CHSE Odisha Class 12 Biology Solutions Chapter 2 Sexual Reproduction in Flowering Plants

Odisha State Board CHSE Odisha Class 12 Biology Solutions Chapter 2 Sexual Reproduction in Flowering Plants Textbook Questions and Answers.

CHSE Odisha 12th Class Biology Chapter 2 Question Answer Sexual Reproduction in Flowering Plants

Sexual Reproduction in Flowering Plants Class 12 Questions and Answers CHSE Odisha

Very Short Answer Type Questions

Fill in the blanks with correct answer from the choices given in the bracket

Question 1.
When gynoecium matures first it is called ………… to effect cross-pollination. (protogyny, protandry, herkogamy, unisexuality)
Answer:
protogyny

Question 2.
In ornithophily, the agents for cross-pollination are ………….. . (ants, birds, snails, rats)
Answer:
birds

Question 3.
Zygote develops from …………. cell of the embryo sac. (egg, synergid, antipodal, nucellus)
Answer:
egg

Question 4.
Fertilisation was discovered by …………. (Strasburger, Mendel, Nitsch, Bower)
Answer:
Strasburger

Question 5.
Due to triple fusion, ……….. is formed.
(zygote, embryo, endosperm, zoospore)
Answer:
endosperm

Question 6.
The innermost layer of wall layers is ………….. (tapetum, epidermis, endodermis, endothecium)
Answer:
tapetum

Question 7.
Straight ovules are called ……………… (anatropous, campylotropous, orthotropous, hemitropous)
Answer:
orthotropous

Question 8.
Contrivance of self-pollination is ………….. (dicliny, herkogamy, self-sterility, cleistogamy)
Answer:
cleistogamy

Answer each of the following in one word or more words

Question 9.
Androecium and gynoecium whorls are present in the same flower.
Answer:
Bisexual flower

Question 10.
Both the essential whorls are absent in a flower.
Answer:
Neuter flower

Question 11.
Petals are united in a flower.
Answer:
Gamopetalous

Question 12.
Free carpels in a flower.
Answer:
Apocarpous

Question 13.
Transfer of pollen grains from anther to stigma of the same flower.
Answer:
Self-pollination

Question 14.
The process in which the’male gamete fertilises with egg.
Answer:
Fertilisation

Question 15.
Pollination in aquatic plants.
Answer:
Hydrophily

Question 16.
Fusion of one male gamete with definitive nucleus.
Answer:
Triple fusion

Correct the statements without changing underlined words only

Question 17.
Anemophilous flowers are pollinated by ants.
Answer:
Anemophilous flowers are pollinated by wind.

Question 18.
Dichogamy is found in bisexual flowers where stamens and carpels mature at same time.
Answer:
Dichogamy is found in bisexual flowers where stamens. and carpels mature at different time.

Question 19.
The ovule is attached to the placenta of ovary by means of nucellus.
Answer:
The ovule is attached to the placenta of ovary by means of a stalk called funiculus.

Question 20.
Animals acting as agents of pollination are called anemophily.
Answer:
Animals acting as agents of pollination are called zoophily.

Question 21.
Polyembryony involves development of one embryo.
Answer:
Polyembryony involves development of more than one embryo from a single fertilised ovum.

Fill in the blanks

Question 22.
The cells present on two sides of egg in the egg apparatus are called ……………..
Answer:
synergids

Question 23.
The outer wall of the pollen grain is called …………..
Answer:
exine

Question 24.
The male gametes are formed from …………. cell.
Answer:
generative

Question 25.
Parthenogenesis means development of fruits without ……………….
Answer:
fertilisation

Question 26.
The endosperm in which first division is cellular and subsequential cellular is called ……………… endosperm.
Answer:
cellular

Question 27.
In grafting, the part of the plant detached is called ………….
Answer:
scion

Question 28.
In self-pollination, pollen is transferred to stigma of the ………….. flower.
Answer:
same

Question 29.
The fertile cells from which microspores or megaspores developed are called ………….. cells.
Answer:
diploid mother

Question 30.
In maize plant, male inflorescence is borne at portion of the plant.
Answer:
tassel

Question 31.
The fusion product of male gamete and egg cell in angiosperms form …………….
Answer:
zygote

Short Answer Type Questions

Write notes on the following with at least 2 valid points

Question 1.
Parthenogenesis
Answer:
Refer to text on page no. 41.
The word parthenogenesis is derived from two Greek words, parthenos means ‘virgin’ and genesis means ‘origin’. It can be defined as the formation of embryo from an unfertilised egg or female gamete. In plants, parthenogenesis is a component process of apomixis.
In parthenogenesis, the haploid egg in which no ‘ fertilisation occurs, develop into an embryo. This forms – viable seed which can give rise to a new plant. In , contrast, in parthenocarpy if seeds develop, they are abortive and do not give rise to new plants.

