores.

Step-by-Step Solution

1
Analyze the hyphal structure and asexual reproduction of *Rhizopus stolonifer*.
Identify that *Rhizopus* is a zygomycete mould with coenocytic (aseptate) hyphae producing internal sporangiospores inside globose sporangia.
Zygomycota moulds are characterized by lack of septa in vegetative hyphae and reproduction via sporangia.
2
Examine the cellular organization of unicellular yeast (*Saccharomyces cerevisiae*).
Identify that yeast exists as discrete single cells that do not form hyphal filaments and undergo cell outgrowth (budding).
Ascomycetes yeasts are secondarily unicellular and utilize budding for rapid asexual multiplication.
3
Evaluate the complex multicellular fruiting structure of *Agaricus bisporus*.
Identify that edible mushrooms are basidiomycetes with septate dikaryotic hyphae forming a cap with gills bearing basidiospores.
Basidiomycota produce macroscopic basidiocarps with gills to optimize wind dispersal of sexual basidiospores.
4
Differentiate *Penicillium chrysogenum* from *Rhizopus* based on hyphal septation and conidial arrangement.
Identify that *Penicillium* has septate hyphae forming brush-shaped conidiophores bearing external chains of conidia rather than enclosed sporangia.
Conidial fungi generate exposed asexual spores directly on specialized branched structures (penicilli).

Key Concept

Structural Diversity and Reproductive Adaptation in Kingdom Fungi
Question 122Question →

Why are viruses classified as acellular entities rather than true living cells?

Show answer & explanation

Answer: They lack cytoplasm and membrane-bound cellular organelles.

Answer

Viruses are classified as acellular entities because they lack a cytoplasm, cell membrane, and membrane-bound organelles necessary for cellular life.
The correct answer highlights that viruses lack cytoplasm and membrane-bound cellular organelles. Unlike eukaryotic or prokaryotic cells, viruses are biological entities consisting solely of a nucleic acid core surrounded by a protein coat (capsid). Because they lack cellular organization and metabolic machinery, they are classified as acellular.

Step-by-Step Solution

1
Define the key structural requirements of a cellular organism.
A true cell must contain a cell membrane, cytoplasm, and internal organelles (such as ribosomes) to carry out metabolic processes.
Establishing cell theory baseline criteria allows comparison with viral structure.
2
Analyze the structural organization of a virus.
A virus consists simply of genetic material (DNA or RNA) enclosed within a protein coat (capsid), without cytoplasm or organelles.
Identifying the non-cellular components confirms their acellular classification.

Key Concept

Acellular Nature of Viruses
Question 123Question →

An isolated infectious pathogen is treated separately with a lipolytic enzyme that hydrolyzes phospholipids and an enzyme that selectively degrades ribose-containing nucleic acids. The pathogen retains its infectivity following lipid hydrolysis but loses infectivity after ribose nucleic acid degradation. Based on these structural properties, which of the following best classifies this pathogen?

Show answer & explanation

Answer: Non-enveloped RNA virus

Answer

Non-enveloped RNA virus
The pathogen's resistance to phospholipid hydrolysis confirms the absence of a outer lipid membrane envelope surrounding its protein capsid. Its loss of infectivity upon exposure to ribose nucleic acid degradation proves that its genetic material is RNA rather than DNA. Therefore, the pathogen is correctly identified as a non-enveloped RNA virus.

Step-by-Step Solution

1
Analyze the effect of phospholipid hydrolysis on pathogen infectivity.
The pathogen remains infectious, indicating it does not possess a phospholipid bilayer membrane or lipid envelope.
Enveloped viruses and cellular organisms rely on intact phospholipid membranes for host infection and structural integrity.
2
Analyze the effect of ribose nucleic acid degradation on infectivity.
The pathogen loses infectivity, confirming its genetic material is RNA containing ribose sugars.
Ribose-degrading enzymes target RNA specifically without degrading deoxyribose nucleic acid (DNA).
3
Synthesize the structural features to classify the organism.
The pathogen is a non-enveloped RNA virus.
Combining a protein capsid lacking a lipid envelope with an RNA genome uniquely defines a non-enveloped RNA virus.

