Class-7th Science Chapter 12 Reproduction in Plants

 

 

SOLUTION OF NCERT CLASS-VII

 

Question 1: Fill in the blanks:
(a) Production of new individuals from the vegetative part of parent is called ________.
(b) A flower may have either male or female reproductive parts. Such a flower is called _________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _________.
(d) The fusion of male and female gametes is termed as __________.
(e) Seed dispersal takes place by means of _________, _________ and _________.
Answer: 

(a) vegetative propagation.
(b) unisexual.
(c) pollination.
(d) fertilisation.
(e) wind, water, and animals.

 

Question 2: Describe the different methods of asexual reproduction. Give examples.
Answer: The various modes of asexual reproduction in plants are as follows:
(i) Vegetative propagation: It is the ability of a plant to produce new plants from roots, stems, leaves, and buds. Vegetative propagation is divided into two types.

Natural vegetative propagation: This type of vegetative propagation occurs easily in nature and involves simple vegetative parts. Potato plant sprouting from an eye is a common example.

Artificial vegetative propagation: This type of vegetative propagation is performed manually and generally occurs in laboratory conditions. The formation of a complete plant from a stem cutting of rose is a common example of this method.

(ii) Budding: It involves the formation of a new individual from a bulb-like projection called a bud. The bud grows and gets detached from the parent to form a new individual. It is commonly observed in yeast.

(iii) Fragmentation: It is a form of asexual reproduction where a new organism is formed from the fragments of the parent body. It is the only mode of asexual reproduction in Spirogyra.
(iv) Spore formation: Many non-flowering plants reproduce through spore formation.
Spores are tiny cells protected by a thick wall. Fungi such as bread moulds reproduce asexually using this method.

Question 3: Explain what you understand by sexual reproduction.
Answer: Sexual reproduction is a process which involves production of seeds. It requires two parents. Most plants reproduce sexually with the help of flowers. The main function of a flower is to reproduce and therefore develop new seeds that can grow into new plants.

 

Question 4: State the main difference between asexual and sexual reproduction.
Answer: 

Differences between sexual and asexual reproduction:

Asexual reproduction	Sexual reproduction
It requires only one parent.	It requires two parents.
In asexual reproduction, newlydeveloped plants are identical to the parent and to each other.	In sexual reproduction, newly developed plantsare not identical to parents.
Special reproductive parts are notrequired for asexual reproduction.	Flower is the reproductive part of a plant whichcontains the sexual organs of a plant. These are important for sexual reproduction.
Examples are yeast, rose, jasmine,potato, etc.	Examples are flowering plants, such as Hibiscus,corn, papaya, etc.

Question 5: Sketch the reproductive parts of a flower.

Answer:

                 

Question 6: Explain the difference between self-pollination and cross-pollination.

Answer: Differences between self-pollination and cross-pollination:

Self-pollination	Cross-pollination
It involves the transfer of pollen from the stamen to the pistil of the same flower.	It involves the transfer of pollen from the stamen of one flower to the pistil of another flower of the same plant or that of a different plant of the same kind.
It occurs only in bisexual flowers.	It occurs in both unisexual and bisexual flowers.

Question 7: How does the process of fertilisation take place in flowers?
Answer: When pollen lands on stigma, it germinates and gives rise to a pollen tube that passes through the style and reaches the ovary of a pistil. When the pollen tube reaches an ovule, it releases the male gametes. A male gamete fuses with a female gamete in the ovule. This process is known as fertilisation. The cell which is formed after the fusion of a male and a female gamete is known as zygote. This zygote divides several times in order to form the embryo present inside the seed.

Process of fertilisation

Question 8: Describe the various ways by which seeds are dispersed.
Answer: Seed dispersal occurs by the following agencies.
(a)Dispersal by animals − There are many ways by which birds and animals can disperse seeds. For example, birds and animals can eat the fruits and excrete the seeds away from the parent plant. Some seeds have barbs or other structures that get attached to the animal’s body and are carried to new sites. Some fruits have hooks on them which cling to fur or clothes.
(b)Dispersal by wind − Seeds that get dispersed by wind are usually smaller in size or they have wings or hair-like structures. For example, winged seeds of drumsticks, hairy fruit of sunflower, etc. are dispersed by wind.
(c)Dispersal by water − Many aquatic plants or plants that live near water has seeds that can float and are carried away by water. For example, coconuts can float and are dispersed by water.
(d) Dispersal by explosion − Sometimes the seeds are dispersed by the bursting of fruits with sudden jerks. The seeds get scattered or distributed far from the parent plant. Examples of such plants are castor and balsam.

