5SiO2 + Na2CO3 + CaCO3 + B2O3 ∆ → Na2SiO3.CaSiO3.B2(SiO3)3 + 2CO2
Borosilicate glass
(Sodium silicate, Calcium silicate and Boron silicate)
Characteristics
a. It is resistant to chemicals and heat.
b. The presence of boron silicate makes it very hard.
Uses
High temperature resistant apparatus are made from borosilicate
glass. The apparatus include test tubes, flasks, beakers, condensers
and kitchen wares.
6. Lead crystal glass
The glass obtained by melting the homogeneous mixture of potassium
silicate and lead silicate is called lead crystal glass. It is obtained by
heating the mixture of silica, potassium carbonate and lead monoxide
at high temperature. It is also known as flint glass.
2SiO2 + K2CO3 + PbO ∆ → K2SiO3.Pb SiO3 + CO2
Potassium silicate and lead silicate
(Lead crystal glass)
Characteristics
a. It has high refractive index.
b. It is hard and insoluble in water, acid, alkali, etc,
Uses
It has high refractive index. So, it is used for making lens, prisms,
electric bulbs, etc.
7. Coloured glass
The glasses of different colours are prepared by adding different
metallic oxides to the mixture of raw materials of the ordinary glass.
Sn Metallic oxide used Colour of the prepared glass
1. Cobalt oxide Blue
2. Nickel oxide Black
3. Chromium oxide Green
4. Manganese oxide Purple
5. Cuprous oxide (Cu2O) Red
6. Selenium oxide Red
7. Ferric oxide [Fe(III) oxide] Yellow or brown
8. Tin oxide Milky white
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Uses
Coloured glass is used for making sunglasses, signals for automobiles,
artificial gems, etc. It is also used for decorative purposes.
Ceramics
A special type of clay containing the compounds of carbon, nitrogen,
silica and oxygen is called ceramics. The word ceramics is derived
from the Greek word 'keramos' which means potter's clay. Ceramics,
itself is the science of pottery and is related to the production of large
number of ceramic products as ceramics industries. Chemically,
ceramics is mainly the hydrated aluminium silicate (Al2O3,
SiO2.2H2O). It may contain other substances such as magnesium
carbonate, limestone powder, iron oxide and manganese oxide. Pure
white soil used in ceramics is called kaolin, which is used to make
cups, plates, etc.
Fact &Reason
What is kaolin?
Pure white soil used for making cups, plates, etc. is called kaolin.
Method of making ceramic pots
a. The clay is separated from gravel and pebbles and is crushed
and ground into very fine powder. It is then sieved.
b. The fine powder is mixed with water and is turned into
shapable paste.
c. It is given a desired shape and is dried in sunlight for some days.
d. The dried pots are then heated at high temperature in special
furnace called kiln. At high temperature, the soil hardens
due to chemical reaction and becomes porous.
e. A small amount of fine salt powder is sprayed on the ceramic
pots in the furnace when it is hot. It makes them non-porous,
smooth, water proof and shiny. This process is called glazing.
f. Colour and polish are also added in order to make the ceramics
attractive.
Characteristics of ceramics
1. They can withstand high temperature.
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2. They are not affected by acid, alkali, and other chemicals.
3. They are hard, attractive and brittle.
4. Ceramics is poor conductor of heat and electricity.
Uses
1. The ceramic cups, bowls, plates, dishes, etc are quite useful.
2. They are used to make vessels that need strong heating.
3. Glazed ceramics is used to make bathroom tiles, sinks, etc.
4. They are used for lining the inner surface of furnaces.
5. They are used to make artificial teeth.
6. Being poor conductor, it is used in electrical appliances.
Polymers and Plastics
A polymer is a very large molecule that is formed by linking a large
number of small molecules together. The starting small molecules
which are used to make polymer are called monomers. For example,
ethylene, vinyl chloride, tetrafluoroethene, etc are monomers.
The process of combination of simple monomeric molecules to form a
giant polymer is called polymerization. Generally, polymerization is
carried out in the presence of catalyst.
The properties of the polymer are quite different from those of the
monomers. For example, polythene is a polymer which is obtained
from the polymerization of ethene gas (CH2 = CH2).
n(CH2 = CH2) polymeriztion → [CH2– CH2]n
ethene
Polythene
(monomer) (Polymer)
Polymers can be categorized into two types: natural polymers and
synthetic polymers.
Natural polymers: The polymers which are available in nature are
called natural polymers. Silk, wool, proteins, starch, cellulose, etc are
examples of natural polymers.
Synthetic polymers: The polymers which are produced under
artificial conditions as per human need are called synthetic polymers.
Plastic, synthetic fibres (terylene, polyester, nylon) etc are examples
of synthetic polymers.
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Plastics
Plastics are synthetic polymers which are prepared by the
polymerization of organic monomers. The raw materials for most
plastics are the chemicals obtained from crude oil. Besides these,
small quantities of other substances are often added to modify their
properties. The plastic goods are widely used due to their following
properties of plastics:
a. It is light, durable and easy to carry.
c. It can be moulded into any desired shape.
b. It is cheap and is available in different shape, size and colour.
e. It is resistant to acids, alkalis and corrosion.
d. It is a bad conductor of heat and electricity.
These characteristics are regarded as the advantages of plastics
over other appliances.
Types of plastics
There are two types of plastics. They are as follows:
1. Thermoplastics
2. Thermosetting plastics
Thermoplastics
The plastics which become, soft on heating and can be moulded again
and again are called thermoplastics. It becomes soft on heating. They
harden again on cooling. So, they can be moulded several times into
different shapes. Polythene is the most common thermoplastic. The
other thermoplastics are polystyrene, polyester, polyvinyl chloride,
etc. The thermoplastic is used for making buckets, bags, pipes, ropes,
etc.
Fact &Reason
Why is PVC called thermoplastic?
PVC softens and melts on heating. So, it is called thermoplastic.
Polythene
It is a polymer of ethylene which can be made by heating ethylene
under high pressure in the presence of a catalyst. It is hard but
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flexible and strong. It is used for making buckets, pipes, laboratory
apparatus, kitchen wares, toys and several other household items.
n(CH2 = CH2) ↑temp,↑press [CH2 - CH2]n
catalyst
ethene Polyethene
Polyvinyl chloride (PVC)
The polymerization of vinyl chloride produces polyvinyl chloride. It
is used for making pipes, raincoats, boots, curtains, hand bags, seats,
furniture, soles of shoes, buckets and insulating cover for electrical
wiring.
n(CH2 = CHCl) polymeriztion → -[CH2 - CHCl]-n
Vinyl chloride Polyvinyl chloride (PVC)
Polystyrene
Polystyrene is a polymer of styrene molecule. It is a hard transparent
and glass-like plastic. It is used for making toys, thermoflask, ceiling
tiles and pipes etc. It is a also used as insulator.
Thermosetting plastics
The plastic that cannot be softened again once a particular shape is
given to it is called thermosetting plastics. Thermosetting plastics are
usually hard and strong. They do not bend easily and are resistant to
heat. So, these plastics cannot be moulded a second time.
Bakelite and melamine are the examples of thermosetting
plastics. Bakelite is manufactured by condensation polymerization of
formaldehyde and phenol. It is used for making radio and TV cabinets,
plugs and other electrical fittings, switches, handles of cookers and
tea kettles etc. Melamine can be coloured easily. It is used to make
cups, plates, bowls, saucers, etc.
Fact &Reason
Why is the handle of pressure cooker made of bakelite?
Bakelite is a thermosetting plastic which does not soften and melt on heating
and it is also a bad conductor of heat. So, the handle of pressure cooker is made
of bakelite.
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Differences between thermoplastics and thermosetting plastics
Thermoplastics Thermosetting plastics
1. It can be reshaped according 1. It cannot be reshaped according
to desire. to desire.
2. It readily softens on heating. 2. It does not soften on heating.
3. These plastics are usually 3. They are usually hard, strong
soft and weak. Examples : and brittle. Examples:
polythene, PVC etc. Bakelite, melamine etc.
Advantages and disadvantages of plastics
As discussed above, plastics are widely used because of their several
properties such as lightness, durability, able to be shaped again and
again, etc.
Besides having advantages, plastics have disadvantages too. They are:
1. They are non-biodegradable. This means that they do not
decay and cause pollution.
2. Many plastics often produce poisonous gases and smoke on
burning and thus cause air pollution.
3. Some plastics catch fire very easily and cause fire of house,
factory, etc.
Fibres
A fibre is a long hair like polymeric strand which is strong and
flexible. Fibres are of two types: natural and Artificial fibres.
Natural fibres
Cotton, silk, wool, linen, etc are natural fibres. Cotton is obtained
from cotton plant, silk from cocoon of silkworm, wool generally from
sheep and rabbit, and linens from stalk of flax plant. Similarly, simal,
hemp, coconut plant, etc also give fibres.
Cotton fibres are used to make clothes. Silk is also used for making
clothes. Wool is used for making blankets, clothes, etc. Similarly,
linen is also used for making clothes. Jute, hemp and coconut are
coarse plant fibres which are used to make ropes, sacs, bags, etc.
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Advantages of natural fibres
1. The cotton clothes absorb sweat. They allow air to circulate and
help to keep our body cool. So, these clothes are comfortable
to wear in summer.
