CBSE Class 12 Biology Reproduction In Flowering Plants Worksheet Set B

Important Questions for NCERT Class 12 Biology Sexual Reproduction in Flowering Plants

Question. Polar nuclei are situated in the central cell
(a) Below the egg apparatus
(b) Above the egg apparatus
(c) Below the antipodals
(d) All of the above

Answer : A

Question. The synergids have special cellular thickening at the micropylar tip, called
(a) Antipodals
(b) Filiform apparatus
(c) Obturators
(d) Vascular tissue

Answer : B

Question. Which of the following part of the flower serves as a landing platform for pollen grain ?
(a) Stigma
(b) Ovary
(c) Style
(d) Ovule

Answer : A

Question. Embryo develops at which end of embryosac?
(a) Micropylar end
(b) Chalazal end
(c) Funiculus
(d) Outside the ovary

Answer : A

Question. The microsporangia develop further and become pollen sacs. In anther these pollen sacs extends
(a) Transverslly
(b) Longitudinally
(c)Obliquely
(d) Sometimes transversaly and some times longitudinally

Answer : B

Question. Enclosed within the integuments is a mass of cells called
(a) Micropyle
(b) Nucellus
(c) Chalaza
(d) Embryosac

Answer : B

Question. An example of insect pollinated flower, in which flower provides safe place to lay eggs for insect is
(a) Vallisneria
(b) Salvia
(c) Amorphophallus
(d) Maize

Answer : C

Question. Endosperm development precedes embryo development, because
(a) Embryo provides nutrition to developing endosperm
(b) Endosperm provides nutrition to developing embryo
(c) Endosperm development starts after embryo development
(d) All of the above

Answer : B

Question. The portion of embryonal axis above the level of cotyledons is called
(a) Hypocotyl
(b) Epicotyl
(c) Tigellum
(d) Scutellum

Answer : B

Question. Egg apparatus consists of
(a) Egg
(b) Egg and polar nuclei
(c) Egg and synergids
(d) Egg and antipodal cells.

Answer : C

Question. Double fertilisation involves:
(a) Syngamy + triple fusion
(b) Double fertilisation
(c) Development of antipodal cell
(d) None of the above.

Answer : A

Question. Triploid tissue in angiosperms is:
(a) Nucellus
(b) Endosperm
(c) Endothecium
(d) Tapetum.

Answer : B

Question. Persistent nucellus in black pepper is called
(a) Pericarp
(b) Perisperm
(c) Primary endospermic nucleus
(d) Endosperm

Answer : C

Question. In a monocot, endosperm cells have24 chromosomes. What shall be the chromosome number in embryo:
(a) 24
(b) 16
(c) 12
(d) 8

Answer : B

Question. Endosperm of flowering plants develops from:
(a) Haploid nucleus
(b) Diploid nucleus
(c) Triploid nucleus
(d) Tetraploid nucleus.

Answer : C

Question. Secondary nucleus present in the middle of embryo sac is:
(a) Tetraploid
(b) Triploid
(c) Diploid
(d) Haploid.

Answer : C

Question. The root cell of a wheat plant has 42 chromosomes. What would be the number of chromosomes in the synergid cell?
(a) 7
(b) 14
(c) 21
(d) 28.

Answer : D

Question. In nature cleistogamous flowers are:
(a) Wind pollinated
(b) Bird pollinated
(c) Self-pollinated
(d) Insect pollinated

Answer : C

Question. The outermost layer of maize endosperm is known as:
(a) Perisperm
(b) Aleurone
(c) Tapetum
(d) Endothecium

Answer : B

Question. Through which cell of the embryo sac, does the pollen tube enter the embryo sac?
(a) Egg cell
(b) Central cell
(c) Persistent synergid
(d) degenerated synergid.

Answer : D

Question. In Banana edible part is:
(a) Fleshy epicarp
(b) Rudimentary mesocarp and fleshy endocarp
(c) Pericarp
(d) Rudimentary endocarp and fleshy mesocarp

Answer : D

Question. The portion of embryonal axis below the level of cotyledons is called
(a) Hypocotyl
(b) Epicotyl
(c) Tigellum
(d) Scutellum

Answer : A

Assertion Reason Type Questions:

A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are true but reason is not the correct explanation of Assertion.
C. If Assertion is true but Reason is false.
D. If both Assertion and Reason are false.