Key Concept

Structural composition of viruses: viral envelopes and genome types
Estimated Time:1m 30s
Question 124Question →

During a botanical field survey, two seed-bearing plants, designated as Plant P and Plant Q, are analyzed for their structural and reproductive traits. Plant P displays ovules borne exposed on the surfaces of cone scales without carpels, while Plant Q displays ovules completely enclosed within an ovary wall. Which of the following statements correctly compares the reproductive and anatomical characteristics of these two plant groups?

Show answer & explanation

Answer: Plant P produces naked seeds relying on a pre-fertilization haploid female gametophyte for embryo nutrition, whereas Plant Q forms seeds enclosed within fruits following double fertilization.

Answer

Plant P produces naked seeds relying on a pre-fertilization haploid female gametophyte for embryo nutrition, whereas Plant Q forms seeds enclosed within fruits following double fertilization.
The correct answer accurately distinguishes gymnosperms from angiosperms. Plant P is a gymnosperm, which produces naked seeds exposed on scales and utilizes a haploid female gametophyte as nutritive tissue formed prior to fertilization. Plant Q is an angiosperm, which encloses its ovules within an ovary that matures into a fruit, and relies on double fertilization to produce a triploid endosperm.

Step-by-Step Solution

1
Identify the taxonomic divisions of Plant P and Plant Q based on ovule enclosure.
Plant P represents a gymnosperm (naked seed plant) because ovules are exposed on cone scales without a surrounding carpel. Plant Q represents an angiosperm (flowering plant) because ovules are enclosed within an ovary wall.
The defining morphological criterion separating gymnosperms from angiosperms is whether ovules/seeds are exposed on megasporophylls or enclosed within carpels.
2
Analyze the reproductive features and nutritive tissue origins of gymnosperms and angiosperms.
Gymnosperms develop a haploid (nn) nutritive tissue from the female gametophyte prior to fertilization. Angiosperms undergo double fertilization where one sperm nucleus fuses with the polar nuclei to yield a triploid (3n3n) endosperm, and the ovary wall matures into a protective fruit.
Double fertilization and true fruit development from an ovary wall are key innovations of angiosperms.
3
Evaluate the options to identify the statement that accurately reflects these differences.
The statement that describes Plant P as bearing naked seeds with haploid nutritive tissue and Plant Q as producing enclosed seeds inside fruits after double fertilization is correct.
This statement aligns precisely with gymnosperm and angiosperm anatomical and developmental definitions.

Key Concept

Structural and reproductive distinctions between gymnosperms and angiosperms
Question 125Question →

Match each characteristic of viruses in Column A with its corresponding biological implication in Column B.

Click a left item, then click its matching right item

Items

Absence of metabolic machinery and organelles
Ability to form crystals outside host cells
Presence of nucleic acid (DNA or RNA)
Specific surface glycoprotein spikes

Matches

Show answer & explanation

Answer

Absence of metabolic machinery and organelles matches with Requires obligate intracellular parasitism for replication; Ability to form crystals outside host cells matches with Demonstrates non-living chemical property when isolated from host; Presence of nucleic acid matches with Provides genetic instructions for viral protein synthesis; Specific surface glycoprotein spikes match with Enables recognition and attachment to host membrane receptors.
The correct matches align viral structural characteristics with their exact biological implications: lack of cellular organelles enforces obligate intracellular parasitism, crystallization demonstrates non-living chemical behavior outside a host, nucleic acids provide genetic hereditary information, and glycoprotein spikes facilitate specific binding to host cell surface receptors.

Step-by-Step Solution

1
Analyze the biological implication of lacking metabolic machinery
Lacking organelles means viruses cannot generate ATP or synthesize proteins independently, making them obligate intracellular parasites.
Viruses rely entirely on the host cell's metabolic infrastructure.
2
Analyze the implication of viral crystallization
Forming crystals in non-living environments behaves like chemical compounds rather than living cells.
Crystallization reflects metabolic inertness outside a living host.
3
Analyze the function of viral nucleic acid
Nucleic acid (either DNA or RNA) carries genetic code for replication.
The genome directs host ribosomes to manufacture viral components.
4
Analyze the role of surface glycoprotein spikes
Spikes mediate host specificity by anchoring to host cell surface receptors.
Viral attachment depends on specific molecular fitting between spikes and host receptors.