2. The woolen clothes are comfortable to wear in winter. They
do not allow body heat to escape and keep us warm.
Disadvantages of natural fibres
1. They are expensive but not durable.
2. Cotton clothes need ironing after every wash.
3. Woolen clothes are easily destroyed by insects.
4. The fabrics made from natural fibres may shrink on washing.
5. They do not get dried fast after washing.
Artificial fibres
Man made fibres are called artificial fibres. They are of two types:
Synthetic fibres and recycled fibres.
Synthetic fibres
The fibres which are produced artificially by chemical reactions are
called synthetic fibres. Some of the common synthetic fibres are
nylon, terylene, rayon, orlon, cashmilon, acrylic fibres, fortel, coddle,
cresian, etc. The advantageous properties of synthetic fibres are as
follows:
1. They are fine, light and durable.
2. They dry up easily after washing.
3. They are strong and flexible.
4. They are not attacked by insects and fungi.
Uses
1. Rayon is used in the manufacture of fabrics like sarees.
2. It is also used to manufacture bandage and lint (for dressing
wound).
Nylon
It is the first prepared synthetic fiber. Nylon is a polymer formed
by the polymerization of adipic acid and hexamethylene diamine.
Hence, nylon fibres are also known as polyamides.
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Nylon is a light and strong elastic fibre. It absorbs very little water,
so it dries up rapidly after washing. It does not shrink and is not
attacked by insects.
Uses
1. It is used for making tyre cords, ropes, parachutes, bristles of
paint brushes, etc.
2. It is used for making sarees, shirts, shocks, etc.
3. It is also used for making carpets, fishing nets etc.
Terylene (polyester)
It is a strong, flexible, durable and wrinkle resistant fibre. It is also
resistant to the action of chemicals. It dries up quickly because it
absorbs less water while washing. It is not damaged by insects.
Uses
1. It is used for making textiles, suits etc.
2. It is also used for making sails for boats.
Recycled fibres
The fibres which are prepared by recycling the natural fibres are
called recycled fibers. Rayon is example of recycled fibres.
Rayon
It is a synthetic fibre but resembles silk in appearance and hence
it is also called artificial silk. Rayon is manufactured from cellulose.
Disadvantages of artificial fibres
1. The clothes made of artificial fibre catch fire easily.
2. They absorb less sweat.
3. They produce bad smell on burning and pollute the air.
4. They are non-biodegradable and pollute the environment.
Soaps and detergents
Soap is a cleaning agent. It is produced by the hydrolysis of oils
and fats. The oils and fats are the triesters of glycerol with long
chain fatty acids. The main fatty acids present in fats and oils are
palmitic acid (C15H31COOH), stearic acid (C17H35COOH), oleic acid
(C17H33COOH), etc.
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Soap is the sodium salt of long chain fatty acid which has cleansing
property in water. The soap is produced when an oil or fat is heated
with strong alkali solution.
CH2 OOCR + Na OH CH2 OH
|
|
CH OOCR + Na OH → CH OH + 3RCOONa
| | Soap
CH2 OOCR + Na OH CH2 OH
Fat or Oil Sodium hydroxide Glycerol
Where, R represents the alkyl radical such as C17H35, C15H31etc.
The process of making soap by hydrolysis of fats or oils with strong
alkali solution is called saponification.
During saponification, sodium chloride is added in the solution to
precipitate. After precipitation, soap floats on the surface of water
due to its less density. It is then collected and kept into moulds to get
the soap cakes. Sodium carbonate or starch is added to make the soap
hard. Additional materials such as perfumes, colours, antiseptics and
bleaching materials are also added in the soap according to the need.
Detergents
The sodium salts of long chain benzene sulphonic acid or long chain
alkyl benzene sulphonates are called detergents. The detergents are
cheap with more cleansing property. Some common examples of
detergents are sodium lauryl sulphate, alkyl benzene sulphonate,
sodium pyrophosphate, etc. The detergents are better than soaps due
to the following reasons:
1. Synthetic detergents have a stronger cleansing action than
that of soap.
2. They are cheaper because they are prepared from the
hydrocarbons produced as byproducts of petroleum.
3. They work well even with hard water but soaps are insoluble in it.
Detergent is also known as soapless soap because it has cleansing
property like that of soap but it does not contain actual soap.
Detergent powder contains synthetic detergents (15-30%), sodium
carbonate, sodium silicate, sodium sulphate and little amount of
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bleaching agents. Perfume is also added to make washing powder
more attractive and popular. The main disadvantage of detergents is
that they are non-biodegradable and hence pollute the environment.
Differences between soaps and detergents
Soaps Detergents
1. Soaps are sodium salts of 1. Detergents are the sodium salts
long chain fatty acids. of long chain benzene sulphonic
acid.
2. They are prepared from 2. They are prepared from
oil or fat of animals or hydrocarbons obtained as the by-
plants. products of petroleum.
3. They have relatively 3. They have relatively strong
weak cleansing action. cleansing action.
4. They are mostly 5. They are mostly non-biodegradable.
biodegradable.
Pesticides
The pesticides are the poisonous substances which are used to
kill pests. The pests destroy the crops and decrease the yield.
Pesticides are of different types: insecticides, herbicides, fungicides,
rodenticides, etc that are used to kill insects, weeds, fungi and
rodents respectively.
Insecticides
The poisonous substances which are used to kill harmful insects are
called insecticides. The insects harm the crops, domestic animals
and human being. So, they are killed by using insecticides. The
insecticides can be categorized into two types:
1. Organic insecticides 2. Inorganic insecticides
1. Organic insecticides
Organic insecticides are the synthetic compounds which are
composed of carbon, hydrogen, oxygen and other elements. There
are three types of organic insecticides. They are:
a. Chlorinated organic insecticides: These compounds
contain chlorine as an additional element. These compounds
are stable and have long term effects. For example, aldrin,
dieldrin, dichlorodiphenyl trichloroethane (DDT) and benzene
hexachloride (BHC).
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b. Organophosphate insecticides: The organic insecticides
that contain phosphorus as an additional element are called
organosphosphate insecticides. These insecticides are less stable,
degradable and highly toxic to other animals. For example,
malathion, parathion, phosdrine, etc.
c. Carbamate insecticides: The insecticides which have amino
group (–NH2) in their molecular formula, are called carbamate
insecticides. For example, baygon and termic.
2. Inorganic insecticides
They are made from minerals and do not contain organic groups.
For example, calcium arsenate, lead arsenate, fluorides and lime
sulphur. These inscecticides are used to protect cotton, fruit,
vegetables, etc from insects.
Characteristics of good insecticides
1. They should be biodegradable.
2. They should not be harmful to human beings, birds and
higher animals.
3. They should not pollute air, water or soil.
4. They should not leave long term effects.
Advantages of insecticides
1. They kill or control harmful insects or pests.
2. They help to increase food production.
3. They help to control several diseases by killing germs.
Disadvantages of insecticides
1. Insecticides kill not only harmful insects but also some useful
insects.
2. They are mostly synthetic and non-biodegradable.
3. DDT is a stable and non-biodegradable insecticide with long
term effects. Hence, it harms human beings, animals, birds
and plants. DDT causes air, water and soil pollution. If it enters
human body through contaminated food, it badly affects liver,
kidney and other organs. It also affects the bird's eggs.
4. They can leave harmful deposits in fruits and crops while
using in them.
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Precautions while using insecticides
1. We should be very careful while applying insecticides because
they can take our lives as well.
2. They should be kept away from the reach of children.
3. They should not be stored along with or near the foodstuffs.
4. We should wash our hands well with soap and water after
using insecticides.
5. Excessive use of insecticides should be avoided.
Fertilizers
Fertilizers are the substances which are added to the soil to increase
the crop production by supplying essential nutrients. There are two
types of fertilizers: a. Organic fertilizers (manures) b. Inorganic or
Chemical fertilizers
a. Organic fertilizers
The fertilizers which are obtained from the decomposition of the
animal wastes and the dead plants are called organic fertilizers.
It is also called manure. Green manure and compost manure are
the examples of manure.
i) Green manure
Green manures are made from plants which are highly nutritive.
Green plants are grown in the field and ploughed back into the
soil. They get decayed in the soil and supply essential nutrients
to the soil.
ii) Compost manure
Compost manure is prepared by keeping dead plants and animal
wastes buried in a pit with thin layers of soil. The organic
matter is decomposed by microorganisms and compost manure
is obtained.
Advantages
a. They are biodegradable and hence do not cause pollution.
b. They are useful for all varieties of plants.
c. They are cheap as they are produced from wastes.
d. They do not impart side effects on human beings as done by
chemical fertilizer.
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e. It helps to conserve water in the soil.
f. It helps for the growth of soil organisms such as earthworms.
Disadvantages
Organic fertilizers are poor in inorganic nutrients like nitrogen,
phosphorus and potassium.
Fact &Reason
NPK fertilizer is a complete fertilizer, why?
