Class 7 Science Chapter 12 Important Questions
Class 7 Science Chapter 12 Important Questions Answers and Main Keywords of Reproduction in Plants for current academic session 2020-2021. Questions are taken from the new NCERT books issued for 2020-21.All the questions are important to know the chapter properly. State boards like MP board, UP board and other board students also take the benefits of these extra questions. Answers of each question is given in simplified format so that student can understand easily.
Class 7 Science Chapter 12 Important Questions for 2020-2021
|Chapter: 12||Reproduction in Plants|
|Contents:||Important Questions with Answers|
Class 7 Science Chapter 12 Important Questions Set – 1
What is reproduction?
To produce its kind is a characteristic of all living organisms. The production of new individuals from their parents is known as reproduction.
What do you know about vegetative and reproductive parts of a plant?
Most plants have roots, stems and leaves. These are called the vegetative parts of a plant. After a certain period of growth, most plants bear flowers. The flowers perform the function of reproduction in plants. Flowers are the reproductive parts of a plant. A flower may have either the male part or the female part or both male and female parts.
Define asexual and vegetative reproduction.
There are several ways by which plants produce their offspring. These are categorised into two types: (i) asexual, and (ii) sexual reproduction. In asexual reproduction plants can give rise to new plants without seeds, whereas in sexual reproduction, new plants are obtained from seeds.
Asexual reproduction, in asexual reproduction new plants are obtained without production of seeds or spores. Vegetative propagation It is a type of asexual reproduction in which new plants are produced from roots, stems, leaves and buds. Since reproduction is through the vegetative parts of the plant, it is known as vegetative propagation.
What do you mean by node, axil and bud?
Node is a point on the stem or branch of a plant where a leaf is attached. Buds are also present in the node regions of a plant.
Axil is the upper angle between a leaf stalk and the stem from which it is growing.
Bud is a compact, knob-like undeveloped shoot consisting of a shortened stem and immature overlapping leaves. Buds are the growing points of a plant.
How do Bryophyllum plants reproduce?
Some plants reproduce themselves from leaves. One example of a plant which can reproduce from its leaves is “bryophyllum”. Bryophyllum (sprout leaf plant) has buds in the margins of leaves. If a leaf of this plant falls on a moist soil, each bud can give rise to a new plant. When a mature leaf of the “bryophyllum” plant falls on the ground, they grow into a new plant. Plants such as cacti produce new plants when their parts get detached from the main plant body.
Class 7 Science Chapter 12 Important Questions Set – 2
With the help of an activity show, cutting plays an important role in vegetative propagation.
Cut a branch of rose or champa with a node. This piece of branch is termed a cutting. Bury the cutting in the soil. A node is a part of the stem or branch at which a leaf arises. Water the planted cutting every-day. After a few days, the end of cutting buried in the soil develops roots. The bud develops into a shoot or branch with leaves. In this way, the branch cutting of a rose plant grows to become a new rose plant.
“The vegetative buds can also give rise to new plants” – How?
Flower buds are present in a plant. Apart from flower buds, there are buds in the axil (point of attachment of the leaf at the node) of leaves which develop into shoots. These buds are called vegetative buds.
Take a fresh potato. Observe the scars on it with the help of a magnifying glass. You may find bud(s) in them. These scars are also called “eyes”. Cut a few pieces of a potato, each with an eye and bury them in the soil. Water the pieces regularly for a few days and observe their progress. Thus, a cut part of a potato with a bud can grow into a new potato plant. Each potato plant produces more than one tuber, and each tuber has more than one bud (which produce more than one new plant).
“Roots plays an important role in vegetative propagation”. Comment.
The roots of plants normally do not bear buds. There are some plants which have modified, thickened roots which bear buds. For example, sweet potato plant has modified roots thickened with stored food which are called root tuber. The root tubers of sweet potato have buds or eyes on them which can grow to produce new sweet potato plants. Thus, sweet potato plants are reproduced by the method of vegetative propagation through their root tubers.
