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Sources of Food
Summary
HD15:11
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Food
Food is essential for all the living organisms. Plants prepare their own food and store in their
special organs as fruits, tubers, seeds etc. Animals and human beings depend on this stored food
of plant. Bigger animals depend on smaller animals for their food. Human beings also depend on
animals for their food.
Importance of food
• Food provides energy.
• Food is needed for growth.
• Food helps in maintaining good health.
• Food maintains body functions.
• Food is necessary to heal wounds.
Ingredients
Food comprises of ingredients. An ingredient is a part of mixture that is added to prepare a dish.
Ingredients vary with different types of food. Ingredients can be obtained from plant sources and
animal sources.
Nutrients
Food comprises of essential nutrients namely, carbohydrates, proteins, fats, vitamins and
minerals. Carbohydrates and fats are called as energy providing food. Proteins are called as
body-building food. Vitamins and minerals are called as protective food.
Plant food products
Plant food products are the different types of food that we get from plants. Green plants are the
primary source of food. Plants provide us with vegetables, fruits, cereals, pulses, spices, nuts,
oils etc.
Edible parts of the plant
Almost all parts of the plants such as leaves, stems, roots, fruits, and seeds are considered to be
edible parts.
a) Roots: We eat plant roots in the form of carrot, turnip, radish and beetroot.
b) Stem: We eat stems of some plants as in sugarcane, coriander. One form of stem tuber is
potato. We also eat underground stem in the form of ginger.
c) Leaves: Many green leaves are the sources of calcium. Some leaves that we eat are spinach,
cabbage, amaranthus, curry leaves etc. Onion is also a form leaf which is underground.
d) Flowers: Flowers of pumpkin, cauliflower are edible flowers. Some types of roses are also
edible.
e) Fruits: We get edible fruits from many plants. Fruits can be fleshy fruits or dry fruits. e.g.
mango, guava, orange, apple, pear, grapes, banana etc. Almonds, cashew nut are used as nuts.
Some fruits are used as vegetables. Some of them are brinjal, tomato, lady's finger, beans, bottle
guard, snake gourd, bitter guord etc.
f) Seeds: Seeds which are edible can be used as grains, pulses and oil seeds.
Grains include rice, wheat, jowar, maize, ragi etc.
Pulses include grams, peas, beans etc.
Oil seeds include groundnut, sesame, mustard, coconut, sunflower seed etc.
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Animal food products
Animal food products are the different types of food that we get from animals. Animals provide
us with different products like milk, eggs, poultry, meat, honey etc. Animals obtain their food
from plants or other animals.
Poultry farm is the place used to rear birds for their eggs and meat.
Dairy farm is the place where buffaloes, goats, cows, sheep, pigs etc are kept in shed for rearing.
We rear animals for their milk and meat. Milk is also used to prepare dairy products.
Aquaculture includes rearing of fish, crabs, lobsters etc. Fish provide their meat for us. Fish can
be marine or freshwater fish.
Edible animal products
a) Milk: Animals like cows, buffaloes, goat, camel provide us their milk. Milk is rich in
proteins, fats, carbohydrates, vitamins and minerals. It is called as complete food as it has all the
nutrients.
b) Eggs: Eggs are rich source of proteins. We get eggs from birds like hen, duck etc.
c) Meat: Flesh of animals is called as meat. We get this form hen, duck, sheep, goat, pig, cow
etc.
d) Sea food: Fish, prawns, crabs also provide us their meat as food.
e) Honey: This is the food product obtained from honey bees. They collect nectar from different
flowers, mix it with a secretion from their mouth and convert it into honey. Bees store this honey
in their bee hives.
f) Dairy products: The products which can be made from milk are called as dairy products.
Some common dairy products which we use in our daily life are paneer, cheese, cream,butter,
curd, ghee etc.
Animals and their food
Based on food they eat, animals are grouped into three groups namely, herbivores, carnivores,
omnivores and decomposers.
a) Herbivores: Animals which eat only plants are called as herbivores. These are also called as
grass-eating animals. e.g. Cow, sheep, goat, deer, buffalo, camel etc.
b) Carnivores: Animals which eat only small animals are called as carnivores. These are also
called as flesh-eating animals. e.g. Tiger, lion, jackals, vultures etc.
c) Omnivores: Animals which eat both plants and animals are called as omnivores. e.g. Human
being, bear, crow etc.
d) Decomposers: Organisms which feed on dead plants, dead animals and rotten materials for
their food are called as decomposers.
Food habits in human beings
Human beings, based on the type of food they eat are grouped into two groups namely,
vegetarians and non-vegetarians.
a) Vegetarians: These are the individuals who depend on plants and plant products for their
food. Vegetarian diet comprises only pulses, grains, cereals, fruits, vegetables.
b) Non-vegetarians: These are the individuals who depend on animals and animal products for
their food. Non-vegetarian diet comprises eggs, meat, fish, poultry etc.
Test For Starch, Proteins and Fats
Nutrition
Nutrition is the way in which an organism obtains its food and how it is used in the body to get
energy. Food we eat should have the substances that are required by our body to carry out normal
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functions. These substances are called as nutrients.
Nutrients
Nutrients are nourishing components of food that are required by our body. They release energy
and help in body growth. Nutrients found in our food are carbohydrates, proteins, fats, vitamins
and minerals. Food also contains dietary fibres and water. Different types of food contain two or
more nutrients in combination.
Energy-giving food: Carbohydrates and fats are called as energy-giving food. Carbohydrates
provide us instant energy. Fats are stored energy resources.
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Body-building food: Proteins are considered to be body-building food as they help in body
growth and repair of damaged parts of the body.
Protective food: Vitamins and minerals are considered to be protective food as they protect us
from many dieases. They give us resistance against disease causing germs.
a) Carbohydrates: Carbohydrates provide instant energy to us. Carbohydrates in our food are of
three types, sugar, starch and cellulose.
Sugar is the sweet substance. Glucose is the instant sugar.
Fructose is available in fruits and is called as fruit sugar. Sugar is also present in honey.
Common sugar we use is sucrose. It is made from sugarcane.
Lactose is also a sugar present in milk. Hence, it is called as milk sugar.
Starch is present in grains like rice, wheat, maize, tubers like potatoes etc.
Cellulose is also a form of carbohydrate which cannot be digested by human beings. It can be
digested by grass-eating animals. Cellulose forms the bulk in our food.
Test to confirm the presence of carbohydrate (starch)
The following steps are performed to test the presence of starch in a food item.
Take small quantity of the food item to be tested on a porcelain tile.
Dilute it with two drops of water.
Put 2-3 drops of iodine solution on it.
Observe the colour of the food item.
Change of colour in the food item into blue-black indicates the presence of starch in the food
item.
b) Proteins: Proteins are the substances which help us in growth of our body.
Proteins help in healing of wounds. Proteins also help in repair of damaged parts in the body.
When our body does not receive any carbohydrates and fats to release energy, proteins can
release energy in those special cases.
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Test to confirm the presence of protein
The following steps are performed to test the presence of protein in a food item.
Take a small quantity of the food item to be tested.
Grind the food item and powder it by mashing .
Put the food item into a test tube.
Add 10 drops of water into the same test tube.
Add two drops of copper sulphate solution to the same test tube.
Add 10 drops of caustic soda solution and shake the same test tube.
Observe the colour of the mixture.
Violet colour indicates the presence of proteins in the tested food item.
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c) Fats: Fats are energy-giving food. They provide us with more energy when used up by the
body.
Fats are stored in our body for future use.
Fats can be obtained both from animals and plants.
Fats from animal sources include milk, butter, ghee, cheese and meat.
Fats from plants are called as oils.
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Seeds like mustard, sesame, groundnut, soyabean, coconut, sunflower, safflower can be used to
produce oils.
Test to confirm the presence of fat
The following steps are performed to test the presence of fat in a food item.
Take a small quantity of the food item to be tested.
Wrap the food item in a small piece of paper.
Crush the food item wrapped in the paper.
Straighten the paper.
Dry the paper by keeping it in sunlight for a while.
Observe the paper.
An oily patch on the paper indicates the presence of fat in the tested food item.
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d) Vitamins and minerals: These are the materials which occur both in plants and animals.
Vitamins protect our body from diseases.
Vitamins are required in small amounts but they are necessary in our diet. Deficiency in vitamins
causes many diseases.
Vitamins are present in two categories, fat soluble vitamins and water soluble vitamins.
A person can maintain his health by maintaining balance of vitamins and minerals in the food.
Vitamins and minerals are present in more quantities in fruits and vegetables.
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e) Dietary fibres: In addition to all these substances, dietary fibres are important materials in our
food.
Dietary fibres do not release energy. These are also termed to be roughage.
They help us in easy digestion of food.
They provide us bulkness in the stomach. We feel stomach full of food.
Green vegetables and leafy vegetables are rich in fibre content.
Beans, pulses whole grains, unpolished rice are also good sources of dietary fibres.
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f) Water: Water is an essential substance in our food. It helps in easy passage of food.
70% of our body is made up of water.It dissolves many substances in itself.
Water is an essential substance in our food.
It protects us from dehydration.
It helps in easy passage of food. It dissolves many substances in it.
Water also provides us some minerals.
Water forms the liquid medium of blood. It acts as main transport channel throughout the body.
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Nutrients and Balanced Diet
All living organisms require food to live. Food comprises of six important nutrients carbohydrates, proteins, fats, vitamins, minerals and water. Nutrients are essential to perform
various metabolic activities.
a) Carbohydrates are compounds of carbon, hydrogen and oxygen, always in the ratio of 1:2:1.
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They are oxidised in the cells to release energy. Carbohydrates include sugars, starch and
cellulose.
Carbohydrates are oxidised in the body into simple sugars like glucose.
They provide instant energy. When oxidised in the body, one mole of glucose releases 686
kilocalories of energy.
Carbohydrates are present in rice, wheat, jowar, maize and other grains.
They are also present in tubers and fruits. They are mainly present in rice, potato, banana, etc.
b) Proteins are formed by carbon, hydrogen, oxygen and nitrogen.
Nitrogen is the most essential element in proteins. Some proteins contain sulphur and phosphorus
also.
Proteins on digestion form simple molecules called as amino acids.
Proteins act as building blocks and serve as materials helping in growth and repair of the body
cells and tissues.
In an emergency, they may also get oxidised to release energy.
Protein helps in the formation of hair, nails etc.
Proteins also help our body in the synthesis of antibodies. Antibodies provide resistance against
germs.
Proteins are required for children who are at the stage of growth.
Protein deficiency in the diet causes diseases related with PEM (Protein Energy Malnutrition).
Proteins can be animal proteins of plant proteins. Animal protein rich food include eggs,fish,
meat, milk, cheese and pulses. Plant protein rich food include pulses of beans. Food rich in
proteins include lean meat, fish, eggs, milk, cheese, nuts, beans, peas, etc.
c) Fats are also made up of carbon, hydrogen and oxygen. Fats have very little oxygen content.
Fats produce more energy than carbohydrates do.
Fat below the skin protects the body against rapid loss of heat.
It serves as a solvent for fat-soluble vitamins. It is an important form of energy storage for future
use.
Common food rich in fats include milk, cheese, butter, cream, ghee, vegetable oils, meat, and
fish liver oils.
d) Vitamins are the chemical substances that help in maintaining a healthy body. Vitamins A, D,
E, and K are fat soluble and can be stored in the body. Vitamin B complexes and Vitamin C are
water soluble forms. They cannot be stored for a long period of time in the body.
Vitamin A: It promotes growth, vision. It is present in butter, egg yolk, milk, carrot, etc.
Vitamin D: It helps the body to absorb calcium and phosphorus which aid in the formation of
bones and teeth. It is present in fish liver oil, milk, eggs, etc. It helps individuals from disease
called scurvy
Vitamin E: Prevents the oxidation of vitamin A. It is present in meat, milk, whole wheat. It
prevents person from ageing.
Vitamin K: It helps in blood clotting mechanism during injury. It is present in cabbage, spinach,
leafy vegetables.
Vitamin B complex: B-complex vitamins are made up of 11 individual vitamins. All these Bcomplex vitamins are water soluble substances. These vitamins are necessary for healthy
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functioning of brain, nerves and muscles. It is present in wheat, rice and liver. They prevent
individuals from being affected by diseases like beri-beri.
Vitamin C: It helps in fighting against diseases like common cold, scurvy throat infections. It is
present in oranges, tomatoes, lemon and guava.
e) Mineral salts are needed in the diet in small quantities. These are obtained from table salt,
green vegetables and fruits. Some important minerals are listed below.
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Calcium is required for the following functions
Strengthening of bones and teeth.
Blood clotting.
Muscle contraction.
Rich sources: Milk, meat, eggs, fish, pulses, vegetables, etc.
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Phosphorus is required for following functions
Strengthening of bones and teeth.
ATP production during cellular respiration.
Conduction of nerve impulses.
Rich sources: Milk, meat, eggs, fish, pulses, vegetables, etc.
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Iron is required for following functions
Formation of hemoglobin in red blood cells.
Rich sources: Green leafy vegetables, liver, etc.
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Iodine is required for following functions
Proper functioning of thyroid gland.
Normal body growth.
Rich sources: Vegetables, mineral water and iodised salt.
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Sodium is required for following functions
To control the fluids in the body.
To carry nerve impulses in the body.
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Potassium is required for following functions
Formation of new cells.
To carry nerve impulses in the body.
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f) Water is the vital nutrient which helps the body in the process of absorption of nutrients from
the food.
