Science 7

Functions
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Plastids Plastid
Plastids are rod, spherical or oval shaped cell
organelles present in plant cells. They are absent
in animal cells. Plastids are of three types:
Chloroplast, chromoplast and leucoplast.
Chloroplasts are green plastids. They are green
due to the presence of chlorophyll. Photosynthesis
process takes place in chloroplast and food is
prepared in it. Thus, it is called kitchen of plant cell.

Chromoplasts DUH FRORXUIXO SODVWLGV 7KH\ DUH IRXQG LQ WKH SHWDOV RI ÁRZHUV
and pericarp of fruits. They contain colourful pigments such as red, yellow,
orange, etc.

Leucoplasts are colourless plastids. They are found in the cells of
underground parts of plants. Due to leucoplast, certain parts of plants are
white.

Functions
a. Chloroplasts are the sites for food preparation in plant cells.
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c. Leucoplasts store foods in the form of carbohydrates and proteins.

Endoplasmic reticulum

Endoplasmic reticulum is a system of tubular Endoplasmic reticulum
structure running from cell membrane to the
nucleus. It forms the endoskeleton of the cell.
Endoplasmic reticulum is of two types: smooth
endoplasmic reticulum and rough endoplasmic
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of rough endoplasmic reticulum whereas they
are absent in smooth endoplasmic reticulum.
Functions

a. It is the supporting framework of a cell.

b. It helps in the transport of materials within the cell.

c. It provides a large surface area to the cytoplasm for various metabolic
activities.

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Ribosomes

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surface of endoplasmic reticulum. They are found freely in the
cytoplasm, too. They are present in both animal and plant cell.

Function Ribosomes

They synthesize protein in the cell.

Golgi Bodies

Golgi bodies consist of a set of membrane bound
vesicles and tubules. They are present in both animal
and plant cells. They are generally found near the
nucleus in cytoplasm.

Functions Golgi body
a. It acts as a site for cellular secretions.

b. It is responsible for the synthesis of cell membrane, cell wall, etc.

Lysosomes

Lysosomes are sac like cell organelles present in Lysosomes
the cytoplasm of animal cells. They are absent in
plant cells. Each lysosome is surrounded by a single
membrane. Lysosome produces powerful chemicals
which digest various types of materials. They can
digest the damaged and poisonous cells. Therefore,
they are called suicidal bags of the cell.

Functions

They digest various substances of the cell.

Centrosome

Centrosome is a small star like structure and
located close to the nucleus of animal cells. They
are absent in plant cells. It contains small two
granules called centrioles and astral rays.

Functions Centrosome
a. It helps in cell division.

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Vacuoles

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plant and animal cell. In the plant cell, they are large and are found in the
middle part of the cell. In animal cell, they are small and are scattered in

Times' Crucial Science and Environment 198 Book 7

the cytoplasm. Vacuoles contain water, protein, sugar, waste materials,
etc. Therefore, they are called storehouse of cells.

Functions
a. They help to make the cells rigid.

b. They store water, minerals and waste products.

Nucleus

Nucleus is a spherical or oval dense part present in the cytoplasm. It is
located at the centre in an animal cell
and at the side of large vacuole in plant Nuclear membrane

cell. Nucleus is covered by a membrane Nucleoplasm

called nuclear membrane. The semi-liquid
substance present inside the nucleus is
nucleoplasm. It contains nucleolus and Nucleolus

chromosomes. Nucleolus is a dense and
round structure present in the nucleoplasm.
Chromosomes are thread like structures
which are responsible for the determination
of characters of an organism.
Chromatin reticulum

Functions Structure of nucleus

a. Nucleus controls various activities taking place in a cell.

b. It helps in cell division.

c. Chromosomes present in the nucleus determine characters of an
organism and transmit those characters to the offspring.

Differences between Plant Cell and Animal Cell

Plant Cell Animal Cell

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Times' Crucial Science and Environment 199 Book 7

Activity 18.2 7R VWXG\ WKH SDUWV RI FHOOV

Draw a plant cell and an animal cell in a chart paper. Label their important
parts and paste the chart paper on the wall of your classroom.

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all life activities such as nutrition, respiration, reproduction, etc take place
within a single cell.

There are various species of 3VHXGRSRGLD
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are parasitic and found in F9oDoFdXRVOaHcuole
water, mud and in the intestine
of human being. Entamoeba (FWRSODVP
histolytica causes dysentery 1XFOHXV
in human being. This kind of
parasite enters the human body
through polluted water.
Structure of Amoeba

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not be seen with naked eyes. We $PRHED
need microscope to see it. It is
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and colourlessness.

Body of amoeba contains only one cell. It is covered by a membrane
named plasmalemma. It is elastic in nature. Due to its elasticity, its shape
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projections are formed. They are called pseudopodia. Literal meaning of
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such pseudopodia.

Inside plasmalemma, there is a liquid named protoplasm. It has two parts.
Outer non-granular part is called ectoplasm and inner granular part is
called endoplasm.

Contractile vacuole, food vacuole and nucleus are present in the endoplasm.
The vacuoles containing food are called food vacuoles.

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The nucleus with chromatin material is situated in the endoplasm. It
controls the activities taking place inside the body.

Times' Crucial Science and Environment 200 Book 7

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Nutrition
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pseudopodia. The food is digested in food vacuoles with the help of enzyme.
The digested food is absorbed in the endoplasm.
Respiration
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is thrown out in the similar way.
Excretion
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It moves slowly towards the peripheral region and gets burst to throw out
the waste materials.
Movement
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whenever required.
Reprodution
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growth, it divides into two Amoebae. Thus, two daughter Amoebae are
formed from one Amoeba.

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In unfavourable condition, Amoeba PXOWLSOLHV E\ PXOWLSOH ÀVVLRQ WRR ,Q
PXOWLSOH ÀVVLRQ DQ Amoeba divides into many Amoebae.
Hydra
Hydra is a multicellular animal. Its body is made up of many cells. It is
found in cool and fresh water. It is found attached with substratum. Hydras
are of various species. But, common hydra is green in colour and is found
in water of ponds and lakes.
Structure
Hydra is a polyp like animal with cylindrical body. It measures about 1cm
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Times' Crucial Science and Environment 201 Book 7

called tentacles. Its mouth is called hypostome and is surrounded by
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attached to substratum.

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fully matured, get detached from the parent body. Thus, buds grow into
new hydra.
The hydra contains a body cavity called coelenteron. It is surrounded by
body wall. The body wall is made up of two layers. Therefore, it is called
diploblastic. The two layers of the body wall are outer ectoderm and inner
endoderm.
Nutrition
Various activities taking place in the body of hydra are as follows:
Hydra feeds on small aquatic animals. Tentacles capture the foods and
keep in the mouth. Food is digested and absorbed in the body. Undigested
foods are ejected through the mouth.
Respiration
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surface. They don’t have special organs for respiration.
Movement
Hydra moves from one place to another with the help of tentacles. It moves
in different ways.

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Times' Crucial Science and Environment 202 Book 7

Reproduction
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from the lateral side of hydra. The buds when become mature, get detached
from the parent body. Then, they start individual life.
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1. Cell is the structural and functional unit of living things.
2. Living substance present in a cell is called protoplasm.
3. The cytoplasmic bodies which are living and are covered by

membranes are called cell organelles.
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5. Plants are green in colour and can prepare their foods by

photosynthesis due to the presence of chloroplast.
6. Endoplasmic reticulum provides cellular framework.
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Times' Crucial Science and Environment 203 Book 7

8. Golgi bodies consist of a set of membrane bound vesicles and
tubules.

9. Lysosomes produce the powerful enzymes and kill the cells also.
Therefore, it is also called suicidal bag.

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and nucleolus. Nucleus controls all activities of a cell.

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plasmalemma, cytoplasm, nucleus, etc.

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various activities taking place in amoeba.

13.Hydra is a multicellular animal with a cylindrical body.

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1. Choose the best alternative in each case.

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i. Cell wall ii. Cell membrane

iii. Nucleus iv. Cytoplasm

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i. Vacuole ii. Plastid

iii. Golgi body iv. Centrosome

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i. Plastid ii. Cell wall

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iii. Hydra iv. Euglena

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i. Cilia ii. Pseudopodia

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Times' Crucial Science and Environment 204 Book 7

2. Copy the correct statements. And correct the false statements
if any.
a. Cell membrane is the outermost cover of plant cell.
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c. Non-living things present in the cytoplasm are called cell
inclusions.
c. Plants are green in colour due to the presence of leucoplast.
d. Centrosomes are present in an animal cell only.
e. Vacuoles are large in plant cells.
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h. Hydra reproduces through tentacles.
i. Hydra is a triploblastic animal.

3. Answer these questions in short.
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M :KDW DUH WHQWDFOHV" 0Hntion functions of tentacles.

4. Give reasons:
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b. Cell is structural and functional unit of living things.
c. Lysosomes are called suicidal bags of a cell.
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e. Chloroplast is called kitchen of a plant cell.
f. Vacuole is called storehouse of a cell.

Times' Crucial Science and Environment 205 Book 7

5. Differentiate between:
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b. Unicellular and multicellular organism
c. Cell wall and cell membrane
d. Cell organelles and cell inclusions

6. Answer these questions in detail.
a. Describe the structure and functions of cell wall.
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d. Describe the structure and function of endoplasmic reticulum.
e. Describe the structure of amoeba.
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h. Copy the following diagram and label important parts.

7. Draw labelled diagrams of: F +\GUD
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Collect the dirty water from ditch or stagnant pond. Take a drop
of water in a slide and observe under the microscope. You may see
micro-organisms of water such as Amoeba, Paramecium, etc. If you
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drops.

Times' Crucial Science and Environment 206 Book 7

Chapter

19 /LIH 3URFHVV

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϭϮ

OBJECTIVES
At the end of the lesson, the students will be able to :
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 ĚĞĮŶĞ ďƌĞĂƚŚŝŶŐ ĂŶĚ ƌĞƐƉŝƌĂƟŽŶ͘
 ƚĞůů ǀĂƌŝŽƵƐ ŽƌŐĂŶƐ ĨŽƌ ďƌĞĂƚŚŝŶŐ͘
 ĞdžƉůĂŝŶ ƌĞƐƉŝƌĂƟŽŶ ƉƌŽĐĞƐƐ ŝŶ ĂŶŝŵĂůƐ ĂŶĚ ƉůĂŶƚƐ͘
 ĞdžƉůĂŝŶ ĚŝŐĞƐƟŽŶ ƉƌŽĐĞƐƐ ŝŶ ŚƵŵĂŶ ďĞŝŶŐ͘
 ĞdžƉůĂŝŶ ĞdžĐƌĞƟŽŶ ƉƌŽĐĞƐƐ ŝŶ ĂŶŝŵĂůƐ ĂŶĚ ƉůĂŶƚƐ͘
MIND OPENERS
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 tŚĂƚ ŝƐ ĚŝŐĞƐƟŽŶ͍ /Ɛ ŝƚ ŝŵƉŽƌƚĂŶƚ ĂĐƟǀŝƚLJ ŝŶ ŽƵƌ ďŽĚLJ͍
 tŚLJ ŝƐ ĞdžĐƌĞƟŽŶ ŝŵƉŽƌƚĂŶƚ ĨŽƌ ůŝǀŝŶŐ ƚŚŝŶŐƐ͍
 ,Žǁ ĚŽ ƉůĂŶƚƐ ĐĂƌƌLJ ŽƵƚ ĞdžĐƌĞƟŽŶ ƉƌŽĐĞƐƐ͍

Introduction

Various activities are taking place inside body of living things to make
them alive. These activities are called life processes. When living things
die, life processes stop. The term metabolism is also used for life processes.
Inside living things, various chemical changes are taking place. The sum of
all the chemical changes is called metabolism. 0HWDEROLVP LV RI WZR W\SHV
anabolism and catabolism.
Anabolism is the synthesis of large molecules from smaller molecules. For
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IURP FDUERQ GLR[LGH DQG ZDWHU Catabolism is breaking down of large
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respiration, food breaks down into smaller molecules and energy is released.

