Detergent We use a variety of detergents to wash clothes. Detergent is a synthetic petrochemical having more cleansing action than the soap. It is obtained from hydrocarbon. It is more soluble in water than a soap. Detergent does not contain chemicals found in soap but it has a cleansing action better than soap. So it is called a soapless soap. Examples: Sodium lauryl sulphate (C12H25SO4–Na+), sodium pyrophosphate, alkyl benzene sulphonate, etc. Detergents are suitable to wash clothes though water is hard. It is because the calcium and magnesium present in detergent dissolve in water. Detergents are non-biodegradable. So they cause environment pollution. Differences between soap and detergent Soap Detergent 1. Soap is a sodium or potassium salt of 1. Detergent is synthetic petrochemical higher fatty acid. having cleansing properties. 2. It is biodegradable. 2. It is non-biodegradable. 3. It is not suitable to wash clothes with 3. It is suitable to wash clothes with hard hard water. water. Compost manure or compost fertilizer The organic manure produced by decaying various parts of plants and animal wastes is called compost manure. It is added to the soil to increase the fertility of the soil. Fertilizers are the substances that increase the fertility of soil. Fertilizers are of two types. They are organic fertilizers and chemical fertilizers. Compost manure is called an organic fertilizer because it is produced by decaying parts of plants and animal wastes. Chemical fertilizers are produced from minerals. Organic fertilizers are of two types. They are green manure and compost manure. Green manure is produced by decaying various parts of plants where as compost manure is prepared by decaying parts of plants and animal wastes. Some bacteria convert atmospheric nitrogen into nitrates and increase the fertility of soil. Organic fertilizers do not contain all elements required for growth and development of plants. So we should add chemical fertilizers to the soil to increase the productivity of crops. Role of compost fertilizer 1. The plants grown by using compost fertilizers grow well and produce good fruits. 2. They preserve water content in the soil. 3. They do not cause environment pollution. 4. They prevent leaching and soil erosion. 5. They do not increase or decrease acidity or alkalinity of soil. GREEN Science (Chemistry) Book-10 251
6. They are biodegradable. 7. They do not have negative impacts on atmosphere. Chemical Fertilizers The chemical substances which are used to increase the fertility of soil are called chemical fertilizers. They are rich in minerals that are essential for the growth and development of plants. Fig.13.9 Fig. Organic fertilizer Chemical fertilizer Organic fertilizers are prepared by using dead and decaying parts of plants and animals. They do not affect the quality of soil. Chemical fertilizers are prepared by using different chemicals or minerals. Prolonged use of chemical fertilizers affects the fertility and quality of soil. Therefore, over use of chemical fertilizers should be avoided. Green plants mainly require three types of chemicals, viz. nitrogen (N), phosphorus (P) and potassium (K). So chemical fertilizers are prepared by using nitrogen, phosphorus and potassium. On the basis of presence of minerals, Do You Know chemical fertilizers are of three types. They are: The fertilizer containing nitrogen, phosphorus and potassium is called NPK i. Nitrogenous fertilizers fertilizer. It is called a complete fertilizer. ii. Phosphorus fertilizers iii. Potassium fertilizers i. Nitrogenous fertilizers The chemical fertilizers rich in nitrogen are called nitrogenous fertilizers. They help in growth of plants. They help in growth and development of flowers, fruits and seeds. Urea, ammonium chloride, ammonium sulphate, etc. are the examples of nitrogeneous fertilizers. Due to deficiency of nitrogen in soil, plants become pale, flowers do not 13.10 bloom properly, fruits and seeds become small. 252 GREEN Science (Chemistry) Book-10
ii. Phosphorus fertilizers 13.11Fig. Fig. The chemical fertilizers rich in phosphorus are called phosphorus fertilizers. Ammonium phosphate, calcium super phosphate, bone meal, etc. are the examples of phosphorus fertilizers. These fertilizers help in growth of roots, leaves and buds, ripening of fruits and development of seeds. iii. Potassium fertilizers The chemical fertilizers rich in potassium are called potassium fertilizers. Examples: Potassium chloride, Potassium sulphate, etc. Potassium fertilizers help in photosynthesis, formation of protein and cell division. In the absence of potassium in soil, the immunity of plants decreases and leaves and buds of plants wither. 13.12 Insecticides Artificial poisonous chemicals that are used to kill or control harmful insects are called insecticides. They are toxic and non-biodegradable. They are poisonous for human beings and animals. Therefore, we should use insecticides having minimum residual effect as less as possible to control insects. The insecticides which are commonly used are as follows: i. DDT (Dichloro Diphenyl Trichloroethane ii. Malathion iii. Parathion iv. BHC (Benzene Hexachloride v. Aldrin vi. Dialdrin vii. Turmic viii. Baygon ix. Calcium arsenate x. Limesulphur, etc. Types of Insecticides On the basis of chemicals present, insecticides are of two types. They are as follows: 1. Inorganic insecticides 2. Organic insecticides 1. Inorganic insecticides The insecticides which are made from minerals are called inorganic insecticides. These insecticides do not contain carbon. Inorganic insecticides are used to protect fruits, vegetables, cotton, etc. from harmful insects. Lime sulphur, calcium arsenate, lead arsenate, fluoride, etc. are some examples of inorganic insecticides. GREEN Science (Chemistry) Book-10 253
2. Organic insecticides Organic insecticides are man-made carbon containing insecticides. These insecticides mainly contain carbon, hydrogen, oxygen and some other elements like chlorine, phosphorus, etc. There are three types of organic insecticides as follows: i. Chlorinated organic insecticides They are organic insecticides having chlorine as an additional element. These insecticides are stable with long and broad effects. Their effect remains for a long time. Examples: i. DDT (Dichloro Diphenyl Trichloroethane ii. BHC (Benzene Hexa chloride) iii. Methoxychlor iv. Aldrin v. Dialdrin ii. Organophosphate insecticides They are organic insecticides having phosphorus as an additional element. They are highly toxic to human and other animals. However, they are less stable and biodegradable. Examples: i. Malathion ii. Parathion iii. Phosdrin, etc. iii. Carbamate Insecticides They are organic insecticides having amino-group. They are less harmful. Examples: i. Termic ii. Begon, etc. Advantages of Insecticides 1. They help to increase crop production by killing harmful insects. 2. They help in disease control by killing germs. 3. They help to kill household insects like cockroach, flies, etc. Disadvantages of Insecticides 1. Most insecticides cause environmental pollution as they are non-biodegradable. 2. Insecticides not only kill harmful insects but useful insects too. 3. Powdered insecticides affect human beings, animals, birds and plants. 4. Consumption of fruits and vegetables having insecticides cause serious diseases like cancer in human beings. Fibres The thread-like strong materials used for making clothes, ropes, nets, etc. are called fibres. They are mainly of two types. 1. Natural fibres 2. Artificial fibres 254 GREEN Science (Chemistry) Book-10
1. Natural fibres The fibres that are obtained from plants and animals are called natural fibres. Cotton, silk, wool and leather are some examples of natural fibres. Characteristics of natural fibres i. They retain body heat, not catching fire and absorb perspiration. ii. They are beautiful and classic in looks. Disadvantages of natural fibres i. They are very expensive. ii. They shrink when washed with water. iii. They take more time to dry after washing as they absorb more water. iv. Insects easily attack them. 2. Artificial fibres The man-made fibres are called artificial fibres. They are mainly of two types. a. Synthetic fibres The artificial fibres made by chemical processes are called synthetic fibres. Examples: nylon, terylene, terywool, etc. b. Recycled fibres The fibres made by recycling natural fibres are called artificial fibres. For examples, rayon is made from cotton cellulose and wood pulp. It looks like silk. So, it is called artificial silk. Characteristics of artificial fibres 1. Artificial fibres are strong and more convenient than natural fibres. 2. They are easy to wash and dry up quickly. 3. They are not attacked by insects. 4. They do not shrink on washing. 5. They are cheap and can be manufactured in a large amount. Chemical pollution We use a variety of chemical substances in our daily life. These chemical substances pollute the environment. The environment pollution caused by various chemical substances is called chemical pollution. Besides chemical Fig. substances, natural phenomena are also responsible for chemical pollution. 13.13 Chemical substances like plastics, Chemical pollution chemical fertilizers, insecticides, detergents, colours, synthetic cleansers, etc. cause chemical pollution. GREEN Science (Chemistry) Book-10 255
Causes of chemical pollution 1. Chemical fertilizers Though chemical fertilizers increase the productivity of crops, they also cause chemical pollution. Overuse of chemical fertilizers has many negative impacts in the environment. It pollutes soil, air and water. If the same chemical fertilizer is used continuously, the fertility of the fertilizer present in the soil cannot be absorbed by plants, which is washed by rain water. Ultimately the excess fertilizer reaches ponds, river, sea, etc. It causes water pollution. Aquatic plants grow well due to chemical fertilizers. They absorb the oxygen present in water. It decreases oxygen content in water. As a result, aquatic animals like fishes die due to lack of oxygen. When these animals decay in water, they also pollute the water. It adversely affects water ecosystem. 2. Automobiles and industrial wastes A variety of harmful chemicals are released in the atmosphere while operating automobiles and machines in industries. These harmful chemical include toxic gases like carbon monoxide, sulphur trioxide, hydrogen sulphide, nitrogen dioxide, and so on. They also release mercury and lead. When these gases combine with rain water, they cause acid rain. Acid rain affects physical and biological environment. It has many negative impacts on the environment. Greenhouse effect occurs due to increase in the amount of greenhouse gases like carbon dioxide in the atmosphere. It increases the temperature of atmosphere and causes global warming. As a result, polar ice melts which affects the people living in coastal regions. Polluted air has many negative impacts on human health. Human beings suffer from various diseases related to respiration. 3. Synthetic cleansers Different types of harmful chemicals are found in synthetic cleansers. Therefore, we should reduce the overuse of detergents and soaps. We should protect plants from water containing synthetic cleansers. 4. Plastics Now-a-days, the use of plastics is spreading throughout the world. Plastics are non- biodegradable materials. They do not rot and corrode and hence cause environment pollution. When we throw plastics, they cause land pollution and water pollution. When we burn them, they release toxic gases and cause air pollution. Therefore, we should recycle the plastics as far as possible. Similarly, we should reduce the production and use of plastics to reduce chemical pollution. 5. Colouring matter We use different types of colour in food items like tea, coffee, sweets, chocolate, etc. to make them attractive. However, most of the colours are not safe for human health. Consumption of unedible colours in food items adversely affects our health. They may cause various dangerous diseases like cancer. 256 GREEN Science (Chemistry) Book-10
