Class 12 Biology Chapter 1- Reproduction in Lower and Higher Plants

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1. Insect pollinated flowers usually posses …………….
 a. Sticky pollens with rough surface 
 b. Large quantities of pollens
 c. Dry pollens with smooth surface 
 d. Light coloured pollens

2. In ovule, meiosis occurs in ……….
 a. Integument 
 b. Nucellus
 c. Megaspore 
 d. Megaspore mother cell

3. The ploidy level is NOT the same in ……
a. Integuments and nucellus
b. Root tip and shoot tip
c. Secondary nucleus and endosperm
d. Antipodals and synergids

4. Which of the following types require pollinator but result is genetically similar to autogamy?
a. Geitonogamy 
b. Xenogamy
c. Apogamy 
d. Cleistogamy

5. If diploid chromosome number in a flowering plant is 12, then which one of the following will have 6 chromosomes?

a. Endosperm 
b. Leaf cells
c. Cotyledons 
d. Synergids

6. In angiosperms, endosperm is formed by/ due to ……….
a. Free nuclear divisions of megaspore
b. polar nuclei
c. polar nuclei and male gamete
d. synergids and male gamete

7. Point out the odd one ……….
a. Nucellus 
b. Embryo sa
c. Micropyle 
d. Pollen grain

Q.2 : Very Short Answer Questions

1. Name the part of gynoecium that determine the compatible nature of pollen grains.
Answer : Stigma is the part of gynoecium which determine the compatible nature of pollen grains.

2. How many haploid cells are present in a mature embryo ?
AnswerThere are 6 haploid cells nd 2 nucleic cells are present in an embryo

3. Even though each pollen grain has 2 male gametes, why atleast 20 pollen grains are required to fertilize 20 ovules in a particular carpel?
Answer : Even though 2 male gametes are there in one pollen grain, 20 pollen grains are required to fertilise 20 ovules. This is due to the presence of double fertilization in angiosperms. For one Zygote to form, One male and one egg is required. The other male gamete fuses with the polar nuclei and forms the primary endosperm nucleus (PEN).

4. Define megasporogenesis.
Answer : Formation of megaspores from megaspore mother cell called megasporogenesis. It occurs inside the nucellus of ovule of angiosperm. The process begins very early then nucellus is not completely surrounded by the integuments.

5. What is hydrophily ?
Answer : Transfer of pollen grains from anther to the stigma through the water is called as hydrophily.

6. Name the layer which supplies nourishment to the developing pollen grains.
Answer : The tapetum is the inner most layer of the microsporangial wall that secretes precursors of sporopollenin which in turn forms sporopollenin as well as provides nourishment to the developing pollen grains.

7. Define parthenocarpy.
Answer : Parthenocarpy is the development of fruit without the formation of seeds due to lack of pollination, fertilization and embryo development.

8. Are pollination and fertilization
necessary in apomixis ?
Answer: Apomixis or Agamospermy involves formation of embryos and seeds by asexual methods without involving meiotic gametogenesis and sexual fusion of gametes. Pollination and fertilization are not necessary in apomixis.

9. Name the parts of pistil which develop
into fruits and seeds.
Answer : pistil has three parts , i.e., stigma (receives pollen), which grows down through style to ovary. Ovary contains ovules, which contain an egg. The ovary develops into the fruit and ovule develops into a seeds

10. What is the function of filiform apparatus ?

Answer : The function of filiform apparatus is to guide entry of pollen tube and release of sperm cells. 

Filiform apparatus : The synergid cell wall forming an extremely thick structure at the micropylar end is called the filiform apparatus. It bears several finger-like projections into the structure of synergid cytoplasm

Q.3 Short answer questions

1. How polyembryony can be commercially exploited ?

Answer Polyembryony may be defined as the occurrence of two or more embryos in one ovule which consequently results in the emergence of multiple seedlings. 
» It Can be commercially exploited by various ways like 
» It can use for disease free plant .
» It can used in horticulture.
» can be used in clones formation.

2. Pollination and seeds formation are very crucial for the fruit formation. Justify the statement.

Answer : pollination and seed formation is very crucial in fruit formation  because 
Seeds and fruits are formed by fertilization. For fertilization pollination is must. In angiosperms, two structures are formed as a result of double fertilization – a diploid zygote and a triploid primary endosperm cell. The zygote develops into an embryo, whereas, the endosperm cell gives rise to endosperm. It provides nourishment to the growing embryo. Both fruits and seeds are an important part of angiosperms.

3. Incompatibility is a natural barrier in the fusion of gametes. How will you explain this statement?

AnswerIn gametic incompatibility, if the sperm and ova are from different species then they do not recognize each other and hence do not fuse to form the zygote. Hence, incompatibility act as a natural barrier for fusion of gametes to prevent reproduction between individuals of different species.

4. Describe three devices by which cross pollination is encouraged in Angiosperms by avoiding self pollination.
Answer Three outbreeding devices that flowering plants have developed:

1. Self-incompatibility: A genetic method to prevent pollens from fertilizing ovules of the same flower by inhibiting their germination on stigma or pistil.

2. Production of unisexual flowers: So that the male and female parts will be present on different plants i.e., dioecious or on different flowers in the same plant (monoecious). This prevents both autogamy and geitonogamy. 

Q. 4 : Long Answers Questions

1. Describe the process of double fertilization.
Answer :

 The process of fusion of male gamete with the female gamete to form the diploid zygote (2n) is known as fertilisation. The fusion of one male gamete with egg and that of another male gamete with a secondary nucleus is called double fertilisation. It is the characteristic feature of only angiosperms. All angiosperms are characterised by a unique process called double fertilisation. Double fertilisation is significant because it involves the use of both the male gametes produced by a pollen grain. This avoids the chances of polyembryony and increases the chances of survival of the future plant. It consists of two fusions and results in the formation of two products. First fertilisation restores diploidy in the life cycle. The diploid zygote develops into an embryo which subsequently develops into a new plant. Second fertilisation product, triploid PEN (Primary endosperm nucleus) develops to form a nutritive tissue called endosperm for developing an embryo.

2. Explain the stages involved in the maturation of microspore into male gametophyte.
Answer :

 Formation of the male gametophyte in flowering plants takes place within specialized male reproductive organs called the stamens. During microsporogenesis, diploid pollen mother cells undergo meiotic division to produce tetrads of haploid microspores. This stage is completed when distinct unicellular microspores are released from the tetrad by the activity of a mixture of enzymes secreted by the tapetum, the inner nutritive layer of the stamen. This results into production of the sperm cell.

Pollen grain marks the begining of male gametophyte. It undergoes first mitotic division to produce bigger, naked vegetative cell and small, thin walled generative cell. The vegetative cell is rich in food and having irregular shaped nucleus. The generative cell floats in the cytoplasm of vegetative cell.

The second mitotic division is concerned with generative cell only and gives rise to two non-motile male gametes. The mitotic division of generative cell takes place either in pollen grain or in the pollen tube. The pollen grains are shed from the anther, at this two- celled stage in most of the angiosperms.

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