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Every living thing needs foods to survive. They cannot survive without
food. The process of taking food is called nutrition. Food provides nutrients
which are required for the growth and development of living things.

Times' Crucial Science and Environment 207 Book 7

The process of taking food differs from organisms to organisms. Human
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should be broken to smaller and simpler forms. The process of breaking
down complex food materials into simpler and soluble form is called
digestion.

Various types of enzymes are required for the digestion of food. These
enzymes are produced by various glands. Salivary gland, gastric gland,
liver, pancreas and intestinal gland are the various glands which produce
enzymes for the digestion of food in human body.

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to anus called alimentary canal. It consists of following parts:

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b) Oesophagus

c) Stomach Tongue Oral cavity
d) Small intestine Mouth Pharynx
e) Large intestine
Salivary glands Esophagus

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Mouth Liver

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alimentary canal. It contains Gall bladder

a cavity called oral cavity. Pancreas

It contains a tongue, teeth Small Intestine
and palate. When the food
is eaten, it is chewed by the Large Intestine

teeth. The food is made soft Rectum Anus
by the saliva produced by
salivary gland. The enzyme
Human digestive system

ptyalin contained in the saliva digests carbohydrate into maltose.

Oesophagus

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stomach. This process is called swallowing.

Stomach

It is the widest part of alimentary canal. Its walls contain gastric glands
which produce gastric juice. ,W FRQWDLQV K\GURFKORULF DFLG DQG HQ]\PHV
named renin and pepsin. Hydrochloric acid kills the disease germs present
in the food and provides acidic medium.

Times' Crucial Science and Environment 208 Book 7

In acidic medium pepsin FKDQJHV SURWHLQ LQWR SHSWRQH DQG SURWHRVH 5HQLQ
changes milk protein into casein.

Small Intestine

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ends at large intestine. The front part of the small intestine is called
duodenum and the back part is called ileum. The duodenum is ‘C’ shaped.
The bile juice from liver and pancreatic juice from pancreas pass towards
duodenum through a common duct. Pancreatic juice contains enzymes-
trypsin, amylase and lypase. Trypsin digests protein into peptides and
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into fatty acids and glycerol. Bile does
not contain any enzyme but neutralizes Villi

the acidic medium created by HCl. It
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wall of intestine also contains gland
named intestinal glands. They produce
enzymes named erepsin, maltase,
sucrase, and lactase. The erepsin digests
the peptides and converts to amino acid.
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Sucrase converts sucrose to glucose.
Villi in ileum

Lactase converts lactose to glucose.

The digestion of food completes in small intestine. The digested food is
absorbed by the villi of ileum. Villi DUH ÀQJHU OLNH SURMHFWLRQV LQWR WKH
lumen of ileum. Villi increase the surface area for the absorption of food.
They are richly supplied with blood vessels. The digested food is absorbed
to the blood vessels and supplied to various parts through blood vessels.

'LJHVWLYH JODQG HQ]\PHV DQG WKHLU IXQFWLRQ

Organ ŝŐĞƐƟǀĞ ŝŐĞƐƟǀĞ Enzyme Food acted Product
gland juice upon

Mouth ^ĂůŝǀĂƌLJ ^ĂůŝǀĂ WƚLJĂůŝŶ ^ƚĂƌĐŚ DĂůƚŽƐĞ
ŐůĂŶĚ

Stomach 'ĂƐƚƌŝĐ 'ĂƐƚƌŝĐ WĞƉƐŝŶ͕ WƌŽƚĞŝŶ WĞƉƚŽŶĞƐ
ŐůĂŶĚ ũƵŝĐĞ ZĞŶŝŶ

Duodenum WĂŶĐƌĞĂƐ WĂŶĐƌĞĂƟĐ dƌLJƉƐŝŶ͕ WĞƉƟĚĞ͕ ŵŝŶŽ ĂĐŝĚ͕
ũƵŝĐĞ ŵLJůĂƐĞ ƐƚĂƌĐŚ͕ DĂůƚŽƐĞ͕
>ŝƉĂƐĞ
&ĂƚƐ &ĂƩLJ ĂĐŝĚ ĂŶĚ
ŐůLJĐĞƌŽů

Times' Crucial Science and Environment 209 Book 7

Ileum /ŶƚĞƐƟŶĂů /ŶƚĞƐƟŶĂů ƌĞƉƐŝŶ WĞƉƟĚĞ ŵŝŶŽ ĂĐŝĚƐ
ŐůĂŶĚ :ƵŝĐĞ DĂůƚĂƐĞ DĂůƚŽƐĞ 'ůƵĐŽƐĞ
^ƵĐƌĂƐĞ ƐƵĐƌŽƐĞ 'ůƵĐŽƐĞ
>ĂĐƚĂƐĞ ůĂĐƚŽƐĞ
'ůƵĐŽƐĞ ĂŶĚ
ŐĂůĂĐƚŽƐĞ

/DUJH ,QWHVWLQH

It is about 1.5 meter long and consists of three parts: caecum, colon and
rectum. In large intestine, water is absorbed from the undigested food. The
H[FHVV RI XQGLJHVWHG IRRG LV HMHFWHG RXW WKURXJK WKH UHFWXP

$VVLPLODWLRQ

7KH DEVRUEHG IRRG JHWV PL[HG WR WKH EORRG 7KURXJK WKH EORRG WKH DEVRUEHG
food is distributed throughout the body. Then the food is utilized to produce
energy. This process is called assimilation.

%UHDWKLQJ DQG 5HVSLUDWLRQ

Living things cannot survive without energy. Energy is obtained by
WKH UHDFWLRQ RI IRRG ZLWK R[\JHQ LQ PLWRFKRQGULD 7KLV SURFHVV LV FDOOHG
UHVSLUDWLRQ ,Q WKLV SURFHVV FDUERQ GLR[LGH DQG ZDWHU DUH DOVR SURGXFHG DV
products.
Respiration is the process in which food reacts with oxygen to release energy.
2[\JHQ LV VXSSOLHG WR WKH ERG\ RI OLYLQJ WKLQJV E\ WKH SURFHVV RI EUHDWKLQJ

Food + Oxygen o Energy + CO2 + H2O

Breathing is the process by which oxygen is taken in and carbon dioxide
is thrown out. ,W LV DOVR FDOOHG H[WHUQDO UHVSLUDWLRQ 7KH SURFHVV RI WDNLQJ
LQ R[\JHQ LV FDOOHG inhalation DQG WKURZLQJ RXW FDUERQ GLR[LGH LV FDOOHG
exhalation.

%UHDWKLQJ WKURXJK 6SLUDFOHV 7UDFKHDO
WXEH
Insects like grasshopper, cockroach, 6SLUDFOHV
PRVTXLWR EXWWHUÁ\ HWF EUHDWKH WKURXJK
a system of air tubes present inside their
body. These tubes are called tracheal
tubes. They open outside through small
openings called spiracles.
7KH\ EUHDWKH LQ R[\JHQ DQG EUHDWKH RXW
FDUERQ GLR[LGH WKURXJK VSLUDFOHV 7KH
R[\JHQ UHDFKHV WKH HYHU\ FHOO WKURXJK
the tracheal tubes.

Times' Crucial Science and Environment 210 Book 7

%UHDWKLQJ WKURXJK JLOOV

$QLPDOV OLNH WDGSROHV RI IURJ ÀVK HWF KDYH
special organs called gills for breathing.
They are covered by operculum. Gills
DUH PDGH XS RI ÀODPHQWV ZKLFK DUH ZHOO
supplied with blood vessels. Filaments
DEVRUE R[\JHQ GLVVROYHG LQ ZDWHU DQG
WKURZ RXW FDUERQ GLR[LGH IURP WKH ERG\

These animals can breathe through gills *LOOV RI D ¿VK
only in the water and not on the land.

5HVSLUDWLRQ WKURXJK OXQJV

$QLPDOV OLNH UHSWLOHV ELUGV DQG PDPPDOV EUHDWKH WKURXJK OXQJV /XQJV
are sac like structure present at either side of chest.

In human beings, well developed respiratory system is present. This system
LQFOXGHV QRVH QRVWULO ODU\Q[ SKDU\Q[ ZLQGSLSH EURQFKL EURQFKLROHV
alveoli, lungs, diaphragm, etc.

Nostril Pharynx

Larynx Bronchus
Windpipe Lungs

Respiratory system
$LU LV LQKDOHG WKURXJK WZR KROHV FRQWDLQHG LQ WKH QRVH FDOOHG nostrils.
Nostrils lead to the nasal cavity contained inside the nose. The nasal cavity
RSHQV WR SKDU\Q[

Pharynx LV WKH FRPPRQ SLSH IRU ERWK DLU DQG IRRG 7KH SKDU\Q[ RSHQV WR
ODU\Q[ Epiglottis EORFNV WKH HQWU\ RI IRRG WR WKH ODU\Q[ ,W OHWV RQO\ WKH DLU
HQWHU WR WKH ODU\Q[ )URP WKH ODU\Q[ DLU PRYHV WR WKH WUDFKHD ,W LV DOVR
called wind pipe. Trachea divides into two pipes. Each leads to right and
left side of the chest. These two pipes are called bronchi. Each bronchus
runs to each lung. The bronchus further divides into smaller pipes called
bronchioles.

Times' Crucial Science and Environment 211 Book 7

Each bronchiole further divides and re-divides into small pipes which end
DW DLU VDFV FDOOHG DOYHROL $ JURXS RI alveoli appear like a bunch of grapes.
Thus, a lung is like a sponge. Alveoli are surrounded by blood vessels.
%ORRG DEVRUEV R[\JHQ IURP WKH DOYHROL DQG LV FDUULHG WR WKH GLIIHUHQW SDUWV
RI WKH ERG\ 7KH FDUERQ GLR[LGH FDUULHG E\ WKH EORRG LV WKURZQ RXW WR WKH
DOYHROL 7KH FDUERQ GLR[LGH SDVVHV RXW WKURXJK WKH VDPH SDWK DV R[\JHQ
goes inside.

Lungs occupy the major part of thoracic cavity. This is bounded on the
sides by ribs and is separated from the abdominal cavity by a muscular
wall called diaphragm.

During inhalation, diaphragm moves down causing the thoracic cavity to
be bigger. This causes the lungs to swell and movement of air from outside.
'XULQJ H[KDODWLRQ GLDSKUDJP PRYHV XSZDUG FDXVLQJ WKH WKRUDFLF FDYLW\
to be smaller. This causes the lungs to be smaller and the air is forced
outside.

Activity 19.1 7R GHPRQVWUDWH WKH SURFHVV RI EUHDWKLQJ

Materials required
Bell jar, rubber sheet, two balloons, Y-tube, cork.
Procedure
Take a bell jar and tie a thin rubber sheet at the wide end as shown
LQ WKH ÀJXUH )L[ D EDOORRQ DW HDFK HQG RI < WXEH WKHQ À[ WKH WXEH DW
the mouth of the jar with a cork. The sheet represents the diaphragm
and the balloons represent the lungs. Push the rubber sheet upward
WKHQ SXOO LW GRZQZDUGV :KDW KDSSHQV"

Observation
When the rubber sheet is pulled downward, the space of the jar
LQFUHDVHV 7KLV FDXVHV WKH ÁRZ RI DLU LQWR WKH MDU DQG WKH EDOORRQV
JHW LQÁDWHG 7KLV UHSUHVHQWV LQKDODWLRQ

Times' Crucial Science and Environment 212 Book 7

When the rubber sheet is pushed upwards, the space of the jar
decreases. The air in the balloon is pushed outwards then the balloon
GHÁDWHV 7KLV UHSUHVHQWV H[KDODWLRQ

%UHDWKLQJ LQ 3ODQWV

Like animals, plants also breathe at night and day time. During day time,
SKRWRV\QWKHVLV DOVR RFFXUV 7KHUHIRUH R[\JHQ LV WKURZQ DW GD\ WLPH %XW
WKH WDNLQJ RI R[\JHQ GXULQJ EUHDWKLQJ RFFXUV DW ERWK QLJKW DQG GD\ WLPH

7KH H[FKDQJH RI WKH JDVHV RFFXUV WKURXJK Stomata
stomata of leaves, lenticles of the stem and
surfaces of the roots.