Question 2.
Allogamy
Answer:
Cross-pollination is also called allogamy. It is the transfer of pollen grains from anther of flower to stigma of flower on another plant of same or allied species.

Question 3.
Herkogamy
Answer:
Herkogamy is seen in orchids where male or female sex organs themselves prove as a barrier to prevent self-pollination by some structural abnormalities.

Question 4.
Geitonogamy
Answer:
It is a kind of pollination where the pollen grains from the anther of a flower are transferred to the stigma of another flower borne on the same plant but at different branches. It usually occurs in plants which show monoecious condition, e.g. Cucurbita. It is functionally a type of cross-pollination (involving a pollinating agent), but genetically it is similar to autogamy (since pollen grains come from same plant).

Adaptations (Contrivances) for Self-Pollination
The contrivances of self-pollination include homogamy, dichogamy and cleistogamy.

• Homogamy In this condition, both anther and stigma mature at the same time, e.g. Mirabilis.
• Dichogamy In this condition, anther and stigma mature at different times, e.g. sunflower.
• Cleistogamy The flowers which are always closed are known as deistogamous, e.g. Oxalic
  

Advantages of SeLf-PoLlination

• Fertilisation and production of the progeny are always certain by this method.
• It maintains purity of race and superiority of the variety.
• Here there is less wastage of pollens.

Disadvantages of SeLf-Pollination

• It leads to loss of viability and vigour of the plant in the long run.
• If lethal genes become homozygous, the effect may be disastrous.

Question 5.
Xenogamy
Answer:
Cross-pollination within a species (different variety) is called xenogamy and it results in production of hybrids.

Question 6.
Self-sterility
Answer:
Self-incompatibility or Self-sterility is the third device to prevent inbreeding. It is a genetic phenomenon of preventing the pollen from fertiismg ovules by the same flower by inhibiting pollen germination or pollen tube growth în the pistil.
Self-incompatibility may be due to genotype of sporophyte known as sporophytic incompatability whereas if it is due to genotype of pollen, it is known as gametophytic incomparibility.

Question 7.
Entomophily
Answer:
Pollination taking place under water is known as hypohydrogamous whereas pollination taking place on surface of water is cailed epihydrogamous.

Question 8.
Embryo sac
Answer:
Embryo sac refers to female gametophyte of a plant.
Refer to text on page no. 25.
Organisation of Female Gametophyte (Embryo Sac)
In general, the development of embryo sac is monosporic, e.g. in Polygonum. In this type of development, only one megaspore situated towards chalazal end remains functional, while the remaining three megaspores gradually degenerate and finally disappear. Following are the different stages in development of female gametophyte

1. The functional haploid megaspore is the first cell of female gametophyte of angiosperm.
2. It enlarges in size to form the female gametophyte, also called embryo sac.
3. Its nucleus undergoes mitotic division to form 2-nuclei that move to opposite poles forming 2-nucIeate embryo sac.
4. The 2-nucleate embryo sac undergoes two more sequential mitotic divisions giving rise to the 4-nucleate stage and later 8-nucleate stage of embryo sac. This stage comprises of a micropylar end and a chalazal end with four nuclei at each end.
5. Six of the eight nuclei are surrounded by cell walls and get organised into cells. Three cells present towards the micropylar end grouped together, constitute the egg apparatus, i.e. two synergids and one egg cell.
6. Three cells of the chalazal end are called the antipodals. The large central cell is formed by the fusion of 2-polar nuclei. Thus, a typical angiospermic embryo sac or female gametophyte at maturity consists of 8-nuclei and 7-cells.

The egg cell combines with a male gamete to form zygote which becomes the embryo. The pollen tube makes its way through the synergids releasing the male gametes.

