MOECDC Class 8 Life process
MOECDC Class 8 Science and Technology | Life process | Nepal Class 8 | Exercise | Question Answer
MOECDC Class 8 English Medium Science Chapter 5 Life process Exercise Question Answer Solution.
| Board | Government of Nepal. |
| Class | Eight (8). |
| Subject | Science and Technology. |
| Chapter | Life process |
| Topic | Exercise Solve / Question Answer / Notes. |
Exercise 1 :
(1) Choose the best alternative from the given answers:
(a) How are new organisms formed during regeneration?
(i) growth of new life from the freshly fragmented part of the parent body
(ii) regenerating the fragmented part into a whole body
(iii) re-fragmenting the fragmented part
(iv) direct development of body from fragmented part.
Answer :
New organisms are formed during regeneration – (ii) regenerating the fragmented part into a whole body.
(b) What should be followed while propagating plants through cutting?
(i) there should be few leaves in the cut part
(ii) there should be new buds in the cut part
(iii) the cut branch should be taken from the upper part of the stem of the parent plant
(iv) there should be a few nodes in the cut part.
Answer :
(iv) There should be a few nodes in the cut part – while propagating plants through cutting.
(c) Which of the following represents the meaning of reproduction?
(i) mechanism birth and death
(ii) to give birth to young ones at maturity
(iii) biological process of giving birth
(iv) forming seeds, laying eggs, giving birth
Answer :
(iv) Forming seeds, laying eggs, giving birth – represents the meaning of reproduction.
(d) Which type of reproduction is shown in the figure?
(i) tuber
(ii) rhizo1ne
(iii) bulbils
(iv) corm
Answer :
reproduction is shown in the figure.
(e) If producing many plantlets from small ex-plant in a lab under the controlled environment is tissue culture, then which of the following sentence is related to this method?
(i) Only a small piece of stem or branch of the parent plant is taken
(ii) Whole part of the plant is taken
(iii) Small cut pieces of both plants and animals can be taken for generating offspring
(iv) It can be done only in non-flowering plants.
Answer :
If producing many plantlets from small ex-plant in a lab under the controlled environment is tissue culture, then (i) only a small piece of stem or branch of the parent plant is taken – is related to this method.
(2) Differentiate:
(i) Fission and Budding
Answer :
(i) In fission, the formation of new organism happens by splitting parent body. But in budding, a small bud appears on a body or cell which gradually grows into the complete organism and separates from the parent body.
(ii) Fission occurs only in unicellular organisms like amoeba, chlorella. But budding occurs in lower organisms like yeast, hydra.
(ii) Bulbils and rhizome
Answer :
Bulbils and rhizome:
(i) In some plants, few buds are formed at nodes or the base of the leaf or on the top of the short-fleshy stem which is called bulbils from which new root and shoot grow to be the new plants. But rhizome is underground stem which has given rise to many buds which grows as new plants in every next season.
(ii) Pineapples, lily, onion propagate through their bulbils. Ginger, turmeric and plants like ferns have rhizomes.
(iii) Natural and artificial v. propagation
Answer :
Natural and artificial v. propagation:
(i) Production of new plants asexually from seed is called natural vegetative propagation. But in artificial vegetative propagation, the production of new plants asexually happens using tools and techniques.
(ii) In natural vegetative propagation, plants take some time to yield. But in artificial technique, plants start yielding much sooner than the plants which are grown from seeds.
(iv) Layering and Grafting
Answer :
Layering and Grafting : Layering is done to the plants having soft branches grows from the very lower part of the stem. On the other side, the grafting technique is used to prepare plantlets of fruit plants having good productivity.
(3) Give reason:
(i) Asexual reproduction has no concept of male and female.
(ii) The reproduction from the tuber of a potato is called vegetative propagation..
(iii) Farmers will be benefitted from grafting techniques
(iv) Tissue culture is considered the most advanced method among other methods of vegetative propagation.
Answer :
(a) Asexual reproduction has no concept of male and female because in this reproduction system, organisms reproduce through a specific organ without the fusion of gametes.
