NEET Previous Year Questions (2016-2024): Sexual Reproduction in Flowering Plants | Biology Class 12 PDF Download

Ans: (d)
To determine the correct set of statements, we need to analyze each statement individually based on the characteristics of water-pollinated plants and specific examples given:

Statement A: "The flowers of Vallisneria are colourful and produce nectar."
This statement is incorrect. Vallisneria is an example of a water-pollinated (hydrophilous) plant. Unlike insect-pollinated flowers, which are often colorful and produce nectar to attract pollinators, water-pollinated flowers typically lack bright colors and nectar because they do not need to attract insects or other animals. Vallisneria flowers are small and inconspicuous.

Statement B: "The flowers of water lily are not pollinated by water."
This statement is correct. Water lilies are typically pollinated by insects, not by water. The large and colorful flowers of water lilies are adapted to attract insect pollinators, contrasting starkly with the typical features of water-pollinated flowers.

Statement C: "In most of water-pollinated species, the pollen grains are protected from wetting."
This statement is correct. In water-pollinated plants, the pollen grains often have a covering or are structured in a way that prevents them from becoming waterlogged and sinking. This adaptation allows them to float on the water's surface and reach the female parts of other plants.

Statement D: "Pollen grains of some hydrophytes are long and ribbon like."
This statement is correct. In some water-pollinated plants, such as seagrasses (e.g., Zostera), the pollen grains are indeed elongated and ribbon-like, which helps them to be transported more effectively by water currents.

Statement E: "In some hydrophytes, the pollen grains are carried passively inside water."
This statement is also correct. Many hydrophytes have pollen grains that are transported by water currents, rather than being actively carried by animal pollinators or the wind. This passive transport is typical in water-pollinated species.

Based on the analysis, Statements B, C, D, and E are correct, while Statement A is incorrect.
Therefore, the correct answer is: Option D: B, C, D, and E only

Ans: (a)
The given diagram shows a wind pollinated plant showing compact inflorescence and well exposed stamens.
Stamens are exposed so complete autogamy does not occur.

Ans: (a)
Large, colorful, fragrant flowers with nectar are features that attract biotic pollinators. Insect pollinated plants, also known as entomophilous plants, often have these characteristics to attract insects such as bees, butterflies, and moths, which play a significant role in their pollination process.

Ans: (c)
Synergids are the cells of gametophyte and hence these are haploid Zygote is formed by fusion of two gametes and thus it is diploid.
Primary endosperm nucleus is formed by the fusion of diploid secondary nucleus with a male gamete. Therefore, it is triploid.

Ans: (b)
The correct answer is Option B : A is true but R is false.
Assertion A is true. In gymnosperms, the pollen grains are indeed released from the microsporangium and are typically carried by air currents, a method of pollination known as anemophily.
Reason R is false. Although it's true that air currents carry the pollen grains, the pollen grains do not directly reach the mouth of the archegonia in gymnosperms. Instead, they land on the ovule, where they germinate and form a pollen tube that delivers the male gametes to the egg. Therefore, a pollen tube is formed in gymnosperms, contrary to what Reason R suggests.

Ans: (b)

Among the animals, insects, particularly bees are the dominant biotic pollinating agents.

Ans: (c)

Cleistogamous flowers does not open at all. In such flowers autogamy occurs. Lack of cross pollination is a disadvantage of cleistogamy.

Ans: (d)
Mostly nucellus is consumed after fertilisation due to absorption of food by developing embryo in a seed. Sometimes, the nucellus remains persistent in the seed and is called perisperm.

Ans: (c)
(b) There is no need to emasculate unisexual flowers of the selected female parent - This statement is correct because unisexual flowers do not have male reproductive parts (stamens), so there is no need to remove anthers (emasculate) to prevent self-pollination.
(c) Emasculated flowers are to be bagged immediately after cross-pollination - This statement is correct because, after cross-pollination with the desired pollen, the flowers need to be bagged to prevent further contamination from unwanted pollen or other pollinating agents.
(d) Emasculated flowers are to be bagged after removal of anthers - This statement is correct. The emasculated flowers should be bagged after anther removal and before cross-pollination. This prevents contamination with unwanted pollen. After cross-pollination, the flowers should be bagged again to avoid any further contamination.