Question. Assertion: Seed disposal by wind is called as anemochory.
Reason: The seeds are light, minute and may be winged.

Answer : A

Question. Assertion: If an endosperm cell of angiosperm contains 24 chromosomes, the number of chromosomes in the cell of root will be 16.
Reason: As the endosperm is triploid and root cells are diploid, the chromosome number in each of root cell will be 16.

Answer : C

Question.Assertion: The first part of the dicot embryo to appear above ground is the leaf.
Reason: Leaves increase the size of plants.

Answer : C

Question. Assertion: Megaspore mother cell undergoes meiosis to produce four megaspores.
Reason: Megaspore mother cell and megaspores both are haploid.

Answer : C

Question. Assertion: 7-celled 8- nucleate and monosporic embryo sac is called polygonum type of embryo sac.
Reason: It was discovered by Hofmeister for the first time in Polygonum.

Answer : C

Question. Assertion: Seeds fail to germinate at very low and high temperatures.
Reason: Seed sown deep into the soil fails to germinate.

Answer : B

Question. Assertion: Continued self-pollination generation after generation results in pure line formation.
Reason: By continued self-pollination, plants become pure or homozygous for its characters.

Answer : A

Question. Assertion: Some fruits are seedless or contain empty or non-viable seeds.
Reason: They are produced without fertilisation.

Answer : A

Question. Assertion: Ovule after fertilisation forms the fruit.
Reason: The fruit contains diploid endosperm.

Answer : D

Question. Assertion: Cross pollination in true genetic sense within species is called xenogamy.
Reason: When there is cross pollination, resultant hybrid is a combination of characters of two plants.

Answer : A

Question. Assertion: Insects visit flowers to gather honey.
Reason: Attraction of flowers prevents the insects from damaging the parts.

Answer : C

Question. Assertion: Red colour of flowers attracts butterflies and wasps, but not bees.
Reason: Bees are colour-blind to red.

Answer : A

Short Answer Type Questions:

Question. Name all the haploid cells present in an unfertilised mature embryo sac of a flowering plant. Write the total number of cells in it.
Answer : One female gamete, two synergids, and three antipodal cells are the haploid cells.
In total, there are seven cells in the mature embryo sac.

Question. Mention one advantage and a disadvantage of a cleistogamous flower.
Answer : Advantage: Since cleistogamous flowers are autogamous, there is an assured seed set.
Disadvantage: Continued self-pollination leads to inbreeding depression.

Question. Name the product of fertilisation that forms the kernel of coconut. How does the kernel differ from coconut water?
Answer : Primary endosperm cells form the kernel of coconut.
The kernel of coconut is the cellular endosperm, while the coconut water is the Free-nuclear endosperm.

Question. You are given caster and bean seeds. Which one of the two, would you select to observe the endosperm?
Answer : (a) Caster seeds.
(b) The development of endosperm precedes that of embryo as an adaptation to Provide assured nutrition to the developing embryo.

Question. Name the type of fruit, apple is categorised under and why? Mention two other examples, which belong to the same category as apple.
Answer : Apple is categorised as false fruit, because the thalamus, a part of a flower other than the ovary, also contributes to fruit formation.
When the part of the flower other than the ovary becomes a part of the fruit, The fruit is said to be a false fruit.
The other examples are strawberry and cashew.

Question. It is said apomixes is a type of asexual reproduction. Justify.
Answer : Since apomixis does not involve formation and fusion of gametes, it is considered as a method of asexual reproduction.
Embryos develop from the cells of integument or nucellus involving mitotic division, apomictic, embryos are genetically similar.

Question. Differentiate between parthenocarpy and parthenogenesis. Give one example of each.
Answer : 7. Parthenocarpy:
Parthenocarpy is the phenomenon of formation of fruits without fertilisation usually seeds are not produced or not viable
Eg. Banana.
Parthenogenesis:
Parthenogenesis is the phenomenon in which the unfertilised female gamete Or ovum develops into an adult/individual
Eg. Drones of honey bees.