It also helps the body to get rid of toxic wastes through urine and sweat.
It helps to maintain constant body temperature.
It keeps our skin moist.
It keeps the body soft.
It provides the medium for transportation of substances in the body.
g) Dietary fibres are necessary for smooth movement of food in the alimentary canal. They
provide bulk roughage to remove the undigested waste during defecation.
Balanced diet
It is the diet that contains all the principle constituents of food in appropriate quantities required
by the body. In other words, balanced diet is the diet that nourishes the body with sufficient
amount of nutrients required by the body. Balanced diet comprises the components like
carbohydrates, proteins, fats, vitamins, minerals and sufficient amount of water. Balanced diet
keeps our body fit and resistant to diseases. RDA is the Recommended Dietary Allowance which
should be followed by individual in order to maintain good health.
Body weight
Category
(kg)
Man
60
Woman 50
Boy
47
Girl
46
Energy in
kcal
2875
2225
2450
2060
Protein in
gms
60
50
70
55
Fat in
gms
15-20
15-20
22
22
Carbohydrate in
gms
225-300
220
130
130
Deficiency Diseases
Deficiency diseases
Disease is the abnormal condition which makes the body weak and a person cannot perform his
normal work. Deficiency diseases are the diseases which occur mainly due to the deficiency of
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one or more nutrients in the diet over a long period of time.
Wheat rich in carbohydrates is poor in nutrients like proteins and fats. Too much intake of wheat
products results in deficiency of proteins and fats, thereby reducing the growth.
Lack of proteins also results in stunted growth. It can cause skin diseases, swelling of the face,
discolouration of hair, and even causes diarrhoea.
So, a balanced diet is to be taken to avoid deficiency diseases.
Protein Energy Malnutrition (PEM)
Deficiency of proteins in the diet results in the development of diseases related to PEM.
Kwashiorkor and Marasmus are two types of diseases related with protein energy malnutrition.
a) Kwashiorkor is one type of disease related to protein energy malnutrition. It affects mainly
children under five years of age who do not get protein in their regular diet.
Symptoms: Child exhibits stunted growth, anaemia, swollen legs, discolouration of hair etc.
Treatment: Children affected should be given milk, eggs and other protein rich food.
b) Marasmus is also a disease related to protein energy malnutrition. It affects mostly infants
who feed on mother's milk who receive less proteins in their diet.
Symptoms: Lean muscles, weak bones, rough skin, weak legs, mental retardation etc.
Treatment: Protein rich diet should be consumed by mothers who feed their children with breast
milk.
Diseases caused by deficiency of minerals
a) Iron deficiency: Lack of iron in the diet leads to a deficiency disease called anaemia.
Symptoms: Headache, dark patches under the eyes, weakness and feeling tired.
Treatment: A balanced diet which includes iron-rich food such as apples, fish and raisins to
avoid anaemia.
b) Iodine deficiency: Lack of iodine in the diet leads to a deficiency disease called goitre.
Symptoms: Thyroid gland does not function properly. In adults, goitre results in swelling of
glands near the throat. In children, iodine deficiency causes stunted mental and physical
development.
Treatment: Iodine deficiency can be avoided by using iodised salt in the diet. It is advised to
have sea food which are rich in iodine.
c) Calcium deficiency: Lack of calcium in the diet makes the bones weak and brittle. It can also
cause tooth decay.
Symptoms: Rickets, weak bones and teeth prone to cracking, stunted growth, excess bleeding
from wounds.
Treatment: Diet should include milk, eggs, dairy products, leafy vegetables.
d) Phosphorous deficiency: Lack of phosphorous in the diet makes the bones weak and brittle.
Improper functioning of the heart and muscles. Genetic material in our body are not formed
properly.
Symptoms: Bones and teeth are fragile. Disorders in the muscular system.
Treatment: Diet should contain milk, green vegetables and cereals.
Diseases caused by deficiency of vitamins:
a) Vitamin A: Lack of vitamin A in the diet causes loss of vision.
Symptoms: Night blindness, i.e. poor vision in dim light, dryness in the mouth.
Treatment: Diet should contain carrot, mangoes, butter and egg yolk. These will help in
development of vision.
b) Vitamin B1: Lack of vitamin B1 in the diet causes a deficiency disease called beriberi.
Symptoms: Loss of weight, weak muscles, paralytic effect.
Treatment: Beans, meat, eggs and corn help in avoiding beriberi. Diet rich in vitamin B1 helps in
curing the disease.
c) Vitamin C: Lack of vitamin C in the diet causes a deficiency disease called scurvy.
Symptoms: Bleeding gums, swelling of joints. Moreover, wounds take longer time to heal.
Treatment: Oranges, tomatoes, lemon, guava and amla are rich in vitamin C. Consuming the
above fruits help us to avoid scurvy.
d) Vitamin D: Lack of vitamin D in the diet causes a deficiency disease called rickets.
Symptoms: Deformed and soft bones, decaying teeth.
Treatment: Diet should include fish, eggs, milk and butter to avoid rickets. In addition, exposure
to sunlight produces vitamin D in the body.
e) Vitamin E: Lack of vitamin E results in early ageing.
Symptoms: Wrinkles on face and body skin
Treatment: Diet should include milk, eggs etc
f) Vitamin K: Lack of vitamin K results in delayed clotting of blood.
Symptoms: Excess bleeding from injuries.
Treatment: Diet should include fish liver oil, milk eggs etc.
Fibres
The basic necessities for human beings are food, shelter and clothing.
Let us discuss about clothes and why they are important. Clothes guard our body from external
environment. They protect us from insect bite and they make us look good.
Depending on the climate of the place people wear different clothes. Clothes are made of
different types of materials.
For example: Cotton sari is made of cotton, Leather jacket is made of leather, Sweater is made of
wool, etc.
History of clothing
In the beginning of civilisation, people used bark, leaves and animal fur as clothes. When people
settled down as farmers, they used woven vines and animal fleece as clothes. In the next stage,
flax and cotton were woven into clothes. In those times, people just draped the fabric to cover
themselves. People started wearing stitched clothes only after the needle was invented. Even
today, in older cultures like India, you see people wearing unstitched garments like turbans, saris
and dhotis.
Fibre and fabric
Fabrics are made up of strands called yarns, which are made from even thinner
strands, called fibres.
fibres can be classified as natural fibres and synthetic fibres.
Natural fibres are obtained from natural sources, i.e. plants and animals.
Example: Cotton, jute, silk, wool, etc.
Synthetic fibres are man-made fibres and are not obtained from any plant and animal sources.
Example: Nylon, Polyester and Acrylic.
Plant fibres: Fibres obtained from plant sources are called plant fibres.
Example: Cotton, Jute, coir, and linen.
Animal fibres: Fibres obtained from animal sources are called animal fibres.
Example: Wool and Silk.
Cotton Fibres: Cotton fibre is obtained from cotton plants that grow in black soil in a warm
climate. In India, cotton is grown in Gujarat, Maharashtra, Andhra Pradesh, Punjab, Haryana,
Karnataka, Tamil Nadu, Rajasthan, Orissa and Madhya Pradesh.
The cotton plant bears fruits about the size of a lemon, called cotton bolls. The bolls are full of
seeds and cotton fibre. They burst open when they are ripe. The cotton fibres are collected by
hand from the ripe cotton bolls. This process is called picking. Next, the cotton fibres are
separated from the seeds by combing them. This is known as ginning. Earlier, ginning was done
by hand, but nowadays, a machine is used.
Jute Fibre: Jute fibre comes from jute plants, which are mainly grown in places that have
high temperatures and plenty of rainfall. Jute is cultivated during the rainy season. In India, jute
is cultivated in West Bengal, Bihar, Andhra Pradesh, Uttar Pradesh, Assam, Chhattisgarh and
Tripura.
The jute plant is generally harvested when it is in the flowering stage. The stems of jute plants
are soaked in water for a few days until they start rotting. Then the fibres are separated by hand
from the rotting stems. Once the fibres have been obtained, they are made into yarn by twisting
the strands together. This process of making yarn from fibre is called spinning.
Not just jute, even cotton, silk and other fibres are spun to convert them into yarn. Machines are
used for spinning yarn on a large scale. Fabrics like khadi are made by spinning yarn on handoperated devices like charkhas and taklis.
Conversion of Yarn to Fabric
For the conversion of yarn to fabric two main processes are used. They are weaving and knitting.
Weaving
Weaving is the process of arranging two sets of yarns together perpendicular to each other to
make a fabric. Fabrics are woven on looms. These looms may be operated by power or by hand.
Knitting
Knitting is a process that makes use of a single yarn to make a piece of fabric. While knitting, a
single yarn is used to make a piece of fabric. That is why, if you pull a single yarn from a torn
woolen garment, it keeps unraveling.
Knitting can be done by hand or on machines.
Other useful plant fibres
Coir
Coconut fibre can be woven into fabric called coir. Coir is too rough to be made into garments. It
is mostly used to make doormats, carpets and other flooring material.
Silk cotton
Silk cotton is obtained from kapok tree. The fruits of this tree contain fibres. These fibres are
light and fluffy.
Silk cotton is used commonly used as stuffing in pillows, sleeping bags and life jackets.
Hemp
Another important plant fibre is hemp. Hemp fibre is obtained from the stems of hemp plant. It is
mostly used to make ropes, carpets, clothes and papers and nets.
Properties of Materials
We use variety of objects in our day to day lives. Objects are made up of different materials.
An object can be made from more than one material
Example: Cake, Soaps
Different objects can be made from the same material
Example: Table, Chair, and Door are made from wood.
An object can be made from different materials
Example: Bottles from glass, Plastic, metals.
Importance of grouping
Grouping materials in groups makes it convenient for study. Objects are grouped on the basis of
their shapes, the materials they are made up of, and the properties of these materials. Materials
can be grouped on the basis of similarities or differences in their properties.
Grouping of objects on the basis of common properties
Objects are grouped on the basis of properties like lustre, hard/softness, transparency, solubility,
floatation, attraction towards magnet, conduction of heat and conduction of electricity.
Property - Lustre: Materials can be grouped as lustrous and non-lustrous on the basis of
lustre/shine possessed by them.
Lustrous materials are those that have a shine on them. Due to this property metals are widely
used for making jewellery.
Example: Gold, silver and most metals are lustrous in nature.
Non-lustrous materials are dull in appearance.
Example: Wood, Plastic, etc.
Property - Hard/Softness
Materials that can be compressed or scratched easily are called soft materials.
Example: Cotton, Sponge.
Some materials that are difficult to compress are called hard.
Example: Iron and most of the other metals.
Property - Transparency
Materials can be classified as transparent, opaque and translucent on the basis of transmittance of
light by them.
Transparent Materials
Transparent materials allow light to pass through them completely. One can see through such
materials
Example: Glass, water, Air and Some plastics
Opaque Materials
Opaque materials do not allow light to pass through them. You cannot see through them.
Example: Wood, cardboard and metals.
Translucent Materials
Translucent materials allow light to pass through them only partially. They are partially
transparent and partially opaque.
Example: Butter paper, Frosted glass.
Property- state
Everything in this universe is made up of matter. Matter exists in 3 states - Solid state, liquid
state and gaseous state.
Solid state
All solid substances are said to have solid state.
Properties of solid state
• Solids have definite shapes, volumes and are not compressible.
• The particles are closely packed and they cannot flow.
Liquid state
All liquid substances are said to have liquid state.
Properties of liquid state
• Liquids do not have definite shapes; they take the shape of the container and have definite
volume.
• The particles of liquids are loosely packed than the particles in solids
• They can be compressed to a small extent.
Gaseous state
All gaseous substances are said to have gaseous state.
Properties of gaseous state
• Gases have no definite shape or volume
• Particles of a gas are very loosely packed
• Gases are highly compressible.
Property - Soluble or Insoluble
Substances that completely dissolve in water are said to be soluble in water.
Example: Lemon juice, vinegar, sugar, salt are completely soluble in water and form a single
layer with water.
Materials (solids or liquids) that form distinct layers with water are said to be insoluble in water.
Example: Substances like sand and sawdust do not dissolve in water even if you stir them very
well. They are said to be insoluble in water.
Lemon juice, vinegar are completely soluble in water and form a single layer with water whereas
mustard oil and kerosene will not dissolve in water, but will form distinct layers. Liquids that are
soluble in water and form single layer with water are said to be miscible in water. Whereas
liquids that are insoluble in water and form distinct layers are said to be immiscible in water.
Some gases can dissolve in water as well. For example, oxygen dissolved in water is useful for
plants and animals that live underwater.
Property - Float or Sink
Materials that are insoluble in water either float on the surface or sink in water. Light materials
float in water.
Example: Paper, Plastic boll etc.
Heavy materials sink in water.
Example: Metals, stones etc.
Attraction towards a magnet
Substances that are attracted to a magnet are called magnetic substances.
Example: Iron, Nickel.
Conduction of heat
Materials that allow the heat to pass through them are called good conductors of heat.
Example: Generally metals are good conductors of heat.
Materials that do not allow the heat to pass through them are called bad conductors of heat.
Example:Plastic, air.
Conduction of Electricity
Materials that conduct electricity are called conductors.
Example: Generally metals are good conductors of electricity.
Materials that do not conduct electricity are called insulators or bad conductors of electricity.
Example: Plastic, Wood, air.
Methods of Separation I
In our day to day life we might have separate the useful substance from the mixture.
For example rice and pulses are cleaned before they cooked. We find tiny stones, small insects
and husk among the grains. We need to separate them before they are cooked.
