CBSE 12th Standard Biology Subject Sexual Reproduction in Flowering Plants Case Study Questions With Solution 2021
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CBSE 12th Standard Biology Subject Sexual Reproduction in Flowering Plants Case Study Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Biology
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Read the following and answer any four questions from (i) to (v) given below:
Cross pollination is the transfer-of pollen grains from the anther of a one flower to the stigma of a genetically different flower. It is performed with the help of an external agency which may be abiotic (e.g., wind, water) or biotic (e.g., insects, birds, bats, snails). The diagram shows the carpel of an insect pollinated flower.
(i) What is the most likely reason for 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 broughtto the flower by insect
(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
(ii) Which of the following best describes the function of the pollen tube?
(a) It acts as a conduit to transport male gametes from the anther to the ovule
(b) It acts as a conduit to transport male gametes from the stigma to the ovule.
(c) It contains key nutrients that serve to nourish the newly-formed zygote
(d) It digests the tissues of the stigma, style and ovary.
(iii) Pollination of a flower in which the pollen is carried by an insect is called(a) anemophily (b) ornithophily (c) entomophily (d) malacophily. (iv) Refer to the given characteristics of some flowers:
A. The stamens hang out of the flower, exposing the anthers to the wind. B. The pollen grains are tiny and light C. The flower has a sweet scent. D. The flower petals are brightly coloured. How many of the above characteristics are of insect-pollinated flower?
(a) One (b) Two (c) Three (d) Four (v) Pollenkitt is generally found in
(a) anemophilous flowers (b) entomophilous flowers (c) ornithophilous flowers (d) malacophilous flowers. -
Read the following and answer any four questions from (i) to (v) given below:
In angiosperms, the pollen grains are being transferred from the anther to the stigma and is termed pollination. This phenomenon was first discovered by Camerarius (1694) in the end of seventeenth century. Pollen grains are immobile. They cannot reach the stigma by themselves. An external agent is required for this. The pollination is mainly of two types-self pollination and cross pollination.
The diagram given below shows two plants of the same species showing different types of pollination.
(i) What is transferred between the plants in the process indicated by arrow P?(a) Ova (b) Pollen (c) Nutrients (d) Seeds (ii) Which of the following statements is correct regarding processes P,Q and R?
(a) Processes P, Q and R introduce genetic variability in the offspring of sexually reproducing plants X andY.
(b) Wind serves as agent for process Q if plants X and Y belong to Genus Salvia.
(c) Flowers of plants X and Y need to produce odour and nectar for completion of processes P and Q if they-are entomophilous.
(d) If plants X and Y belong to Genus Cannabis, then their flowers need to produce sticky and heavy pollens in very small amount for accomplishment of process Q.(iii) Identify the processes P,Q and R.
P Q R (a) Geitonogamy Xenogamy Autogamy (b) Allogamy Chasmogamy Cleistogamy (c) Autogamy Geitonogamy Xenogamy (d) Geitonogamy Allogamy Autogamy (iv) In Catharanthus, the growth of style brings the stigma in contact of ripe anthers present on the mouth of corolla tube. This is an example of
(a) homogamy (b) cleistogamy (c) geitonogamy (d) xenogamy. (v) Which of the given processes represents a type of pollination that would result in greater adaptability of the particular species to potential environmental changes?
(a) P (b) Q (c) R (d) All of these -
Read the following and answer any four questions from (i) to (v) given below:
The endosperm makes the main source of food for the embryo. Generally the endosperm nucleus divides after the division of the oospore, but in several cases the endosperm is formed to a great extent even before the first division of the oospore. There are three general types of endosperm formation: (a) nuclear type, (b) cellular type and (c) helobial type. The endosperm is usually triploid but haploid endosperm is also found. Endosperm may either be completely consumed by the developing embryo before seed maturation or it may persist in the mature seed.
(i) Haploid endosperm is found in(a) Pinus (b) cauliflower (c) sunflower (d) pea (ii) Persistent endosperm is found in
P. Pea Q. Castor R. Bean S. Coconut T. Groundnut(a) Q and S (b) P and T (c) R, S and T (d) P, S and T (iii) Milk of tender coconut represents.(i) and the surrounding white coconut meal represents (ii).