Anil wants to know the advantage of vegetative propagation. Would you help him?
Advantage of vegetative propagation:
- i) New plants contain the genetic material of only one parent.
- ii) Used to propagate those plants which are not able to produce seeds.
- iii) Purity of variety is maintained and a quick method.
- iv) Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced by seeds.
How does bud play an important role in reproduction?
Yeast is a single-celled organism. Yeast can be seen only under a microscope. These grow and multiply every few hours if sufficient nutrients are made available to them. Take a piece of yeast cake or yeast powder from a bakery or a chemist shop. Take a pinch of yeast and place it in a container with some water. Add a spoonful of sugar and shake to dissolve it. Keep it in the warm part of a room. After an hour, put a drop of this liquid on a glass slide. You may see the formation of new yeast cells. The small bulb-like projection coming out from the yeast cell is called a bud. The bud gradually grows and gets detached from the parent cell and forms a new yeast cell. The new yeast cell grows, matures and produces more yeast cells. Sometimes, another bud arises from the bud forming a chain of buds. If this process continues, a large number of yeast cells are produced in a short time.
Class 7 Science Chapter 12 Important Questions Set – 3
How fragmentation occurs in spirogyra (an alga)?
Spirogyra is a filamentous charophyte green alga which have spiral arrangement of the chloroplasts. These are found as slimy green patches in ponds, or in other stagnant water bodies. These are the algae. When water and nutrients are available algae grow and multiply rapidly by fragmentation. An alga breaks up into two or more fragments. These fragments or pieces grow into new individuals. This process continues and they cover a large area in a short period of time.
Discuss the spore formation in bread mould.
The bread mould or Rhizopus plant undergoes asexual reproduction using spores. Spores are resistant to adverse environmental conditions. Though spores are present in the environment, fungus does not grow on dry surfaces. They need moisture to grow. Hence, fungus is seen on the bread. Observe the spores in the cotton-like mesh on the bread. When spores are released, they keep floating in the air. As they are very light, they can cover long distances. The spores are asexual reproductive bodies. Each spore is covered by a hard protective coat to withstand unfavorable conditions such as high temperature and low humidity. So, they can survive for a long time. Under favorable conditions, a spore germinates and develops into a new individual. Plants such as moss and ferns also reproduce by means of spores.
What do you mean by bisexual flowers unisexual flowers?
The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The flowers which contain both stamens and pistil are called bisexual flowers. Corn, papaya and cucumber produce unisexual flowers, whereas mustard, rose and petunia have bisexual flowers. Both the male and the female unisexual flowers may be present in the same plant or in different plants.
During sexual reproduction, how does zygote form in plant?
The flowers are the reproductive parts of a plant. The stamens are the male reproductive part and the pistil is the female reproductive part. Anther contains pollen grains which produce male gametes. A pistil consists of stigma, style and ovary. The ovary contains one or more ovules. The female gamete or the egg is formed in an ovule. In sexual reproduction a male and a female gamete fuse and form a zygote.
What do you mean by pollination?
We know that anther contains pollen grains which produce male gametes. Generally, pollen grains have a tough protective coat which prevents them from drying up. Since, pollen grains are light, they can be carried by wind or water. Insects visit flowers and carry away pollen on their bodies. Some of the pollen lands on the stigma of a flower of the same kind. The transfer of pollen from the anther to the stigma of a flower is called pollination.
Class 7 Science Chapter 12 Important Questions Set – 4
Are you familiar with the word “self-pollination” and “cross-pollination”?
Pollen grains are light; they can be carried by wind or water. Insects visit flowers and carry away pollen on their bodies. If the pollen lands on the stigma of the same flower it is called self-pollination. When the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different plant of the same kind, it is called cross-pollination.
“The zygote develops into an embryo” – How?
