Plant Reproduction

11. In flowering plants, DNA content of the parent plant gets halved

In flowering plants, DNA content of the parent plant gets halved during

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Seed germination
Fruit formation
Flower bud formation
Pollen formation
This question was previously asked in
UPSC NDA-2 – 2023
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In flowering plants, DNA content gets halved during meiosis. Meiosis is a type of cell division that produces gametes (sex cells) with half the number of chromosomes (and thus half the DNA content) of the parent cell. In flowering plants, pollen grains contain the male gametes (sperm), and their formation (microsporogenesis) involves meiosis. Similarly, the formation of the female gametophyte and egg cell (megasporogenesis) also involves meiosis, halving the DNA content. Seed germination, fruit formation, and flower bud formation involve mitotic division and growth, not the halving of DNA content for gamete production.
Meiosis reduces the chromosome number (and DNA content) by half to produce gametes. Pollen formation involves meiosis.
Fertilization, the fusion of male and female gametes, restores the diploid number of chromosomes (and doubles the DNA content compared to the gametes) in the zygote, which then develops into the embryo.

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12. Relationship between a flower and honey-bee will help the flower

Relationship between a flower and honey-bee will help the flower for/in

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Faster development
Pollination
Quick germination of pollen
Increase in size
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UPSC NDA-2 – 2023
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Honey-bees are common pollinators. When a honey-bee visits a flower to collect nectar or pollen, it inadvertently picks up pollen grains on its body. As it visits other flowers of the same species, it transfers pollen to the stigma, facilitating pollination. Pollination is the transfer of pollen from the anther to the stigma, a necessary step for fertilization and subsequent seed and fruit development in many flowering plants.
The relationship between flowering plants and pollinators like honey-bees is a classic example of mutualism, where the flower benefits from pollination (leading to reproduction), and the bee benefits from food resources (nectar and pollen).
While successful pollination leads to seed/fruit development which is part of the plant’s life cycle, the direct benefit to the flower from the bee’s visit is the act of pollination itself. The bee’s visit does not directly cause faster flower development, quicker pollen germination (which happens after pollination on the stigma under favorable conditions), or increase in flower size.

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13. In angiosperms, pollen grain germinates to produce two male gametes. W

In angiosperms, pollen grain germinates to produce two male gametes. Which one of the following functions is carried out by these gametes ?

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Both the gametes fuse with a single egg cell
Both the gametes fuse with two different egg cells
One gamete fuses with the egg cell and the other one eventually degenerate
One gamete fuses with the egg cell and the other one fuses with a diploid secondary nucleus
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UPSC NDA-2 – 2023
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In angiosperms, the pollen grain contains two male gametes. During double fertilization, one male gamete fuses with the egg cell to form the diploid zygote, which develops into the embryo. The other male gamete fuses with the diploid secondary nucleus (formed by the fusion of two polar nuclei) within the embryo sac to form the triploid primary endosperm nucleus (PEN), which develops into the nutritive tissue called endosperm. This process of fertilization of both the egg cell and the secondary nucleus is unique to angiosperms.
Double fertilization is a characteristic feature of angiosperms, involving two male gametes: one fertilizes the egg (forming the zygote), and the other fertilizes the secondary nucleus (forming the endosperm).
The pollen tube grows down the style and enters the ovule, releasing the two male gametes into the embryo sac. This ensures efficient delivery and participation of both gametes in the fertilization process.

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14. After fertilization, the fruit and the seed are produced by

After fertilization, the fruit and the seed are produced by

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ovule and ovary, respectively
ovary and ovule, respectively
ovary, no ovule required
ovule, no ovary required
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UPSC NDA-2 – 2022
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The correct answer is B) ovary and ovule, respectively.
After fertilization in flowering plants, the ovary, which contains the ovules, develops and matures into the fruit. Simultaneously, the ovules inside the ovary develop and mature into seeds. Therefore, the fruit is produced by the ovary, and the seed is produced by the ovule.
The process of fertilization is the fusion of the male gamete (from the pollen) with the female gamete (egg cell) inside the ovule. This triggers the development of the embryo within the ovule and the maturation of the ovule into a seed and the ovary into a fruit. The fruit serves to protect the seed and aid in its dispersal.

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15. If one set of chromosomes for a given plant is represented as N; in ca

If one set of chromosomes for a given plant is represented as N; in case of double fertilization, the zygote and the endosperm nucleus of a diploid plant would have how many sets of chromosomes respectively?

