Class 10 Science Solutions Nepal

NOTE Soap produces insoluble scum with hard water. So, it is not suitable washing with hard water.
Soap is biodegradable in nature. So, it does not cause chemical pollution.

Detergent

Detergents are the sodium salt of long chain benzene sulphonic acid or long chain alkyl benzene
sulphate which are mostly non-biodegradable with more cleaning property.

Detergents are also known as soapless soap because they have similar action with
soap but chemically they are different. Some examples of detergent are sodium lauryl
sulphate, alkyl benzene sulphonate, sodium pysrophosphate, etc.

Detergents have following characteristics so they are more popular than soap.
i. Detergent powder or washing powder has more cleansing power than the
soap.
ii. They are easily soluble in hard water so they can be used with hard water
but soap is less soluble in it.
iii. They are cheap in cost because they are manufactured from the petroleum
bi-products.
iv. Soap produces scum with hard water but detergents do not produce it.

NOTE Detergent does not produce insoluble scum with hard water. So, it is also suitable washing
with hard water. Detergent is non-biodegradable in nature. So, it causes chemical pollution.

MEMORY TIPS

Detergent powder contains about 15-30% of synthetic detergent, sodium silicate, sodium
carbonate, sodium sulphate and some bleaching agents like sodium perborate. To make it
attractive and popular, colours and perfumes are also added.

Differences between soaps and detergents.

S.N. Soaps S.N. Detergents

1. They are sodium salts of long 1. They are sodium salts of long chain

chain fatty acid. benzene sulphonic acid or long

chain alkyl benzene sulphate.

2. They are insoluble or less soluble 2. They are easily soluble in hard

in hard water. water.

3. They are mostly biodegradable. 3. They are mostly non biodegradable.

4. They are prepared from fat, 4. They are prepared from petroleum

sodium hydroxide and sodium by-products, concentrated sulphuric

chloride. acid and sodium hydroxide.

PLASTICS

Plastics are man-made polymers which are used in our daily life and are found in different
shapes, sizes and colours.

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Plastics are solid at room temperature and become liquid or semi-solid on heating.
Hence, most of the plastics are recycled into desired shapes and sizes. The word plastic
was derived from the Greek word plastiko. It means plastic is a substance which can
change its shape. Plastics are made from many monomer molecules. When many
monomer molecules are heated, they join together and give polymer molecule. This
process is called polymerization.

Characteristics of plastics

1. They are cheap, light and easily available in different shapes and sizes.
2. They are bad conductors of heat and electricity.
3. They do not react with acid, base, salt and other chemicals.
4. They are resistant to corrosion.
5. They are coloured easily and can be made transparent.

Classification of plastics

There are two types of plastics. They are a. Thermoplastic and b. Thermosetting plastic

a. Thermoplastic

The plastic which becomes soft on heating and can be remoulded into a desired shape is called
thermoplastic. For example, polyvinyl chloride, polystyrene, etc. In thermoplastic, the
monomer molecules are joint together by linear bonding. So, they can be changed into
different shapes.

Polyethylene

It is a polymer of ethylene molecules which becomes soft on heating. It is a bad

conductor of heat and electricity and does not show any sign corrosion. Hence, it is

used to make insulating of electric wires, pipes, buckets, packaging materials, etc.

n (CH2 = CH2) Polymerization n (– CH2 – CH2 –)n

Ethylene Polyethylene

Polystyrene

It is a polymer of styrene molecules which becomes soft on heating. It is hard,
transparent and light in weight. It is used to make toys, ceiling tiles, pipes, thermocot,
insulators, etc.

Polyvinyl chloride (PVC)

It is an example of thermoplastic. It is formed by the combination of many vinylchloride
molecules. It is used to make pipes, raincoats, sole of the shoes, hand bags, bottles, etc.

(CH = CH Cl)n Polymeriza tion (– CH2 – CH nCl)
2

Vinyal chloride Cl

(Polyvinyl chloride)
PVC

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b. Thermosetting plastic

The plastic which does not become soft on heating and cannot be remoulded into a desired shape
is called thermosetting plastic. For example: Bakelite, Melamine, etc. In thermosetting
plastic, there occurs cross link bonding among the monomer molecules. So, it is not
possible to change thermosetting plastic into other shapes.

i. Bakelite: It is an example of thermosetting plastic which is formed from
formaldehyde and phenol. It does not become soft on heating and cannot be
remoulded into desired shapes. It is blackish brown, hard and brittle. Due to
its hard nature, it is used to make handles of pressure cookers, kettles, electric
plugs, switches, etc.

ii. Melamine: It is an example of thermosetting plastic which does not become
soft on heating and cannot be remoulded into desired shapes. It is used to make
cups, plates, bowls, saucers, etc.

Differences between thermoplastics and thermosetting plastics.

Thermoplastics Thermosetting plastics

1. Those plastics which become soft on 1. Those plastics which do not become

heating are called thermoplastics. soft on heating are called thermosetting

plastics.

2. They can be remoulded into desired 2. They cannot be remoulded into desired

shapes. shapes.

3. They are soft, weak elastic and less 3. They are hard, strong, non-elastic and

brittle. more brittle.

For example: nylon, polyvinyl For example: bakelite, melamine, etc.
chloride (PVC) etc.

Common uses of plastics

1. They are used to make insulators of electric wires.
2. They are used to make parts of vehicles instead of metals.
3. They are used in place of natural fibres, leathers, stones, woods, metals, glasses, etc.
4. They are used to make surgical instruments.
5. They are used to make medicine covers, medicine bottles, etc.
6. They are used to make pipes, bags, seat-covers, water tanks, water bags, etc.
7. They are used to make packing materials, kitchenwares, laboratory equipments, etc.

Demerits of Plastics

Plastics are man-made non-biodegradable chemical substances which are making
human life easy and comfortable. But excess use of plastics causes different types of
problems related to the environment like air, water and soil pollution. The poisonous
fume of plastic causes air pollution.

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CERAMICS

We can see different types of clay pots, cups, dishes, etc. in the market. All these dishes
are made of a special clay called ceramics. Ceramics is a word derived from Greek
word ‘Keramos’ which means potter’s clay. So it is used to make potter’s pots. Ceramics
is a special type of clay that contains Carbon, Nitrogen, Silica and Oxygen. Its chief
compound is hydrated aluminium silicate (Al2O3. SiO2. 2H2O). Other substances also
are found in it such as limestone, magnesium, carbonate, oxides of manganese and
iron. Its pure white clay is called kaolin or china clay which is specially used to make
pots, cups, plates, dishes, etc.

Process for making ceramic products

The following steps are taken to make ceramic products. First, the soil is crushed and
ground into a powder form. Now, it is sieved from the soil to obtain fine clay. Then,
the clay is kneaded with water. When it is well kneaded, it is put in different keys or
made into different objects with the help of hands or potter's wheels. Different objects
are kept in the sunshine for some time or some days. After that, objects are fired in
a kiln (furnace) at a high temperature to make fully dry and hard. Due to different
chemical reactions, objects become porous. To shine, to make smooth and water proof
as well as attractive, objects of ceramics are coated with tin oxide or lead oxide and
heated again. This process of coating is called glazing. At last, colour and painting is
done.

Features of ceramics

1. Ceramic objects are hygienic to use because they are not affected by acids, bases,
gases, salts, and other chemicals.

2. It has high thermal resistant power.
3. It is poor conductor of heat and bad conductor of electricity.
4. Its objects are hard, brittle and attractive.

Uses

1. Ceramics is used to make clay pots, cups and different dishes.
2. It can be used in electrical appliances as it is a bad conductor of electricity.
3. It can be used to make bathroom tiles, commodes, etc.
4. It can be used to make household pottery.
5. It can be used to make containers that need strong heating. For example:

porcelain basin.

FIBRES

In our daily life, we see and use hair-like strands, threads, ropes, nets, clothes, blankets,
caps, sweaters, gloves, rugs, cotton, jute, etc. Such types of materials and things, plants,
fruits, foods or birds which have hair-like strands in them are called fibres.

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Fibres are hair-like strands of plants, animals or any substances whose length is extremely long
in comparison to its cross section area are called fibres.

Fibres are used for different purposes in our daily life. There are two types of fibres;
1. Nature fibres
2. Artificial fibres

1. Natural fibres

Natural fibres are those which are obtained from natural things like animals, insects,
plants or fruits. Natural fibres can be divided into two groups:

a. Animal fibres
b. Plant fibres

a. Animal fibres: Animal fibres are those fibres which are directly obtained from
animals and insects. Wool and silk are its example; yaks, goats, sheep, rabbits,
silkworms, etc. are the sources of animal fibres.

b. Plant fibres: Plant fibres are those materials which are obtained directly from
the plants. Jute, hemp, cotton, bombax, etc. are some examples of plant fibres.

2. Artificial fibres

Artificial fibres are those fibres which are made or prepared artificially or chemically.
Rayon, nylon, polyester, olefin, etc. are the examples of artificial fibres. Artificial fibres
are of two types:

a. Recycled or regenerated fibres
b. Synthetic fibres

a. Recycled or regenerated fibres: Recycled or regenerated fibres are those fibres
which are artificially prepared from natural materials. Rayon is one of them. It is
prepared from the cellulose present in cotton and pulp present in wood. Rayon
looks like silk, so it is also called artificial silk.

b. Synthetic fibres: Synthetic fibres are those fibres which are prepared through
chemical process. Nylon, polyester, acrylic, olefin etc. are the examples of
synthetic fibres.

Importance and uses of fibres

Different types of fibres have different uses and importance in our daily life.
i) Pillows and quilts are made from bombax fibres.
ii) Sacks are made from jute fibres.
iii) Comfortable garments are prepared from cotton fibres.

INSECTICIDES

There are different types of insects and pests in our surroundings. Sometimes, very
new types of insects are found in a large number. Some insects are harmful and

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poisonous but some insects are beneficial for the environment i.e. soil, plants, animals
and human beings as well. Insecticides are used to kill, prevent or control these
harmful and poisonous insects and pests. Some insects die when they eat insecticides,
some of them die when they come in contact with insecticides and some of them can’t
reproduce and grow themselves.

So, insecticides are those artificial chemical substances which are used to kill, control or prevent
harmful and poisonous insects and pests.

Types of insecticides

i. Organic insecticides

Organic insecticides are prepared by the combination of carbon, hydrogen, oxygen
and other elements like chlorine, phosphorous, etc. These organic insecticides are of
three types according to their chemical combination.

a. Chlorinated organic insecticides: Carbon, hydrogen and oxygen are the main
elements of all organic insecticides. But when the chemical called chlorine is
added as an additional element, it is called chlorinated organic insecticide.
BHC (Benzene hexa-chloride), DDT (Dichloro diphenyl trichloro ethane),
Aldrene, Dieldrene, Methoxychlor, etc. are the examples of chlorinated organic
insecticides. The main features of these insecticides are that they can resist for a
long time effectively.

b. Organophosphate insecticides: When phosphorus is added as an additional
element, it is called organophosphate insecticide. The main features of these
insecticides are, they are less stable, degradable and highly toxic to other
animals. Melathion, parathion, phosdrin, etc. are some of the examples of these
insecticides.

c. Carbamate insecticides: These organic insecticides contain amino group (–
NH2). They are less harmful. Begon, Termic, etc. are some examples.

ii. Inorganic insecticides

Inorganic insecticides are prepared from different minerals. Calcium arsenate, lead
arsenate, fluoride and lime sulphur, etc. are inorganic insecticides, which are used to
protect cotton, fruits, vegetables, etc. from insects.

