GK: Class 12 General Q&A · Page 176
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Write down the type of life cycle found in Fucus.
Fucus (a brown alga) exhibits a diplontic life cycle, where the dominant phase is the diploid sporophyte, and meiosis directly produces haploid gametes without an intervening multicellular gametophyte stage.
- GeneralClass 12All
What are microphylls?
Microphylls are small, simple leaves with a single, unbranched vascular strand (vein), characteristic of certain pteridophytes such as Selaginella and Lycopodium. They contrast with megaphylls, which have complex branching venation.
- GeneralClass 12All
What are gemmae?
Gemmae are multicellular, green asexual reproductive bodies produced in specialized structures called gemma cups in certain bryophytes (e.g., Marchantia). Upon detachment and favorable conditions, each gemma develops into a new independent gametophyte.
- GeneralClass 12All
Name the sex organ which produces antherozoids in Funaria.
The antheridium (male sex organ) produces biflagellated antherozoids (male gametes) in the moss Funaria.
- GeneralClass 12All
What is the function of holdfast in brown algae?
The holdfast is a root-like anchoring structure that attaches brown algae (Phaeophyceae) to substrata such as rocks, preventing dislodgement by water currents and waves. Unlike true roots, holdfasts do not absorb nutrients.
- GeneralClass 12All
Who gave the most popular natural system of classification?
George Bentham and Joseph Dalton Hooker developed the most widely accepted natural classification system for flowering plants, published in their monumental work Genera Plantarum (1862-1883).
- GeneralClass 12All
Name two unicellular algae used as food.
Chlorella: A green microalga rich in proteins, vitamins, and essential amino acids Spirulina: A cyanobacterium (blue-green alga) valued for its high protein content and nutritional supplements
- GeneralClass 12All
What is the basis of cytotaxonomy?
Cytotaxonomy utilizes cytological characteristics—particularly chromosome number, karyotype structure, and chromosomal behavior during cell division—as criteria for taxonomic classification. This approach provides insights into evolutionary relationships and genetic compatibility between organisms.
- GeneralClass 12All
What are zoospores?
Zoospores are flagellated, motile asexual reproductive structures produced by certain algae and fungi. Unlike non-motile spores, zoospores possess one or more flagella that enable active movement through aquatic environments, facilitating dispersal and colonization of new habitats.
- GeneralClass 12All
Give two examples each of Methanogens, Halophiles, and Thermoacidophiles
Solution: METHANOGENS Definition: Anaerobic archaebacteria that produce methane (CH₄) as a metabolic byproduct. Example Habitat Characteristics 1. Methanococcus <td width="25
- GeneralClass 12All
Which feature of Archaebacteria allows them to survive in extreme conditions?
Solution: Archaebacteria possess unique cell wall structures fundamentally different from Eubacteria, enabling survival in extreme environments. KEY STRUCTURAL ADAPTATIONS: CELL WALL COMPOSITION Absence of Peptidoglycan: Unlike Eubacteria, Archaebacteria completely lack peptidoglycan Resistant to antibiotics targeting
- GeneralClass 12All
Why are Archaebacteria special?
Solution: Archaebacteria (now classified in Domain Archaea) are extraordinary prokaryotes with unique biochemical and ecological characteristics that distinguish them from both Eubacteria and Eukaryotes. SPECIAL FEATURES OF ARCHAEBACTERIA: EXTREME HABITAT SPECIALIZATION Archaebacteria thrive in environments hostile to most life forms:
- GeneralClass 12All
How are bacteria grouped on the basis of their shape?
Solution: Bacteria exhibit four primary morphological shapes, used as fundamental classification criteria: 1. COCCUS (Plural: Cocci) Shape: Spherical or oval Size:5-1.0 μm diameter Arrangements: Arrangement Description<
- GeneralClass 12All
Which type of nutrition and reproduction is found in kingdom Monera?
Solution: NUTRITION IN MONERA Bacteria exhibit diverse nutritional strategies: AUTOTROPHIC NUTRITION Photosynthetic Autotrophs (Photoautotrophs): Mechanism: Use light energy to synthesize organic compounds Pigments: Bacteriochlorophyll (different from plant chlorophyll) Types: <
- GeneralClass 12All
Give a characteristic feature of kingdom Monera, in terms of their nucleus and cell wall composition
Solution: Nuclear Characteristics: Nucleoid/Incipient Nucleus: Structure: Primitive, not membrane-bound Genetic Material: Single circular DNA molecule (chromosome) Components: Naked DNA (not associated with histone proteins in Eubacteria) RNA molecules (mRNA, tRNA, rRNA) <stro
- GeneralClass 12All
What are the sole members of the kingdom Monera and mention their habitat?
Solution: Sole Members:Bacteria constitute the exclusive members of Kingdom Monera. Habitat Diversity: Ubiquitous Distribution: Air: Atmospheric bacteria (survive in dust particles, aerosols) Water: Freshwater, marine, estuarine environments Soil: Rhizosphere bacteria, decomposers</l
- GeneralClass 12All
Which type of similarities are reflected in the existing classification system?
Solution: Modern classification systems integrate multiple types of similarities to create comprehensive, evolutionary-based taxonomic frameworks: 1. Morphological Similarities External Features: Body shape, size, structural patterns Internal Anatomy: Organ systems, tissue organization Example: Pentadactyl limb structure in vertebrates
- GeneralClass 12All
Why do we expect the criteria of classification to change in the future?
Solution: Classification systems evolve continuously as scientific understanding deepens. Several factors drive these changes: 1. Improved Understanding of Characteristics Molecular Biology: DNA/RNA sequencing reveals hidden relationships Biochemical Markers: Protein structure analysis Cytological Studies: Ultrastructural details via electron microscopy</li
- GeneralClass 12All
In which kingdom did Whittaker place Chlamydomonas and Chlorella? What was their earlier position in the two-kingdom system?
Whittaker's Classification (1969): Kingdom: Protista Rationale: Unicellular eukaryotic organisms with simple organization Earlier Position (Two-Kingdom System): Kingdom: Plantae Group: Algae (Thallophyta) Reason: Presence of cell wall and photosynthetic capability Comparative A
- GeneralClass 12All
Write down three drawbacks of two-kingdom classification system
Solution: The two-kingdom classification (Plantae and Animalia) had several fundamental limitations: Drawback 1: Failed to Distinguish Unicellular and Multicellular Organisms Grouped bacteria (E. coli) with complex plants No recognition of cellular complexity levels Ignored fundamental organizational differences Drawback 2: Did Not Differentiate Eukaryotes and Prokaryotes <ul