6. Insecticides Insecticides are the chemical substances which are used for killing insects. Insecticides not only kill the targeted insects but also useful insects. It imbalances the ecosystem. Mixing of insecticides in environment causes pollution. The use of DDT affects the physical as well as biological environment. Polluted water due to insecticides affects aquatic animals. It affects the reproductive capacity of organisms. Insecticides affect the growth and fertility of fishes and birds. Birds lay unfertilized eggs. The outer cover of eggs become thin. Insecticides cause various diseases related to respiration. Therefore, we should reduce the use of insecticides like DDT, BHC, methoxychloride, aldrin, dialdrin, etc. Ways to get rid of chemical pollution Human being is the major cause of chemical pollution. Therefore, it is the duty of human beings to reduce chemical pollution. Following measures should be adopted to get rid of chemical pollution. 1. We should minimize the use of plastics. 2. Household biodegradable wastes should be used to produce compost manure. 3. We should reduce the over use of synthetic detergents, chemical fertilizers and insecticides. 4. We should recycle the plastic materials as far as possible. 5. We should minimize the use of chemical fertilizers and the chemical fertilizers should be used after testing the soil. 6. The harmful gases should be converted into harmless gases before releasing them in the air. 7. We should avoid the use of inedible colours in food items. 8. We should be careful while using insecticides. Biodegradable and non-biodegradable solid wastes and their management Biodegradable solid wastes are those wastes which get decomposed due to action of decomposers like bacteria and fungi. Wastes from plants and animals are the examples of biodegradable wastes. These wastes can be used to produce compost manure. Non-biodegradable solid wastes are those wastes which do not decompose due to action of decomposers. Different types of solid wastes from factories and industries, waste plastics, waste glasses, etc. are the examples of non-biodegradable wastes. These solid wastes should be managed properly according to their type. Some of them can be recycled and other can be either buried in landfill site or incinerated. Solid Waste Management Collection of wastes, transportation, processing and reuse of the waste materials are the major steps of solid waste management. Human beings and other animals suffer from various disease if solid wastes are not managed properly. Therefore, it is necessary to manage solid wastes properly. We should keep our surroundings neat and clean. We GREEN Science (Chemistry) Book-10 257
should separate biodegradable and non-biodegradable wastes before their management. We should dispose solid wastes properly. There is a great role of government as well as non-governmental agencies in solid waste management. The various steps of solid waste management are given below: i. Collection and transportation It is the first step of solid waste management. The solid waste produced in our houses and offices should be collected and kept in a fixed place. After collection, solid wastes should be transported away from residential areas for management. ii. Segregation and waste management After collection solid waste materials should be separated into biodegradable and non- biodegradable wastes. It makes management of solid wastes easier. iii. Processing and disposal Solid wastes should be transported after their processing. Biodegradable wastes should be used for making compost manure. It also helps to increase the productivity of crops. iv. Landfill dumping After processing, solid wastes materials should be collected in a dumping site. We should construct dumping site away from human settlement. The environment impact assessment should be done to select the dumping site. v. Incineration The solid wastes which cannot be recycled should be incinerated. Incineration is the process of burning solid wastes at about 1000°C. Incineration should be done away from human settlement and forests. Key Concepts 1. Cement is a fine gray powder made by grinding limestone (CaCO3) and special type of clay (Al2O3.SiO2). It is used in various construction works. 2. Crushing, grinding and finish grinding are the three steps involved in the manufacture of cement. 3. Glass is a solid and transparent industrial material. It is a super-cooled liquid because it flows downwards very slowly. 4. We prepare glass by heating the mixture of silica, sodium carbonate and potassium carbonate. 5. When silica is heated at about 1600°C, it melts. When it is cooled it forms a crystalline substance which is known as crystalline glass or silica glass. 6. Ordinary glass is the glass which is prepared by heating silica with sodium carbonate and calcium carbonate. 7. The glass which is prepared by heating silica with potassium carbonate and calcium carbonate is called hard glass. 8. The glass which is prepared by heating silica with sodium carbonate, calcium carbonate and boric oxide is called borosilicate glass. 258 GREEN Science (Chemistry) Book-10
9. The glass which is prepared by heating silica with potassium carbonate and lead monoxide is called lead crystal glass. 10. Coloured glasses are used for making window panes, spectacles, glasses of car, train, aeroplane, etc. They are also used for making decorative items. 11. The special type of clay which consists of compounds of carbon, nitrogen, oxygen and silica is called ceramics. 12. Glazing makes ceramic materials shiny, smooth, attractive and non-porous (water- proof). We can polish the ceramic materials to make them more attractive. 13. The man-made polymers which can be changed into various shapes are called plastics. They are made by heating monomers like ethene, vinyl chloride, etc. 14. When monomers are heated, they combine and form a long chain called polymer. The process of formation of polymer is called polymerization. 15. The plastic which becomes soft and flexible on heating and hard on cooling is called thermoplastic. 16. The plastic which becomes hard on heating and cannot be changed into different shapes is called thermosetting plastic. 17. A soap is a sodium or potassium salt of higher fatty acid. Sodium palmitate, sodium stearate, sodium oleate are the common examples of soap. 18. The process of making soap by heating animal fat or vegetable oil with sodium hydroxide and sodium chloride is called saponification. 19. Soap is not suitable to wash clothes with hard water as it forms a curdy precipitate which is insoluble in water. Soap is biodegradable. So, it does not cause environmental pollution. 20. Detergent is a synthetic petrochemical having more cleansing action than the soap. 21. Detergent does not contain chemicals found in soap but it has a cleansing action better than soap. So it is called a soapless soap. Examples: Sodium lauryl sulphate, sodium pyrophosphate, alkyl benzene sulphonate, etc. 22. The organic manure produced by decaying various parts of plants and animal wastes is called compost manure. It is added to the soil to increase the fertility of the soil. 23. The chemical substances which are used to increase the fertility of soil are called chemical fertilizers. They are rich in minerals that are essential for the growth and development of plants. 24. Green plants mainly require three types of chemicals, viz. nitrogen (N), phosphorus (P) and potassium (K). So chemical fertilizers are prepared by using nitrogen, phosphorus and potassium. 25. The environment pollution caused by various chemical substances is called chemical pollution. 26. Chemical substances like plastics, chemical fertilizers, insecticides, detergents, colours, synthetic cleansers, etc. cause chemical pollution. 27. Plastics are non-biodegradable materials. They do not rot and corrode and hence cause environment pollution. 28. Insecticides are the chemical substances which are used for killing insects. Insecticides not only kill the targeted insects but also useful insects. 29. Biodegradable solid wastes are those wastes which get decomposed due to action of decomposers like bacteria and fungi. Wastes from plants and animals are the examples of biodegradable wastes. GREEN Science (Chemistry) Book-10 259
30. Non-biodegradable solid wastes are those wastes which do not decompose due to action of decomposers. Different types of solid wastes from factories and industries, waste plastics, waste glasses, etc. are the examples of non-biodegradable wastes. 31. We should keep our surroundings neat and clean. We should separate biodegradable and non-biodegradable wastes before their management. 32. Incineration is the process of burning solid wastes at about 1000°C. Incineration should be done away from human settlement. Sequential General Exercise 1 1. Choose the best answer from the given alternatives. a. Which of the following chemicals is added to cement? lead oxide gypsum boric oxide kaolin b. Which of the given glasses dissolves in water? water glass hard glass pyrex glass ordinary glass c. Which of the following is a thermoplastic? melamine PVC bakelite urea d. Which of the following is a detergent? sodium pyrophosphate sodium palmitate sodium oleate sodium stearate 2. Answer the following questions. a. Define cement and write down the raw materials used for making cement. b. How is cement manufactured? Describe. c. What is glass? How is ordinary glass prepared? d. What is water glass? Name the raw materials for making water glass. e. What is pyrex glass? How is it prepared? f. How is lead crystal glass prepared? Explain. g. Name the metal oxides that are used for obtaining blue and green glass. h. What is ceramics? Why are ceramic materials brought into use? i. What are plastics? Write their types with examples. j. What is polymerization? 260 GREEN Science (Chemistry) Book-10
k. Write any three characteristics and three uses of plastics. l. What is soap? How is soap prepared? m. Define detergents with any three examples. n. What is compost fertilizer? How is it prepared? o. Write down the role of compost fertilizers. p. What are chemical fertilizers? Write their types with examples. q. What is chemical pollution? Write down the major causes of chemical pollution. r. Write any three ways to get rid of chemical pollution. s. Write in brief about 'solid waste management'. 3. Differentiate between: a. Mortar and concrete b. Hard glass and soft glass c. PVC and bakelite d. Soap and detergent e. Organic fertilizer and chemical fertilizer f. Thermoplastic and thermosetting plastic 4. Give reason: a. Gypsum is added to the cement. b. Boric oxide is added to the material for making glass. c. PVC is called a thermoplastics but bakelite is called a thermosetting plastic. d. Environmentalists request to avoid the use of plastics. e. Detergent is called soapless soap. f. Plastics are the major causes of environment pollution. Grid-based Exercise 2 Group ‘A’ (Knowledge Type Questions) (1 Mark Each) 1. What is cement ? 2. What are the materials necessary for the manufacture of cement ? 3. Name the chemical which increases the setting time of cement. 4. Write down raw materials used in the preparation of ordinary glass. 5. Mention any two properties of quartz glass. 6. Which metallic oxide is mixed in ordinary glass to make red and black glass of each ? 7. Which substance is used to increase refractive index of glass ? 8. Which glass is prepared by heating the mixture of silica and potassium carbonate? 9. Define lead crystal glass. 10. Write the name of metal oxides which are used for obtaining green and yellow coloured glasses. GREEN Science (Chemistry) Book-10 261
