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Q11(f):
Identify each part in a flowering plant and write whether it is haploid (\(n\)) or diploid (\(2n\)).
(f) Zygote ———————————
Solution :
Biological Setup & Target Identification
In the study of sexual reproduction in flowering plants (angiosperms), the ploidy level refers to the number of sets of chromosomes present in the nucleus of a cell. The ploidy is generally denoted by the variable $n$, where $n$ represents a single set of chromosomes (haploid state).
We are tasked with identifying the ploidy level of a Zygote in a flowering plant.
Step 1: Analyzing the Origin of the Zygote
In angiosperms, reproduction involves a process called double fertilization. This process consists of two distinct fusion events occurring within the embryo sac of the ovule:
- Syngamy (True Fertilization): The fusion of one male gamete with the female gamete (egg cell) to form a zygote.
- Triple Fusion: The fusion of the second male gamete with two polar nuclei to form the primary endosperm nucleus (PEN).
The zygote is the direct product of syngamy [Per the fundamental principles of sexual reproduction].
Step 2: Determining the Ploidy of the Fusing Gametes
Gametes in all sexually reproducing organisms are produced via meiosis (reduction division) or are derived directly from a haploid gametophyte structure (as seen in plants via mitosis of haploid spores). Therefore, both the male and female gametes contain only one complete set of chromosomes.
- Ploidy of the Male Gamete (Sperm cell) = Haploid ($n$)
- Ploidy of the Female Gamete (Egg cell) = Haploid ($n$)
Step 3: Mathematical Derivation of the Zygote's Ploidy
When syngamy occurs, the genetic material of the two haploid gametes combines. The total chromosomal complement of the resulting zygote is the sum of the chromosomal complements of the fusing gametes.
$$\text{Ploidy of Zygote} = \text{Ploidy of Male Gamete} + \text{Ploidy of Female Gamete}$$ $$\text{Ploidy of Zygote} = n + n$$ $$\text{Ploidy of Zygote} = 2n$$
Thus, the zygote possesses two complete sets of chromosomes, making it diploid. This diploid zygote will subsequently undergo continuous mitotic divisions to develop into a diploid embryo, which represents the beginning of the sporophytic generation.
Visualizing the Fertilization Process
The following diagram illustrates the precise fusion of haploid cells to form a diploid zygote, preserving the conservation of chromosomal sets.
Summary Table of Reproductive Structures
| Plant Part | Origin / Mechanism of Formation | Ploidy Level |
|---|---|---|
| Male Gamete | Mitosis of generative cell inside the pollen grain | Haploid ($n$) |
| Egg Cell | Mitosis of the functional megaspore | Haploid ($n$) |
| Zygote | Fusion of male gamete and egg cell (Syngamy) | Diploid ($2n$) |
Final Solution: The zygote in a flowering plant 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(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 ———————————
- 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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