Substances are mostly available in mixtures. A few substances are available in pure form. Hence,
we need to separate the useful substance from the mixture by using some methods.
Before studying the various separation methods we should know the need to separate the
components of a mixture.
Need for separation of substances
Substances need to be separated from each other to remove impurities or to get two or more
useful products.
Separation of substances can be carried out under two conditions
• Dry conditions
• Wet conditions
Separation of substances under dry conditions
There are various methods for separating substances, such as handpicking, threshing, winnowing
and sieving.
Handpicking
It involves simply picking out substances by hand and separating them from others. The
substances being separated may be impurities that have to be thrown away or it may be that both
the substances being separated are useful – such as if you separate green grapes from black ones
from a mixture of the two.
Threshing
This is done after harvesting of crops. Once wheat is harvested, the stalks are dried. Then, each
grain of wheat is separated from the stalks to which it is attached, so that it can be ground into
flour.
This method of separating grains from stalks is called threshing. It is basically the beating of the
dry stalks to shake off the dried grains
It can be done by hand, by cattle, or by using machines. Traditionally, threshing was done by
hand, but cattle help to do this job quickly. Nowadays, threshing machines are also used to
separate large quantities of grain at a time. One of these machines is a combine harvester
Winnowing
Once the wheat has been threshed, the grains should be cleared of the husk and chaff before
grinding into wheat flour.
The process of separation of lighter and heavier particles from the mixture by wind or blowing
air is called winnowing. The chaff is separated from the grains by winnowing. In this method the
farmer gently drops the mixture to the ground from a height. The heavier grains are collected at a
place, while the lighter chaff blows away.
Sieving
Sieving is used to separate substances that are of different sizes. In this method a sieve is used.
The smaller components of the mixture can pass through the pores of the sieve whereas bigger
components of the mixture are retained by the sieve.
For example, Wheat flour has some fine powdered wheat as well as some bigger
impurities. When this flour is put through a sieve, the fine powder falls through the small holes
in the sieve, while the thicker impurities remain as they are too big for these holes. And hence,
the substances are separated.
Methods of Separation II
Methods of separation of substances under wet conditions
Some solid particles are insoluble in water. For example chalk powder, dust particles, sand, and
tiny pieces of straw are insoluble in water. To separate this type of particles generally we use the
following methods
Sedimentation and Decantation
The process of separating insoluble substances which are heavier than liquid by allowing them to
settle down on their own due to gravity is called sedimentation. The particles which settle down
during sedimentation are called sediments.
Decantation follows sedimentation. In this process the clear upper liquid is poured out from
the container without disturbing the sediment. The upper clear liquid is called supernatant.
For example muddy water contains heavier particles like sand and soil. Leave this
muddy water undisturbed for some time. The heavier soil and sand particles settle down. And the
clear upper water is poured out from the container.
Filtration
Filtration is a process by which insoluble solids can be removed from a liquid by using a filter
paper.
A filter paper is a special type of paper which has pores that are tiny enough to let only liquids
pass through it. If you pass a solution through filter paper, any undissolved solid particles will
get left behind on the paper whereas the liquid will filter through.
The liquid that passes through is called the filtrate and the undissolved solid particles are called
residue.
Example: A mixture of chalk powder and water can be separated by this method.
To separate the soluble solids form liquids we use evaporation and condensation methods.
Evaporation
The process of conversion of water into vapour by heating it to its boiling point is called
evaporation.
The salt can be easily obtained from the salty water by the process of evaporation. If we boil
this water, the water evaporated completely, leaving behind only the salt.
Condensation
The process of conversion of water vapour into its liquid form is called condensation.
Example: The water vapour condenses and we receive the same water in the form of rain.
If you pour cold water in a glass, you will observe the formation of water droplets on the outer
surface of the glass . This is due to the condensation of water vapour present in atmosphere.
Separation of substances using more than one method
A mixture of sand and salt can be separated by combination of methods. The first method is
sedimentation and decantation. This mixture is put in water and left for the sand to settle for
some time. Then, we will decant the salty water, which will separate the sand from the mixture.
Now the salt can be separated from the water by evaporation. The water will boil away, leaving
the salt behind. So, the mixture of the sand, salt and water has been separated successfully using
a combination of sedimentation, decantation, evaporation and condensation.
Solution and solubility
Solution
A solution is prepared by dissolving a substance in a liquid.
Solute + Solvent = Solution
Salt + water = Salt solution
Saturated solution
A solution is said to be saturated if it cannot dissolve more of the substance in it at a particular
temperature.
Unsaturated solution
A solution is said to be unsaturated if it can dissolve more of the substance in it at a particular
temperature.
Changes Around Us
Every day, we see different types of changes around us, like day turning into night, the
season changing from winter to summer, melting of ice to water, cooking of food, etc.
Changes take place all around us all the time. All the changes are not of the same type we get
back the original substance in some, and can’t get them back in others.
Changes observed around us can be classified as
• Reversible change
• Irreversible change
Reversible Change
A reversible change is a change that can be undone or reversed. These changes are observed in
the physical state, size and shape of the substance. A reversible change does not create a new
material.
Examples: Melting ice, Boiling, evaporation and condensation, etc are the examples of reversible
changes.
If you could capture all the steam that is made when a kettle boils, you could turn it back
into water by cooling it.
Some other examples of reversible changes are folding a paper and blowing a balloon.
Irreversible Change
An irreversible change is a permanent change that cannot be undone. In an irreversible change,
new substances are formed.
Examples: Cake batter is made from eggs, flour, sugar and butter. Once the cake has been baked,
you cannot get the ingredients back.
Cooking is another example. We cannot get back the substances that we originally started with.
Mixing substances can also cause an irreversible change.
Examples: when vinegar is mixed with bicarbonate of soda, you can observe the release of
carbon dioxide gas in the form of bubbles. Again, here, we cannot get back our original
substances.
Some other examples of irreversible changes are the digestion of food and heating of lime stone.
The burning of wood is also an irreversible change. Once wood is burned, it changes to ash, and
we cannot get back the wood again.
Our growth itself, as you can see, is an irreversible change.
Relevance of Reversible changes in Daily Life
Working of Blacksmith
A blacksmith changes a piece of iron into different tools. For that, a piece of iron is heated to red
hot. This also softens it. It is then beaten into the desired shape. It is a reversible change.
Expansion and contraction of metals
Metals expand on heating and contract on cooling. This expansion and contraction of a metal is a
reversible change.
Small gaps are left between the rails that form the parallel lines of a railway track. These gaps
are called expansion gaps. These gaps allow the rails expand in hot weather. If there are no gaps
or gaps are too small the lines can bend.
Fixing wooden handles on tools
While making agricultural tools the metal ring is heated before fixing the wooden handle. On
heating the metal ring expands. When the ring become bigger size the wooden handle fix easily.
When the metal ring cools, it contract and the handle fits in tightly.
Fixing metallic rim on a wooden wheel
The fixing of metallic rim to the wooden base of the wheel of bullock cart can be done in the
similar manner. The metallic rim used is slightly smaller in diameter than the wheels .On heating
the rim expands. And can easily lie on the wheels. When the rim cools, it contract and press
tightly on to the wheels.
Categories of Plants
HD10:48
LearnNext Lesson Video
Plants are multicellular, mostly green organisms which are seen inour environment.
Classification of plants
1) Based on the size, nature of the stem and the life span, plants are classified into herbs, shrubs
and trees There is one more category called as creepers and climbers.
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a) A herb is a non-woody plant that has green and tender stem with few branches on.
It is usually short.
It has a very short life.
Herbs have a variety of uses like adding flavour to food, providing medicine for diseases and
some with spiritual touch.
Mustard, Tulsi, Wheat, Gram are some of the herbs we know.
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b) A shrub is taller than a herb and has stem branching out at its base.
Shrub is a bushy plant.
The stems of a shrub are not hard but thick.
A common place where shrubs are grown is known as shrubbery.
These plants live for many years.
Sunflower, Rose, Lime are some of the shrubs that we see around.
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c) A tree is a woody plant that has many branches on a single stem.
Trees serve us lot of benefits.
They prevent soil erosion, maintain carbon dioxide content in the air, provide us materials to
make huts and to make furniture.
Trees are categorised based on their height, width of their trunk, overall size, and of course their
age.
Trees are with long life span.
Mango tree, Neem tree, Peepal tree are some of the trees in our surroundings.
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d) Creepers are the plants with weak stems and hence cannot stand straight.
They grow on the ground.
Creepers as the name suggests creep horizontally on the ground.
Creepers are capable of growing new plants on their own.
Some creepers can also cause allergies or skin problems if touched.
Life time of creepers if very short.
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e) Climbers are the plants that need support from other structures to grow and spread.
Climbers can either grow horizontally or vertically unlike creepers that grow only in horizontal
direction. Lifespan is very short in climbers.
The climbing plants use these tendrils to cling on to the support firmly.
A tendril can be a modified leaf or a shoot or petiole like structure which is used by climbers to
wrap around a support.
Different types of tendrils are leaf tendril, stem tendril, leaflet tendril, leaf tip tendril etc.
Climbers attract insects and reptiles by their bright coloured flowers and fragrance.
2) Depending on the presence of flowers, plants are classified into two types namely, flowering
plants and non-flowering plants.
a) Flowering plants are the plants which possess distinct roots, stems, flowers and fruits. e.g.
Mango, Papaya, Guava.
b) Non-flowering plants are the plants which do not have distinct roots, stem, leaves, flowers or
fruits. e.g. Fern, Moss.
3) Depending on the way they obtain food, plants are classified into autotrophs and heterotrophs.
a) Autotrophs are the plants which make their own food by the process of photosynthesis by
using raw materials like carbon dioxide and water. e.g. Most of the green plants.
b)Heterotrophs are the plants which depend on other organisms for their food. e.g.
Insectivorous plants.
Parts of a Plant
Summary
Parts of a plant
A typical plant has different parts in its body. Different parts of the plant are the roots, stem,
leaves, flowers and fruits. The parts which are present under ground are the roots. Parts which
are present above the ground are stem, leaves, buds, flowers, fruits and seeds.
Root
The roots of a plant are mostly seen underground and look brown in colour. The tiny thread-like
structures over the roots are the root hairs. The tip of the root is covered by root cap which is
preventive in function. Root and the root hairs form the root system.
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Features of root
Root grows towards the soil and away from the light. Hence, it is called as geotropic structure.
Root does not possess green colour pigment, the chlorophyll. It cannot produce food.
Root does not bear leaves, buds or flowers.
Roots along with their root hairs absorb water and minerals from the soil.
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Functions of root
They hold the plant firmly in the soil, thereby serving as an anchor to the plant.
They absorb water and nutrients from the soil required for the growth of the plant.
Some roots also store starch and sugars in them.
Some roots also help in respiration. They possess special structures called as pneumatophores.
Some roots have useful bacteria in them to increase the soil fertility with nitrogen content.
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Types of roots
Roots are of two types - tap root and fibrous roots.
Tap root is a primary root that grows more or less straight down into the soil, and is tapered
towards the end. It is found in many of the plants. It is also called as true root. Smaller roots that
branch out from the tap root are called as lateral roots. Examples of plants with tap roots are
hibiscus, carrot, turnip and sunflower.
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Fibrous roots are a group of lateral roots arising at the base of the stem. In the plants bearing
fibrous roots, tap root slowly weakens and replaced by bunch of roots arising from the base of
the stem. These bunch of roots form the fibrous roots. Examples of plants with fibrous roots are
banana, grass and onion.
Modifications of roots
Roots in many plants are modified to perform additional functions by some modifications.
Storage roots are the roots modified to store food in them. e.g. Carrot, turnip, radish, sweet
potato etc.
Respiratory roots are the roots modified for respiration. The plants in magroves have roots with
special structures called as pneumatothodes to obtain more oxygen.
Parasitic roots are the roots which arise from the stem and absorb nourishment from the host
plant. e.g.Cuscuta.
Climbing roots are the roots which help the plant to climb and cling on to the support. e.g.
Money plant, betel.
Reproductive roots are the roots which help in the process of producing the offspring.
Prop roots are the roots which offer support to huge structure of the tree. e.g. Banyan tree
Stem
The stem is the part of the plant seen above the ground. It bears the leaves, flowers and fruits of a
plant. It is almost green or woody. It grows towards the sunlight. It moves away from the ground.
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Features of stem
They support the entire plant to stand as a whole.
They are always phototrophic. i.e. they grow towards light.
Stem has nodes separated by internodes. Stem bears branches, leaves, flowers and fruits.
Functions of stem
Stem helps in transportation of absorbed water and nutrients through vascular tissue from roots
to leaves
Stem also transports food from the leaves to different storage organs.
Stem exposes leaves to light and help them in performing the process of photosynthesis.
The stem bearing leaves helps in the process of transpiration. Transpiration is the process by
which plants release excess water in the form of water vapour through minute openings in the
leaves called as stomata.
Sometimes stem can store food which is mostly underground.
Stem can store water by becoming fleshy as in desert plants.
Stem can perform photosynthesis when leaves are reduced or absent as in desert plants.
Modifications of stem
Stems in many plants are modified to perform additional functions by some modifications.
Storage of food: In some plants, underground stem is modified to store food in the form of
starch. Three types of underground modifications of stem are tubers (e.g. Potato), rhizome
(e.g.Ginger) and bulb (e.g.Onion).
Photosynthesis: In some desert plants, leaves are absent or reduced to spines. Here, the stem
performs photosynthesis to synthesise food.