11. What is thermoplastic? 12. Define thermosetting plastic with one example. 13. What is detergent ? 14. What is compost manure ? 15. Define non-biodegradable wastes. Group ’B’ (Understanding Type Questions) (2 Marks Each) 16. Write any two differences between Mortar and Concrete. 17. Write any two differences between thermoplastic and thermosetting plastic. 18. NPK fertilizer is called a complete fertilizer, why? 19. PVC is not used to cover the handle of a pressure cooker, why? 20. Write any two differences between biodegradable solid wastes and non-biodegradable solid wastes. 21. Give two differences between soft glass and hard glass. 22. Distinguish between soap and detergent on two points. 23. Detergent is more useful than soap, why? 24. Mention any two properties of ceramics due to which it is suitable for making false teeth. 25. Plastic materials are widely used in comparison to other materials, why? Group ’C’ (Application Type Questions) (3 Marks Each) 26. Write any three uses of cement. 27. Write any three uses of plastics. 28. Write down the method of making soap with chemical equation. 29. Write any three ways to get rid of chemical pollution. 30. Write down one use of each of the given industrial chemicals. i. Sodium stearate ii. Potassium nitrate iii. Bakelite Group ‘D’ (Higher Abilities Type Questions) (4 Marks Each) 31. Describe the method of making cement in brief. 32. How is pollution caused by insecticides and chemical fertilizers ? Write. 33. Write the various steps of solid waste management. 34. Describe the method of making ordinary glass. 35. Describe the process of making utensils from ceramics in brief. 262 GREEN Science (Chemistry) Book-10
Biology UNIT Invertebrates 14 Weighting Distribution Theory : 5 Practical: 2 Before You Begin Invertebrates are those animals which do not have backbone or vertebral column.A variety of invertebrates like earthworm, mosquito, snail, butterfly, cockroach, moth, leech, etc. are found around us. Different types of insects like butterfly, mosquito, cockroach, silk moth, honeybee, wasp, etc. are found in our surrounding. Most insects are harmful and some insects are useful for human beings. But honeybee and silkworm are very useful for human beings. We get honey from honeybee and silk fibre from silkworm. Honey is highly nutritious food and silk fibre is used to make silk clothes. In this unit, we will study the life cycle of two useful insects. They are honeybee and silkworm. Learning Objectives Syllabus After completing the study of this unit, students will be able to: • Honeybee i. describe the structure and life cycle of honeybee and - Life cycle of honeybee - Economic importance of silkworm. honeybee ii. explain the importance of honeybee and silkworm. • Silkworm - Structure of silkworm - Life cycle of silkworn - Economic importance of silkworm Glossary: A dictionary of scientific/technical terms silkworm : an insect larva that produces silk from salivary glands mating : sexual intercourse between a male and a female pupa : the third stage of the life cycle of an insect drone : male honeybee nuptial : of or relating to marriage swarming : the behaviour of honey bee to come out in a large number sericulture : the rearing of silkworms for commercial production of silk fibre GREEN Science (Biology) Book-10 263
A. Honeybee Honeybees are the most familiar members of the phylum Arthropoda and class insecta. The honeybee usually described in textbooks is Apis mellifera, the common European honeybee. The small sized honeybee, employed for commercial bee-keeping (apiculture) in Nepal are Apis cerana, Apis dorsata, the giant honeybee and Apis florae, the little honeybee. Fig.14.1 Do You Know Fig. Classification of Honeybee Honeybees are social insects which live in a large colony. Kingdom : Animalia Phylum : Arthropoda Honeybees secrete liquid wax which Class : Insecta solidifies on coming in contact with air. Type : Honeybee Honeybees use wax to form combs for collecting honey and to raise adult from egg. Honey producing bees belong to Bombydae, Meliponidae and Apidae. Different species of Apidae are main honey producing bees. They are Apis mellifera, Apis floral, Apis dorsata, Apis indica and Apis adamsoni. Habit and Habitat Honeybees are found all over the world and are known for their art of manufacturing the honey and bee-wax. They are highly specialized insects, both in structure and habits. They constitute the social insects living in colonies and exhibiting polymorphism and division of labour. The nests or beehives of honeybees, harbouring thousands of individuals, are seen hanging down the tree branches or ceiling of houses. These are built by 14.2 their cooperative efforts and manifest a spectacular engineering feat (skill). Honeybees exhibit a high level of discipline while living in colony. Bee Colony Do You Know A colony of honeybees consists of three kinds Honeybees are trimorphic as they are of individuals or castes: (i) workers which are found in different forms in colony, viz. sterile females, (ii) drones which are fertile queen, drone and workers. males, and (iii) a queen which is a fertile female. The workers are assigned the job of The queen is the largest and the worker producing royal jelly, building the beehives, is the smallest in a bee colony. caring the larvae and disposing of the debris and dead bees. The drones and queen are for reproductive purposes. An average-sized colony consists of one queen, about 100 drones and 60,000 workers. 264 GREEN Science (Biology) Book-10
External Morphology Antenna Head Compound eye Simple eyes Wing Thorax Leg Abdomen Fig. Pollen collection area Fig. 14.3 Sting External morphology of honeybee Worker bee The worker bee is the smallest member of the colony and makes up the largest number of the colony individuals. It is black or brownish in colour with the body densely covered with hairs. For 10 days, it acts as a foster mother, feeding younger brothers and sisters. For more 10 days it cleans the hive and builds combs. As the fourth week approaches, it leaves the hive to forage for pollen and nectar till old age. Worker bees can visit 20-30 flowers in a minute to collect nectar and honey. Like all other insects, the body of the worker bee is divisible into three regions. They are head, thorax and abdomen. 1. Head It is a wide triangular structure with the apex pointed below. It bears a pair of large compound eyes, a pair of short and 12-jointed antennae and chewing and lapping type of mouthparts adapted for taking nectar from flowers and moulding the wax. 2. Thorax The thorax is divided into three segments- an anterior prothorax, a middle mesothorax and a posterior metathorax. Each of these segments bears a pair of legs and a pair of wings is borne by the mesothorax as well as metathorax. Honeybees consists of three pairs of legs densely 14.4 covered with hairs. The hairy legs contain pollen baskets. The thorax consists of two pairs of wings. Worker honeybee The wings are small, narrow, membranous and transparent. GREEN Science (Biology) Book-10 265
The abdomen consists of six visible segment and bears the wax glands and the sting at the end of abdomen. The sting is the modified ovipositor of the insects and is used for injecting poison. The glandular area secreting wax lies on the ventral surface of the last four visible segments of the abdomen. The wax is secreted through minute pores in the form of flat scales. The wax is masticated by the mandibles before its use for building the cells of the honeycomb. Duties of worker bees 1. Making honey combs. 2. Collecting pollen and nectar to make honey. 3. Protecting the hive from enemies. 4. Looking after eggs, larvae and pupae. 5. Feeding the larvae and the queen. Queen The queen is the only fertile female in a beehive, having immensely developed ovaries. She is elongated, 15-20 mm long and is easily distinguished by her long tapering abdomen, short legs and wings. She has pointed mandibles and shorter mouthparts Fig. Fig. and sting. She can sting repeatedly as there are no barbs on her sting. She is unable to produce wax and honey or gather pollen or nectar. She is a 14.5 specialized and degenerate individual with a small brain and without salivary glands. The queen arises from a fertilized egg and larva especially fed on royal jelly. She alone lays eggs and is the mother of almost all the members of the hive. She lives for several successive years laying about 2,000 or more eggs a day and up to about 1,500,000 eggs during her lifetime. Duties of a Queen Do You Know 1. To lay eggs. The queen produces a typical fragrance from its body which is known by all the 2. To co-ordinate the worker and drone bees of the colony. Due to this fragrance all bees according to their necessity. bees find their way to come back the hive during the collection of pollen grains and Drones nectar. Drones are the male honeybees. They fly near the hive in the sunshine. There are usually 100 drones in a typical colony, depending upon the season of the year. Drones are blackish and more hairy. They are intermediate in size, 15-17 mm long, but considerably stouter and boarder. They possess 14.6 very large eyes, small pointed mandibles and lack wax-producing glands, pollen-collecting apparatus and a sting. The drones do not work and 266 GREEN Science (Biology) Book-10
may be seen begging for honey from the workers. If not fed by the workers, they will die. They are fed by worker bees. They develop parthenogenetically from the unfertilized eggs laid by the queen and exist only to mate with the queen of their own or some other colony. Duties of Drones 1. To fertilize the queen bee 2. To keep he hive warm Parthenogenesis In honeybee colonies, the fertilized eggs develop into females (queen and workers) and the unfertilized eggs develop into male drones. This process is called haploid parthenogenesis: the unfertilized egg has only half the number of chromosomes of a fertilized egg. In parthenogenesis, reproduction occurs asexually when a female egg cell develops into a new individual without fertilization. The formation of drones, worker bees and queen is shown below: Male bee Mitosis Sperm cells Fertilizationfem2naleHojRenloleyyyal Worker bee (Drone) (n) (n) sterile female Queen bee Meiosis Egg cell (2n) (2n) Meiosis (n) Queen bee (2n) Egg cell No fertilization Male bee (n) (Parthenogenesis) (Drone) (n) Behaviour of Honeycomb The honeycomb or nest is commonly built hanging down vertically from a rock, building or branch of a tree. It consists of two layers of hexagonal chambers of cells made by the bee- wax secreted from the abdomen of the worker bee. Their walls are extremely thin and fragile. The storage cells containing honey and pollen, are usually built near the top and margins of the comb. The brood cells, generally occupying Fig. the lower and central positions, contain the young stages. In A. dorsata, the brood cells are 14.7 similar in shape and size but in other species Artificial beehive they may be of three types. The worker cells, in which workers are reared, are very small like the honey cells; the drone cells are slightly GREEN Science (Biology) Book-10 267
