31 Years NEET Previous Year Questions: Sexual Reproduction in Flowering Plants - 1


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QUESTION: 1

The term used for transfer of 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, is:    

(2021)

Solution:

The transfer of pollen grains that are shed from the anther to the stigma of a pistil is termed pollination. It is of the following types:
Autogamy: Pollination is achieved within the same flower. Some plants such as Viola, produce two types of flowers. One type of flowers has exposed anthers and stigma and are referred to as chasmogamous flowers. The other type do not open at all and are referred to as cleistogamous flowers.
Geitonogamy: Transfer of pollen grains from the anther to the stigma of another flower of the same plant. Since the pollen grain comes from the same plant, it will be genetically similar to the stigma.
Xenogamy – Transfer of pollen grains from anther to the stigma of a different plant. This is the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma.

Hence, the correct option is C.
NCERT Reference: Page no. 28 of topic “2.2.3 Pollination” of chapter 2.

QUESTION: 2

A typical angiosperm embryo sac at maturity is:    

(2021)

Solution:

There is a characteristic distribution of the cells within the embryo sac. Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled.


 

Image: 8-nucleate 7-celled embryo sac.

Hence, the correct option is C.
NCERT Reference: Page no. 27 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

QUESTION: 3

In some members of which of the following pairs of families, pollen grains retain their viability for months after release?    

(2021)

Solution:

The period for which pollen grains remain viable is highly variable and to some extent depends on the prevailing temperature and humidity.
In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.

Hence, the correct option is B.
NCERT Reference: Page no. 24 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

QUESTION: 4

In water hyacinth and water lily, pollination takes place by:    

(2020)

Solution:

In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. Their stem part which is above the thalamus is not in the water. The pollen grains are in the upper part of thalamus so pollination can't be done by water. That's why it is done by insects and wind.

Hence, the correct option is C.
NCERT Reference: Page no. 29 of topic “Agents of Pollination” of chapter 2.

QUESTION: 5

The plant parts which consists of two generation one within the other:         (2020)
(a) Pollen grains inside the anther
(b) Germinated pollen grain with two male gametes
(c) Seed inside the fruit
(d) Embryo sac inside the ovule

Solution:

Pollen grains inside the anther  - consists of two generations.
Seed inside the fruit - consists of two generation.

Hence, the correct option is C.
NCERT Reference: Page no. 33 of topic “Pollen-pistil Interaction” and page no. 36 of topic “2.4.3 Seed” of chapter 2.

QUESTION: 6

In some plants, the thalamus contributes to fruit formation. Such fruits are termed as:           (2020)

Solution:

In most plants, by the time the fruit develops from the ovary, other floral parts degenerate and fall off. However, in a few species such as apple, strawberry, cashew, etc., the thalamus also contributes to fruit formation. Such fruits are called false fruits

Hence, the correct option is A.

NCERT Reference: Page no. 36 of topic “2.4.3 Seed” of chapter 2.

QUESTION: 7

What type of pollination takes place in Vallisneria?  

 (2019)

Solution:
  • Vallisneria is an aquatic plant. In case of Vallisneria water is the agent for cross pollination. 
  • In female Vallisneria, the flower reaches to the surface of water by the long stalk and the male flower or pollen grains are released into the surface of water. 
  • Female flowers or stigma carried them by water current.
  • Some of them eventually reach the female flowers and the stigma.

​​​​​​​Hence, the correct option is C.
​​​​​​​NCERT Reference: Page no. 29 of topic “Agents of Pollination” of chapter 2.

QUESTION: 8

Persistent nucellus in the seed is known as:    (2019)

Solution:

Nucellus is the mass of parenchymatous cells enclosed within integuments of an ovule. It is the storehouse of abundant food reserves. The residual, persistent nucellus in the seed is called perisperm.
Chalaza is the basal part of the ovule, hilum is the junction between ovule and funicle and tegmen is the inner layer of the seed coat in a dicotyledonous seed.

Hence, the correct option is C.
NCERT Reference: Page no. 36 of topic “2.4.3 Seed” of chapter 2.

QUESTION: 9

Which one of the following, both autogamy and geitonogamy are prevented?    

(2019)

Solution:

Autogamy and geitonogamy are two forms of self-pollination. In autogamy, pollen falls on the stigma of the same flower. While in geitonogamy pollens from a flower fall on the stigma of some other flower on the same plant. Papaya is a dioecious plant thus both autogamy and geitonogamy are prevented in it.

Hence, the correct option is B.
NCERT Reference: Page no. 31 of topic “Outbreeding Devices” of chapter 2

QUESTION: 10

Which of the following has proved helpful in preserving pollen as fossils?    

(2018)

Solution:

Exine of pollen grain is made up of highly resistant fatty substance called sporopollenin, which is not degraded by any enzyme. It is not affected by high temperature, strong acid or strong alkali. Because of the sporopollenin, pollen grains are well preserved as microfossils.

Hence, the correct option is D.
NCERT Reference: Page no. 23 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

QUESTION: 11

Double fertilisation is    

(2018)

Solution:
  • Double fertilisation is a unique and universal feature of angiosperms. Total number of nuclei involved in double fertilisation is five, i.e., 2 in syngamy and 3 in triple fusion. 
  • Syngamy is fusion of one male gamete with egg to form zygote. 
  • Triple fusion occurs when the second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus.

Hence, the correct option is D.
NCERT Reference: Page no. 34 of topic “2.3 DOUBLE FERTILISATION” of chapter 2.

