MOECDC Class 8 Living Beings and Their Structure
| Board | Government of Nepal. |
| Class | Eight (8). |
| Subject | Science and Technology. |
| Chapter | Living Beings and Their Structure |
| Topic | Exercise Solve / Question Answer / Notes. |
Exercise 1 :
(1) Select the correct option from the followings:
(a) What is called the branch of science that deals with the study of the cell?
(i) Histology
(ii) Cytology
(iii) Cytogenetics
(iv) Anatomy
Answer :
(ii) Cytology – is called the branch of science that deals with the study of the cell.
(b) In which form is the energy generated in a cell stored before it is distributed to organelles?
(i) DNA
(ii) RNA
(iii) RBC
(iv) ATP
Answer :
The energy generated in a cell stored before it is distributed to organelles in – (iv) ATP form.
(c) What is the common feature of the nuclear membrane and cell membrane?
(i) they help in internal transportation
(ii) they are composed of Pectin
(iii) they are non-elastic in nature
(iv) they inherit heredity to offspring
Answer :
The common feature of the nuclear membrane and cell membrane is – (i) they help in internal transportation.
(d) What is indicated by ‘R’ in the given figure?
(i) Nucleus
(ii) Chloroplast
(iii) Mitochondrion
(iv) Vacuole
Answer :
(iv) Vacuole – is addicted by ‘R’ in the given figure.
(e) Which of the following function is done by both plant and animal cells?
(i) Photosynthesis
(ii) Cellular respiration
(iii) Transpiration
(iv) Guttation
Answer :
(ii) Cellular respiration– is done by both plant and animal cells.
(f) What would happen if there was no cell membra
(i) cell organelles would be lost.
(ii) cellwould die
(iii) cell couldn’t conduct metabolism iv) nucleus would be lost
(iv) nucleus would be lost
Answer :
If there was no cell membrane – (iii) cell couldn’t conduct metabolism.
(g) Which of the following is a function of the nucleus for the growth and development of the body?
(i) to synthesize protein
(ii) internal transportation of cell
(iii) to take part in cell division
(iv) to control and coordinate all the functions of cell
Answer :
(iv) to control and coordinate all the functions of cell– is a function of the nucleus for the growth and development of the body.
(2) Differentiate:
(a) Cytoplasm and Nucleoplasm
Answer :
Cytoplasm and Nucleoplasm – Cytoplasm is viscous, sticky, clear semi-liquid and compose of water, soluble salts, minerals, proteins, vitamins. On other hand, nucleoplasm is a liquid solution of water, amino acids, minerals, nucleic acids and enzymes.
(b) Chloroplast and Chromoplast
Answer :
Chloroplast and Chromoplast –
(i) Chloroplast is green-colored plastid but chromoplasts are all colorful plastids, except green.
(ii) Chloroplasts are generally round or oval in shape but chromoplasts are somewhat flat in shape.
(c) Cell wall and Cell membrane
Answer :
Cell wall and Cell membrane –
(i) The cell wall is found only in bacterial, fungal and plant cells, it is absent in most of the protozoans and animal cells. On other side, the cell membrane is the outermost layer of the cells of animal and protozoans, but in bacterial, fungal and plant cells, it lies just beneath the cell wall.
(ii) The cell wall is generally a tough, rough, semi-elastic and nonliving substance. But the cell membrane is comparatively much smoother and elastic than the cell wall and it is a living substance.
(d) Cell organelles and Cell inclusions
Answer :
Cell organelles and Cell inclusions –
(i) Cell organelles are living sites but cell inclusions are non-living things.
(ii) Cell organelles performs specific metabolic activities which are essential for life process. On other side, cell inclusions act as raw materials and sources of energy generation which are used by various cell organelles for metabolic activities.
(3) Give reason:
(a) Ribosomes are also called ‘protein factories.
Answer :
Ribosomes are also called ‘protein factories’ – Ribosomes synthesize protein from different amino acids. Therefore, ribosomes are also called protein factories.
(b) Cell wall provides a fixed shape to plant cells.
Answer :
Cell wall provides a fixed shape to plant cells – Plant cells have cell wall which is generally tough, rough, semi-elastic and nonliving substance. It provides plant cells mechanical support and fixed shape.
(c) Metabolism occurs in the cytoplasm
Answer :
Metabolism occurs in the cytoplasm – Metabolism occurs in the cytoplasm because metabolic activities of life process are accomplished within the cytoplasm.
(d) Cell is considered as the basic unit of life.
Answer :
Cell is considered as the basic unit of life – Cell is considered as the basic unit of life because all the mechanisms of life processes like digestion, respiration, reproduction, internal transpiration, photosynthesis etc are accomplished inside or by the action of cells through biochemical reactions and contraction-relaxation motion.