Question. Do all pollen grains remain viable for the same length of time? Support your answer with two suitable examples.
Answer : (a) No, the pollen grains of two different species remain viable for different periods of time.
Eg. Pollen grains of cereals remain viable for less than 30 minutes whereas some members of Rosaceae, Leguminosae and Solanaceae retain the pollen viability for months.
(b) In the pollen banks, pollen grains are stored in liquid nitrogen (at -196 C).
such stored pollen grains can be used for breeding programmes whenever necessary.

Question. If you squeeze a seed of orange, you might observe many embryos of different sizes. How is it possible? Explain.
Answer : It is a case of polyembryony, the phenomenon of occurrence of more than one embryo In a seed.
Some of the nucellar cells surrounding the embryo sac start dividing, protrude Into the embryo sac and develop into embryos.

Question. Gynoecium of a flower may be apocarpous or syncarpous. Explain with the help of an Example each.
Answer : Apocarpous pistil:
When the carpels of a multicarpellary pistil are free, it is called an apocarpous pistil.
Eg. Michelia.
Syncarpous pistil:
When the carpels of a multicarpellary pistil are fused together, it is called a syncarpous pistil.
Eg. Papaver, brinjal.

Question. Parthenocarpy and apomixis have been observed in some plants. Give an example of each. State a similarity and a difference observed between the two processes.
Answer : Parthenocarpy is seen in banana Apomixis is seen in Citrus, mango, some members of Asteraceae and grasses.
Similarity: -
There is no fertilisation involved in both parthenocarpy and apomixis
Difference: -
Parthenocarpy is fruit formation without fertilisation, the fruits are seedless or the Seeds are not viable Apomixis is seed formation without fertilisation

Question. Explain the mechanism of pollination in marine /seagrass like Zostera.
Answer : In sea grasses like Zostera, the female flowers remain submerged in water.
The pollen grains are released inside the water.
pollen grains are long and ribbon like, they are carried passively by water Some of them reach the stigma and achieve pollination.

Question. Mention the ploidy of the different types of cells present in the female gametophyte of an Angiosperm.
Answer : (1). Antipodal cell—Haploid.
(2) Central cell—Diploid (when the two polar nuclei fuse to form a secondary nucleus)
(3). Female gamete (egg cell)—Haploid.
(4) Synergids- Haploid.

Question. Write the differences between wind-pollinated and insect pollinated flowers. Give examples of each type.
Answer : Wind pollinated flowers:
The flowers are small, and not showy or fragrant They do not produce nectar.
Stamens are well exposed.
Pollen grains are light and non-sticky Often, they have feathery stigma
Eg. Maize, Cannabis
Insect pollinated flowers:
The flowers are large, showy and fragrant.
They produce a large quantity of nectar.
Stamens are not exposed Pollen grains are sticky stigma is also sticky
Eg. Yucca, Sunflower.

Question. Where are the following structures present in a male gametophyte of angiosperms? Mention the function of each of them.
Answer :(a) Germ pore present in the exine, where sporopollenin is absent.
The intine grows out through the germ pore as pollen tube
(b) Sporopollenin forms the exine of pollen grain.
(c) Generative cell floats in the cytoplasm of the vegetative cell of the Pollen grain.
It divides mitotically to form two male gametes

Question. In plant breeding experiments, pistillate flowers are not emasculated, but are still bagged. Explain.
Answer : 6. (a) In plant breeding experiments, pollen from the selected male parent only, are used for pollination To prevent contamination of the stigma by any other pollen grain, the pistillate flowers are bagged.
(b) Continued self-pollination leads to inbreeding depression; hence To discourage self-pollination, out breeding devices are developed by flowers.

Question. Explain the different modes of pollination that can occur in a chasmogamous flower.
Answer : (a) Autogamy: It refers to the transfer of pollen grains from the anther to the stigma of the same flower.
(b) Geitonogamy: It refers to the transfer of pollen grains from the anthers of flowers to the stigma of another flower of the same plant.
(c) Xenogamy: It refers to the transfer of pollen grain from the anther of a flower to the stigma of another flower on a different plant of the same species.