Stomata are small holes on the surface of the
leaves usually on the lower surface of leaves.
Stomata are surrounded by two specialized
bean-shaped cells known as guard cells. The
movement of the guard cells causes the opening
or closing of stomata.

Lenticles are oval shaped opening packed with loosely arranged cells. They
are present on the surface of stem.

2[\JHQ HQWHUV WKH SODQW ERG\ WKURXJK VWRPDWD DQG OHQWLFOHV &DUERQ
GLR[LGH FRPHV RXW IURP WKH SODQW ERG\ WKURXJK WKH VDPH RSHQLQJV

Differences between Breathing and Respiration

Breathing ZĞƐƉŝƌĂƟŽŶ

ϭ͘ /ƚ ŝƐ ƚŚĞ ƉƌŽĐĞƐƐ ŽĨ ŝŶŚĂůŝŶŐ ŽdžLJŐĞŶ ϭ͘ /ƚ ŝƐ ƚŚĞ ƉƌŽĐĞƐƐ ŽĨ ƌĞĂĐƟŽŶ ŽĨ ĨŽŽĚ

ĂŶĚ ĞdžŚĂůŝŶŐ ŽĨ ĐĂƌďŽŶ ĚŝŽdžŝĚĞ͘ ĂŶĚ ŽdžLJŐĞŶ ƚŽ ƉƌŽĚƵĐĞ ĞŶĞƌŐLJ͕ ǁĂƚĞƌ

ĂŶĚ ĐĂƌďŽŶ ĚŝŽdžŝĚĞ͘

Ϯ͘ /ƚ ƚĂŬĞƐ ƉůĂĐĞ ŽƵƚƐŝĚĞ ƚŚĞ ĐĞůů ƚŚƌŽƵŐŚ Ϯ͘ /ƚ ƚĂŬĞƐ ƉůĂĐĞ ŝŶ ƚŚĞ ŵŝƚŽĐŚŽŶĚƌŝĂ ŽĨ

ůƵŶŐƐ͕ ŐŝůůƐ͕ ƐƚŽŵĂƚĂ͕ ĞƚĐ͘ ĐĞůů͘

ϯ͘ /ƚ ŝƐ Ă ƉŚLJƐŝĐĂů ƉƌŽĐĞƐƐ͘ ϯ͘ /ƚ ŝƐ Ă ĐŚĞŵŝĐĂů ƉƌŽĐĞƐƐ͘

ϰ͘ ŶĞƌŐLJ ŝƐ ŶŽƚ ƌĞůĞĂƐĞĚ͘ ϰ͘ ŶĞƌŐLJ ŝƐ ƌĞůĞĂƐĞĚ͘

([FUHWLRQ

Various metabolic activities such as digestion, respiration, etc take place
in the body of living things. These activities cause the production of
YDULRXV W\SHV RI WR[LF VXEVWDQFHV LQ WKHLU ERG\ ,I WKH\ DUH DFFXPXODWHG
in large amount, they may harm our body. Hence, they should be thrown
outside from the body. The process of removing waste materials produced
by metabolic activities is called excretion.

Times' Crucial Science and Environment 213 Book 7

9DULRXV RUJDQV DUH LQYROYHG IRU WKH H[FUHWLRQ RI PHWDEROLF ZDVWHV 7KHVH
organs make a system named excretory system. $QLPDOV WKURZ WKH ZDVWH
VXEVWDQFHV OLNH XUHD FDUERQ GLR[LGH VDOWV DPPRQLD XULF DFLG HWF WKURXJK
H[FUHWLRQ SURFHVV

([FUHWLRQ LQ $QLPDOV

Unicellular animals like paramecium, amoeba, euglena, etc remove the
waste products from their body through body surface. In the same way
animals like sponges, coelenterates, etc remove their waste products
through body surface.
,Q ÁDWZRUPV WKHUH DUH VSHFLDO RUJDQV QDPHG ÁDPH FHOOV IRU WKH H[FUHWLRQ
of waste products. Earthworms have nephridia IRU H[FUHWLRQ The insects
OLNH EXWWHUÁ\ FRFNURDFK HWF KDYH malpighian bodies IRU H[FUHWLRQ
9HUWHEUDWHV KDYH ZHOO GHYHORSHG H[FUHWRU\ RUJDQV VXFK DV NLGQH\ VNLQ
lungs, liver, intestine, etc.

([FUHWLRQ LQ +XPDQ EHLQJV

Human beings have mainly kidney, lungs, skin, liver and intestine for
H[FUHWLRQ

Blood vessels

Kidney

Ureter

Excretory system Urinary bladder
Urethra
Times' Crucial Science and Environment 214
Book 7

.LGQH\ Kidneys

Kidneys are two bean shaped organs
located at the either side of the backbone.
Each kidney is made up of large number of
coiled tube like structures called nephrons.
1HSKURQV ÀOWHU WKH EORRG DQG WKURZ RXW
waste things from the body in the form of
urine. Urine passes from each kidney to
the urinary bladder through small pipes
originated from the kidney. These pipes
are called ureters. Urinary bladder is a bag
like structure which collects urine produced
from kidney.

When the urinary bladder is full, it contracts and the urine is passed out
through a small pipe called urethra.
Thus, kidney, ureter, urinary bladder and urethra make a system named
urinary system. This system removes the waste materials in the form of
XULQH 8ULQH FRQVLVWV RI PDLQO\ XUHD XULF DFLG VRPH H[FHVV VDOWV DQG ZDWHU

/XQJV

'XULQJ WKH SURFHVV RI UHVSLUDWLRQ SURFHVV R[\JHQ LV
XVHG DQG FDUERQ GLR[LGH DQG ZDWHU DUH SURGXFHG DV
ZDVWH SURGXFWV &DUERQ GLR[LGH LV UHPRYHG WKURXJK
lungs.

Lungs

6NLQ

6NLQ UHPRYHV ZDVWH PDWHULDOV OLNH XUHD VDOW H[FHVV
water, etc in the form of sweat.

/DUJH ,QWHVWLQH Skin

$OO WKH IRRG HDWHQ E\ XV FDQQRW EH GLJHVWHG
in our body. Some of the foods remain in
XQGLJHVWHG DQG XQDEVRUEHG IRUP 7KH H[FHVV
of water present in the food is absorbed by
large intestine and the unwanted materials
are collected in the rectum. These materials
are thrown out from the body through the
anus.

Large intestine

Times' Crucial Science and Environment 215 Book 7

/LYHU

/LYHU SURGXFHV ELOH %LOH LV SURGXFHG IURP EURNHQ 5%&V
Liver also produces urea and supplies to the kidney for
H[FUHWLRQ

([FUHWLRQ LQ 3ODQWV Liver

3ODQWV KDYH QR VSHFLDO RUJDQV IRU H[FUHWLRQ 3ODQWV SURGXFH FDUERQ GLR[LGH
(sCtoOm2a) taas. waste product during respiration. They throw CO2 through the

7KH H[FHVV ZDWHU SURGXFHG LQ WKH SODQW ERG\ LV HYDSRUDWHG WKURXJK OHDYHV
and aerial parts through transpiration.

7KH R[\JHQ JDV SURGXFHG GXULQJ SKRWRV\QWKHVLV LV WKURZQ WKURXJK VWRPDWD

Plants collect other waste product in the bark, dead wood and old leaves.
5HVLQV JXPV ODWH[ RLO HWF DUH VXFK ZDVWH SURGXFWV

EƵƚƌŝĞŶƚ ͗ Ă ƐƵďƐƚĂŶĐĞ ƚŚĂƚ ƉƌŽǀŝĚĞƐ ŶŽƵƌŝƐŚŵĞŶƚ͖ Ă ĐŽŵƉŽŶĞŶƚ ŽĨ ĨŽŽĚ
ŽŵƉůĞdž ͗ ĐŽŶƐŝƐƟŶŐ ŽĨ ŵĂŶLJ ĐŽŶŶĞĐƚĞĚ ƉĂƌƚƐ
WĂůĂƚĞ ͗ ƌŽŽĨ ŽĨ ŵŽƵƚŚ
^ĞĐƌĞƚĞ ͗ ƉƌŽĚƵĐĞ
ŶnjLJŵĞ ͗ Ă ƐƵďƐƚĂŶĐĞ ŝŶ ŽƌŐĂŶŝƐŵ͛Ɛ ďŽĚLJ ǁŚŝĐŚ ŚĞůƉ ĨŽƌ ĐŚĞŵŝĐĂů ƌĞĂĐƟŽŶ
>ĞŶƟĐĞů ͗ Ă ƌĂŝƐĞĚ ƉŽƌĞ ŝŶ ƐƚĞŵ ŽĨ ƉůĂŶƚ ƚŚĂƚ ĂůůŽǁƐ ĞdžĐŚĂŶŐĞ ŽĨ ŐĂƐ
hƌĞĂ ͗ Ă ŶŝƚƌŽŐĞŶ ĐŽŶƚĂŝŶŝŶŐ ƐƵďƐƚĂŶĐĞ ǁŚŝĐŚ ĐŽŵĞƐ ŽƵƚ ƚŚƌŽƵŐŚ ƵƌŝŶĞ
ŝůĞ ͗ Ă ďůƵŝƐŚ ĂůŬĂůŝŶĞ ŇƵŝĚ ǁŚŝĐŚ ŚĞůƉƐ ĨŽƌ ĚŝŐĞƐƟŽŶ
>ĂƚĞdž ͗ ŵŝůŬLJ ŇƵŝĚ ƉƌŽĚƵĐĞĚ ŝŶ ƉůĂŶƚƐ

0DLQ 3RLQWV WR 5HPHPEHU

1. The various activities which take place in the body of living things
to make them alive are called life processes.

$QDEROLVP LV VHW RI FKHPLFDO UHDFWLRQV WDNLQJ SODFH LQ WKH ERG\ RI
living things which form larger molecules from smaller molecules.

3. Catabolism is a set of chemical reactions in which smaller molecules
are formed by the break down of larger molecules.

'LJHVWLRQ LV WKH SURFHVV RI EUHDNLQJ GRZQ RI FRPSOH[ IRRG PDWHULDOV
into simpler and soluble form.

Times' Crucial Science and Environment 216 Book 7

0RXWK RHVRSKDJXV VWRPDFK VPDOO LQWHVWLQH ODUJH LQWHVWLQH
rectum, etc are parts of alimentary canal.

0RXWK VWRPDFK DQG VPDOO LQWHVWLQH DUH WKH SDUWV IRU WKH GLJHVWLRQ
of the food.

7. Villi of the small intestine are the place for the absorption of food.

%UHDWKLQJ LV WKH SURFHVV RI WDNLQJ LQ R[\JHQ DQG WKURZLQJ RXW
FDUERQ GLR[LGH

5HVSLUDWLRQ LV WKH SURFHVV LQ ZKLFK IRRG UHDFWV ZLWK R[\JHQ WR
produce energy.

6SLUDFOHV JLOOV OXQJV HWF DUH YDULRXV RUJDQV IRU EUHDWKLQJ LQ DQLPDOV

11.Plants breathe through stomata and lenticles.

([FUHWLRQ LV WKH SURFHVV RI UHPRYLQJ ZDVWH PDWHULDOV IURP WKH ERG\
of living things.