(I) (ii) (a) cellular endosperm free-nuclear endosperm (b) free-nuclear endosperm cellular endosperm (c) helobial endosperm cellular endosperm (d) free-nuclear endosperm helobial endosperm (iv) If an endosperm cell of a gymnosperm contains 12 chromosomes, the number of chromosomes in each cell of the root will be
a) 4 (b) 24 (c) 16 (d) 6 (v) In angiosperms, normally after fertilisation
(a) the zygote divides earlier than the primary endosperm nucleus (b) the primary endosperm nucleus divides earlier than the zygote (c) both the zygote and primary endosperm nucleus divide simultaneously (d) both the zygote and primary endosperm nucleus undergo a resting period. -
Read the following and answer any four questions from (i) to (v) given below:
Embryo develops at the micropylar end of the embryo sac where the zygote is situated. Most zygotes divided only after certain amount of endosperm is formed. The early stages of embryo development are similar in both monocotyledons and dicotyledons. The zygote gives rise to the proembryo and subsequently to the globular heart-shaped and mature embryo. A typical dicotyledonous embryo consists of an embryonal axis and two cotyledons. Embryo of monocotyledons possess only one cotyledon.
(i) True embryo develops as a result of fusion of(a) two polar nuclei of embryo sac (b) an egg cell and a male gamete (c) synergid and male gamete (d) a male gamete and antipodals (ii) Refer to the given diagram of the embryo of an angiospermous plant with parts labelled P, Q and R. Select the correct statement(s) regarding this.
(i) Part 'P' supplies nutrition to the developing embryo.
(ii) Part 'Q' is the protective sheath of radicle and root cap.
(iii) Part 'R' is the protective sheath of shoot apex and leaf primordia.
(iv) The embryo shown in the diagram is present in members of Family Poaceae.(a) (iv) only (b) (ii) and (iii) only (c) (i) and (iv) only (d) (i), (ii), (iii) and (iv) (iii) Which of the given statements are true?
(i) During the development of a dicot embryo, heart-shaped embryo is followed by globular embryo.
(ii) The part of embryonal axis above-the level of cotyledons is epicotyl, while the part below the level of cotyledons is hypocotyl.
(iii) Monocot seeds possess a single cotyledon represented by scutellum.(a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iii) (d) (i), (ii) and (iii) (iv) Consider the following parts of an embryonal axis of a dicot seed.
(i) Hypocotyl (ii) Epicotyl (iii) Radicle (iv) Plumule
In which of the following the above parts are correctly arranged from top to base?(a) (iii) \(\to \) (i) \(\to \) (ii) \(\to \) (iv). (b) (ii) \(\to \) (i) \(\to \) (iii) \(\to \) (iv) (c) (iv)\(\to \) (ii) \(\to \) (i) \(\to \) (iii) (d) (iii) \(\to \) (iv) \(\to \) (ii) \(\to \) (i) (v) In grass family, the cotyledon is called
(a) epiblast (b) plumule (c) scutellum (d) perisperm -
Read the following and answer any four questions from (v) to (v) given below:
A typical angiospermic ovule is a small structure attached to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is formed. Mature ovules are classified on the basis of funiculus. It can be orthotropous, anatropous, hemitropous, campylotropous, etc.
(i) The body of the ovule consists of a mass of parenchymatous cells called(a) integuments (b) nucellus (c) hilum (d) funiculus (ii) Refer to the given figure and select the correct statement regarding it.
(a) This type of ovule is found in cactus.
(b) The micropyle comes to lie close to the funiculus due to unilateral growth of ovule.
(c) It is most common type of ovule found in the members of Chenopodiaceae
(d) It is half inverted ovule.(iii) Identify the parts labelled as A, B, Cand D in the given figure and select the correct option
A B C D (a) Chalaza Female gametophyte Embryo sac Micropyle (b) Chalaza Nucellus Embryo sac Micropyle (c) Micropyle Egg Embryo sac Chalaza (d) Micropyle Nucellus Embryo sac Chalaza (iv) Mature ovules are classified on the basis of funiculus. If micropyle lie close to the funiculus, the ovule is termed as
(a) orthotropous (b) anatropous (c) hemitropous (d) campylotropous (v) In Asphodelus, ovule is
(a) unitegmic (b) tritegmic (c) bitegmic (d) ategmic
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CBSE 12th Standard Biology Subject Sexual Reproduction in Flowering Plants Case Study Questions With Solution 2021 Answer Keys
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(i) (d): Pollen grains can only germinate if the pollen grain and style tissues are compatible, i.e., of the same or closely related species. Pollen grains X and Y must have come from a compatible species.