Precautions in using insecticides

Insecticides are poisonous. They should be used properly, as careless and random use
of these insecticides creates different types of hygienic and environmental problems.
So, the following precautions should be taken while using these insecticides.

1. Before using insecticides, proper training should be taken on how to use
them.

2. Appropriate quantity according to soil and plants should be used.
3. If possible, only short-term insecticides should be used.

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4. Masks and gloves should be used while using insecticides. The dress
should be changed and hands, legs, mouth should be washed properly
with soap after their use.

5. Insecticides should be stored and kept away from the reach of the children
and foods.

Features of good insecticides

1. They should not have side effects in the health of human beings as well as
animals.

2. They should be easily degradable and should have a short-term effect.
3. Useful insects should not be killed and disturbed by the use of these

insecticides.
4. Crops, fruits, vegetables should not lose their natural quality.
5. Environmental elements such as water, air, and soil should not be polluted

after their use.

Advantages of insecticides

1. Insecticides help to kill and control harmful insects.
2. Crops, fruits and vegetables are protected from different diseases.
3. Insecticides help farmers to get desired crops, vegetables and fruits.

Disadvantages of insecticides

There is no doubt that insecticides are helpful to protect from different harmful insects
but they are not free from side effects and disadvantages. Some of the disadvantages
of insecticides are as follows:

1. Most of the insecticides create air, water and soil pollution.
2. They are not easily degradable.
3. Some insecticides leave deposit in fruits, crops, vegetables, etc.
4. Some insecticides kill useful insects as well.
5. Different types of side effects are caused in the body of human beings,

animals, and birds by DDT.

Effects of DDT

1. DDT causes air, water and soil pollution.
2. DDT used foods create side effects in the kidneys, liver, lungs.
3. It causes lung diseases.
4. It has adverse effects on birds' egg.
5. Photosynthesis and transpiration are reduced due to the dusting of the

leaves of the plants.

FERTILIZERS

Fertilizers are those chemicals or organic substances which contain essential nutrients for
plants, fruits and vegetables for their healthy and good growth and production. Regular
production of different types of crops, fruits and vegetables decreases the fertility of

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soil. Different types of fertilizers help to maintain the fertility i.e. nutritive elements of
the soil. They are used in the soil for plants, vegetables, fruits, etc. There are two types
of fertilizers.

1. Chemical fertilizers
2. Organic fertilizers

1. Chemical fertilizers

Chemical fertilizers are those fertilizers which are prepared through chemical reactions and
processes which are also called inorganic fertilizers. These inorganic fertilizers contain
mainly nitrogen phosphorus and potassium elements. Plants need these elements for
their growth, development and seed production. We can divide chemical fertilizers
into three groups on the basis of the elements containing in them.

a. Nitrogenous fertilizers: In these fertilizers, nitrogen (N) is present as a chief
element. For example;
i) Calcium cyanide Ca(CN)2
ii) Urea NH2CONH2
iii) Ammonium nitrate NH4NO3
iv) Ammonium sulphate (NH4)2 SO4

b. Potassium containing fertilizers: These fertilizers mainly supply potassium to
the plants. For example;
i) Potassium carbonate K2CO3
ii) Potassium chloride KCl
iii) Potassium sulphate K2SO4
iv) Potassium nitrate KNO3

c. Phosphorus fertilizers: These fertilizers contain mainly phosphorus elements.
For examples,
i. Bone meal
ii. Triple super phosphate 3Ca (H2PO4)2
iii. Ammonium phosphate (NH4)3 PO4
iv. Calcium super phosphate Ca (H2PO4)2 2CaSO4

2. Organic fertilizers

Organic fertilizers are called natural fertilizers or manure. Natural fertilizers are obtained
from natural processes. These organic fertilizers are obtained from the decomposition
of plants, dead animals or their waste products. Organic fertilizers are very suitable
for crops and plants because they supply all the essential nutritive elements naturally
and there are no side effects. There are two types of organic fertilizers.

i) Green manure: When green plants are grown, ploughed and mixed in the soil
to provide fertility to the plants and crops, this is called green manure.

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ii) Compost manure: Compost manures are also natural fertilizers, which are prepared
from dead, decayed and decomposed parts of animals and plants or their waste products.
To prepare compost manure, mixture of dead plants, animals or their waste
products are kept within the soil. Sometimes, lime is also added to it. After some
time, due to micro organisms, it is decomposed and manure is ready to use.
It increases the fertility of the soil but it has a low concentration of Nitrogen,
Phosphorus and Potassium.

Roles of compost manure
i. They contain organic substances, which help for the healthy growth and

development of plants.
ii. They do not cause chemical pollution as they are biodegradable.
iii. They do not change the acidic and basic nature of the soil.
iv. They maintain the water holding capacity of the soil.
v. They help in environmental conservation protecting them from the chemical

pollution.
vi. They help to reduce environmental pollution by decaying dead bodies of

animals and plants.

Differences between organic and chemical fertilizers.

Organic fertilizers Chemical fertilizers

1. Organic fertilizers are called natural 1. These fertilizers are called artificial

manure. fertilizers.

2. They don’t supply enough nitrogen, 2. They contain enough nitrogen,

phosphorus and potassium to the phosphorus and potassium elements.

growing plants.

3. They are prepared from the plants, 3. They are prepared through chemical

animals or natural waste. processes.

4. They don’t pollute air, water and soil. 4. They pollute air, water and soil.

5. Plants absorb them very slowly. 5. Plants absorb them very quickly.

6. The products have no side effects in 6. The products create side effects in the

the human body and animals. body of human beings and animals.

Significance of Nitrogen (N), Potassium (P) and Phosphorous in fertilizers

Nitrogen

Nitrogen is one of the most important and essential nutrients for plants and crops. It
fulfills the following needs of the plants.

i. It helps in fast growth of plants.
ii. It helps in the formation of protein, protoplasm and chlorophyll in plants.
iii. It helps to develop more flowers, fruits and seeds.

The deficiency of nitrogen in plants makes leaves yellow, and there is no fast growth
of plants and its size, enough production of flowers, fruits and seeds.

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Potassium
i) With the help of potassium fertilizers, plants make food through the
photosynthesis process.
ii) It also helps in the synthesis of protein, fat, sugar, cell division, growth of
leaves, flowers, fruits, etc. in plants.
iii) It helps to resist different types of diseases.

Phosphorus
i) The roots of plants are developed with the help of this fertilizer.
ii) With the help of phosphorus nutrients, ripening of fruits and healthy
development of seeds take place.
iii) Cell division and development of buds are take place in plants by the
phosphorus elements.

Three groups of fertilizer

Fertilizers can be divided into three groups according to the number of basic nutrients
supplied.

(a) Single fertilizers: When the fertilizers supply only one basic nutrient out of three
basic nutrients i.e. nitrogen, phosphorus or potassium are called single fertilizers.
Calcium nitrate, potassium sulphate, potassium chloride are its examples.

(b) Mixed fertilizers: These fertilizers supply more than one basic nutrient.
Examples: potassium nitrate, ammonium phosphate, etc.

(c) Complete fertilizers: Those fertilizers which supply all three basic nutrients i.e.
nitrogen, phosphorus, and potassium are called complete fertilizers.

Disadvantages of using fertilizers

Nowadays due to the rapid population growth, fast and unorganized urbanization,
there is a shortage of natural things in the market. People are trying to earn money
within a short period. For this, they are using such types of fertilizers which help in
the fast growth and more production. Using excessive chemical fertilizers leads to air,
water and soil pollution. When nitrogenous fertilizers are mixed with water sources,
they help in the unusual and rapid growth of aquatic plants. These plants use-up
oxygen mixed in water and aquatic animals die due to the lack of oxygen. If small
children drink nitrogen containing water, their growth stops and they become dwarfs.

Precautions while using fertilizers

i) We should take training from the J.T.A about how to use fertilizers.
ii) Before using fertilizers, the soil must be tested.
iii) Fertilizers should not be used in an excessive amount and randomly.
iv) They should be used properly, in proper time as well as in an appropriate

quantity.

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v) Nitrogenous fertilizers should be used very carefully and should not be kept in
wooden dust, coal, dry leaves or fuel because they have easy burning feature.

vi) Overuse of fertilizers damages plants.
vii) We should use masks, gloves while using fertilizers.
viii) We should keep them away from the reach of children, animals, etc.
ix) We should not keep them near edible things, foods or water.
x) We should change the dress after using and hands, mouth and legs should be

washed with soap properly.

CHEMICAL POLLUTION

The process of degradation in the quality of air, water and land by mixing unwanted chemicals
is called chemical pollution.

When different types of foreign and unwanted chemicals are mixed in air, water and
land, these things become dirty and unhealthy or lose their original quality, This state
of air, water and land is called pollution. From everyday human activities such as use
of chemical fertilizers, insecticides pesticides, detergents, dyes, synthetic fibers, waste
water and pollutants from the factory, different gases emitted from the industry, etc.
degrade the health quality of the environment. The unwanted, imbalanced, excessive
and unlimited chemicals mixed in the environment degrade its quality, which is called
chemical pollution.

Causes of chemical pollution

Human activities are the responsible factors to cause chemical pollution in the
environment. How are these activities creating chemical pollution? It is discussed below.

1. Chemical fertilizers used by farmers in the fields: Due to the rapid development
of agricultural science, farmers use more and more chemical fertilizers to produce
more quantity of crops in place of organic compost. Such types of fertilizers
decay the quality of land and they dissolve in rainy water and reach different
water sources such as rivers, ponds, streams etc. Fertilizers that contain more
nitrogen elements, help in the excessive growth of aquatic plants. These plants
use-up all the oxygen dissolved in water. It creates lack of oxygen in water and
the aquatic animals die due to the lack of oxygen in the water. It is called a
biological oxygen demand (BOD) value.

2. Excessive use of insecticides and pesticides: Not only fertilizers, but farmers
also use more quantity of insecticides and pesticides to kill insects and pests in
the fields. These toxic insecticides and pesticides such as aldrene, dieldrene and
heavy metals like lead, cobalt, mercury, etc. also pollute the air, water and land.

3. Household plastics and wastes: Houses are also the great sources of chemical
pollution. Different types of solid wastes of food, vegetables, clothes, ceramics,
detergents, soaps, plastics, etc. create chemical pollution. Some of the non-
degradable wastes cause a long-lasting effect in the environment.