.LGQH\ VNLQ OXQJV OLYHU ODUJH LQWHVWLQH HWF DUH WKH H[FUHWRU\
organs in animals.

([HUFLVH

1. Choose the best alternative in each case.

D :KLFK RI WKH IROORZLQJ VXEVWDQFHV LV SURGXFHG GXULQJ UHVSLUDWLRQ"

L 6DOW LL &DUERQ GLR[LGH

LLL 8UHD LY 2[\JHQ

E :KDW LV WKH UHVSLUDWRU\ RUJDQ RI LQVHFWV"

i. Spiracles ii. Gills

iii. Bronchi iv. Lungs

F :KLFK RUJDQ LV XVHG E\ SODQWV IRU EUHDWKLQJ"

i. Leaf ii. Stomata

iii. Flower iv. Fruit

G :KDW LV WKH PDLQ FRQVWLWXHQW RI GLJHVWLYH MXLFH"

i. Bile ii. Vitamin

iii. Hormone iv. Enzyme

Times' Crucial Science and Environment 217 Book 7

H 7KH FRLOHG WXEH OLNH VWUXFWXUHV RI NLGQH\ WKDW ÀOWHU WKH EORRG DQG
produce urine are called

i. Ureters ii. Urethra

iii. Nephrons iv. Urinary bladder

2. Fill in the blanks with appropriate words.
a. Various………….are taking place in the body of living things.
E «««« LV WKH SURFHVV RI WDNLQJ LQ R[\JHQ
c. …………..is the site for absorption of digested food in human
being.
d. ……….and ……….. are the enzymes present in gastric juice.
H «««««EORFNV WKH HQWU\ RI IRRG WR WKH ODU\Q[
I ««« VHSDUDWHV WKUR[LF FDYLW\ IURP DEGRPLQDO FDYLW\
g. Plants breathe through …………and…………..
h. …………….is the process of removal of waste materials from the
body of living things.
i. ……………..are the small tubes which are present in the kidney

of human being.

3. Copy the correct statements. And correct the false statements.
a. Catabolism is set of chemical reactions in which smaller
molecules are formed from large molecules.

b. Ptyalin is the enzyme produced by gastric gland.

F $VVLPLODWLRQ LV WKH SURFHVV RI EUHDNLQJ GRZQ RI FRPSOH[ IRRG
materials into simpler and soluble forms.

G 2[\JHQ LV WDNHQ LQVLGH WKH ERG\ RI OLYLQJ WKLQJV E\ H[KDODWLRQ

e. The openings of tracheal tubes in the insects are called operculum.

I /DU\Q[ LV WKH FRPPRQ SLSH IRU ERWK IRRG DQG R[\JHQ

g. Plants carry out the process of breathing through stomata.

h. The process of removing waste materials from the body of living
WKLQJV LV FDOOHG H[FUHWLRQ

i. The small tubules present in the kidney are called malphigian
bodies.

j. Skin removes urea, salts, etc in the form of sweat.

Times' Crucial Science and Environment 218 Book 7

4. Pick out the odd words
a. Urethra, kidney, lung, ureter, urinary bladder
b. Heart, skin, kidney, liver, lung
c. Lungs, bronchus, alveoli, heart, trachea
G 0RXWK RHVRSKDJXV, stomach, small intestine, rectum, gills.

5. Answer these questions in brief.
D :KDW LV PHWDEROLVP" :KDW DUH YDULRXV W\SHV RI PHWDEROLVPV"
E :KDW LV FDWDEROLVP" *LYH VRPH H[DPSOHV
F :KDW LV GLJHVWLRQ" :KDW DUH WKH YDULRXV RUJDQV RI DOLPHQWDU\ FDQDO"
d. :KDW LV EUHDWKLQJ" 'LIIHUHQWLDWH EHWZHHQ EUHDWKLQJ DQG UHVSLUDWLRQ
H :KDW LV H[FUHWLRQ" :KDW DUH WKH YDULRXV H[FUHWRU\ VXEVWDQFHV"
I :KDW LV XULQDU\ EODGGHU"
J :KDW LV LQKDODWLRQ"
K :KDW DUH DOYHROL" :KDW DUH WKHLU IXQFWLRQV"
L +RZ GR XQLFHOOXODU DQLPDOV UHPRYH WKHLU ZDVWH PDWHULDOV"
M :KDW LV WUDQVSLUDWLRQ"

6. Draw the labelled diagrams of:
a. Digestive system of human being.
b. Urinary system.
F 5HVSLUDWRU\ V\VWHP RI KXPDQ EHLQJ

7. Label the following parts in the given diagram.

a

b
c

d

3URMHFW :RUN

0DNH D OLVW RI OLIH SURFHVVHV ZKLFK WDNH SODFH LQ \RXU ERG\ ZLWK
H[DPSOHV

Times' Crucial Science and Environment 219 Book 7

Chapter

20 / LIH & \FOH RI ) URJ

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗Ϯ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ƚĞůů ŵĞĂŶŝŶŐ ŽĨ ůŝĨĞ ĐLJĐůĞ͘
 ƚĞůů ƚŚĞ ǀĂƌŝŽƵƐ ƐƚĂŐĞƐ ŽĨ ůŝĨĞ ĐLJĐůĞ ŽĨ ĨƌŽŐ͘
 ƚĞůů ƚŚĞ ĨĞĂƚƵƌĞ ŽĨ ĞĂĐŚ ƐƚĂŐĞ ŽĨ ůŝĨĞ ĐLJĐůĞ ŽĨ ĨƌŽŐ͘

MIND OPENERS
 ,ĂǀĞ LJŽƵ ĞǀĞƌ ƐĞĞŶ ďĂďŝĞƐ ŽĨ ĨƌŽŐƐ͍
 tŚĂƚ ĂƌĞ ƚŚĞLJ ĐĂůůĞĚ͍
 ,Žǁ ĚŽ ĨƌŽŐƐ ƌĞƉƌŽĚƵĐĞ ŶĞǁ ďĂďŝĞƐ͍
 ĂŶ LJŽƵ ƐĂLJ ǀĂƌŝŽƵƐ ƐƚĂŐĞƐ ŽĨ ůŝĨĞ ĐLJĐůĞ ŽĨ ĨƌŽŐ͍ džƉůĂŝŶ͘

Introduction

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develop into adults passing through different stages. When the new young
ones become adult, they also reproduce new babies. Thus, the same process
continues. This process is called life cycle. Every organism has its own life
cycle. Every organism passes through various stages in its life cycle.

/LIH F\FOH RI IURJ Eggs

Life cycle of frog completes Adult frog
in three stages. They are:

i) Egg
ii) Tadpole
LLL $GXOW

Grown up tadpole Tadpole

Life cycle of frog

Times' Crucial Science and Environment 220 Book 7

Egg
$GXOW IHPDOH IURJ OD\V HJJV LQ ZDWHU :KHQ HJJV DUH ODLG PDOH IURJV GHSRVLW
sperms to them and eggs are fertilized. Eggs are joined together by a jelly
OLNH VOLSSHU\ VXEVWDQFH 7KLV PDNHV D FOXPS RI HJJV ÁRDWLQJ RQ WKH ZDWHU
It is called spawn. It protects the eggs from enemies. The egg begins with
a single cell. The single cell splits into many cells and embryo is formed.
9DULRXV RUJDQV DQG JLOOV EHJLQ WR GHYHORS LQ WKH HPEU\R DQG D ÀVK VKDSHG
tadpole is formed.
Tadpole
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weeks. It feeds on algae present in the water. The tadpoles have gills to
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legs develop, then the fore limbs grow. The tail becomes shorter. Lungs
begin to develop preparing for the frog for its life on the land.
Adult Frog
$IWHU DERXW ZHHNV RI WKH WDGSROH VWDJH D IXOO\ GHYHORSHG IURJ ZLWK OHJV
lungs will be developed. It is called adult frog. Due to the presence of the
lungs, they can breathe on the land. Therefore, they live mostly on the land.
The adult frogs feed on insects and worms. When they become mature, the
female frog lays the eggs and same process repeats. Thus, the life cycle of
frog completes.

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,ŝŶĚ ůŝŵď ͗ ĞŝƚŚĞƌ ŽĨ ƚǁŽ ďĂĐŬ ůŝŵďƐ
&ŽƌĞ ůŝŵď ͗ ĞŝƚŚĞƌ ŽĨ ƚǁŽ ĨƌŽŶƚ ůŝŵďƐ

0DLQ 3RLQWV WR 5HPHPEHU

$OO WKH RUJDQLVPV SDVV WKURXJK GLIIHUHQW VWDJHV LQ WKHLU OLIH F\FOH
2. Life cycle of frog completes in three stages: egg, tadpole and adult stage.
$ IHPDOH IURJ OD\V HJJV LQ ZDWHU
4. Eggs hatch into tadpoles after three weeks.
7DGSROHV DUH ÀVK VKDSHG ZLWK ELJ KHDG DQG ORQJ WDLO
6. Tadpoles develop into adult frogs after 6 weeks of the tadpole stage.
$GXOW IURJ KDV OHJV OXQJV DQG RWKHU RUJDQV OLNH H\HV PRXWK QHFN HWF

Times' Crucial Science and Environment 221 Book 7

([HUFLVH

1. Fill in the blanks with appropriate words.

D $ IURJ SDVVHV WKURXJK««««« DQG ««««« LQ LWV OLIH F\FOH

b. Female frog………..eggs in water.

c. Eggs of frogs are joined together by jelly like substance to
make………….

d. …………breathe through gills.

H $GXOW IURJV EUHDWKH WKURXJK«««««« RQ WKH ODQG

2. Copy the correct statements. And correct the false statements
if any.
a. Tadpoles develop from eggs after 21 days.
E $GXOW IURJ EUHDWKHV WKURXJK JLOOV
c. Eggs are fertilized after they are laid in the water.
d. The egg of frog begins with a single cell.

3. Give short answer.
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E :KDW LV VSDZQ" :KDW LV LWV PDLQ IXQFWLRQ
F :KDW LV WDGSROH" 'UDZ D WDGSROH RI IURJ
G +RZ GRHV D WDGSROH GHYHORS LQWR DQ DGXOW IURJ"
H ([SODLQ WKH VWUXFWXUH RI DGXOW IURJ

4. Draw life cycle of frog and label its important stages.

3URMHFW :RUN

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FKDUW SDSHU $OVR GHVFULEH WKH GLIIHUHQW VWDJHV

Times' Crucial Science and Environment 222 Book 7

Chapter

21 6 WUXFWXUH RI
WKH (DUWK

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϲ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ĚĞĮŶĞ ƌŽĐŬƐ͘
 ƚĞůů ƚŚĞ ƐƚƌƵĐƚƵƌĞ ĂŶĚ ƉŚLJƐŝĐĂů ƉƌŽƉĞƌƟĞƐ ŽĨ ƌŽĐŬƐ͘
 ƚĞůů ƚŚĞ ƚLJƉĞƐ ŽĨ ƌŽĐŬƐ ĂŶĚ ƚŚĞ ƵƐĞƐ ŽĨ ǀĂƌŝŽƵƐ ƚLJƉĞƐ ŽĨ ƌŽĐŬƐ͘
 ŝĚĞŶƟĨLJ ǀĂƌŝŽƵƐ ƚLJƉĞƐ ŽĨ ƌŽĐŬƐ ĨŽƵŶĚ ŝŶ ŽƵƌ ĐŽƵŶƚƌLJ͘

MIND OPENERS
 Ž LJŽƵ ŬŶŽǁ ǁŚĂƚ ƌŽĐŬ ŝƐ͍
 /Ɛ ůĂĚĚĞƌ ŽĨ LJŽƵƌ ŚŽƵƐĞ ƉĂǀĞĚ ǁŝƚŚ ŵĂƌďůĞ͍ /Ɛ ŵĂƌďůĞ ƌŽĐŬ͍
 ĂŶ LJŽƵ ƐĂLJ ƐŽŵĞ ƵƐĞƐ ŽĨ ƌŽĐŬƐ͍
 ,Žǁ ŵĂŶLJ ƚLJƉĞƐ ŽĨ ƌŽĐŬƐ ĚŽ LJŽƵ ŬŶŽǁ͍ ŝƐĐƵƐƐ͘

Introduction

The earth is only a living planet in the solar system. It has some features
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follows:

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ii) Water and minerals are available.
iii) The climatic conditions are suitable.
iv) There is suitable temperature.
v) Presence of ozone layer prevents the entry of ultraviolet rays to the

earth surface.
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HDUWK VXUIDFH LV FRYHUHG E\ WKH ZDWHU DQG DERXW LV FRYHUHG E\ WKH ODQG
The land surface contains soil, rocks and sand. The part of the crust under
the water may also contain rocks, soils, etc.
Rocks are hard solids which are composed of minerals and other substances.
5RFNV DUH IRXQG RQ WKH VXUIDFH DV ZHOO DV LQ WKH LQQHU SDUWV RI WKH HDUWK
Small pieces of the rocks are found in the soil also. Larger rocks are found
in the hills and mountains.