Question. Apomixis resembles asexual reproduction as well as mimics sexual reproduction in plants. Explain the help of a suitable example.
Answer : Apomixis resembles asexual reproduction, as there is no formation of gametes and fertilisation and the apomictic embryos are genetically identical among
Themselves and to the parent cell.
It mimics sexual reproduction as embryos and seeds are formed.
In citrus and mango, some of the cells of nucellus around the embryo Sac starts dividing, get pushed into the embryo sac and develops into embryos.
In members of Asteraceae, a diploid egg cell is formed without meiosis In the megaspore mother cell, it develops without fertilisation into an Embryo.

Question. Name and explain the mechanism by which the seeds from hybrid plants are developed that are able to retain the desired hybrid characters in the progeny.
Answer : Apomixis is the mechanism.
It refers to the form of asexual reproduction that mimics sexual reproduction and Seeds are formed without fertilisation.
Since there will be no segregation of the hybrid characters in the progeny plants, They will be maintained for a number of generations.

Question. Write the cellular contents carried by the pollen tube. How does the pollen tube gain its entry into the embryo sac?
Answer : Pollen tube carries two male gametes and the vegetative nucleus.
Pollen tube grows through the tissues of stigma and style to reach the ovary.
It enters the ovule through the micropyle and then enters the embryo sac through The filiform apparatus of one of the synergids.

Question. Majority of angiosperms have hermaphrodite flowers, but self-pollination is discouraged by them. Explain any three outbreeding devices that they have developed to achieve it.
Answer : The outbreeding devices are as follows.
(1) Self incompatibility is the genetic mechanism that prevent self-pollen from Fertilising the ovule by inhibiting pollen germination or retarding the growth of Pollen tube.
(2) Certain plant species produce male and female flowers on different plants, i.e. the plants are Dioecious; this prevents both autogamy and geitonogamy
(3) Pollen release and stigma receptivity are not synchronised, either the anthers Mature first or the pistil mature first
(4) The anthers and stigma of a flower are placed in such a way that the pollen of the flower cannot fall on the stigma of the same flower.

Question. State what apomixis is. Comment on its significance. How can it be commercially used?
Answer : Apomixis is a form of asexual reproduction that mimics sexual reproduction and seed are formed without fertilisation
Apomixis Is of significance in the hybrid seed industry.
If the hybrids are made into apomicts, there will be no segregation of the hybrid characters in the progeny plant The farmers can use the hybrid seeds to raise new crops year after year and they need not buy the costly hybrid seeds.

Long Answer Type Questions:

Question. (a) when a seed of an orange is squeezed, many embryos, instead of one, are observed. Explain how it is possible.
(b) Are these embryos genetically similar or different? Comment.
Answer : 2. (a) It is a case of polyembryony, i.e. the occurrence of more than one embryo in a seed.
In oranges, some of the nucellar cells around the embryo sac start dividing, protrude into the embryo sac and develop into the embryos, i.e. apomictic embryos are formed without fertilisation.
(b All the apomictic embryos are genetically similar among themselves and to the female parent as they have developed from the nucellar cells and involve only mitotic division.
The zygotic embryo in the same seed will be genetically different from these apomictic embryos, as it has developed from the zygote, which is formed by fusion of gametes from two different parents.

Question. (a) Describe any two devices in a flowering plant, which prevent both autogamy and geitonogamy.
(b)Explain the events up to fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm
Answer : (A) Dioecy and self-incompatibility are the two phenomenon which can prevent
Both autogamy and geitonogamy.
Dioecy is a phenomenon in which male and female flowers are produced on different plants of the same species, as in date palm and papaya.
Self-incompatibility is a genetic mechanism that prevents the self-pollen from fertilising the ovule by inhibiting pollen germination of pollen tube growth on the pistil.
(b) Double fertilisation:
The pollen tube discharges two male gametes after entering one of the synergids.
One of the male gametes fuses with the female gamete to form a zygote; this process is called syngamy The other male gamete fuses with the secondary nucleus (formed by the fusion of two polar nuclei) to form the primary endosperm nucleus (PEN); this process is called triple fusion.