(ii) (b)
(iii) (c) : Entomophily is the type of pollination that takes place through the agency of insects. The insectloving flower possesses various adaptations by which they attract insects and use them as carrier of pollen grains for the purpose of cross pollination.
(iv) (b) : Insect-pollinated flowers produce nectar, which attract the pollinators for feeding. Some flowers produce edible pollen grains. Flowers are fragrant and emit scent and odour. These are brightly coloured. The pollen grains are spiny, heavy and surrounded by a yellow sticky substance called pollenkitt.
(v) (b) : Insect-pollinated flowers produce nectar, which attract the pollinators for feeding. Some flowers produce edible pollen grains. Flowers are fragrant and emit scent and odour. These are brightly coloured. The pollen grains are spiny, heavy and surrounded by a yellow sticky substance called pollenkitt. -
(i) (b)
(ii) (c) : In the given figure, processes P, Q and R represent geitonogamy (self pollination), xenogamy (cross pollination) and autogamy (self pollination), respectively. Pollinating agents are required for accomplishment of processes P and Q but no agent is required for process R. Out of P, Q and R, only Q is responsible for introducing genetic variability as it is cross pollination between different plants of same species. Salvia is insect pollinated whereas Cannabis is wind pollinated plant.
(iii) (a) : In the given figure, processes P, Q and R represent geitonogamy (self pollination), xenogamy (cross pollination) and autogamy (self pollination), respectively. Pollinating agents are required for accomplishment of processes P and Q but no agent is required for process R. Out of P, Q and R, only Q is responsible for introducing genetic variability as it is cross pollination between different plants of same species. Salvia is insect pollinated whereas Cannabis is wind pollinated plant.
(iv) (a) : Homogamy occur in chasmogamous or open flowers where anthers and stigmas are brought together by growth, bending or folding.
(v) (b) -
(i) (a) : In gymnosperms, the endosperm is haploid (n) and forms a continuation of the female gametophyte.
(ii) (a) : In some seeds, the endosperm persists in the seed as food storage tissue. Such seeds are called endospermic or albuminous, e.g., castor, maize, wheat, barley, rubber and coconut.
(iii) (b): In coconut (Cocos nucifera), the surrounding white kernel called coconut meal is cellular endosperm and the coconut water (also called coconut milk) in the centre is free nuclear endosperm made up of thousands of nuclei.
(iv) (b) : The endosperm of a gymnosperm is haploid (n), while the cells of the root are diploid (2n). So, the number of chromosomes in the root will be 24.
(v) (b) -
(i) (b) : In double fertilisation, out of the two male gametes one fuses with egg or oosphere to perform generative fertilisation. Generative fertilisation is also called syngamy or true fertilisation. It gives rise to a diploid zygote or oospore.
(ii) (c)
(iii) (b) : During the development of dicot embryo, initially the dicot embryo is globular and undifferentiated. Early embryo with radial symmetry is called pro embryo. It is transformed into embryo with the development of radicle, plumule and cotyledons. Two cotyledons differentiate from the sides with a faint plumule in the centre. At this time the embryo becomes heart-shaped.
(iv) (c)
(v) (c): In the grass family, the cotyledon is called scutellum that is situated towards one side (lateral) of the embryonal axis. -
(i) (b)
(ii) (a) : The given figure is of circinotropous ovule where funiculus coiled around the ovule. It is found in the Family Cactaceae.
(iii) (d) : Given figure represents an anatropous ovule where· A, B, C and D represent micropyle, nucellus, embryo sac and chalaza respectively.
(iv) (b) : Depending upon the configuration and orientation of the body of ovule in relation to funiculus, there are six types of ovule - orthotropous (atropous, erect), anatropous (inverted), hemitropous (half inverted), campylotropous (body curved), amphitropous (both body and embryo sac curved) and circinotropous (funiculus coiled around the ovule). Anatropous or inverted ovule is the most common type of ovule found in angiosperms (in 80% of angiosperm families). Here, body of the ovule gets inverted and micropyle is on lower side. Further micropyle and funiculus lie side by side and micropyle is close to hilum.
(v) (b)
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