Times' Crucial Science and Environment 223 Book 7

When rocks break into smaller pieces, soil is formed. The rocks break into
smaller particles due to heat, water, chemicals, etc.
5RFNV DUH FRPSRVHG RI YDULRXV W\SHV RI HOHPHQWV 7KH PDLQ HOHPHQWV WKHLU
symbols and percentage in the rocks are presented below:

S. No. Elements Symbol Percentage

1 KdžLJŐĞŶ O ϰϲ͘ϲ

2 ^ŝůŝĐŽŶ ^ŝ Ϯϳ͘ϳ

3 ůƵŵŝŶŝƵŵ Al ϴ͘ϭ

4 /ƌŽŶ &Ğ ϱ͘Ϭ

5 ĂůĐŝƵŵ Ă ϯ͘ϲ

ϲ ^ŽĚŝƵŵ EĂ Ϯ͘ϴ

7 WŽƚĂƐƐŝƵŵ K Ϯ͘ϲ

8 DĂŐŶĞƐŝƵŵ DŐ Ϯ͘ϭ

9 KƚŚĞƌ ĞůĞŵĞŶƚƐ — ϭ͘ϱ

Total 100

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the above elements. These elements combine together to form minerals.
Thus, minerals are the elements or compounds which combine together to
form rocks.

7\SHV RI 5RFNV

2Q WKH EDVLV RI RULJLQ DQG IRUPDWLRQ WKH URFNV DUH FODVVLÀHG LQWR WKUHH W\SHV
a) Igneous rocks
b) Sedimentary rocks
F 0HWDPRUSKLF URFNV

Igneous Rocks
The rocks which are formed due to cooling of the magma inside or outside
the surface of the earth are called igneous rocks. The molten mass found
inside the earth is called magma. When the magma comes to the surface
of the earth, it is called lava. When the lava comes to the earth surface,
LW FRROV DQG VROLGLÀHV 7KH VROLG PDVV IRUPHG DIWHU WKH VROLGLÀFDWLRQ RI WKH
lava is called igneous rock. Igneous rocks do not contain fossils. It is of two
types.

a) Volcanic rock
b) Plutonic rock

Times' Crucial Science and Environment 224 Book 7

Volcanic Rocks

7KH URFNV ZKLFK DUH IRUPHG GXH WR VROLGLÀFDWLRQ RI WKH ODYD RQ WKH VXUIDFH
of the earth are called volcanic rocks. The magma of the internal part of the
earth comes out through weaker part during volcanic eruption. Volcanic
rocks have small crystals and their surface is glassy.

Basalt 3XPLFH 2EVLGLDQ

Examples: Basalt, pumice, obsidian, etc.

Plutonic Rocks

Sometimes the magma is unable to come out to the surface of the earth. It
comes near to the surface only. In this situation, the magma cools inside
the earth and forms the rock named plutonic rock.

3OXWRQLF URFNV DUH WKH URFNV ZKLFK DUH IRUPHG GXH WR VROLGLÀFDWLRQ RI PDJPD
inside the earth surface.

They have larger crystals. They are the hardest rocks.

*UDQLWH 'LRULWH 'XQLWH

Examples: Granite, diorite, peridiorite, dunite, etc.
Sedimentary Rocks

The break down of the materials on the earth surface takes place
continuously by weathering and erosion. The eroded or weathered particles
are carried by the agents like water, wind, rain, etc and are deposited to
bed of lakes, oceans or seas. They are deposited in the form of layers and
WKLV GHSRVLWLRQ SURFHVV FRQWLQXHV IRU D ORQJ WLPH $IWHU ORQJ WLPH WKH ORZHU
layers become harder due to high pressure of the upper layers and change
into rocks. These rocks are called sedimentary rocks.

Times' Crucial Science and Environment 225 Book 7

The rocks which are formed due to deposition of the particles at the bed of
lake, sea or ocean in the form of layers are called sedimentary rocks.

These rocks are softer than igneous rocks. They contain many layers. In
the middle of these layers, fossils of animals and plants are found. Some
H[DPSOHV RI VHGLPHQWDU\ URFNV DUH FRQJORPHUDWH VDQGVWRQH OLPHVWRQH
shale, etc.
Conglomerate

It is formed from pebbles and sand cemented
together by silica. It is also called concrete
rock.

It is found near the rivers or stream.

Sandstone

It is formed by sand particles joined together
by silica or mud. It may be hard or soft.

Shale

Silt has smaller soil particles than the
VDQG :KHUHDV WKH FOD\ KDV WKH ÀQHVW
soil particles. The rock formed by the
combination of silt and clay is shale. It is
black in colour. It is soft type of rock.

Limestone

Bodies of some aquatic animals are covered
by shells. These shells are hard and made
IURP FDOFLXP FRPSRXQGV $IWHU WKHLU GHDWK
the shells and bones remain at the bottom
of sea and take the form of stones after long
time. They are called limestones.

Limestones contain the mineral lime (CaO).
Fossils are also contained in such rocks.

Metamorphic Rocks

Heat and pressure cause chemical and physical change in the minerals of
rocks. Thus, new types of rocks are formed from igneous and sedimentary
rocks due to heat and pressure. These new types of rocks are called
metamorphic rocks.

Times' Crucial Science and Environment 226 Book 7

The rocks which are formed from sedimentary and igneous rocks due to the
change caused by heat and pressure are called metamorphic rocks.

It takes millions of years to form metamorphic rock from sedimentary or
igneous rocks.

6RPH H[DPSOHV RI PHWDPRUSKLF URFNV DUH DV IROORZV

Metamorphic Rocks Changed from (original)
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'ƌĂƉŚŝƚĞ ŽĂů ;ƐĞĚŝŵĞŶƚĂƌLJͿ
ŝĂŵŽŶĚ 'ƌĂƉŚŝƚĞ ;ŵĞƚĂŵŽƌƉŚŝĐͿ
^ůĂƚĞ ^ŚĂůĞ ;ƐĞĚŝŵĞŶƚĂƌLJͿ
'ŶĞŝƐƐ 'ƌĂŶŝƚĞ ;ŝŐŶĞŽƵƐͿ
^ĐŚŝƐƚ ^ŚĂůĞ ;ƐĞĚŝŵĞŶƚĂƌLJ ƌŽĐŬͿ
YƵĂƌnjŝƚĞ ^ŝůŝĐĂ ;ƐĞĚŝŵĞŶƚĂƌLJ ƌŽĐŬͿ

Activity 21.1 7R FROOHFW DQG VWXG\ GL൵HUHQW NLQGV RI URFNV

Collect various types of rocks from your surroundings. Name them
and classify them as sedimentary, igneous and metamorphic rocks.

Sn. Sedimentary Igneous Metamorphic

ϭ͘

Ϯ͘

ϯ͘

8VHV RI 5RFNV

D 5RFNV DUH XVHG LQ WKH FRQVWUXFWLRQ RI EXLOGLQJ EULGJHV URDGV GDPV
etc.

E 5RFNV DUH EURNHQ WR JUDYHOV *UDYHOV DUH DOVR XVHG LQ WKH FRQVWUXFWLRQ
of concrete roofs, roads, etc.

F 0DUEOHV DUH XVHG IRU ÁRRULQJ DQG GHFRUDWLRQV
d) Granite is used to make temples.
H 5RFNV DUH XVHG WR PDNH VWDWXHV LGROV HWF
I 6ODWHV DUH XVHG IRU URRÀQJ SXUSRVH
g) Slates are also used by children for writing purpose.

Times' Crucial Science and Environment 227 Book 7

h) Geologists use the rocks for the study about the origin and
development of living things.

i) Coal is a sedimentary rock. It is used as fuel.

0DLQ URFNV RI 1HSDO

,Q RXU FRXQWU\ YDULRXV W\SHV RI URFNV DUH SUHVHQW 0DLQO\ WKHUH DUH
sedimentary and metamorphic rocks. Igneous rocks are rarely found. Some
of the important sedimentary rocks found in our country are: conglomerate,
silica, sandstone, shale, limestone, coal, etc. They are found as the main part
of hills and mountains. They are found in the rivers, streams, too. Some of the
metamorphic rocks found in our country are slate, quartzite, marble, etc.

6ODWH 4XDUW]LWH 0DUEOH

6ODWH LV IRXQG LQ 'RODNKD GLVWULFW 0DUEOH LV IRXQG LQ *RGDZDUL /DOLWSXU

DŝŶĞƌĂů ͗ Ă ƐŽůŝĚ ŶĂƚƵƌĂůůLJ ŽĐĐƵƌƌŝŶŐ ŝŶŽƌŐĂŶŝĐ ƐƵďƐƚĂŶĐĞ
^ŽůŝĚŝĮĐĂƟŽŶ ͗ ƉƌŽĐĞƐƐ ŽĨ ĐŚĂŶŐŝŶŐ ŝŶƚŽ ƐŽůŝĚ
YƵĂƌƚnjŝƚĞ ͗ ĂŶ ĞdžƚƌĞŵĞůLJ ĐŽŵƉĂĐƚ Žƌ ŚĂƌĚ ƌŽĐŬƐ ĐŽŶƐŝƐƟŶŐ ŽĨ ƋƵĂƌƚnj
/ĚŽů ͗ ŝŵĂŐĞ Žƌ ƌĞƉƌĞƐĞŶƚĂƟŽŶ ŽĨ ŐŽĚ͖ ƐƚĂƚƵĞ
^ŚĂůĞ ͗ Ă ƌŽĐŬ ŵĂĚĞ ĨƌŽŵ ĐůĂLJ

0DLQ 3RLQWV WR 5HPHPEHU

1. The earth is a living planet where all conditions required for the
H[LVWHQFH RI OLIH DUH DYDLODEOH

5RFNV DUH KDUG VROLGV ZKLFK DUH FRPSRVHG RI PLQHUDOV DQG RWKHU
substances.

0LQHUDOV DUH WKH HOHPHQWV RU FRPSRXQGV ZKLFK FRPELQH WRJHWKHU
to form rocks.

4. Igneous rocks are the rocks which are formed from the cooling of
magma inside or outside of the earth.

Times' Crucial Science and Environment 228 Book 7

9ROFDQLF URFNV DUH WKH URFNV ZKLFK DUH IRUPHG GXH WR VROLGLÀFDWLRQ
of lava on the surface of the earth.

3OXWRQLF URFNV DUH WKH URFNV ZKLFK DUH IRUPHG GXH WR VROLGLÀFDWLRQ
of magma inside of the earth.

7. Sedimentary rocks are the rocks which are formed due to deposition
of particles at the bed of lake, sea or oceans in the form of layers.