NPK fertilizer contains all three basic elements necessary for plants i.e., nitrogen,
phosphorus and potassium. So, NPK fertilizer is a complete fertilizer.
b. Inorganic or Chemical fertilizers
The water soluble chemical compounds which are added to the soil
to increase crop production by supplying essential elements are
called chemical fertilizers. The chemical fertilizers supply nitrogen,
phosphorus, potassium, etc to the soil. The examples of chemical
fertilizers are ammonium sulphate , ammonium phosphate, urea,
potassium nitrate, etc. These chemical fertilizers may contain the
chief elements required for the plants. The chief elements required
for the plants are nitrogen, potassium and phosphorus.
Differences between organic fertilizers and chemical fertilizers
Organic Fertilizer Chemical Fertilizer
1. They are man-made chemicals
1. They are obtained by
the decomposition of which contain specific
dead plants and animal elements.
wastes.
2. They are soluble in water and
2. They are not readily hence are quickly absorbed by
soluble in water and plants.
are absorbed slowly by
plants. 3. They are nutrient specific. For
example; nitrogen containing
3. They are not nutrient fertilizers provide only
specific. They provide nitrogen.
several nutrients.
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4. They do not pollute the 4. They pollute the environment.
environment.
5. They are rich in nitrogen,
5. They are rich in organic phosphorus and potassium
nutrients but poor in (NPK). They do not provide
nitrogen, phosphorous organic nutrients.
and potassium (NPK).
Chemical pollution
The pollution of the environment due to the release of unwanted
and harmful chemicals is called chemical pollution. The chemical
pollution is heavy in industrial and densely populated areas. The
chemical pollution is harmful to human as well as other lives.
Causes of chemical pollution
The use of pesticides, chemical fertilizers, plastics, detergents, etc is
the main cause of chemical pollution. In addition to these, industrial
wastes and byproducts, water from the science labs and hospitals are
also the major causes of chemical pollution.
The major causes of chemical pollution are as follows:
1. Chemical fertilizers: The chemical fertilizers contain useful
as well as harmful substances. The harmful elements present
in chemical fertilizers are accumulated in fruits, vegetables and
grains. These elements harm human health if such foods are
eaten.
The chemical fertilizer washed away by run off water from the
field is mixed into the rivers, ponds, lakes, etc. Algae and other
aquatic weeds grow rapidly in such water and take up more
oxygen dissolved in water. Thus, the aquatic animals begin to
die due to the lack of oxygen.
2. Insecticides: The insecticides such as DDT, malathion, aldrin,
dialdrin etc cause chemical pollution. DDT is accmulated in the
body of animals and causes long term effects. If other carnivorous
animals eat the animal died from the effect of DDT, they are also
affected.
3. Detergents: Detergents and other synthetic cleansers are non-
biodegradable. They are harmful to human health if swallowed
or come in contact of them.
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4. Colouring matter in foodstuff: The colouring matter used in
tea, coffee, chocolate, sweet dishes, etc are harmful to human
health. These chemicals can make us prone to dangerous diseases
like cancer. These chemicals also affect the vital organs such as
kidney, liver, etc.
5. Plastics: Plastics are non-biodegradable. So, they pollute the
environment. The burning of plastics produces poisonons gases
and causes air pollution.
6. Harmful gases from vehicles and factories: The harmful
gases such as CO2, SO2, NO, NO2, CO, etc are emitted from
factories and vehicles. These gases cause air pollution and
adversely affect the human health.
7. Domestic wastes: The wastes produced from home is one of
the major causes of pollution in urban areas. When the toxic
substances present in the wastes spread in air and water, they
enter human body and cause serious harms.
Control measures of pollution
Various human activities are responsible for causing pollution
hence, it is not easy to make our environment pollution-free. Public
awareness, feeling of responsibility and organized efforts are
necessary to control pollution.
Some of the control measures of pollution are as follows:
a. The gases emitted from factories and vehicles should be
converted in to harmless form before they are released to the
environment.
b. The use of plastic bags should be discouraged. Plastic
materials should be recycled instead of throwing them as
waste.
c. The overuse of pesticides and chemical fertilizers should be
controlled.
d. Household waste should be managed properly.
e. People should be made conscious about the use of harmful
colours in foodstuffs.
It is necessary to keep balance in nature. Hence, every individual
should be conscious and responsible for the preventive measures of
pollution. Control of pollution, and conservation of nature help to
keep balance in nature.
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Solid waste management
The unwanted and useless materials generated in solid from human
activities are solid wastes. Household garbage, food waste, farmyard
waste, construction wastes, demolition debris, industrial wastes,
unwanted items like damaged furniture, machinery, scarp metals
etc. are some solid wastes. Production of solid waste is increasing
due to urbanization and increase in population.
Management of solid waste in proper way is becoming a big
challenge in urban areas. If solid waste is not managed in proper
way, it may create many problems. It may bring many diseases; it
causes air pollution; it causes growth and development of various
types of disease germs and insects. Therefore, management of solid
waste is very important. Following are some of the activities we need
to do for solid waste management:
1. Reduction in the generation of solid waste
Reduction in the generation of solid waste is one of the
best action for management of solid waste. We have to use
materials of good quality, so that they can last for long time.
We should develop habit of purchasing goods when they are
absolutely required.
2. Reuse of solid waste materials
Using the waste materials again for another purpose is reuse
of materials. We can reuse cans of chocolates and bottle of
drinks for keeping pulses and other materials in kitchen.
Similarly, we can reuse old clothes for making pillow and
quilt. Some of the waste materials like plastic, metals can be
recycled to make new products.
3. Collection and transportation
Solid wastes produced from various sources like industries
and household should be collected and transported timely and
effectively. For developing proper collection and transportation
system, government should take proper step. The collected
waste should be transported to a place far away from human
settlement.
4. Land filling
After collection and transportation of solid waste, disposal of
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solid waste by burying it at land fill site is done. This process
is called landfilling. Landfill sites are generally selected far
away from the human settlement.
5. Generation of energy
Organic waste matter can be used to produce bio gas. Cattle
dung and other organic matters are decayed to produce bio
gas.
6. Production of fertilizer
Solid waste rich in organic matter can be used to produce
compost manure. They are decomposed by bacteria and fungi.
Organic solid waste can be used for vermicomposting too.
7. Incineration
Incineration is the process of burning solid waste in a special
type of furnace. The hot gas produced during incineration can
be used to run turbine from which electricity can be produced.
Learn and Write
1. Hard glass is also called potash lime glass. Why?
Hard glass is prepared by heating mixture of silica, potassium
carbonate and calcium carbonate at high temperature. Thus,
hard glass contains potassium silicate and calcium silicate.
Therefore, hard glass is called potash lime glass.
2. Sodium chloride powder is sprayed on the ceramics pots when it
is hot. Why?
When sodium chloride powder is sprayed in the ceramic pots
when it is hot, it makes them smooth non-porous and water
proof.
3. Environmentalists advise not to use detergents. Why?
Detergents are non-biodegradable. Thus, they do not decay
for a long time and cause environmental pollution. Therefore,
environmentalists advise not to use detergents.
4. Use of insecticides is both beneficial and harmful. Why?
Insecticide kills the harmful insects which destroy crops. Thus,
it helps to increase crop production. It does not kill harmful
insects only but also useful insects. Therefore, it is harmful too.
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Main points to remember
1. Cement is a mixture of calcium silicate and calcium aluminate
in the form of fine grey powder.
2. Glass is an amorphous, hard, transparent and homogeneous
mixture of silicates of different metals. It may contain third
substance as colouring matter.
3. A special type of clay which contains the compounds of carbon,
nitrogen, silica and oxygen is called ceramics.
4. A polymer is an extremely large molecule that is formed by the
chemical combination of a large number of small molecules together.
5. The process by which two or more simple molecules are joined
together to form a giant molecule is called polymerization.
6. There are two types of fibres natural fibres and artificial fibres.
7. Soap is the sodium salt of long chain fatty acid which has
cleansing property in water.
8. The process of making soap by the hydrolysis of fats or oils with
strong alkali solution is called saponification.
9. Detergents are the sodium salts of long chain benzene sulphonic
acid or long chain alkyl benzene sulphonates.
10. Fertilizers are the substances which are added to the soil to
increase the crop production by supplying essential nutrients.
Exercise
A. Very short answer questions (1 mark )
1. Write down the raw materials of the following substances:
i. Cement ii. Glass iii. Borosilicate glass
iv. Ordinary glass v. Soap vi. Hard glass
2. Write a special property of water glass.
3. Name the chemical which increases the setting time of
cement.
4. What is kaolin? Why is it used ?
5. What is glazing?
6. What are plastics?
7. Which industrial substances are formed from the following
chemicals?
i. Silica and sodium carbonate are heated together.
ii. Fat and caustic soda are heated together.
8. What is detergent ? Give one example.
9. What is compost manure? How is it prepared ?
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10. What are nitrogenous fertilizers?
11. What is water glass?
12. What is quartz glass ?
13. What is cement?
14. What is hard glass ?
15. What is lead crystal glass?
16. Which chemical is used to prepare red glass?
17. Name a chemical used to make blue glass.
18. Which compound is added to make the black glass?
19. What is concrete?
20. List out two materials used for making water glass.
21. Which glass is fireproof?
22. Write the name of two raw materials used for the
preparation of pyrex glass.
23. Which chemical is heated with the mixture to increase the
refractive index of ordinary glass.