The stamens are the male reproductive part and the pistil is the female reproductive part. Anther contains pollen grains which produce male gametes. The cell which results after fusion of the gametes is called a zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilization. The zygote develops into an embryo.
How does seeds and fruits dispersed by wind?
Seeds and fruits of the plants are carried away or dispersed by wind, water animals. Some seeds are also dispersed by an explosive mechanism in which the ripe fruits of some plants brust on their own by making a little explosion and throw their seeds away from the plants with a great force.
The seeds and fruits dispersed by wind either have wing like structure or they have hair or they are very small and light, which helps them to be easily carried away by the blowing wind. For example, the seeds of drumstick plant and maple plant have wings so that they can be carried away by wind to faraway places and dispersed.
How does seeds and fruits dispersed by water?
The seeds and fruits of some of the plants are dispersed by water. The seeds and fruits which are dispersed by water develop “floating ability” in the form of “spongy or fibrous” outer coats. The seeds of water lily plant and coconut plant are dispersed by water. The coconut fruit have a fibrous outer coat which enables them to float in water and carried away by flowing water to far off places. Coconut fruit floating in sea water are carried hundreds of kilometers away by the sea current to other parts of land. It is due to the dispersal of coconut fruits by sea-water that coconut trees grow in all the coastal areas.
What do you think, will happen if all seeds of a plant were to fall at the same place and grow there?
All the seeds of a planned way to fall at the same place below the plant and grow there then, there would be deficiency of the mineral in the soil which the plant requires. There can be a competition between the plants of same species and further may lead to the death of the plants, so the seeds dispersed to the other place and germinates so that they can grow in efficient conditions.
Class 7 Science Chapter 12 Important Questions Set – 5
After germination, how does a seed grow into new plant?
A seed on germination grows into a new plant and fertilization in plants can only occur after pollination. When a seed is sown in the moist soil, it begins to grow and called germination. And in this stage, the seed coats splits (as tiny root grows) downward and (the shoot grows) upwards. The seedling grows further and ultimately forms a new plant. And after a certain period, the plant bears flowers once again.
Deepak wants to know how the male gamete in the pollen grain reaches the female gamete present in the ovule.
Pollen grain germinate on stigma. Pollen tube is formed, which carries the sperm cell or male gamete. This pollen tube makes its way through the style and reaches to ovule. One of the main gametes fertilizes egg cell present in the ovule to form an embryo.
Sohan wants to know why flowers are generally so colorful and fragrant?
Flowers also have fragrance in order to attract insects which help in pollination. Bright flowers attract insects during day time, so that the insects visit the plant, sit on the flowers and help in pollination process.
Explain the various steps involved in the formation of a plant, starting from the pollination.
- i) A seed on germination grows into a new plant and fertilization in plants can only occur after pollination. The transfer of pollen grains from anther of a stamen to stigma of a pistil is called pollination.
- ii) It can occur by two ways as self-pollination (transfer occur in same flower or another flower of same plant) and cross-pollination (transfer occurring between flowers of two separate but similar plants. Insects, water and wind are agents of pollination.
- iii) The process in which the male gamete present in pollen grain fuses or joins with the female gamete present in ovule to form a new cell called zygote, is called fertilization.
- iv) After fertilization two main things happen. As the ovule present in ovary grows to become a seed. After fertilization ovary of a flower develops and becomes a fruit (with seeds inside it). Thus, fruit is the ripened ovary of a flower.
- v) When a seed is sown in the moist soil, it begins to grow and called germination. And in this stage, the seed coats splits (as tiny root grows) downward and (the shoot grows) upwards. The seedling grows further and ultimately forms a new plant.
One morning as Rupali strolled in her garden. She noticed many small plants, which were not there a week ago. She wondered, where they had come from as nobody had planted them there. Explain the reason for the growth of these plants.
The small plants which were not there in the garden in a week ago may have grown up due to the seed dispersal. The seeds from the tree may have fallen below or have been dispersed by wind or animals on the ground, which on germination developed into new small plants.