0HWDPRUSKLF URFNV DUH WKH URFNV ZKLFK DUH IRUPHG IURP VHGLPHQWDU\
and igneous rocks caused by heat and pressure.

9. Sandstone, limestone, shale, slates, marble conglomerate, silica,
etc are the main rocks found in our country.

([HUFLVH

1. Choose the best alternative in each case.

D :KLFK LV WKH PRVW DEXQGDQW HOHPHQW SUHVHQW LQ WKH HDUWK FUXVW"

i. Silicon ii. Iron

LLL $OXPLQLXP LY 2[\JHQ

b. The molten mass found inside the earth crust is called

L /DYD LL 0DJPD

iii. Volcano iv. Plutonic rock

F :KLFK RI WKH IROORZLQJ URFNV FDQQRW KDYH IRVVLOV"

i. Obsidian ii. Sandstone

iii. Limestone iv. Conglomerate

G :KLFK RI WKH IROORZLQJ URFNV LV XVHG WR PDQXIDFWXUH FHPHQW"

i. Sandstone ii. Granite

iii. Slate iv. Limestone

H :KLFK RI WKH IROORZLQJ LV QRW D PHWDPRUSKLF URFN"

L 0DUEOH LL 3XPLFH

iii. Gneiss iv. Diamond

2. Copy the correct statement and correct the false statements if any.

D 5RFNV DUH IRUPHG IURP RQH RU PDQ\ PLQHUDOV

E 3OXWRQLF URFNV DUH IRUPHG GXH WR VROLGLÀFDWLRQ RI ODYD RQ WKH
earth surface.

c. Granite, sandstone and basalt are sedimentary rocks.

Times' Crucial Science and Environment 229 Book 7

d. Igneous rocks contain fossils.

e. Shale is formed from clay and silt.

I 0HWDPRUSKLF URFNV DUH IRUPHG IURP FKDQJH RI VHGLPHQWDU\ DQG
igneous rocks caused by heat and pressure.

J 0DUEOH LV FKDQJHG IRUP RI OLPHVWRQH

3. Match the following

0DUEOH *UDQLWH

Graphite Limestone

Gneiss Shale

Quartzite Coal

Slate Silica

4. Answer in short.
D :KDW LV URFN" :KDW DUH WKHLU YDULRXV W\SHV"
E :KDW LV PLQHUDO"
F :KDW LV LJQHRXV URFN" *LYH VRPH H[DPSOHV
G :KDW LV SOXWRQLF URFN" *LYH VRPH H[DPSOHV
H :KDW LV YROFDQLF URFN" *LYH VRPH H[DPSOHV
I :KDW LV VHGLPHQWDU\ URFN" *LYH VRPH H[DPSOHV
J :KDW LV PHWDPRUSKLF URFN" *LYH VRPH H[DPSOHV

5. Write short notes on:
limestone, slate, conglomerate

6. Answer these questions in detail:
D +RZ DUH VHGLPHQWDU\ URFNV IRUPHG"
E :KDW DUH WKH YDULRXV XVHV RI URFNV"
F +RZ LV OLIH SRVVLEOH RQ WKH HDUWK"
G ([SODLQ WKH YDULRXV W\SHV RI URFNV IRXQG LQ 1HSDO

3URMHFW :RUN

2UJDQL]H D RQH GD\ H[FXUVLRQ WR D ODQGVOLGH KLW DUHD RU WKH ULYHUVLGH WR
study different kinds of rocks. Collect samples, draw their diagrams and
write their name and type.

Times' Crucial Science and Environment 230 Book 7

Chapter

22 : HDWKHU DQG
&OLPDWH

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϲ

OBJECTIVES

At the end of the lesson, the students will be able to :
 ŝŶƚƌŽĚƵĐĞ ĐůŽƵĚ͕ ƐŶŽǁ ĂŶĚ ĨƌŽƐƚ͘
 ĞdžƉůĂŝŶ ƚŚĞ ůĂLJĞƌƐ ŽĨ ĂƚŵŽƐƉŚĞƌĞ͘
 ĞdžƉůĂŝŶ ƚŚĞ ƐƉĞĞĚ͕ ĐĂƵƐĞƐ ĂŶĚ ĞīĞĐƚƐ ŽĨ ǁŝŶĚ͘
 ĞdžƉůĂŝŶ ƚŚĞ ƐŝŵƉůĞ ƚĞĐŚŶŝƋƵĞƐ ŽĨ ǁĞĂƚŚĞƌ ĨŽƌĞĐĂƐƟŶŐ͘
 ŝŶƚƌŽĚƵĐĞ ƚŚĞ ĚĞǀŝĐĞƐ ƵƐĞĚ ƚŽ ŵĞĂƐƵƌĞ ƚŚĞ ĚŝīĞƌĞŶƚ ĐŽŵƉŽŶĞŶƚƐ ŽĨ

ǁĞĂƚŚĞƌ͘

MIND OPENERS
 ,ĂǀĞ LJŽƵ ĞǀĞƌ ƐĞĞŶ ƐŶŽǁ ͍ ,Žǁ ĚŽĞƐ ƚŚĞ ƐŶŽǁ ĨĂůů ŽĐĐƵƌ ͍
 ,Žǁ ŝƐ ƚŚĞ ǁĞĂƚŚĞƌ ĚƵƌŝŶŐ ƚŚĞ ƐŶŽǁ ĨĂůů ͍
 tŚĂƚ ĐĂƵƐĞƐ ƚŚĞ ĐŚĂŶŐĞƐ ŝŶ ǁĞĂƚŚĞƌ ͍
 ĂŶ LJŽƵ ĨŽƌĞĐĂƐƚ ǁĞĂƚŚĞƌ ͍ ŝƐĐƵƐƐ͘

Introduction
:HDWKHU

Weather is the sum of all processes occurring in a particular area at a
particular time. In general, weather refers to a day-to-day temperature,
rainfall, humidity, sunshine, etc. The weather occurs due to the differences
in temperature and moisture of different places. The weather includes the
sun, wind, cloud, rain, snow, frost, etc.

Cloud

$OO WKH VRXUFHV RI ZDWHU OLNH ULYHU SRQG ODNH RFHDQ HWF HYDSRUDWH DW DQ\
temperature. The evaporation of these sources releases large amount of
water vapours in the atmosphere. When the temperature of the atmosphere
EHFRPHV ORZ WKH H[FHVV RI ZDWHU YDSRXUV LQ WKH DLU FRQGHQVH DQG IRUP
cloud. The clouds can be white, grey, dark or brown in colour. If the cloud
spreads in the sky, it blocks the sunlight and the weather becomes cloudy.

7\SHV RI &ORXGV

The clouds can be divided into four main types - cirrus, stratus, cumulus
and nimbus.

Times' Crucial Science and Environment 231 Book 7

a. Cirrus Clouds
The cirrus cloud consists of tiny ice crystals
and looks like thin feathers in the sky.
These clouds are formed only at high
altitudes about 5 to 13km from the surface
of the earth.
The cirrus clouds are generally white in
colour and indicate the fair weather.

b. Stratus Clouds
It is generally grey in colour and has layers.
It can cover most or whole of the sky and
obstruct the sunlight.
The stratus cloud is associated with stormy
weather.

c. Cumulus Clouds
Cumulus is a puffy cloud and looks like a
large mass of cotton. It may be very thick. It
is usually seen in afternoon and disappears
in the evening.
Cumulus cloud is associated with both
JRRG DQG EDG ZHDWKHUV $ IRUP RI FXPXOXV
cloud, which is very large and black, can
cause heavy rainfall and thunderstorm.
Such cloud is called cumulus congestus.
But cumulus cloud indicates fair weather.

d. Nimbus Clouds
It is a grey and dark coloured cloud and
develops vertically upwards.
The clouds that produce heavy
thunderstorm in summer are the collective
form of cumulus and nimbus clouds called
cumulonimbus.
The clouds are associated with different kinds of rainfalls, e.g. light, heavy,
UDLQIDOO ZLWK KDLOVWRQHV HWF *HQHUDOO\ GLIIHUHQW NLQGV RI FORXGV JHW PL[HG
in the sky and give a different appearance.

6QRZ

,I WKH WHPSHUDWXUH RI WKH FORXG IDOOV EHORZ ƒ& WKH ZDWHU YDSRXUV SUHVHQW
in the cloud directly change into solid state. The solid state of water
YDSRXU WKXV IRUPHG LV FDOOHG VQRZ 6QRZ LV YHU\ WKLQ ZKLWH DQG ÁXII\ LQ

Times' Crucial Science and Environment 232 Book 7

appearance. The snow fall occurs as the falling of
very small pieces of cotton balls continuously.

During snow formation, the liquid rain drops are
not formed. The snow is deposited on the ground,
grass or the leaves of plants giving a white
appearance. During very cold weather, large
amount of snow may be deposited all around including the roads, airports,
HWF ,W REVWUXFWV WKH WUDQVSRUWDWLRQ DQG PDNHV WKH OLIH GLIÀFXOW

,Q RXU FRXQWU\ WKH KLJK PRXQWDLQV VXFK DV 0W (YHUHVW 0W 0DFKKDSXFKKUH
0W .DQFKDQMDQJKD HWF DUH DOZD\V FRYHUHG ZLWK VQRZ

Frost

Frost is the solid deposition of water vapour from
the air saturated with water vapours. It is formed
when solid substances are cooled to below the
freezing point of water. If the solid surfaces on the
earth (eg, grass leaves, stones, trees, etc) become
very cold due to cold weather, the water vapour
which is in contact with these surfaces turns into
thin white mass, known as frost. The frost consists of spicules of ice which
grow out from the solid surface.

The frost can be formed during the winter season. The frost can cause
economic damage by destroying the crop plants and fruits.

&OLPDWH

The average atmospheric conditions of a particular place over a long period
of time is called climate. For the climatic average, a minimum period of 35
years is needed. The climate of a particular place is determined with the
help of systematic observation, recording and analysis of various factors
such as temperature rainfall, wind, cloud, sunshine, humidity, atmospheric
pressure, etc.

The climate can be of various types: tropical climate, sub-tropical climate,
temperate climate, alpine climate, tundra climate, etc. In Nepal, there are
different climates in different geographical regions. They are:

Terai region: Tropical climate,

Hilly region: Subtropical and temperate,

+LPDOD\DQ UHJLRQ $OSLQH FOLPDWH

Times' Crucial Science and Environment 233 Book 7

There are separate branches of science to study the weather and climate.
0HWHRURORJ\ LV WKH EUDQFK RI VFLHQFH WKDW GHDOV ZLWK ZHDWKHU ZKHUHDV
climatology is the branch of science that deals with climate.