(b) The reproduction from the tuber of a potato is called vegetative propagation as tuber of potato is an underground stem which is a vegetative part.
(c) Farmers will be benefitted from grafting techniques because in this technique, plants soon start yielding having same quality as the plants from which the scions were taken.
(d) Tissue culture is considered the most advanced method among other methods of vegetative propagation because with this technique, hundreds of thousands of disease-free and genetically desirable plantlets of any kind of plant can be produced within a limited time.
(4) Answer the following questions :
(a) What is reproduction? Give an example
Answer :
Giving birth to own kind through any biological method by organisms is called reproduction. Example – in plants, reproduction occurs either through the seeds or spores or any of the asexual methods.
(b) What are the types of asexual reproduction? Describe any one of them if brief.
Answer :
The types of asexual reproduction are, fission, budding, fragmentation, regeneration, sporulation and parthenogenesis.
Budding – Yeast, hydra, obelia, taenia, corals and jellyfish like lower organisms adopt the budding process for asexual reproduction. In this method, a small bud appears on a body which gradually grows into the complete organism and separates from the parent body.
(c) Describe the budding process in Hydra with suitable figures
Answer :
In budding process, a small bud appears on a body of hydra which gradually grows into the complete organism and separates from the parent body.
(d) Make a flowchart of the methods of vegetative propagation.
Answer :
(e) What kind of reproductive unit is bulbil? Give an example.
Answer :
In some plants, few buds are formed at nodes or the base of the leaf or on the top of the short-fleshy stem which is called bulbils from which new root and shoot grow to be the new plants.
Example – Pineapples, lily, onion propagate through their bulbils.
(f) What are stock and scion in grafting? Describe the process of grafting with its advantage.
Answer :
Out of two parts, the first one which has roots is obtained from a year-old fruit plant germinated from seed by cutting its upper part 20-30 cm from the ground, it is called stock. Another is a twig of a selected fruit plant having good quality and productivity. This part is called a scion.
Grafting – Scion should have a few nodes with or without a few half-cut leaves. The cut points of both parts are given appropriate shapes for fixing well. While selecting, cutting and joining them, we should keep in mind that there should be no disturbance in the internal conductivity between the stock and the scion. Grafting wax and plant tape are used to join them airtight. After a few days, the wounds heal, and both parts are joined firmly and become a single plant. This plant soon starts yielding having the same quality as the plant from which the scion was taken.
(g) What is layering? Draw a figure of layering with an example.
Answer :
Layering is an artificial vegetative propagation which is done to the plants having soft branches grows from the very lower part of the stem.
The branch selected for layering is called the layer. 2-3 cm of the bark of the layer is removed and then the part is bent down in the soil and covered with soil. The soil is kept moist until a new root system is grown from the buried part of the branch without bark, then, it is separated from the parent plant and sowed elsewhere.
(h) Write down the name of the method of asexual reproduction in the following organism Yeast, parameciun1, pineapple, banana, planaria, begonia, ginger, onion, sugarcane, mucor, sweet potato, spirogyra
Answer :
Yeast – Budding,
Paramecium – Fission,
Pineapple – Natural vegetative propagation through bulbils,
Banana – Natural vegetative propagation through suckers,
Planaria – Regeneration,
Begonia – Natural vegetative propagation through leaves,
Ginger – Natural vegetative propagation through rhizome,
Onion – Natural vegetative propagation through bulbils,
Sugarcane – Natural vegetative propagation through aerial stem,
Mucor – Fragmentation and sporulation,
Sweet potato – Natural vegetative propagation through root,
Spirogyra – Fragmentation.
(i) Artificial vegetative propagation is more important and beneficiary to everybody. Justify this statement including smne examples.
Answer :
(i) Artificial vegetative propagation is more important and beneficiary to everybody because,
(a) With this, the breed and genetics of plants can be directed as per need,
(b) With the artificial method, fast-yielding plants can be obtained,
(c) Many genetically identical saplings can be produced in a short period from a single parent plant,
(d) This technique is very useful for spreading plants which have no viable seeds.
