GK: Class 12 General Q&A · Page 175
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is the storage food in different classes of algae?
Class Storage Product Chlorophyceae Starch Phaeophyceae Laminarin, Mannitol Rhodophyceae <p
- GeneralClass 12All
Draw a well-labelled diagram of Fucus.
Fucus exhibits typical brown algae morphology with: Holdfast: Anchoring structure Stipe: Stem-like portion Frond: Photosynthetic blade with midrib Air bladders: Gas-filled structures providing buoyancy
- GeneralClass 12All
Give two general characteristics of angiosperms.
Reproductive structures: Produce flowers containing specialized reproductive organs; seeds develop within fruits (mature ovaries) Habitat diversity: Exhibit remarkable ecological adaptability, occupying virtually all terrestrial and many aquatic habitats
- GeneralClass 12All
Name the algae from which agar is obtained. Give two uses of agar.
Source algae: Gelidium and Gracilaria (red algae) Uses of agar: Microbiological culture medium: Provides solid substrate for bacterial and fungal cultivation Food industry: Gelling agent in ice creams, jellies, and confectionery
- GeneralClass 12All
Give two general characteristics of Rhodophyceae.
Pigmentation: Possess r-phycoerythrin (red pigment) that masks chlorophyll, enabling photosynthesis at greater depths where red wavelengths penetrate Habitat: Predominantly marine, with greater diversity in warmer tropical and subtropical waters
- GeneralClass 12All
In pteridophytes how are haploid spores produced?
In the dominant diploid sporophyte, specialized leaves called sporophylls bear sporangia. Within sporangia, diploid spore mother cells undergo meiosis, producing haploid spores that disperse and germinate into gametophytes.
- GeneralClass 12All
What is nucellus in gymnosperms?
The nucellus is the megasporangium tissue that comprises the central portion of the ovule. A single megaspore mother cell differentiates from nucellar cells and undergoes meiosis to produce megaspores, which develop into the female gametophyte.
- GeneralClass 12All
How is secondary nucleus formed? What is the ploidy of primary endosperm nucleus (PEN)?
Secondary nucleus formation: Fusion of two polar nuclei (each haploid) within the embryo sac produces the diploid (2n) secondary nucleus Primary Endosperm Nucleus (PEN): Forms through triple fusion—one male gamete (n) fuses with the secondary nucleus (2n), resulting in triploid (3n) PEN
- GeneralClass 12All
Discuss the flagellar number and position of insertion in different classes of algae.
Class Flagellar Number Position of Insertion Chlorophyceae (Green algae) 2–8, equal length Apical (at cell apex) Phaeophyceae (B
- GeneralClass 12All
What is alternation of generation?
Alternation of generation describes life cycles where multicellular haploid gametophyte and diploid sporophyte phases alternate regularly. The gametophyte produces gametes via mitosis; gamete fusion forms a zygote that develops into a sporophyte. The sporophyte produces spores via meiosis, which develop into gametophytes, completing the cycle.
- GeneralClass 12All
What is the difference between pollination and syngamy?
Process Definition Nature Pollination Transfer of pollen from anther to stigma Physical transfer of immobile structures Syngamy </td
- GeneralClass 12All
How can we say that embryo sac is haploid?
The embryo sac is demonstrably haploid because: A diploid megaspore mother cell in the nucellus undergoes meiosis This produces four haploid megaspores Three degenerate; one functional megaspore undergoes mitotic divisions This forms the seven-celled, eight-nucleate female gametophyte (embryo sac), all cells being haploid
- GeneralClass 12All
Explain how sexual reproduction occurs in gymnosperms.
Gymnosperm sexual reproduction involves: Pollination: Wind-dispersed pollen grains reach the ovule's micropyle Pollen tube formation: The pollen grain germinates, forming a tube that grows through nucellus tissue Fertilization: The pollen tube delivers male gametes to archegonia within the megagametophyte Syngamy: Male gamete fuses with egg cell, forming a diploid zygote</s
- GeneralClass 12All
Mention the "division" of plant group that is known as non-vascular amphibians of the plant kingdom. Why are they called so?
Bryophytes are termed the "amphibians of the plant kingdom" because: Lack of vascular tissue (xylem and phloem) limits their size and distribution Dependence on water for sexual reproduction—flagellated sperm require external moisture to swim to the egg Terrestrial habitat with aquatic reproduction, paralleling amphibian life history
- GeneralClass 12All
Explain how mosses reproduce sexually.
Sexual reproduction in mosses follows this sequence: Antheridia release biflagellated antherozoids into water Antherozoids swim chemotactically toward archegonia Fertilization occurs when an antherozoid fuses with the egg cell The resulting zygote develops into a multicellular sporophyte consisting of: Foot (absorbs nutr
- GeneralClass 12All
Explain how liverworts reproduce asexually.
Liverworts employ two primary asexual reproductive mechanisms: Fragmentation: The thallus breaks into fragments; each fragment regenerates into a complete individual through mitotic cell division Gemma formation: Specialized multicellular propagules develop in gemma cups, detach, and germinate into new gametophytes under favorable conditions
- GeneralClass 12All
Define numerical taxonomy.
Numerical taxonomy (phenetic classification) employs quantitative methods to classify organisms based on numerous observable characteristics. Each character receives equal weight, and similarity is calculated using mathematical algorithms. This computer-based approach can simultaneously analyze hundreds of characters, providing objective, reproducible classifications.
- GeneralClass 12All
How do algae increase the level of dissolved oxygen in their immediate environment?
Algae are primary producers that fix approximately 50% of global carbon dioxide through photosynthesis. During this process, they release molecular oxygen (O₂) as a byproduct, thereby increasing dissolved oxygen concentrations in aquatic ecosystems critical for supporting aerobic life forms.
- GeneralClass 12All
Define isogamous and anisogamous reproduction.
Reproductive Type Definition Gamete Characteristics Isogamous Fusion of morphologically identical gametes Similar size, may be flagellated or non-flagellated <td width="124
- GeneralClass 12All
What is the ploidy of a male gamete present in the pollen grain?
The male gamete within a pollen grain is haploid (n), resulting from mitotic division of the generative cell within the microgametophyte.