24. Which type of fibre are rayon and silk?
25. What is chemical pollution ?
26. What is soap? Give one example.
27. What is saponification?
28. Write down the full form of DDT.
29. Write the name of a carbamate insecticide.
30. What are fertilizers ?
31. Name two types of fertilizers.
B. Short answer questions (2 marks)
1. Write two reasons that compost fertilizer is better than
chemical fertilizer.
2. Detergents are called soapless soap. Why?
3. "Synthetic detergents are better than soaps". Justify this
statement with any two reasons.
4. Why are plastic materials used more than other materials?
5. Why is gypsum added to cement ? Give reason.
6. Why are ceramic materials brought into use? Give any four
reasons.
7. Electric switch and handle of pressure cooker are made up of
bakelite, why?
8. What is meant by NPK fertilizer? Why is it called a complete
fertilizer?
9. Water used to wash clothes with detergent is not useful for
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the plants, why?
10. Why is PVC called a thermoplastic? How does it differ from
bakelite?
11. Mention any two reasons of chemical pollution.
12. Environmentalists request to avoid the use of plastic. Why?
13. Mention the major causes of chemical pollution.
14. Differentiate between compost manure and chemical
fertilizers.
15. Organic fertilizer is better than chemical fertilizer. Give any
two reasons.
16. Why are the following chemicals added while making these
materials?
i. Gypsum in cement.
ii. Calcium carbonate in ordinary glass.
iii. Lead monoxide in ordinary glass.
iv. Nickel oxide in ordinary glass.
v. Salt in heated ceramics.
vi. Sodium chloride in the solution during saponification.
C. Long answer questions (3 marks)
1. How is compost fertilizer made? Explain.
2. Why is glass called fourth state of matter? Write any two
uses of water glass and lead crystal glass.
3. How is ordinary glass made? Write any one use of ordinary
glass.
4. How can you prepare soap? Write the word formula
equation.
5. Write down the main uses of ceramics.
6. Write down differences between.
i) Thermoplastic and thermosetting plastic.
ii) Ordinary glass and hard glass.
iii) Soap and detergent.
iv) Organic fertilizer and inorganic fertilizers.
v) Natural polymer and artificial polymer.
D. Very long answer questions (4 marks)
1. How can we colour the glasses ? Describe.
2. How is cement manufactured ? Describe.
3. What are the major causes of chemical pollution? Explain
control measures of chemical pollution.
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4. What is solid waste management? What are various
activities which we need to carry out for solid waste
management? Explain.
Project Work
Study the materials used in your home. Find out how they are
produced and what their constituents are. Also write down the
uses (advantages) and disadvantages of these materials.
Glossary
• Kiln : a specialized oven or furnace used
for industrial processes such as firing
clay for pottery or bricks
• Homogeneous : having uniform composition
• Silica : silicon dioxide found naturally in various
crystalline and amorphous forms, e.g. quartz,
opal, sand, flint, etc
• Ceramics : objects that are made from clay and are made
hard with heat
• Synthetic : man-made
• Accumulated : collected
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Chapter
14 Invertebrates
Thomas Hunt Morgan
Thomas Hunt Morgan was an American evolutionary
biologist, geneticist, embryologist, and science author.
Estimated Periods: 6 (4T+2P)
Objectives
At the end of the lesson, students will be able to:
• describe the introduction, structure and life cycle of silkworm. Also explain the
properties and uses of silk.
• describe the introduction, structure and life cycle of honeybee.
The animals which do not have backbone are called invertebrates.
The invertebrates are categorized into nine phyla – protozoa, porifera,
coelenterate, platyhelminthes, aschelminthes, annelida, arthropoda,
mollusca and echinodermata. Among them, arthropoda is the largest
group of invertebrates. The phylum arthropoda is divided into four
classes – crustacea, myriapoda, arachnida and insecta. Silkmoth and
honeybee are some useful insects. In this chapter, we study the life
cycle of silkworm and honeybee.
Silkworm
Silkworms are useful insects. They produce silk fibre which is one of
the expensive and good quality fibres. From business point of view,
generally two types of silkworms are reared. They are eri-silkworm
(Attacus ricini) and seri silkworm (Bombyx mori). Eri silkworms feed
on castor leaves and seri silkworms feed on mulberry leaves. The
rearing of silkworms for the commercial production of silk fibre is
called sericulture. Commercial sericulture was started from China
around 2700 BC but it was kept secret to other countries for long time.
In Nepal, the sericulture was introduced in Khopasi, Kavre.
Systematic Position fore wing head antenna
thorax
Kingdom - Animalia
Sub Kingdom - Invertebrata
Phylum - Arthropoda hind wing abdomen
Class - Insecta
Type - Silkworm Silkmoth
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Structure
Silkworm is a medium-sized insect shaped like a butterfly. It is white
creamy in colour. Its length is about 2-3 cm. Its body is divided into
three parts. They are: head, thorax and abdomen.
The head bears a pair of compound eyes, a pair of feathery antennae
and sucking types of mouth parts. The thorax bears three pairs of legs,
two pairs of wings and two pairs of spiracles. The abdomen consists of
ten segments which are hairy. The body of female silkworms is wider
than those of males to accommodate eggs.
Life cycle of silkworm
Silkworm passes through four stages in its life cycle. They are egg,
larva, pupa and adult. Male and female copulate in air. The male dies
after copulation whereas female dies after laying eggs.
Adult Eggs
Life Cycle of Larvae
Silkworm
Pupa
Eggs
Female lays about 300-400 eggs in cluster
on leaves of mulberry plants. The eggs are
covered by gelatinous secretions by which they
are stuck to the leaves.
The eggs are round, small and yellowish-white Eggs
in colour. The eggs can be stored in a cool place
when the mulberry leaves are not available. When the temperature
increases upto 18° to 25°C, they hatch into larvae within 12 days.
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Fact &Reason
Why does seri silkworm lay eggs on mulberry leaves?
The larvae of the seri silkworm feeds on mulberry leaves, due to which seri
silkworm lays eggs on mulberry leaves.
Larvae
The larvae of silkworm are creamy white
in colour. Their body contains three parts,
i.e. head, thorax and abdomen. The head
contains biting and chewing mouth parts.
They eat a lot in this stage even for pupae
stage. Therefore, they are called voracious
eater. Thorax contains three pairs of true Larvae
legs. The abdomen contains five pairs of
pseudolegs and a dorsal anal horn on the eighth segment. The larva
changes its skin four times. This process is called moulting. The newly
hatched larva is called first instar. It feeds for three days then sleeps
for 20 to 24 hours. After this, it moults into second instar. In the same
ways second instar moults into third instar on the 12th day. The third
instar moults into fourth instar on the 18th day. The 4th instar moults
into 5th instar on the 26th day.
The fifth instar eats much and grows fully. Fully grown instar develops
a pair of silk glands which produce silk fluid. When the silk fluid comes
in contact with air, it changes into fibres. The fibres wrap around the
body of the larva to form the pupal case or cocoon. The cocoon is white
or yellow. Larva of silkworm is also called caterpillar.
Pupa
Pupa is the inactive stage in the life cycle of
silkworm. Pupa remains inside the cocoon.
It stops feeding but internal development
process continues inside the cocoon. This Pupae
process is called histogenesis. The pupal
stage lasts for about 12-14 days. The pupa changes to adult stage after
complete metamorphosis. Pupa comes out from the cocoon by cutting
the silk fibres. Therefore, the pupae are killed by keeping the cocoon in
hot water or oven for obtaining silk fibres. About 1000 metre long silk
fibre is obtained from a single cocoon.
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Fact &Reason
The cocoon is added to hot water, why?
The cocoon is added to hot water to kill the pupa so that single unbroken silk fiber
can be obtained.
Adult
After active metamorphosis, the pupa changes
into adult or imago. It comes out from the
cocoon by cutting the silk fibres. It then dries
its wings and flies. After 3 to four days, it
becomes fully matured. Then male and female
insects mate. Male dies after mating and Adult
female dies after laying eggs. Thus, adult survives for 5 to 6 days after
they emerge from the cocoon.
In this way, life cycle of silkworm completes within 45 days under
favourable conditions.
Fact &Reason
Why are eggs of silk moth preserved in the cold place during winter?
The larva of the silk moth feed on mulberry leaves. But mulberry leaves are not
available in winter. Due to this reason, eggs of silk moth are preserved in the cold
place to prevent from getting hatched.
Economic importance of silkworms
Silkworms are very useful insects. They produce silk fibres in larva
stage. The silk cocoons are kept in hot water or hot air to kill the
pupae. If they are not killed, they cut the silk fibres into pieces to
emerge out. Silk fibres can be used for making clothes. The importance
of silkworm is as follows:
1. Silk produced from silkworm is used for making clothes like saris,
shirts, vests, ties, nets, etc. The clothes are durable and
attractive.
2. Silk fibres are used with other fibres to make new types of clothes.
3. Intestines of silkworms are extracted to make strings (gut). This gut
is used in surgical or fishing purpose.
4. Sericulture improves economic condition of the individual
and nation.
Features of silk thread
1. Silk is a shining, light and durable fibre.
2. It is longer and more elastic.
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3. It can be coloured easily.