larger, while the queen cells are enormous, irregular, cylindrical or vase-shaped structures hanging down from the bottom. Like others, the queen cells cannot be used again. Life History The life cycle of honeybee shows complete metamorphosis. There are four stages in the life cycle of honeybee. They are: i. egg ii. larva iii. pupa and iv. adult. 1. Swarming The behaviour of the honeybee to come out of the hive in large numbers is called swarming. It takes place during the spring or early summer. It relieves the over-crowding and provides a means of colony-reproduction, i.e., founding of new colonies. On a fine forenoon, the old queen leaves the hive to establish a new one, accompanied by a large number of old workers and drones. Left behind in the hive are the young workers and several new queens still in their cells but approaching the time of emergence. Only one queen survives by stinging to death the other newly-hatched queens. 2. Nuptial or marriage flight The prime swarm is led by the old queen while the second swarm is accompanied by the newly- emerged virgin queen. About a week after emergence, the new queen takes her first aerial flight followed by a swarm of drones. The queen flies very high and the drones gradually drop out of the race. The last drone left in the race, mates with her. Mating occurs in mid-air, during which the queen receives spermatophores from the drone. The sperms are stored in spermathecal or sperm-reservoir of the queen to fertilize her eggs as long as she lives. The genital parts of the male are forced out with such a great pressure that he dies after mating. The pair then falls to the ground and the queen after pulling herself away returns to the hive not to leave it again, until she grows old and leads a prime swarm. 3. Development and caste determination Eggs An adult queen of 3-5 days comes out of hive and mates with drones in air. Two to three days after mating, the young queen begins to lay eggs. The queen lays about 1500-3000 eggs per day. However, the number of eggs may vary according to the species of honeybee. The eggs are white and elongated. In the first day of laying, the egg is erect, in the second day, it is slanted and in third day, it is horizontal in the cell. The queen lays eggs in drone cells to make males, queen cells to make queens and in worker cells to make worker honeybees. The stage of egg lasts for three days. A fertilized egg is laid in a worker or queen cell while an unfertilized egg in a drone cell. All eggs laid by the queen bee are not fertilized. The unfertilized egg contains 16 chromosomes whereas a fertilized egg contains 32 chromosomes. 268 GREEN Science (Biology) Book-10
Worker Queen Larva fed bee bread Larva fed royal jelly Fertilized eggs Fig. Unfertilzed Egg Larva Pupa eggs Drone 14.8 Life cycle of honeybee ii. Larva It is the second stage of the life cycle. After Do You Know three days small larvae or grubs hatch out from the eggs. The formation of a queen or The duration of larval stage in queen cells workers depends on the diet which the larvae is 5.5 days, that in drone and worker cell receive. All larvae are fed by the workers for is 6 days each. Larval stage is a voracious the first three days on the royal jelly, which is eater. The larva of a drone and queen cell composed of digested honey and pollen mixed is larger than that in worker cell. with a glandular secretion. The larvae destined (predetermined) to become queens receive this food throughout their life while, after the third day, the worker and drone larvae are fed upon increasing proportions of honey. If a worker larva is transferred to a queen cell before third day, it develops into a queen, and vice versa. The fully grown larvae are sealed with wax in the cells by worker bees. The larva sheds its skin for 5 times before changing into pupa. iii. Pupa Pupa is the third stage of the life cycle of honeybee. it is non-motile stage. A pupal stage is passed within the sealed chamber during which the larva secretes a thin, silken cocoon around it. It takes the queen on an average 7.5 days, the worker 12 days and the drone 14.5 days to complete metamorphosis and emerge out as adults. GREEN Science (Biology) Book-10 269
iv. Adult It is the last stage of the life cycle of honeybee. Do You Know All the organs develop and the pupa The worker bees survive for 6-7 weeks, changes into an adult after completing the drones for a few weeks to 4 months and metamorphosis. After laying eggs, a queen the queen for 2-5 years. bee develops within 15-16 days, a worker bee develops within 20-21 days and a drone bee develops within 22-24 days. The body structure and functions of queen, workers and drones are different. The duration of egg larva, pupa and adult of all three forms of bees is shown in the following table. Form of bee Egg Larva Pupa Adult Total Worker bee 3 days 6 days 14.5 days 6-7 weeks Upto 7 weeks Drone bee 3 days 6 days 12 days Upto 4months Up to 4 months Queen bee 3 days 5.5 days 7.5 days 2-5 years 2-5 years The queen bee lays eggs and releases special type of smell to conduct control the bee hive. Worker bees have a variety of roles according to their age. They are very busy in their own work. The division of labour according to the age of the worker bee is given below: 1. The worker bees of 1-3 days are very weak. They are also called baby bees. They move on bee hive, keep eggs and larvae warm and eat the food spread around them. Similarly, they clean the cells around them. 2. The worker bees of 4-6 days provide food to matured larvae. They also take a lot of food. 3. The worker bees of 7-11 days develop special gland in their head to secrete royal jelly. Worker bees feed this royal jelly to the queen and young larvae of 1-3 days. They also take a lot of food. 4. The gland that secretes royal jelly get dried in the workers of 12-17 days. They develop 4 pairs of wax glands in their abdomen which secrete wax. The wax is used to construct the beehive and to close the larvae cells and honey cells. The workers of 12-17 days are also called \"constructors\". 5. The worker bees of 18-20 days develop sting and poison glands. They protect their hive sitting at the entry point. 6. After 21 days, the worker bees come out of hive and they fly away to collect nectar, pollen, sap, water, etc. from crop fields and forests. At the approach of winter, the drones are driven out of the hive by the workers. They are either stung by workers or die of cold or hunger. The queen and the workers bridge over the winter season by feeding upon the stored honey and pollen. 270 GREEN Science (Biology) Book-10
Uses of Honeybee 1. Honey bees produce honey which is used as a nutritious food. Honey is also used to prepare jam, honey cakes, biscuits and breads. 2. Bee wax is used for making face packs, creams, lotions, candle, etc. 3. Honey is used as a medicine to cure weakness, fatigue, nervous disorder and mental disorder. 4. Honey is also used to cure hyperacidity, gastric ulcer and to kill bacteria. 5. Honeybees increase crop productivity by helping in pollination. Activity Visit a nearby beekeeping farm with your science teacher. Collect queen, drone and worker bee. Study their morphology. Prepare a short report and submit to your science teacher. Apiculture The primitive method of collecting honey is by killing the resting bees by flames and procuring their combs. The combs are then cut and squeezed to extract honey. This method is not only crude but also the honey thus extracted is not pure. This crude method of honey-collection persists in many parts even today but it is being gradually replaced by a better and scientific method called apiculture. The honeybees are now reared in artificial hives with large brood chambers and bee wax sheets called comb foundations. The bees are attracted to form cells and combs on the comb foundations which are then removed for extractions of honey. B. Silkworm Silkworm is a very important and useful insect to human beings in the context of our country. Silkworm forms a quality fibre called silk fibre which is extracted from (cocoons) one stage of its life cycle. Silk clothes are very popular, attractive, and stronger even they are expensive too. There are various kinds of silkworms found in our country Nepal. But from the economic point of view mainly two kinds of silkworms are reared in our country for the production of silk thread. They are ERI silk moth (Attacus ricini) and SERI silk moth (Bombyx mori). Bombyx mori silk moth is found on mulberry leaves produces the silk of commercial importance. It is the caterpillar of a moth whose cocoon is used to make silk. Attacus ricini silk moth is found on caster leaves. Fig. 14.9 Silkworm Silk fibre Silk cloth Silk moth GREEN Science (Biology) Book-10 271
Classification of silk moth Do You Know Kingdom : Animalia It has been found that about 95% of the silk produced in the world includes seri Phylum : Arthropoda silk or mulbery silk. Class : Insecta Type : Silkworm/Silk moth External Morphology of Silk moth Silk moth is a small insect of creamy white colour. It is slightly thick and shiny in nature. Do You Know It is about 2 to 3 cm in length. The body of silkworm is mainly divided into three parts, The proboscis of silkmoth is highly viz. head, thorax and abdomen. The head reduced. So the adult moth does not take consists of a pair of feathery antennae, a pair of food during adult stage. compound eyes and the sucking type of mouth parts. The thorax consists of three pairs of legs and two pairs of wings covered with scales which are about 25 mm in length. The abdomen consists of ten hairy segments. The entire body of silkworm is covered with minute scales. Male and female moths are flightless and lack functional mouth parts. The moths differ in morphological features. The female has a large abdomen whereas the male has a much larger pair of antennae with comb-like side projections on one of two margins of the segments. Fig. 14.10 Silk moth (female) Silk moth (male) Life cycle of Silk moth The life cycle of silk moth demonstrates the most advanced form of metamorphosis. Silk moths are unisexual, i.e. sexes are separate. Silk moth passes all the stages of an insect in its life cycle. Silk moth lives on mulberry trees. The adult moths seldom eat and are primarily concerned with reproduction. The male dies after copulation and the female is oviparous and dies after laying eggs. The serial progressions of four distinct stages of development complete one generation of the species. The four stages in the life cycle of a Silk moth are as follows: 1. Egg 2. Larva 3. Pupa 4. Adult 272 GREEN Science (Biology) Book-10