Differences between weather and climate

Weather Climate

ϭ͘ /ƚ ŝƐ ƚŚĞ ĚĂLJͲƚŽͲĚĂLJ ĐŽŶĚŝƟŽŶ ŽĨ ƚŚĞ ϭ͘ /ƚ ŝƐ ƚŚĞ ĂǀĞƌĂŐĞ ĐŽŶĚŝƟŽŶ ŽĨ ǁĞĂƚŚĞƌ

ĂƚŵŽƐƉŚĞƌĞ͘ ĨŽƌ Ă ůŽŶŐ ƟŵĞ͘

Ϯ͘ /ƚ ŝƐ ĚĞƚĞƌŵŝŶĞĚ ďLJ ƚŚĞ ĞůĞŵĞŶƚƐ ƐƵĐŚ Ϯ͘ /ƚ ŝƐ ĚĞƚĞƌŵŝŶĞĚ ďLJ ƚŚĞ ĂǀĞƌĂŐĞ

ĂƐ ƚĞŵƉĞƌĂƚƵƌĞ͕ ƌĂŝŶĨĂůů͕ ŚƵŵŝĚŝƚLJ͕ ƐƚĂƟƐƟĐĂů ƉƌŽďĂďŝůŝƟĞƐ ŽĨ Ăůů ƚŚĞ

ǁŝŶĚ͕ ĞƚĐ͘ ĞůĞŵĞŶƚƐ ŽĨ ǁĞĂƚŚĞƌ ŽĨ Ă ůĂƌŐĞ ĂƌĞĂ͘

ϯ͘ /ƚ ĂīĞĐƚƐ ĚĂŝůLJ ůŝĨĞ͘ ϯ͘ /ƚ ĚĞƚĞƌŵŝŶĞƐ ƚŚĞ ůŝĨĞ ƐƚLJůĞ ŽĨ ƉĞŽƉůĞ͘

ϰ͘ /ƚ ĐĂŶ ďĞ ƉƌĞĚŝĐƚĞĚ Žƌ ĨŽƌĞĐĂƐƚ͘ ϰ͘ /ƚ ŝƐ ĂĐĐĞƉƚĞĚ ĂƐ Ă ƐĞĂƐŽŶĂů Žƌ ĂŶŶƵĂů
ŶĂƚƵƌĂů ƉŚĞŶŽŵĞŶŽŶ͘

$WPRVSKHUH ExosSKHrH

7KH HDUWK LV VXUURXQGHG E\ D PL[WXUH RI VHYHUDO JDVHV 7KHVH JDVHV
together are known as air. The layers of air around the earth is known as
DWPRVSKHUH 0RVW RI WKH DWPRVSKHUH LV ORFDWHG FORVH WR WKH HDUWK·V VXUIDFH
7KH DWPRVSKHUH H[LVWV LQ ÀYH GLIIHUHQW OD\HUV

They are:

1. Troposphere

2. Stratosphere

0HVRVSKHUH

4. Thermosphere

([RVSKHUH

1. Troposphere

The layer of the atmosphere closest to the

earth is called troposphere. 5DLQ KDLO

dew and snow arise from this layer. This

OD\HU H[WHQGV XS WR WKH KHLJKW RI DERXW Layers of atmosphere
16 kilometers from the surface of the

HDUWK 7KH PDLQ JDVHV SUHVHQW LQ WURSRVSKHUH DUH QLWURJHQ R[\JHQ FDUERQ

GLR[LGH ZDWHU YDSRXU GXVW HWF 7KH WHPSHUDWXUH RI WKH WURSRVSKHUH

decreases with height.

Times' Crucial Science and Environment 234 Book 7

2. Stratosphere

The layer of the atmosphere that lies above the troposphere is known as
stratosphere. 7KLV OD\HU H[WHQGV EHWZHHQ WKH KHLJKW RI NP IURP WKH
surface of the earth. This layer contains an important gas called ozone. The
ozone gas forms a layer and is known as ozonosphere or ozone layer. The
ozone layer absorbs the sun’s harmful ultraviolet radiations and protects
the living beings on the earth. So, this layer is called protective layer.

3. Mesosphere

The layer of atmosphere that lies above the stratosphere is known as
mesosphere. 7KLV OD\HU OLHV EHWZHHQ WKH KHLJKW RI NLORPHWHUV IURP
the surface of the earth. It is the coldest layer of atmosphere.

4. Thermosphere

The layer of atmosphere that lies above the mesosphere is known as
thermosphere. 7KLV OD\HU H[WHQGV EHWZHHQ NLORPHWHUV IURP WKH
surface of the earth. It is a very thin layer of atmosphere. It contains
nitrogen,hydrogen, helium, etc.

5. Exosphere

,W LV WKH RXWHUPRVW OD\HU RI DWPRVSKHUH 7KLV OD\HU H[WHQGV EHWZHHQ WKH WRS
RI WKHUPRVSKHUH WR NLORPHWHUV IURP WKH VXUIDFH RI WKH HDUWK 7KH
main gases of this layer are hydrogen and helium. This layer has very few
gas molecules which can escape into the space.

:LQG

:LQG LV WKH ÁRZ RI JDVHV RQ D ODUJH VFDOH Anemometer
The wind consists of bulk movement of
air. We cannot see the wind but we can
feel it. The wind is named according to
the strength and direction in which it
LV EORZLQJ $ VKRUW EXUVW RI KLJK VSHHG
wind is known as gust. $ VWURQJ ZLQG
that blows for around one minute is
known as squall. But the long duration
winds have various names on the
basis of their average strength. They
are breeze, gale, storm, hurricane and
typhoon.

We can measure the direction and speed of wind. The direction of the wind
is measured by using wind vanes whereas the speed is measured by using
anemometer.

Times' Crucial Science and Environment 235 Book 7

$ ZLQG YDQH FRQVLVWV RI D URWDWRU LQGLFDWRU ZKLFK VKRZV WKH GLUHFWLRQ RI WKH wind.
Different kinds of anemometers are available to measure the velocity of
ZLQG 7KH\ DUH FXS ZLQGPLOO KRW ZLUH VRQLF DQHPRPHWHU HWF $ VLPSOH
type of anemometer is a cup anemometer. It consists of four hemispherical
cups each mounted on one end of four horizontal arms, which in turn are
mounted at equal angles to each other on a vertical shaft. 7KH DLU ÁRZ QHDUE\
the cups in any direction turns the cups in a manner that is proportional
to the wind speed. Thus, the average speed to the wind is determined by
counting the turns of the cups over a set time period.

Causes of wind
Wind is caused due to the difference in atmospheric pressure of two places.
The difference in atmospheric pressure may arise due to the unequal
heating of these places by the sun. The hotter place has low atmospheric
pressure near it because the air becomes light due to heat and rises up.
But, the colder place has more pressure. Hence, the air from more pressure
moves towards the area having low pressure and causes wind.

Effects of wind
Wind at normal speed is useful. It can run windmill. It helps to maintain
the levels of different gases in the atmosphere. The land breeze (a kind
of slow and cool wind) and sea breeze help to keep the atmosphere of the
coastal areas pleasant.

Some forms of wind such as storm, hurricane, etc are destructive. They can
uproot the trees, destroy the houses and spoil other properties. They can
take lives of people as well as other animals.
Weather Forecasting
Weather forecasting is the practice of predicting the state of atmosphere
for a future time and for a given location. The weather forecasting is
mainly based upon the changes in atmospheric pressure, present weather
conditions and sky condition.

Times' Crucial Science and Environment 236 Book 7

The weather forecasting is the science of predicting the future weather
conditions.
It can be done by using different techniques such as persistence, use of
thermometer, use of barometer, looking at the sky, etc.

One of the simplest method of weather forecasting is the prediction of
conditions of tomorrow based on today’s conditions. Such method is called
persistence. If the days are sunny for past few days, it can easily be said
that tomorrow and few other days will be sunny.

Weather can be forecasted by looking at the sky as well. If there is no
cloud in the sky and the sun is shining, the weather will be fair in the near
future. Similarly, thickening of the cloud in the sky indicates the rainfall
LQ WKH QHDU IXWXUH $ IRJ LQ WKH PRUQLQJ PD\ LQGLFDWH D IDLU GD\ DQG VR RQ

&RPSRQHQWV RI ZHDWKHU DQG WKHLU PHDVXUHPHQW

The natural events or processes that affect the condition of atmosphere
are called components of weather. Following are the major components of
weather:

7HPSHUDWXUH 5DLQIDOO +XPLGLW\

$WPRVSKHULF SUHVVXUH :LQG

We measure these components in the following ways:

Temperature

The degree of hotness or coldness of a body is called $B $%
temperature. We record temperature with the help
of different types of thermometers. The temperature
of the atmosphere is measured with the help of
PD[LPXP PLQLPXP WKHUPRPHWHU

7KLV WKHUPRPHWHU LV XVHG WR PHDVXUH WKH PD[LPXP 0D[ 0LQ
and minimum temperature of a day. It is made of a
U- shaped glass tube having two bulbs (one bulb at
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WKH HQGV DUH ÀOOHG ZLWK DOFRKRO $PRQJ WKH WZR EXOEV
RQH LV ODEHOOHG DV $ DQG WKH RWKHU DV % 7KH EXOE $
LV FRPSOHWHO\ ÀOOHG EXW WKH EXOE % KDV VRPH HPSW\
space. Each tube has a steel pointer just above the
mercury level. Scales are marked on both the tubes.

When the temperature of the surrounding increases, 0D[LPXP PLQLPXP
WKHUPRPHWHU
the alcohol in bulb $ H[SDQGV DQG WKH PHUFXU\ LV

Times' Crucial Science and Environment 237 Book 7

pushed downward, which lifts the pointer upward in another tube. The
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WKH WHPSHUDWXUH RI DLU GHFUHDVHV WKH DOFRKRO LQ EXOE $ FRQWUDFWV DQG WKH
mercury rises in this bulb. The rise in mercury level lifts the pointer to
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temperatures of a day are recorded.
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above the mercury level with the help of a magnet.

Rainfall
When the cloud is cooled, it turns into water droplets. The small droplets
then combine to form bigger and heavier drops and fall in
the form of rain. The rainfall can occur in a particular place
for a very short to a long duration. Sometimes, it rains
nonstop for some days.
The amount of rainfall in a particular place is measured
with an instrument called rain gauge. $ UDLQ JDXJH
FRQVLVWV RI D PHWDOOLF F\OLQGHU ZLWK D PHWDO IXQQHO RI
inch diameter. It leads to a small bottle shaped container.
To measure the amount of rainfall, the rain gauge is kept in
an open place above the ground for 24 hours of a day. Then
the measurement of rainfall is done by removing the funnel Rain gauge
and pouring the rain water into a graduated cylinder of 1/2 inch diameter.

Pressure Hg pressure equal Vacuum
The layer of air around the to air pressure
earth is called atmosphere. The 760 mm
pressure due to the atmosphere is Atmospheric Mercury (Hg)
called atmospheric pressure. The pressure
atmospheric pressure is measured
by using a barometer. The pressure Barometer
varies from place to place and from
time to time.
$ mercury barometer is commonly
used to measure atmospheric
pressure. It consists of about 1
metre long glass tube with one
open end. The open end is dipped in
mercury contained in a container.
The glass tube has a mercury

Times' Crucial Science and Environment 238 Book 7

column. The height of the mercury column in the glass tube determines
the atmospheric pressure at a particular place. The height of the mercury
column is different at different places.
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PP FP ,W PHDQV WKDW WKH DWPRVSKHULF SUHVVXUH DW WKH VHD OHYHO LV
mm of Hg.