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4. Toxic gases, smoke, dust and other particles emitted from the industry:
Factories and industries are the great sources of chemical pollution from where
different types of gases like carbon dioxide, carbon monoxide, sulphur trioxide,
etc. are the pollutants for air. When rainwater and other different types of gases
are mixed, acids like sulphuric acid, nitric acid, carbonic acid, etc. are formed.
The excessive emitting of the poisonous gases from the industries in the air
causes acid rain fall and burns plants, animals, soil and important monuments.
Global warming is the result of the excessive outcome of the carbon dioxide,
methane, sulphur dioxide, etc. which create greenhouse effects.

5. Waste water, chemical, drugs, and other polluted liquid coming out from
the industries, hospitals, research centres etc: Industries, factories, hospitals,
research centres, laundry centres, bathing and washing centres, etc. throw out
different colourful water, mixtures, waste and dirty water which mix in water
sources and pollute the water. Such water decays the fertility of the land. Bad
smells come out and pollute the air.

6. Different food colours: The shopkeepers use different types of colours to attract
customers and users which are made of different chemicals that affect our health.

7. Different types of dyes and detergents: Different industries like leather,
textiles, carpet, etc. also cause chemical pollution by releasing different harmful
colours, dyes and detergents such as peroxide, hypochloride, sodium hydroxide
and other bleaching agents. These dyes and detergents degrade the quality of
water, land and air as well. Water sources are badly polluted due to the mixing
of detergents which are non-biodegradable cleansing compounds.

8. Metallic particles: Different types of metallic particles such as lead, chromium,
mercury, arsenic, etc. come out from different research centres, industries,
automobiles, hospitals, etc. and they mix in the water sources and land. When
human beings, animals, birds and aquatic animals use or take these chemicals in
different forms, it causes pollution.

9. Warfare: Different mini and major warfares have created air, water and land
pollution.

Controlling measures of chemical pollution

Chemical pollution is the greatest threat to the existence of all living beings. We human
beings are the prime factor of the chemical pollution. In return, we become its prey
and victims as well. The following measures can be recommended to control chemical
pollution.
i. Use of nuclear weapons, bombs and chemicals must be stopped.
ii. Unorganized urbanization should be changed into organized urbanization.
iii. Over population growth especially in developing counties must be controlled.
iv. Sustainable development must be done.

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v. Industries, factories, research centers, hospitals, etc. must be established far from
the residental areas and they must follow industrial code so as not to pollute the
environment.

vi. Farmers must be given training on the use of chemical fertilizers, insecticides,
pesticides in proper ways.

vii. Farmers must be incouraged to use bio-compost in the field.
viii. Manufacture of weapons, bombs and toxic chemicals must be stopped.
ix. Excessive production of non-degradable materials such as plastics should be

stopped and discouraged. Beside recycling, and reuse of the things must be
encouraged.
x. Waste water and liquid coming from the industry must be purified before
throwing it in the water sources and fields.
xi. Chimneys must be used in the industry.
xii. Toxic gases should not be allowed to be mixed in the air.
xiii. Solid waste gas such as plastics, clothes, glasses, carpet ceramics, etc. should be
managed property.
xiv. The most important measure is to create awareness among the people on the
effects of chemical pollution.

SOLID WASTE

Wastes are the materials which are discarded after use or the useless byproducts of
any processes. Solid or semisolid materials resulted from anthropogenic and even natural
activities that are useless, unwanted, or hazardous are called solid wastes. Solid wastes
include garbage, rubbish, ashes, construction and demolition debris, dead animals,
sewage solid, industrial waste, mining waste and agricultural waste. Among them,
wastes from garbage, rubbish, construction and demolition debris, sewage solid also
termed as municipal wastes, and hazardous wastes are of major concern as they
degrades the environment as well as the human health.

Based on the ability of their natural decomposition, solid wastes are categorized as
biodegradable waste and non-biodegradable waste. Wastes that are able to decompose
naturally due to the action of microbes are called biodegradable wastes. Some
examples are food waste, fruits and vegetable peels, dead animals, plants and their
parts, faeces of human and animals, natural fabrics, papers, etc. Wastes that are unable
to decompose naturally due to the action of microbes are called non-biodegradable
wastes. Examples are plastic materials, hardwood, rubber, glass, metal scraps etc.

Solid waste management

Solid wastes are responsible for the degradation of the environment in the form of
air, water and soil pollution. Environmental pollution finally affects the health and
well-being of people as causes various diseases like jaundice, typhoid, dysentery, eye
diseases, skin diseases, etc. Population is increasing and towns and cities are expanding
rapidly. Solid wastes are being generated in larger and larger amounts. Therefore
solid waste must be managed effectively and efficiently with special attention to the
safeguard environment and the human health. The steps provided below should be

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practiced to manage the municipal solid waste and the household should help it by
segregating waste at the source.

a. Segregation at source: Waste segregation at the source is the initial step of solid
waste management. Biodegradable and non-biodegradable wastes should be
separated and kept in separate bins. The recyclable wastes like glasses, cans,
metal scraps can also be kept in separate bins.

b. Collection and transportation: The waste should be collected by appropriate
vehicles and transported to the waste collection centers. Recyclable wastes are
collected separately and transported to recycling/processing centers. Door to
door collection or collection from a common site can also be practiced. The waste
should be covered properly while hauling.

c. Segregation and processing: Metallic waste, glass, metal scraps and any other
recyclable materials are segregated at collection centers. Magnetic separation
is used to separate the metallic waste from the refuse. Similarly, gravity
separation is used to separate heavy waste from lighter ones. Recyclable wastes
are transported to recycling centers. Degradable wastes are transported to
processing centers for manufacturing compost. Segregation and processing
reduce the amount of waste to be disposed.

d. Disposal: There are a number of waste disposal methods like sanitary landfilling,
composting, incineration, etc. Different kinds of wastes are disposed by different
methods.
i) Composting: Composting is the process of producing compost manure
through the natural decomposition of biodegradable wastes by using
natural or activated microorganism. Wastes are dumped in compost pits
by making layers separated by the layers of soil. The process may or may
not need a regular turnover depending upon the types of composting. It
takes about a month or more for the compost to be ready.
ii) Sanitary landfilling: Both biodegradable and non-biodegradable wastes
can be disposed in sanitary landfill/dumping sites. Here, the waste is
disposed and compressed and compacted. The compacted waste is covered
by a layer of soil and the numbers of waste layers form a new landform in
the end life. Landfill sites can accommodate a large amount of waste and
can be operated for many years. Initial Environmental Examination (IEE)/
Environment Impact Assessment (EIA), etc. is necessary for the selection
of landfill sites to safeguard the environment and public health from the
consequences of using a landfill.
iii) Incineration: Incineration is the process of disposal of solid waste by
burning it in a furnace at a high temperature in chambers called incinerators.
This process is used to dispose hazardous waste like medical waste from
hospitals or combustible and corrosives solids. Ash is the end product of
incineration, which requires much less time and space for decomposition.
It is one of the widely used solid waste treatment/ disposal process.

210 | Materials Used in Daily Life

MODEL QUESTIONS ANSWER

1. Why do we add gypsum to cement?
Ü Gypsum (CaSO4. 2H2O) is added to the cement clinker to increase the quality of

cement as well as to regulate the setting of cement by increasing the settling time.

2. What is glazing and why is it done?
Ü Coating of ceramics by tin oxide or lead oxide during their manufacturing

is called glazing. Glazing makes the ceramic objects smooth, attractive and
waterproof.

3. Organic and chemical fertilizers are used together. Why?
Ü Organic fertilizers are poor in basic nutrients (i.e. N, P, and K). So it is fulfilled

by adding chemical fertilizers.

4. Environmentalists advise us not to use plastic. Why?
Ü Plastics are non-biodegradable chemical substances. They do not decay. Their

burning produces poisonous smoke. Hence, they cause air, water and soil
pollution. Due to the above reason, environmentalists advise us not to use plastic.

5. Define NPK fertilizer. Why is it called a complete fertilizer?
Ü The fertilizer which supplies nitrogen, phosphorus and potassium is called

NPK fertilizer. The basic nutrients required for growing plants are nitrogen,
phosphorus and potash that are supplied by NPK fertilizer. So, it is called a
complete fertilizer.

6. Define monomer, polymer and polymerization.
Ü Monomers: The simple organic compounds which are used to make polymer are

called monomers. For example: vinyl chloride, ethene, glucose, amino acid, etc.

Polymers: The complex organic compounds which are obtained by repeating
many monomer molecules are called polymers. For example: PVC, polyethene,
protein, etc.

Polymerization: The process by which polymer is obtained by repeating
monomer molecules is called polymerization.

SUMMARY
 The fine grey powder of calcium silicate and calcium aluminate which becomes hard and

strong when it is mixed with water and left for some time is called cement.
 The homogeneous mixture of different types of metallic silicates which is hard transparent

and amorphous in nature is called glass.
 Sodium salt of long chain of fatty acid which has cleansing property in water is called soap.
 Detergents are the sodium salt of long chain benzene sulphonic acid or long chain alkyl

benzene sulphate which are mostly non-biodegradable with more cleaning property.
 Plastics are man-made polymers which are used in our daily life and are found in different

shapes, sizes and colours.

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 The plastic which becomes soft on heating and can be remoulded into a desired shape is

called thermoplastic.
 The plastic which does not become soft on heating and cannot be remoulded into a desired

shape is called thermosetting plastic.
 Fibres are hair-like strands of plants, animals or any substances, whose lenth is extremely long

in comparison to its cross section area, are called fibres.
 Insecticides are those artificial chemical substances which are used to kill, control or prevent

harmful and poisonous insects and pests.
 Fertilizers are those chemical or organic substances which contain essential nutrients for

plants, fruits and vegetables for their healthy and good growth and production.
 Chemical fertilizers are those fertilizers which are prepared through chemical reactions and

processes. They are also called inorganic fertilizers.
 Organic fertilizers are called natural fertilizers or manure.
 Compost manures are also called natural fertilizers which are prepared from dead, decayed

and decomposed parts of animals and plants or their waste products.
 Degradation of components of the environment (air, water, soil, etc.) due to the presence of

chemical that are neither naturally present or are in higher amounts than their natural values

is called chemical pollution.
 Surface runoff from such agricultural fields carries a large amount of nutrients in the water

bodies and pollutes water bodies.
 Global environmental problems like global warming, climate change, ozone layer depletion, etc.

and local environmental problems like acid rain, reduction in visibility, extinction of flora and

fauna, etc. are primarily due to the chemicals from automobiles and industries.
 Pesticides like DDT, BHC, Aldrin, Dieldrin, Carbosulfan, Endosulfan, Malathion, etc. are well

known for their toxic effects in humans and the environment.
 Solid or semisolid materials resulted from anthropogenic and even natural activities that are

useless, unwanted, or hazardous are called solid wastes.
 Solid wastes are divided into biodegradable waste and non-biodegradable waste.
 Solid waste must be managed effectively and efficiently with special attention to safeguard the

environment and human health.
 Segregation at the source, collection and transportation, segregation and processing and

disposal are the steps taken for solid waste management.
 Sanitary landfilling and incineration are popular solid waste disposal methods.