 

Question 9: Match items in Column I with those in Column II:

Column I	Column II
(a) Bud	(i) Maple
(b) Eyes	(ii) Spirogyra
(c) Fragmentation	(iii) Yeast
(d) Wings	(iv) Bread mould
(e) Spores	(v) Potato
	(vi) Rose

 

Answer:

Column I	Column II
(a) Bud	(iii) Yeast
(b) Eyes	(v) Potato
(c) Fragmentation	(ii) Spirogyra
(d) Wings	(i) Maple
(e) Spores	(iv) Bread mould

 

Question 10: Tick (√ ) the correct answer:

(a) The reproductive part of a plant is the
(i) leaf
(ii) stem
(iii) root
(iv) flower
(b) The process of fusion of the male and female gametes is called
(i) fertilisation
(ii) pollination
(iii) reproduction
(iv) seed formation
(c) Mature ovary forms the
(i) seed
(ii) stamen
(iii) pistil
(iv) fruit
(d) A spore producing plant is
(i) rose
(ii) bread mould
(iii) potato
(iv) ginger
(e) Bryophyllum can reproduce by its
(i) stem                 (ii) leaves
(iii) roots               (iv) flower

Answer:        (a) – (iv). flower,

(b) – (i). fertilization,

(c) – (iv). fruit,

(d) – (ii). bread mold,

(e) – (ii). leaves

Some most frequent asked questions for the examination purposes…..

(D) Very Short Answer Type Questions.

1.What is Reproduction?

Ans: Reproduction is the production of offspring. There are two main forms: sexual and asexual reproduction.

2. Name the different modes of asexual reproduction.

Ans: Both multicellular and unicellular species exhibit asexual reproduction. Fission, Fragmentation, Regeneration, Budding, Vegetative propagation and spore formation are the different forms of asexual reproduction.

3. Name the part of flower considering of filament and anther.

Ans: The stamen is made up of two parts: the anther and filament. The anther produces pollen (male reproductive cells). The filament holds the anther up.

4. What is grafting short answers?

 

Ans: Grafting is the act of placing a portion of one plant (bud or scion) into or on a stem, root, or branch of another (stock) in such a way that a union will be formed and the partners will continue to grow

 

5. What is Zygote?

Ans: A zygote is the first diploid cell that is formed by the fusion of male and female gametes resulting in the formation of an embryo. The zygote stage development occurs in the first week of fertilization.

6. What are the various agents of pollination?

Ans: Air, water, animals and insects are the common agents of pollination. Pollination by air: Light and dry pollen grains are carried by air to the other plants. Pollination by water: Pollen or the male flower is carried by water current towards the female flower to pollinate.

 (E) Short Answer Type Questions.

1. Why is reproduction is important in living beings?

Ans: Reproduction is necessary for living things because it enables them to create offspring and continue their population. Through reproduction, they pass on their genetic information to the next generation. This ensures that their species continues to exist on Earth which is why the organism reproduces.

2. Explain the process of Tissue Culture.

Ans: The stages of plant tissue culture are: selection/preparation (stage 0), initiation/establishment (stage 1), multiplication (stage 2), rooting (stage 3), and acclimatization/hardening (stage 4). A formulation for growth medium is selected based on which stage the plant is in or will be entering.

3. Give two differences between Binary Fission and Budding.

Ans: With budding, a parent cell creates an outgrowth that eventually becomes a daughter cell. With binary fission, a parent cell reproduces by splitting in half. Both types of reproduction are common among unicellular organisms [45], and can be found within extant multicellular taxa.

4. What is germination?

Ans: Germination is the process of seeds developing into new plants. First, environmental conditions must trigger the seed to grow. Usually, this is determined by how deep the seed is planted, water availability, and temperature.

5. What is meant by seed dispersal? Name the various agents which help in the dispersal of seeds.

Ans:  Seed dispersal is the mechanism by which plant seeds are transported to new sites for germination and the establishment of new individuals. Animals commonly mediate this process, and consequently, the ultimate fate of seeds depends on their effectiveness as seed dispersers.

6. Define self-pollination and cross-pollination.

Ans:

·        Self-pollination occurs when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant.

·        Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species.

(F) Long Answer Type of Questions.

1. List the methods of asexual reproduction in plants. Explain any two methods.

Ans:

Asexual reproduction in plants involves the generation of new individuals without the involvement of seeds or spores, and it typically results in offspring that are genetically identical to the parent plant. Here are two common methods of asexual reproduction in plants:

1. Vegetative Propagation:

·        Definition: Vegetative propagation involves the formation of new plants from vegetative structures such as stems, roots, and leaves, without the formation of seeds.

·        Methods:

·        Runners and Stolons: Some plants, like strawberries, produce horizontal stems called runners or stolons. These stems grow along the soil surface, producing nodes from which new plants develop.

·        Rhizomes: Plants like bamboo and ginger produce underground horizontal stems called rhizomes. Nodes along the rhizome give rise to new shoots, and these shoots can grow into independent plants.

·        Tubers: Potatoes are an example of plants that reproduce through tubers. Tubers are swollen, underground stems that develop eyes. Each eye can give rise to a new plant.

·        Offsets: Plants like aloe vera produce offsets or offshoots, which are small lateral shoots that develop near the base of the main plant. These can be separated and planted to grow into new plants.