Humidity Hygrometer
The amount of water vapour present in the air is
called humidity. It is one of the main factors for
climate and weather change.
The relative humidity is measured by using a
K\JURPHWHU ,W LV H[SUHVVHG LQ SHUFHQWDJH

,ƵŵŝĚŝƚLJ ͗ ĂŵŽƵŶƚ ŽĨ ǁĂƚĞƌ ǀĂƉŽƵƌ ƉƌĞƐĞŶƚ ŝŶ Ăŝƌ
&Ăŝƌ ͗ ŵŽĚĞƌĂƚĞ Žƌ ŶĞƵƚƌĂů
ĞƉŽƐŝƚĞĚ ͗ ĐŽůůĞĐƚĞĚ
^ƉŝĐƵůĞƐ ͗ ŵŝŶƵƚĞ ƐŚĂƌƉ ƉŽŝŶƚĞĚ ŽďũĞĐƚƐ
,ƵƌƌŝĐĂŶĞ ͗ ǁŝŶĚ ǁŝƚŚ ŚŝŐŚ ƐƉĞĞĚ
dLJƉŚŽŽŶ ͗ ĨĂƐƚ ŵŽǀŝŶŐ ǁŝŶĚ ŝŶ ƚƌŽƉŝĐĂů ƌĞŐŝŽŶ
ŽĂƐƚĂů ƌĞŐŝŽŶ ͗ ĂƌĞĂ ŶĞĂƌ ŽĐĞĂŶ

0DLQ 3RLQWV WR 5HPHPEHU

1. Weather is the sum of all processes occurring in a particular area
at a particular time.

2. Cloud is a condensed form of large amount of water vapours which
forms white, grey or dark appearance in the sky.

3. The clouds can be divided into four main types- cirrus, stratus,
nimbus and cumulus.

7KH YHU\ WKLQ ZKLWH DQG ÁXII\ VROLG IRUP RI ZDWHU ZKLFK LV IRUPHG GXH
WR WKH GHFUHDVH RI WKH WHPSHUDWXUH RI FORXG EHORZ ƒ& LV FDOOHG VQRZ

5. Frost is the solid deposition of water vapour from the air saturated
with water vapours.

6. The average atmospheric conditions of a particular place over a
long period of time is called climate.

Times' Crucial Science and Environment 239 Book 7

7KH DWPRVSKHUH FDQ EH GLYLGHG LQWR ÀYH GLIIHUHQW OD\HUV WURSRVSKHUH
VWUDWRVSKHUH PHVRVSKHUH WKHUPRVSKHUH DQG H[RVSKHUH

8. Weather forecasting is the practice of predicting the state of
atmosphere for a future time and for a given location.

([HUFLVH

1. Choose the best alternative in each case.

D :KLFK FORXG ORRNV OLNH WKLQ IHDWKHUV LQ WKH VN\"

i. Cirrus ii. Stratus

iii. Cumulus iv. Nimbus

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i. Tropical ii. Sub-tropical

LLL 7HPSHUDWH LY $OSLQH

F :KLFK LV WKH FORVHVW OD\HU RI DWPRVSKHUH WR WKH HDUWK"

i. Stratosphere ii. Thermosphere

LLL 7URSRVSKHUH LY 0HVRVSKHUH

G $Q LQVWUXPHQW ZKLFK PHDVXUHV WKH UHODWLYH KXPLGLW\ RI D SODFH LV

i. Barometer ii. Hygrometer

LLL $QHPRPHWHU LY $OO RI WKHVH

H $W ZKDW GLVWDQFH IURP WKH VXUIDFH RI WKH HDUWK LV VWUDWRVSKHUH"
L NP LL NP
LLL NP LY %H\RQG NP

2. Answer these questions in very short.
D :KDW LV ZHDWKHU"
b. Name the four types of clouds.
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G :KDW LV IURVW "
H +RZ LV VQRZ GLIIHUHQW IURP IURVW "
I :KDW NLQG RI FOLPDWH GRHV WKH WHUDL UHJLRQ KDYH "
g. Name the layer of atmosphere that is the closest to the earth.
K :KDW LV R]RQH "

Times' Crucial Science and Environment 240 Book 7

L :KDW LV R]RQRVSKHUH "
M 1DPH WKH PDLQ JDVHV SUHVHQW LQ H[RVSKHUH
N 1DPH WKH WKHUPRPHWULF OLTXLGV XVHG LQ PD[LPXP PLQLPXP

thermometer.

'HÀQH b. Weather c. Climate
a. Cloud H 6QRZ I 6WUDWRVSKHUH
K $QHPRPHWHU
G $WPRVSKHUH
J 7HPSHUDWXUH

4. Answer these questions in brief.

D :K\ LV ZHDWKHU IRUHFDVWLQJ LPSRUWDQW WR WKH SHRSOH "

b. Write down differences between weather and climate.

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G :KDW LV SHUVLVWHQFH EDVHG RQ "

H +RZ LV ZHDWKHU IRUHFDVWLQJ GRQH E\ ORRNLQJ DW WKH VN\ "

I +RZ LV R]RQRVSKHUH XVHIXO "

J ([SODLQ WKH ZRUNLQJ RI PD[LPXP PLQLPXP WKHUPRPHWHU ZLWK
the help of diagram.

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L :KDW LV ZHDWKHU IRUHFDVWLQJ " 1DPH WKH WHFKQLTXHV RI ZHDWKHU
forecasting.

M :KDW LV SUHVVXUH " ([SODLQ WKH VWUXFWXUH DQG ZRUNLQJ RI PHUFXU\
barometer.

5. Write short notes on: b. Thermosphere
a. Troposphere G $QHPRPHWHU

F &DXVHV RI ZLQG

3URMHFW :RUN

Draw the diagrams of different instruments that are used to measure
GLIIHUHQW HOHPHQWV RI ZHDWKHU :ULWH WKHLU QDPH DQG H[SODLQ ZRUNLQJ LQ
a chart paper.

Times' Crucial Science and Environment 241 Book 7

Chapter

23 7 KH ( DUWK D Q G
6SDFH

ƐƟŵĂƚĞĚ ƉĞƌŝŽĚƐ͗ϳ

OBJECTIVES
At the end of the lesson, the students will be able to :
 ƚĞůů ƚŚĞ ŵĞĂŶŝŶŐ ŽĨ ƐŽůĂƌ ƐLJƐƚĞŵ͘
 ĞdžƉůĂŝŶ ƚŚĞ ǀĂƌŝŽƵƐ ŵĞŵďĞƌƐ ŽĨ ƐŽůĂƌ ƐLJƐƚĞŵ͘
 ƚĞůů ƚŚĞ ŵĞĂŶŝŶŐ ŽĨ ƉůĂŶĞƚ ĂŶĚ ƐƚĂƌ͘
 ĚŝīĞƌĞŶƟĂƚĞ ďĞƚǁĞĞŶ ƉůĂŶĞƚ ĂŶĚ ƐƚĂƌ͘
 ĚĞĮŶĞ ĐŽŶƐƚĞůůĂƟŽŶ ĂŶĚ ŐŝǀĞ ƚŚĞŝƌ ĞdžĂŵƉůĞƐ͘

MIND OPENERS
 ,ĂǀĞ LJŽƵ ƐĞĞŶ ƐƚĂƌƐ ŝŶ ƚŚĞ ƐŬLJ͍
 /Ɛ ƚŚĞ ƐƵŶ ƐƚĂƌ͍ /Ĩ LJĞƐ͕ ǁŚLJ͍
 tŚĂƚ ĂƌĞ ƉůĂŶĞƚƐ͍ ,Žǁ ŵĂŶLJ ƉůĂŶĞƚƐ ĚŽ LJŽƵ ŬŶŽǁ͍
 /Ɛ ƚŚĞ DĂƌƐ ƐƚĂƌ͍ tŚLJ͍
 tŚĂƚ ŝƐ ĐŽŶƐƚĞůůĂƟŽŶ͍ ŝƐĐƵƐƐ͘

7KH 6XQ DQG 6RODU 6\VWHP

The sun is a medium sized star. It is yellow in colour. It is the nearest
star from the earth. It is about 15 crore kilometers away from the earth.
,W SURYLGHV KHDW DQG OLJKW WR WKH HDUWK DQG RWKHU SODQHWV 0RRQ DQG RWKHU
planets shine due to the sunlight. It is 13 lakh times bigger than the earth.
,WV VXUIDFH WHPSHUDWXUH LV DERXW ƒ& DQG WHPSHUDWXUH DW WKH FHQWUH LV
DERXW ƒ& ,W FRQWDLQV WKUHH OD\HUV SKRWRVSKHUH FKURPRVSKHUH
and corona.

Corona
Chromosphere
Photosphere

The sun Layers of the sun Book 7
Times' Crucial Science and Environment 242

The sun contains more amount of hydrogen gas and less amount of helium.
The sun produces heat and light energy due to nuclear reaction taking
place in its core. The nuclear reaction taking place in the sun in the nuclear
fusion.

6RPH LPSRUWDQW IDFWV RI WKH VXQ

DĂƐƐ Ϯ п ϭϬϯϬŬŐ
ŝĂŵĞƚĞƌ ϭ͕ϯϴϮ͕ϰϬϬ Ŭŵ
ŝƐƚĂŶĐĞ ĨƌŽŵ ƚŚĞ ĞĂƌƚŚ ďŽƵƚ ϭϱ ĐƌŽƌĞƐ ŬŝůŽŵĞƚƌĞƐ
^ƵƌĨĂĐĞ ƚĞŵƉĞƌĂƚƵƌĞ ϲϬϬϬ°C
ϭϱ͕ϬϬϬ͕ϬϬϬ°C
ŽƌĞ ƚĞŵƉĞƌĂƚƵƌĞ

DĂũŽƌ ŐĂƐĞƐ ,LJĚƌŽŐĞŶ ;ϵϬйͿ ĂŶĚ ,ĞůŝƵŵ ;ϱйͿ

6RODU 6\VWHP The solar system

There are many heavenly bodies
which move around the sun due
to the gravitational force of the
sun. They make a family named
solar system. Solar system is a
group of the sun, eight planets
and their satellites, comets,
asteroids, etc which move around
the sun.

The sun is the main member
of solar system. It lies in the
centre. It moves around the
galactic centre carrying all other
members of solar system.

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Planets are the heavenly bodies which revolve around the sun in elliptical
paths. Planets do not have their own light. They appear bright because
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eight planets in the solar system. The eight planets of the solar system on
the basis of the increasing distance from the sun are as follows:

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7) Uranus 8) Neptune

Times' Crucial Science and Environment 243 Book 7

Mercury

This is the nearest planet to the sun. It is about
ð 7 km away from the sun. It is the smallest
planet of solar system. Its diameter is 4,851.2 km.
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It revolves around the sun in 88 days. It has no
atmosphere. It does not have any satellite. It is
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during night time.
Venus
It is the hottest and brightest planet of the solar
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243 days. It completes one revolution around the
sun in about 225 days.
It has no moon. It has an atmosphere of carbon
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sunrise and in the western sky after the sunset.
Therefore, it is called morning and evening star.
Earth
It is the third planet from the sun. It is the only
planet of solar system where the life is possible. It
has favourable conditions for the survival of life.
Therefore, it is called living planet.
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Its diameter is about 12,742 km. It takes about
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takes about 365 days to complete one revolution
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vapour. It has one satellite.
Mars

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km away from the sun. Its diameter is about 6,794
km. It takes about 24 hours and 37 minutes to
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about 687 days to make one complete revolution

Times' Crucial Science and Environment 244 Book 7

around the sun. The research proved that there was water present in the
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and Deimos.

Jupiter
It is the largest planet of the solar
system. ,W OLHV DERXW ð 7 km
away from the sun. Its diameter is
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complete one revolution around the
sun. It has thin ring around it. It
has a great red spot on the surface.
It is mysterious for scientists. It has
79 satellites. Europa, Ganymede,
callisto, etc. are main satellites of
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Saturn
It is the second largest planet of the solar
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takes 29.5 years to make one complete
revolution around the sun. Its diameter
is about 1,15,811.2 km. It is surrounded
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The rings are made up of rocks and move
around the Saturn. The density of the
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the water too. It has 82 satellites. Titan
is the main satellite.

Uranus
It is the second farthest planet from the sun.
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by using telescope. It is seen green with
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It takes about 17 hours and 14 minutes to

Times' Crucial Science and Environment 245 Book 7

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revolution around the sun. It is also surrounded by the rings. It has 27
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atmosphere contains mainly hydrogen, helium and methane.

Neptune

It is the farthest planet from the sun. It was
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ORRNV JUHHQ ,W LV DERXW ð 7 km away from the
sun. Its diameter is 48,972.8 km. It takes about 16
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about 164 years to make one complete revolution
around the sun. It has 13 satellites. Titron and
Nereid are the main satellites. Its atmosphere
contains mainly hydrogen, helium and methane. It
is the coldest planet.

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move around the sun. They are called asteroids. They are also called baby
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NP 7KH\ DUH DERXW LQ QXPEHU

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Asteroids

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two types of satellites:

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Natural satellite

Natural satellites are those heavenly bodies which revolve
around the planets. They do not have their own light. But
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Times' Crucial Science and Environment 246 Book 7