Key Concept

Viral Characteristics and Structure
Question 126Question →

Match each fungal structure or specialized cell type with its corresponding diagnostic anatomical or reproductive characteristic.

Click a left item, then click its matching right item

Items

Rhizoid (*Rhizopus*)
Basidium (*Agaricus*)
Zygospore (*Rhizopus*)
Pseudohypha (*Saccharomyces*)

Matches

Show answer & explanation

Answer

Rhizoid (*Rhizopus*) matches the specialized root-like hyphal branch that penetrates substrate for extracellular digestion; Basidium (*Agaricus*) matches the microscopic club-shaped structure lining mushroom gills where meiosis yields sexual spores; Zygospore (*Rhizopus*) matches the thick-walled, resistant zygotic structure from gametangial fusion; Pseudohypha (*Saccharomyces*) matches the short chain of unseparated daughter cells formed during budding.
Each fungal archetype possesses unique structural and reproductive adaptations: *Rhizopus* utilizes subterranean-like rhizoids for substrate penetration and enzyme secretion, as well as zygospores for sexual survival; *Agaricus* develops basidia on gill surfaces for sexual basidiospore production; and *Saccharomyces* forms pseudohyphae when budding daughter cells remain attached in chains.

Step-by-Step Solution

1
Analyze the nutrition and vegetative structures of moulds
Identify that rhizoids in *Rhizopus* serve an anchoring and absorptive function by penetrating the growth medium and secreting extracellular enzymes.
Rhizoids are specialized subterranean-like hyphae distinct from aerial sporangiophores and horizontal stolons.
2
Evaluate the reproductive structures of macrofungi (mushrooms)
Identify the basidium as the diagnostic spore-bearing club cell of *Agaricus* situated on the gill surfaces.
Karyogamy followed by meiosis occurs inside the basidium, extruding four haploid basidiospores externally.
3
Examine sexual reproduction in Zygomycota
Connect the zygospore to gametangial conjugation in moulds like *Rhizopus*.
When opposite mating strains meet, multinucleate gametangia fuse to create a highly resistant, dark, thick-walled zygospore.
4
Analyze asexual growth patterns in unicellular yeasts
Associate pseudohyphae with budding in *Saccharomyces*.
When budded cells fail to detach during rapid mitotic growth, they form elongated, linked chains known as pseudohyphae.

Key Concept

Structural and reproductive differentiation among Kingdom Fungi archetypes (moulds, yeasts, and mushrooms)
Question 127Question →

During the light-dependent stage of photosynthesis in the unicellular green alga *Chlamydomonas*, water molecules undergo photolysis inside the chloroplast. Which molecule is released as a direct byproduct of this light reaction?

Show answer & explanation

Answer: Oxygen

Answer

Oxygen gas is the direct byproduct released when water molecules undergo photolysis during the light-dependent stage of photosynthesis in unicellular green algae.
During photolysis in the light-dependent stage of photosynthesis in unicellular green algae, light energy absorbed by chlorophyll drives the splitting of water molecules, yielding hydrogen ions, electrons, and oxygen gas as a byproduct.

Step-by-Step Solution

1
Identify the specific photosynthetic process occurring in the chloroplast of the unicellular alga.
The process is photolysis of water during the light-dependent stage of photosynthesis.
Photolysis splits water molecules using light energy absorbed by photosynthetic pigments.
2
Determine the chemical products resulting from the photolysis reaction.
Water (2H2O2H_2O) breaks down into hydrogen ions (4H+4H^+), electrons (4e−4e^-), and oxygen gas (O2O_2).
Water serves as the primary electron donor to replace electrons excited from chlorophyll.
3
Identify which of the resulting substances is released as a gas into the environment.
Oxygen gas (O2O_2) diffuses out of the organelle and cell as a byproduct.
Hydrogen ions and electrons are retained for ATP and NADPH synthesis, whereas molecular oxygen is released.