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N and 2N
2N and 2N
N and 3N
2N and 3N
This question was previously asked in
UPSC NDA-2 – 2018
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In double fertilization in a diploid plant (where N represents the haploid set of chromosomes), the zygote is formed by the fusion of a haploid male gamete (N) and a haploid egg cell (N), resulting in a diploid zygote (2N). The endosperm nucleus is typically formed by the fusion of a haploid male gamete (N) with the diploid central cell (usually containing two haploid polar nuclei, N+N=2N), resulting in a triploid primary endosperm nucleus (N + 2N = 3N).
– Double fertilization is a unique process in flowering plants involving two sperm cells.
– One sperm cell fertilizes the egg to form the diploid zygote (embryo).
– The other sperm cell fertilizes the central cell of the embryo sac to form the primary endosperm nucleus.
– In most diploid angiosperms, the central cell contains two polar nuclei, both usually haploid (N). Their fusion with a haploid sperm (N) results in a triploid (3N) endosperm.
The zygote develops into the embryo. The primary endosperm nucleus develops into the endosperm, which serves as nutritive tissue for the developing embryo. The ploidy level of the central cell can vary in some species, potentially leading to different ploidy levels for the endosperm.

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16. Which one of the following plants has unisexual flowers?

Which one of the following plants has unisexual flowers?

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Papaya
Hibiscus
Mustard
Sunflower
This question was previously asked in
UPSC NDA-1 – 2022
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The correct option is A.
Unisexual flowers contain either male reproductive organs (stamens) or female reproductive organs (pistil/carpel), but not both.
Plants with unisexual flowers can be monoecious (male and female flowers on the same plant, e.g., maize, cucumber) or dioecious (male and female flowers on separate plants, e.g., papaya, date palm). Papaya is a dioecious plant, having separate male and female trees with unisexual flowers. Hibiscus, Mustard, and Sunflower typically have bisexual flowers, containing both stamens and pistil/carpel within the same flower.

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17. In a typical flower, germinating pollen grains pass through several pa

In a typical flower, germinating pollen grains pass through several parts of the gynoecium before they reach the ovule. A list of the parts of gynoecium is given below in different combinations. Choose the combination that represents the correct sequence of pollen tube pathway/journey :

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Style, Stigma, Ovary
Stigma, Style, Ovary
Pistil, Stigma, Ovary
Ovary, Pistil, Style
This question was previously asked in
UPSC NDA-1 – 2021
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The correct answer is (B) Stigma, Style, Ovary.
In the typical process of fertilization in flowering plants, a pollen grain lands on the stigma (the receptive tip of the pistil/gynoecium). If compatible, the pollen grain germinates and grows a pollen tube. This pollen tube grows down through the style (the stalk connecting the stigma to the ovary) and eventually reaches the ovary, where it enters an ovule to deliver the male gametes. Thus, the correct sequence of the pollen tube pathway is Stigma -> Style -> Ovary.
The pistil or carpel is the entire female reproductive part of a flower, typically consisting of the stigma, style, and ovary. Starting the sequence with “Pistil” is not detailing the pathway *through* the parts of the gynoecium.

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18. During seed germination, the part of the embryo which grows into root

During seed germination, the part of the embryo which grows into root is

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Radicle.
Plumule.
Cotyledon.
Epicotyl.
This question was previously asked in
UPSC NDA-1 – 2021
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The correct answer is (A) Radicle.
During seed germination, the embryo within the seed develops into a seedling. The radicle is the embryonic root, which is the first part of the seedling to emerge from the seed during germination. It grows downwards into the soil to anchor the seedling and absorb water and nutrients.
The plumule is the embryonic shoot, which develops upwards into the stem and leaves. Cotyledons are seed leaves that store food or perform photosynthesis temporarily. The epicotyl is the part of the embryonic shoot above the cotyledons.

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19. The colourful part of the Sunflower or Marigold plant is

The colourful part of the Sunflower or Marigold plant is

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Flower
Inflorescence
Fruit
Seed
This question was previously asked in
UPSC NDA-1 – 2017
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The colourful part of the Sunflower or Marigold plant is an inflorescence.
Plants like Sunflower (Helianthus annuus) and Marigold (Tagetes spp.) belong to the family Asteraceae (also known as Compositae). Their characteristic flower structure is a capitulum or head, which is a type of inflorescence. What appears to be a single flower is actually a composite structure made up of many smaller individual flowers called florets. The outer, colourful “petals” are typically ray florets, while the central part consists of numerous disc florets.
A single flower is a reproductive structure. An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or complicated arrangement of branches. Fruits develop from flowers (or inflorescences in some cases), and seeds are contained within the fruit, developing from ovules.

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20. The seeds of flowering plants are made up of

The seeds of flowering plants are made up of

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Ovary and ovary wall
Embryo, food reserves and coat
Cotyledons
Zygotes
This question was previously asked in
UPSC NDA-1 – 2015
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A seed is a fundamental part of the reproduction process in flowering plants. It develops from the ovule after fertilization. A typical seed is composed of three main parts: the embryo (developed from the zygote), stored food reserves (often in the form of endosperm or cotyledons), and a protective seed coat (developed from the integuments of the ovule).
A seed is the structure containing the embryonic plant, along with food, enclosed in a protective outer covering.
The embryo consists of the radicle (embryonic root), plumule (embryonic shoot), and one or two cotyledons (seed leaves). The stored food provides nourishment for the embryo during germination before it can photosynthesize.

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