EXERCISE

1. Define the given terms:

(a) Cement (b) Plastics (c) Ceramics
(f) Cement clinker
d) NPK fertilizer (e) Cement mortar (i) Concrete
(l) Sanitary landfilling
(g) RCC (h) Cement

(j) Chemical pollution (k) Solid waste

(m) Incineration (n) Composting

212 | Materials Used in Daily Life

2. Write differences between:

(a) organic fertilizer and chemical fertilizer
(b) thermoplastic and thermosetting plastic
(c) soap and detergent
(d) soft glass and hard glass
(e) chemical fertilizers and chemical pesticides
(f) biodegradable and non-biodegradable solid waste
(g) incineration and sanitary landfilling

3. Give reasons.
(a) PVC is not used to make the handle of a pressure cooker.
(b) Detergents are called soapless soap.
(c) We should avoid the use of plastic.
(d) RCC is stronger than cement concrete.
(e) NPK is called a complete fertilizer.
(f) Gypsum is added to the cement.
(g) Runoff from agricultural fields with intensive chemical fertilizers can cause
oxygen deficit in ponds.
(h) If pesticides kill all bees less food will be produced.
(i) Plastic is an important chemical of the environmental pollution.

4. Write full form of:

(a) PVC (b) DDT (c) BHC (d) RCC

5. Write raw materials of the given substances.

(a) Soap (b) Cement (c) Quartz glass

(d) Borosilicate glass (e) Detergent

6. Write any three uses of the given substances.

(a) Cement (b) Plastics (c) Ceramics (d) Glass (e) Fibres

7. Describe the process of manufacturing the given substances in brief.

(a) Cement (b) Ceramics (c) Soap (d) Borosilicate glass

8. Write any three characteristics of the given substances.

(a) Glass (b) Organic fertilizers (c) Chemical fertilizers

(d) Natural fibres (e) Plastics

9. Define borosilicate glass and write its uses.

10. Define quartz glass and write its uses.

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11. How are coloured glasses obtained?
12. What are fibres? Write different types of fibres with their examples.
13. Define chemical pollution and write its effect.
14. Describe the adverse effects of DDT.
15. Nitrogenous fertilizers help to grow aquatic plants and decrease the growth of

aquatic animals. Describe it in brief.
16. Write the importance of nitrogen, phosphorus and potassium for growing plants.
17. What is glazing? Write its use in ceramic objects.
18. What are insecticides? Write their characteristics and uses.
19. Making polythene is called polymerization. Justify this statement.
20. We use more number of plastics and ceramics. Give reasons.
21. List out the causes of chemical pollution.
22. How do cleansers pollute the environment?
23. What is the main property that makes plastic environment unfriendly?
24. Explain the global environmental problems caused by automobiles and industrial

emissions.
25. Name some pesticides that are toxic to humans and the environment.
26. Mention four ways to get rid of chemical pollution.
27. List the steps for solid waste management.

A

B GLOSSARY
C

Ceramic : object made of clay and made hard with heat

Fertilizers : substances added to soil to make plants grow successfully

Adverse : negative and unpleasant

Glazing : fitting sheets of glass onto something



214 | Materials Used in Daily Life

UNIT

14 Invertebrates

About the Scientist INTRODUCTION

Louis Pasteur We see various animals around us. Among them some are
(1822) back boned and some do not have backbones. Those animals
which do not have a backbone in their body are called invertebrates.
Louis Pasteur was born on For example, amoeba, paramecium, housefly, mosquito,
December 27, 1822 in Dole, in silkworm, honeybee, etc. Among the invertebrates, some
the region of Jura, France. His are beneficial and some are harmful to us. Silkworms and
discovery that most infectious honeybees are beneficial insects. In this unit, we will discuss
diseases are caused by germs, about the lifecycle of silkworms and honeybees.
known as the “germ theory
of disease,” is one of the most A. SILKWORM
important in medical history. His
work became the foundation for A silkworm is a useful insect as it produces a high quality
the science of microbiology, and a silk fibre. Silk fibre is used to produce silk clothes, shawls
cornerstone of modern medicine. and other attractive and expensive clothes. Silk is obtained
from the cocoons of silkworms. There are two types of silk
Pasteur’s phenomenal contributions moths commonly reared in Nepal. They are Eri and Seri.
Bombyx mori or Seri feeds on mulberry leaves and Eri or
to microbiology and medicine Attacus ricinii feeds on caster leaves. The cultivation of
silkworms is known as sericulture. The systematic position
can be summarized as follows: of silkworms is as follows:

First, he championed changes Kingdom- Animal

in hospital practices to minimize Sub-kingdom- Invertebrat

the spread of disease by microbes. Phylum- Arthropoda

Second, he discovered that Class- Insecta

weakened forms of a microbe Type- Silkworm

could be used as an immunization Habit and habitat

against more virulent forms of the They are found in many indigenous varieties across the
world. China was the first country to introduce sericulture
microbe. Third, Pasteur found around 2700 BC and later it was flourished in other countries.

that rabies was transmitted by External morphology

agents so small they could not The silkworm is a medium sized insect. It is creamy white
in colour. The length of a silkworm is from two to three cm.
be seen under a microscope, thus

revealing the world of viruses. As

a result, he developed techniques

to vaccinate dogs against rabies,

and to treat humans bitten by

rabid dogs. And fourth, Pasteur

developed “pasteurization,”

a process by which harmful

microbes in perishable food

products are destroyed using heat,

without destroying the food.

New Creative Science, Class 10 | 215

The body is divided into three parts i.e. head, thorax and abdomen. The head bears a
pair of compound eyes, a pair of antennae and a sucking type of mouth. The thorax
bears two pairs of wings and three pairs of legs.

The abdomen consists of ten segments containing seven pairs of spiracles. The
abdomen of the female is larger than that of the male silkworm.

Lifecycle of silkworm

The lifecycle of a silkworm completes in four stages i.e. egg, larva, pupa and adult.
The male silkworm dies after copulation and the female moth dies after laying eggs.
(i) Eggs: A female silk moth lays about 300-400 eggs in clusters on a mulberry leaf.

The eggs are whitish, small and have a round structure, which turn grey later.
On getting a favourable condition and temperature of about 18°C to 25°C, the
eggs hatch into larvae in about 10-12 days.
When there is a scarcity of mulberry leaves, the eggs are kept in cold places to
prevent from hatching.

QUESTIONS
# Why are eggs of silk moths kept in cold places?

(ii) Larva: The larva of the silkworm is grey in colour and it is a very active stage
of the lifecycle of the silk moth. The larva of the silk moth or the caterpillar is
the voracious feeder on mulberry leaves. It is only considered for eating and
growing. The larva moults for four times in sixth, twelfth, eighteenth and twenty
sixth days respectively. While moulting, the caterpillar stops feeding for some
hours.
The stage of the larva between two successive moltings is called instar. The fifth
instar is about 100 times bigger than the first instar larva. After the last moulting,
it develops a pair of salivary glands which secrete liquid silk on the lateral side
of the body. When this liquid silk comes in contact with air, it becomes hard
with fine thread, inside which the caterpillar is enclosed. This stage is known as
the cocoon or pupal case.

216 | Invertebrates

(iii) Pupa: It is the inactive stage in the lifecycle of the silkworm, which doesn’t eat
and move at all. However the histogenesis and histolysis are talking place inside
the silk cocoon. The silk thread is obtained in the pupal stage of the silkworm.

For obtaining silk thread, the cocoons are put in hot water or oven to destroy the
glue of the silk thread so they can be obtained and unwounded easily. About
one thousand metres of silk thread can be yielded from a single cocoon.

MEMORY TIPS
About, 50,000 cocoons are required to prepare a kilogram of silk.

(iv) Imago or Adult: The pupa changes into an
adult from about twelve to fourteen days.

The imago breaks the cocoon by the

secretion of alkaline fluid, which softens

the thread. The imago cannot fly

immediately but as its wings get dry, it flies

and the female lays eggs on maturity.

Hence, its lifecycle continues.

Features of silk thread Life cycle of silkworm

(1) Silk is shiny, attractive, light and durable fibre.

(2) It is strong, long and elastic fibre.

(3) It can be coloured easily.

(4) It can be dried easily.

(5) It does not decay easily.

(6) The clothes made from silk fibres are attractive, durable and expensive.

Economic importance of silkworm

(1) Silk is used to make clothes nets, surgieal stitching thread, curtains, etc.
(2) It is used for fishing.
(3) It can be blended with other fabrics to make more attractive clothes.
(4) It increases the economic condition of a person thereby uplifting the economic

status of the nation.
(5) A maximum number of women can be employed in sericulture.
(6) It can be reared in low land areas.

B. HONEY BEE

A honey bee is an invertebrate that belongs to phylum Arthropoda, class Insecta, and
is the member of subfamily Apinae.

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Honey bees are known for producing and storing honey as well as building impressive
large hives using wax secreted by the workers in a particular colony. In wild, their
hives are often located in holes of trees, rock crevices, etc. They are social insects that
live in colonies in huge numbers. Each colony contains three adult classes of honey
bees: egg-laying queens, sperm-producing male drones and infertile female workers.
These different classes of honey bees perform their own functions.

Queen bees are the fertile females that are involved in mating with the drone bees and
reproduce bees in the colony. Drone bees are the male bees and their only function is
to mate with queen bees for fertilization. Worker bees are infertile females that collect
pollen and nectar from plants, cut and shape wax, feed larvae and the queen, clean the
hive, protect the hive and queen bees, etc.

Anatomy of honey bee

Honey bees are usually oval-shaped
creatures with golden-yellow colours
and brown bands. The size and shape
of a honey bee differs according to its
types. The queen bee is the largest
bee with a large elongated abdomen,
and it is up to 2 cm in length. Drone
bees are smaller than the queen bee
but larger than workers, and worker
bees are the smallest in size and they measure up to 1.5 cm in length.
The body of a honey bee is divided into three major parts; head, thorax and abdomen.
The head consists of eyes, an antennae and feeding structures. The eyes include a
compound eye and simple eyes. Compound eyes help the bees understand colour,
light and UV rays direction while simple eyes detect the amount of light present. The
antenna detects odours and measures flight speeds. The mandible is bee’s jaw used
in eating pollen, cutting and shaping wax, feeding larvae and the queen, cleaning the
hive, grooming and fighting. Worker bees have the ability of chewing and lapping.

218 | Invertebrates

The thorax has three segments and it consists of two pairs of wings, three pairs of legs
and movement controlling muscles. Fore wings are used for flight and cooling the
body while hind limbs cool the hive. The legs of worker bees are covered with hair
and they contain a pollen basket for storing the pollen and nectar.

The sixth segment of abdomen includes the female reproductive organs in the queen
bee and the male reproductive organ in the drone. Both the queen and the worker bees
have a stinger at the end of their abdomen.