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Protective structures: In some plants like rose, stems are modified into thorns to protect the
plant from being eaten by animals.
Supportive structures: In climbing plants, stems are modified sometimes into structures which
twine around the support.
Storage of water: In some plants like cactus and jade, stems become fleshy and succulent to
store water.
Leaves
Leaves are the structures which develop on branches. These are green coloured structures rich in
chloroplasts. As they have chlorophyll in them, they are considered to be food factories of the
plant. Photosynthesis occurs in the leaves. Each leaf bears a bud in its axil.
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Parts of leaf
The point of attachment of the leaf to the node on the stem is called as leaf base.
Leaf bears a stalk with which it is attached to the stem. It is called as petiole.
The flat part of the leaf exposed to light is called as lamina.
A thin structure which extends from the leaf base to the tip on the lamina is called as mid-vein.
Many small thread like structures extend from the mid rib to the leaf margin. These are called as
veinlets. Arrangement of veins on the lamina of the leaf is called as venation. Veins help in
transportation of food and water.
Two types of arrangement of veins on the leaf are parallel venation and reticulate venation.
Types of leaves
Leaves can be simple leaf or compound leaves.
Simple leaf is a single leaf with undivided lamina.
Compound leaf is a leaf which has divided lamina into a number of leaflets. The central structure
called rachis bears all the leaflets.
Arrangement of leaves
Leaves are arranged in different patterns at the node on the stem. Arrangement can be
alternate,opposite, whorl etc.
Alternate leaves are the ones which arise one at a node.
Opposite leaves are the leaves which arise as two at a node.
Whorl type of arrangement includes three or more leaves arise at a node.
Structure and surface of the leaf
Leaf has two surfaces namely, dorsal surface and ventral surface. Dorsal surface is the upper
surface which is exposed to sunlight. It has number of chloroplasts having lot of chlorophyll in
them. Upper surface of the leaf is dark green in colour.
Leaf has many pores called as stomata on both of its sides. These stomata help in exchange of
gases like oxygen and carbon dioxide. Stomata also help in loss of excess water by the process of
transpiration.
Functions of leaf
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Leaves are the food factories of the plant which help in the process of photosynthesis to
synthesise their food. They make use of raw materials like carbon dioxide and water in the
presence of chlorophyll and sunlight.
Leaves lose excess water by the process of transpiration. Transpiration cools the body of the
plant by regulating the temperature.
Modifications of leaf
In weak stemmed plants, leaves are modified into special structures which twine around a
support. These are tendrils. These offer support to the plant while climbing up.
In some plants like onion, leaves are modified to store food. These are termed to be scaly leaves.
In some desert plants like cactus, leaves are reduced to spines so as to reduce loss of water
through transpiration. These spines are also called as thorns. Thorns protect these plants from
grazing animals.
In some insectivorous plants, leaves are modified into pitchers where they are used to trap
insects. These insects can be digested inside the body of the plant. In this way, plants obtain
nitrogen from animals.
Flower
Flower is a reproductive structure of the plant. The different parts of a flower include sepals,
petals, stamens and pistil. Flower helps the plant to give rise to new plants by the process of
sexual reproduction.
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Parts of a flower
The green leaf-like structures surrounding the bud are called as sepals.
The coloured parts of a flower are called as petals. These help in attracting insects.
The male reproductive part of a flower is called as stamen. It carries pollen grains.
The female reproductive part of a flower is called the pistil. It carries ovules.
Fruit
Fertilisation is the union of male and female cells in a flower to produce a fruit. Fruit is basically
the fertilised ovary. This grows in size to store sugars. Ovules develop into seeds. So, fruits
enclose seeds.
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Parts of a Flower
Flowers
A flower is the reproductive part of a plant. It is the most attractive part of the plant. Different
parts of a flower include sepals, petals, stamens and pistil. Parts of a flower can be grouped into
two categories namely, accessory whorls and essential whorls.
Accessory whorls are also called as vegetative whorls which include sepals and petals.
Essential whorls are also called as reproductive whorls which include stamens and pistil.
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Complete and incomplete flowers
A flower can be complete or incomplete based on the number of whorls present in it.
Complete flowers are the flowers which possess all the four whorls on it.
Incomplete whorls are the whorls which do not possess any one or more of the four whorls.
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Unisexual and bisexual flowers
Flowers can be unisexual or bisexual based on the reproductive structures present in it.
Unisexual flowers are the flowers which have either one of the reproductive structure i.e. either
the stamen, male reproductive structure or the pistil, female reproductive structure. Flower is
termed to be a male flower if it has only stamens. It is termed to be female flower if it has only
pistil.
Bisexual flowers are the flowers which have both male and female reproductive structures,
stamens and pistil in them. Bisexual flowers are also called as hermaphrodite flowers.
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Sepals
These are hard, leaf-like structures around the base of a flower.
They protect the bud before it blooms into a flower.
These are green in colour in most of the plants.
The sepals are collectively called as calyx.
The number of sepals varies from plant to plant.
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Petals
These are brightly coloured portions of a flower.
They petals are collectively called as corolla.
They are brightly coloured so as to attract insects and birds for pollination.
The number of petals is almost equal to the number of sepals in a flower.
In some flowers, the petals and sepals combine to form a round structure called as tepal.
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Stamens
The stamens are the male reproductive parts of a flower. Stamen is made up of a filament and
anther.
Anther is a bilobed structure at the tip of the filament.
Anther contains male reproductive cells, the pollen grains.
Pollen grains are the male reproductive cells which are very light, that they can be carried away
by wind.
Pollen grain has a thick covering made up of two layers, outer exine and inner intine.
Pistil
The pistil is the female reproductive part of a flower. It is made up of the stigma, the style and
the ovary.
Stigma is a bulged sticky structure at the tip of the pistil. As it is sticky it receives pollen grains
from the male reproductive structure.
Style is a long tube like structure which allows pollen grain to travel from stigma to ovule, the
egg cell.
Ovary is a large lobed structure at the base of the carpel. It contains the female reproductive
cells, the ovules. The number and arrangement of ovules differ in different flowering plants.
Joints and their Types
Human beings exhibit locomotion. Locomotion is brought about by the combination of muscular
and skeletal system. The bending and movement of the skeleton is brought about by special
structures called as joints.
Joints
Joint is a point at which two separate bones meet. Joints are held at position by strong cords
called as ligaments. Joints can be classified based on the type of movement they bring about.
There are three main types of joints in the human body. They include fixed or immovable joints,
slightly movable joints and freely movable joints.
a) Fixed or immovable joints are the joints which do not allow the structure to move but they
offer protection for the structure in which they are present. Examples are the sutures between the
bones of the cranium,ribs in the breast bone, bones of the hip girdle.
b) Slightly movable joints provide support to the structure in which they are present. They also
help the structure to move slightly. Example includes joints of the lower jaw which are slightly
movable.
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c) Freely movable joints are the joints which solely help in the movement of the structure or
organ in which they are present. Four immovable joints present in our body are Ball and socket
joint, Pivot joint, hinge joint and the gliding joint.
Ball and socket joint: This joint is formed by two bones in which one end of a bone is rounded
and ball-like. It fits into a cup-like depression of the other bone. This joint provides movement in
any direction. Examples of a ball and socket joint are shoulder joints and hip joints.
Pivot joint: This is the joint in which one bone fits into a ring formed by the other bone. It
rotates over the pivot-like end of the other bone. Example is the joint which joins the neck to the
head. Head rotates over the neck.
Hinge joint: This is a joint which moves like a hinge in a single plane not more than 180
degrees. It provides back and forth movement of the structure. This is a joint which can be
compared to that of a hinge in the door. Examples of a hinge joint are the elbow joint and the
knee joint.
Gliding joints: This is a joint which allows bones to glide over each other. These types of joints
provide little movement in all directions. These are the joints present at the ankles,wrist and
between vertebrae.
Movement in bones
Joints along with muscles can bring about movement in bones.
One end of the muscle is attached to a movable bone and the other end of the muscle is attached
to a fixed bone.
Muscles are attached to bones by tough cords called as tendons.
Muscles work in pairs and bring about movement by contraction and relaxation.
The paired muscles are biceps and triceps which together help in the movement of the structures
like arm, leg etc.
Contraction brings in the shortening of the muscle and relaxation brings about lengthening of the
muscle. It makes the muscle short, thick and stiff to pull the bone .
When the arm is folded, biceps contract and triceps relaxes and lengthens.
When the arm is straightened, biceps relax and lengthen whereas triceps contract.
Bones and Skeleton
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Skeleton
The skeleton is an internal framework of all the bones and cartilage in the human body. It is
made up of 206 bones. It gives the shape and structure to support the body. Babies at birth
possess 300 separate bones. Later some of the bones fuse together and finally an adult has 206
bones making up the skeleton.
Bone is a type of fibrous connective tissue. Bones provide support to the structures in the body.
Bone cells are embedded in a hard matrix composed of calcium and phosphorus compounds.
Bones also anchor the muscles. The strongest longest and the heaviest bone in the human body is
femur. It is located in the thigh region of the leg.
Cartilage is a soft elastic tissue that covers the bones at the region of the joints. It offers support
to the structure. It connects the bones together. Cartilage has widely spaced cells suspended in a
matrix of proteins and sugars. It is found in the nose, ears, and the rings of the trachea to give
flexibility.
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Types of bones
Bones can be of different types based on their rigidity.
Round and long: Bones can be round and long as in limbs.
Ring like bones with outgrowths: Bones in the vertebrae are ringlike with outgrowths on both
the sides.
Flat and strong: Bones in the skull are flat and strong.
Girdles: Bones are present in the form girdles in the shoulder region and pelvic region.
Parts of skeleton
Human skeleton is of two parts, axial skeleton and appendicular skeleton.
Axial skeleton includes the skull, vertebral column and the rib cage.
Appendicular skeleton includes shoulder bone, pelvic bone, arm bone, and the leg bone.
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Axial skeleton
a) Skull
Skull is a hard structure made up of small bones. It forms the cranium and the face. Cranium
protects the brain.
Skull is formed by 22 bones out of which 8 bones are fixed together to form the cranium and 14
bones fuse to form the face.
The only bone which has movable joint is the lower jaw. This movable joint is supported by
muscles and ligaments.
Skull placed on the top of the backbone can be moved up, down and sidewards.
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b) Vertebral column
Vertebral column running at the back of the body is also called as spine or the backbone.
It is in the trunk region to offer support to the upper part of the body.
Vertebral column is made up of individual bones called as vertebrae.
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Total vertebral column consists of 7 cervical vertebrae, 12 lumbar vertebrae, 5 fused sacral and 3
fused coccygeal vertebrae.
Vertebral column runs from the base of the skull to the hip bone forming a tube. Spinal cord
passes through this hollow tube.
Movement of neck can be up, down or sidewards.
Vertebrae are joined by gliding joints which offer spring movement to the backbone. Body can
be bent back, front or sidewards.
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Functions of vertebral column
It protects the spinal cord.
It supports the head.
It serves as an attachment for the ribs.
It provides support and place of attachment for the pectoral and pelvic girdle.
It provides movement for the human skeleton.
It helps in walking and standing erect, correct posture.
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c) Rib cage
Rib cage occupies the chest region. It is cone-shaped structure made up of 12 pairs of ribs.
Ribs are attached to vertebrae at the back which curve around to form a cage.
10 pairs of ribs are attached to the breast bone at the front.
2 pairs of lower ribs are free at front. These are called as free-floating ribs.
Rib cage is set up in such a way that it can contract and expand during the process of breathing.
Rib cage protects the underlying lungs, heart and some part of liver etc.
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Appendicular skeleton
a) Shoulder bone
Shoulder bone is formed by collar bone at the front and the shoulder blade at the back.
The collar bone is supported by breast bone at one end and the shoulder blade at the other end.
The shoulder bone encloses a socket like cavity into which fixes the ball of the upper arm.
This forms a ball and socket joint. This girdle is also called as pectoral girdle.
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b) Pelvic bone
Pelvic bone is also called as pelvic girdle. It is made up of strong bones to balance entire weight
of the body.
Pelvic girdle is formed by five fused vertebrae at the back and form a cavity in the centre while
reaching the front part.
The thigh bones are attached to either side of the girdle with a ball and socket joint.
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c) Arm bone
Arm bone is the upper limb made up of humerus, radius, ulna, carpals, metacarpals and
phalanges. All these bones are joined by hinge joints which allow the limb to move only in one
direction.
Humerus makes up the upper arm.
Fore-arm is made up of radius and ulna.
Wrist is made up of carpals.
Palm is made up of metacarpals.
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Fingers are made up of phalanges
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d) Leg bone
Leg bone is the lower limb made up of femur, tibia, fibula, tarsals, metatarsals and phalanges.
All these bones are joined by hinge joints which allow the limb to move only in one direction.
Knee is covered by a cap like structure called as patella or a knee cap.
Femur makes up the thigh bone.
Leg is made up of tibia and fibula.
Ankle is made up of tarsals.
Foot is made up of metatarsals.
Toes are made up of phalanges.
Gait of Animals
Animals have their own way of movement or locomotion. The animals which have a backbone
are called as vertebrates. Presence of endoskeleton helps the animal to be stiff and erect. Muscles
and bones help in the movement of animals. The pattern of movement of limbs of animals is
called as gait. Gait of lower animals differs from that of larger ones.
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Gait of earthworms
Earthworm is a small annelidan which mostly lives in the soil.