The other options are incorrect :
(a) The female flower buds of plant producing unisexual flowers need not be bagged - This statement is incorrect because even unisexual flowers need to be bagged to prevent contamination from unwanted pollen or other pollinating agents.
(e) Bisexual flowers, showing protogyny, are never selected for cross - This statement is incorrect because protogyny (when the female reproductive part matures before the male reproductive part) can reduce the chances of self-pollination, making these flowers suitable for cross-pollination.

Ans: (c)

Xenogamy refers to the transfer to pollen grains from anthers of one plant to stigma of a different plant which during pollination, brings genetically different types of pollen grains to stigma.

Cleistogamy is a condition in which flower does not open.

Geitonogamy refers to the transfer of pollen grain from anther to stigma of another flower of the same plant.

Chasmogamy is a condition in which flowers remain open.

Ans: (c)

A typical angiospermic embryo sac has seven cells that are three antipodals, one central cell, one egg cell and two synergids.

The central cell has two polar nuclei, hence the embryo sac is eight nucleated.

Ans: (b)

In some members of Rosaceae, Leguminosae and Solanaceae pollen grains maintain viability for a month due to sporopollenin.

The outer wall or exine of pollen grains contains sporopollenin. It is one of the most resistant organic compounds known. It protects pollen grains from external factors such as temperature, acid, alkali, etc. because of sporopollenin, pollen grains are preserved as fossils.

Ans: (d)
Diadelphous condition is a condition of arrangement of filaments and stamen in a flower, e.g. Pea. In this condition, filaments of nine different stamens are connected into one unit and the tenth posterior stamen remains out of the bundle as a stand part. The androecium of pea flower is diadelphous because the filaments of the anther are united in two bundles. In the case of pea, out of ten, nine stamens form a staminal tube while one is free. Thus, the correct answer is 'Pea' which exhibit diadelphous condition

China rose has monoadelphous stamens while, Citrus has polyadelhphous stamens. Monoadelphous stamens are grouped in single bundle whereas polyadelphous stamens occur in more than two bundles.

Ans: (b)
The attachment point of funicle and body of ovule is known as hilum. A hilum is a scar or mark left on a seed coat by the former attachment to the ovary wall or to the funiculus (which in turn attaches to the ovary wall). A hilum can also be a nucleus of a starch grain; the point around which layers of starch are deposited.

Ans: (b)
The plant parts which consist of two generations one within the other are pollen grains inside the anther and embryo sac inside the ovule. Pollen grain is haploid inside the diploid anther. Embryo sac is haploid inside the diploid ovule.

Ans: (c)
In some seeds, remains of nucellus persist.
This residual nucellus which persists in the seed is called perisperm
Examples: Black pepper, coffee, castor, cardamom, Nymphaea.

Ans: (a)

In flowering plants,

Out of the two male gametes, one gametes fuses with the nucleus of the nucleus of the egg cell and forms the zygote. The process is known as syngamy.

The other male gamete fuses with the two polar nuclei located in the central cell to form a triploid primary endosperm nucleus (PEN). Since, the process involves the fusion of three haploid nuclei, it is known as triple fusion.

Since two kinds of fusions (syngamy and triple fusion) take place in an embryo sac it is known as double fertilisation

Ans: (a)

Central cell develops into Endopserm. Endosperm developes from the fusion of secondary diploid nucleus with one male nucleus formina primary endopsermm nucleus (PEN).

Ans: (c)
Parthenogenesis is the process, whereby the female gamete develops into new organism without fertilisation. Seedless fruits are formed by parthenogenesis.