Key Concept

Photolysis of water in unicellular algal photosynthesis
Question 128Question →

A botanist analyzed three cryptogamic plant specimens (XX, YY, and ZZ) collected from different microhabitats during an ecological survey. Specimen XX consists of an simple, undifferentiated thallus without vascular tissues or organ differentiation; Specimen YY possesses multicellular rhizoids and a dominant gametophytic generation lacking lignified conducting elements; Specimen ZZ exhibits a dominant sporophytic generation with true roots, fronds, and lignified xylem and phloem. Which of the following correctly categorizes specimens XX, YY, and ZZ into their respective taxonomic divisions?

Show answer & explanation

Answer: Specimen X is a Thallophyte, Specimen Y is a Bryophyte, and Specimen Z is a Pteridophyte.

Answer

Specimen X is a Thallophyte, Specimen Y is a Bryophyte, and Specimen Z is a Pteridophyte.
The classification is derived from key evolutionary and anatomical distinctions among cryptogams: Thallophytes (Specimen X) have an unsegmented thallus with no vascular system; Bryophytes (Specimen Y) possess multicellular rhizoids and an avascular, gametophyte-dominant body; Pteridophytes (Specimen Z) are vascular cryptogams characterized by true vegetative organs (roots, stems, leaves) and a dominant sporophyte phase.

Step-by-Step Solution

1
Analyze the structural characteristics of Specimen X
Specimen X has an undifferentiated thallus body without root, stem, or leaf differentiation and lacks specialized conducting tissue, placing it in Division Thallophyta (Algae/Fungi).
Thallophytes represent the simplest plant organisation characterized by a non-vascular thallus body.
2
Evaluate the reproductive and anatomical features of Specimen Y
Specimen Y possesses rhizoids and displays a dominant gametophytic phase (nn) while lacking true vascular tissues (xylem and phloem), identifying it as a Bryophyte (mosses/liverworts).
Bryophytes are non-vascular land plants with gametophyte-dominant alternation of generations.
3
Assess the vascularization and alternation of generations in Specimen Z
Specimen Z features true roots, leaves, lignified vascular tissues (xylem and phloem), and a dominant sporophytic phase (2n2n), placing it in Division Pteridophyta (ferns).
Pteridophytes are seedless vascular plants exhibiting a dominant, independent sporophyte generation.

Key Concept

Taxonomic differentiation of lower plant groups based on body organisation, vascularization, and dominant life cycle generation
Question 129Question →

A culture of bacteria in a nutrient-rich broth undergoes rapid population expansion under optimal environmental conditions. Which mechanism is primarily responsible for the asexual reproduction and multiplication of these prokaryotic organisms?

Show answer & explanation

Answer: Binary fission, resulting in two genetically identical daughter cells

Answer

Binary fission, resulting in two genetically identical daughter cells
In Kingdom Monera, bacteria reproduce asexually under favorable conditions through binary fission. The single circular chromosome replicates, attaches to the plasma membrane, and the cell elongates before invaginating to yield two genetically identical cells.

Step-by-Step Solution

1
Identify the biological group and kingdom of bacteria
Bacteria belong to Kingdom Monera and are prokaryotic organisms.
Prokaryotic cells lack membrane-bound organelles, a true nucleus, and mitotic structures.
2
Determine the standard mode of cellular reproduction in prokaryotes under favorable conditions
Prokaryotes replicate their single circular chromosome and divide by binary fission.
Binary fission allows rapid exponential growth by splitting one parent cell into two identical daughter cells without mitosis.

Key Concept

Bacterial Reproduction via Binary Fission
Question 130Question →

Arrange the following sequential stages of holozoic nutrition and intracellular digestion in *Amoeba proteus* from the initial capture of food to the elimination of waste.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence of holozoic nutrition in *Amoeba proteus* is: Extension of pseudopodia to capture food → Enclosure of food within a food vacuole → Discharge of hydrolytic enzymes by lysosomes → Absorption of soluble nutrients into cytoplasm → Exocytosis of insoluble residual waste.
Holozoic nutrition in *Amoeba* follows a strict sequence: pseudopodia surround the food, a food vacuole forms around it, lysosomes release digestive enzymes into the vacuole, digested soluble nutrients are absorbed into the cytoplasm, and finally undigested waste is egested via exocytosis.