Adult female Adult male Cocoon chrysalis Eggs Dorsal horn cCuot coopoenn Eggs on mulberry leaf Head Fig. Fig. Thoracic true legs Spiracles Abdominal pseudolegs 14.11 1. Egg The female Silk moth lays about 300 to 400 whitish seed-like eggs about the size of an ink dot during summer or the early fall at a time. It lays eggs on the leaves of mulberry tree. The eggs are covered with a gelatinous secretion by which they stick to the leaves. The eggs in the beginning are whitish, small and later they change into grey as the development proceeded. Female moth lays the eggs and dies after 14.12 3 to 4 days of laying eggs. In a cool place, Eggs of Silk moth on mulbery leaf the eggs can be stored for long time when mulberry leaves are not available. In favourable condition, they hatch into larvae. Larvae are produced in about two weeks from eggs in a temperature of 18°C to 25°C. 2. Larva Larva is the vegetative stage where the growth takes place. Larvae live on eating mulberry leaves about 25 to 32 days. They are similar to larvae of butterfly (caterpillar). A silk moth passes through five stages during the larvae phase of its life. These five stages are called instars. The larvae that comes out from the egg is Fig. called first instar which is grey in colour and body consists of twelve segments. The 14.13 first instar feeds on the mulberry leaves Larvae of Silk moth on mulberry leaves and grows very quickly. After 4-5 days, it GREEN Science (Biology) Book-10 273
stops feeding and becomes inactive. The moulting occurs four times in the larva stage. After each moulting they do not eat food and move for about 20 to 24 hours. The second, third and fourth instar eats food for three days and then sleeps for about 24 to 26 hours, 26 to 30 hours and 20 to 36 hours respectively, whereas fifth instar eats food for three days and sleeps for 36 to 42 hours. The required quantity of water is fulfilled from leaves they eat. Larva possesses silk glands, which produces silk fibres as thin thread from its saliva. It begins to wrap the thread in its body. This becomes an egg like structure called cocoon. Further development of silkworm takes place inside the cocoon. 3. Pupa A larva develops the thread from its saliva, it wraps itself and forms a spherical structure called cocoon. This stage is called pupa which is the third stage of life cycle. Pupa goes on developing inside cocoon. Pupa stage completes in about 12 to 14 days. The pupa stage is inactive stage which goes on developing inside cocoon. During pupation, unsegmented abdominal prolegs become absent and thorax forms two pairs of wing. As a result of complete metamorphosis, pupa changes into an imago, which produces an alkaline fluid to moisten one end of cocoon and emerges out. For the extraction of silk, the cocoons are kept in boiling or hot water. The pupa dies within the cocoon. Living pupa feeds on the silk if it survives. About 1000 to 15000 meter long silk thread can be extracted from one cocoon. Fig. Fig. 14.14 Cocoons Pupa of silk moth 4. Adult After certain period of development, newly 14.15 formed adult silk moth (imago) breaks the cocoon to come out from it. It possesses three pairs of legs and two pairs of wings. It cannot fly immediately, thus after drying its wings for some time in air, the adult flies in the sky. Thus, under favourable condition the life cycle of silkworm completes in about 45 days. Silk moth emerging out of cocoon 274 GREEN Science (Biology) Book-10
Sericulture Do You Know Historically, sericulture was introduced for the Mulberry leaves are not available first time in China, around 2700 BC. Sericulture throughout the year. Therefore, eggs is the rearing of silkworms for the production of Silk moths are stored below 18°C in of silk on commercial basis. Sericulture helps winter to prevent them from hatching. to improve the economic development of individual and the nation. Sericulture helps The natural silk fibre is called queen of to improve the economic condition of farmers fibres because it is soft, shiny, elastic, since silk clothes are very expensive. strong and durable. Silk farming requires i. Clean and dry mulberry leaves. ii. Temperature maintenance for hatching of eggs (between 18°C to 25°C). iii. Proper silk threads extraction method Advantages from silkworm 1. Silkworms are very useful insects. About 1000 to 1500 meter long thread can be extracted from a single cocoon. 2. Silk extracted from silkworm is natural silk which is many times shiny, light, soft and durable as compared to artificial silk. 3. Intestines of silkworms are useful in various surgical finishing purposes. Features of natural silk fibre produced from cocoon 1. Silk fibre is very long, attractive, strong and shiny. 2. Clothes made from silk are valuable and that can be used in all seasons. 3. It has high elasticity so it can be stretched easily. 4. It is used in making very fine and expensive clothes. 5. It absorbs water rapidly and can be dried easily. 6. It can be coloured easily. 7. It has high resistant to deformation. 8. The fibre is more comfortable to wear. Uses of Silk fibre 1. Silk fibre is used to make clothes and insulation coil of telephone. 2. The dead pupae obtained during extraction of silk fibre are used to feed livestock and fishes. GREEN Science (Biology) Book-10 275
Key Concepts 1. Honeybees are the most familiar members of the phylum Arthropoda and class insecta. 2. They are found all over the world and are known for their art of manufacturing the honey and bee-wax. 3. A colony of honeybees consists of three kinds of individuals or castes: (i) workers which are sterile females, (ii) drones which are fertile males, and (iii) a queen which is a fertile female. 4. The worker bee is the smallest member of the colony and makes up the largest number of the colony individuals. It is black or brownish in colour with the body densely covered with hairs. 5. The queen is the only fertile female in a beehive, having immensely developed ovaries. 6. The queen arises from a fertilized egg and larva especially fed on royal jelly. She alone lays eggs and is the mother of almost all the members of the hive. 7. Drones are the male honeybees. They fly near the hive in the sunshine. There are usually 100 drones in a typical colony, depending upon the season of the year. 8. The behaviour of the honeybee to come out of the hive in large numbers is called swarming. It takes place during the spring or early summer. 9. After laying eggs, a queen bee develops within 15-16 days, a worker bee develops within 20-21 days and a drone bee develops within 22-24 days. 10. Silkworm is a very important and useful insect to human beings in the context of our country. 11. Silk clothes are very popular, attractive, and stronger even they are expensive too. 12. The female Silk moth lays about 300 to 400 whitish seed-like eggs about the size of an ink dot during summer or the early fall at a time. 13. In favourable condition, they hatch into larvae. Larvae are produced in about two weeks from eggs in a temperature of 18°C to 25°C. 14. Sericulture is the rearing of silkworms for the production of silk on commercial basis. Sericulture helps to improve the economic development of individual and the nation. 15. Silkworms are very useful insects. About 1000 to 1500 metre long thread can be extracted from a single cocoon. 276 GREEN Science (Biology) Book-10
Sequential General Exercise 1 1. Choose the best answer from the given alternatives. a. Which of the following is a fertile female? queen drone worker larva 21 days b. What is the duration of the egg of honeybee? 25 days adult 6 days 3 days 12 days c. The life cycle of Silk moth completes in ........................... 7 days 45 days 21 days d. In which stage does a Silk moth produce silk? egg larva pupa e. How many chromosomes are found in fertilized egg of honeybee? 8 16 32 46 2. Answer the following questions. a. Where are honeybees found? b. Where are the nests of honeybees seen? c. Describe the structure of workers, drones and a queen bee. d. Draw a neat figure of a worker bee. e. Name the type of mouthparts of a honeybee? f. What is swarming? g. Describe in brief the structure of honeybee. h. Explain in brief the life history of honeybees. i. What is the economic importance of honeybees? j. What is apiculture? Write down its significance in the context of Nepal. k. Why is the silkworm called a useful insect? l. Where do silkworms live? m. What is a cocoon? How we can extract silk from cocoon? n. Describe the life cycle of silkworm with a well-labelled diagram. o. What are the characteristics of silk thread? p. Write shorts note on sericulture. 3. Why are the eggs of Silk moth kept in cold places for a long time? 4. In which stage does the silkworm produce silk fibre in its life cycle? GREEN Science (Biology) Book-10 277
5. Name two types of silkworms found in Nepal. 6. In which instar larvae begin to produce silk thread? 7. Write a procedure to extract silk from cocoon. 8. In how many times does silkworm change its skin? 9. In how many days the silkworms completes their life cycle? 10. Differentiate between: a. Eggs of Silk moth and Larvae of Silk moth b. Pupa and Cocoon c. Worker bee and Drone bee d. Worker bee and Queen bee 11. Sericulture is very important context of our country. Explain this statement. Project work Visit a nearby sericulure and apiculture farms with your science teacher. Observe various stages of the life cycle of silkmoth and honeybee. Prepare a short report and submit to your science teacher. Grid-based Exercise 2 Group ‘A’ (Knowledge Type Questions) (1 Mark Each) 1. Write the name of two species of silkmoths reared in Nepal. 2. Write down the scientific name of Seri silkworm and Eri silkworm. 3. What is the food of the larva of Seri silkmoth? 4. What is the food of Eri silkworm? 5. What is the food of larva of silkmoth? 6. Write any two characteristics of eggs of silkmoth. 7. what is the duration of the larva of silkmoth? 8. In which stage of life cycle does the silkmoth produce silk thread? 9. In how many days does life cycle of silkmoth complete? 10. How many types of honeybees are there in the hive? What are they? 11. Write any two characteristics of drone bee. 12. Mention the major function of queen bee. 278 GREEN Science (Biology) Book-10
13. What is metamorphosis? 14. In how many stages does the life cycle of silkmoth complete? What are they? 15. What is royal jelly? Group ‘B’ (Understanding Type Questions) (2 Marks Each) 16. Why is silkmoth called the queen of insects? 17. Why are eggs of silkmoth stored below 18°C in winter season? 18. Why is the larva of silkmoth called voracious eater? 19. Write any two differences between larva and egg of silkmoth. 20. Why are cocoons kept in hot air before the extraction of silk fibre? 21. Write any two differences between male silkmoth and female silkmoth. 22. Write any two differences between pupa and cocoon. 23. Why is honeybee called social insect? 24. Write any two differences between queen bee and drone bee. 25. Write any two differences between worker bee and queen bee. Group ’C (Application Type Questions) (3 Marks Each) 26. How does silkworm produce silk fibre? Describe in brief. 27. Describe in brief the advantages of silkmoth. 28. How is sericulture done? Explain in brief. 29. Write any three functions of worker bee. 30. Write any three uses of honeybee for human beings. Group ’D’ (Higher Abilities Type Questions) (4 Marks Each) 31. Draw a neat and labelled figure showing the life cycle of silkmoth. 32. Describe the life cycle of silkmoth in brief. 33. Describe the method of extraction of silk fibre from silkworm. 34. Draw a neat and labelled figure showing the life cycle of honeybee. 35. How is honey prepared from honeybee? Describe in brief. GREEN Science (Biology) Book-10 279
