Sexual Reproduction in Flowering Plants VBQs Class 12 Biology

Please refer to Sexual Reproduction in Flowering Plants HOTs Class 12 Biology provided below with solutions. All HOTs for Class 12 Biology with answers provided below have been designed as per the latest syllabus and examination petter issued by CBSE, NCERT, KVS. Students of Standard 12 Biology should learn the solved HOTS for Class 12 Biology provided below to gain better marks in examinations.

Sexual Reproduction in Flowering Plants Class 12 Biology HOTs

Question. Asexual reproductive structures found in Penicillium are
(a) conidia
(b) buds
(c) gemmules
(d) zoospore

Question. Clones are
(a) morphologically similar individuals
(b) genetically similar individuals
(c) Both (a) and (b)
(d) None of the above

Question. ……. is the fastest method to obtain clones.
(a) Induced mutation
(b) Parasexual hybridisation
(c) Vegetative reproduction
(d) Parthenogenesis

Question. Asexual reproduction is common in
(a) single-celled organisms
(b) plants with relatively simple organisation
(c) animals with relatively simple organisation
(d) All of the above

Question. Organisms reproducing throughout the year are called …… breeders, e.g. … and those who show recurring sexual activity are called …… breeders, e.g. … .
(a) continuous, sparrow, seasonal, hen
(b) seasonal, lizard, continuous, hen
(c) continuous, man, seasonal, tiger
(d) seasonal, hen, continuous, tiger

Question. In diploid organism the gamete producing cells are called
(a) gamete mother cell
(b) meiocytes
(c) Both (a) and (b)
(d) None of these

Question. Select the correct sequence of events.
(a) Gametogenesis® Gamete transfer® Syngamy® Zygote® Cell division (Cleavage)® Cell differentiation® Organogenesis
(b) Gametogenesis® Gamete transfer® Syngamy® Zygote® Cell divison (Cleavage)® Organogenesis® Cell differentiation
(c) Gametogenesis® Syngamy® Gamete transfer® Zygote® Cell division (Cleavage)® Cell differentiation® Organogenesis
(d) Gametogenesis® Gamete transfer® Syngamy® Zygote® Cell differentiation® Cell division (Cleavage)® Organogenesis

Question. Identify the events (A, B, D and E) of sexual reproduction given below.
Choose the correct option.
(a) A–Gamete transfer, B–Gametogeneis, D–Zygote formation, E–Embryogenesis
(b) A–Gametogeneis, B–Gamete transfer, D–Zygote formation, E–Embryogenesis
(c) A–Gametogeneis, B–Zygote formation, D–Gamete transfer, E–Embryogenesis
(d) A–Gametogeneis, B–Gamete transfer, D–Embryogenesis, E–Zygote formation

Question. Diploid zygote is universal in
(a) All sexually reproducing organisms
(b) All asexually reproducing organisms
(c) All sexually and asexually reproducing organisms
(d) Only plants and animals

Question. Life begins in all sexually reproducing organism from a
(a) single-celled zygote
(b) double-celled zygote
(c) thick-walled zygote
(d) All of these

Question. Embryogenesis involves
(a) formation of embryo from zygote
(b) cell division via meiosis and differentiation
(c) Both (a) and (b)
(d) None of the above

Question. Identify the type of gametes shown in figure A, B and C, respectively. 
(a) A–Heterogametes, B–Isogametes, C–Homogametes
(b) A–Homogametes, B–Isogametes, C–Heterogametes
(c) A–Isogametes, B–Heterogametes, C–Heterogametes
(d) A–Heterogametes, B–Heterogametes, C–Isogametes

Question. Figure P represents the reproductive organs of a plant, Chara and figure Q represents the reproductive organs of an animal, earthworm. Select the option which correctly identifies male reproductive organs of the two organisms. 
(a) A and D
(b) B and C
(c) A and C
(d) B and D

Question. The condition in which male and female parts are present on different organisms, is called
(a) heterothallic
(b) dioecious
(c) unisexual
(d) All of these

Question. In flowering plants, the unisexual male flower is called …A… while the female is called …B… .
Flowering plants may be monoecious, e.g. …C… or dioecious, e.g. …D… .
Complete the paragraph by filling up the blanks.
(a) A–staminate, B–pistillate, C–date palm, D–coconut
(b) A–pistillate, B–staminate, C–date palm, D–papaya
(c) A–pistillate, B–staminate, C–Cucurbita, D–coconut
(d) A–staminate, B–pistillate, C–Cucurbita, D–papaya