Step-by-Step Solution

1
Identify the initial contact and engulfment phase.
Pseudopodia extend to encapsulate the prey item.
Phagocytosis in Amoeba relies on pseudopodial engulfment.
2
Identify the vacuole formation phase.
The food particle is enclosed in a food vacuole.
Membrane fusion isolates the ingested prey inside the cell cytoplasm.
3
Identify the chemical digestion phase.
Lysosomes release hydrolytic enzymes into the food vacuole.
Enzymatic hydrolysis degrades complex organic matter into simpler solutes.
4
Identify the nutrient assimilation phase.
Soluble nutrients diffuse into the cytoplasm.
Digested simple nutrients must be absorbed into the cytoplasm for cellular growth and metabolism.
5
Identify the egestion phase.
Insoluble waste is expelled by exocytosis.
Undigested materials are removed by fusing the vacuole membrane with the plasma membrane.

Key Concept

Holozoic Nutrition and Intracellular Digestion in Amoeba
Estimated Time:1m 30s
Question 131Question →

A terrestrial cryptogam exhibits an independent, vascularized dominant sporophyte phase alongside a tiny, photosynthetic prothallus that relies on a film of water for swimming sperm. Based on these anatomical and life cycle features, to which plant division does this specimen belong, and how does its dominant generation compare to that of bryophytes?

Show answer & explanation

Answer: Pteridophyta, possessing a dominant diploid sporophyte generation, whereas bryophytes have a dominant haploid gametophyte generation.

Answer

The plant belongs to Pteridophyta, possessing a dominant diploid sporophyte generation, unlike bryophytes which feature a dominant haploid gametophyte generation.
Pteridophytes are vascular cryptogams whose dominant, prominent life cycle stage is the diploid sporophyte (2n2n). Bryophytes, on the other hand, lack true vascular tissues and are dominated by the haploid gametophyte (nn) stage. Both groups remain reliant on free water for motile flagellated sperm during sexual reproduction.

Step-by-Step Solution

1
Analyze the structural and reproductive characteristics described in the stem.
The presence of true vascular tissue (xylem and phloem) and an independent sporophyte phase eliminates Thallophyta and Bryophyta, identifying the plant as a Pteridophyte.
Among cryptogams, only Pteridophytes possess true vascular bundles and an independent diploid sporophyte phase.
2
Compare the dominant phase of alternation of generations between Pteridophytes and Bryophytes.
Pteridophytes feature a dominant diploid (2n2n) sporophyte, whereas Bryophytes feature a dominant haploid (nn) gametophyte.
Evolutionary trends in land plant adaptation demonstrate a transition from gametophyte-dominated life cycles in bryophytes to sporophyte-dominated life cycles in pteridophytes.

Key Concept

Alternation of generations and vascular differentiation in plant cryptogams (Thallophytes, Bryophytes, and Pteridophytes)
Question 132Question →

During plant evolution, non-seed bearing plants (cryptogams) exhibit important structural and developmental transitions. Which structural feature uniquely characterizes mature pteridophytes when compared to bryophytes?

Show answer & explanation

Answer: A dominant, independent sporophyte generation containing true vascular tissue

Answer

Pteridophytes are distinguished from bryophytes by having a dominant, free-living sporophyte generation that possesses true vascular tissues (xylem and phloem).
The correct response highlights the evolutionary innovation of pteridophytes: they possess a dominant, multicellular, free-living sporophyte equipped with lignified vascular tissues (xylem and phloem) for water and nutrient conduction.

Step-by-Step Solution

1
Compare the dominant generation between bryophytes and pteridophytes.
Bryophytes have a dominant gametophyte stage, whereas pteridophytes have a dominant sporophyte stage.
Plant kingdom evolution progresses from gametophyte-dominated life cycles to sporophyte-dominated life cycles.
2
Evaluate the presence of internal conducting tissues in both groups.
Bryophytes lack vascular tissues (tracheophytes), whereas pteridophytes are vascular plants equipped with xylem and phloem.
Lignified vascular tissue evolved in pteridophytes, allowing them to achieve larger physical size and structural support compared to non-vascular bryophytes.