2. Budding:

·        Definition: Budding is a method of asexual reproduction in which a new organism develops from an outgrowth or bud on the parent organism. This outgrowth eventually detaches and becomes an independent organism.

·        Process:

·        A small outgrowth, called a bud, forms on the parent plant. The bud contains undifferentiated cells capable of developing into various plant structures.

·        The bud continues to grow and differentiate into specialized tissues, such as stems, leaves, and roots.

·        Eventually, the bud becomes large enough to detach from the parent plant, either through natural processes or human intervention.

·        Once detached, the bud can take root and grow into a genetically identical copy of the parent plant.

Examples: Yeast, a unicellular fungus, reproduces through a form of budding. In plants, examples include the water lily, where new plants develop as buds on the surface of the parent plant's rhizomes.

2. What is vegetative reproduction? Explain artificial methods of vegetative propagation.

Vegetative reproduction is a form of asexual reproduction in plants where new individuals are produced from vegetative structures, such as stems, roots, or leaves, without the involvement of seeds. This method allows plants to propagate without the need for the complex process of sexual reproduction, and the offspring are genetically identical to the parent plant.

Artificial methods of vegetative propagation involve human intervention to create new plants with desirable traits. Here are some common artificial methods of vegetative propagation:

1. Cuttings:

·        Process: A portion of a stem, root, or leaf (cutting) is removed from the parent plant and placed in a suitable environment to encourage the development of roots and shoots.

·        Steps:

·        Select a healthy and disease-free plant as the source of the cutting.

·        Cut a portion of the stem, root, or leaf, ensuring it has nodes (points where leaves and buds emerge).

·        Treat the cutting with rooting hormones to stimulate root formation.

·        Plant the cutting in a suitable medium (like soil or a rooting medium) and provide optimal conditions for root and shoot development.

·        Once roots have developed, the cutting can be transplanted to a new location as an independent plant.

2. Grafting:

·        Process: Grafting involves joining two different plant parts in such a way that they unite and grow as one plant.

·        Steps:

·        Select a scion (the desired top part of the plant with specific traits) and a rootstock (the lower part of the plant with a well-developed root system).

·        Make precise cuts on both the scion and rootstock, ensuring they fit together perfectly.

·        Join the scion and rootstock and bind them together using grafting tape or a similar material.

·        Allow the graft to heal, and over time, the scion and rootstock will fuse, creating a plant with the desired traits of the scion and the strong root system of the rootstock.

3. Explain the structure of a flower with the help of a neat and labeled diagram.

Ans:

·        When a flower is in a bud stage, we can see a green color, leaf-like structure that covers the whole bud or flower, Each of these green-like structure present as an outermost layer is called as sepal. This outermost ring of sepals is known as calyx.

·        Petals are the largest part of flowers. The ey are often attractive, brightly colored, sometimes sweet-scented, and attract the insects. This ring of petals together is called a corolla.

·        Inner to this corolla, in Hibiscus, we can observe a long tube on which many stamens are arranged. But in Datura, we can see only fi ve stalked structures, stamens. This ring or whorl of a flower is called androecium. Each stamen consists of two parts – a stalk called filament and a lobe called anther. If you touch these lobes in a mature flower, you can get a powdery substance called pollen grains, the male reproductive part.

·        Inner to this androecium whorl, we can find a female reproductive part of the flower, called Gynoecium. You will find this part with a swollen bottom part. This is the ovary. Seeds are produced in this part. On top of the ovary, there is a slender tube-like structure called style. The topmost sticky tip of the style is the stigma.

4. What is the pollination? How does it lead to fertilization? Explain with the help of a diagram.

Ans:

Pollination:

The transfer of pollen grains from a flower's anther to the stigma of another flower is pollination.

Occurrence:

Pollination occurs with the help of many agents known as pollinating agents. The most common pollinating agents are wind, water, insects, animals, and humans.

The pollen tube descends through the style and eventually reaches the ovary. Finally, it passes via a tiny pore into the ovule. Here one male gamete fuses with an egg. It is the act of fertilization that results in the formation of a zygote and the development of an embryo.

Two sperm cells are involved in double fertilization: one fertilizes the egg cell to produce the zygote, while the other fuses with the two polar nuclei to produce the endosperm. The fertilized ovule becomes the seed after fertilization, while the ovarian tissues become the fruit.

5. Explain the various agents of seed dispersed.

Ans:

There are five main modes of seed dispersal: gravity, wind, ballistic, water, and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus.

6. Write short notes on sexual reproduction in plants.

Ans:

Sexual reproduction in plants takes place in the following steps:

1. The male reproductive organ stamen produces male gamete or anthers.
2. Simultaneously the female reproductive organ carpel produces the female gamete or the egg inside the ovules.
3. Pollination transfers the male gamete to the female organ. Male gametes fertilize the female gametes by forming a zygote capable of growing into a new plant.
4. The fertilized ovules containing the zygote harden their coat to form seeds.
5. The seeds produce new plants under favorable condition like the presence of water, warmth, air, light, etc

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