Exercise 2 :
(1) Choose the best alternative from the given options :
(a) Where does fertilization take place in flowering plants?
(i) In stigma
(ii) In ovary
(iii) In ovule
(iv) In style
Answer :
Fertilization takes place – (ii) in ovary in flowering plants.
(b) What is called the pollination that is carried out by flies?
(i) Self-pollination
(ii) Cross-pollination
(iii) Pollen germination
(iv) Entomophily
Answer :
The pollination that is carried out by flies is called – (ii) cross pollination.
(c) Which of the following statement indicates the meaning of pollination?
(i) Pollination within the same flower
(ii) Pollination between two flowers
(iii) Pollination between genetically sin1ilar flowers
(iv) Pollination between genetically dissimilar flowers
Answer :
(ii) Pollination between two flowers – indicates the meaning of pollination.
(d) Which part is indicated by ‘B’ in the figure alongside?
(i) Pollen grain
(iii) Style
(ii) Pollen tube
(iv) Germinating pollen grain
Answer :
(ii) Pollen grain – is indicated by ‘B’ in the figure alongside.
(e) Which of the following animal adopt internal fertilization?
(i) Lizard
(ii) Frog
(iii) Sea-horse
(iv) Salamander
Answer :
(i) Lizard – adopts internal fertilization.
(f) Which of the statements are true regarding fertilization?
(i) Generally, the ovary changes into fruit and the ovule changes into a seed after fertilization
(ii) In some plants, the ovary changes into the fruit without fertilization
(iii) Firsts fertilization occurs in the stigma and second in the ovary
(IV) Fertilization occurs at first and then gametogenesis happens to make a zygote.
(i) i and iii
(ii) i and ii
(iii) i and iv
(iv) all statements
Answer :
(ii) i and ii – are true regarding fertilization.
(f) Which sequence is true regarding pollination in flowering plants?
(i) anther, stigma, pollen grain, pollen tube
(ii) anther, pollen grain, stigma, germination
(iii) pollen tube, pollen grain, style, anther
(iv) pollen grain, anther, pollen tube, stigma
Answer :
(ii) Anther, pollen grain, stigma, germination – is true regarding pollination in flowering plants.
(2) Differentiate :
(a) Pollination and Fertilization
Answer :
Pollination and Fertilization :
(i) Transferring pollen grains onto the stigma of the same flower or different flowers of the same species is called pollination. On the other side, the fusion of male gamete with a female gamete of the same species is called fertilization.
(ii) Pollination takes place in stigma in the flowering plants. On the other side, fertilization occurs inside the ovary in flowering plants.
(b) Gametes and Zygote
Answer :
Gametes and Zygote : Gametes are reproduction cells which used in sexual reproduction to produce a zygote. On the other hand zygote is the first cell of a new body to be born.
(c) Anther and Pollen grain
Answer :
Anther and Pollen grain : Anthers are the part of flowers which produce pollen. On the other hand, the powder-like things that are produced in the pollen sacs within anthers.
(d) Autogainy and Geitonogainy
Answer :
Autogamy and Geitonogamy : If pollen grains are transferred onto the stigma of the same flower it is called autogamy but if it is transferred onto the stigma of different flowers of the same plant, it is called geitonogamy.
(e) External fertilization and Internal fertilization
Answer :
External fertilization and internal fertilization:
(i) External fertilization takes place outside the body of the female in the outer environment. But internal fertilization takes place inside the female body at the end of mating.
(ii) In external fertilization, the female lays many eggs in water or on substratum without mating and then after, the male releases sperm over the eggs to fertilize them. But in internal fertilization, the fusion of sperm and an ovum takes place inside the fallopian tube of a female.
(3) Give reason :
(a) Pollinating agents have a great role in pollination.
Answer :
Pollinating agents have a great role in pollination because transferring of pollen grains of a flower onto the flowers of different plants of the same species is carried out by pollinating agents.
(b) Both male and female organisms are required for sexual reproduction.
Answer :
Both male and female organisms are required for sexual reproduction.
(c) External fertilization takes place either in water or on land.