Earthworms are small worms which can move easily on hard surfaces.
Earthworms move with help of tiny, stiff hair-like projections called bristles.
Every body segment of the earthworm possesses setae which help in their movement. Setae get
firm hold on the ground.
Earthworms move forward by repeated contractions and relaxations of their muscles in the skin.
A slimy substance secreted by the earthworm helps in its movement.
Gait of cockroaches
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Cockroach is an arthropod with six jointed legs.
Six legs of the insect help it to walk, and two pairs of wings help it to fly.
Cockroach does not possess any bones making up endoskeleton.
Exoskeleton is the hard and stiff outer covering of the body made up of chitin.
Exoskeleton is a jointed structure which helps in the movement of the body.
A cockroach moves its legs with the help of muscles near the limbs.
It uses its breast muscles to move its wings and fly.
A cockroach can walk, fly and even climb.
Gait of snails
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Snail is a small molluscan with thick exoskeleton.
Snail is protected by its external skeleton called as shell.
Snails are found in wet places.
Entire body except the foot lies inside the shell. When disturbed, snail even retracts the foot in to
the shell. Snail moves with the help of single muscular foot.
The under surface of the muscular foot is lubricated with mucus. The muscular foot glides over
the surface. The rhythmic contractions and relaxations of this muscular foot brings about pulling
action in the body.
The secreted mucus also reduces the risk of injury from sharp objects.
Gait of fish
Fish is a vertebrate with vertebral column in its body.
The body of the fish is supported by endoskeleton made up of bones.
Fish possess a streamlined body which helps them to swim in water. Fish swim with the help of
their fins. The tail flaps from side to side to make them swim in the right direction.
Some fish, however, move by bending their bodies from one side to another in quick succession.
This produces a thrust that helps it move forward.
Movement of fish in water is also supported by air bladder filled with air. It helps the fish to rise
or dive deep into water.
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Gait of snakes
Snakes are vertebrates with vertebral column.
Body is supported by a skeleton made up of vertebrae which run continuously from head to tail.
As they do not have any limbs, snakes do not have appendicular skeleton.
Snakes move in a loop-like, zig-zag manner. They cannot move in a straight line. T
hey have difficulty in moving on very smooth surfaces.
Snakes have a long back bone and many interconnected muscles that help them to slither.
They have muscles connecting the backbone, ribs and skin.
Snakes move in grass, sand and water. Though the snakes do not have arms or legs, they can
climb trees.
Gait of birds
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Birds are arboreal in habit. Birds exhibit two types of locomotion.
They fly in the air. They can also walk.
A bird has a body best suited for flight.
Forelimbs are modified into its wings.
Birds have light and hollow bones.
The breast bones are connected to strong muscles which help them to flap their wings during
flight.
The tail controls the direction of flight. Birds have very strong shoulder bones.
Birds can walk and perch on trees with the help of their hind limbs.
Habitat and Adaptation
Livings things exist in most places of earth. Life exists in both extremely hot and extremely cold
regions. Habitat of an organism is its immediate surroundings. Habitat is the home of the
organism where it can find food, shelter and favourable conditions for breeding. Habitat includes
both living and non-living components. Plants and animals possess special characters which help
them to survive in their own habitat.
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Types of habitat
Habitat can be terrestrial or aquatic.
Terrestrial habitat is further classified into forests, grasslands, deserts, mountains and polar
regions.
Aquatic habitat can be classified into freshwater habitat, marine habitat and the coastal habitat.
Terrestrial habitat
It refers to the land where all plants and animals survive. Animals and plants which live on land
are called as terrestrial animals and terrestrial plants. Animals and plants living on the land
respire oxygen from air. They release carbon dioxide during this process. Terrestrial habitat
includes forests, grasslands, deserts, mountains and polar regions.
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a) Forests: These are large areas covered with trees and plants. Organisms living in the forest
depend upon abiotic factors like air, availability of water, temperature, sunlight etc. Wild life in
the forest include both plants and animals. All these organisms are interdependent on one and
other. Plants can synthesise their own food and store in their body. Animals make use of this
food for survival.
Three types of forests are tropical forests, temperate forests and boreal forests.
Tropical forests are known as Rain forests are the forests which occur between equator and the
two tropics. The temperature is maintained between 20oC and 34oC. They receive rainfall
throughout the year. Annual rainfall is about 200cm. Different types of flora and fauna occur in
these forests.
Temperate forests occur in Northeast Asia, North America and Central Europe. Temperature
ranges between -30oC to 30oC. Annual rainfall is about 150cm and is received throughout the
year. Summer season is demarcated from winter season. Trees are deciduous trees.
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Boreal forests are also called as Taiga forests. These forests are scattered over many places
which include, China, Canada, Russia, Northern Japan etc. Temperature ranges between -50oC to
30oC. Annual snowfall ranges from 40 to 100 cm.
b) Grasslands: These are mainly covered by long and thick grasses. Temperature ranges
between -20oC and 30oC. Annual rainfall they receive varies between 50cm and 90cm. Animals
like zebra, giraffe, lion and elephant are prevalent.
c) Deserts: These are the areas that receive scanty rainfall. These are dry with sand covering the
whole region. Deserts are mostly hot regions but some of them are even too cold regions.
Temperatures are too high during day time and too low during night time. Annual rainfall is less
than 25 cm. Animals like camel, rattle snake, kangaroo rat are found in deserts. Plants like cactus
and thorny plants are prevalent.
d) Mountains: These regions are rocky and dry. Sometimes water occurs as flowing streams.
Plants present on hills are xerophytes. These are conical and evergreen. Many climbers are found
covering the huge trees. As the height of the mountain increases, temperatures fall down and
animals are adapted to live in those cold conditions. Winds are dry and cold. Animals like Yak,
bear, hill goats, flying fox are the examples.
e) Polar region: These regions are covered with high snowy peaks. Animals found here are
adapted by having thick furry coat on the skin. They also have a layer of fat under the skin. This
fat is used as reserved food during ice-cold winter. Animals like polar bears, seals, foxes are
seen. Penguins are seen standing in the ice. Fish are adapted to live in ice-cold water.
Aquatic habitat
It refers to the region covered with water where plants and animals survive. Aquatic habitat is
further divided into freshwater habitat, marine habitat and coastal habitat. Water is the medium
for the organisms living in aquatic habitats.
a) Freshwater habitat: These are the water bodies filled with fresh water. These include rivers,
lakes, ponds, streams etc. Water present has very low concentration of salts. Plants growing in
water are called as hydrophytes.
b) Marine habitat: Ocean and seas are termed to be marine habitat. These are full with life.
Different varieties of organisms exist in marine habitat. Organisms like, corals, shelled animals,
sponges, jelly fish, sharks and many others are found in this habitat.
c) Coastal habitat: This is the region represented by the place where land meets the sea.
Estuaries are formed when the saltwater mixes with freshwater. These habitats are unique
Special type of trees called as mangroves are found in this region. Animals are also well adapted
to live in these regions.
Adaptations
The ability of living organisms to adjust themselves to the surroundings is called as adaptation.
Adaptations are the changes in structure or behaviour of an organism that will allow the
organism to survive in that habitat. Plants and animals make some natural adjustments in some
features to fit themselves into their environment. Different living organisms adapt themselves to
their habitats in different ways. Adaptations can be brought about by changes in the body,
changes in the behaviour and changes in location.
Acclimatisation:
The ability of an organism to make small adjustments or changes in the body in a short period of
time to adjust itself to the surrounding atmosphere is called acclimatisation. People who visit
mountain ranges suffer from altitude sickness due to poor oxygen content in the atmosphere at
such heights. Their body gets adjusted or acclimatised to changes in the surroundings.
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Components of a habitat
The components in a habitat are broadly classified into two types, namely biotic and abiotic
components. Biotic components interact with abiotic components to obtain all the necessary
conditions.
Biotic components include all the livings organisms in a habitat, i.e. plants, animals and
microorganisms.
Abiotic components include all the non-living things in a habitat, i.e. air, soil, water, sunlight and
temperature. The favourable conditions for survival of living organisms are provided by abiotic
components.
a) Air: Air is essential for all the living organisms on earth. Plants and animals take in oxygen
from the air during respiration. Plants take in carbon dioxide during the process of
photosynthesis. Air also provides nitrogen which is fixed to the plants for utilisation. Air is
required by organisms to cool their body. Winds help in generating energy. Winds also help in
carrying the seeds for distant places.
b) Soil: Soil is the topmost layer of the earth. Soil is rich in minerals and microorganisms which
help in different ways for plant growth. Soil also possess certain spaces which lodge water
particles. This water lodged in the spaces is used by plants by the process of absorption.
c) Water: Three-fourths of our earth is covered with water. Water is essential for life. Water
forms a medium for many metabolic reactions taking place inside the body. Water can be fresh
water or marine water. Animals living in water are called as aquatic organisms. Plants specially
living in water are called as hydrophytes. Humidity and rain are also the forms of water which
help the living organisms.
d) Sunlight: Sun is the ultimate source of energy for all the living organisms on earth. Plants
depend on sunlight for synthesising their food by the process of photosynthesis. Animals depend
on plants for their food i.e. indirectly they depend on sunlight.
e) Temperature:Temperature at a place depends on the sunlight available at the particular place.
Temperature also influences the humidity of that particular place. Areas may be too hot,
moderate or too cool. Some animals hibernate during cool winter and some of them aestivate
during hot summer.
Types of Habitat
Habitat: Habitat is the immediate surroundings of an organism. It is the place that is natural for
the life and growth of an organism. Animals and plants adapt themselves for their different
habitats.
Terrestrial habitat: All the deserts, mountains and forests and grasslands are included under
terrestrial habitat.
Desert: Camels show different adaptations to live in deserts. They possess long legs, long
eyelashes, covered nostrils, special fat cells, modified cells in the stomach as adaptations.
Snakes and rats live in burrows and come out only during the night when it is cool.
Plants present in the forest are xerophytes or desert plants exhibit some adaptations to live in the
desert conditions. Leaves are reduced to spines. Stems are green and fleshy to carry out
photosynthesis and to store water. Roots grow deep into the soil to absorb water. The reduced
leaf and the thick waxy layer of stem minimize transpiration.
Mountain region: Most of the trees in cold mountains are cone shaped. The leaves are very thin
and needle-shaped to slide off the snow and rain water immediately.
Animals in mountain areas have long thick skin to protect themselves from cold climate They
possess strong hooves to run easily.
Grasslands: Lions living in the forests possess skin colour so as to match their environment.
They hide themselves in grasslands to catch their prey. They possess strong claws and teeth to
tear the food. They have sharp eyesight.
Deer possess long ears to have sharp hearing sense. Deer possess eyes on the side of its head
which makes it look in all directions. They have long legs to run fast.
Aquatic Habitat: All the fresh water and marine water bodies are included under aquatic habitat
Fish possess have streamlined bodies, which reduce friction and allow them to move freely in
water.
Sea animals like the octopus and the squid do not possess streamlined body as they stay deep
inside the ocean. They have the ability to make their body streamlined when they move in the
water.
Aquatic animals possess gills that help them to absorb the dissolved oxygen from
water. Dolphins and whales possess blowholes to breathe in air from atmosphere directly.
Aquatic plants have much smaller roots which are mostly free floating. Stems are long and
light. Leaves in submerged plants possess ribbon - like leaves which allow the plants to bend
themselves in the direction of the flowing water.
Frogs are amphibious in nature. i.e a frog can live both in water and on land. Frogs have strong
hind legs to hop on land and webbed feet to swim in water. Frogs also have a protective
membrane called the nictitating membrane on their eyes.
Characteristics of Living Things
All the forms on earth can be classified into living organisms and non-living materials. Living
organisms exhibit certain characteristic features which make them different from non-living
organisms.
Characteristics of living organisms
All living organisms exhibit certain characteristics of life.
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Living things require food
Living things exhibit growth
Living things perform respiration
Living things excrete
Livings Things move
Livings Things respond to stimuli
Livings Things Reproduce
Livings Things Die
Living things require food
Livings things require food to survive and grow. Food makes the body grow faster, and gives
energy to the body to help it perform the life activities.
Plants are considered to be autotrophs. The type of nutrition they exhibit is called as autotrophic
nutrition. Plants synthesise their own food from raw materials like carbon dioxide and water in
the presence of sunlight and chlorophyll by the process of photosynthesis. Carbon dioxide is
taken from the atmosphere through small pores called as stomata. Water is absorbed from the
soil by roots.
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Stomata are small pores on the surface of the leaf. The stomata contain guard cells that regulate
the opening and closing of the stomata. They are opened only when the plant needs carbon
dioxide for photosynthesis. They even release excess water by the process of transpiration.
Chlorophyll is the green coloured pigment present in the chloroplasts of the leaf. It is responsible
for the absorption of sunlight required for photosynthesis.
Animals depend on plants for their food. Bigger animals depend on smaller animals for food.
Animals are called as heterotrophs and they exhibit heterotrophic nutrition. Based on the type of
nutrition, heterotrophs are classified into holozoic forms, parasitic forms, saprophytic forms and
symbiotic forms.
Living things exhibit growth
As living things take in food to obtain energy. Energy is necessary for growth. Organisms
increase in height, weight etc. to exhibit growth. Living organisms have different stages of
growth in their life. Organisms grow from birth till death. At some stages of life, growth is rapid
and during others, it is very slow. Growth in living organism is an irreversible change. Animals
are born as small forms which later grow and reach adulthood. Then they become old and die
after sometime. Plants also grow, reproduce mostly by producing seeds during their lifetime and
die.