(e) There should be proper coordination among cells, tissues and organs to conduct the life process.
Answer :
There should be proper coordination among cells, tissues and organs to conduct the life process – There should be proper coordination among cells, tissues and organs to conduct the life process because cells, tissues, organs and organ systems are interrelated to each other for the construction and functioning of the body of organisms.
Answer the following questions:
(a) What is a cell?
Answer :
The cell is the structural as well as functional units of life.
(b) Draw a labelled diagram of plant and animal cells.
Answer :
(c) Where are the mitochondria located in a cell? Write their functions.
Answer :
The mitochondria are located in cytoplasm.
Their functions are –
(i) The main function of mitochondria is to generate energy for the survival of the cell.
(ii) Mitochondria contain some DNA molecules which transfer hereditary character.
(d) Which organelle of the cell undergoes self-digestion and why?
Answer :
Lysosome undergoes self-digestion. It is because when the level of the lysosomal enzyme becomes high, the organelle itself is digested
(e) Make a list of cell organelles and cell inclusions found in a cell.
Answer :
The list of cell organelle – Mitochondria, Plastid, Ribosome, Endoplasmic Reticulum, Golgi body, Lysosome, Vacuole.
The list of cell inclusions – Droplets of free water, crystals of salts and minerals, enzymes, hormones, vitamins and waste materials excreted by the cell.
(f) Mention the function of plastids in a plant cell.
Answer :
The function of plastids in a plant cell –
(i) Plastid like chloroplast makes plants green.
(ii) Plastid like chromoplasts make flowers colorful.
(iii) Plastid like leucoplast stores starch, protein and fat for future use.
(g) Complete the Venn diagram by comparing plant and animal cells.
Answer :
(h) Mention the role of the Golgi body and Vacuole in a cell.
(i) Study the given figure carefully and answer the following questions:
(i) Copy this figure in your exercise book and label ‘A’, ‘B’, ‘C’, ‘D’
(ii) What is the function of ‘B’?
(iii) What happens if there is no nucleus in a cell?
Answer :
The role of Golgi body in a cell –
(i) Golgi body helps to secrete gum, mucus, sweat, saliva, tear etc.
(ii) During cell division, the Golgi body contributes to making new cell membranes and new cell-plate.
(iii) Golgi body also helps in the internal transportation of cells and sorting of proteins.
The role of vacuole in a cell –
(i) Vacuoles balance the amount of water and salts in the cytoplasm.
(ii) It collects metabolic wastes of organelles before they are excreted out of the cell membrane.
(j) Among various organelles of a cell, which one is the most important in your opinion and why?
Answer :
In my opinion, among various organelles of a cell, mitochondria is the most important because it act as ‘power-houses’ of cells without which cells cannot survive.
(k) What would happen in the plants’ life processes if there were no chloroplasts in them?
Answer :
If there were no chloroplasts in plants, then plants could not have made their food and they would have died.
(l) What is the reason that the nucleus is also called ‘the brain of cells”? Clarify.
Answer :
The nucleus is also called ‘the brain of cells’ because nucleus controls and coordinates the function of every cell organelle.
(m) If there were no metabolic processes in a cell, what effect would occur in the life processes of the organism?
Answer :
If there were no metabolic processes in a cell, then cell would have died as every metabolic process is essential to survive.
Exercise 2 :
(1) Select the best answer from the given alternatives:
(a) Who proposed the “Two kingdom system’ of classification?
(i) Whittaker
(ii) Haeckel
(iii) Linnaeus
(iv) Aristotle
Answer :
(iii) Linnaeus– proposed the ‘Two kingdom system’ of classification.
(b) To which kingdom do protozoans belong according to the ‘Five Kingdom system”?
(i) monera
(ii) protista
(iii) mycota
(iv) animalia
Answer :
Protozoans belong to (ii) Protista– kingdom according to the ‘Five kingdom system’.
(c) Why are bacteria called decomposers?
(i) they cause diseases
(ii) they infect wounds
(iii) they survive in extreme environment
(iv) they decay dead bodies and excreta of organisms
Answer :
Bacteria are called decomposers because – (iv) they decay dead bodies and excreta of organisms.
(d) Which virus causes COVID-19?
(i) SARS COV-1
(ii) SARS COV-2
(iii) Corona virus
(iv) Flu virus
Answer :
(iii) Corona virus – causes COVID-19.
(e) What is the main thing to be followed while preserving foodstuffs?
(i) to prevent germs
(ii) drying well
(iii) to prevent from decaying of food
(iv) keeping cold
Answer :
(i) To prevent germs– is the main thing to be followed while preserving foodstuffs.