Life cycle of honey bee

The honey bee's life cycle goes through 4 basic stages. They are egg, larva, pupa and
adult stages. As a colony has three classes of bees, queens, drones and workers, each
class of bee develops as an adult over varying durations.

Egg stage

The lifecycle of honey bees begin when the queen bee hatches
eggs. A queen bee lays up to 3,000 eggs in a day. The queen
bee packs eggs closely together within the cells. The eggs
are long elongated and pink coloured. During the first stage
of its development, the egg cell divides rapidly and form the
digestive system, the nervous system and the outer covering. After three days, egg
hatch into larvae.

Each and every egg of the bee doesn’t get fertilized by sperms. Fertilized eggs are
diploid with a pair of 16 chromosomes (16 from male and 16 from female) while
unfertilized eggs are haploid and have only 16 chromosome in them. Fertilized eggs
develop as queen bees and workers bees while unfertilized eggs develop as drone
bees. Future queens develop into a large cell in the egg stage.

Larva stage

During the larva stage, each larva is fed about 1,300 times a
day. They are fed ‘royal jelly’, a highly nutritious food, by
worker bees for 3 days. These workers bees have the specific
task of feeding larvae and tending the brood and often
called ‘brood nurse’. After 3 days, the larvae of worker bees
and drone bees are fed with less nutritious food called ‘bee
bread’ which is made from pollen, honey and the secretion of
brood nurse while the potential queen larva receives royal jelly continuously. Due to
difference in intake of nutrients, bees show difference in the rate of their development.
All the larvae undergo molting. Their body develop rapidly.

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Pupa stage

At the end of the larva stage, the brood cell gets close and the

larva becomes the pupa. In about 5.5 days, the potential queen

bee’s larva spins itself into a cocoon and becomes a pupa while

it takes 6 days for the drone and the worker larva to become a

cocoon inside it. Under the brood, inside the cocoon, the pupa

gets metamorphosed into an adult honey bee.

Adult stage

A queen bee gets metamorphosed from the pupa to the adult
stage in about 7.5 days while it takes 14.5 days for the drone
bee and 12 days for the worker bee. For about 21 days, the
adult worker bees engages itself inside the hive as a brood
nurse by cutting and shaping wax, feeding larvae and the
queen, cleaning and protecting the hive. After that duration,
worker bees get out of the hive for the collection of pollens and
nectar from plants, manufacture honey, provide protection to
the hive from enemies, etc. When a worker bees see a source of
pollen and nectar, it dances and communicates the information with other bees which
are also known as honey bees dance. Drone bees are lazy and do no work.

Honey bee colonies can survive the winter, provided they have enough food resources,
are able to keep sufficiently warm, and are free from diseases and predators. However,
in the winter, colonies are smaller than in the summer because part of the colony
leaves the hive and some worker bees die due to cold. The queen bee lives up to 2
years, the drone bees up to 4 months and the worker bee lives up to 4 to 6 months.

Lifecycle of honeybee

220 | Invertebrates

When the number of bees and queens increase in the hive, a new queen and worker
bees separate from the colony along with drones to form a new colony. Within each
colony, a single queen rules her workers and drones. When an existing queen dies or
becomes incapable of laying eggs, worker honey bees raise a new queen from their
colony. As the new queen becomes a young adult, she attends a nuptial flight. A
nuptial flight is mode of flying of the queen bee for mating with several drones. After
releasing sperms, mating drones die due to the exhaustion of energy released in the
form of sperm. With the sperms stored in its abdomen, the queen bees begins to lay
eggs in the hive.

Different types of honey bees, their age and work division.

Bees Work

Drone bees To fertilize the female

Queen Laying eggs and controlling the colony

Workers of 1-3 days They are very small and weak. They warm the eggs, larva
and pupa

Workers of 4-6 days They feed larva and eat themselves

Workers of 7-11 days They produce royal jelly. They feed royal jelly to larvae and
the queen and also eat themselves.

Workers of 12-17 days They produce wax and use wax to make honey combs. They
close the mouth of the honey comb by using wax.

Workers of 18-20 days They produce poison and protect the whole comb.

Workers of 21 days They become mature and go out of the comb for searching for
nectar, pollen, water, etc.

Importance of honey bee

i. Honey bees help in pollination while moving from flowers to flowers and from
plants to plants. Without pollination from bees some of the plants cannot fertilize
and fruit/food production decreases.

ii. Honey is packed with number of nutrients/substances that are necessary for
human health benefits.

iii. Honey bees are important for apiculture, through which honey is manufactured
in a large scale.

iv. Honey is used in bakeries, confectioneries, food industries, pharmaceutical
industries, etc.

v. Natural waxes which are the secretion of honey bees are used in quality candles,
cosmetics and in polishing goods.

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ACTIVITY

Prepare a table showing the duration of each stage of life cycle of each class of bees of a colony.
Visit an apiculture farm and prepare a report on ‘How honey is extracted in an apiculture farm?’

SUMMARY
 Silkworms are the useful insects which produce silk threads.
 There are two types of silkworms reared in Nepal i.e. Eri and Seri.
 The body of a silkworm is divided into head, thorax and abdomen.
 The silkworm starts producing silk after the 4th moulting of the larval stage.
 The silk is obtained during the pupal stage by keeping them in hot water or even to destroy

the glue.
 Silk is long elastic durable and attractive fibre which is very expensive.
 Sericulture helps to uplift the economic condition of the individual and the nation.
 Each colony contains three adult classes of honey bees: egg-laying queens, sperm-producing

male drones and infertile female workers.
 Queens are fertile bees, drones are male bees while workers are infertile female bees.
 The body of a honey bee is divided into three major parts; head, thorax and abdomen.
 Fertilized eggs develop as queen bees and worker bees while unfertilized egg develop as drone bees.
 Honey bee colonies can survive the winter, provided they have enough food resources, are

able to keep themselves sufficiently warm, and are free from diseases and predators.
 When the number of bees and queens increases in the hive, a new queen and worker bees

are separated from the colony along with the drones to form a new colony.
 Nuptial flight is a mode of flying of the queen bee for mating with several drones.

EXERCISE

1. Classify silkworms. Name the two species of silkworms cultivated in Nepal.
2. In which stage of the lifecycle of the silkworm is silk produced and in which stage

is the silk thread produced?
3. How is the silk thread obtained from the cocoon of the silkworm?
4. Why are the eggs of the silkworm kept in cold places?
5. How many times does the larva of a silkworm moult?
6. Draw a well labeled diagram of the lifecycle of the silkworm.
7. Write the economic importance of the silkworm.
8. What are the features of silk thread? Write any three points.
9. What feature of silk is useful for fishing and surgical thread?
10. Name the different stages of the life cycle of the silkworm.
11. Identify male and female silk moths.

222 | Invertebrates

12. Define.

(a) Brood nurse (b) Bee bread

(c) Nuptial flight (d) Drone bee

13. Give reasons.

(a) Royal jelly is fed continuously to the queen bee for six days. Why?

(b) Why don’t worker bees have reproductive organs in their abdomen?

(c) Why do drone bees die after mating?

14. Differentiate between:

(a) silkworm and honey bee

(b) queen bee and worker bees

15. Answer the following questions.

(a) Describe the anatomy of the bee.

(b) What is the use of the mandible in the bee?

(c) Explain the life cycle of the honey bee.

(d) Prepare a table showing the duration of each stage of the life cycle of each
class of the bee of a colony.

(e) When does the honey bee dance?

A

B GLOSSARY
C

Cocoon : a covering of silk thread that silkworm makes to protect itself in pupal stage
Crysalis : an organism inside puparium



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UNIT

15 Human Nervous and Glandular System

About the Scientist INTRODUCTION

Camillo Golgi Environmental factors such as light, heat, cold, touch,
(1843) taste, smell, sound, water current, force of gravity, etc. act
as stimuli to induce responses and reactions in all living
The golgi bodies inside the cell organisms.
was first described by Camillo
Golgi. Golgi received the Nobel The changes in the environment (or environmental factors) to
Prize in 1906 for his work on the which the organisms respond and react are called stimuli.
structure of the nervous system
which he shared with Santiago Different organisms respond and act to stimuli differently.
Ramony Cajal. Most of the plants do not possess any special structures for
the perception of the external stimuli. They do not have the
nervous system. However, plants respond to the external
stimuli. They do so due to the action of plant hormones.
The plant hormones co–ordinate their behaviour either by
affecting the growth of plants slowly (e.g. plants respond
to light by bending towards it) or by affecting the shape of
plant cells by changing the amount of water in them e.g :
response of ‘touch-me-not’ plant, Mimosa pudica.

The response shown by an organism towards or away from a
stimulus is called reaction.

The working together of various organs of the body of an
organism in a proper manner to produce proper reactions to
a stimulus is called co-ordination.

For proper control and co-ordination, higher animals have
two systems; nervous system and endocrine system.

NERVOUS SYSTEM

The system of tissues, organs and the body which help in the
control and co-ordination of the body is called the nervous system.
The nervous system is composed of specialized cells called
neurons (nerve cells). They exercise by sending electrical
signals called nerve impulses. The nervous control is speedy
and flexible but its effect is localized.

224 | Human Nervous and Glandular System

NERVE CELL/NEURON

The neuron is the structural and functional unit of the nervous system. It has a special
structure and varies greatly in shapes and sizes. Neurons are in-fact, the largest cells
present in the human body.

Neuron (or Multipolar Neuron)

A neuron consists of three main parts as,
(i) Cell body
(ii) Dendrites
(iii) Axon

(i) Cell body (cyton)

A cyton has a nucleus and numerous basophilic Nissl’s granules. These granules are made
of ribonucleic acid and produce new cytoplasm in neurons. They are also concerned
with protein synthesis in nerve cells. The cyton has fine threads of neurofibrils forming
a network. The cell body is also concerned with metabolic maintenance and growth.

MEMORY TIPS
The mass of cyton found in the brain or the spinal cord is called nuclei and the similar mass
found outside the central nervous system is known as ganglion.

(ii) Dendrites

They are generally several short branching processes close to the cell body. They are
afferent because the neuron receives impulses through them. They lie in contact either
with receptors or with the axon of another neuron. Nissl’s granules are also found in
them.

(iii) Axon

The single process which is generally long and has terminal branches is called the axon.
They germinates by small swellings at the ends of the branches. They are different
because impulses are sent out through them. Axons lack Nissl’s granules.

New Creative Science, Class 10 | 225

MEMORY TIPS

 The nerve impulses travel only in one direction in neurons, from the dendrites to the
cell body and then through the axon.

 Neurons do not divide. They are formed shortly after birth. New neurons do not develop
and also they are not repaired when injured.

Differences between Dendrites and Axons.

Dendrites Axons

1. These are short and highly branched. 1. These are long uniform processes.

2. A number of dendrites arise directly 2. A single axon arises from the end of

from the cell body. the cell body.