UNIT Human Nervous and 15 Glandular System Weighting Distribution Theory : 5 Practical: 2 Before You Begin A variety of changes occur in our surroundings. These may be physical as well as chemical changes. We know about these changes with the help of five sense organs, nerves and brain. When we touch an ice cube, we feel cold. When we touch a burning coal, we feel hot. Similarly, we feel pain when pricked with a pin. We remove our hand immediately when we touch a hot object. All these activities are controlled by nervous system. Similarly, endocrine system also plays a great role to conduct various activities of our body in a balanced condition. Endocrine system consists of different types of endocrine glands which secrete different types of hormones. In this unit, we will study about human nervous system and glandular system, structure and functions of brain, endocrine glands and their functions with disorders. Learning Objectives Syllabus After completing the study of this unit, students will be able to: • Human nervous system • Central nervous system i. give general introduction to human nervous system – Brain and describe the functions. – Spinal cord • Neuron and its types ii. give general introduction to human glandular system • Peripheral nervous system and describe its functions. • Autonomic nervous system • Glandular system iii. introduce hormones and state their functions with • Endocrine glands disorders due to hyposecretion and hypersecretion of these hormones. Glossary: A dictionary of scientific/technical terms nervous : of, relating to or composed of neurons glandular : of, relating to or composed of glands neuron : smallest unit of nervous system or a nerve cell cranium : the outer bony cover that protects the brain meninges : the three layered membrane that surrounds the brain hormones : the chemical messengers that control, co-ordinate and integrate various activities of the body 280 GREEN Science (Biology) Book-10
A. Human Nervous System We react various stimuli with help of a system made of the brain, spinal cord and different types of nerves. The system formed by the brain, spinal cord and different types of nerves is called nervous system. Nervous system collects information from outside the body with the help of five sense organs. It also controls various activities of body with the help of nerves. It also transmits information to organs, muscles and glands. The nervous system in human body is divided into three parts which are as follows: a. Central nervous system (CNS) b. Peripheral nervous system (PNS) c. Autonomic nervous system (ANS) a. Central nervous system The system formed by the brain and spinal cord is called central nervous system. It is located in mid dorsal part of our body. Brain 15.1 Fig. Cerebrum Fig. Corpus callosum Brain is the most developed Diencephalon organ which controls various Midbrain activities of human body. It is the largest and the uppermost Cerebellum portion of nervous system. It is Pons varoli protected inside the box of Medulla oblongata bones called cranium. The Spinal cord weight of the brain in adult human beings ranges from Structure of human brain 1200 to 1400 gram. The brain consists of 10000 million nerve cells. The brain works as the highest co-ordinating centre in the human body. The brain is surrounded by a three Cerebrum layered protective membranes called meninges. These three Cerebellum layers are duramater, piamater and Medulla oblongata arachnoid. Duramater remains 15.2 Spinal cord attached to the inner surface of the skull. Similarly, arachnoid is Structure of human brain attached to the surface of the brain. The space between arachnoid and piameter is filled with a fluid which is called cerebrospinal fluid. GREEN Science (Biology) Book-10 281
This fluid protects the brain from mechanical shocks. The brain is mainly divided into three parts. They are as follows: i. Cerebrum ii. Cerebellum iii. Medulla oblongata 1. Cerebrum Cerebrum occupies 80% of the brain. It is the largest part of the brain. Cerebrum is a dome-shaped part which is spread into four regions, viz. frontal, parietal, temporal and occipital. The cerebrum is divided into and left right Do You Know cerebral hemispheres. The dorsal surface of Injury to cerebrum leads a person into these hemispheres contain a deep median coma. groove (fissure). The fissure is called corpus callosum. There are many convolutions in hemispheres which increase the surface area of the brain. The outer part of the cerebral hemispheres is made of gray matter and the inner part is made of white matter. A person enters into coma when the cerebrum gets mechanical shock. Functions of cerebrum i. Cerebrum controls various mental activities like memorizing, thinking, learning, reasoning, intelligence, etc. ii. It controls the functions of different organs of the body. iii. It controls anger, emotions, will, speech, etc. iv. It controls feeling of love, hatred, admiration, etc. 2. Cerebellum It is the second largest part of the brain. It consists of two small hemispheres like lemon. It also consists of gray matter outside and white matter inside. Cerebellum is located above medulla oblongata and below the posterior part of cerebrum. It occupies about 10% of the total weight of the brain. Do You Know Functions Small injury to cerebellum causes i. Cerebellum maintains body balance. dizziness which disturbs body balance. ii. It controls muscular tone. iii. It controls voluntary movement. Alcohol affects the cerebellum which affects body balance. Injury to cerebellum leads to failure of voluntary muscles and causes paralysis. 282 GREEN Science (Biology) Book-10
3. Medulla oblongata It is the lowermost part of the brain. It is cylindrical in shape. It is connected to the spinal cord. It also consists of gray matter and white matter. Medulla oblongata contains various vital reflex centres like cardiac centre and centre for conghing, sneezing, hiccupping, swallowing, etc. Damage to medulla oblongata causes instant death. Functions i. It controls vomiting, coughing, swallowing, etc. ii. It controls heart beat, breathing and blood pressure. iii. It controls contraction and relaxation of blood vessels. iv. It controls peristalsis (contraction and relaxation of digestive tract), secretion of hormones and enzymes, secretion of saliva, etc. Spinal Cord Brainstem Spinal cord It is an elongated and cylindrical structure which Vertebra arises from medulla oblongata. It passes down in the neural cavity of vertebral column upto lumbar vertebrae. The outer surface of the spinal cord is made of white matter and inner surface is made of gray matter. The spinal cord is connected to the brain. It is protected by bony cage of vertebral column. Spinal cord is also protected by cerebrospinal fluid and spinal meninges. Any shock or injury to the spinal cord causes paralysis of the body below the portion of injury. Such a type of injury is called spinal injury. Functions Cauda equina i. It connects different part of body to the brain. Fig. ii. It controls reflex action. 15.3 Spinal cord inside the vertebral column Neuron Neuron is the smallest unit of nervous system. It is also called a nerve cell. A neuron consists of cell body having long and short branches. The cell body consists of nucleus, cytoplasm and different types of nerves. The short branches of a neuron are called dendrites whereas the long branch is called axon. Axon carries impulses away from the cell body whereas dendrites collect message towards the cell body. GREEN Science (Biology) Book-10 283
Cell nucleus Dendrites Myelin sheath Axon Neural impulse Cell body 15.4 Fig. Axon terminals Fig. Motor neuron (multipolar) Sensory (afferent) neuron A Spinal cord Motor (efferent) neuron B C 15.5 Sensory neuron (unipolar) Dendrite Dendrite Peripheral Cell body Cell body axon Central axon Axon Fig. 15.6 a. Bipolar b. Pseudo-unipolar c. Multipolar 284 GREEN Science (Biology) Book-10 Inter neuron (multipolar)
The axon of the neurons combine and form nerve fibres. On the basis of function, nerve fibres are of three types. They are as follows: i. Sensory or afferent neuron It carries impulses or messages from receptor to the spinal cord or brain. ii. Motor or efferent neuron It carries impulses or messages from spinal cord or brain to the different parts of body, Nervous tissues act as messengers between the spinal cord and brain. iii. Inter neuron It converts sensory impulses into motor impulses. Ganglia Ganglia are the groups of nerves made of gray matter. They are found near the spinal cord. They establish communication between the brain and spinal cord. White matter Dorsal root ganglion Ganglion Gray matter Dorsal root Sensory neuron soma Fig. Spinal nerve 15.7 Motor neuron soma Ventral root Ganglion near spinal cord Synapse The axon of a neuron branches into fine filaments which terminate into synaptic knobs or swellings. These synaptic knobs are very close to the dendrites and the cell body of next neuron. So, synapse is the minute gap between synaptic knob of a neuron and dendrites and cell body of next neuron. b. Peripheral nervous system The nervous system which consists of nerve tissue that communicates between the brain and different parts of body is called peripheral nervous system. This system is made of two types of nerve fibres which are as follow: i. Cranial nerve fibres ii. Spinal nerve fibres GREEN Science (Biology) Book-10 285
i. Cranial nerve fibres The nerve fibres that originate from the brain are called cranial nerve fibres. Twelve pairs of nerve fibres arise from the brain. These nerve fibres communicate between the brain and various organs present in the head, i.e. eyes, ears, nose, mouth, tongue, etc. Cranial nerve fibres originate from the brain and end in the head region. ii. Spinal nerve fibres The nerve fibres that originate from the spinal cord and form a network of nerves to different parts of the body are called spinal nerve fibres. Thirty one pairs of nerve fibres originate from the spinal cord. These nerve fibres form a network to various parts of the body. Spinal nerve fibres communicate between the brain, spinal cord and different parts of the body. c. Autonomic Nervous System Autonomic nervous system consists of sympathetic and parasympathetic nervous system. This nervous system controls the functions of muscles and certain glands when we are sleeping or waking up. Sympathetic nervous system increases the functions of heart, respiration, intestine, stomach, urinary bladder, etc. Similarly, parasympathetic nervous system brings the increased functions of these organs to the normal condition. The functions of sympathetic and parasympathetic nervous system are opposite to each other . For example, sympathetic nervous system increases the heart beat and blood pressure when an accident occurs suddenly. On the other hand, parasympathetic nervous system brings increased heart beat and blood pressure under normal conditions. In this way, autonomic nervous system controls various activities of the body. Project work Prepare a model of human nervous system in a chart paper. Colour it and display in your classroom. B. Glandular System The system which is formed by a group of glands is called glandular system. Glands are the group of epithelial cells which secrete hormones or enzymes. Watering of mouth occurs when we see a tasty food. Similarly, tears come out when an insect enters our eye. The secretion of saliva and tear is possible due to presence of glandular system in our body. Tears are produced by tear glands present in corners of eyes. Similarly, saliva is secreted by salivary gland present in the wall of buccal cavity. These are different types of glands present in different parts of human body. On the basis of structure and function, there are two types of glands in human body. They are as follows: a. Exocrine glands b. Endocrine glands 286 GREEN Science (Biology) Book-10