Key Concept

Structural differentiation and life cycle dominance in cryptogamic plant divisions
Question 133Question →

Arrange the heart chambers and associated structures of a typical bony fish (Class Pisces) in the correct sequence through which deoxygenated blood flows, starting from the chamber that receives venous blood from the body to the vessel leading to the gills.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of deoxygenated blood flow through a fish heart is: Sinus venosus → Atrium → Ventricle → Bulbus arteriosus.
In fish (Class Pisces), deoxygenated blood flows through a single-circuit heart in a strict linear pathway: it enters the sinus venosus from the body, moves to the atrium, passes into the thick muscular ventricle, and exits via the bulbus arteriosus toward the ventral aorta and gills.

Step-by-Step Solution

1
Identify the initial collecting chamber for venous blood returning from body tissues.
Deoxygenated blood first enters the thin-walled sinus venosus.
The sinus venosus functions as the primary receiving reservoir for systemic venous blood in fish.
2
Trace blood movement from the initial collecting reservoir into the first main heart chamber.
Blood passes from the sinus venosus into the atrium.
Contraction of the sinus venosus propels blood across the sinoatrial valve into the atrium.
3
Follow blood flow from the atrium into the main pumping chamber.
Blood moves from the atrium into the muscular ventricle.
Atrial contraction drives blood across the atrioventricular valve into the heavy-walled ventricle.
4
Determine the exit pathway out of the heart toward the respiratory surfaces.
Blood is pumped from the ventricle through the bulbus arteriosus into the ventral aorta leading to the gills.
The elastic bulbus arteriosus maintains continuous forward blood flow and buffers pressure fluctuations prior to entering delicate gill capillaries.

Key Concept

Single-circuit cardiac blood flow sequence in Class Pisces
Question 134Question →

Match each unicellular protist listed on the left with its defining structural feature or locomotory organelle on the right.

Click a left item, then click its matching right item

Items

*Amoeba*
*Paramecium*
*Euglena*
*Plasmodium*

Matches

Show answer & explanation

Answer

*Amoeba* matches with pseudopodia locomotion; *Paramecium* matches with cilia locomotion; *Euglena* matches with flagellum and eyespot; *Plasmodium* matches with non-motile spore-forming parasite.
Each protist taxon is accurately paired with its primary locomotory structure or biological characteristic: *Amoeba* utilizes pseudopodia, *Paramecium* uses cilia, *Euglena* possesses a flagellum with an eyespot, and *Plasmodium* is a non-motile spore-forming parasite.

Step-by-Step Solution

1
Identify the locomotory mechanism of *Amoeba*
*Amoeba* extends pseudopodia (false feet) through streaming endoplasm and ectoplasm.
Rhizopod protozoans move exclusively via pseudopodial extension.
2
Identify the characteristic features of *Paramecium*
*Paramecium* is covered in short, hair-like cilia.
Ciliates utilize metachronal waves of cilia to swim through aquatic environments.
3
Identify the features of *Euglena*
*Euglena* uses a long flagellum for swimming and a red eyespot (stigma) for phototaxis.
The stigma directs *Euglena* toward light sources for photosynthesis.
4
Identify the features of *Plasmodium*
*Plasmodium* is a non-motile parasite producing infectious sporozoites.
Apicomplexan protozoa rely on vectors rather than active locomotory structures.

Key Concept

Classification and locomotory organelles of Kingdom Protista
Question 135Question →

A mature virus particle (virion) isolated outside a host cell contains functional ribosomes and metabolic enzymes capable of synthesizing proteins independently.

Show answer & explanation

Answer: False

Answer

The statement is False because viruses lack ribosomes and metabolic enzymes, making them incapable of independent protein synthesis.
The statement is false because viruses are non-cellular (acellular) biological agents that lack ribosomes, cytoplasm, and ATP-generating enzymes, making independent protein synthesis impossible.

Step-by-Step Solution

1
Examine the structural components of an extracellular virion.
A virion consists solely of a nucleic acid genome (DNA or RNA) enclosed within a protein coat (capsid), and occasionally a lipid envelope, but completely lacks cytoplasm and cell organelles.
Structural analysis reveals whether protein translation machinery is present.
2
Assess the metabolic capabilities of viruses outside a host cell.
Without ribosomes or ATP-generating metabolic enzymes, a virus cannot synthesize proteins or carry out metabolic reactions independently.
Confirming the inability to perform independent protein synthesis establishes that the statement is false.