3. They are afferent. 3. They are efferent.

4. They contain Nissl’s granules. 4. They lack Nissl’s granules.

5. They do not have knobs at the tips of 5. They have knobs at terminal

branches. branches.

Arrangement of neurons

Neurons lie from end to end in chains to transmit nerve impulses in the body. They
are not connected. There occurs a minute gap between the terminal portion of the
axon of one neuron and the dendron of the other. This minute gap is called a synapse.
The synapse acts as a one–way valve to conduct the limpulse in one direction only
with the help of Neuro transmitter. Nerve impulse travels from axon of one neuron to
dendron of another neuron through a synapse.

Impulse transmission across a synapse

Types of neurons

There are three types of neurons:
(I) Sensory (receptor) neurons or unipolar neurons
(II) Motor (effector) neurons or multipolar neurons
(III) Relaying (connector)/mixed neurons or bipolar neurons

226 | Human Nervous and Glandular System

Basic neuron types

(I) Sensory (receptor) neurons: A receptor is a nerve cell or a group of nerve
cells which is sensitive to a specific stimulus or to the specific change in the
environment. They often occur in sense organs and receive stimuli by their
dendrites. They transmit impulse towards the central nervous system (brain
and spinal cord) through their axons. They are also called afferent neurons.

(II) Motor (effector) neurons: A motor neuron is the multipolar nerve cell, which
transmits impulses of commands sent by CNS to the effectors (respective
voluntary muscles or glands or other organs of specific parts) to exhibit necessary
responses to the stimulus. It is also called the efferent neuron.

(III) Relaying (connector)/mixed neurons: These are in the central nervous system
(brain and spinal cord). These serve as links between sensory and motor
neurons for distant transmission of nerve impulses. These neurons receive and
observe the nerve impulses brought by sensory (or, unipolar) neuron, analyse
them, make a quick decision and command the respective voluntary muscles
or glands or other organs through the motor (or, multipolar) neuron to take
suitable reaction.

Stimulus Name of Location of
Receptors Receptors

1. Heat and cold Thermo receptors Skin
Eyes
2. Light Photo receptors Ears
Nose
3. Sound Sono receptors Tongue
Skin
4. Smell Olfacto receptors Ear

5. Taste Gustato receptors

6. Touch, pain, pressure Thigmo receptors

7. Gravity Geo receptors

New Creative Science, Class 10 | 227

ACTIVITY

Put some sugar in your mouth. How does it taste? Block your nose by pressing it between your thumb
and index finger. Now eat some sugar again. Is there any difference in taste? Explain the phenomenon.

QUESTIONS
# What happens at the synapse between two neurons?
# How do we detect the smell of an incense stick?

Parts of the human nervous system

The human nervous system is much more complex and highly developed than that of
other animals. It consists of mainly two parts:

(I) Central nervous system
(II) Peripheral nervous system
The main parts of the human nervous system can be shown in the following chart:

NERVOUS SYSTEM

Central nervous system [CNS] Peripheral nervous system [PNS]

Brain Spinal cord Autonomic nervous Voluntary nervous
system [ANS] system

Sympathetic Para sympathetic
nervous system nervous system

Main parts of human nervous system

(1) Central Nervous System (CNS)

It lies along the main longitudinal axis of the body. It consists of the brain or encephalon
and the spinal cord or the myelon.

(I) Brain or encephalon: The brain reaches its highest development in man with
better integration and has a mastery over the environment. It is situated in the
cranial cavity of the skull. Inside the cranium, the brain is contained in a fluid
filled balloon. It provides the shock absorption and protects the brain from
injury. The fluid which is filled in cranial cavity is known a cerebrospinal fluid.
The brain is made up of nervous tissue which is covered with three membranes
together, called meninges. The outer one is known as duramater, middle is

228 | Human Nervous and Glandular System

arachnoid mater and inner one is the pia mater. The brain consists of three parts.
(a) Cerebrum (Fore brain)
(b) Mid brain
(c) Hind brain

Structure of brain

(a) Cerebrum (Fore brain): It is the largest, most complex and specialized part of
the brain. The two cerebral hemispheres lie side by side, being separated by a
deep longitudinal cerebral fissure. Each cerebral hemisphere is divided by three
deep fissures into four lobes: anterior lobe (frontal lobe), middle lobe (parietal
lobe), posterior lobe (occipital lobe) and lateral lobe (temporal lobe). The main
functions of the cerebrum are given below:
(i) It is the centre of intelligence, memory, imagination and emotions. It is
also the region for speech, facial muscular activities etc. (frontal lobe).
(ii) It is the region of ordinary sensations like auditory reception/hearing
(temporal lobe), visual reception (occipital lobe), touch, taste, smell,
temperature and conscious association (parietal lobe).
(iii) It controls the functions of other parts of the brain.

Functions of cerebrum

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(b) Mid brain: It consists of two fibres and two swellings. This part of the brain is
significantly small. It controls the reflex movements of the head, neck and trunk
in response to visual and auditory stimuli. It changes the pupil size as well as
the shape of the eye lens.

(c) Hind–brain: It consists of three parts – cerebellum, pons varoli and medulla
oblongata.
(i) Cerebellum
It is the second largest part of the brain. It is also known as the small
brain.
Its main functions are:
a. It is sensitive to gravity. It maintains the equilibrium and controls
the posture of the body.
b. It there is small injury in the cerebellum, it causes dizziness. It
disturbs the body balance.
c. It also helps in controlling the eye movement.
(ii) Pons Varoli
It controls the spontaneous respiration. It also controls the cerebellum in
some way.
(iii) Medulla Oblongata
It is the lowermost part of the brain which runs from pons varolii to the
spinal cord.

Its main functions are:
i. It controls the rate of heartbeat, breathing movements, expansion and contraction

of blood vessels to regulate blood pressure.
ii. It also controls swallowing, coughing, sneezing, vomiting, hiccupping, etc.

MEMORY TIPS

 Cerebrum and cerebellum are formed from grey matter and the inner core is formed
from white matter.

 Electroencephalograph is an instrument which records the electrical activity of the
brain in a graph and this record is known as EEG.

(II) Spinal cord or Myelon

It is a long cylindrical structure. It arises from medulla oblongata to the early part of
lumbar region of the vertebral column. It is protected inside the vertebral column or
the backbone. It is also surrounded by meninges and protected by cerebrospinal fluid.
There are 31 pairs of nerves in the spinal cord of a human. The main functions of the
spinal cord are:

i. It conducts sensory and motor impulses to and from the brain.
ii. It acts as the centre of reflex action.

230 | Human Nervous and Glandular System

MEMORY TIPS

The injury in the spinal cord may lead to the paralysis of the body parts below the point of
injury.

QUESTIONS

# Differentiate between the cerebrum and cerebellum.
# Which part of the brain maintains the postures and equilibrium of the body?
# Which signals will get disrupted in case of spinal cord injury?

REFLEX ACTIONS

These are the involuntary actions. They are e e ti
generally done by the spinal cord for quick
response to a specific stimulus.

A reflex action may be defined as a quick,
spontaneous, automatic and mechanical
response to a stimulus.

The blinking of eyes, the movement of the
diaphragm during respiration, withdrawal
of the hand when suddenly pinched or
pricked or while touching a hot object,
coughing, sneezing, yawning, watering
of the mouth on seeing food, etc. are the
examples of the reflex action.

REFLEX ARC

It is a pathway in which the nerve impulse travels along sensory and motor nerves in
the reflex action.

First of all, the receptors receive the stimulus. It is transmitted to the spinal cord
through the sensory neuron. In the spinal cord, impulse is passed on to the mixed
connector or relay neuron which, in turn, passes it to the motor neuron. The neuron
then transmits the instructions to the effector or muscle which shows the response.
Thus, the major components of reflex arc may be explained as,

(i) Sensory (receptor) organ: It receives the stimulus.

(ii) Sensory (afferent) nerve: It transmits the impulse from the receptor organ to the
spinal cord.

New Creative Science, Class 10 | 231

(iii) Mixed neuron: It transmits the instruction of the spinal cord from the afferent to
the efferent neuron.

(iv) Efferent (motor) nerve: It carries messages from the spinal cord to the effector
organs.

The reflex action can be diagrammatically represented as:

External stimulus Receptor Sensory Spinal
organs nerve cord
(Muscles)
Mixed
nerve

Motor nerve

Response Effector
organs

Diagrammatic representation of reflex action

MEMORY TIPS

Reflex actions involve the spinal cord and hence are also termed spinal reflexes. Some
reflexes that involve the brain are termed as cerebral reflexes, e.g. changing the size of the
pupil when bright light is focused on the eye.

ACTIVITY

Stand with a freely hanging leg. Now gently strike the leg below the knee. See what happens? Can
you explain the phenomenon?

QUESTIONS
# What is the difference between a reflex action and walking?
# What is the role of the brain in reflex actions?

THE ENDOCRINE SYSTEM

There are secretary glands found in various parts of the body. They have no ducts
of their own. So their secretions called hormones or internal secretion are carried by
diffusion into blood and lymphatic vessels. These glands are known as endocrine
glands.

232 | Human Nervous and Glandular System

Differences between Endocrine and Exocrine glands

S.N. Endocrine glands S.N. Exocrine glands

1. They are ductless glands. 1. They are the glands with duct.

2. Their secretions are known as 2. Their secretions are known as

hormones. enzymes.

3. They pour hormones directly in to 3. They transfer enzymes directly to

the blood and lymphatic vessels. the organ of action.

4. Their site of their action and 4. Their site of their action and the

the organ of their production of organ of production of enzymes

hormones is at a distance. close by.

Example: Pituitary glands, Example: Salivary glands, tear
adrenal gland etc. glands, liver etc.

MEMORY TIPS
Pancreas and gonads are the intermediates between exocrine and endocrine. So, they are
also known as mixed or heterocrine glands.

HORMONES

They are the chemicals produced from the endocrine glands. They control, co–ordinate,
regulate and integrate the functions of various organs of the body. So, they are also
known as the chemical messenger of the body. They are produced in a small amount,
and small change in the amount of their production leads to the big disorder in the
body. Pituitary glands, thyroid glands, adrenal glands, etc. are some glands present in
the human body. Their location is shown in the figure below:

Position of endocrine glands

The endocrine glands present in the human body are discussed below:

New Creative Science, Class 10 | 233

(a) Pituitary gland

It is a small pea-shaped endocrine gland which lies in a depression of the sphenoid
bone in the skull.

This gland has three lobes; anterior lobe, intermediate lobe and posterior lobe.
The anterior lobe of the pituitary gland produces about ten hormones. They not only
affect other organs but they also influence and control other endocrine glands. So, this
gland is also known as the Master gland of the body. It secrets somatotrophic hormone
or growth hormone. This causes the normal growth of the bones and the body. Over
secretion of the growth hormone leads to gigantism and acromegaly. Its hyposecretion/
less secretion leads to dwarfism. Other hormones are thyroid stimulating hormone
(TSH), antidiuretic hormone (ADH), follicle–stimulating hormone, prolactin, etc.
The intermediate lobe produces intermedin hormone and posterior lobe produces
vasopressin and oxytocin hormone.