a. Exocrine glands The glands which have a duct or tube to pass their secretion are called exocrine glands. Salivary gland, gastric glands, intestinal glands, tear glands, sweat glands, etc. are the examples of exocrine glands. Exocrine glands secrete enzymes . Enzymes secreted by exocrine glands are poured to the corresponding parts through the duct. Enzymes generally help in the digestion of food and internal respiration. b. Endocrine glands The glands having no duct to pass their secretion are called endocrine glands. Pituitary gland, thyroid gland, pancreas, adrenal gland, etc. are the examples of endocrine glands. Endocrine glands pour their secretion directly into the blood stream. Endocrine glands are small in size. But they secrete very important chemicals called hormones. Hormones are required for normal growth and development of the body. They affect metabolism, reproduction and other characteristics. Various symptoms and disorders like obesity, infertility, gigantism, dwarfism, etc. occur in the body due to under secretion or over secretion of certain hormones. Therefore, endocrine glands are very important though they are small in size. The system formed by a group of endocrine glands is called endocrine system. This system uses chemicals to communicate. These chemicals are called hormones. Differences between Exocrine glands and Endocrine glands Exocrine glands Endocrine glands i. They have duct or tube to pour i. The do not have duct to pour their their secretion. secretion. ii. They secrete enzymes. ii. They secrete hormones. iii. They are present near the site of iii. They are present away from the site action. action. Hormones The word 'hormone' has been derived from the Greek word 'hormones' which means to set in motion. Hormones are the chemical substances produced by endocrine glands which control, co-ordinate and regulate metabolic activities, growth and development of body. Examples: growth hormone, thyroxine, insulin, testosterone, etc. Hormones are produced by endocrine glands and are released in blood stream. Hormones act as chemical messengers to control and regulate various metabolic activities, growth and development of the body. Chemically, hormones are proteins, amino acids or steroids. Hormones are specific in function and they act only in target cells, tissues and organs. Functions of hormones i. Hormones regulate growth and development of the body. ii. They regulate reproduction. GREEN Science (Biology) Book-10 287
iii. They control and stimulate various metabolic as well as physiological activities of the body. Endocrine glands present in human body The various endocrine glands present in human body are as follows: a. Pituitary gland b. Thyroid gland c. Parathyroid gland d. Adrenal gland e. Pancreas f. Testes g. Ovaries a. Pituitary gland (Master gland) Pituitary gland is located in the Do You Know skull just below the mid brain. It is a pea-sized gland attached to the Pituitary gland controls and stimulates various lower surface of the brain. activities of the human body. It also controls the secretion of other endocrine glands. Therefore, Pituitary gland secretes two types pituitary gland is also called master gland. of hormones. They are: i. Growth hormone or Somatotrophic hormone ii. Catalytic hormones or Stimulating hormones Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female)Fig. Testis (male) 15.8 Endrocrine System of Human Body 288 GREEN Science (Biology) Book-10
Functions of growth hormone i. Growth hormone control the growth and overall development of the body. ii. It increases the rate of protein synthesis. Functions of catalytic hormones i. Catalytic hormones control the secretion of other endocrine glands. ii. They control and regulate various metabolic activities. The hyposecretion or undersecretion of growth hormone during childhood causes dwarfism and hypersecretion or over secretion causes gigantism. The hypersecretion of growth hormone in adults causes over growth of jawbone and bowing of backbone. b. Thyroid gland This gland is located in the neck region just below the larynx in front of trachea. It has two lobes, viz. right lobe and left lobe. A narrow mass of tissue called isthmus connects those lobes together. Thyroid gland secretes two hormones. They are as follows: i. Thyroxine or thyrotrobin ii. Calcitonin Functions of thyroxine or thyrotrobin i. It regulates the growth and development of the body. ii. It controls the activities of nervous system. iii. It stimulates the rate of cellular respiration and metabolism. Functions of calcitonin i. It regulates the level of calcium and phosphate in blood. ii. It controls calcium absorption and release by bones. Thyroxine hormone contains iodine. The hyposecretion or lack of iodine in the body causes swelling of thyroid gland. This condition is called goitre. Following symptoms are seen in the body due to deficiency of thyroxine hormone: • Obesity • Simple goitre • Physical and mental weakness • Roughness a skin • Stammering • Hoarseness of sound • Less sweating GREEN Science (Biology) Book-10 289
Following symptoms are seen in body due to hypersecretion of thyroxine hormone: • Loss of weight • Excessive excitement • Digestive disorders • Increased metabolic rate • Mental imbalance • Protruding eyes • Excessive sweating • Excessive hunger c. Parathyroid gland Parathyroid glands are located behind the thyroid gland. These glands are oval in shape. One pair of parathyroid gland is located in the left lobe and one pair is located in the right lobe of the thyroid gland. Parathyroid glands secrete a hormone called parathormone hormone. It is also called parathyroid hormone. Functions of parathormone hormone i. It regulates the exchange of calcium between blood and bones. ii. It increases the level of calcium in blood. The hypersecretion of parathormone hormone has following symptoms in the body. • Kidney stone • Parathyroid tumour • Softening of bones Do You Know The hyposecretion of parathormone Wrinkles are seen on the face and hands when hormone causes painful jerk of parathyroid glands are removed from the body. It voluntary muscles, the amount occurs due to lack of calcium in blood. of calcium in blood decreases and muscles contract. This condition is called tetany. d. Adrenal glands Right adrenal gland Left adrenal gland One adrenal gland is located on the top of each kidney. Adrenal gland is a cream coloured gland. It produces a hormone called adrenalin. Adrenal glands are also known as emergency glands. Functions of adrenalin Fig. i. It prepares body to face various condition like stress and strain. 15.9 Kidney Kidney 290 GREEN Science (Biology) Book-10
Fig.ii. It controls fear, anger and blood pressure. iii. It controls emotions, heart beat and respiration. iv. It controls the contraction of voluntary muscles. The blood pressure increases due to oversecretion of adrenalin hormone. Following symptoms are seen in the body due to hyposecretion of adrenalin hormone. • Weakness • Nausea • Low blood pressure • Less sugar content in blood • Unconsciousness Adrenal gland is also called emergency gland because this gland releases emergency hormone to face the emergency situation and prepares the body for flight, fight or fright. Adrenal releases cortison hormone which also acts as a sex hormone. Feminine characters are seen in males due to over secretion of cortisone hormone. Similarly, masculine characteristics are seen in female due to oversecretion of cortisone hormone. e. Pancreas Pancreas is a leaf-shaped gland located posterior to the stomach in the abdominal region. This gland remains attached to the duodenum and measures 10-15 cm in length. Pancreas has an exocrine part to secrete enzymes and an endocrine part to secrete hormones. Therefore, pancreas is also called a mixed gland. Head Body Tail Pancreatic duct Bile duct Duodenum 15.10 The endocrine part of pancreas secretes two hormones. They are i. Insulin ii. Glucagon Functions of insulin i. It controls amount of sugar in blood. ii. It stimulates deposition of extra glucose in the forms of glycogen in liver and muscles. GREEN Science (Biology) Book-10 291
Function of glucagon i. It increases amount of sugar in blood. ii. It stimulates liver to convert glycogen into glucose. The under secretion of insulin causes diabetes. It is commonly known as sugar disease. The symptoms of diabetes are as follows: • Excessive hunger • Excessive thirst • Frequent urination • High concentration of sugar in blood and urine • Weakness • Delay in wound healing The oversecretion of insulin in the body causes insulin shock. f. Testes or Male gonads In males, two testes are located in a small muscular pouch outside the lower abdominal region. They are also called male gonads. Testes produce a male sex hormone called testosterone. Functions of testosterone i. Testosterone controls the development of secondary sexual characteristics in males like • enlargement of sex organs. • growth of facial and pubic hair. • deeper voice. • enlargement of larynx. g. Ovaries In females, two ovaries are located in the lower abdominal region. They are oval–shaped glands. Ovaries are also called female gonads. Ovaries secrete two female sex hormones. They are as follows: i. Oestrogen ii. Progesterone Functions of oestrogen the Do You Know sex i. Oestrogen controls The release of ovum or egg from ovaries is called development of female ovulation. organs. ii. It controls the development of female characteristics like 292 GREEN Science (Biology) Book-10
• Soft skin and breasts. • Hair pattern. • Feminine voice, etc. Functions of progesterone i. Progesterone helps in maintenance of pregnancy. ii. It controls ovulation. Activity Take a chart paper. Prepare a model of human endocrine system. Label various endocrine glands and write hormones secreted by them. Display the chart paper in your classroom. Key Concepts 1. The system formed by the brain, spinal cord different types of nerves is called nervous system. 2. Nervous system collects information from outside the body with the help of five sense organs. It also controls various activities of body with the help of nerves. 3. The system formed by the brain and spinal cord is called central nervous system. 4. Brain is the most developed organ which controls various activities of human body. 5. The space between arachnoid and piameter is filled with a fluid which is called cerebrospinal fluid. This fluid protects the brain from mechanical shocks. 6. Cerebrum is a dome-shaped part which is spread into four regions, viz. frontal, parietal, temporal and occipital. 7. A person enters into coma when the cerebrum gets mechanical shock. 8. Cerebrum controls various mental activities like memorizing, thinking, learning, reasoning, intelligence, etc. 9. Cerebellum is located above medulla oblongata and below the posterior part of cerebrum. It occupies about 10% of the total weight of the brain. 10. Medulla oblongata contains various vital reflex centres like cardiac centre and centre for conghing, sneezing, hiccupping, swallowing, etc. 11. Any shock or injury to the spinal cord causes paralysis of the body below the portion of injury. 12. The nervous system which consists of nerve tissue that communicate between the brain and different parts of body is called peripheral nervous system. 13. The nerve fibres that originate from the spinal cord and form a network of nerves to different parts of the body are called spinal nerve fibres. 14. The system which is formed by a group of glands is called glandular system. Glands are the group of epithelial cells which secrete hormones or enzymes. 15. Hormones are very important chemicals required for normal growth and development of the body. They affect metabolism, reproduction and other characteristics. GREEN Science (Biology) Book-10 293
