12th Bio - Botany - Book Back Answers - Chapter 1 - English Medium Guides

 

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Tamil Nadu Board 12th Standard Bio-Botany - Chapter 1: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Chapter 1 – Bio-Botany from the Tamil Nadu State Board 12th Standard Bio-Botany textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Bio-Botany Chapter 1 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 12 students! Prepare well and aim for top scores. Thank you!

Unit 1 - Asexual and Sexual Reproduction in plants

I. Multiple Choice Questions

1. Choose the correct statement from the following
a) Gametes are involved in asexual reproduction
b) Bacteria reproduce asexually by budding
c) Conidia formation is a method of sexual reproduction
d) Yeast reproduce by budding
Answer Key:
d) Yeast reproduce by budding

 
2. An eminent Indian embryologist is
a) S.R.Kashyap
b) P.Maheswari
c) M.S. Swaminathan
d) K.C.Mehta
Answer Key:
b) P.Maheswari

 
3. Identify the correctly matched pair
a) Tuber - Allium cepa
b) Sucker - Pistia
c) Rhizome - Musa
d) Stolon – Zingiber
Answer Key:
c) Rhizome - Musa 

 
4. Size of pollen grain in Myosotis
a) 10 micrometer
b) 20 micrometer
c) 200 micrometer
d) 2000 micrometer
Answer Key:
a) 10 micrometer 

 
5. First cell of male gametophyte in angiosperm is
a) Microscope
b) megaspore
c) Nucleus
d) Primary Endosperm Nucleus
Answer Key:
a) Microscope

 
6. Match the following
I) External fertilization i) pollen grain
II) Androecium ii)anther wall
III) Male gametophyte iii)algae
IV) Primary parietal layer iv)stamens
a)I-iv;II-i;III-ii;IV-iii
b)I-iii;II-iv;III-i;IV-ii
c)I-iii;II-iv;III-ii,IV-i
d)I-iii;II-i;III-iv;IV-ii
Answer Key:
b)I-iii;II-iv;III-i;IV-ii 

 
7. Arrange the layers of anther wall from locus to periphery
a) Epidermis,middle layers, tapetum, endothecium
b) Tapetum, middle layers, epidermis, endothecium
c) Endothecium, epidermis, middle layers, tapetum
d) Tapetum, middle layers endothecium epidermis
Answer Key:
d) Tapetum, middle layers endothecium epidermis

 
8. Identify the incorrect pair
a) sporopollenin - exine of pollen grain
b) tapetum – nutritive tissue for developing microspores
c) Nucellus – nutritive tissue for developing embryo
d) obturator – directs the pollen tube into micropyle
Answer Key:

c) Nucellus – nutritive tissue for developing embryo 

9. Assertion : Sporopollenin preserves pollen in fossil deposits
Reason : Sporopollenin is resistant to physical and biological decomposition
a) assertion is true; reason is false
b) assertion is false; reason is true
c) Both Assertion and reason are not true
d) Both Assertion and reason are true.
Answer Key:
d) Both Assertion and reason are true. 

 
10. Choose the correct statement(s) about tenuinucellate ovule
a) Sporogenous cell is hypodermal
b) Ovules have fairly large nucellus
c) sporogenous cell is epidermal
d) ovules have single layer of nucellus tissue
Answer Key:
a) Sporogenous cell is hypodermal 

 
11. Which of the following represent megagametophyte
a) Ovule
b)Embryo sac
c)Nucellus
d)Endosperm
Answer Key:

b)Embryo sac

 
12. In Haplopappus gracilis, number of chromosomes in cells of nucellus is 4. What will be the chromosome number in Primary endosperm cell?
a) 8
b) 12
c) 6
d) 2
Answer Key:
c) 6 

 
13. Transmitting tissue is found in
a) Micropylar region of ovule
b) Pollen tube wall
c) Stylar region of gynoecium
d) Integument
Answer Key:
c) Stylar region of gynoecium

 
14. The scar left by funiculus in the seed is
a) tegmen
b) radicle
c) epicotyl
d) hilum
Answer Key:
d) hilum

 
15. A Plant called X possesses small flower with reduced perianth and versatile anther. The probable agent for pollination would be
a) water
b) air
c) butterflies
d) beetles
Answer Key:
b) air