(b) Thyroid gland

It lies in the neck and its secretion is known as thyroxin. It
increases the rate of metabolism for the release of energy.
Deficiency of thyroxin in a young child causes a condition
known as cretinism and myxoedema, whereas excessive
production leads to the exopthalmic goitre. Deficiency of
iodine in thyroxin causes a simple goitre.

MEMORY TIPS
Cretinism is characterized by growth retardation, low intelligence, low development of sex
organs, bent legs, protuberence of the tongue and the abdomen.
Myxodema is common in women than in men.

234 | Human Nervous and Glandular System

(c) Parathyroid glands

They are the four minutely yellowish glands attached to the dorsal side (at the back
side) of thyroid. The hormone of parathyroid is called parathormone. It is concerned
with maintaining the amount of calcium and phosphorous in blood, and it is an
important part in bone formation.

Over secretion of parathormone causes calcium and phosphorous to go out of bones
and teeth making them soft and weak. Under secretion lowers the body calcium
retarding growth of the bones and leads to tetany in which a spasmodic contraction of
the limb muscles occurs.

(d) Adrenal gland

The adrenal glands are attached in front of the
kidneys. It has two portions, an outer cortex and an
inner medulla. Secretions of the cortex are essential
for life; they are concerned with carbohydrate
metabolism, balance of salts in the blood, balance
of sodium and fluids in the body, maintenance of
the volume of circulating blood, control of sexual
maturity and giving resistance to many diseases.
The several hormones secreted by the cortex are
collectively called cortin. Aldosterone, cortisol and
sex–corticoids are some examples of cortin.

Similarly, the medulla of the kidney secrets two
hormones i.e. adrenaline and non–adrenaline.

In normal situations, the production of these hormones is also normal or in a small
amount. But when a person faces stress or danger, these are secreted in a large amount
to prepare the body to face emergency situations. So, these hormones are also known
as emergency hormones.

When adrenal glands are removed from the body, the body will not be able to face
the emergency conditions, secondary sexual characters will be poorly developed, the
body will not be able to regulate carbohydrate, protein, fat metabolism, etc.

MEMORY TIPS
Addision’s disease is caused due to the hypo secretion of cortisol. The under secretion of
Aldosterone results in increasing sodium and decreasing potassium concentration in the
blood leading to high blood pressure.

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(e) Pancreas

Pancreas is both an exocrine and an endocrine gland with two distinct kinds of tissues.
The endocrine part has isolated groups of cells called islets of langerhans. It has two
types of cells known as α - cells and β- cells. The β- cells produce the hormone called
insulin and α- cells produce another type of hormone known as glucagon.

Insulin controls carbohydrate metabolism. Deficiency of insulin causes diabetes mellitus
in which body cells become unable to consume appropriate amount of sugar or glucose
and the entire body system lose their efficiency for metabolic processes. Because of
diabetes mellitus, there is on one hand, lack of glucose in the cytoplasm for cellular
respiration and on the other hand, there is an excess of unused sugar in the blood
that is excreted with urine. So that, the sugar level becomes low in the blood due to
frequent urination.

Differences between Diabetes Mellitus and Diabetes insipidus

S.N. Diabetes Mellitus S.N. Diabetes Insipidus

1. It occurs due to the deficiency of 1. It occurs due to the deficiency of

insulin hormone. anti diuretic hormone (ADH).

2. Blood sugar level is high. 2. Blood sugar level is normal.

3. Sugar is excreted in urine. 3. Sugar is not excreted in urine.

(f) Gonads

In males, a pair of testis and in females a pair of ovaries are called gonads.

Male sex organs Female sex organs

In males, the testes are located in scrotum. They secret male sex hormones (i.e.
testosterone) under the stimulation of luteinizing hormone (LH). The testis is made
up of specialized cells called cells of Leydig. The testosterone mainly helps in the
development of male accessory glands and controls the development of secondary
sex characteristics such as the development of moustache, beards, change of voice, etc.

236 | Human Nervous and Glandular System

In females, ovaries are the oval-shaped organs which are located inside the lower
abdominal cavity of a woman on the either sides of the uterus. The ovary produces
three types of hormones i.e. Estrogen, Progesterone and Relaxin.

Estrogen stimulates the formation of ova in the ovary and the development of accessory
sex characters such as enlargement of breasts, broadening of pelvis, growth of pubic
hair and the onset of menstrual cycle.

Progesterone maintains pregnancy by suspending ovulation and stimulates the
thickening of uterine epithelium (in uterus) during the menstrual cycle.

Relaxin is produced at the end of gestation period which helps ease the birth of the
young one.

MEMORY TIPS
Pineal and thymus are other two endocrine glands. Pineal glands are located at the back
of brain secret Melatonin hormone lightens the colour of skin and regulates the working of
gonads. Similarly, thymus secrets thymosin, which regulates growth. This gland gradually
disappars with the increase in age.

ACTIVITY

Make a summary chart of major hormones, their glands, position in the body, functions and the
conditions due to their over secretion and under secretion.

QUESTIONS

# Why are hormones known as chemical messengers?
# Which gland is known as the ‘master gland of the body?’
# Which hormone is called the ‘emergency hormone’? Why?

Stimulation and reaction in Plants and Animals [Not included in new curriculum]

Plants do not respond quickly to the particular stimuli. This is because they do not have
the nervous system (or sensory cells), muscles and sense organs like animals. Yet, they
can respond and react to various environmental stimuli such as light, gravity, water,
touch, chemicals, etc. Plants show two different types of movements in response to
various stimuli. One type of movement is independent of the growth. For example,
the curling of leaves of Mimosa Pudica (touch me not plant). The next movement is
dependent on growth. For example, roots going down and stems coming up. Plants
coordinate their responses against environmental stimuli using the plant hormone.

The plant movements are broadly classified into two types:

(i) Nastic movements (ii) Tropic movements

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(i) Nastic movements

These are non–directional movements. In this case, plants show an immediate response
to stimuli but do not involve the growth of the plants. Nastic movement includes,

(a) Seismonastic movement (thigmonasty), e.g. dropping the leaves of ‘touch-
me not plant’ when they are touched.

(b) Nyctinastic movements: It is of two types i.e. photonastic movements and
thermonastic movement.

Example of photopnastic movement; opening of Dandelion flower in the
morning in bright light and closing in the evening when the light fades.
Example of thermonastic movement, the variations in the position of plant
parts such as leaves and flowers are due to the change in temperature.

(ii) Tropic movements or tropism

Directional movements of specific part of the plant in response to the external stimuli
are called tropism or tropic movements.

Tropic movements are very slow. The movement of the plant part can either be
towards the stimulus or away from the stimulus.

If the movement of the plant part is towards the stimulus, it is termed as positive
tropism and if the movement of the plant part is away from the stimulus, it is termed
as negative tropism.

Types of tropism

There are the following types of tropisms: (c) Chemotropism
(a) Phototropism (b) Geotropism
(d) Hydrotropism (e) Thermo tropism

(a) Phototropism: It is the directional movement of the plant
part in response to the light. For example, the stem or the
shoot of the plant moves towards light and shows positive
phototropism.

Roots of plants move away from light and thus show negative Phototropism
phototropism.

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(b) Geotropism : Here, the external stimulus
is the gravity of the earth. For example,
roots of a plant move downward in the
soil, in the direction of gravity and thus
show positive geotropism.

The stem shows a movement against Geotropism
the direction of gravity and thus shows
negative geotropism.

(c) Chemotropism: It is the directional movement or orientation of the plant part in
response to the chemical stimulus. For example: during the process of fertilization,
the growth of the pollen tube is towards the ovule. Similarly, plants like the
sundew, venus fly trap, etc. move towards the nitrogen compounds. Thus they
show positive chemotropism.

Bending of tendrils away from the chloroform, the contraction of tentacles of
sundew plant in response to the liquid protein, etc. are the examples of negative
chemotropism.

(d) Hydrotropism: The directional movement or the water
orientation of the plant part in response to water is called
hydrotropism. For example, the growth of roots towards
water is the positive hydrotropism.

The stem growing opposite to the water is the example of Hydrotropism
negative hydrotropism.

(e) Thermotropism: The directional movement of the plant part in response to heat is
called thermo tropism. For example, tulip, lotus, etc. open during the sunrise showing
positive thermo tropism and close at sunset showing negative thermo tropism.

TAXIS

The movement of the entire cell of an organisms or its whole body in response to the stimulus
is called taxis.

If the movement of the whole body is towards the stimulus, it is called positive taxis

and if the movement of the whole body is away from the stimuli, it is called negative

taxis. It is of the following types:

(i) Phototaxis (ii) Chemotaxis (iii) Geotaxis

(i) Phototaxis

Here the stimuli is light, e.g. the movement of the chalamydomonas, euglena moths,
bacteria, etc. towards the light is an example of positive phototaxis and the movement
of the earthworm, cockroach, etc. away from light are the examples of negative
phototaxis.

New Creative Science, Class 10 | 239

(ii) Chemotaxis

Here, the movement of the whole body or the entire cell of an organism induced by the
chemicals, e.g. the movement of antherozoids of plants towards the ovary due to the
maleic acid is an example of positive chemotaxis and the movement of mosquitoes,
flies, etc. move away from the insect repellants like mats, Baygon, etc. are the examples
of negative chemotaxis.

(iii) Geotaxis

The movement of the entire cell or the whole body of an organism in response to the
gravity is called geotaxis. For example, the movement of the earthworm towards the
soil is an example of positive geotaxis and the movement of the cnidarian larvae away
from the seabed is an example of negative geotaxis.

MEMORY TIPS
 Auxins, Gibberllins, Cytokinin, Abscisic acid, ethene are the five types of phyto hormones

(plant hormones) which are involved in stimulation and reaction in plants.
 Thigmotropism/Haptotropism is the movement of plant parts, in which the external

stimuli is the touch.

ACTIVITY

Fill a conical flask with water. Cover the neck of the flask with a wire mesh.
1. Keep two or three freshly germinated bean seeds on the wire mesh.
2. Take a cardboard box with one side open.
3. Keep the flask in the box in such a manner that the open side of the box faces light coming

from the window.
4. Observe after two or these days.
5. What can we conclude from this activity?

QUESTIONS
# What are plant hormones?
# How is the movement of leaves of sensitive plant different from the movement of a shoot

towards light?

MODEL QUESTIONS ANSWER

1. What is the difference between a reflex action and walking?

Ü A reflex action is a spontaneous, automatic and mechanical response to the
stimulus acting on a specific receptor without the will of an animal. On the other
hand, walking is a voluntary action that occurs with the animal’s will.

240 | Human Nervous and Glandular System

2. What happens at the synapse between two neurons?
Ü The synapse between two neurons acts as a one–way valve to conduct impulse

in one direction only. The message is passed in the form of nerve impulse from
one neuron to another across the synapse.