Answer :
External fertilization takes place either in water or on land because in this method, fertilization takes place outside the body of the female in the outer environment.
(4) Answer the following questions :
(a) What is pollination? Give an example.
Answer :
Transferring pollen grains of a flower onto the flowers of different plants of the same species is called pollination. Example – Lily adopt self-pollination.
(b) Compare the self-pollination and cross-pollination with diagrams and mechanisms.
Answer :
Self-pollination and cross-pollination:
(i) Transferring pollen grains of a flower onto the flowers of different plants of the same species is called self-pollination. On the other hand, transferring pollen grains of a flower onto the flowers of different plants of the same species is called cross-pollination.
(ii) Self-pollination mostly occurs in small, colorless or dull flowers without nectar and fragrance. But cross-pollination usually occurs in colorful and well-scented flowers having nectar.
(iii) Self-pollination may not require pollinating agents. On the other hand pollinating agents play a vital role in cross-pollination.
(c) What is meant by double fertilization? Describe the process in brief.
Answer :
In fertilization, after making zygote, the remaining male gamete fertilizes with a secondary polar nucleus and an antipodal cell forming an endospermic nucleus. In this way, there will be double fertilization in flowering plants.
(d) Draw a neat and labelled diagram of an ovum and a spern~.
Answer :
(e) ‘Four puppies were born at a home,’ Which type of reproduction is this? Describe the importance of gametes in sexual reproduction.
Answer :
‘Four puppies were born at a home,’ this is sexual reproduction.
Gametes are reproduction cells which used in sexual reproduction to produce a zygote. Both males and females have special organs to produce male and female gametes. Example – the male has testes to produce sperm and the female has ovaries to produce eggs or ova.
(f) Make a graphical chart showing sexual reproduction in animals.
Answer :
The process of producing gametes in the testes and ovaries is called gametogenesis. In animal, gametogenesis takes place in testes and ovaries and in plant, this process takes place in anthers and ovary.
(g) What is gametogenesis? In which part of plants and animals does this process take place?
Answer :
The process of producing gametes in the testes and ovaries is called gametogenesis. In animal, gametogenesis takes place in testes and ovaries and in plant, this process takes place in anthers and ovary.
(h) Name the type of fertilization in given animals : Human, Pigeon, Tortoise, Butterfly, Fish, Bat, Frog, Cow, Dragonfly. Whale.
Answer :
Human – Internal fertilization, Pigeon – Internal fertilization, Tortoise – Internal fertilization, Butterfly – Internal fertilization, Fish – External fertilization, Bat – Internal fertilization, Frog – External fertilization, Cow – Internal fertilization, Dragonfly – Internal fertilization, Whale – External fertilization.
(i) What effects would occur if there is no sexual reproduction in plants and animals? Clarify with a suitable example.
Answer :
If there is no sexual reproduction in plants and animals, then plants and animals will die and become extinct. Example – If tigers die without reproducing their babies, then the tiger species will become extinct.
(i) ‘If there is no pollination in plants, fertilization will be nearly impossible’ Justify this statement with logic.
Answer :
‘If there is no pollination in plants, fertilization will be nearly impossible’ – This is because, if there is no pollination in the plants, then the nucleus present in pollen grains (male gamete) cannot enter into the ovule and the fertilization of the egg nucleus of the ovule (female gamete) cannot occur which results in no formation of zygote .
(k) ‘Internal fertilization is safer than external fertilization’. How?
Answer :
‘Internal fertilization is safer than external fertilization’ – this because in internal fertilization, gametes are protected from the outside environment which leads high survival rates more than external fertilization.
(l) How to do ‘fragrance in flower’ and the ‘different time for anther and stigma to be matured’ assure the pollination process? Describe in brief.
Answer :
Self-pollination mostly occurs in small, colorless or dull flowers without nectar and fragrance, on the other hand, cross-pollination usually occurs in colorful and well-scented flowers having nectar and in which androecium and gynoecium mature at different times. So, this is how ‘fragrance in flower’ and ‘different time for anther and stigma to be matured’ assure the pollination process.