4. The silk clothes are suitable for all seasons.
5. It does not decay easily. So, it is used in surgical stitching.
6. It absorbs water readily.
Honeybee
A honeybee is a useful insect. It has three pairs of jointed legs and a
pair of wings. Its external structure is given below:
Forewing
Head Thorax Abdomen
Compound Eye Spiracle
Antennae Sting
Hind Leg
Upper Lip
Jaw BeMeiddle Leg
Lower Lip
Foreleg
Queen bee
The queen is the long, well grown and the largest
bee in the hive. However, its head is round and
smaller than that of others. Its mouth part
(proboscis) is also shorter. There is a stinger at
the last segment of its abdomen. A hive of bees
contains a single queen bee. They are diploid.
So, they have 32 chromosomes. The main job of
the queen bee is to lay eggs. But it can control
and direct the other bees of the hive in different Queen bee
situations. It produces a unique smell from its
body which is received by all other bees of the hive. The other bees
recognize and return to their own hive due to this smell.
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Drone bee Drone bee
The drones are the male bees. They are smaller
than the queen bee but are bigger than the
worker bees. They are haploid. So, they have 16
chromosomes. They have a dark, rough and hairy
body. They do not have sacs in legs for collecting
pollens and nectar. They also lack honey making
and poison glands. They have to be fed by the
worker bees. The single job of the drones is to
fertilize the queen for laying eggs.
Worker bee Worker bee
These bees are females but they are not sexually
developed. They are also diploid in nature and
have 32 chromosomes. The worker bees are the
smallest among other bees in the hive. They bear
three pairs of hairy legs. These legs consist of
pollen basket for collecting pollens and nectar
from the flowers. They have chewing and lapping
type of mouth parts which help to collect pollen
and nectar from flowers. Worker honey bees are
able to live for six weeks. Workers are the only
bees that most people ever see.
Workers search for food (pollen and nectar from flowers), build the
hive, take care of larvae, circulate air by beating their wings and fight
with enemies to protect the hive.
Life cycle of honeybee
There are four stages in the life cycle of a honeybee. They are eggs,
larva, pupa and adult. These stages are of different durations according
to the breed or type of the honeybee.
If the number of bees in a hive becomes much more, the old queen
bee builds up a new group of bees within the hive. In such case, a
new queen gets birth. The mature queen bee and drone bees get out
from the hive for mating flight or nuptial flight. There is the mating of
queen bee with a number of drone bees during nuptial flight.
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Adult Eggs Larvae
Life Cycle of
Honeybee
Egg Pupa
Life cycle of honeybee
The queen bee performs the nuptial (mating) flight after Egg
3 to 5 days of its maturity. It starts to lay eggs after 2
to 3 days of mating flight. The queen bee can lay upto
3,000 eggs in day during favourable weather. However,
the number of eggs differs according to the species of
honeybee. The egg of honeybee is white and elongated in
shape. The egg remains erect in the egg cell on the first
day, it gets slanted on the second day and lies down on
the third day.
The queen bee lays eggs in different cells to give birth to workers,
drones and new queen. It lays eggs in male cells for drone bees, in
worker cells for worker bees and in queen cell for the new queen bee.
The egg stage lasts for three days in all species of bees.
Some of the eggs of honeybee are not fertilized. The unfertilized eggs
are haploid with 16 chromosomes. The fertilized eggs are diploid with
32 chromosomes.
Larva
The egg hatches into larva after 3 days of laying eggs.
The larva of queen and drone bee is larger than that
of a worker bee. The larva stage lasts for 6 days for
worker and drone bees. It is of 5 - 5 ½ days duration
for the queen bee. Both the queen and worker bees
are the female bees but their future growth and Larva
development depends upon the food they are fed. The queen bee is fed
with royal jelly until it is fully grown whereas the worker bee is fed
with royal jelly for 3 days only. Then the worker bee is fed with bee
bread. The drone bees are also fed with royal jelly for 3 days and then
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with bee bread for remaining time. The larva undergoes moulting for
4 – 5 times. The process of shedding off skin and changing the body
form is called moulting.
Pupa stage Pupa
The bees remain inactive in a pupal case in pupa stage.
During this stage, the pupa does not eat anything. All
the external organs grow and develop fully during this
stage. The pupa stage of worker bee lasts for 12 days,
that of a drone lasts for 14 days and that of queen bee
lasts for 8 days.
Adult stage
The new worker bees perform different jobs inside
the hive for about three weeks. Inside the hive, their
job includes feeding larva, protecting and caring
larva, constructing and maintaining the hive comb,
etc. Then the worker bees get off the hive to perform
outside works. They collect nectar and pollens from
the flowers, protect the hive, fight against the enemies,
etc. They also convert collected nectar and pollens into Adult
honey in the honeycomb.
The worker bees perform a number of works. Their works according to
their age can be explained as given below:
1 – 3 days: The worker bees are very weak and delicate during the first
three days of their emergence from the pupal case. These bees are also called
baby bees. They learn to stand and walk in the beginning. Then they remain
attached to the honeycomb and provide warmth to eggs, larva and pupa. They
eat the food that is available nearby them. They also clean the comb cells to
some extents.
4 – 6 days: They feed mature larva with beebread. They also eat themselves.
7 – 11 days: The head gland gets developed in the head of worker bees. This
gland secretes royal jelly. The worker bees feed early larva and queen bee with
this royal jelly. The worker bees also eat a lot of food themselves. After the 11th
day, the head gland starts to degenerate.
12 – 17 days: The head gland dries up but four pairs of wax glands get
developed in the abdomen. The wax glands produce wax which is used by
worker bees to build honeycomb and the cells for larva.
18 – 20 days: The wax gland dries up and becomes functionless. A poison
gland and a stinger develop at the last segment of their abdomen. Such bees sit
near the entry point of the hive and provide security to it.
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21 days: The worker bee gets out of the hive to perform other functions. It
flies away to the fields and forest to collect nectar, pollens, water, latex, etc.
Advantages from honeybees
1. Honey
We obtain honey from honeybee which is rich in carbohydrates, minerals
and vitamins. The raw honey is a suitable nutritional supplement
because it is rich with antioxidants, minerals and vitamins. Honey
also possesses antiseptic and anti-bacterial properties.
2. Bee wax
The remains of honeycomb after the extraction of honey is used to
prepare wax. This wax is called bee wax. The bee wax can be used to
make candles, chemicals, etc.
3. Pollination
Bees help pollinate the flowers in the garden and the edible crops by
transporting pollen from flower to flower as they collect nectar to return
to their hives. The pollen attaches to the honeybees' hairy bodies and
rubs off on flowers as they collect nectar. The pollen transfer helps
plants to reproduce and produce fruit and seed.
Learn and Write
1. Silkworm is called queen of fibres. Why?
Silkworm produces silk which is the natural fibre of best quality.
It is shiny, attractive, durable and comfortable. Therefore,
silkworm is called the queen of fibres.
2. Silkworm should be killed in pupa stage to obtain silk fibres. Why?
The pupa cuts out the silk fibres into pieces to emerge out as an
adult. The cocoon is kept in hot water or air to kill the pupa, so
that the fibres can be obtained in a long form. If pupae are not
killed, the silk fibres will be got in small pieces.
Main points to remember
1. Silkworm is a butterfly like insect which produces silk in larva stage.
2. Farming of silkworm is called sericulture.
3. Silkworm passes through four stages in their life cycle. They
are egg, larva, pupa and adult.
4. Seri silkworm lays its eggs on mulberry leaves.
5. The eggs hatch into larvae after twelve days at the temperature
of 18°C to 25°C.
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6. The larva converts into pupa after passing through 5 instars.
7. The pupa remains inside puparium which is formed by
winding silk threads.
Exercise
A. Very short answer questions (1 mark )
1. What is cocoon? What is it made of ?
2. What does seri silkworm feed on?
3. Write down any two features of natural silk thread.
4. What is sericulture?
5. How many types of silk moths are reared in Nepal? What are
they?
6. In which stage of its life cycle does silkworm produce silk?
7. What is nuptial flight?
8. What is the number of chromosomes in unfertilized egg of
honeybee?
9. When does a queen bee mate with drones?
10. How does the larva that develops into queen differ from the
larva that develops into worker ?
11. What is royal jelly?
12. Write any two features of queen bee.
13. Write any two features of drone bee.
14. Write down the major function of drone bees.
15. In how many stages does the life cycle of honeybee complete?
What are they?
16. Write down any two features of worker bee.
B. Short answer questions (2 marks)
1. Which stage in the life cycle of silkworm will be affected
immediately if there is scarcity of mulberry plants? Explain
2. Why are silk moths considered as useful insects? Give any two
reasons.
3. Write any two differences between adult silkworm and its larva.
4. Write any two differences between drone bee and queen bee.
5. Differentiate between drone bee and worker bee.
6. Write any two characteristics of larva of silkworm on the basis
of body structure.
7. Why are eggs of silk moth stored in cold places during winter?
8. Why are pupae of silk moth killed inside cocoon before
extracting silk fibre?
9. Why is silkworm called queen of fibre?
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10. Honeybee is a social insect. Why?
11. Why is the larva of silk moth called voracious eater?
C. Long answer questions ( 3 marks)
1. Draw the diagram of larval stage of silkworm and label the
parts .