Question Based on High Order Thinking Skills(HOTs) 

Question. The flask-shaped organ A at the centre of a flower is surrounded by a number of little stalks B having swollen tops which lie just inside the ring of petals.
(a) Name A. What are the various parts of A ?
(b) Which part of A contains gametes ?
(c) Name B. What is the swollen top of B known as ?
(d) What does the swollen top of B contain ?
(e) Out of A and B, which one is (i) male part, and (ii) female part of the flower ?
Answer : (a) A is carpel (or pistil) ; Stigma, Style and Ovary (b) Ovary (c) B is stamen ; Anther (d) Pollen grains (e) (i) B (ii) A

Question. When an insect sits on the flower of a plant then some particles A present in the top of little stalks in the flower attach to its body hair. When this insect now sits on the flower of another similar plant, then particles A attached to the hair of insect are put on the top of a flask-shaped organ at the centre of flower. The particle A grows a long tube B from the top of flask-shaped organ through which C moves down and reaches the bottom part of flask-shaped organ. Here C fuses with the nucleus of D contained in structure E.
The fusion of C and D forms a new cell F which grows and develops into a seed of the plant.
(a) What are particles A ? What is the process of transferring A from one flower to another flower of similar plant by the insect known as ?
(b) What is the name of tube B ?
(c) What is C which moves down through the tube B ?
(d) Name D and E.
(e) What is F ?
Answer : (a)A are pollen grains ; Cross-pollination (b) Pollen tube (c) C is male gamete (d) D is female gamete (ovum or egg) ;E is ovule (e) F is fertilised egg (zygote)

Question. When a human female reaches a certain age then vaginal bleeding occurs for a few days after regular time intervals.
(a) What is this process known as (i) in scientific terms, and (ii) in everyday language ?
(b) At what approximate age this process starts in human females ? What is the human female said to have attained at this stage ?
(c) After how much time is this process repeated ? For how many days this process usually lasts ?
(d) What does the onset of this process in human females signify ?
(e) At which particular event in the life of a human female this process stops temporarily but starts again ?
(f) At which approximate age of human female this process stops permanently ?
Answer : (a) (i) Menstruation (ii) Periods (b) 10 to 12 years ; Puberty (c) 28 days ; About 3 to 5 days (d) That the reproductive system of human female has started working (e) Beginning of pregnancy (f) About 45 to 50 years.

Question. X and Y are two human beings. The organ A in the reproductive system of X releases a mature gamete B once a month which goes into a tube-like structure C through a funnel-like opening. The organ D in the reproductive system of Y makes and releases gametes E which pass through a duct F and are introduced by an organ of Y, into the body of X. B and E fuse together in C to form a new cell G. The cell G divides repeatedly to form a ball of cells H which gets embedded in the lining of organ I of reproductive system of X where it grows and develops into a baby.
(a) Name (i) organ A, and (ii) gamete B.
(b) Write two names of tube-like structure C.
(c) Name (i) organ D, and (ii) gamete E.
(d) Write two names of duct F.
(e) Name (i) cell G (ii) ball of cells H, and (iii) organ I.
(f) Out of X and Y, which one is (i) male, and (ii) female ?
Answer : (a) (i) Ovary (ii) Ovum (or Egg) (b) Fallopian tube ; Oviduct (c) (i) Testis (ii) Sperm (d) Sperm duct ; Vas deferens (e) (i) Zygote (Fertilised egg) (ii) Embryo (iii) Uterus (or Womb) (f) (i) Y is male (ii) X is female

Question. When a fertilised egg E formed in the oviduct of a human female divides repeatedly to form an embryo, the embryo gets implanted in the thick and soft lining of the uterus. After this a disc-like special tissue T develops between the uterus wall and embryo through which all the requirements of the developing embryo (and foetus) are met from the mother’s body. The embryo is connected to the tissue T through a string like structure S.
(a) What is the other name of fertilised egg cell E ?
(b) What is the name of tissue T ?
(c) Name the string-like structure S .
(d) Name two substances which pass from mother’s blood to embryo through tissue T and, one type of substance which passes from embryo to mother’s blood.
(e) What happens to S when the baby is born ? Why ?
Answer : (a) Zygote (b) Placenta (c) Umbilical cord (d) From mother’s blood to embryo : Oxygen and Nutrients ; From embryo to mother’s blood : Wastes (e) S (umbilical cord) is tied and then cut ; To separate the new born baby from the mother