Living things perform respiration
Respiration is the process of breathing in oxygen and giving out carbon dioxide. Respiration
takes place in every cell and is called as cellular respiration. Oxygen is necessary to break up
food and produce energy from it. Different animals possess different organs for respiration.
Human beings respire through lungs. Lungs are spongy structures made up of special cells called
as alveoli. Alveoli are lined by thin membranes which perform gaseous exchange. Even plants
respire only in the night through small pores called as stomata.
Respiration in plants takes place during night. Stomata are the small pores seen on the surface of
the leaves. They open and close to exchange gases from the environment. Oxygen is taken in
from the environment and carbon dioxide is released into the environment during the process of
respiration.
Livings things excrete
The process of eliminating wastes from the body is called excretion. Plants eliminate harmful
waste substances in the form of secretions such as resins and gums. Animals possess different
organs for excretion. Animals excrete their wastes in the form of ammonia or urea or uric acid,
carbon dioxide and certain salts.
Livings things move
Even though plants are livings organisms, they cannot move as their roots are fixed firmly to the
soil. So, they require lot of strength in their cell wall. It is strong and provides support to the
plants during bad (adverse) conditions like strong wind, rainfall etc. Plants exhibit movement
being at the same place. Stems bend towards sunlight. Roots grow towards earth. Opening and
closing of flowers is also a type of movement. In some plants, leaves droop during night time
and open during daylight. Animals can move from one place to another in order to escape from
adverse climatic conditions.
Livings things respond to stimuli
Stimulus is the change in the immediate environment of a living organism. Every living thing
responds in some way or the other to stimuli. Plants respond to environmental stimuli like light.
Plants grow towards light. Roots in plants grow away from the light. The response in plants to
stimulus can be observed easily. e.g. Touch-me-not plant. Some animals like cockroach respond
to the environmental stimuli like light.
Livings things reproduce
All livings things reproduce. Some animals lay eggs, while others reproduce by giving birth to
young ones. Plants produce seeds that can germinate into new plants. Some plants do not
produce seeds but give rise to new plants in different ways.
Livings things die
All livings things must die one day or the other. As an organism grows, it undergoes many
changes during its lifetime. Finally, it undergoes ageing process and dies after sometime.
Transportation and Distances
Evolution of Transport
Before the invention of the wheel, the only means of transportation was walking. For
transporting goods, people used animals like donkeys, horses, mules, elephants, oxen, sled dogs
and bison. Boats were used as a means of transportation on water. The earliest boats were simple
logs of wood with a hollow cavity.
The oldest wheel was discovered in Mesopotamia, which was believed to be over 5,500 years
old. Carts fixed with wheels were invented around 3,500 BC, according to some historians. After
the invention of the wheel, man started using animals to pull vehicles that moved on wheels, and
thus, bullock carts and chariots came into existence. The invention of the wheel revolutionised
transport and wheel design was improved over thousands of years.
Till the beginning of the 19th century, people depended on animals for transportation of goods.
Animals were used to pull vehicles that moved on wheels. Popular vehicles, like the bicycle,
were invented in the late 18th century. The first bicycles did not have any brakes. It was up to the
rider to control the speed or stop the bicycle with his feet. Later on, motors were fitted to
bicycles, and thus, mopeds came into existence. Further research and development led to the
invention of the motor car.
The steam engine and the rail road were invented in the 19th century. The invention of the steam
engine introduced a new source of power for transportation. Rail tracks were made for steamengine-driven carriages and wagons to transport goods. Apart from these, motorised boats and
ships were used as a means of water transport. Roads, rail roads and water remained the major
means of transport for a very long time.
The Wright brothers invented the airplane and gave the world another means of transport –
airways. Electric trains, monorails, supersonic aeroplanes and spacecraft are some of the
contributions of the 20th century to transportaion. One of the most exciting developments in
travel is the flying train. It is referred to as the flying train because it does not touch the rails as it
moves. Huge magnets keep the train suspended in air. In his effort to explore the universe, man
has even invented the spaceship to travel in space and stepped into the space.
There are various means of transport, such as road, rail, water and airways. The mode of
transport can be chosen depending upon the distance to be travelled and how fast one wants to
get to the destination.
Evolution of Standard Units of Measurement
Before the metrics for measurement were developed, people used several different means to
calculate distance and length. For instance, a carpenter would measure the length of wood using
his palm, fingers or arm. Similarly, a cloth merchant would measure the length of cloth against
his outstretched arm. Foot length or palm length were commonly used as non-standard units of
measurement. The base measurement for the pyramids is the cubit, which was formulated by the
Egyptians. A cubit was measured on the arm, from the point where the elbow bends, to the tip of
the middle finger. One cubit is approximately equal to 18 inches. The inch was invented by the
Romans.
Scientists all over the world felt the need for uniformity in the standards for the measurement of
lengths and distances. In order to avoid confusion in measurements, the French created in 1970
the metric system, which is a standard for measurement. A further development to ensure
uniformity in the measurement of lengths and distances, and other quantities, was a standard of
measurement called the International System of Units or SI units. The SI unit of length is the
metre (m). The multiples and submultiples of metre are given below.
Multiples:
1 decametre (dam) = 10 m
1 hectometre (hm) = 100 m
1 kilometre (km) = 1000 m
Submultiples:
1 m = 10 decimetre (dm)
1 m =100 centimetre (cm)
1 m = 1000 millimetre (mm)
Large distances are measured in kilometres. The length and type of an object determines the kind
of measuring tool that can be used.
Measuring Length and its Accuracy
Length is one of the fundamental physical quantities. A ruler is used to measure the length of an
object. It is also used to measure the length of a straight line. A non-stretchable string or thread is
used to measure the length of a curved line.
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Procedure to Measure the Length of an Object (or) a Straight Line
First place the ruler along the edge of the object whose lengthis to be measured, with the zero
mark of the ruler placed at one end of the object.
On the ruler, note the reading at the other end of the object.
This gives the measure of the length of the object.
The same procedure can be followed to measure the length of a straight line.
Procedure to Measure the Length of a Straight Line Using a Damaged Ruler
Place the broken or damaged ruler along the edge of the object whose length is to be measured in
such a way that any visible mark coincides with one end of the object.
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Now note the reading on the ruler at the other end of the object.
The difference between the two readings gives the length of the object.
Procedure to Measure the Length of a Curved Line
Take a non-stretchable string or a thread and tie a knot at one of its ends.
Place the knotted end of the thread at one end of the curved line.
Holding the thread steadily with your fingers, stretch it along the curved line until you reach the
other end.
Now make a mark on the thread where it reaches the other end.
Finally, place the thread along a metre scale and measure the length between the knot and the
marked point.
This gives the length of the curved line.
When noting the reading on a ruler, you should look at it with the eyes directly above the
reading, and not in an oblique way. Otherwise, you will not be able to note the reading
accurately. If the zero mark of the ruler does not coincide with the first end of the object, then the
difference between the readings at the two ends gives the length of the object.
Rest and Motion
Rest
A body is said to be at rest if its position does not change with time with respect to an observer
(or a reference point). For example, the chairs of the dining table are at rest with respect to the
dining table; the passengers sitting in a moving bus are said to be at rest with respect to the driver
of the same bus, because their positions do not change with respect to the driver.
Motion
A body is said to be in motion if its position changes with time with respect to an observer (or a
reference point). The passengers sitting in a moving bus are said to be in motion with respect to
an observer standing outside the bus, Similarly, the blades of a rotating fan, the hands of a
working wall clock, a spinning top and satellites are all in motion with resect to a fixed axis .
Rest and motion are relative terms. A body may seem to be at rest with respect to one
object, but may appear to be in motion with respect to another object. If you consider a
passenger in a moving train, he is at rest with respect to his co-passengers, but is in motion
with respect to an observer standing on the ground.
Types of Motion
There are different types of motion. They are rectilinear motion, circular motion and
periodic motion. Rectilinear motion is the motion of a body along a straight line. For
example, a train moving on a straight track and a stone falling from a height are in
rectilinear motion. Circular motion is the motion of a body that moves along a circular
path. Examples of bodies in circular motion are the rotating blades of a fan, a child sitting
on a merry-go-round, and the tips of the hands of a clock.
Periodic motion is the motion that repeats itself at regular intervals of time. Every
object executing uniform circular motion can be said to be executing periodic motion. The
motion of the pendulum in a pendulum clock, the motion of a swinging cradle and the
motion of the needle in a sewing machine are some examples of periodic motion.
Sometimes an object can display combinations of different types of motion. For example, a
moving car which moves straight on the road displays rectilinear motion but at the same
time the wheels of the car which are moving in circles display circular motion. So the
wheels of a moving car execute both rectilinear and circular motions. In a sewing machine,
the tip of the needle is in rectilinear motion as well as in periodic motion.
Types of Media
Luminous Objects
Objects that emit light on their own are called luminous objects. The light emitted by luminous
objects enables us to see things around us. Examples of luminous objects are a tubelight, the sun,
a lit candle, a glowing bulb, a bonfire and a lit torch.
Non-luminous Objects
Objects that do not emit light on their own are called non-luminous objects. The light emitted by
luminous objects falls on non-luminous objects, and then bounces back to our eyes, which
enables us to see non-luminous objects. Examples of non-luminous objects are the moon, a book,
a pen, a wooden box, a cupboard and a chair.
Light travels in a straight line, and its rays represent the path of light. The material that light
passes through is called a medium.
Opaque Objects
Objects through which we cannot see anything are called opaque objects. A medium that does
not allow light to pass through it is called an opaque medium. Examples of opaque objects are a
pencil box, a wooden screen, a book, a towel, a ceramic plate and chart paper. Most objects in
our surroundings, like buildings and trees, are opaque objects.
Transparent Objects
Objects through which we can see clearly are called transparent objects. A medium that allows
all the light incident on it to pass through it is called a transparent medium. Examples of
transparent objects are a plain glass plate, a clear plastic scale, windowpanes, a soap bubble, and
pure water.
Translucent Objects
Objects through which we cannot see the objects on the other side clearly but can see some light
are called translucent objects. A medium that allows only a part of the light incident on it to pass
through it is called a translucent medium. Examples of translucent objects are ground glass,
frosted glass, smoked glass, sun glasses and butter paper.
Shadows and Pin Hole Camera
Shadow
A shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
A shadow is formed only when a light source, an opaque object and a screen are present. For
example, during a lunar eclipse, we see a part of the earth’s shadow on the surface of the moon.
This happens when the earth, the sun and the moon are in a straight line, with the earth between
the sun and the moon. Here, the sun acts as the light source, the earth as the opaque object, and
the moon as the screen. Shadows are formed due to the rectilinear propagation of light. The size
and shape of the shadow depends on the position and orientation of the opaque object between
the source of light and the screen.
Whatever be the colour of the object, its shadow is always black because the shadow region is
not illuminated by light. The length and shape of a shadow depends on the object by which it is
formed. In the olden days, shadows caused by objects placed in the sun were used to measure
time. Such a device is called a sun dial. The Jantar Mantar in Jaipur consists of a sundial or
Samrat Yantra, which can be used to tell the time, as its shadow moves visibly at one millimetre
per second, or roughly six centimetres every minute.
Pinhole Camera
The pinhole camera works on the principle that light travels in a straight line. The image formed
by a pinhole camera is real, inverted and diminished in size when compared to the original
object. Pinhole cameras are inexpensive and are easy to make. An eclipse can be viewed using a
pinhole camera.
Making a Pinhole Camera
• Take two rectangular boxes that fit into one another without leaving any gap.
• Cut open one side of each box.
• Make a small hole in the larger box at the centre of the closed end opposite to the side that
has been cut open.
• Cut a square of side five centimetres in the smaller box in the closed end opposite to the
side that has been cut open. Cover this square with tracing paper.
• Finally, slide the smaller box into the larger box, ensuring that the pinhole and the tracing
paper are in line with one another, but at the opposite ends.
• Slide the smaller box to adjust the focus so that you can capture the image of any object you
want.
This is the basic structure of the pinhole camera. However, the developed form of a pinhole
camera uses photosensitive film instead of translucent paper to capture images. The film can be
developed later to obtain photo prints. Nowadays, of course, we use digital cameras that store
images in a computer chip. However, the basic principle of capturing the image remains the
same.
Differences between A Shadow and A Pinhole Camera Image
• A shadow is in general black and does not give the details of the object. The image formed
by a pinhole camera is colourful and contains all the details of the object.
• A shadow can be bigger than the object whereas the image formed by a pinhole camera is
always smaller than the object.
• The shape of a shadow varies depending on the orientation of the object between the light
and screen while the pinhole camera image is always inverted and has the same shape as the
object.
Mirrors and Reflection
Summary
HD11:59
LearnNext Lesson Video
Reflection is the phenomenon in which light incident on an object bounces back into the same
medium through which it was propagating while incident on the object, following some laws.
The path along which light propagates is called a light ray. The light ray that strikes an object is
called the incident ray. The ray that bounces back from the object into the same medium is called
the reflected ray.
Types of Reflection
The phenomenon of bouncing back of light after falling on the surfaces of the objects is called
reflection of light.
The reflection of light is of of two types, they are:
1. Regular reflection or Specular reflection
2. Diffused or irregular reflection.
In general, reflection is the process where the light incident on an object bounces back into the
same medium. This happens when light is incident on a translucent or an opaque medium. When
light is incident on a transparent medium, all the incident light passes through the medium, and
reflection does not take place. In the case of translucent medium, a part of the incident light is
reflected, and the rest is transmitted through the medium.
