Important Questions Class 12 Biology Chapter 2
Important Questions Class 12 Biology Chapter 2
Important Questions for CBSE Class 12 Biology Chapter 2 – Sexual Reproduction in Flowering Plants
Sexual reproduction in flowering plants is the focus of Chapter 2 in Class 12 Biology. Students will learn about the various parts of a flower that are involved in sexual reproduction in Chapter 2. Students will learn about the structure of flowers and the various terms associated with reproduction in flowering plants. Flowering plants reproduce sexually, with both male and female gametes competing to produce new offspring.
Extramarks Class 12 Chapter 2 Biology Important Questions are useful for students during exams to quickly understand the key concepts. It will assist students in becoming acquainted with all possible board exam questions. These questions are compiled by subject matter experts and written in a clear, concise manner so that it will take less time to cover the entire chapter without skipping any topic..
CBSE Class 12 Biology Chapter-2 Important Questions
Study Important Questions for Class 12 Biology Chapter 2- Sexual Reproduction In Flowering Plants
A set of questionnaires with 1,2,3 and 5 marks respectively are given below. The answers for these questions are written from NCERT books with step by step explanations which help students revise and understand how to frame the answers with the marks provided.
1 Mark Question and Answers
Q. If an angiospermic plant has a diploid number of chromosomes of 16. Mention how many chromosomes are in the endosperm and antipodal cell.
Endosperm contains chromosomes, and antipodal cells contain 16 chromosomes.
Q. At the end of microsporogenesis and megasporogenesis, what structures are formed?
Microsporogenesis involves the formation of four haploid dust grains in a tetrahedral tetrad, whereas Megasporogenesis involves the formation of four megaspores in a linear tetrad.
2 Marks Questions and Answers
Q. Cell division occurs in Angiospermic plants prior to the formation of microspores in sporogenous tissue.
Polyembryony is defined as the presence of more than one embryo in a seed. For example, more than one embryo may be created inside an embryo sac by splitting the egg or by cleavage, endosperm, synergid, or antipodal cleavage.
Insects, particularly bees, are the most important pollinators among animals.
Q. List any four distinguishing characteristics of the insect-pollinated flower.
The insect-pollinated flower has four distinguishing characteristics:
- The flowers are quite large.
- Flowers have colourful petals.
- The presence of perfume in flowers.
- They are rich in nectar.
Q.Why can pollen grains survive as fossils so well?
Pollen grains are well preserved as fossils because their exine is composed of sporopollenin, a chemical that can withstand high temperatures, strong acids and alkalis, and strong enzymes.
Q. How are the cells in an embryo sac organised?
An embryo sac is a seven-celled, eight-nucleated structure. At the micropylar end, three cells are present: two synergids and one egg cell. The chalazal end has three cells known as antipodals. A central cell with two polar nuclei exists.
3 Marks Questions and Answers
Q. Distinguish microsporogenesis from megasporogenesis. What type of cell division takes place during these events? Name the structure that results from these two events.
Microsporogenesis is the process by which microspores are produced from Pollen mother cells. Megasporogenesis is the process by which megaspores are produced from MMC. Meiotic division occurs during both Microsporogenesis and Megasporogenesis, resulting in the formation of pollen grains and megaspores.
Q. What exactly is triple fusion? Where does it happen?
The nucleus of a pollen grain’s vegetative cell joins with two polar nuclei of the female gametophyte’s central cell to form the primary endosperm. Because it involves three nuclei, this fusion is known as vegetative fusion or triple fusion. It takes place in the central cell of the egg apparatus.
Q. Explain the stages of development of a microspore into a pollen grain.
A dense cytoplasm surrounds the microspore, with a larger nucleus in the centre. The nucleus of the microspore shifts to the side as it develops due to the production of vacuoles in the upper end of the cytoplasm. Mitotic division causes the nucleus to split into two nuclei, each of which separates into two cells: the lower generative cell and the larger upper vegetative cell. A mature pollen grain has two cells.
Q. Describe the composition of a pollen grain.
Pollen grains are typically spherical with two wall layers.
The outer layer is exine composed of sporopollenin, a highly resistant organic substance that is absent at the aperture region known as the germ pore.
The inner layer, known as the intine, is composed of pectin and cellulose.
A mature pollen grain contains both vegetative and generative cells.
Q. Follow the growth of microsporocytes into mature pollen grains.
During the early stages of development of the anther, the microsporangium has closely arranged homogenous cells that form the sporogenous tissues.
- Each sporogenous tissue cell develops into a pollen mother cell (PMC) and produces microspore tetrads or pollen grains.
- However, some of them lose this potential and eventually differentiate into pollen or microspore mother cells (MMC)
- Each microspore mother cell (MMC) goes through meiosis and produces a cluster of four haploid cells known as a microspore tetrad.
- As the anther matures, the microspores separate from the tetrad and grow into pollen grains.
- Mitosis occurs in microspore nuclei to produce larger vegetative cells and smaller generative cells. They form a double-layered wall, with the outer exine composed of sporopollenin.
- The inner intine is composed of cellulose and pectin. Pollen grains are typically released in two-celled stages.
5 Marks Questions and Answers
Q. What are the post-fertilization changes that occur in a flowering plant?
(i) Endosperm Development: Endosperm development occurs before embryo development. The nuclear type is the most common method of endosperm development in which triploid endosperm (PEN) undergoes repeated mitotic divisions without cytokinesis – cell wall formation occurs from the periphery and endosperm stores food materials.