(m) Study the given diagram of a flower and answer the following question:
(i) Label A, B C and D parts of a flower.
(ii) What effect may occur in the fertilization process if part B is removed?
Answer :
Exercise 3 :
(1) Choose the best alternative from the given options :
(a) Which method does thatch-grass (Khar) adopt to disperse their seeds?
(i) through air
(iii) by bursting pods
(ii) through water
(iv) by birds
Answer :
Thatch-grass disperses their seeds – (i) through air.
(b) What is the main function of a seed?
(i) to determine fruit
(ii) to produce a new plant
(iii) to continue their race
(iv) to preserve nutrients
Answer :
The main function of a seed is – (ii) to produce a new plant.
(c) Which of the following event occurs during germination?
(i) Plumule and radicle become active and make cotyledon.
(ii) Endosperm is turned into the root syste1n.
(iii) Stem is grown from the seedcoat.
(iv) Cotyledons turn into embryonic leaves.
Answer :
(iv) Cotyledons turn into embryonic leaves – during germination.
(d) Which of the following figure indicates seedling?
(i) A
(ii) B
(iii) c
(iv) D
Answer :
(iii) C – indicates seedling.
(e) Why are seeds not stored in moist or wet places?
(i) to prevent the decaying of seeds
(ii) to store seeds for a long time
(iii) to prevent seeds from fungal attack
(iv) to prevent germination
Answer :
Seeds are not stored in moist or wet places – (iv) to prevent germination.
(f) Which statement regarding the ‘dormancy’ is correct?
(i) it preserves the life and germination potential of seeds.
(ii) it preserves nutrients in seeds.
(iii) it protects seeds from air and water.
(iv) it conducts biochemical reactions during the germination of seeds.
Answer :
(i) it preserves the life and germination potential of seeds – is correct regarding the ‘dormancy’.
(f) Seeds of red silk cotton trees, Aak trees, Kans, maple etc which are dispersed through wind have either air sacs or wing-like structures. How do these structures help them to be dispersed?
(i) these structures protect the seed from a strong current of air and are (dispersed.
(ii) these structures help seeds to burst when they are fully ripened.
(iii) these structures help seeds to be exposed to fruits and then dispersed.
(iv) theses structures decrease the density of seeds and help them float in the air while dispersing.
Answer :
(iv) these structures decrease the density of seeds and help them float in the air while dispersing.
(2) Differentiate :
(a) Dispersal of seeds and Germination of seeds
Answer :
Dispersal of seeds and Germination of seeds: Reaching of seeds from their origin to different places through the help of any one of the carriers is called dispersal of seed. On the other hand, the development of a new root and shoot system of a new plant from a seed is called germination.
(b) Plurnule and Radicle
Answer :
Plumule and Radicle: During germination, the plumule develops into the shoot system. On the other hand the radicle develops into the root system.
(c) Dispersal of mustard seeds and Dispersal of myrica seeds.
Answer :
Dispersal of mustard seeds and Dispersal of myrica seeds: Mustard seeds are dispersed by bursting of pods but myrica seeds are dispersed by animal.
(3) Give reason:
(a) Seeds start germinating if soaked in water.
Answer :
Seeds start germinating if soaked in water because when they are soaked in water, the cells of the seed absorb plenty of water they break their dormancy, become active and start metabolism which initiates germination.
(b) Seeds of red silk cotton are dispersed over a long distance.
Answer :
Seeds of red silk cotton are dispersed over a long distance because it is dispersed through air and travelled long distance.
(c) Seeds continue the race of generation.
Answer :
Seeds continue the race of generation as germination of seed results in the production of a new generation of plants.
(4) Answer the following questions :
(a) What is a seed? Give examples.
Answer :
Seed is a part of the life cycle of flowering plants which can germinate into new plants of their kind. Example – rice, soybean, coconut, walnut.
(b) Write the methods of dispersal of seeds and explain any one of them with a figure and example.
Answer :
The methods of dispersal of seeds are, dispersal through wind, dispersal through water, dispersal by animals, dispersal by gravity, dispersal by bursting of pods.