 
16. Consider the following statement(s)
i) In Protandrous flowers pistil matures earlier
ii) In Protogynous flowers pistil matures earlier
iii) Herkogamy is noticed in unisexual flowers
iv) Distyly is present in Primula
a) i and ii are correct
b) ii and iv are correct
c) ii and iii are correct
d) i and iv are correct

Answer Key:

b) ii and iv are correct  

 
17. Coelorhiza is found in
a)Paddy
b)Bean
c)Pea
d)Tridax
Answer Key:
a)Paddy 

 
18. Parthenocarpic fruits lack
a)Endocarp
b)Epicarp
c)Mesocarp
d) seed
Answer Key:
d) seed

 
19. In majority of plants pollen is liberated at
a) 1 celled stage
b) 2 celled stage
c) 3 celled stage
d) 4 celled stage
Answer Key:

b) 2 celled stage 

 

II. Short Answer Questions

1. What is reproduction?

• Reproduction is the biological processes by which new individual organisms- off springs are produced from their parent or parents.

 

2. List out two sub-aerial stem modifications with example.

• 1.Runner - Centella asiatica
• 2.Offset - Pistia, and Eichhornia
• 3.Stolon - Dioscorea and Agave
• 4.Sucker – Chrysanthemum

 

3. What is layering?

• The stem of a parent plant is allowed to develop roots while still intact. 
• The root develops, the rooted part is cut and planted to grow as a new plant. 
• Examples: Ixora and Jasminum. 
• Types: Mound layering and Air layering

4. What are clones?

• Morphologically and genetically identical individuals are formed by asexual methods are called clones.

 

5. A detached leaf of Bryophyllum produces new plants. How?

• In Bryophyllum, Adventious buds develop at the notches on its leaf margin. 
• These are called epiphyllous buds.
• They develop into new plants forming a root system.
• They become independent plants when the leaf gets decayed.

 

6. Differentiate Grafting and Layering.

Grafting	Layering
There is a fusion between tissues of different plants	There is no fusion between tissues of different plants
Stock plant contains a very strong root system.	Roots are formed on a stem of a mother plant
Types: 1.Bud grafting, 2. Approach grafting, 3. Tongue grafting, 4.Crown grafting and 5.Wedge grafting.	Types: 1.Mound layering 2.Air layering are

  

7. "Tissue culture is the best method for propagating rare and endangered plant species"- Discuss.

• Tissue culture is the best method used for large scale multiplication to develop better variety plants to save endangered species of plants.

 

8. Distinguish mound layering and air layering.

Mound layering	Air layering
Applied for the plants having flexible branches	The stern is girdled at nodal region.
The lower branch with leaves is bent to the ground	Hormones are applied to girdled region
The part of the stem is buried in the soil	Girdled portion is covered with damp soil
Roots emerge in buried part of the stem	Roots emerge in these branch

  

9. Explain the conventional methods adopted in vegetative propagation of higher plants.
1. Cutting: 

• Producing a new plant by cutting the plant parts. (root, stem and leaf), 
• The cut part is placed in a suitable medium. 
• It produces root and grows into a new plant. 
• Example:1. Root cutting (Malus),
• 2.Stem cutting (Hibiscus, Bougainvillea and Moringa)
• 3.Leaf cutting (Begonia, Bryophyllum).

2. Grafting:

• The parts of two different plants are joined and they continue to grow as one plant.
• The plant which is in contact with the soil is called stock.
• The plant used for grafting is called scion.
• Example: Citrus, Mango and Apple. 
• They are 5 Types 
• i). bud grafting, 
• ii). approach grafting, 
• iii). tongue grafting, 
• iv). crown grafting and 
• v). wedge grafting.

3. Layering: 

• The stem of a parent plant is allowed to develop roots while still intact. 
• When root develops, the rooted part is cut and planted to grow as a new plant.
• Example: Ixora and Jasminum. 
• Types: Mound layering and Air layering

 

10. What is Cantharophily.

• Pollination by beetle is called Cantharophily 

 

11. List any two strategy adopted by bisexual flowers to prevent self-pollination.
The special adaptations of the bisexual flowers prevents self-pollination.
1. Dichogamy: 

• In bisexual flowers anthers and stigmas mature at different times.
• a. Protandry: The stamens mature earlier than the stigmas of the flowers.
• b. Protogyny: The stigmas mature earlier than the stamens of the flower

2. Herkogamy: 

• In bisexual flowers, the stamens and stigmas, are arranged different positions.
• a. style is reflexed away from the stamens
• b. stigmas project far above the stamens

 

12. What is endothelium ?

• The inner layer of the integument may become
• specialized to perform the nutritive function for the embryo sac and is called as endothelium or
• integumentary tapetum. Ex: Asteraceae. 