Question. A scion is grafted to a stock. The quality of fruits produced will be determined by the genotype of AIIMS 2018
(a) stock
(b) scion
(c) Both (a) and (b)
(d) Neither (a) nor (b)

Question. Which one of the following generates new genetic combinations leading to variation? NEET 2016, 13
(a) Vegetative reproduction
(b) Parthenogenesis
(c) Sexual reproduction
(d) Nucellar polyembryony

Question. Sexual reproduction involves formation of male and female gametes by
(a) same individual
(b) different individual of opposite sex
(c) Both (a) and (b)
(d) All of the above

Question. Name the type of gametes formed in staminate and pistillate flower, respectively.
(a) Stamen, pollen
(b) Antherozoid, egg
(c) Stamen, ovum
(d) Ovum, antherozoid

Question. Which of the following is hermaphrodite?
(a) Ant
(b) Aphids
(c) Earthworm
(d) Cockroach

Question. Which among the following is unisexual species?
(a) Tapeworm
(b) Leech
(c) Cockroach
(d) All of these

Question. If the parent body is haploid then the gametes are
(a) haploid
(b) diploid
(c) triploid
(d) None of these

Question. Name the type of gametes found in algae.
(a) Homogametes
(b) Heterogametes
(c) Anisogametes
(d) All of these

Question. What is male gamete called in heterogametic condition?
(a) Antherozoid
(b) Sperm
(c) Egg
(d) Both (a) and (b)

Question. The condition, in which, both male and female reproductive organs are found on the same plant, is called
(a) unisexual
(b) bisexual
(c) monoecious
(d) Both (b) and (c)

Question. What does ‘P’ signifies in the diagram given below?
(a) Pistil
(b) Thick pericarp
(c) Thin pericarp
(d) Pollen tube

Question. Self-fertilisation occurs in the
(a) bisexual flower
(b) unisexual flower
(c) Both (a) and (b)
(d) dioecious flower

Question. In which of the following organisms self-fertilisation is seen?
(a) Peas
(b) Mustard
(c) Sweet potato
(d) All of these

Question. In some plants, the female gamete develops into embryo without fertilisation.
This phenomenon is known as NEET 2019
(a) parthenocarpy
(b) syngamy
(c) parthenogenesis
(d) autogamy

Question. 61 Syngamy may occur in ………… .
(a) external medium
(b) internal medium
(c) Both (a) and (b)
(d) None of these

Question. ‘Organisms exhibiting external fertilisation release a large number of gametes’. Why?
(a) These organisms shows great synchrony between thesexes
(b) In order to enhance the chances of syngamy
(c) To produce large number of offsprings as they are vulnerable to predators
(d) All of the above

Question. Identify the sequence of events shown in the diagram below. 
(a) Fission of gametes® New individual® Zygote
(b) Fusion of gametes® Zygote® New individual (cell 2n)
(c) Fission of gametes® Zygote® New individual (cell 2n)
(d) Stages in the gametogenesis

Question. Internal fertilisation is the one in which syngamy
(a) occur outside the body
(b) occur inside the body
(c) is followed by meiosis
(d) None of the above

Question. Choose the incorrect pair.
(a) Cell division in embryo – Increase the number of cells
(b) Cell differentiation – Form specialised tissues and organs
(c) Eggs covered by hard calcareous shell – Oviparous animals
(d) Zygote develops outside the body –Viviparous animals

Very Short Answer Type Questions

Question. State the function of filiform apparatus found in mature embryo sac of an angiosperm.
Answer : Filiform apparatus helps to guide the path of pollen tubes into synergid. 

Question. Give an example of a plant that came to India as a contaminant and is a cause of pollen allergy.
Answer : Parthenium or carrot grass.

Question. How many pollen grains and ovules are likely to be formed in the anther and the ovary of an angiosperm bearing 25 microspore mother cells and 25 megaspore mother cells respectively?
Answer : Microspore mother cells 25 × 4=100 pollen grains and from megaspore mother cells 25 ovules respectively. 

Short Answer Type Questions

Question. How many cells are present in the grains at the time of their release from anther ? Name the cells.
Answer : Pollen grain may be released at 2-celled stage. One vegetative and one generative cell.

Question. A pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage ?
Answer : In 2-celled stage, the mature pollen grain contains a generative and vegetative cell, whereas in 3-celled stage, one vegetative cell and two male gametes are present. 
The generative cell floats in the cytoplasm of vegetative cell. 