(f) Which of the given is a feature of the ‘Five Kingdom system’?
(i) Classified according to phylogenetic order.
(ii) Classified based onthe mode of nutrition and lifecycle.
(iii) Classified based on chlorophyll and growth.
(iv) Classified based onthe movement of the body.
Answer :
(i) Classified according to phylogenetic order– is a feature of the ‘Five kingdom system’.
(g) What should be done to preserve fresh and wet Gundruk
(fernrnnted veggies)?
(i) It should be dried extremely in sun.
(ii) It should be dried in shadow.
(iii) It should be dried maintaining the required percentage of inoisture.
(iv) It should be kept airtight in a bottle or a can.
Answer :
(iii) It should be dried maintaining the required percentage of moisture – to preserve fresh and wet Gundrunk.
(2) Differentiate :
(a) Bacteria and Virus
Answer :
Bacteria and Virus:
(i) Bacteria are unicellular but virus has no cell.
(ii) Bacteria are living organisms but virus shows the characteristics of both living and non-living things.
(b) Two kingdom system and Five kingdom system
Answer :
Two kingdom system and five kingdom system:
(I) In Five Kingdom System, unicellular and multicellular organisms are kept in separate kingdoms. But Two Kingdom System does not separate them.
(II) In Five Kingdom System, prokaryotes and eukaryotes are also separated. But in Two Kingdom System, prokaryotic bacteria and eukaryotic algae are kept in same kingdom.
(3) Give Reason :
(a) Virus is called a very sniall infectious particle but not an organism.
Answer :
Virus is called a very small infectious particle but not an organism because it has no cell therefore it does not belong to any kingdom.
(b) We should not consume stale and s1nelly food.
Answer :
We should not consume stale and smelly food because microorganisms like Clostridium bacteria enter into such food through air, water or any medium and make the toxic substance. If such contaminated food is consumed then we will suffer from diarrhea, vomiting, fever, dehydration, dry mouth, headache etc.
(c) Five kingdom system has provided an appropriate position to almost all organisms.
Answer :
Five kingdom system has provided an appropriate position to almost all organisms because in this system organisms are arranged in sequential form from least developed to more developed which also refers to the trend of organic evolution.
(d) Fruits do not get spoiled if preserved after drying well.
Answer :
Fruits do not get spoiled if preserved after drying well. Because of dryness, microorganisms cannot affect fruits and due to certain moisture the nutritional value of fruits is maintained and they can be stored at room temperature for a long time.
(4) Answer the foil owing questions :
(a) What is a inicroorganism? Give an exainple from each category.
Answer :
The microscopic organisms that are found in air, water, soil, unsaved food, dirt and on/in the body of living dead and decaying organisms, are called microorganisms. Example – Entamoeba Histolytica, yeast, rhizobium, coronavirus.
(b) What are the methods of food preservation? Describe any one method and also mention the importance of food preservation.
Answer :
The methods of food preservation are dry preservation, wet preservation and cold preservation.
The importance of food preservation is, with preservation, the nutritional value of the foodstuffs can be conserved and they can be kept safe from infectious microorganisms.
Dry preservation – This technique prefers a moderate temperature between 20-30 Celsius for some days either in sun or in an oven or electric dryer until the foodstuffs are completely dry externally and keep very less moisture internally. Because of dryness, microorganisms cannot affect fruits and due to certain moisture the nutritional value of fruits is maintained and they can be stored at room temperature for a long time.
(c) What is foodpoisoning? Mention its causes and the measures to be safe from it.
Answer :
Microorganisms like Clostridium bacteria enter into stale and smelly food through air, water or any medium and make the toxic substance. If such contaminated food is consumed then we will suffer from diarrhea, vomiting, fever, dehydration, dry mouth, headache etc. Such conditions due to contaminated food are called food poisoning.
Food poisoning causes diarrhea, vomiting, fever, dehydration, dry mouth, headache etc.
The measures to be safe from food poisoning are, we should not consume stale and smelly food and foods should be kept covered.
(d) Why is the Five Kingdom System more advanced than the Two Kingdom System?
Answer :
The Five Kingdom System is more advanced than the Two Kingdom System because in Five Kingdom System, organisms are arranged in sequential form from least developed to more developed which also refers to the trend of organic evolution, unicellular and multicellular organisms are kept in separate kingdoms, prokaryotes and eukaryotes are also separated and autotrophic and heterotrophic organisms are kept in plantae, Animalia and mycota kingdoms respectively. While in Two Kingdom System, all living beings are divided into only plant and animal kingdoms. In fact, the living beings which cannot conduct photosynthesis also kept in the same section of plant kingdom. Two kingdom system is not able to include organisms like Lichens.