16. The system formed by a group of endocrine glands is called endocrine system. This system uses chemicals to communicate. These chemicals are called hormones. 17. Hormones are the chemical substances produced by endocrine glands which control, co-ordinate and regulate metabolic activities, growth and development of body. 18. Adrenal gland is also called emergency gland because this gland releases emergency hormone to face the emergency situation and prepares the body for flight, fight or fright. 19. Pancreas has an exocrine part to secrete enzymes and an endocrine part to secrete hormones. Therefore pancreas is also called a mixed gland. Sequential General Exercise 1 1. Choose the best answer from the given alternatives. a. The number of cranial nerves is .................... 12 pairs 31 pairs 21 pairs 13 pairs 33 pairs b. The number of spinal nerves is ...................... 13 pairs 31 pairs 6 pairs c. Which of the following glands is called master gland? adrenal gland pituitary gland thyroid gland pancreas d. Which of the following glands secretes both hormones and enzymes? testes ovaries pancreas adrenal e. Which of the given hormones control the amount of sugar in blood? adrenalin testosterone oestrogen insulin 2. Answer the following questions. a. What is nervous system? Name its types. b. What are meninges ? Write their function. c. What is cerebrospinal fluid? Write its function. d. Write down the major functions of – cerebrum – cerebellum – medulla oblongata 294 GREEN Science (Biology) Book-10
e. Where is spinal cord located? Write its major functions. f. What is peripheral nervous system? Write its functions. g. Write down the major functions of autonomic nervous system. h. Draw a neat figure of a neuron and describe its structure. i. What are exocrine glands? Give any two examples. j. What are endocrine glands? Give examples. 3. Where are the given endocrine glands located in human body? Write the hormones secreted by each of them. a. pituitary gland b. pancreas c. ovaries d. adrenal gland e. testes 4. Write down the major function of the hormones given below: a. growth hormone b. insulin c. progesterone d. parathormone e. insulin 5. Draw a neat and labelled figure showing various parts of human brain and describe any two parts of the brain in brief. 6. Draw a neat and labelled figure showing various endocrine glands of human body. 7. Write down the symptoms in the body due to hyposecretion and hypersecretion of a. growth hormone b. insulin c. thyroxin hormone 8. Differentiate between: a. Cerebrum and cerebellum b. Sensory neuron and motor neuron Cranial nerves and spinal nerves c. Endocrine and exocrine glands d. e. Salivary gland and thyroid gland 9. Give reason: a. Hormones are called chemical messengers. b. Pituitary gland is called a master gland. GREEN Science (Biology) Book-10 295
c. Adrenal gland is called an emergency gland. d. Pancreas is called a mixed gland. e. Hormones are very important for growth and development of body. 10. Name the glands A, B, C, D, E and F shown in the given figure. Also, mention the names of hormones secreted by each of them. A B C D E F 11. List the major functions of human nervous system. 12. Describe the importance of endocrine system in human body. 296 GREEN Science (Biology) Book-10
Grid-based Exercise 2 Group ‘A’ (Knowledge Type Questions) (1 Mark Each) 1. What is nervous system ? 2. What is cerebrospinal fluid ? Write down its main function. 3. What is spinal cord ? Where is it located ? 4. Write down the major functions of spinal cord. 5. What is a sensory nerve ? 6. What is endocrine system ? 7. How many types of glands are there ? Name them. 8. Define exocrine glands. 9. What is a hormone ? 10. Where is pituitary gland located ? 11. Write the name of any two membranes that completely cover the brain. 12. Where is cerebro-spinal fluid found ? 13. What is ganglion ? 14. Write the name of hormone and gland that controls blood sugar. 15. Write two main functions of cerebellum. Group ‘B’ (Understanding Type Questions) (2 Marks Each) 16. Brain is considered as the centre of all senses, why? 17. Write any two differences between sensory neuron and motor neuron. 18. Hormone is called a chemical messenger, why ? 19. Pancreas is called mixed gland, why ? 20. Write any two differences between exorine gland and endocrine gland. 21. Why is pituitary gland called master gland ? 22. Write any two differences between cerebrum and cerebellum. 23. Adrenal gland is called an emergency gland, why? 24. ‘Endocrine glands are very important even they are small in size’. Give any two reasons to justify this statement. 25. Write two differences between afferent nerve and efferent nerve ? GREEN Science (Biology) Book-10 297
Group ‘C’ (Application Type Questions) (3 Marks Each) 26. Write any three functions of medulla oblongata. 27. Name the hormones produced by pituitary gland and mention the major function of each hormone. 28. Draw a neat diagram showing the structure of human brain. 29. Describe the structure of neuron with a neat figure. 30. Write any three functions of nervous system. Group ’D’ (Higher Abilities Type Questions) (4 Marks Each) 31. Study the given figure and answer the following questions. A i. Name the given figure. B ii. Name A and B. C iii. Name any two functions of C. 32. In which part of the body is the thyroid gland found ? Write name of the hormone secreted by this gland and its one function. What symptoms are seen due to oversecretion of that hormone ? 33. What happens in our body when there is hyposecretion or hypersecretion of following hormones. i. Parathormone ii. Insulin 34. Write down the position of the following glands in our body. Name the hormones produced by them. Also, write down the functions of each hormone. i. Thyroid gland ii. Parathyroid gland 35. Write down the position of the following glands in our body. Name the hormones produced by them. Also, write down the functions of each hormone. i. Testes ii. Ovary 298 GREEN Science (Biology) Book-10
UNIT Blood Circulation in 16 Human body Weighting Distribution Theory : 5 Practical: 1 Before You Begin In human body, there is a system (group of organs) to transport nutrients required for cells and tissues. This system is called blood circulatory system. It transports respiratory gases (digested food) and waste products from one part of body to another with the help of blood. Blood circulatory system consists of three components. They are heart, blood and blood vessels. In blood circulatory system, heart acts as a pumping organ, blood acts as a circulatory medium and blood vessels acts as pipes or tubes to transport blood to different parts of the body. In this unit, we will study the composition of blood, structure of heart, circulation of blood, blood pressure, blood sugar and uric acid. Learning Objectives Syllabus After completing the study of this unit, students will be able to: • Introduction to blood circulatory i. describe the composition and functions system of blood. • Blood : Structure and functions • Heart : Structure and working ii. explain the structure of human heart with a neat and labelled figure. mechanism • Blood vessels iii. explain blood circulation in human body – Arteries with labelled figures. – Veins – Capillaries iv. introduce blood pressure, blood sugar • Blood circulation and uric acid. • Blood pressure and its types • Causes of high blood pressure • Diabetes (Blood sugar) • Uric acid Glossary: A dictionary of scientific/technical terms blood : red coloured fluid tissue made of RBC, WBC, platelets and plasma heart : a muscular organ which pumps blood to different parts of body blood vessels : the tubes or pipes through which blood flows arteries : the thick-walled blood vessels which pump blood away from the heart veins : the thin-walled blood vessels which collect blood towards the heart GREEN Science (Biology) Book-10 299
Blood Circulation in Human Body Human body consists of different systems which are responsible to perform specific functions. There is a system which is responsible for transportation of various substances from one part of body to another with the help of blood. This system is commonly known as blood circulatory system. The system formed by heart, blood and blood vessels which transports various materials from one part of the body to another is called the blood circulatory system. The blood circulatory system transports digested food, oxygen, etc. to various parts of the body. It also transports waste materials like carbon dioxide, urea, uric acid, etc. to the excretory organs for their removal from the body. Similarly, blood circulatory system transports hormones and helps to maintain body temperature. It also regulates the amount of water and minerals in the body. The human blood circulatory system consists of three main parts. They are: (i) Blood, (ii) Heart and (iii) Blood vessels. Blood circulatory system Blood Heart Blood vessels Auricles Ventricles Arteries Blood corpuscles Veins Plasma Capillaries RBCs(Erythrocytes) WBCs(Leucocytes) Platelets(Thrombocytes) i. Blood Plasma (55%) Leukocyte The blood is a red fluid connective tissue. It consists of various substances essential for the body. It is slightly alkaline in nature with pH Plasma value 7.4. It distributes nutrients and respiratory gases to different parts of body. It consists of plasma (55%) and blood corpuscles (45%). About 5.5 Fig. litres of blood is found in the body of Blood Thrombocyte a healthy young adult. 16.1 cells (45%) Erythrocyte Plasma Blood tissue Plasma is a straw-coloured liquid which occupies 55% of the blood volume. It contains about 90% water, 8% proteins and 2% other dissolved substances like carbohydrates, respiratory gases, waste products, etc. It also consists of various waste materials, hormones, etc. in dissolved form. 300 GREEN Science (Biology) Book-10
Search
Read the Text Version
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
- 160
- 161
- 162
- 163
- 164
- 165
- 166
- 167
- 168
- 169
- 170
- 171
- 172
- 173
- 174
- 175
- 176
- 177
- 178
- 179
- 180
- 181
- 182
- 183
- 184
- 185
- 186
- 187
- 188
- 189
- 190
- 191
- 192
- 193
- 194
- 195
- 196
- 197
- 198
- 199
- 200
- 201
- 202
- 203
- 204
- 205
- 206
- 207
- 208
- 209
- 210
- 211
- 212
- 213
- 214
- 215
- 216
- 217
- 218
- 219
- 220
- 221
- 222
- 223
- 224
- 225
- 226
- 227
- 228
- 229
- 230
- 231
- 232
- 233
- 234
- 235
- 236
- 237
- 238
- 239
- 240
- 241
- 242
- 243
- 244
- 245
- 246
- 247
- 248
- 249
- 250
- 251
- 252
- 253
- 254
- 255
- 256
- 257
- 258
- 259
- 260
- 261
- 262
- 263
- 264
- 265
- 266
- 267
- 268
- 269
- 270
- 271
- 272
- 273
- 274
- 275
- 276
- 277
- 278
- 279
- 280
- 281
- 282
- 283
- 284
- 285
- 286
- 287
- 288
- 289
- 290
- 291
- 292
- 293
- 294
- 295
- 296
- 297
- 298
- 299
- 300
- 301
- 302
- 303
- 304
- 305
- 306
- 307
- 308
- 309
- 310
- 311
- 312
- 313
- 314
- 315
- 316
- 317
- 318
- 319
- 320
- 321
- 322
- 323
- 324
- 325
- 326
- 327
- 328
- 329
- 330
- 331
- 332
- 333
- 334
- 335
- 336
- 337
- 338
- 339
- 340
- 341
- 342
- 343
- 344
- 345
- 346
- 347
- 348
- 349
- 350
- 351
- 352
- 353
- 354
- 355
- 356
- 357
- 358
- 359
- 360
- 361
- 362
- 363
- 364
- 365
- 366
- 367
- 368
- 369
- 370
- 371
- 372
- 373
- 374
- 375
- 376
- 377
- 378
- 379
- 380
- 381
- 382
- 383
- 384
- 385
- 386
- 387
- 388
- 389
- 390
- 391
- 392
- 393
- 394
- 395
- 396
- 397
- 398
- 399
- 400
- 401
- 402
- 403
- 404
- 405
- 406
- 407
- 408
- 409
- 410
- 411
- 412
- 413
- 414
- 415
- 416
- 417
- 418
- 419
- 420
- 421
- 422
- 423
- 424
- 425
- 426
- 427
- 428
- 429
- 430
- 431
- 432