We get light from a luminous object, which we refer to as a source of light. If the size of the
source of light is very small, then we call it a point source of light. If the size of the source of
light is considerable, then we say it is an extended source of light. Light rays from a point source
of light travel in all directions, moving away with time. Such a beam of light is called a divergent
beam of light.
If the light source is an extended source, then we get a parallel beam of light from it. Consider a
parallel beam of light from an extended source, incident on a plane surface like a plane mirror.
As the beam of light is parallel, and the surface on which the beam is incident is a plane surface,
the angle made by each ray with the normal at the point of incidence on the surface is equal,
which implies that the angle of incidence of all the rays is equal.
Each ray of light follows the laws of reflection irrespective of whether it is from a parallel beam
or not. According to the laws of reflection, the angle of reflection is equal to the angle of
incidence.
Thus, for every ray of light incident on the mirror, the angle of reflection is equal to its angle of
incidence.
Regular Reflection
As the angles of incidence of a parallel beam of t all the ligh rays are equal for a smooth plane
like a plane mirror,the angles of reflection of all the rays equal. This implies that all the reflected
rays are parallel. When all the reflected rays, reflected from a given surface, are parallel then it is
called regular reflection.
Diffused Reflection
If the surface is not a plane surface, then the reflected rays are not parallel to each other. In such
a case, the reflection is called diffused reflection.
The diffused reflection occurs at the rough or un polished or the slightly polished non smooth or
rough surfaces.
As the rays of light falls on a rough surface at any angle of incidence then the angle of reflection
is equal to the angle of incidence.
Note:Laws of reflection are valid for both regular and irregular reflections of liht.
Mirror
A smooth plane surface that reflects the entire light incident on it is called a plane mirror. Light
incident on an object is reflected by that object. That reflected light is incident on the mirror, and
is reflected to our eyes. It is because of this reflection that we see images in a plane mirror. An
image is the likeness of an object carried and formed by light in a mirror. In other words, your
image is a reflection of yourself in the mirror. In ancient times, people mostly used pools of still
water, or water collected in a vessel as mirrors. The first man-made mirrors were in the form of a
polished stone made by using obsidian, a naturally occurring volcanic glass.
Mirrors change the direction of light incident on them. The image in a plane mirror is of the
same size and colour as that of the object. Moreover, the distance between the image and the
mirror is the same as the distance between the mirror and the object.
A periscope is an instrument used for observing objects from a hidden position. This instrument
is mostly used in submarines, and works on the concept of reflection in plane mirrors. Using
mirrors, it enables people in a submarine to view objects on the surface of the water.
A glass that acts as a mirror on one side and plain glass on the other is called a two-way mirror.
A two-way mirror is used when you want to observe people without letting them know that they
are being watched, for example, by police or in psychological institutions.
Differences between Images Formed by A Pinhole Camera and A Plane Mirror
Images formed by a pinhole camera are entirely different from the images formed by a
mirror. The image in a plane mirror is virtual, erect and is of the same size as the object, whereas
the image formed by a pinhole camera is real, inverted and is smaller in size when compared to
the object. Moreover, the distance between the image and the mirror is the same as the distance
between the mirror and the object whereas the distance between the object and the pinhole is not
the same as the distance between the pinhole and the image.
Comparison of Shadow and Mirror Image
The similarity between a shadow and an image is that neither of them can exist without light.
However, there are some differences between shadows and images. Shadows are black, whereas
images are colourful. Shadows of objects placed in the sun change in length with the position of
the sun through the day. Your shadow will be at its longest at dawn and dusk, whereas it will be
at its shortest at noon. An image in a plane mirror doesn’t change in size at all; it is always of the
same size as that of the object. An image in a mirror can be seen without a screen, whereas it is
mandatory to have a screen to form a shadow.
Electric Cell and Torch Bulb
Electric Cell
An electric cell is a device that supplies electrical energy to devices that function using
electricity. It provides electricity to a number of devices, such as toys, alarm clocks, pocket
radios and cameras. An electric cell consists of two terminals: a positive terminal and a negative
terminal. It has a cap, just under which there is a plus sign. This is the positive terminal of the
cell. At the other end of the cell, there is a flat metallic disc with a minus sign just above it. This
metallic disc is the negative terminal of the cell. These terminals of the cell can be used to
connect it to various devices. Inside a cell, there is dark powdery stuff, which is the chemical that
helps the cell to provide electricity to the device it is connected to. When a cell is connected to a
device, the strength of the chemical decreases. Finally, when the entire energy of the chemical is
spent, the device connected to the cell stops functioning. A rechargeable cell or a storage battery
can be recharged and can be used again.
Torch Bulb
A torch bulb consists of two terminals and a filament. The filament is a spirally wound wire
inside the bulb supported by two thick wires at its ends. When the positive and the negative
terminals of an electric cell are connected to the two terminals of a bulb, electricity passes
through the filament and it starts glowing. The terminals of the bulb are fixed in such a way that
they do not touch each other. In recent years, a different type of bulb has become popular - the
compact fluorescent lamp (CFL). It is an energy-saving bulb, which has a longer life than an
ordinary bulb.
Electric Circuit
Electricity needs a path to flow from the positive terminal to the negative terminal of an electric
cell. A connection that provides a path outside an electric cell, for the electricity to flow from
the positive terminal to the negative terminal of the cell, is called an electrical circuit. For
example, a bulb glows only when the positive terminal and the negative terminal of an electric
cell are connected to the two terminals of the bulb. If the wires from the bulb are connected to
the same terminal (either positive or negative), then the bulb does not glow. Sometimes, the bulb
may not glow even though the connections are properly made. This may be because the flow of
electricity is incomplete as the filament in the bulb is broken. A bulb with broken filament is said
to be fused.
A device that is used to stop the flow of electricity by breaking the circuit is called a switch.
Switches have wide range of applications. Some common types of switches are:
• Toggle switches, which are used in our houses.
• Pushbutton switches, which are used in the starter of a water pump.
• Joystick switches, which are used in the remote control unit of a toy car.
Electric circuit including a switch
Activity 1:
To connect a bulb to an electric cell, we will need:
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Four pieces of wire and
An adhesive tape
First, remove the plastic insulation from the ends of all the four wires, such that a small length of
the metal wire is exposed.
Fix the exposed end of one wire to the positive terminal of the cell. Fix the exposed end of anoth
er wire to the negative terminal of the cell. Now, fix the exposed ends of the other two pieces of t
he wires to the two terminals of a bulb with the adhesive tape. This is what the bulb and the elect
ric cell will look like with the wires attached to them.
We now connect one of the wires of the bulb to a wire from the electric cell. Then we connect th
e second wire from the bulb to the remaining wire from the electric cell. The bulb now starts glo
wing.
Activity 2:
Let’s connect all the wires to the positive terminal of the cell now. The bulb still doesn’t glow. It
is because the connection should be made in a specific way for the bulb to glow. Now let’s recon
nect it, the way we connected the first time. The bulb glows again. Electricity needs a path to pas
s from the positive terminal to the negative terminal of the cell.
When the positive and the negative terminals of an electric cell are connected to the two terminal
s of a bulb, the path is completed and the bulb glows.
A connection that provides a complete path for the electricity to pass from the positive terminal o
f the cell to its negative terminal, outside an electric cell, is called an electrical circuit.
At times a bulb in the circuit will not glow even though the connections are correct. The reason
could be a fused bulb.
A bulb is said to have fused when its filament breaks. When the filament is broken, there is a bre
ak in the flow of electricity through the terminals of the bulb. That is, the path required by electri
city to flow is broken. Hence, the bulb does not glow.
We need to disconnect one of the wires to switch off the bulb in the circuit that we just made. Bu
t then we’ll need to reconnect the wire manually to get the bulb to glow again. A switch in the cir
cuit will make it easy to switch the bulb on and off.
A switch is a device that is used to stop the flow of electricity by breaking the circuit. A switch e
nables us to break or complete a circuit on the click of a button.
Making a switch:
We need the followingt to construct an electric switch thermocol piece,
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A pair of thumbtacks,
A metal paper clip,
Four pieces of insulated wire,
An electric cell and
A torch bulb.
We start by creating the circuit. There will be one difference, though. We will leave one of the w
ires of the electric cell and the bulb unconnected.
We connect one end of the loose wire from the cell to a thumbtack, which is fixed on the thermo
col.
Now we connect one end of the loose wire from the bulb to another thumbtack fixed to the therm
ocol close to the thumbtack fixed earlier.
The distance between the two thumbtacks should be less than the length of the paper clip. The sw
itch is ready.
When we want to switch the bulb on, just bring the paper clip in contact with the thumbtack.
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This completes the circuit and the bulb starts glowing. To click it off, take the clip away from the
thumbtack.
Switches can be found in a variety of applications. A few common types of switches are:
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Toggle switch
Used in our houses.
Pushbutton switch
Used in the starter of a water pump.
Joystick switch
Used in the remote control unit of a toy car.
Electric Conductors and Insulators
Materials that allow electricity to pass through them are called conductors. Since metals are good
conductors of electricity, electrical wires are made up of metals. These conducting wires are used
to connect various components of an electrical circuit. Copper, silver, gold and aluminium are a
few examples of electrical conductors. Copper is the most commonly used material for making
connecting wires. Sometimes we get electric shocks because our bodies are also good conductors
of electricity.
Materials that do not allow electricity to pass through them are called insulators. Some common
insulators are glass, air, plastic, cotton, thermocol, wood and rubber. As insulators do not
conduct electricity they are used to protect us from the dangerous effects of electricity. Without
the help of insulators, the use of electrical appliances is impossible.
Tap water is a good conductor of electricity, but distilled water (water in it its purest form), acts
as an insulator. Distilled water is, therefore, used in batteries as an insulator.
We use various electrical appliances every day. The parts of the electric appliances that we touch
are covered with insulating material. For example, plugs and switches are covered with an
insulating material such as plastic, and the wire attached to the plug has a metal wire inside it,
which is a conductor. So conductors and insulators work hand in hand.
Water Cycle
Water occupies two-thirds of our earth. 97% of water available is salt water found in seas and
oceans. At about 3% is the fresh water available on earth. Most of it is in the form of icecaps.
Just at about 0.003% of fresh water is available as ground water, lakes, streams, rivers, water
vapour etc.
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Uses of water
70% of our body is made up of water. Water is essential for normal functioning of life processes.
Water is used for various activities such in agriculture, industries and domestic purposes. 70% of
fresh water is used for irrigating agricultural fields. 22% of water is utilised by industries. 8% of
water is used for domestic requirements.
Domestic activities include cooking, cleaning utensils, bathing, washing clothes and mainly for
drinking.
Ponds, wells, streams, lakes and rivers are the different sources of drinking water. Drinking
water is called as potable water. Oceans and seas supply water to other water bodies through
water cycle.
A variety of useful salts, like sodium chloride, calcium, magnesium and potassium are present in
saline water.
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States of water
Water exists in three different states. Water can occur in the solid state.
Solid state can be represented by ice, snow or hail. Water can occur in the liquid state.
Liquid state of water can be represented by river, rain or sea. Water can occur in the gaseous
state.
Gaseous state of water can be represented by water vapour.
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Three states of water are inter-convertible.
Solid form of water can be converted into liquid form by heating.
Liquid form of water can be converted into gaseous form by evaporation.
Gaseous form can be converted into liquid form by the process of condensation.
Liquid form can be converted into solid form by freezing.
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Water cycle
The cyclic movement of water from the atmosphere to the Earth and back to the atmosphere
through various processes is called as water cycle.
Different steps of water cycle include evaporation, transpiration, condensation, precipitation and
surface run-off.
a) Evaporation - The water present on the surface of oceans evaporates by the sun’s heat. This
process of conversion of water from liquid state to vapour state is called evaporation.
Evaporation also takes place from wet clothes, fields, ponds, lakes and rivers.
b)Transpiration - Plants take in water from the soil to prepare their own food and also for other
life processes. They release excess water into air in the form of water vapour by the process of
transpiration.
c) Condensation - The evaporated water is carried away by warm air. As the warm air moves
higher from the surface of the Earth, it starts to cool down. This water vapour condenses to form
tiny water droplets which float in air to form clouds or fog.
d) Precipitation - All these droplets collect to form bigger drops of water. Bigger water drops
come down ads rain by the process of precipitation. If the air is too cold, the water drops can
become snow or hail and may settle on the top of a mountain. When these snow or hail melts,
they can become part of a river or a stream.
e) Surface run-off – Some amount of rain water is absorbed by the soil and settles down as
ground water. Most of the rain water flows down the hills and mountains to collect into rivers,
lakes or streams. Rain also washes away the topmost layer of the soil into water bodies.
This circulation of water through all these different factors is called as water cycle.
Effects of Rainfall - Droughts and Floods
Water cycle plays an important role in maintaining the climate. Oceans absorb heat from the sun.
They provide warmth on the land. Water gets evaporated from the surface of oceans by
absorption of heat. Water vapour releases heat by cooling in the process of condensation. This
continuous absorption and release of heat in the form of heat maintains the constant climate of a
particular place.
Natural calamities
Natural calamities related to water are floods and droughts. These are uncontrolled conditions
during which floods and droughts prevailing affect an area or a region on earth.
a) Floods: The condition during which rain water being everywhere, even submerging the land
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is called as flood.