Key Concept

Acellular Nature and Obligate Intracellular Parasitism of Viruses
Question 136Question →

Which of the following structural features distinguishes members of the phylum Platyhelminthes from Coelenterata?

Show answer & explanation

Answer: Possession of three distinct germ layers (triploblastic body plan)

Answer

Possession of three distinct germ layers (triploblastic body plan)
Platyhelminthes (flatworms) represent the simplest animal group to exhibit a triploblastic body plan containing ectoderm, mesoderm, and endoderm. In contrast, Coelenterata (cnidarians) are diploblastic, having only an outer ectoderm and inner endoderm separated by non-cellular mesoglea.

Step-by-Step Solution

1
Analyze the germ layer organization of Coelenterata and Platyhelminthes.
Coelenterata are diploblastic (two germ layers: ectoderm and endoderm), while Platyhelminthes are triploblastic (three germ layers: ectoderm, mesoderm, and endoderm).
The evolutionary emergence of mesoderm in Platyhelminthes provides true muscle tissue and organs, distinguishing them from diploblastic coelenterates.
2
Evaluate the other body features to eliminate incorrect options.
Cnidocytes belong uniquely to coelenterates; pseudocoelom and complete digestive tract belong to roundworms (Nematoda).
Platyhelminthes are acoelomate and possess an incomplete digestive tract with a single opening.

Key Concept

Triploblastic organization in Platyhelminthes vs. diploblastic organization in Coelenterata
Estimated Time:1m 0s
Question 137Question →

Match each viral structural component listed in Column I with its correct biochemical nature or biological function in Column II.

Click a left item, then click its matching right item

Items

Capsid
Viral Envelope
Capsomeres
Glycoprotein Spikes

Matches

Show answer & explanation

Answer

Capsid matches with the complete protective protein shell surrounding the genetic material; Viral Envelope matches with the host-derived lipid bilayer membrane; Capsomeres match with the individual protein subunits determining viral symmetry; Glycoprotein Spikes match with surface proteins essential for host receptor attachment.
Each structural component has a specific chemical identity and function: the capsid serves as the primary protective protein shell for viral DNA or RNA; capsomeres are the fundamental repeating protein units assembling the capsid structure; the envelope is a host-derived lipid membrane modified with viral proteins; glycoprotein spikes mediate specific viral binding to host cell surface receptors.

Step-by-Step Solution

1
Identify the whole protein coat structure versus its individual sub-units
The overall protein shell is the Capsid, whereas the constituent protein monomers are Capsomeres.
Viruses assemble their outer protein shell (capsid) from repeating polypeptide subunits called capsomeres.
2
Determine the origin and nature of the viral outer membrane
The Viral Envelope is a phospholipid membrane derived from host cell plasma or organelle membranes during viral exit.
Viruses lack metabolic pathways to synthesize lipids independently and must acquire membrane envelopes from host cells.
3
Analyze host target binding structures
Glycoprotein Spikes extend from the surface to anchor the virus to specific host cell receptors.
Host tropism is determined by viral attachment proteins recognizing specific complementary cellular surface receptors.

Key Concept

Viral morphology is defined by a nucleic acid genome surrounded by a protein capsid composed of capsomeres, with some viruses possessing an outer host-derived lipid envelope bearing viral spikes.
Question 138Question →

Spermatophytes display distinct vascular and reproductive features that differentiate gymnosperms from angiosperms. Which of the following correctly pairs each spermatophyte structure on the left with its corresponding characteristic description on the right?

Click a left item, then click its matching right item

Items

Microsporangiate cone
Embryo sac
Tracheids with bordered pits
Sieve tube elements with companion cells

Matches

Show answer & explanation

Answer

Microsporangiate cone matches the male reproductive structure in gymnosperms producing microspores; Embryo sac matches the highly reduced female gametophyte enclosed within an angiosperm ovule; Tracheids with bordered pits match the primary water-conducting cell type dominant in gymnosperm xylem; Sieve tube elements with companion cells match the specialized phloem transport tissue characteristic of angiosperms.
Each structural term correctly matches its anatomical or reproductive identity. Gymnosperms utilize microsporangiate cones to generate microspores (pollen) and rely on tracheids for xylem transport. In contrast, angiosperms produce an embryo sac as their female gametophyte and possess sieve tube elements linked with companion cells in their phloem.