3. What is the role of the brain in reflex action?
Ü Reflex actions generally involve the spinal cord for a quick response to a specific

stimulus. However, the information input also goes on to reach the brain where
feeling and thinking process occurs.

4. How is the movement or leaves of ‘touch–me–not plant’ different from the
movement of a shoot towards light?

Ü The movement of a shoot towards light is the tropic movement or tropism. It
involves the growth of the plant. However, the movement of leaves of the ‘touch me
not’ plant is the nastic movement, which does not involve the growth of the plant.

5. Hormones are called the chemical messengers of the body. Why?
Ü They are called the chemical messengers of the body because they are the

chemicals whose site of production and site of action are different and they help
in the control and co–ordination of the body.

6. Adrenaline is called the emergency hormone of the body. Why?
Ü When a person faces stress or fear, adrenaline is secreted in a large amount

to prepare the body to face emergency situations. It increases the rate of the
heartbeat, breathing, blood pressure and sugar level in the blood and activates
all cells of the body to perform their metabolic activities in efficiently so that the
person can tackle the situation. Hence, it is known as the emergency hormone.

7. Name the hormone which requires iodine for functioning. Also, site its
location and name the glands which produce that hormone.

Ü Thyroxine requires iodine for functioning. Thyroid gland produces thyroxine
hormone and this gland lies in the neck region over the larynx (voice-box).

8. Which hormone controls water and electrolyte balance in the body?
Ü Aldosterone controls water and electrolyte balance in the body.

9. What causes gigantism?
Ü Hyper secretion of somatotrophin (growth hormone) causes gigantism.

10. Which part of the brain controls the posture and equilibrium?
Ü Cerebellum controls the posture and equilibrium.

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SUMMARY

 The environmental change which induces the organisms is called a stimulus.
 The nervous system is the network of organs and tissues that control and co–ordinate all the

activities of the body.
 Like the nervous system, the endocrine system is meant for the internal communication and

regulation of the animal body.
 The human nervous system is divided into: (i) Central nervous system (ii) Peripheral nervous

system.
 The neuron is the structural and functional unit of the nervous system. It is divided into axon,

dendrites and cell body.
 There are three types of neurons: (i) sensory (ii) motor (iii) mixed neurons or intermediate.
 The central nervous system comprises Brain and Spinal cord.
 Reflex action is a spontaneous, automatic and mechanical response to the stimulus acting,

without the will of an animal. It involves the spinal cord.
 Exocrine glands are ducted glands and endocrine glands are ductless glands.
 The secretion of endocrine glands is the hormone.
 Hormones are also called the chemical messengers of the body.
 The pituitary gland secrets the growth stimulating hormone, antidiuretic hormone,

vasopression, oxytocin, etc.
 The thyroid gland secrets thyroxine, adrenal gland produces adrenaline and non–adrenaline

hormone.
 The pancreas is called both the endocrine and exocrine gland.
 Testes are the male gonads which secret testosterone, and ovaries are the female gonads

which secret progesteron and oestrogen.
 Hyposecretion and Hypersecretion of hormones lead to various disorders.
 The non–directional movement of the plants which do not involve its growth is the called nastic

movement.
 The directional movement of the plant part in response to external stimuli is called tropism.
 The movement of the entire cell of an organism or its whole body in response to a stimulus is

called taxis.
 The movement towards the stimulus is called positive and the movement opposite to the

stimulus is called negative taxis/tropism.

EXERCISE

1. What do you mean by stimulation and reaction? Explain with examples.

2. What is a neuron? Differentiate between axon and dendrites.

3. Differentiate between afferent nerves and efferent nerves.

4. Write two functions of each.

(a) Cerebrum (b) Cerebellum (c) Medulla oblongata

5. Draw a neuron.

6. What is a spinal cord? Write its function.

7. When a person steps on a thumb pin, he shouts. Explain the process to bring this
stimulation.

242 | Human Nervous and Glandular System

8. What is a spinal cord? Draw a reflex arc and describe it.

9. What do you mean by reflex action? Give some examples.

10. Differentiate between the exocrine and endocrine glandular system.

11. What do you mean by hormones? Why are they called the chemical messengers
of the body?

12. Where are the following glands located in the human body? Also, name the
hormones secreted by each of them.

(a) Pituitary gland (b) Thyroid gland

(c) Pancreatic gland (d) Testes

(e) Ovary (f) Adrenal gland

13. Name the disorder caused due to the hypo and hyper secretion of thyroxine
hormone and growth hormone.

14. Differentiate between the nastic movement and tropic movement in plants.

15. What is taxis? Define positive and negative chemo taxis with examples.

16. When an earthworm is placed in soil, it tries to go under the soil. Why?

17. Write about the following with examples:

(a) Phototropism (b) Phototaxis

(c) Geotropism (d) Chemotaxis

18. Name the stimulus which acts in each of the given reactions.

(a) The shoot of a plant bends towards the sun.

(b) Mosquitoes fly away from a burning mat.

(c) Earthworms move inside soil.

19. Why is pancreas called the heterocrine gland?

20. Study the given figure and answer the following questions.

(a) In which direction does the plant grow?

(b) What do you do to let a plant grow straight?

(c) Why do roots grow towards the soil?

(d) Name the type of tropism shown by the plant.

A

B GLOSSARY
C

Hormone : a chemical substance produced by different endocrine glands
Gestation period : the time that the young ones develop inside their mother’s body
Diurnal : active during the day
Reaction : what you do, say or think as a result of something that has happened

Stimulus : something that produces reaction in human body



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UNIT

16 Blood Circulatory System in Human
Body

About the Scientist INTRODUCTION

William Harvey The human body consists of millions of cells which lie apart
(1578-1657) from each other, e.g. the cells of the head are far away from
the cells of the foot. All of these cells need oxygen, water,
Harvey announced the discovery minerals and other organic substances for their survibal and
of the circulatory system in 1616. proper functioning. The food is digested in the stomach,
He was the first to propose in the small intestine and the other parts of the alimentary
his book ‘An atomic exercise on canal. The nutrients gained from these foods must be
the motion in Animals (1628),’ available to all the cells of the body. Thus, there must be
the first complete theory of the some mechanism for the transportation of nutrients, oxygen
circulation of blood. and other materials from one part of the body to another.
Such coordinated process carrying out proper distribution
and collection of materials from the cells is considered as
transportation or circulation.

Thus, it is the system of the body which works in the transportation,
distribution and regulation of nutrients and oxygen throughout
the body and collects the waste products from there for the process
of excretion called the circulatory system.

In the human body, there are two circulatory systems
through which the materials are transported to the relevant
organs and tissues. They are:

i) Blood vascular system
ii) Lymphatic system

The blood vascular system consists of :
i) Blood
ii) Blood vessels and
iii) Heart

i) Blood

Blood is a red coloured, viscous
fluid connective tissue which
consists of 55% of plasma and 45%
of different types of blood cells. It
has a salty taste and is alkaline in
nature (PH- 7.3 to 7.5). Its specific
gravity is 1.05 to 1.06. An average
human body of an adult consists of 5.5 litres of blood.

244 | Blood Circulatory System in Human Body

ii) Plasma

It comprises about 55% of the blood. It is a transparent yellowish liquid which contains
about 90% of water and 8% of different types of proteins like albumin, globulin and
fibrinogens. The remaining about 2% includes clotting factors, electrolytes, minerals,
carbohydrates, salts, antibodies, hormones, gases and waste products. The blood cells
are suspended in the plasma. The functions of the plasma are as follows:

Functions of plasma

i) It transports digested food to different parts of the body like organs, tissues, cell,
etc.

ii) It transports the various metabolic waste materials of the body like ammonia,
urea, CO2, etc. from the tissues to their respective excretory organs for the
elimination.

iii) It maintains the amount of water (osmoregulation) in the body.
iv) It regulates the body temperature and the amount of various other chemicals in

the body.
v) The hormones secreted by the endocrine glands are transported to the tissues

through the blood.
vi) The protein in plasma (fibrinogen) helps in blood clotting.
vii) It helps in the maintaining of viscosity of the blood.

BLOOD CORPUSCLES/BLOOD CELLS

There are three types of blood cells in the body. They are:
a) RBC (Red Blood Cells/Erythrocytes)
b) WBC (White Blood Corpuscles)/Leucocytes)
c) Platelets (Thrombocytes)

(a) RBC (Red Blood Cells/Erythrocytes)

RBCs are circular biconcave and disc-shaped cells having

no nuclei. In a foetus, there are about 7.8 million of

RBCs per mm3 and in infants there are 6.7 million/mm3

whereas there are 5-5.5 million per cubic mm of the blood

in an adult. They are formed in the bone marrow and

after the completion of the lifespan of about 120 days, Red blood cells
they are destroyed in the liver and spleen. RBC is red in

colour due to the presence of iron pigmented substance known as haemoglobin.

Haemoglobin combines with oxygen to form oxyhaemoglobin. Thus oxygen is

transported to all the parts of the body in the form of oxyhaemoglobin (HbO). Similarly,

it combines with CO2 to form carboxyhaemoglobin. Hence CO2 reaches the lungs for
excretion.

New Creative Science, Class 10 | 245

Function of RBCs

i. They carry oxygen from the lungs to the different parts of the body (like organs,
tissues and cells) and CO2 from the body to the lungs for excretion.

ii. Haemoglobin in the RBC balances the amount of acid and base in the blood.
iii. They maintain viscosity of blood. RBCs help in ion-balance.

Lack of RBCs or haemoglobin in the blood leads to anaemia.

MEMORY TIPS
 The RBCs of camels have nuclei in them.
 One of the causes of jaundice in a newborn baby is due to the excessive destruction of RBCs.
 Anaemia is a long-term disease due to the decrease in the number of RBCs or

haemoglobin. Its symptoms are tiredness, weight loss, pale and dull coloured skin,
retarded growth and loss in appetite.

QUESTIONS
# Why is RBC red in colour? What are the functions of RBC?
# What are the functions of the plasma?

ACTIVITY

Bring a little fresh blood from a butcher’s shop. Shake it vigorously and put it in a glass and observe it after
some time (i) What is the yellowish fluid on the top? (ii) What is the viscous matter which settles down?
Name the blood cells present in it.

(b) White Blood Cells (Leucocytes/WBC)

They are colourless irregular-shaped blood cells having
nuclei. They have nuclei with various shapes and sizes.
There are about 4000-11000 WBCs per cubic mm of the
blood. They are formed in the white bone marrow and
lymph nodes. They get destroyed in the liver, spleen or
the site of infection. They are of two types:

Granulocytes

They are the leucocytes having granules in their cytoplasm
and having lobed nucleus, e.g. neutrophils, eosinophils
and basophils.

Agranulocytes White blood cells

They are the leucocytes without granules and having unilobed nucleus, e.g.
lymphocytes and monocytes.

Functions of WBCs

i. They help in the defense of the body by phagocytosis with the production of
antibodies.

246 | Blood Circulatory System in Human Body