Ans: (d)
The pinus seeds have a very hard seed coat so without fungal association the seed cannot absorb water. The mycorrhizae penetrate deep inside the seeds to moisten them.

Ans: (a)
In parietal placentation the ovules develop on the inner wall of ovary or in peripheral part. E.g. Mustard, Argemone, etc.

Ans: (d)

Sporopollenin cannot be degraded by enzyme; strong acids and alkali, therefore it is helpful in preserving pollen as fossil.

Ans: (d)

Winged pollen grains are present in Pinus. Each pollen grain has two wing-like structures which enables it to float in air, as an adaptation for dispersal by the wind.

Ans: (b)
In angiosperms, the functional megaspore is the first cell of female gametophyte. It enlarges and undergoes three nuclear mitotic divisions to form embryo sac.

Ans: (a)

Insect pollinated plants provide rewards as edible pollen grain and nectar as usual rewards. In order to materialize and maximize pollination flowers have developed a set of attributes which are aimed at attracting the pollinators called attractants.

Ans: (b)
Wind pollination or anemophily occurs in flowers which are having a single ovule in each ovary, and numerous flowers packed in an inflorescence. It is a non-directional pollination.

Ans: (a)
Autogamy occurs in bisexual flowers. Geitonogamous flowers are unisexual but present in the same plant. Dioecious condition is observed when unisexual male and female flowers are present on different plants and it prevents both autogamy and geitonogamy.

Ans: (c)
Double fertilisation is the characteristic feature of angiosperms. Here, two male gametes are released in the embryo sac or female gametophyte. One male gamete fuses with the egg cell to form zygote that gives rise to embryo whereas the other male gamete fuses with the secondary nucleus to form primary endosperm nucleus (PEN) that gives rise to endosperm.

Ans: (c)

• Megaspore mother cell of megasporangium undergoes meiosis and forms megaspore tetrad, out of which, one megaspore is functional. 
• Central cell of embryo sac is the large cell consisting of two polar nuclei. 
• Synergids, the flanking cells of the egg cell, have finger-like projections of the wall in their cytoplasm, the filiform apparatus.
• An embryo sac has three antipodal cells which provide nutrition to developing the embryo.

Ans: (b)

• Water lily has actinomorphic flowers and produce large number of stamen to favour anemophily (wind pollination). 
• Water hyacinth exhibit entomophily and is pollinated by insects that feed on its foliage.

Ans: (a)

• The archesporial cells (2n) of young ovule cut off the parietal cell and are differentiated into megaspore mother cells (2n). 
• The diploid megaspore mother cells then undergo meiosis to form a linear tetrad of megaspores. 
• Megaspore is the first cell of the female gametophyte. 
• Out of four, the functional megaspore undergoes megagametogenesis to 8-nucleate and 7-celled embryo sac. 
• Ovule serves as megasporangium wherein megaspores production occurs.

Ans: (b)
The coconut water from tender coconut represents the free nuclear or liquid endosperm. During the development of nuclear type of endosperm, the primary endosperm mother cell divides by free nuclear divisions, and these divisions are not followed by cell wall formation. Thus, the free nuclei remain in the cytoplasm of the embryo sac.

Ans: (c)

Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat.

Ans: (b)
Apomixis is a reproductive process which does not involve gametic fusion. In apomictic flowering plants there is no fertilisation and embryos develop simply by division of a cell of ovule.

Ans: (c)

Pollen-pistil interaction is the group of events that occur from the time of pollen deposition over the stigma to the time of pollen tube entry into ovule. It is a safety measure to ensure that illegitimate crossing does not occur. Pollen grains of number of plants may settle over a stigma. The pollens belonging to same species would germinate while other fail to do so but the pollen tube of the compatible pollen will grow through the style to reach the ovule whereas growth of incompatible pollens will be arrested at stigmatic disc or sometimes in the beginning part of style.

Ans: (b)

The proximal end is attached to the thalamus whereas the distal end bears anther.