 

13. "The endosperm of angiosperm is different from gymnosperm". Do you agree. Justify your answer.

• Yes I agreed. 
• The endosperm of angiosperm is triploid. 
• But in gymnosperm is haploid

 

14. Define the term Diplosporу.

• A diplold embryo sac Is formed from megaspore mother cell without a regular meiotic division is called Diplospory. 
• It also called Generative apospory
• Ex. Eupatorium and Aerva.  

 

15. What is polyembryony? How it can commercially exploited.

• The occurrence of more than one embryo in a seed is called polyembryony.
• Embryos developed through polyembryony are found virus free.
• The seedlings formed from nuclear tissue in citrus are found on better clones for orchards. 

 

16. Why does the zygote divide only after the division of Primary endosperm cell?

• The Zygote needs nourishment during its development.
• Fertilized embryo sac offers little nourishment to the Zygote.
• The primary endosperm cell divides and generates endosperm tissue.
• This nourishes the Zygote. So, the Zygote divides after the primary Endosperm cell.

 
17. What is Mellitophily?

• Pollination carried out by Bees is said to be mellitophily.

 
18. “Endothecium is associated with dehiscence of anther” Justify the statement.

• Endothecium is a layer in the anther wall.
• It has a single layer of radially elongated cells. It is below the epidermis.
• The tangential wall or radial wall has lignified thickenings.
• These cells are hygroscopic. This nature helps in the dehiscence of anther at maturity.

 
19. List out the functions of the tapetum.

• It supplies nutrition to the developing microspores.
• It contributes sporopollenin through ubisch bodies thus plays an important role in pollen wall formation.
• The pollenkitt material is contributed by tapetal cells and is later transferred to the pollen surface.
• Exine proteins responsible for the ‘rejection reaction’ of the stigma are present in the cavities of the exine. These proteins are derived from tapetal cells.

 
20. Write a short note on Pollenkitt.

• Pollen kitt is an oily layer on the pollen surface. 
• It is a viscous coating.
• It is contributed by tapetum.
• It is coloured yellow or orange.
• It is made of carotenoids, flavonoids.
• It attracts insects.
• It protects from damage by Uv radiation.

 
21. Distinguish tenuinucellate and crassinucellate ovules.
Tenuinucellate Ovule:

• Ovules with hypodermal sporogerous cell with unilayerd nucellus tissue is called tenuinucellate type.
• They have very small nucellus

Crassinucellate Ovule:

• Ovule with subhypodermal sporogenous cell is called crassinucellate type.
• They have large nucellus

 
22. ‘Pollination in Gymnosperms is different from Angiosperms’ – Give reasons.
Gymnosperms:

• Pollination in gymnosperms is direct.
• The pollens are deposited directly on the exposed ovules.

Angiosperms:

• In Angiosperms it is indirect.
• The pollens are deposited on the stigma of the pistil.

 
23. Write short note on Heterostyly.
Heterostyly: 

• Some plants produce two or three different forms of flowers that are different in their length of stamens and style. 
• Pollination will take place only between organs of the same length.
• Example: Primula.

 

24. Enumerate the characteristic features of Entomophilous flowers.

• Generally large. It is small aggregated in the inflorescence. 
• ex: Asteraceae flowers.
• Brightly coloured to attract insects.
• ex: poinsettia and Bougainvillea the bracts become coloured.
• Scented with nectar.
• Pollen and nectar are floral rewards. Pollen is used for consumption.
• Foul odour also attracts flies and beetles
• Juicy cells of flowers are pierced and sucked by insects.

 
25. Discuss the steps involved in Microsporogenesis.
Microsporogenesis: 

• The stages involved in the formation of haploid microspores from diploid microspore mother cell through meiosis is called Microsporogenesis. 
• The primary sporogenous cells directly, or may undergo a few mitotic divisions to form sporogenous tissue. 
• The last generation of sporogenous tissue functions as microspore mother cells.
• Each microspore mother cell divides meiotically to form a tetrad of four haploid microspores (microspore tetrad). 
• Microspores soon separate from one another and remain free in the anther locule and develop into pollen grains.