Question. When a female child is born, her ovaries already contain thousands of immature eggs (or ova) contained in immature structures A. On maturing, A bursts open and an egg shoots out of the ovary in a process called B. The process B starts in the females at puberty and occurs again and again after a time period x. Before every occurrence of process B, the inner lining of uterus becomes thick and soft with lots of blood vessels in it. When the egg cell gets fertilised by a sperm, then an event C occurs in the life of mature human female which lasts for time period y leading to the birth of baby. If, however, the egg cell released by the ovary does not get a sperm to fuse with, then the thick and soft inner lining of uterus breaks down and comes out of the female’s body in an event called D. The occurrence of event D is controlled by chemical substances E.
(a) What are A ?
(b) What is process B ?
(c) What is the time period x ?
(d) Name the event C.
(e) How much is the time period y ?
(f) What is the name of process D ?
(g) Name the chemical substances E.
Answer : (a) Follicles (b) Ovulation (c) 28 days (d) Conception (or Pregnancy) (e) About nine months (f) Menstruation (g) Hormones

Question. In the surgical method of birth control available for males, the structures A in the reproductive system are cut and ligated (tied up) at both ends. This prevents the reproductive cells B from coming out from the organs C where they are made in the male body. Since B cannot come out from the male body, they cannot fuse with cell D in the body of a female and hence pregnancy is prevented.
(a) What are structures A ?
(b) What are cells B ?
(c) Name the organs C.
(d) What is cell D ?
(e) What is the name of this surgical procedure for birth control available to males ?
Answer : (a) Sperm ducts (or Vas deferens) (b) Sperms (c) Testes (d) Egg cell (or Ovum) (e) Vasectomy

Question. In the surgical method of birth control available for human females, the structures P in the reproductive system are cut and ligated (tied up) properly at both ends. This prevents the reproductive cell Q released by an organ R from entering the structures P so that Q is not available to fuse with another reproductive cell S coming from the male reproductive system. In this way, pregnancy is prevented.
(a) What are structures P ?
(b) What is cell Q ?
(c) Name the organ R.
(d) What is the reproductive cell S ?
(e) What is the name of this surgical method of birth control available to females ?
Answer : (a) Oviducts (or Fallopian tubes) (b) Ovum (or Egg cell) (c) Ovary (d) Sperms (e) Tubectomy

Question. The human males use a device X made of a very thin rubber sheet as a covering on the male organ to prevent pregnancy. This device traps the gametes Y in it. In order to prevent pregnancy, the human females use a device Z which is a circle of rubber with a metal spring around it. The device Z is put inside the vagina to cover the cervix. It stops Y from going into the uterus.
(a) What is device X ?
(b) What are Y ?
(c) Name the device Z.
(d) What is the general name of these methods of birth control (or preventing pregnancy) ?
(e) The use of which contraceptive device, X or Z, can protect the persons from sexually transmitted diseases ?
Answer : (a) Condom (b) Sperms (c) Diaphragm (or Cap) (d) Barrier methods (e) X

Question. A woman uses pills A as a method of birth control (or preventing pregnancy). The pills A stop the ovaries from releasing ovum into oviducts. Another woman uses pills B as a method of birth control. The pills B kill the sperms and prevent pregnancy.
(a) What do the pills A contain ?
(b) What is the common name of pills A ?
(c) What do the pills B contain ?
(d) What is the common name of pills B ?
(e) What is the general name of these methods of birth control ?
Answer : (a) Hormones (b) Oral pills (c) Spermicides (d) Vaginal pills (e) Chemical methods

Question. A woman uses a device X made of a common metal for preventing pregnancy. This device works by preventing the implantation of fertilised egg cell (or embryo) in the female organ Y.
(a) What are the two names of device X ?
(b) Name the organ Y.
(c) Can this method of contraception protect a woman from acquiring a STD ?
Answer : a) Copper-T and IUCD (b) Uterus (or Womb) (c) No