One male gamete fuses with female gamete (egg) called syngamy. The two polar nuclei which have fused to form secondary nucleus combine with second male gamete and form primary endosperm cell. This primary endosperm cell develops into endosperm which provides nutrition to the developing embryo. The antipodal cells degenerate.

Question 9.
Embryo
Answer:
Development of an Embryo: The first stage in the development of a plant zygote is a pre-determined mode of development (embryogeny).

It gives rise to an organised mass of cells called the embryo, that has the potentiality to form a complete plant. Most zygotes divide only after certain amount of endosperm is formed to assure proper nutrition is provided to the developing embryo.
In the majority of angiosperms, the zygote (fertilised egg) divides by an asymmetric mitotic division and generates two cells with two different fates

1. The smaller daughter cell with dense cytoplasm is situated towards the chalazal pole side. It is called terminal cell or apical cell or embryonal cell.
2. Another comparatively larger daughter cell situated towards the micropylar cell is called basal cell. This cell divides transversely and gives, rise to suspensor cells. The zygote gives rise to the proembryo anti subsequendy to the globular, heart-shaped and mature embryo.

Though the seeds differ greatly, the early stages of embryo development (embryogeny) are similar in monocots and dicots.

Question 10.
Micropropagation
Answer:
Micropropagation It is the production of large number of individual plants from a small piece of plant tissue cultured in a nutrient medium. It leads to formation of clones. It is a fast method of plant production.

Question 11.
Polyembryony
Answer:
Polyembryony
In general, each seed bears an embryo, but sometimes there are found more than one embryo in a single seed. The occurrence of more than one embryo in a seed is called polyembryony. It was first time observed in orange seeds by Antony van Leeuwenhoek in 1719.
On a broad basis, polyembryony is of two types
(i) Spontaneous It includes naturally occurring polyembryony.
(ii) Induced This type of polyembryony is induced experimentally.

Question 12.
Incompatibility
Answer:
Incompatibility It is the inability of the pollen grains to germinate on the stigma of genetically similar plants or the failure of gametes to fuse or inability of the zygote to develop into a mature sporophyte.

Differentiate the following with at least three valid and meaningful points.

Question 1.
Pollination and Fertilisation.
Answer:
Differences between pollination and fertilisation are as follows

Pollination	Fertilisation
It refers to the transfer of pollen grains from an anther to stigma.	It refers to the fusion of male and female
It is a physical process.	It is cellular, genetic, biochemical process.
It can be achieved by various agents such as wind, insect, etc.	It is assisted by the plant itself.

 

Question 2.
Dichogamy and Herkogamy.
Answer:
Differences between dichogamy and herkogamy are as follows

Dichogamy	Herkogamy
When stamens and carpels of bisexual flowers mature at different times to prevent self-pollination, it is called dichogamy.	When some sort of barrier develops between stamens and pistil of same flowers and prevents self-pollination, it is called herkogamy.
It is of two types, i.e. protogyny and protoandry.	It is seen in Calotropis, etc.
It is seen in banana, coriander, etc.	It also prevents cross-pollination.
It prevents self-pollination.	Herkogamy

 

Question 3.
Protogyny and Protandry.
Answer:
Differences between protogyny and protandry are as follows

Protandry	Protogyny
In this, the anthers mature earlier so that its stigma is not ready to receive pollen from its anther.	In this, stigmas mature earlier so that they get pollinated before the anthers of the same flower mature and develop pollen grains.
e.g. in Salvia, sunflower, cotton, jasmine, etc.	e.g. in Plantago, Mirabilis jalapa, peepal, banyan, etc.

 

Question 4.
Self-pollination and Cross-pollination.
Answer:
Differences between self-pollination and cross-pollination are as follows

Self-pollination	Cross-pollination
Pollen grains are transferred from anther to stigma of the same flower (autogamy) or another flower borne on the same plant (geitonogamy).	Pollen grains are transferred from anther of one flower to stigma of another flower borne on a different plant of the same species (allogamy).
Both anthers and stigma mature at the same time.	The anthers and stigma of a flower mature at different times.
External agent is not required for self-pollination.	An external agent is essential for cross-pollination.
It is economical for the plant.	Cross-pollination is not economical as the plant has to produce a large number of pollen grains, nectar, ‘ scent and bright coloured corollas, etc.
It results in progenies which are purelines, e.g. homozygous.	It results in hybrids, e.g. heterozygous. They show variations in characters.