Dispersal through water – Seeds of hydrophytes, plants that grow at river banks and wetlands are dispersed through water. Such seeds are water-proof, light and floating type. When their fruits ripen and fall in the water, they are carried by water up to distant places. Lotus, lily, Mangrove, Coconut, cattail etc are dispersed running or moving through water.
(c) What is meant by seed dormancy? How does it help seeds?
Answer :
The state in which the seed remains unchanged without any process of germination is called seed dormancy.
Dormancy preserves the life and germination potential of seeds.
(d) Explain the germination process of seeds with a suitable diagram.
Answer :
The development of a new root and shoot system of a new plant from a seed is called germination. If a seed is provided plenty of moisture, oxygen and suitable temperature, it absorbs moisture and due to starting of a bio-chemical reaction inside the seed cells, the embryo becomes active. The Radicle of the seed first starts to germinate into the root system which is followed by the germination of plumule into the shoot system and cotyledons turn into embryonic leaves.
(e) What is the role of air in the germination of seeds?
Answer :
Role of air in the germination of seeds – For the germination of seed, oxygen is essential. Oxygen generates energy in mitochondria which is necessary for their germination. During dormancy, cells of the seed are not breathing, not consuming nutrients and not generating any energy.
(f) Mention the importance of the germination of seeds in points.
Answer :
The importance of the germination of seeds –
(i) As germination of seed results in the production of a new generation of plants, it is very necessary for the continuation of their race.
(ii) Proper germination of seeds in farming increases productivity which is beneficial for farmers, consumers and the nation.
(iii) Germinating seeds contain more nutrients than normal seeds, so it is better to let the seeds germinate before they are consumed.
(iv) Proper germination of seeds of grass and trees in forests and pastures assists to conserve biodiversity.
(g) Read the given passage and answer the following questions:
Suryanaraya dug his field well with a tractor to sow wheat and put compost manure. The next day he sowed wheat and dug the field once again which helped to bury all seeds in the soil. After a few days. he went to the field to observe the condition. At the moistened part, the seedling was good but at the dry part, germination and seedling were not uniform
(i) Why did Suryanarayan again dig the field after sowing wheat?
(ii) What may be the reason for seeds not germinating inthe dry part of the field?
(iii) What should be done for proper seedlings at every corner of the field?
Answer :
(i) Surya Narayan dug the field again after sowing wheat because it helped to bury all seeds in the soil.
(ii) The reason for seeds not germinating in the dry part of the field may be there is no metabolic activity in dry seeds.
(ii) For proper seedlings at every corner of the field, seeds should be soaked in water 24 hours before their sowing.
(h) Name the method of dispersal for the given seeds :
Mango, chestnut, maple, gram, cobblers pegs (Kuro), sesame seed (Teel), pumpkin, coconut, pear.
Answer :
Mango – Dispersal by gravity, Chestnut – Dispersal by bursting of pods, Maple – Dispersal through the wind, Gram – Dispersal by air, Cobblers pegs – Dispersal by animals, sesame seed – , Pumpkin – Dispersal by animals, Coconut – Dispersal through the water/ Dispersal by gravity, Pear – Dispersal by animals.
(i) Study the given figure and answer the following questions:
(i) Name the parts A. B, C, D, E and G.
(ii) While germinating, what is developed from part A?
(iii) Do all seeds have part G? What does this part do?
Answer :
(a) Names of A – Plumule, B – Micropyle, C -, D -, E – Radicle, G – Cotyledon.
(b) While germinating, the shoot system developed from part A.
(c) All seeds do not have part G. This part protects the embryo.
(j) ‘Consuming germination seeds is more beneficial than normal dry seeds’. Clarify this statem.ent with logic.
Answer :
‘Consuming germination seeds in more beneficial than normal dry seeds’ – Because germinating seeds contain more nutrients than normal seeds.
More Solutions :
👉 (2) Information and Communication Technology
👉 (3) Living Beings and Their Structure
👉 (4) Biodiversity and Environment
👉 (8) Electricity and Magnetism