Question. A, B and C are three common STDs. A and C are caused by bacteria whereas B is caused by a virus D. The virus D reduces the immunity of the infected person to such a low level that the person can die of even very mild diseases.
(a) What could A and C be ?
(b) What is B ?
(c) Name the virus D ?
(d) How can A, B and C be caused ?
(e) Out of A, B and C, which one does not have a definite cure as yet ?
Answer : (a) Syphilis and Gonorrhoea (b) AIDS (c) HIV (d) By sexual contact with an infected person (e) B (AIDS)

Question. The germ cell A produced by a person X is round in shape and it fuses with another germ cell B having a long tail and produced by a person Y. The fusion of A and B produces a new cell C. The cell C divides repeatedly and grows inside the organ D of person X to form E in which the body features of the unborn baby are not much developed. E grows further to form F in which the various body features of the unborn baby (like hands, legs, head, eyes, and ears, etc.) can be identified. F grows further and ultimately forms a baby. What are A, B, C, D, E and F ? Out of the two persons X and Y, which one is male and which one female ?
Answer : A is ovum (or egg cell); B is sperm ; C is zygote (fertilised egg) ; D is uterus ; E is embryo ; F is foetus; Y is male ;X is female

Question. Explain why, a human zygote is more likely to grow into an adult than a frog zygote.
Answer : The human zygote grows inside the uterus of mother so it can grow safely into an adult.
On the other hand , a frog zygote grows in the water of pond or stream where it is very unsafe because it may be eaten up by other aquatic animals

Question. In a bisexual flower, inspite of the young stamens being removed artificially, the flower produces fruit. Explain.
Answer : Though stamens have been removed but the female organ ‘carpel’ of the flower is intact. Cross-pollination has occurred in this flower leading to the formation of fruit

Question. In what ways is fertilisation in a plant :
(a) similar to fertilisation in a human ?
(b) different from fertilisation in a human ?
Answer : (a) Similarities : (i) The fusion of gametes occurs in the female part in a plant as well as in a human (ii) the male gamete moves (or is moved) to the female gamete in a plant as well as in a human (iii) A zygote is produced which develops into an embryo in a plant as well as in a human (b) Differences :
(i) There is pollination in a plant but copulation ( or mating) in a human to bring the male and female gametes together (ii) There is no equivalent in a plant to the oviducts in a human (iii) In a human, the male gametes (sperms) swim but in a plant self-fertilisation is possible (The fertilisation of a plant with its own pollen is called self-fertilisation)

Diagram Based Questions:

1. Read the following and answer any four questions from (1) to (v) given below:
Cross pollination is the transfer of pollen grains from one flower to the stigma of a genetically different flower. It is performed with the help of an external agency which may be abiotic (Eg., wind, water) or biotic (eg.; insects, birds, bats, snails). The diagram shows the carpel of an insect pollinated flower.

Question. Out of the following characters which one is not applicable for wind pollination
(a) Stamen hang out of the flowers exposing the anthers to the wind
(b) the pollen grains are tiny and light
(c) the flowers are nectar less
(d) the petals are brightly coloured

Answer : D

Question. How many of the above characteristics are of insect pollinated flower
(a) 1
(b) 2
(c) 3
(d) 4

Answer : A

Question. Pollen kit is generally found in
(a) anemophilous flowers
(b) Entomophilous flowers
(c) ornithophilous flowers
(d) malacophilous flowers

Answer : B

Question. The given diagram shows the carpel of an insect pollinated flower. What is the most likely reason for the non-germination of pollen grain Z?
(a) Pollen grains X and Y were brought to the stigma earlier, therefore, their germination inhibited the germination of pollen grain Z.
(b) Pollen grain Z was brought to the flower by wind, while pollen grains X and Y were brought to the flower by insects.
(c) Pollen grain Z lacks protrusions that allow it to adhere properly onto the stigma surface.
(d) Pollen grain Z comes from a flower of an incompatible species.