Question. Write the function of tapetum in anthers.
Answer : The tapetum is the inner most wall layer of the microsporangia (pollen sacs) in anthers. These cells nourish the developing microspore mother cells and pollen grains. Besides this it forms the exine, secrete pollenkitt and special proteins for pollen grains so as to recognize compatible stigmas.

Question. In a flowering plant, a microspore mother cell produce four male gametophytes while a megaspore mother cell form only one female gametophyte. Explain. 
Answer : A microspore mother cell/PMC on meiosis forms 4 functional pollen grains/male gametophyte 
A megaspore mother cell/MMC on meiosis also forms four megaspores but out of it only one is functional and other three degenerate.

Question. Differentiate between two cells enclosed in a mature male gametophyte of an angiosperm.
Answer : There are three cells enclosed in the male gametophyte of angiosperms out of which two are male gametes and one is tube cell or vegetative cell. The two male gametes are small, round and surrounded by a little cytoplasm.
They are situated towards the proximal part of the pollen tube, whereas the tube cell or vegetative cells are irregular in outline and is present in the distal part of the pollen tube. Two male gametes are functional and take part in double fertilization whereas the tube cell/vegetative degenerates after the growth of pollen tube. 

Question. (i) Draw a labelled diagram of a section of an enlarged view of microsporangium of an angiosperm.
(ii) Name the cells and the event they undergo to produce pollen grains.
Answer :

(ii) Microspore mother cell/pollen mother cell, through meiosis.
Detailed Answer :
(ii) There are the microspore mother cells (MMC) or pollen mother cells (PMC) in the microsporangium that produce pollen grains.
They are diploid (2n) cells and undergo meiosis to produce pollen grains. The process is called as microsporogenesis.

Question. Why are angiosperm anther called dithecous ?
Describe the structure of its microsporangium.
Answer : A typical angiosperm anther is bilobed with each lobe having two pollen sacs. Hence, angiosperm anther are called dithecous. 
Structure of Microsporangium : It is circular and is generally surrounded by wall layers namely, an endothecium, 2 or 3 middle layers and a tapetum.
(i) The endothecium performs the function of protection and helps in dehiscence of anther to release the pollen.
(ii) The middle layers and the innermost layer, tapetum nourishes the developing pollen grains. The cells of the tapetum possess dense cytoplasm and more than one nuclei.
(iii) When the anther is young, a group of compactly arranged homogenous cells called sporogenous tissues occupies the centre of each microsporangium which produce microspores or pollen grains.

Question. Draw a labelled diagram of the sectional view of a mature pollen grain of angiosperms. Explain the function of any two of its parts.
OR
Draw a labelled diagram of a mature pollen grain.
Answer :

Exine : It can withstand high temperature/strong acids/alkali. It protects pollens.
Intine : It is a thin and continuous layer made up of cellulose and pectin. The intine produces pollen tube.
Vegetative cell : It is bigger and has abundant food reserve.
Generative cell : It divides mitotically to give rise to two male gametes.

Question. (i) Draw a labelled sketch of a mature 7-celled, 8-nucleate embryo sac.
(ii) Which one of the cell in an embryo-sac produce endosperm after double fertilization ?
Answer :
(i)

(ii) Central cell.
Detailed answer :
(ii) After double fertilization the Primary Endosperm Nucleus (PEN) formed as a result of triple fusion (fusion of one male gamete (n) with a diploid secondary nucleus (2n) or with two haploid polar nuclei) produces endosperm.

Question. (i) Name the organic material exine of the pollen grain is made up of. How is this material advantageous to pollen grain
(ii) Still it is observed that it does not form a continuous layer around the pollen grain. Give reason.
(iii) How are ‘pollen banks’ useful ?
Answer : (i) Sporopollenin. 
Most resistant to high temperature / strong acids / alkali / no enzymes can degrade it.
(ii) (Germs pores) to allow pollen tube to emerge out / pollen germination. 
(iii) Helps in storing pollen grains for years / for crop breeding programmes. 
Detailed Answer :
(i) Exine is the hard, outer, protective covering of the pollen grain. It is made up of sporopollenin.
Sporopollenin is one of the most resistant organic compounds, which can withstand high temperature, strong acids and alkalies. It cannot be degraded by any of the known enzymes.
Hence, it acts as a shield and protects the pollen grain from getting damaged.
(ii) Exine does not form a continuous layer around the pollen grain. Hence, sporopollenin is absent over certain specific regions which are called germ pores. Germ pores serve as outlet for the growth and emergence of pollen tube.
(iii) Pollen grains can be stored for years in liquid nitrogen at – 196°C. After this treatment, they
are stored in pollen banks. Such conserved pollen grains can be later used in plant breeding
programs.