2. Describe the structure of a silkworm with a diagram.
3. Write the uses of honey.
4. Write down the major functions of worker bees.
5. Write any three things to be considered during sericulture.
D. Very long answer questions (4 marks)
1. Explain the life cycle of honeybee with a neat and labelled
figure.
2. Describe the life cycle of silk moth with a neat and labelled
figure.
3. Draw labelled diagram of larva stage of silkworm. Write the
importance of this stage.
4. Explain the division of labour in different types of honeybee.
Project Work
a. Visit a nearby silkworm farming site.
b. Observe mulberry plants, various stages of silkworms.
c. Observe the technique of farming.
d. Prepare a report about the farming of silkworm with
diagram and submit to your teacher.
Glossary
• Commercial : relating to the buying and selling of goods or
services
• Compound eyes : eyes of arthropoda that consist of a number
of small units
• Metamorphosis : a complete change
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Chapter Human Nervous
15 and
Glandular System Oliver Wolf Sacks
Oliver Wolf Sacks was a British neurologist, naturalist and
author who spent his professional life in the United States.
He believed that the brain is the "most incredible thing in
the universe." Estimated Periods: 7 (5T+2P)
Objectives
At the end of the lesson, students will be able to:
• tell the functions of brain and nerves and their relationship;
• explain reflex action;
• tell different hormones produced in human body and their functions;
All living things live in the environment. There occur different changes
in the environment. Living things respond to such changes in different
ways. For example, when we touch a Mimosa pudica plant, its leaflets
get collapsed. Similarly, when we put sugar on the ground, ants get
gathered on the sugar. Thus, we can say that both plants and animals
show response to the environmental changes.
The environmental change that causes an organism to show response
is called stimulus.
The response shown by an organism towards certain stimulus is called
reaction. In the above example, touching Mimosa plant is stimulus and
collapsing leaflets is reaction.
Animals use nervous system and endocrine system for showing response
but plants use only endocrine system for showing response.
Nervous system
It is a system of brain, spinal cord and nerves which control and co-
ordinate the activities of human body. It provides pathways by which
information travels from surroundings to the central nervous system
and vice versa. Human nervous system can be divided into three parts.
i) Central nervous system.
ii) Peripheral nervous system
iii) Autonomous nervous system
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Central nervous system Cerebrum
It is the controlling centre of human body. It
consists of brain and spinal cord.
Brain Cerebellum
Mid-brain
It is a highly delicate organ of central Pons varoli
nervous system. It is located inside a bony
box called cranium which protects it from Medulla oblongata
injury.
Spinal cord
The brain is composed of soft nervous Central nervous system,
tissues. It is completely covered by three
membranes which are together called meninges.
The outer membrane is called Cerebrum
duramater. The middle membrane
is called arachnoid and the inner
membrane is called piamater. The
duramater is thick and tough layer
of meninges which is attached to the Mid-brain
inner wall of cranium. Arachnoid
is the middle thin and soft layer Pons varoli Cerebellum
of meninges. The piamater is the Medulla oblongata Spinal cord
innermost layer of meninges which Human brain
is attached to the brain. The cavity
between the arachnoid and piamater is filled with a liquid called
cerebrospinal fluid. This fluid protects the brain and spinal cord
from injury. The brain consists of five parts. They are (i) Cerebrum
(ii) Cerebellum (iii) Mid-brain (iv) Pons varolii (v) Medulla oblongata.
Cerebrum
Cerebrum is the largest part of brain. It is also known as big brain. It
occupies about 80% of the total brain. It has a number of grooves and
ridges called convolutions which increase the area of brain 2200cm2.
Cerebrum is divided into two parts; right and left hemispheres, each
part is separated by a very deep fissure.
The cerebral hemispheres are covered by a thin layer of grey matter
called cerebral cortex. The cerebrum is the centre of mental abilities
such as thinking, learning, memorizing, reasoning, intelligence, etc. It
controls the feeling of love, admiration and hatred. It also controls the
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functions of perception, imagination, anger, mood, taste, pain, stress,
etc. If cerebrum stops functioning, such condition is called coma.
Fact &Reason
What happens when cerebrum stops to function?
When cerebrum stops to function, the person enters into coma.
Cerebellum or Small brain
There is a lemon sized semicircular structure which lies just below the
posterior part of cerebrum. It is called cerebellum. It is also called
small brain and occupies 10 percent of total weight of the brain. It has
the following functions.
i) It coordinates and controls voluntary body movements.
ii) It maintains the balance and equilibrium of the body.
iii) It maintains the muscular tone.
Alcohol mainly affects small brain. In drunk people, the cerebellum
cannot coordinate with the muscles. Hence, the drunk people cannot
walk properly.
Mid-brain
It is a part of brain that lies between cerebellum and pons varolli. Its
main function is to act as relay station between cerebellum and pons
varolli.
Pons varolii
It is located between the mid-brain and medulla oblongata. It also acts
as a relay station for the impulses.
Medulla oblongata
It is the posterior end of the brain. It continues downward as spinal
cord. Any kind of damage to it causes instantaneous death. It performs
the following functions:
i) It controls breathing, heart beat and blood pressure.
ii) It controls the activities like coughing, sneezing, swallowing,
vomiting, etc.
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iii) It controls the activities of alimentary canal such as peristalsis
movements, secretion of digestive juice, hormones, etc.
iv) It works as a bridge between the brain and spinal cord.
Spinal cord
Spinal cord is a long nerve tissue found inside the neural canal of
vertebral column. It extends from the medulla oblongata to the first
lumbar vertebra. It consists of white and grey matter. White matter
remains outside and the grey matter remains inside. It is also covered
by meninges. Any kind of damage to the spinal cord due to any disease
or accident can cause paralysis of the body parts below the injury.
The major functions of spinal cord are as follows:
i) It is the control centre for reflex action.
ii) It connects large part of peripheral nervous system to the
brain. Therefore, it acts as a passage way for the transmission
of impulses from different organs to the brain and brain to the
organs.
Nerves
Nerves are thread like structures which transmit impulses from one
part of body to another parts. An impulse is a message or a wave of
electrical disturbance that sweeps over the nerve cell. For example,
impulse of touch, impulse of hot, etc.
On the basis of origin, nerves are divided into two types. They are
cranial nerves and spinal nerves. The nerves that are originated from
the brain are called cranial nerves and the nerves that are originated
from the spinal cord are spinal nerves. There are 12 pairs of cranial
nerves and 31 pairs of spinal nerves.
Types of nerves
The nerves can be classified into three types on the basis of direction
of flow of impulses.
1) Afferent or sensory nerves
The nerves that carry impulses from organs to the brain or spinal
cord are called sensory nerves. When our skin touches hot object, the
impulses of hotness are carried to the brain by the sensory nerves. Here
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the hotness is impulse and the skin is receptor. The sense organs send
the impulse to the brain through sensory nerves. Olfactory nerves,
optic nerves, auditory nerves, etc are examples of sensory nerves.
2) Efferent or motor nerves
The nerves which carry impulses from brain or spinal cord to the various
organs are called efferent or motor nerves. Brain or spinal cord sends
instructions to the various parts for taking necessary action through
motor nerves. Vasomotor nerves, secretary motor nerves, facial motor
nerves, etc are examples of motor nerves.
3) Mixed nerves
Mixed nerves are the nerves which consist of both afferent and efferent
nerves.
Neurons Cell body
Nerves are made by the combination of nerve Dendrites
cells called neurons Nucleus
Neurons make nervous tissue of nervous Cytoplasm
system. Therefore, it is called structural and
functional unit of nervous system. A neuron medullary
sheath
consists of three parts, viz. cell body, axon
and dendrites. The cell body contains a large Axon
nucleus. It acts as a centre for sending and Boutons
receiving impulses. From cell body, two types
of nerve fibres arise. They are dendrites and Nerve cell
axon. Dendrites are highly branched and thin.
They receive impulses from another neuron and send to the cell body.
The axon is a long and tube like structure which carries impulses from
the cell body to dendrites of another neuron. The axon is covered with
medullary sheath.
Types of neurons
On the basis of function and structure, neurons are of three types.
i) Sensory neurons: The neuron which carries messages from the
receptors to the brain or spinal cord is called sensory neuron. It
has long dendrites and short axon.
ii) Motor neuron: It is the neuron which carries impulses from
brain or spinal cord to the receptors. It has long axon and short
dendrites.
283 Times' Crucial Science Book - 10
iii) Connecting neuron: It is the neuron which connects sensory
neuron and motor neuron. It converts sensory impulse to motor
impulse.
Synapse
In nervous system, axon of one neuron connects to dendrites of
another neuron and nerves are formed. The axon branches into minute
filaments and terminates into small swellings called synaptic knobs.
Synaptic knobs of one neuron remain very close to dendrites of another
neuron. There remains gap between synaptic knobs of a neuron and
dendrites and cell body of another neuron. This gap is called synapse.
Ganglion
A cluster of neuron bodies found in autonomous and peripheral
nervous is called ganglion. It communicates with brain and spinal
cord to regulate involuntary nervous system.
Peripheral nervous system
The peripheral nervous system consists of nerves which originate
from the brain and spinal cord. The nerves are of two types. They are
cranial nerves and spinal nerves.
Cranial nerves: These nerves originate from the brain. There are 12
pairs of cranial nerves in human body. They control the activities of
eyes, ears, tongue, etc.
