Solved examples for class 7 science : Chapter 12
Reproduction in Plants
I. Multiple Choice Questions (MCQs).
Q.1. In a plant, root, stem and leaves are altogether called
a) vegetative parts
b) reproductive parts
c) germinative parts
d) all of these
Answer: (a) vegetative parts
Q.2. An outgrowth formed on the body of simple organisms, for asexual reproduction is called
Answer: b) bud
Q.3. Which of the following is not a bisexual flower?
Answer: d) Begonia
Q.4. The process of fusion of male and female gametes is called
d) asexual reproduction
Answer: (b) fertilisation
Q.5. The male reproductive part of a flower is
Answer: (a) androecium
II. Fill in the blanks by selecting appropriate words from the given list : List : coconut, seed, Rafflesia, stamens, flowers
Q.1. The flowering plant bears ______________ after a certain period of growth.
Q.2. After fertilisation, the ovule grows into a ______________.
Q.3. Androecium consists of whorls of ______________.
Q.4. Seeds of ______________have a spongy or fibrous outer coat.
Q.5. ______________ flower is the largest flower of the plant kingdom.
III. Match the items of Column A with those of Column B.
Answer: 1-e, 2-a, 3- d, 4-b, 5-c
IV. Write ‘T’ for the true and ‘F’ for the false statements.
Q.1. A spore in suitable conditions germinates to form a new plant.
Q.2. Leaves of Bryophyllum develop buds in their margins.
Q.3. Seedless varieties of plants can be grown by the vegetative propagation by leaf.
Q.4. Gynoecium consists of stigma, style and ovary.
Q.5. Offspring produced by vegetative propagation are very much similar to their parent plants.
Answer: 1-T, 2- T, 3-F 4-T 5-T
V. Very Short Answer Questions.
Q.1. Define pollen tube.
Answer: A tube that carries male gamate produced by pollen grain.
Q.2. Name an organism which reproduces through fragmentation.
Answer: Algae reproduces by fragmentation
Q.3. Name two plants in which vegetative propagation by stem is possible.
Answer: Bryophyllum and Begonia
Q.4. How reproduction occurs in mango and apple plants?
Answer: Reproduction occurs in mango and apple plants by grafting.
Q.5. Write some pollinating agents.
Answer: The various agents involved in pollination are insects, wind, water, birds, etc.
VI. Short Answer Questions.
Q.1. Do all flowers contain both of reproductive parts? Describe with examples.
Answer: No, all flowers do not both of reproductive parts. Some flowers have either male or female reproductive part. These flowers are called unisexual flowers. Begonia, corn, papaya and cucumber are some examples of unisexual flowers.
Q.2. How does pollination occur? Explain in brief.
Answer: There are various mechanisms involved in the pollination.
(a) Pollination by insects – Insects visit flowers to get nectar. The pollen grains stick to the body of the visiting insects. When they sit on another flower, the pollen gets transferred to the stigma on this flower.
(b) Pollination by wind – Some plants have small flowers. The pollen grains are very Light and easily carried by the wind. The flowers are made in a way that slight breeze disperse and carry away the pollen grains.
(c) Pollination by water- In the aquatic plants such as Vallisneria, Hydrilla, etc., pollination is brought about by the water.
(d) Pollination by birds- In some plants such as pomegranate and Kadam tree, pollination is brought about by birds.
Q.3. Describe some common methods of asexual reproduction briefly. Give examples also.
Answer: Some common methods of asexual reproduction are :
(a) Budding: In some simple organisms an outgrowth is formed from their body. This outgrowth is called bud. This bud may remain attached to parent body to form another bud or may get detached from parent to form a new individual. Yeast reproduces through budding.
(b) Fragmentation: Some algae such as Spirogyra grow near stagnant water bodies multiply by breaking into two or more fragments. Each fragment grows into a new individual.
(c) Spore formation: Many plants that do not produce flowers reproduce through spore formation. Each spore is covered by a thick wall that protects it from unfavourable conditions. Spores are developed inside a sporangia. Mosses, ferns and fungi reproduce through spore formation. A spore in suitable conditions germinates to form a new plant.
4. What do you mean by vegetative parts of a plant? How is reproduction possible through such parts under favourable conditions?
Answer: In a plant root, stem and leaves are called vegetative parts of a plant.
Vegetative propagation by root – Storage roots of sweet potato, Asparagus and Dahlia when get detached from the parent plant can grow into a new plant.
(a) Vegetative propagation by stem – In certain plants like potato, ginger, turmeric, etc. new plants can be developed from underground stems.
(b) Vegetative propagation by Leaf – Leaves of certain plants develop buds in their margins. These buds develop in a new plant after falling in soil. The plants of Bryophyllum and Begonia reproduce through this mean.
5. What is fertilisation? What happens with the different parts of a flower after fertilisation?
Answer: Fertilisation occurs when the ovule and the pollen grains fuse to form a zygote. By repeated cell division, the zygote grows from a single cell into a many-celled embryo. When pollen grain reaches the stigma, it develops a tube called pollen tube that grows down through the style. This tube carries male gamate produced by pollen grain. The male gamate is discharged into ovule present in ovary. Ovule contains a female gamate called egg. Male gamate fuses with female gamate. This process is called fertilisation.
After fertilisation the ovary grows into a fruit and the ovules into seeds. All other parts of the flower fall off. Zygote divides to form an embryo that lies within a seed.
VII. Long Answer Questions.
Q.1. Describe vegetative propagation by artificial methods with the help of suitable examples. Write its advantages also.
Answer: Plants can also be vegetatively propagated by some artificial methods :
(i) Cutting : Cutting means a piece of stem having a few nodes. When this cutting is buried in moist soil, new roots develop in its underside and it develops into a new plant. Bougainvillea, rose, champa, sugarcane, etc., reproduce through stem cutting.
(ii) Layering : In this type of vegetative reproduction, the branch of a plant is bent and covered with moist soil. After some days the roots develop from the branch which grows into a new plant. This plant becomes separate from the parent plant. This is a common practice with plants like jasmine, Bougainvillea, etc.
(iii) Grafting : In this method, a small branch of plant [scion] is inserted into a cut made in a rooted stem [stock). Now, both scion and stock are tied together to develop a new plant. This type of reproduction takes place in citrus, mango, apple, etc.
Advantages of Vegetative Propagation
• Plants which are not capable of producing seeds, can be reproduced vegetatively for example, banana, grapes, rose, jasmine, etc.
• The offspring produced by vegetative propagation are very much similar to their parent plant.
• Plants raised by vegetative propagation bear flowers and fruits earlier than the plants raised by seeds.
• Seedless variety of plants can be grown by the artificial vegetative propagation.
Q.2. With the help of diagrams only show layering, grafting and stem cutting.
Answer: Following diagrams show layering, grafting and stem cutting.
Q.3. Describe the structure of flower with the help of a well-labelled diagram.
Answer: A flower consists of four whorls. The outermost whorl is of sepals that are green in colour, the second whorl is of colourful petals, third whorl has the male sex organs, stamens, and the last whorl has the female sex organ, pistil. The stamen consists of a filament and an anther. The anther has two lobes, which contain minute pollen grains. There is a double-walled structure around the pollen grain. Male gametes are produced in pollen grains. The female organ, pistil has three parts –ovary, style and stigma. Stigma is a lobe-like structure, which is connected with the ovary through tube-like structure called style.