Answer : D

Question. Pollination by insect is called
(a) entomophily
(b) chiropterophily
(c) anemophily
(d) ornithophily

Answer : A

Question. 

The diagram of an angiosperm ovule is presented above.

Question. Give the technical term for ovule.
Answer : Megasporangium

Question. forms the test a of seed.
Answer : E – Outer Integument

Question. represents the basal part of the ovule.
Answer : A – Chalaza

Question. represents the female gametophyte.
Answer : C – Embryo Sac

(b) Identify and name the part that

Question. attaches the ovule to the placenta
Answer : F – Hilum

Question. remains as perisperm in some seeds.
Answer : D – Nucellu

1. Apomixis is a type of reproduction that results is the development of a/an_______________________.

2. Why apple is called a false fruit. Which part of plant forms the fruit?

3. What are cleistogamous flowers? Can cross – pollination occurs in cleistogamous flowers. Give reason?

4. Mention the scientific term for the type of pollination which ensures Genetic Recombination.

5. List any three differences between wind pollinated flower & insect – pollinated flower.

6. What relationship exists between a species of moth and Yucca plant?

7. Enlist the advantages offered by seeds to angiosperms.

8. Why is emasculation done in the process of hybridization?

9. What is triple fusion? Where does it occur?

10. What is perisperm. Name two plants in which perisperm is present.

 Unit VI- Reproduction

Chapter 2
Sexual Reproduction in Flowering Plants
Significance of seed and fruit formation

Significance of fruit formation
The fruits protect the seeds from unfavorable climatic conditions. Both fleshy and dry fruits help in the dispersal of seeds to distant places. They are a source of many chemicals like sugars, protein, oil, organic acids, vitamins and minerals. Some fruits may provide nutrition to the developing seedlings. Generally hard seeds are surrounded by soft fleshy fruit pericarp ( for example guava) and soft seeds by a hard fruit shell (for example almond). The fleshy, edible parts of the fruit become the source of food and energy for the animals which often act as dispersal agents.

Polygenic Inheritance

Galton in 1883 suggested that many instances of continuous variation are heritable. He was impressed by the fact that taller human beings generally produce taller children. He suggested that characters such as height and mental capabilities in humans are heritable although these show a continuous range of variation in a population. Galton’s postulate gained experimental support when it was found that at least in some instances the same character can be determined by more than one gene, each with the same but cumulative phenotypic effect Quantitative characters like plant height, yield of crops (size, shape and number of seeds and fruits per plant), intelligence in human beings and milk yield in animals have been found to be determined by many genes and their effects have been found to be cumulative. Each gene has a certain amount of effect, and the more the number of dominant genes, the greater expression of the character. Quantitative inheritance is also known as polygenic inheritance or multiple factor inheritance. Though polygenic traits can be easily influenced by environment, these are generally controlled by three or more genes with phenotype reflecting the contribution of each allele (Quantitative). Let us discuss the polygenic trait by studying the inheritance of human skin colour. There are no contrasting phenotypes for this trait. Let us assume that this trait is controlled by three genes A, B, and C. in this cross, there is a mating between dark-skinned and fair-skinned human beings and then the intermediate skin coloured individuals expected at F1 are mated to obtain F2 progeny.

Polygenic inherence

(a) A cross depicting the inheritance of human skin colour controlled by polygenes.
(b) In the relative frequency of F2 progeny in a polygenic cross is plotted against the extent of phenotypic expression – a typical inverted bell shaped curve is seen.
It is clear that:-
(i) Few individuals fall into parental categories;
(ii) The expression level of the phenotype is dependent upon the number of contributive alleles and is hence more quantitative.

If the F2 data are plotted graphically, a bell-shaped curve results.
In this example, we have assumed the involvement of three gene pairs, However if higher number of genes are involved in determining a phenotype, greater variety would be expected in F2generation.

Other examples that can be studied are the kernel colour in wheat and inheritance of cob length in maize. It is generally believed that during evolution there was duplication of chromosome or chromosome parts thereby leading to multiple copies of the same gene. A large number of characters are controlled by polygenes in which alleles contribute additively to a phenotype. This results in polygenic inheritance.