Spinal nerves: These nerves originate from spinal cord and spread to
different organs. There are 31 pairs of spinal nerves in human body.
They carry both sensory and motor impulses.
Autonomous nervous system
Autonomous nervous system is concerned with the control and co-
ordination of automatic activities of human body. The working of heart,
kidneys, lungs, ureter, etc are under the control of the autonomous
nervous system. The autonomous nervous system is divided into two
parts. They are: sympathetic and parasympathetic nervous system.
Sympathetic nervous system and parasympathetic nervous system
function opposite in nature. Due to it, balance is maintained in body.
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Sympathetic nervous system increases blood pressure, heart beat rate,
blood flow to the brain at the time of sudden accidents. Parasympathetic
nervous system normalizes the situation after accidents. It means
parasympathetic nervous system decreases blood pressure, heart beat
and blood flow to the brain.
Current electricity travels at the speed of 1,50,000 km per second.
However, the nerve impulses travel at the speed of 100 m per second.
Glandular system
There are many glands in our body which secrete different types of
juices. Some of the secretions get directly mixed with the blood whereas
some of them pass to the related organs through duct.
Glands like pituitary, adrenal, thyroid, etc do not contain duct. Their
secretions directly get mixed to the blood. These glands are called
endocrine glands. Glands like salivary glands, liver, tear gland, etc
contain ducts. Their secretions get transmitted to the related organs
through ducts. These glands are called exocrine glands.
Differences between exocrine and endocrine glands
Exocrine glands Endocrine glands
1. They have ducts. 1. They do not have ducts.
2. Their secretion is carried to 2. Their secretion is carried through
related organs by the duct. blood stream to the related regions.
3. Their secretions are called 3. Their secretions are called
enzymes. hormones.
4. Their secretions are related 4. Their secretions are responsible
to the life processes like for control and co-ordination of
respiration, digestion, etc. growth.
5. Consumption of their 5. Consumption of their secretion
secretions is more in amount. is less in amount.
6. Distance between the glands 6. Distance between the gland and
and the working organ of the working organ is more
the juice is less.
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Hormones Pituitary
Hormones are the special type of secretions Thyroid
produced by endocrine glands. They are
transported by the blood to a particular Pancreas
organ or tissue. Hormones are chemicals. Adrenal
They control and co-ordinate the activities gland
of various parts of our body. Therefore, Ovary
they are called chemical messengers. (female)
Following endocrine glands are present
in human body. Testes
(male)
Fact &Reason Endocrine glands in human
Hormones are called chemical messengers, why?
Hormones are the chemical substances which help to control, coordinate, and
integrate various physiological processes and activities of the body. So, hormones
are called chemical messengers.
1. Pituitary gland
It is a small endocrine gland, located at the lower portion of the brain.
Its shape and size is like a pea. It has three lobes namely anterior,
intermediate and posterior lobe. It produces two types of hormones:
trophic hormones or stimulating hormones and non-tropic hormones
or growth hormones. The tropic hormones control the activities of other
glands. For example, thyroid gland controls the activities of thyroid
gland. Similarly, follicle stimulating hormone controls activities of
ovary. Since, the hormones produced by pituitary gland control the
activities of other glands. Therefore, it is called master gland.
Growth hormone controls the growth of children. Undersection of
pituitary hormones in children causes the dwarfism. It also causes
obesity, poor development of sex organs, etc. whereas over secretion
causes excessive tallness called gigantism. It causes acromegaly i.e.
enlargement of bones of hands, feet and face)
Fact &Reason
Why is pituitary gland called master gland?
Pituitary gland is called master gland because it controls the secretion and
activities of all other endocrine glands.
2. Thyroid gland
Thyroid gland consists of two lobes each lies at either side of trachea.
286Times' Crucial Science Book - 10
Two lobes are connected by a narrow mass of tissue called isthmus.
This gland produces thyroxin, triiodothyronine
and thyrocalcitonin hormones. To produce
these hormones, iodine is necessary. The
deficiency of iodine in the body leads to the
swelling of thyroid gland. It is called goitre. Thyroid
cartilage
Thyroid hormones are responsible for Thyroid
regulating the metabolic rate of body, gland
stimulate protein synthesis, maintain body Trachea
temperature and suppress release of calcium Positions of human
ions from the bones and accelerates mental thyroid glands
development. Deficiency of thyroid hormones cause the problems like
puffiness and roughness of the skin, falling of hairs, stammering and
sign of obesity, etc. The under secretion in infant stage results in slow
mental and physical growth with dry and rough skin, deformed teeth
and bones, etc. It is called cretinism. Over section of this hormone
causes loss of weight, mental imbalance, bulging of eyes, disorder in
digestive system, increased heartbeat rate, excessive excitement, etc.
3. Parathyroid gland
There are two pairs of parathyroid glands just below the thyroid gland.
One pair of parathyroid glands are located at each lobe. The hormone
secreted by the parathyroid gland is called parathormone. It controls the
exchange of calcium between blood and bone. It reduces the excretion
of calcium in urine. It helps for the normal growth of bones and teeth.
Undersecretion of parathormone leads to decrease in calcium level in
the blood. There is uncontrolled contraction of muscles of larynx, face,
hands and legs. This disorder is called tetany. Oversecretion of this
hormone causes increase in calcium level in the blood and decrease
in calcium level in the bone. Increased level of calcium in blood leads
to parathyroid tumor and kidney stone. Similarly, decreased level
of calcium in bones leads to weak and porous bones. This is called
osteoporosis.
Adrenal gland
The adrenal medulla secretes the hormones epinephrine and nor-
epinephrine. These hormones are together known as adrenaline. The
adrenaline is responsible for maintaining the blood pressure. It also
secretes the hormone named cortisone. Sometimes cortisone acts as a sex
287 Times' Crucial Science Book - 10
hormone. Adrenal
gland
The adrenal gland secretes
adrenaline hormone at the time Kidney
of emergency which prepares the
body to face any emergency situation Adrenal glands
such as excitement, fright or anger.
Therefore, adrenaline is called
emergency hormone and adrenal
gland is called emergency gland.
Disorders
The under-secretion of adrenaline results in weakness, low blood pressure,
less sugar content in blood, nausea, unconsciousness, etc. The over-
secretion of adrenaline causes hypertension. It may cause death.
The over-development of adrenal cortex in an adult male may cause over-
secretion of cortisone. It causes the appearance of feminine characters
such as big size of breast, shrill voice, etc. Similarly, the over-secretion of
cortisone in adult female causes the appearance of masculine characters
such as moustache, hoarse sound, etc.
Fact &Reason
Why is adrenal gland called emergency gland?
Adrenal gland produces hormone called adrenaline hormone which prepares the
body to face the emergency situations like flight, fright and fight. So, adrenal
gland is called emergency gland.
Pancreas Stomach
Pancreas
Pancreas is mixed gland
because it produces hormones Pancreas
insulin and glucagon
as endocrine gland and
pancreatic juice as exocrine
gland. It is located at the loop
of duodenum. The hormones
insulin and glucagon maintain
sugar level in the blood.
Glucagon increases the sugar Pancreatic
level in the blood whereas duct
insulin decreases sugar level in the blood.
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Undersecretion of insulin causes the increase in sugar level in the
blood and the person suffers from diabetes. Feeling hungry, thirsty,
appearance of sugar in the urine, loss of weight, delay in wound
healing, etc are symptoms of diabetes.
The oversecretion of insulin causes low sugar level in the blood.
Gonads
Testes of male and ovaries of females are called gonads. They are also
called reproductive glands.
Testes are oval glands of males which produce the hormones named
testosterone and androgen. These hormones stimulate the development
of secondary sex characters like appearance of pubic hair, development
of sexual desire, enlargement of larynx, hoarse voice, etc.
Ovaries are the reproductive organs of females which are located inside
the lower abdominal cavity. Ovaries produce two hormones named
oestrogen and progesterone. Oestrogen regulates the development of
sex characters of females such as growth of breast, growth of pubic
hair, development of buttock etc. The progesterone controls the release
of ova from ovary. It also helps in maintenance of pregnancy.
Undersecretion of gonad hormone results in the retarded development
of secondary sex characters in adolescence. The oversecretion of gonad
hormones causes the premature development of sex characters such
as growth of breasts, development of pubic hair in early stage, etc.
Learn and Write
1. Pituitary gland is called master gland. Why?
The hormones produced by the pituitary gland controls the activities
and secretion of other glands. Therefore, pituitary gland is called
master gland.
2. Pancreas is called mixed gland. Why?
Pancreas works as endocrine as well as an exocrine gland. As an
endocrine gland, it produces hormones named insulin and glucagon
and as an exocrine gland, it produces pancreatic juice. Thus, it is
called mixed gland.
3. Cerebrum is the main part of our nervous system. Why?
Cerebrum is the centre for the main activities of our body. It
governs the mental abilities like thinking, learning, reasoning,
289 Times' Crucial Science Book - 10
memory, intelligence, etc. It controls feeling of love, emotions,
sentiments, etc. Thus, it is the main part of our nervous system.
Main points to remember
1 Nervous system is the system which controls and co-ordinates all
the activities of human body.