Long Answer Type Questions

Question. (i) Draw a labelled diagram of the sectional view of microsporangium of an angiosperm.
(ii) Explain the development of male gametophyte in the microsporangium.
Answer :
(i)

(ii) Each cell of sporogenous tissue, functions as microspore mother cells →, meiosis/ microsporogenesis, → microspore tetrad →,4-pollen grains (male gametophyte) 2-celled stage.

Question. (a) Draw a diagrammatic sketch of a transverse section of an anther of an angiosperm.
Label its different walls and the tissue forming microspore mother cells.
(b) Describe the process of microsporogenesis upto the formation of a microspore.
(c) Write the function of ‘germ pore’ in a pollen grain of an angiosperm. 
Answer : (a)

(b) Sporogenous tissue Mitosis Microspore mother cell Meiosis microspore tetrad
(c) Germ pores allow the germinating / growing pollen tube with contents of the pollen grain / male gametes + vegetative cell to come out of the pollen grains

Question. Draw a labelled diagram of sectional view of a mature embryo sac of an angiosperm.
OR
Draw a diagram of a mature embryo sac of an angiosperm and label the following parts in it :
(i) Filiform apparatus
(ii) Synergids
(iii) Central cell
(iv) Egg cell
(v) Polar nuclei
(vi) Antipodals.
Answer :

Question. (i) Describe the process of megasporogenesis of angiosperms until the 8-nucleate stage.
(ii) Draw the labelled structure of a mature embryo sac.
OR
How does the megaspore mother cell develop into 7-celled 8-nucleate embryo sac in an angiosperm ?
Draw a labelled diagram of a mature embryo sac.
Answer : (i) The process of formation of the megaspore from the megaspore mother cell is called megasporogenesis.
Ovules generally differentiate a single megaspore mother cell in the micropylar region of the nucellus. This mother cell undergoes meiosis and as a result forms a linear tetrad of 4 megaspores.
Usually one of the four megaspores towards the micropylar end is functional, while the other three degenerate. Only the functional megaspore develops into the female gametophyte (embryo sac).
The nucleus of the functional megaspore divides mitotically to form two nuclei, which move to opposite poles, forming 2-nucleate embryo sac.
Two more sequential mitotic nuclear divisions result in the formation of the 4 nuclei and the later 8-nucleate stage of the embryo sac.
(ii)

Megasporogenesis

• The formation of haploid megaspores from the diploid megaspore mother cell (MMC) as a results of meiosis is called megasporogenesis.
• A single megaspore mother cell is differentiated in the micropylar region of the nucellus.
• The megaspore mother cell is a large cell containing dense cytoplasm and a prominent nucleus.
• The megaspore mother cell undergoes meiotic division resulting in the production of four haploid megaspores.

Female gametophyte (Embryo sac)

• The remaining two nuclei called the polar nuclei are found below the egg apparatus in the large central cell.
• In most of the flowering plants, only one megaspore is functional while the other three degenerate.
• The functional megaspore develops into the female gametophyte or embryo sac.
• This method of embryo sac formation from a single megaspore is termed as monosporic development.

Development of Female gametophyte

• The nucleus of the functional megaspore divides mitotically to form two nuclei which move towards the opposite poles, forming two-nucleated embryo sac.
• Two more sequential mitotic nuclear divisions result in the formation of the four-nucleated and later the eightnucleated stages of the embryo sac.
• These divisions are strictly free nuclear, i.e. nuclear divisions are not followed immediately by cell wall formation.
• After eight-nucleate stage, the organization of the typical female gametophyte or embryo sac takes place.
• Generally six of the eight nuclei are surrounded by cell walls and organized into cells.

Distribution of the cells within the embryo sac

• The three cells consisting of two synergids and one egg cell which are grouped together at the micropylar end constitute the egg apparatus.
• The synergids have special cellular thickenings at the micropylar tip called filiform apparatus.
• The filiform apparatus helps to guide the pollen tubes into the synergid.
• Three cells at the chalazal end organize as the antipodals.
• Thus, a typical mature angiosperm embryo sac at maturity is eight-nucleate and seven-celled.