 

Question 5.
Embryo and Endosperm.
Answer:
Differences between embryo and endosperm are as follows

Embryo	Endosperm
It is formed by fertilised egg. (syngamy).	It is formed by fusion of secondary nucleus (triple fusion).
It is always diploid.	It is triploid. ‘
It gives rise to new plant.	It provides nutrition to the developing embryo.
Cotyledons, plumule and radicle are formed in embryo.	There is no formation of such structures.
Embryo is seen in seed.	It is only seen in endospermic seeds. Otherwise it degenerates with the formation of seed.

 

Question 6.
Gamete and Zygote.
Answer:
Differences between gamete and zygote are as follows

Gamete	Zygote
It is the cell that fuses with another cell in order to form zygote during fertilisation,	It is the fused product between an egg and a sperm.
Ploidy level of gametes is haploid.	Ploidy level of zygote is diploid.
Gamete is found in both male and female.	Zygote is only present in female.

 

Question 7.
Micropyle end and Chalazal end.
Answer:
Differences between micropyle end and chalazal end are as follows

Micropyle end	Chalazal end
In seed bearing plants, a small opening in the integuments of the ovule through which sperms are able to access the ovum.	In seed bearing plants, the location where the nucellus attaches to the integuments, opposite the micropyle.

 

Question 8.
Zoophily and Anemophily.
Answer:
Differences between zoophily and anemophily are as follows

Zoophily	Anemophily
Animal pollination is termed as zoophily. These animals can be bats, insects, birds, ants, etc.	Wind pollination is also termed as anemophily.
These flowers are large, colourful, fragrance and rich in nectar.	These flowers are small, colourless, inconspicuous and nectarless.
The pollen grains are produced in less number.	The pollar grains produced are more in number.

 

Question 9.
Double fertilisation and Triple fusion.
Answer:
Differences between double fertilisation and triple fusion are as follows

Double fertilisation	Triple fusion
It involves two processes, i.e. triple fusion and syngamy.	It is a process in angiosperms which occurs along with syngamy in the embryo.
It involves two sperm cells or male gametes.	It involves a single male gamete.
After double fertilisation zygote and an endosperm is formed.	It involves fusion of a male gamete with polar nuclei to form triploid endosperm.

 

Question 10.
Porogamy and Chalazogamy
Answer:
Differences between porogamy and chalazogamy are as follows

Porogamy	Chalazogamy
It is the condition when the pollen tube enters the ovule from the micropylar end during fertilisation.	It is the condition of entering of pollen tube from chalazal end during fertilisation.
e.g. in lily, etc.	e.g. in Casuarina, Jug Ians, etc.

 

Question 11.
Apospory and Apogamy.
Answer:
Differences between apospory follows and apogamy are as

Apospory	Apogamy
It is a type of reproduction in which gametophyte develops from sporophyte without meiosis and involvement of spores. The gametophyte usually develops from vegetative cells of sporophyte.	It is a type of reproduction in which sporophyte develops from gametophyte without fertilisation or fusion of gametes. The sporophyte usually develops from vegetative cells of gametophyte.

 

Question 12.
Monocot and Dicot embryo.
Answer:
Differences between monocot and dicot embryo are as follows

Monocot embryo	Dicot embryo
Basal cell forms a 6-10 celled suspensor.	Basal cell produces a single-celled suspensor.
Terminal cell produces embryo except the radicle.	It forms the whole of the embryo.
The first division of terminal cell is generally longitudinal.	It is transverse.
It has two cotyledons.	There is a single cotyledon.
Plumule is terminal and lies in between the two elongated cotyledons.	Plumule appears lateral due to excessive growth of the single cotyledon.

 

Question 13.
Nuclear and Cellular endosperm. (2018)
Answer:
Differences between nuclear and cellular endosperm are as follows

Nuclear endosperm	Cellular endosperm
Nuclear divisions are not followed by cell divisions.	Each division of nuclei is immediately followed by cell divisions.
The nuclear mass is then pushed to periphery and cell walls are laid. Mostly cell wall formation remains incomplete.	Complete cell walls are laid from the very beginning and a solid cellular mass is obtained,
A central vacuole is formed initially which ultimately disappears with a few exceptions.	No such vacuole is formed generally.
e.g. wheat, maize, rice, etc.	e.g. balsam, Datura, Petunia, etc.