(ii) Embryo Development: First, the zygote divides via mitosis in a pro-embryo. Later development results in the formation of a globular and heart-shaped embryo, which eventually develops into a horseshoe-shaped embryo with one or more cotyledons. The portion of the embryonal axis around the level of attachment in a dicot embryo is epicotyl and reduces to plumule, while the portion of the embryonal axis below the level of attachment is hypocotyl and it eventually terminates into a radicle.
Important Questions for Class 12 Biology Chapter 2
Why is Chapter 2 Important for Students?
Sexual Reproduction in Flowering Plants is covered in Chapter 2 of Biology Class 12. This may be a challenging chapter for students , but they can easily learn and understand it better if they make use of study materials available on our website. This chapter is critical because many questions in the final examinations are often repeated in the board exams. . Furthermore, sexual reproduction in flowering plants has a significant weightage in competitive examinations as well.
Relevance of Chapter 2
Plant reproduction is required because it assists plants in producing offspring. Plants can reproduce sexually or asexually. In plants, sexual reproduction occurs through the fusion of gametes.
Students should learn about these because it will help them better understand plant reproduction and conduct lab experiments with ease. . They must first have a clear understanding of the basics before proceeding further.
Why is it Important to Study Class 12 Biology Chapter 2 Important Questions from Extramarks?
It is crucial to study Class 12 Biology Chapter 2 Important Questions from Extramarks because students can obtain all necessary assistance from our website. Not only are the important questions available, but also study notes, class notes, and revision notes, which students can use to enhance their learning abilities by offering deeper understanding of the chapter. For the best preparations, diagrams and step-by-step explanations of the solved solutions are provided.
How to Study for Chapter 2 Sexual Reproduction in Flowering Plants
We recommend that students follow the pattern below for the best possible preparation before exams.
- Examine the study notes and class notes available on our website and make your own notes from them.
- For a better understanding of the topics, carefully study the diagrams and draw them individually.
- Solve the important Chapter 2 Biology Class 12 Important Questions so that students are aware of the various types of questions that may appear in examinations.
Introduction to Sexual Reproduction in Flowering Plants
Reproduction in plants refers to the birth of offspring. Sexual or asexual reproduction is possible in plants.
Angiosperms, or flowering plants, reproduce sexually. Male and female gametes found in the flower are used in this reproduction method. Even if certain parts of flowering plants are sterile, they still aid in reproduction.
In this chapter, we will investigate the various parts of the flower to understand their nature and the role they play in the reproduction process.
Topics Included under Sexual Reproduction in Flowering Plants
The topics that will be covered here are as follows:
Stamen, Microsporangium, and the Pollen Grains
The filament and the anther are the two parts of the stamen. The filament is a long, slender stalk, whereas the anther is a bilobed structure with two thecae in each lobe, making them dithecous.
The anther is tetragonal in shape and is made up of microsporangia that are located at the edge of each lobe.
The microsporangia is the fusion of microspores from a pollen mother cell via meiosis. The microsporangia grow into pollen sacs.
Male gametophytes are pollen grains. Pollen grains mature into two types of cells: vegetative cells and generative cells.
Sexual Reproduction in Flowering Plants Occurs in Three Stages
Pollination – Pollination is the transfer of pollen grains across the anther and stigma of the same flower of one plant or between flowers of different plants. This results in fertilisation and seed production. Birds, wind, animals, and water all spread pollen grains.
Pollination occurs in three ways: autogamy, geitonogamy, and xenogamy.
Formation of a Zygote – Following pollination, the male gamete is transported down the pistil style to the ovary. The male gamete fuses with the female gamete to form a zygote. After some endosperm is produced, the embryo develops and the zygote splits. This aids in the nutrition of the developing embryo.
Fruit and seed formation- The zygote develops in the embryo after formation. Meanwhile, the ovules develop into seeds, and the ovary develops into a fruit. Fruits are responsible for the formation of seeds. Other reproductive processes, such as pollination and fertilisation, are required for seed formation. This process is also water-dependent. Seeds have an extremely adaptable strategy that allows them to colonise new areas. Young seedlings can feed themselves and are self-sufficient. The new seeds also have new genetic combinations, resulting in variations. The seeds formed in this manner can be stored for almost a year.
To summarise, sexual reproduction in plants is an important chapter for students in class 12. They are not only important for school and board exams, but they also have more weightage in many competitive exams. Extramarks’ Important Questions for Class 12 Biology Chapter 2 will allow students to become more familiar with the important questions, saving valuable time and getting good grades in both the board exams as well as competitive exams later on.
FAQs (Frequently Asked Questions)
1. What is the structure of anther?
The anther has two lobes, each with two cells. The two lobes are separated by a groove that runs longitudinally. The anther has four sides and four microsporangia on each corner, with two in each lobe. Microsporangia develop into pollen sacs. They continue to develop and contain a large number of pollen grains, which aid in the fertilisation of flowering plants.
2. Describe the properties of insect-pollinated flowers.
An entomophilous flower possesses the following characteristics:
- The petals and sepals are well developed and have attractive colours to attract insects.
- Flowers are typically larger in size and have a strong odour.