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Q11(a):
Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)).
(a) Ovary ———————————
Solution :
Step 1: Anatomical Identification & Context
In the morphology of flowering plants (angiosperms), the flower is a highly specialized reproductive shoot. The female reproductive organ is known as the pistil or carpel. The carpel is differentiated into three primary distinct regions:
- Stigma: The apical receptive surface where pollen grains land.
- Style: The elongated tubular stalk connecting the stigma to the base.
- Ovary: The swollen, basal portion of the carpel that houses one or more ovules (integumented megasporangia).
Step 2: Theoretical Framework of Alternation of Generations
To determine the ploidy level—whether a structure is haploid ($n$) or diploid ($2n$)—we must analyze its developmental origin within the plant's life cycle [Per the botanical principle of Alternation of Generations].
In angiosperms, the dominant, independent, and photosynthetic phase of the life cycle is the sporophyte generation. The entire physical plant body—including roots, stems, leaves, and all floral appendages (sepals, petals, stamens, and carpels)—is comprised of somatic cells belonging to the sporophyte generation. Because the sporophyte develops from a diploid zygote via somatic mitosis, every vegetative and structural cell of the sporophyte is strictly diploid ($2n$).
Step 3: Cytological Deduction of the Ovary
The ovary is a structural, maternal tissue forming the protective wall of the megasporangium (ovule). It is not a gamete, nor is it formed through meiosis. Instead, meiosis occurs inside the ovule (within the ovary) to produce a haploid megaspore, which then develops into the haploid female gametophyte (the embryo sac).
Since the ovary tissue is a direct extension of the parent plant's sporophytic body, its constituent cells carry two sets of chromosomes, one inherited from each parent of the given plant.
Visual Analysis: Structural Ploidy of the Carpel
The following structural diagram illustrates the cross-section of a carpel, distinguishing the diploid maternal tissues from the site of haploid generation.
Step 4: Final Verification
Let us rigorously verify the cellular constitution. During microsporogenesis and megasporogenesis, the parent cells known as Spore Mother Cells (SMCs) are diploid ($2n$). The ovary contains the megasporangium which houses the Megaspore Mother Cell (MMC). Because the ovary wall envelops and protects the MMC prior to meiosis, the ovary itself has not undergone any reductional division. Therefore, its chromosomal complement remains exactly identical to the somatic cells of the vegetative root, shoot, and leaf systems.
Final Solution: The ovary is diploid ($2n$).
More Questions from Class 12 Biology Reproduction in Organisms EXERCISES
- Q1: Why is reproduction essential for organisms?
- Q1: Why is reproduction essential for organisms?
- Q2: Which is a better mode of reproduction: sexual or asexual? Why?
- Q2: Which is a better mode of reproduction: sexual or asexual? Why?
- Q3: Why is the offspring formed by asexual reproduction referred to as clone?
- Q3: Why is the offspring formed by asexual reproduction referred to as clone?
- Q4: Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
- Q4: Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
- Q5: How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
- Q5: How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
- Q6: Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
- Q6: Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
- Q7: What is vegetative propagation? Give two suitable examples.
- Q7: What is vegetative propagation? Give two suitable examples.
- Q8(a): Define (a) Juvenile phase,
- Q8(a): Define (a) Juvenile phase,
- Q8(b): Define (b) Reproductive phase,
- Q8(b): Define (b) Reproductive phase,
- Q8(c): Define (c) Senescent phase.
- Q8(c): Define (c) Senescent phase.
- Q9: Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
- Q9: Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
- Q10: Explain why meiosis and gametogenesis are always interlinked?
- Q10: Explain why meiosis and gametogenesis are always interlinked?
- Q11(a): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (a) Ovary ———————————
- Q11(b): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (b) Anther ———————————
- Q11(b): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (b) Anther ———————————
- Q11(c): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (c) Egg ———————————
- Q11(c): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (c) Egg ———————————
- Q11(d): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (d) Pollen ———————————
- Q11(d): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (d) Pollen ———————————
- Q11(e): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (e) Male gamete ———————————
- Q11(e): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (e) Male gamete ———————————
- Q11(f): Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)). (f) Zygote ———————————
- Q11(f): Identify each part in a flowering plant and write whether it is haploid ((n)) or diploid ((2n)). (f ) Zygote ———————————
- Q12: Define external fertilisation. Mention its disadvantages.
- Q12: Define external fertilisation. Mention its disadvantages.
- Q13: Differentiate between a zoospore and a zygote.
- Q13: Differentiate between a zoospore and a zygote.
- Q14: Differentiate between gametogenesis from embryogenesis.
- Q14: Differentiate between gametogenesis from embryogenesis.
- Q15: Describe the post-fertilisation changes in a flower.
- Q15: Describe the post-fertilisation changes in a flower.
- Q16: What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
- Q16: What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
- Q17: Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
- Q17: Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
- Q18: Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
- Q18: Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
CBSE Solutions for Class 12 Biology Reproduction in Organisms
Chapters in CBSE - Class 12 Biology
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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