General Q&A for Class 12 · Page 251
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Which parts in ginger and potato are edible?
Ginger: The edible part is the rhizome, a modified underground stem that grows horizontally and stores food. Potato: The edible portion is a tuber, another modified underground stem characterized by swollen nodes called "eyes" (axillary buds). Key Point: Both are stems, not roots, as evidenced by the presence of nodes, internodes, and axillary buds.
- GeneralClass 12All
Describe the type of fertilization that is unique to plants in which seeds are enclosed by fruits.
Double fertilization (unique to angiosperms): Syngamy: Male gamete + Egg → Zygote (2n) → Embryo Triple fusion: Male gamete + Secondary nucleus (2n) → PEN (3n) → Endosperm
- GeneralClass 12All
Represent schematically the haplo-diplontic life cycle.
Sporophyte (2n) → Meiosis → Spores (n) → Gametophyte (n) → Gametes (n) → Syngamy → Zygote (2n) → Sporophyte (2n) Both phases are multicellular and often free-living
- GeneralClass 12All
What are the two classes of angiosperms? Give an example for each.
Class Cotyledon Number Example Dicotyledons Two Pisum sativum (Pea) Monocotyledons One
- GeneralClass 12All
Mention three economic importance of the first terrestrial plants having vascular tissues.
Soil binding: Prevents erosion on slopes Medicinal value: Dryopteris provides anthelmintic drugs Ornamental use: Ferns cultivated for decorative foliage
- GeneralClass 12All
Write the names of any three classes of pteridophytes. Give one example for each.
Class Example Psilopsida Psilotum Lycopsida Lycopodium Sphenopsida Equ
- GeneralClass 12All
Name the three classes of algae and mention the pigments present in them.
Class Common Name Pigments Chlorophyceae Green algae Chlorophyll a, b Phaeophyceae Brown algae <
- GeneralClass 12All
What is the ploidy of endosperm in flowering plants and how is it formed? Ploidy: Triploid (3n)
Formation: Triple fusion—one haploid male gamete fuses with diploid secondary nucleus (formed from two polar nuclei)
- GeneralClass 12All
Write two examples of green algae that are filamentous. What is the common mode of vegetative reproduction in green algae?
Examples: Ulothrix, Spirogyra Vegetative reproduction: Fragmentation and spore formation (zoospores, aplanospores)
- GeneralClass 12All
Name three algae that show haplodiplontic life cycle. Name one alga that shows diplontic life cycle.
Haplodiplontic: Ectocarpus, Polysiphonia, Kelps Diplontic: Fucus
- GeneralClass 12All
How does asexual reproduction occur in liverworts?
Fragmentation: Thallus fragments regenerate into complete plants Gemma formation: Multicellular propagules in gemma cups detach and grow into new individuals
- GeneralClass 12All
How do the gametophytes of bryophytes differ from those of gymnosperms?
Feature Bryophytes Gymnosperms Independence Free-living, dominant phase Dependent on sporophyte Size Macroscopic <td width=
- GeneralClass 12All
How does isogamous reproduction differ from anisogamous reproduction?
Isogamous: Fusion of morphologically identical gametes (same size, structure) Anisogamous: Fusion of morphologically different gametes (differing sizes) Name the characteristic pigments of brown algae. Chlorophyll a & c, carotenoids, and xanthophylls (especially fucoxanthin)
- GeneralClass 12All
Name the two main parts of a stamen.
Filament (stalk) Anther (pollen-producing structure)
- GeneralClass 12All
Name the structure formed by the germination of a spore of a fern.
Prothallus (heart-shaped gametophyte)
- GeneralClass 12All
What type of sexual reproduction is shown by Volvox?
Oogamous reproduction (fusion of large non-motile egg with small motile sperm)
- GeneralClass 12All
What are gymnosperms?
Gymnosperms are vascular seed plants characterized by naked seeds—ovules and seeds not enclosed within ovary or fruit tissue.
- GeneralClass 12All
What happens to the synergids after fertilization?
Synergids degenerate following fertilization, having fulfilled their role in guiding the pollen tube.
- GeneralClass 12All
Name the characteristic red pigment of red algae.
r-Phycoerythrin (phycobiliprotein)
- GeneralClass 12All
Name the structure that fixes brown algae to the substratum.
Holdfast