Botany 2024 Paper I 50 marks 150 words Compulsory Explain

Q5

Answer the following questions in about 150 words each: (a) What are the consequences of domestication of plants? Explain. 10 (b) Describe how successive cambia cause thickening of the stem in some flowering plants. Name any two families that display this phenomenon. 8+2=10 (c) Distinguish various types of agamospermy. Why is apomixis now regarded a tool of practical importance? 8+2=10 (d) Write the botanical names, family and parts used of any five fibre-yielding plants. 10 (e) Differentiate between zygotic and somatic embryos. 10

हिंदी में प्रश्न पढ़ें

निम्नलिखित प्रत्येक प्रश्न का उत्तर लगभग 150 शब्दों में दीजिए : (a) पौधों को घरेलु (खेती-बाड़ी) बनाने के क्या परिणाम रहे हैं? व्याख्या कीजिए। 10 (b) वर्णन कीजिए कि किस प्रकार क्रमिक कैम्बिया कुछ फूल वाले पौधों में तने के मोटे होने का कारण बनते हैं। किन्हीं दो कुल के नाम बताइए जो इस संवृत्ति को दर्शाते हैं। 8+2=10 (c) विभिन्न प्रकार की अनिषेकबीजता में अंतर कीजिए। असंगजन (एपोमिक्सिस) को अब व्यावहारिक महत्व का साधन क्यों माना गया है? 8+2=10 (d) किन्हीं पाँच रेशे देने वाले पादपों के वानस्पतिक नाम, कुल का नाम और प्रयुक्त भागों को बताइए। 10 (e) युग्मज और दैहिक भ्रूण के बीच अंतर को स्पष्ट कीजिए। 10

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Directive word: Explain

This question asks you to explain. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

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How this answer will be evaluated

Approach

This multi-part question requires explaining consequences (part a), describing successive cambia mechanism (part b), distinguishing agamospermy types and justifying apomixis importance (part c), enumerating fibre plants with nomenclature (part d), and differentiating embryo types (part e). Allocate approximately 30 words each to parts (a), (b), (c) and (e) (10 marks each), and 30 words to part (d). Structure each sub-part as a concise paragraph with definition → mechanism/process → specific examples → significance/application where applicable. No introduction or conclusion needed across parts; treat as five independent short answers.

Key points expected

  • Part (a): Genetic erosion and loss of allelic diversity; morphological changes (seed size, loss of shattering, synchronous ripening); physiological alterations (reduced dormancy, photoperiod insensitivity); reduced fitness in wild conditions; Indian examples like rice (Oryza sativa) from O. rufipogon or wheat domestication in Fertile Crescent/Mehrgarh context
  • Part (b): Formation of successive cambia from pericycle or parenchyma; development of concentric rings of vascular bundles; secondary xylem and phloem produced by each cambium; families: Chenopodiaceae (Beta vulgaris) and Amaranthaceae (Achyranthes/Amaranthus) or Nyctaginaceae (Boerhaavia)
  • Part (c): Adventitious embryony (Sporophytic apomixis: nucellar/polyembryony), Gametophytic apomixis (apospory, diplospory), Recurrent vs non-recurrent types; practical importance: fixation of heterosis, clonal seed production, hybrid development (apomictic breeding in Citrus, mango, guava), bypass of incompatibility barriers
  • Part (d): Five fibre plants with correct binomials, families and plant parts: e.g., Gossypium arboreum/herbaceum/hirsutum (Malvaceae, seed hairs/lint); Corchorus capsularis/olitorius (Malvaceae, phloem fibre); Linum usitatissimum (Linaceae, stem bast); Crotalaria juncea (Fabaceae, stem bast); Agave sisalana (Asparagaceae, leaf fibre)
  • Part (e): Zygotic embryo: sexual origin, zygote formation, endosperm typically triploid, genetic variation, suspensor present; Somatic embryo: asexual origin from somatic cells (callus/nucellus), no endosperm formation, genetically uniform, no suspensor or reduced, direct embryogenesis from explants

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness20%10Accurately defines domestication syndrome traits, correctly identifies successive cambia as de novo cambium formation (not normal secondary growth), precisely classifies agamospermy types with correct ploidy relationships, and accurately distinguishes zygotic vs somatic embryo origins without conflating termsBasic definitions correct but minor errors in cambium origin (confusing with normal vascular cambium), incomplete agamospermy classification, or vague distinction between embryo types lacking specific developmental criteriaFundamental misconceptions such as treating domestication as only cultivation, confusing successive cambia with storied cambium, misclassifying apomixis types, or equating somatic embryos with zygotic embryos without basis
Diagram / labelling15%7.5Clear labeled diagram for part (b) showing concentric vascular rings, successive cambia positions, and secondary growth pattern; or for part (e) showing structural differences between zygotic and somatic embryos with suspensor and developmental stages indicatedSimple diagram present but incomplete labeling, missing key structures like cambium rings or embryo suspensor, or diagram only for one part when applicable to multipleNo diagram despite clear requirement in part (b), or diagram completely unlabeled/irrelevant to the structures described
Examples & nomenclature25%12.5Correct binomial nomenclature throughout: five fibre plants with accurate botanical names, families, and plant parts (e.g., Gossypium spp. with Malvaceae, seed coat fibres); Indian/domestication context for (a) (Mehrgarh, Vavilov centers); correct families for successive cambia (Chenopodiaceae, Amaranthaceae/Nyctaginaceae); specific crop examples for apomixis (Citrus, mango)Most names correct but minor errors in family placement (e.g., Tiliaceae instead of Malvaceae for Corchorus), generic references without species, or missing one plant part in fibre enumerationMultiple nomenclature errors, incorrect families, confused common and scientific names, or complete absence of specific examples for domestication consequences or apomixis applications
Process explanation20%10Clear mechanistic explanation: for (a) sequential genetic and phenotypic changes under selection; for (b) stepwise cambium initiation from pericycle and vascular tissue formation; for (c) precise developmental pathways of each agamospermy type; for (e) contrasting developmental origins and nutrient acquisitionDescribes processes in general terms without clear sequence, missing key steps like pericycle origin of successive cambia, or conflating developmental pathways of different agamospermy typesDescriptive without mechanistic explanation, no clear process flow, or completely incorrect developmental sequence (e.g., stating successive cambia form from cork cambium)
Application / ecology20%10Explicitly links domestication to genetic vulnerability and conservation needs; connects successive cambia to ecological adaptation in arid/semi-arid plants; emphasizes apomixis as breeding tool for hybrid seed production and intellectual property protection; notes economic importance of fibre plants in Indian agriculture (jute, cotton)Mentions practical importance superficially without specific breeding applications, or notes ecological context without linking to mechanism, or lists fibre uses without economic significanceNo application or ecological context provided, treats all parts as purely academic descriptions without real-world relevance, or completely misses the 'practical importance' requirement in part (c)

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