2 Nervous system is divided into central and peripheral nervous system.
3 Nerves are the thread like structures which carry the impulses
from one part to another part of our body.
4 Neuron is a nervous cell which consists of cell body, axon and dendrites.
5 Central nervous system consists of brain and spinal cord.
6 Brain is the most important part of nervous system which controls
and co-ordinates the activities of our body.
7 Cerebrum, cerebellum, mid-brain, pons varolli and medulla
oblongata are the main parts of the brain.
8 Spinal cord is a long cylindrical structure that arises from the
medulla oblongata and passes through the neural canal of the
vertebral column.
9 Immediate response to a certain stimulus is called reflex action.
10 The gland whose secretion gets directly mixed to the blood is
called endocrine gland.
11 Pituitary gland is called master gland because it controls
activities and the secretion of other glands.
12 Thyroid gland, parathyroid gland, adrenal gland, pancreas,
gonads, etc are examples of endocrine glands.
Exercise
A. Very short answer questions (1 mark)
1. Where is cerebrospinal fluid found ?
2. Name the three membranes that covers the brain.
3. What is the main function of cerebrospinal fluid?
4. What is nervous system?
5. How many numbers of spinal nerves are present in human
body?
6. What is spinal cord ?
7. State the major functions of the spinal cord.
8. Which part of central nervous system conducts reflex action ?
9. What is meant by ganglion ? Write its function.
10. Write the main function of insulin hormone.
11. What happens when cerebrum stops working?
290Times' Crucial Science Book - 10
12. Which hormone is responsible for the following functions ?
i) Balances calcium level in bone
ii) Maintains the level of sugar in blood
13. Write any two effects of hypo secretion of insulin.
14. Write down the functions of testosterone.
15. What are hormones?
16. Name a hormone that is produced by thyroid gland.
17. Write name of two hormones produced by pituitary gland.
18. Where is thyroid gland located in human body?
19. Name the hormone secreted by parathyroid gland with its
function.
20. What disorders are caused due to hypo secretion and hyper
secretion of growth hormone ?
21. Name hormones secreted by testes.
B. Short answer questions (2 marks)
1. Differentiate between axon and dendrites:
2. Write any two effects that are seen due to lack of thyroxine
hormone.
3. Write any two functions of medulla oblongata.
4. Differentiate between endocrine and exocrine glands.
5. Write any two differences between cranial nerves and spinal
nerves.
6. Adrenalin is called emergency hormone, why?
7. Pancreas is called a mixed gland, why?
8. Why are hormones called chemical messengers?
9. Pituitary gland is called master gland. Why?
10. Write any two causes of increasing uric acid.
C. Long answer questions (3 marks)
1. Write the major functions of human brain.
2. What is cerebellum ? Describe its structure and functions.
3. State any three functions of nervous system.
4. Draw a neat and labeled figure showing the structure of
neuron.
5. Draw a neat and labelled diagram showing the location of
endocrine glands in the human body.
6. Draw a diagram of different parts of brain.Damage of which
part of brain causes sudden death? Show this part in diagram.
7. Where are testes located in human body? Name the hormone
secreted by testes. Also state the functions of that hormone.
291 Times' Crucial Science Book - 10
8. Differentiate between:
i) Brain and spinal cord
ii) Sensory and motor nerves
iii) Central and peripheral nervous system
iv) Endocrine gland and exocrine gland
v) Cerebrum and cerebellum
D. Very long answer questions (4 marks)
1. A, B and C are endocrine glands. If A is called master gland,
B is called emergency gland and C is called mixed gland then
answer the following questions.
a. Write the name of glands A and B.
b. What difference is seen in the body of men containing
more and less hormone produced by A?
c. Why is B called emergency gland?
d. If diabetes is seen in any man, which gland is not
working properly?
2. Label the parts shown in the figure and write the function of
each part.
D
E
F
292Times' Crucial Science Book - 10
3. Label the parts shown in the figure and write the function of
each part
B
A
C
Glossary
• Gather : to collect, to amass something
• Fissure : a long narrow crack or opening
• Coma : a prolonged state of deep unconsciousness
• Impulse : a progressive wave of biochemically generated
energy that travels along a nerve fiber or
muscle and stimulates or inhibits activity
• Olfactory : used in smelling or relating to the sense of
smell
• Vasomotor : causing or influencing changes in the
diameter of blood vessels
• Undersecretion : insufficient secretion
293 Times' Crucial Science Book - 10
Chapter
Blood Circulatory
16 System in Human
Beings William Harvey
William Harvey was an English physician who made
seminal contributions in anatomy and physiology.
He discovered the circulation of blood in human
body. Estimated Periods: 6 (5T+1P)
ObAjetctthieveesnd of the lesson, students will be able to:
• describe the composition and functions of blood;
• describe the circulation of blood in human body with diagram.
Every organism needs oxygen, water, hormones, nutrients, etc to be
supplied to every cell. The waste materials such as carbon dioxide,
urea, uric acid, waste products, etc need to be removed from the cells.
In animals, transportation of those things is done by blood and fluids
whereas it is done in plants by xylem and phloem. In human body,
transportation of oxygen, nutrients, hormones, etc is done by blood
circulatory system.
The blood circulatory system consists of mainly three parts: blood,
blood vessels and heart. Thus, blood circulatory system is a group
of organs which are responsible for the transportation of substances
inside the body.
Blood
Blood is a fluid connective tissue which keeps on circulating throughout
the body. It consists of blood cells suspended in plasma. It is red in
colour.
Plasma
It is liquid portion of blood. It constitutes 55% of the total blood volume.
It is a straw coloured transparent liquid. It contains 90% water
and 10% other substances like dissolved food, mineral salts, waste
products like urea, uric acid, ammonia, etc. It also contains proteins
like fibrinogen, albumin, globulin and various types of hormones. It
also contains heparin which prevents blood circulating in the blood
vessel from clotting.
294Times' Crucial Science Book - 10
Functions
i) It transports digested foods such as glucose, amino acids,
etc to various parts of the body.
ii) It transports excretory products to the excretory organs.
iii) It transports carbon dioxide to the lungs.
iv) It carries hormones secreted by endocrine glands to the various parts.
v) It regulates body temperature, amount of water and other
chemicals in the body.
Blood cells RBC
There are three types of WBC
blood cells suspended in the Platelets
Plasma
blood. They are: erythrocytes,
leucocytes and platelets. Structure of Blood
Erythrocytes (Red blood cells: RBCs)
They are disc shaped cells. They are biconcave, i.e. pressed
inwards in the middle. They do not contain nucleus. They are
covered by highly elastic membrane which enables them to pass
through fine capillaries too. About 4.5 to 5 million RBCs are present in
1 cubic millimeter of blood. They are formed in red bone marrow and
destroyed in spleen and liver.
The erythrocytes contain haemoglobin which is iron rich pigment.
It makes the blood red in colour. Haemoglobin carries oxygen
from lungs to the different cells. The haemoglobin with oxygen is
called oxyhaemoglobin. It is scarlet in colour. The oxyhaemoglobin
decomposes to release oxygen in the tissue. The decrease in the number
of red blood cells causes the disease named anaemia. It is mainly
caused due to malnutrition. Loss in weight, pale and dull coloured
skin, loss of appetite, etc are symptoms of anaemia.
Leucocytes (White blood cells: WBCs)
Leucocytes are larger blood cells. They are less in number. Generally
8,000 to 10,000 WBCs are present in 1 cubic millimeter of blood. They
have no fixed shape. They contain large nucleus. WBCs are of two
types. They are granulocytes and agranulocytes. The WBCs which have
granules in their cytoplasm are called granulocytes. They are of three
types. They are neutrophils, basophils and eosinophils. Agranulocytes
donot have granules in their cytoplasm. They are of two types. They
are lymphocytes and monocytes.
295 Times' Crucial Science Book - 10
WBCs are produced in bone marrow and lymph gland. They fight with
disease germs and destroy them. If the number of WBCs in our body
is higher than the normal number, then the person may suffer from a
disease called leukemia. It is also called blood cancer.
Functions
a. They fight with disease germs.
b. They produce antibodies against different pathogens and
protect the body against specific diseases.
c. They destroy the damaged cells by phagocytosis.
Differences between red blood cells and white blood cells
RBCs WBCs
1. RBC is small and biconcave 1. WBC is large and irregular in shape.
in shape.
2. They are about 4 to 5 millions 2. They are about 8000 to 10000 in 1
in 1 cubic millimeter of blood. cubic millimeter of blood.
3. Haemoglobin is present in it. 3. Haemoglobin is absent in it.
4. They carry oxygen from 4. They fight with disease germs.
lungs to various cells.
5. They do not have nucleus. 5. They have nucleus.
Thrombocytes (Platelets)
Platelets are fragments of larger cells. They are smaller in size.
They lack nucleus and are irregular in shape. They are also produced
in red bone marrow. Their number ranges between 2 to 4 lakhs in one
cubic millimeter of blood.
Functions
They clot blood during injury and prevent excessive bleeding.
Blood clotting
When the blood is exposed to the air due to wound or injury it changes into a
jelly-like mass. The process of solidification of blood is called blood clotting.
Functions of blood
The main functions of blood are as follows.
(i) Transportation (ii) Regulation (iii) Protection.
296Times' Crucial Science Book - 10
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