 
26. With a suitable diagram explain the structure of an ovule.
Structure of ovule(Megasporangium):

• Ovule is also called megasporangium and is protected by one or two covering called integuments. A mature ovule consists of a Raphe stalk and a body. 
• The stalk or the funiculus (also called funicle) is present at the base and it attaches the ovule to the placenta. The point of attachment of funicle to the body of the ovule is known as hilum. 
• It represents the junction ovule and funicle. In an inverted ovule, the funicle is adnate to the body of the ovule forming a ridge called raphe. 
• The body of the ovule is made up of a central mass of parenchymatous tissue called nucellus which has large reserve food materials. 
• The nucellus is enveloped by one or two protective coverings called integuments. Integument encloses the nucellus completely except at the top where it is free and forms a pore called micropyle.
• The ovule with one or two integuments are said to be unitegmic or bitegmic ovules respectively. The basal region of the body of the ovule where the nucellus, the integument and the funicle meet or merge is called chalaza. 
• There is a large, oval, sac-like structure in the nucellus toward the micropylar end called embryo sac or female gametophyte. It develops from the functional megaspore formed within the nucellus. 
• In some species(unitegmic tenuinucellate) the inner layer of the integument may become specialized to perform the nutritive function for the embryo sac and is called as endothelium or integumentary tapetum (Example: Asteraceae). 

 

27. Give a concise account on steps involved in fertilization of an angiosperm plant.

• The fusion of male and female gamete is called fertilization.
• Fertilization in angiosperms is double fertilization.

Events of fertilization

• The stages involved in double fertilization are:-
• Germination of pallen to form pollen tube in the stigma.
• Growth of pollen tube in the style.
• Direction of pollen tube towards the micropyle of the ovule.
• Entry of the pollen tube into one of the synergids of theembryo sac,
• Discharge of male gametes,
• One male gametes fuses with the egg to farm Zygote Second male gamete fuses with the polar nuclei and forms the primary endosperm nucleus (PEN).
• This phenomenon is called double fertilization
• It is unique to angiosperms.
• One male gametes (n) fuses with the egg (n) to form zygote (2n) is called syngamy
• Second male gamete (n) fuses with the polar nuclei (2n) and forms the primary endosperm nucleus (3n) this phenomenon is called triple fusion.
• It results endosperm which forms the nutritive tissue for the embryo

28. What is endosperm. Explain the types.

• The primary endosperm nucleus (PEN) divides immediately after fertilization but before the zygote starts to divide, into an endosperm.
• Three types of endosperm in angiosperms.
• 1. nuclear endosperm,
• 2. cellular endosperm and
• 3. helobial endosperm

1. Nuclear endosperm:

• Primary Endosperm Nucieus undergoes several mitotic divisions without cell wall formation.
• Thus free nuclear condition exists in the endosperm, 
• Examples: Coccinia, Capsella and Arachis

2. Cellular endosperm:

• Primary endosperm nucleus divides into 2 nuclei.
• It is Immediately followed by wall formation.
• Subsequent divisions also follow cell wali formation.
• Examples: Adoxa, Helianthus and Scopariu

3. Helabial endosperm:

• Primary Endosperm Nucleus divides into two nuclei
• 1. large micropylar 2. small chalazal chamber.
• The nucleus of the micropylar chamber undergoes
• several free nuclear division.
• The chalazal chamber may or may not divide.
• Examples: Hydrilla and Vallisneria. 

 

29. Differentiate the structure of Dicot and Monocot seed.

Dicot seed	Monocot seed
Two cotyledons in the embryo	One cotylerlon in the embryo
Plurmule is terminal.	Plumule is lateral.
cotyledons are lateral	cotyledons are terminal
No sheath	Plumule and radicle are surrounded by coleoptile and coleorhiza respectively
Albuminous and exalbuminous	Mostly albuminous
Germination is epigeal	Germination ishypogeal

 

30. Give a detalled account on parthenocarpy. Add a note on its significance

• Fruit may develop from the ovary without fertilization.
• are called parthenocarpic fruits.
• They donot have seeds.
• Ex: Banana, Grapes and Papaya

Significance parthenocarpic fruits

• The seedless fruits have great significance in horticulture.
• They donot have seeds.
• The seedless fruits have great commercial importance.
• Seedless fruits are useful for the preparation of jams, jellies, sauces, fruit drinks etc.
• High proportion of edible part is available due to the absence of seeds.

 

III. Long Answer Questions

12th bio botany

IV. Exercise

12thbio botany