(e) Make a list of any two diseases caused by each category of microorganism.
Answer :
Virus causes COVID-19, common cold.
Bacteria causes typhoid, pneumonia.
Amoeba causes amoebiasis dysentery,
Fungus causes fungal eye infection, sporotrichosis.
(f) What are the common words for microorganisms?
Answer :
The common words for microorganisms are ‘germs’, ‘microbes’.
(g) What is Classification? How does classification make the study of organisms easier?
Answer :
When living beings differ from each other by their habitat, mode of nutrition, type of reproduction they have adopted, physical structures, is called classification.
Classification makes the study of organisms easier. Classification imparts knowledge about the trend of organic evolution on Earth. It also helps us to identify the various organisms correctly and to understand how organisms are related and their benefits and negative effects.
(h) Write any four advantages of microorganisms.
Answer :
Four advantages of microorganisms are,
(i) Some amoeba feeds on bacteria, so they are used to control bacteria.
(ii) Distilleries use yeast to ferment foodstuffs to produce alcohol and acids.
(iii) To develop the products of medical science like insulin, antibiotics, vaccines, vitamins etc, bacteria and fungi are used.
(iv) In genetic engineering, many viruses are being used to replace, transfer, repair and synthesis of genes to develop high-yielding plants and animals.
(i) Mention the merits and drawbacks of the Two kingdom system.
Answer :
(i) The merits of Two Kingdom System are,
(a) All living beings are divided into plant and animal kingdoms.
(b) This is the first scientific system of classification of living beings.
(c) It is simple by which plants and animals can easily be distinguished.
(ii) The drawbacks of the Two Kingdom System are,
(a) The living beings which cannot conduct photosynthesis also kept in the same section of plant kingdom.
(b) Prokaryotic bacteria and Eukaryotic algae are kept in the same kingdom.
(c) Two kingdom system does not separate unicellular and multicellular organisms.
(d) Two kingdom system is not able to include organisms like Lichens.
(j) Mention the basis and features of the Five Kingdom system.
Answer :
The basis of Five Kingdom System : Based on types of cell, body structure, mode of nutrition, role in the ecosystem and phylogenetic relationship, Whittaker has divided all the known organisms into five kingdoms. Here, all the unicellular prokaryotes are kept under the kingdom Monera. All unicellular eukaryotes except free-living fungal cells are kept under the kingdom Protista. All saprophytic and parasitic fungi that exhibit extracellular digestion are kept under the kingdom Fungi or Mycota. All autotrophic green organisms are kept under the kingdom Plantae and multicellular eukaryotic consumers are kept under the kingdom Animalia.
The features of Five Kingdom System :
(a) Unicellular and multicellular organisms are kept in separate kingdoms.
(b) Prokaryotes and eukaryotes are also separated.
(c) Autotrophic and heterotrophic organisms are kept in Plantae, Animalia and Mycota kingdoms respectively.
(d) In this system organisms are arranged in sequential form from least developed to more developed which also refers to the trend of organic evolution.
(k) Study the given figure and answer the following questions:
(i) What are shown in the figure?
(ii) Name a disease caused by it and two preventive nleasures for the disease.
Answer :
(i) These are the figure of Corona virus.
(ii) COVID-19 is caused by it. Two preventive measures for the disease are, cover our mouth and nose with mask and avoid crowds or maintain physical distance in the crowd.
(l) Two kingdoms system has not differentiated prokaryotes and eukaryotes, how is this corrected by Five kingdom system? Describe in brief.
Answer :
Two kingdoms system has not differentiated prokaryotes and eukaryotes. But this is corrected by the five kingdom system. Here, all the unicellular prokaryotes are kept under the kingdom Monera. All unicellular eukaryotes except free-living fungal cells are kept under the kingdom Protista.
(m) How is amoeba being used by mankind for beneficiary purposes?
Answer :
Some amoeba, like Amoeba proteus feed on bacteria, so they are used to control bacteria.
(n) Fungus sometimes grows in pickles kept in a bottle or jar. Why does it happen? What should be done to protect pickles from fungal attacks?
Answer :
Fungus sometimes grows in pickles in a bottle or jar. It may happen because of humid weather condition or if we store pickles improperly for a long time or we use wet spoon in it. Then fungus react with the fats and oils of pickle.
To protect pickles from fungal attacks, we should keep pickles in the glass jars instead of plastic containers. The glass jars should be washed thoroughly and dried in sunlight.
More Solutions :
👉 (2) Information and Communication Technology
👉 (4) Biodiversity and Environment
👉 (8) Electricity and Magnetism