Floods are caused by rise in the water level in ponds and lakes due to heavy rainfall. The excess
rain water flows on to land causing floods. Floods make the soil water-logged.
Floods affect normal life by disturbing everything which comes in its way.
Floods wash out the living beings such as plants, fish and other animals etc.
Floods create water-logging in the soil bringing out stored air from the spaces. Organisms like
earthworms, ants, insects rats, rabbits, snakes living under soil get disturbed by floods.
Floods cause heavy loss to human life.
Floods damage different types of property.
Floods cause uprooting of trees. Floods wash away the crops.
Floods result in shortage of food supply.
Floods cause stagnation of water forming the breeding ground for many disease causing
organisms. Diseases can easily spread out during floods. These are called as water-borne
diseases.
Floods cause disruption of modes of transport and communication.
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Floods also disturb many kinds of food chains.
b) Droughts: Droughts are the conditions which involve abnormally long period of insufficient
or no rainfall.
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Droughts are caused due to lack of rains.
Drought condition results in drying up of wells, lakes, ponds and thereby creating water scarcity.
Droughts result in the evaporation of water from the soil leaving the soil dry and patchy.
Droughts result in mass death of plants and animals due to dehydration.
Droughts affect agriculture and lessen food production.
Droughts result in death of animals and birds which provide us animal products like milk, meat
and eggs. This scarcity of food results in the famine.
Droughts result in forest fires caused by enormous amount of heat from scorching sun.
Water conservation
Water is an essential natural resource. These exists no life without water. Water is so precious
that it has to be conserved.
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Avoiding water wastage is also a kind of water conservation.
Excess rain water running in the river is stored in huge and special structure called as dam.
Dams are huge structures built on rivers to hold back excess water. Dams prevent areas from
flooding by storing large amount of water.
Dams provide water for irrigating fields, domestic use and also drinking water for some areas.
Drinking water should not be wasted to water the plants.
Water bodies should not be polluted in order to get pure water.
Water should not be wasted during irrigation of fields. Modern methods like spraying, sprinkling
or drip irrigation should be used.
Water should be used judiciously to avoid wastage.
Destruction of trees should be controlled to increase the rainfall.
Rain water harvesting
Rain water harvesting includes collection and storing of rain water from the roofs of houses and
huge constructions. This is also called as roof-top rainwater harvesting. Constant use of fresh
water from the ground results in water scarcity. Rain water harvesting increases the level of
ground water.
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Technique involved in rain water harvesting
Rain water is collected at the roof top.
It is allowed to flow into pipes.
It is filtered through wire mesh.
It is allowed to pour into an underground tank setup to store rain water. These tanks contain
layers of sand, gravel, charcoal that will filter the dirt and other impurities from rain water.
This water seeps back into ground slowly to increase the level of ground water table.
of concrete floor which does not allow the rain water to seep into the ground.
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All about Air
Air
Air is present everywhere on earth. Air is present as a thick blanket surrounding the surface of
the earth.
The layer of gases around the earth is called as atmosphere.
The atmosphere is dense at the surface of the earth and becomes thinner as one moves up.
Air is essential for all living beings. It supports life on earth.
Air is utilised by all the living organisms like plants, animals and microorganisms.
Air cannot be seen but is felt when it moves.
The movement of air is called breeze or wind depending on its velocity or speed.
Air fills in the empty space available every where.
We all breathe in air. Breathing is an essential part of respiration. We breathe in oxygen rich air
and breathe out carbon dioxide rich air.
Components of air
Air contains mostly nitrogen and oxygen. Nitrogen occupies 78% of the air. Oxygen occupies
21% of the air. 1% of the air is made up of carbon dioxide, other gases, water vapour, dust
particles etc.
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Nitrogen: It is a lightest colourless, odourless gas. It generally occurs in its diatomic form N2.
Nitrogen is used to control combustion.
Nitrogen is used by plants and animals to synthesise proteins in the body.
Nitrogen cannot be directly used by plants or animals. It has to be fixed into its nitrate or nitrite
forms.
Nitrogen is used to manufacture fertilisers to increase soil fertility.
Nitrogen is used to manufacture ammonia used for in many industries.
Nitrogen oxidation of stored food in packets.
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Oxygen: It is a chemical element in the form of gas. Mostly it is diatomic, made up of two
atoms. O2 is the molecular oxygen.
Oxygen is taken directly from the air by organisms living on land.
Oxygen helps in oxidising the food eaten by organisms to release energy.
Aquatic organisms take in oxygen dissolved in water.
Oxygen is required for combustion.
Oxygen in the form of ozone helps in protection of living organisms from dangerous UV rays
coming out from the sun.
Oxygen is used as a fuel in rockets.
Oxygen stored in the cylinders is used to provide artificial respiration to patients in the hospital.
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Carbon dioxide: It is the gas which is made up of one carbon atom combining with two atoms
of oxygen.
CO2 is used by plants in synthesising their food by the process of photosynthesis.
CO2 is used in fire extinguishers.
CO2 is used in storing soft drinks.
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Inert gases: These are also called as noble gases. They occupy a negligible percentage in air.
Argon is used to fill the bulbs to prevent their filament.
Helium is used in providing low temperatures.
Neon is used to fill special bulbs called as neon signs.
Radon is used in treating cancer patients.
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Water vapour: It is a form of water present as gas in the air.
Amount of water vapour in the air varies with sun's heat.
Hot sun can evaporate more amount of water and convert it into water vapour.
It helps in the formation of clouds which later can come down as rain.
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Dust and smoke: Air contains some amount of dust and smoke in it.
Dust and smoke are contributed by vehicles and industries releasing them.
These are harmful to human beings and can cause many respiratory diseases.
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Oxygen-Carbon dioxide levels
Oxygen and carbon dioxide levels in the air are maintained by different processes like respiration
and photosynthesis.
Respiration involves utilisation of oxygen from air by living organisms and releasing carbon
dioxide into air. It occurs in all living organisms.
Photosynthesis involves utilisation of carbon dioxide from air and release of oxygen into the air.
Carbon dioxide is replenished by the process of respiration and oxygen is replenished by the
process of photosynthesis.
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Properties of air
Air is transparent. Air is a transparent medium which allows light to pass through it. The objects
are seen clearly through air.
Air is colourless. It is not visible.
Air can be felt when it moves fast. Moving air is called as wind.
Air occupies space. Air is present everywhere. Air can be displaced by water.
Air exerts pressure.
Air can be compressed and filled into a container.
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Other uses of air
Air is used to rotate wind mills, which can lift water.
Wind energy is a renewable form of energy.
Air is also used to rotate wind mills which can generate electrical energy by aerogenerators.
Air is used in sail boats
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Garbage Disposal and Vermicompost
Garbage
Waste accumulated in our surroundings and is ready for disposal is called as garbage. Garbage is
the solid waste which includes domestic wastes, municipal wastes and industrial wastes.
Domestic wastes are the wastes from our houses.
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Municipal wastes are the wastes from schools, offices, roads and shops.
Industrial wastes are the wastes discarded from industries and small factories.
Garbage Disposal
A large, low-lying area used to dispose garbage is known as a dump.
A garbage dump is also used as landfill. Garbage collectors collect waste and then dispose it at
garbage disposals.
Garbage dumps have flies, cockroaches and mosquitoes, and later turn into breeding grounds for
micro-organisms which may cause diseases. This is the reason why garbage dumps are usually
located on the outskirts of a city.
On a long run when garbage mixes with soil, it takes a longer time to decay making the soil
loose.
Burning of agricultural wastes like dried leaves, husk etc. releases smoke and harmful gases into
the atmosphere. These harmful gases may cause respiratory diseases.
Components of garbage
Domestic wastes can be of two types namely, dry wastes and moist wastes. Wastes are collected
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in two separate types of bins.
Blue bins are used to dump recyclable wastes which include glass pieces, glass bottles, plastic
waste, old batteries, polythene bags etc.
Green bins are used to dump vegetable and fruit peels, food remains, tea leaves, egg shells,
leaves, hair, tissue papers etc.
a) Dry wastes or non-biodegradable wastes: Dry wastes include newspapers, metallic waste,
plastic pieces, broken glass pieces, wooden blocks, waste rags. These wastes are to be discarded
into blue bins provided by the municipality. Dry wastes can be recycled and reused. At regular
intervals of time they are taken to recycling plants for the process of recycling.
b) Moist wastes or biodegradable wastes: These are the wastes which come from our kitchen.
They include food remains, vegetable peels, fruit peels, garden waste. These are discarded into
green bin provided by municipality. These can be composted to obtain manure. Moist wastes are
also used to fill the low lying areas by converting them into landfills.
Management of biodegradable wastes
Wastes can be decomposed and converted into organic manure by different processes.
a) Composting involves conversion of biodegradable wastes into organic manure by burying
them in the compost pits. These wastes are decomposed by the action of bacteria and fungi. It is
a slow and simple process. It is a cheap process. It causes no harm to the environment.
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Advantages of compost
Compost increases the fertility of the soil.
It increases the amount of trace elements copper, manganese, molybdenum in the soil which are
essential for growth.
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Compost increases water holding capacity of the soil. It also improves the texture of the soil.
b) Vermicomposting involves degradation of organic matter into fertile manure by using special
type of earthworms called as red worms. The nutrient rich manure is called as
vermicompost. The process of preparing manure with the help of red worms is called
vermicomposting. The red worm is a type of earthworm that lives in the soil rich in organic
matter. Organic soils are rich in nitrogen and carbon with plenty of moisture and microbes.
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Method of Vermicomposting
A vermicomposting pit is made with a wooden box or big cement rings.
A mesh is spread at the bottom of the pit.
Vegetable waste, fruit waste, waste paper which is not shiny or coated with plastic, is spread
over the mesh.
Water is sprinkled to create moisture so that the red worms can live.
A vermicomposting pit takes nearly two to four weeks to completely convert waste into manure.
The red worms possess a special structure called gizzards with which they grind food material. A
red worm eats food equal to its weight every day. Their castings are used as rich manure. This is
called as vermicompost.
Vermicompost should be removed from the pit and dried before use.
Vermicompost can be made in 3 -4 weeks.
Red worms do not survive in too hot or too cold conditions.
c) Landfill is another method of managing biodegradable wastes. Landfills are large areas used
for waste disposal. Garbage thrown into landfills decomposes very slowly and makes the soil
loose. As the landfill becomes full, the garbage decomposes and mixes with the soil. This land
can be cleaned and converted into a park.
Recycling Paper and Plastics
Waste management
Waste management includes collection of wastes, segregation of wastes, recycling of wastes and
treatment of wastes for disposal.
Management of non-biodegradable wastes
As non-biodegradable wastes cannot be decompose by bacteria, these wastes can be managed by
following 3R principle – Reduce, Reuse and Recycle.
Reduce: We have to reduce the amount of waste generation by lessening the use of disposable
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items.
Ball point pens should be replaced by fountain pens, old news papers should be used instead of
plastic bags.
Waste can also be reduced by consuming the necessary amount leaving out less waste.
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Reuse: Many items can be reused for other purposes. Small bottles can be cleaned and used to
sore food items in the kitchen.
Soft drink bottles can be reused by refilling the same.
Used clothes can be donated to poor and needy instead of throwing them.
Electronics can be donated to others.
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Recycle: It is the essential method to minimise the waste. It also helps in using resources in best
way.
It is important to reuse things than discarding them as waste.
Materials like glass pieces, metals, plastics, paper etc. can be recycled to make new ones.
a) Recycling of plastic: Plastic items should be recycled to reduce the pollution they cause in the
environment. Plastics which can be recycled are called as recyclable plastics.
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Harmful effects of plastics
Though plastic is easy and comfortable to use, it is very harmful in terms of health and
environment.
Polythene bags are one kind of plastics which are non-biodegradable and cause environmental
pollution.
Plastics undergo a process known as photo degradation, in which they break down into smaller
and smaller toxic particles.
These particles contaminate soil and water and enter the food chain when eaten accidentally by
animals like cows.
Polythene bags are very dangerous that they can cause the death of the cattle.
Plastic materials discarded into aquatic resources cause death of huge number of aquatic
organisms.
Plastics in the form of polythene bags are also responsible for the clogging of drainage systems
in cities and towns.
Plastics take several years to decompose. Plastic is used in various forms in our daily life.
Plastics are not suitable for storing cooked food as they emit harmful chemicals when they are
exposed to high temperatures. Using plastics causes health problems.
Burning of plastics emits harmful gases which cause cancer in living beings. Hence, plastics
should be disposed in the right way.
Plastics that do not contain the chemical, BPA, are usually licensed for storing food items.
Plastics thrown casually get into drains and sewage often blocking the way and cause waterlogging.
Measures to reduce dangerous effects of plastics
Reduce, reuse and recycle plastics.
Carry jute or cloth bags for shopping.
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Do not store food items in plastic bags.
Do not burn plastic items.
Recycle plastics so that new plastic items can be made.
b) Recycling of paper: Paper is recycled in industries to regenerate new paper. Paper that is
suitable for recycling is called scrap paper.
You can recycle old newspapers, magazines, notebooks and used envelopes.
Waxed papers, oil-soaked papers, paper contaminated with food, carbon paper, thermal fax
paper, plastic laminated paper, stickers cannot be recycled.
Steps involved in recycling paper
Paper is torn into small pieces.
Soak these pieces in water for a day.
Make a thick paste and spread it on a net or sieve.
Let water drain off completely.
Use an old cloth or newspaper to remove the extra water from the paste and dry it.
Use this paste to get beautiful patterns.