Step-by-Step Solution

1
Analyze reproductive structures of Gymnosperms vs Angiosperms
Microsporangiate cones produce pollen (microspores) in gymnosperms, while the embryo sac represents the female gametophyte contained within the angiosperm ovule.
Gymnosperms rely on cone structures for spore production, whereas angiosperms enclose their female gametophyte inside an ovary-enclosed ovule.
2
Analyze vascular tissue differences between Gymnosperms and Angiosperms
Gymnosperms rely primarily on tracheids for water conduction and sieve cells for nutrient transport. Angiosperms feature vessels for water transport and sieve tube elements with companion cells for phloem transport.
Distinct anatomical evolution sets angiosperm vascular efficiency apart from gymnosperms.
3
Pair each left item with its corresponding right item definition
Microsporangiate cone pairs with the male cone description; Embryo sac pairs with the angiosperm female gametophyte; Tracheids pair with gymnosperm xylem elements; Sieve tube elements with companion cells pair with angiosperm phloem tissue.
Matches align accurately with fundamental plant taxonomy and comparative histology.

Key Concept

Comparative vascular and reproductive anatomy of Gymnosperms and Angiosperms
Question 139Question →

Arrange the following sequential events in the reproductive life cycle of a moss (Bryophyta), beginning with the germination of a haploid spore:

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence begins with the germination of a spore into a protonema, followed by the development of leafy gametophytes with sex organs, fertilization via swimming sperm in water, and lastly the growth of the dependent diploid sporophyte.
In mosses (bryophytes), the reproductive cycle starts when a haploid spore germinates into a filamentous protonema. This structure gives rise to the leafy gametophyte, which bears sex organs (antheridia and archegonia). Flagellated sperm swim through water to fertilize the egg inside the archegonium, forming a zygote that develops into the sporophyte generation attached to the parent gametophyte.

Step-by-Step Solution

1
Identify the initial developmental stage following spore dispersal.
A haploid spore germinates on moist soil to form a filamentous, algal-like green structure known as the protonema.
Spores are single-celled reproductive units that initiate the haploid gametophyte phase.
2
Trace gametophyte maturation and gamete container production.
Protonemal buds develop into adult leafy gametophytes that produce male (antheridia) and female (archegonia) reproductive structures.
The dominant haploid gametophyte produces gametes by mitosis.
3
Identify the fertilization mechanism.
Flagellated sperm released from antheridia swim through a surface layer of water to reach and fertilize the egg in an archegonium, forming a diploid zygote.
Bryophytes require liquid water for sexual reproduction because sperm are flagellated.
4
Determine the final stage of sporophyte generation formation.
The diploid zygote undergoes mitotic division to form a sporophyte consisting of a foot, seta, and spore-bearing capsule, which stays attached to the gametophyte.
In bryophytes, the diploid sporophyte is nutritionally dependent on the autotrophic gametophyte throughout its lifespan.

Key Concept

Bryophyte life cycle and alternation of generations
Question 140Question →

Which of the following structural features is present in all complete virus particles (virions), regardless of the host species they infect?

Show answer & explanation

Answer: A protein capsid enclosing the nucleic acid genome

Answer

A protein capsid enclosing the nucleic acid genome
All virions fundamentally consist of a nucleic acid genome (either DNA or RNA) surrounded by a protein coat called a capsid. This basic nucleoprotein structure is universal to all viruses across all host types.

Step-by-Step Solution

1
Identify universal components of a virion
Every intact infectious virus particle consists minimally of a nucleic acid core enclosed by a protein coat termed a capsid.
The nucleoprotein complex (capsid plus genome) is the defining architectural unit of all viruses.
2
Evaluate variable and cellular components against viral characteristics
Lipid envelopes are restricted to enveloped viruses, while cytoplasm, organelles, and dual DNA/RNA genomes do not exist in viruses.
Viruses are acellular obligate intracellular parasites containing only one type of nucleic acid and lacking metabolic machinery.

Key Concept

Universal Viral Structure and Acellular Nature
Estimated Time:1m 0s
PreviousPage 7 / 13Next
Variety of Organisms Practice Questions — JAMB UTME — Page 7 | Examkin