QUESTION: 12

 Which of the following statements is not correct? [2016]

Solution:
  • Pollen grains of different species can land on the stigma, but pistil has an ability to recognise the compatible pollen and accept it for germination on stigma and growth of pollen tube in the style.
  • There occurs a chemical mediated interaction between pollen and pistil, which facilitates the recognition and acceptance of the right type of pollen for further processes and the rejection of the wrong type of pollen grains.

Hence, the correct option is A.
NCERT Reference: Page no. 31 of topic “Pollen-pistil Interaction” of chapter 2.

QUESTION: 13

Which one of the following statements is not true? [2016]

Solution:
  • The tapetum is a specialized layer of nutritive cells found within the sporangium, particularly within the anther, of flowering plants, where it is located between the sporogenous tissue and the anther wall.
  • Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat, however it does not help in dehiscence of the anther.

Hence, the correct option is A.
NCERT Reference: Page no. 21 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

QUESTION: 14

Filiform apparatus is characteristic feature of: [2015 RS]

Solution:

The synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end, consisting of numerous finger-like projections into the synergid cytoplasm. It is believed to play a major role in pollen tube guidance and reception.

Hence, the correct option is C.

NCERT Reference: Page no. 27 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

QUESTION: 15

Which of the following are the important floral rewards to the animal pollinators? [2015 RS]

Solution:

Nectar and pollen grains are the usual floral rewards which the animal pollinators get. 

Additional Information:

  • Flowering plants need to get pollen from one flower to another, either within a plant for self-pollination or between plants of the same species for cross-pollination to occur.
  • However, pollen  can't move on its own, so animals or the wind (and water in rare cases) move the pollen for plants.Many flowers use colours to attract insects, sometimes helped by coloured guiding marks. Some have ultraviolet marks that can be seen by insects but are invisible to human eyes.
  • Flowers are often shaped to provide a landing platform for visiting insects or to force them to brush against anthers and stigmas.
  • Some flowers have a scent to attract insects. Many of these scents are pleasing to humans too, but not all some flowers attract flies with a smell of rotting meat.
  • Colours can't be seen in the dark, so scent is important for flowers that are pollinated by night-flying insects such as moths.
  • Most bird-pollinated flowers have lots of nectar, often at the bottom of a tube of petals.
  • Birds need to brush against anthers and stigmas when reaching for the sugary reward with their long beaks. Some birds, such as stitchbirds and bellbirds, have special brush-like tips to their tongues to help them soak up the nectar.

Hence, the correct option is A.
NCERT Reference: Page no. 30 of topic “Agents of Pollination” of chapter 2.

QUESTION: 16

The hilum is a scar on the: [2015 RS]

Solution:
  • Ovule is an integumented megasporangium found in spermatophytes which develops into seed after fertilization.
  • An angiospermic ovule is typically an ovoid and whitish structure. It occurs inside the ovary where it is attached to a parenchymatous cushion called placenta either singly or in a cluster.
  • The ovule is stalked. The stalk is called funiculus or funicle. The point of attachment of the body of the ovule with the funiculus is known as hilum. It is present as a scar on a mature seed.

Hence, the correct option is D.
NCERT Reference: Page no. 25 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

QUESTION: 17

Which one of the following statements is not true? [2015 RS]

Solution:

Honey is made from nectar and pollens. Bees collect pollen and nectar in the spring when most flowers and plants are in bloom. They collect them in their stomach but for an hour, the nectar mixes with the proteins and enzymes produced by bees, which convert nectar into honey. 

Hence, the correct option is C.
NCERT Reference: Page no. 30 of topic “Agents of Pollination” of chapter 2.

QUESTION: 18

Which one of the following may require pollinators, but is genetically similar to autogamy? [2015 RS]

Solution:
  • Geitonogamy involves transfer of the pollen from one flower of a plant to the stigma of another flower of the same plant.
  • As the pollen has to move from one flower to another flower, it requires a pollinating agent. Yet it is genetically similar to autogamy, as both the flowers of the plant share the same genotype of the plant.
  • Xenogamy is pollination between two flowers of two different plants.
  • Apogamy: It can be defined as the development of a sporophyte directly from the gametophyte without the intervention of sex organs and gametes. The sporophyte formed usually has the same chromosome number as the gametophyte (i.e. the haploid number for the species). It is common and wide spread phenomenon in ferns.
  • Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers. Especially well known in peanuts, peas, and beans. 

Hence, the correct option is D.
NCERT Reference: Page no. 28 of topic “2.2.3 Pollination” of NCERT.

QUESTION: 19

Function of filiform apparatus is to: [2014]

Solution:
  • Filiform apparatus helps in the entry of pollen tube into a synergid in the ovule.
  • Filiform apparatus is in the form of finger like projection comprising a core of micro fibrils enclosed in a sheath. It resembles transfer cells meant for short distance movement of metabolites.
  • It is responsible for the absorption of food from the nucleus.

Hence, the correct option is D.

NCERT Reference: Page no. 27 of topic “2.2.2 The Pistil, Megasporangium (ovule) and Embryo sac” of chapter 2.

QUESTION: 20

Which of the following layers in the wall of an anther nourishes the developing pollen grains?

Solution:
  • The tapetum is a specialised layer of nutritive cells found within the anther of flowering plants, where it is located between the sporogenous tissue and the anther wall.
  • Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat.

Hence, the correct option is A.
NCERT Reference: Page no. 21 of topic “2.2.1 Stamen, Microsporangium and Pollen Grain” of chapter 2.

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