Select Board & Class

Chapter 10: Respiration in Organisms
Cellular Respiration
  • It is the process in which food is broken down in the cell to release energy.
  • It occurs in the cells of all living organisms.

Two types of Respiration
  • Aerobic respiration – It is the process of breakdown of food in the presence of oxygen.
    ⚬ It occurs in all organisms.
    ⚬ It leads to production of carbon dioxide, water, and energy.
       Glucose oxygen CO2 + Water + Energy
  • Anaerobic respiration – It is the process of breakdown of food in the absence of oxygen.
    ⚬ Yeast, bacteria, human muscle cells, etc. respire anaerobically.
    ⚬ In yeast cells, anaerobic respiration leads to production of alcohol and carbon dioxide.
     Glucose oxygenwithout Alcohol + Energy + CO2
  • During heavy exercise, our muscles respire anaerobically to provide energy to muscle cells.
    This leads to accumulation of lactic acid that causes muscle cramps and thus, pain in body.
    Glucose oxygenwithout Lactic acid

  • It is a continuous process that involves inhalation and exhalation.
    ⚬ Inhalation – Process of taking in oxygen-rich air in the body
    ⚬ Exhalation – Process of giving out carbon dioxide-rich air into the atmosphere
  • Nostril is the opening through which we inhale air.
  • Nasal cavity filters and purifies the air that we breathe in.
  • Parts of Respiratory system
  • During inhalation:
    ⚬ Diaphragm moves down.
    ⚬ Ribs move upwards and downwards increasing the space in the chest cavity.

  • During exhalation:
    ⚬ Diaphragm moves to its original position.
    ⚬ Ribs move down and inward reducing the size of chest cavity.

Breathing rate
  • It is the number of times a person inhales and exhales.
  • An increased physical activity increases the rate of breathing.
  • Breathing rate is least when we are at rest. It is at maximum when we run very fast so as to provide more oxygen to the body.
  • The normal breathing rate per minute in an average adult (at rest) is 15 to 18 times.
  • The percentage of oxygen in inhaled air is 21% while the percentage of carbon dioxide is 0.04%.
  • The percentage of oxygen and carbon dioxide in exhaled air is 16.4% and 4.4% respectively.

Respiration in land animals
  • Respiration in cockroaches takes place through spiracles. The spiracles are connected to a network of tubes, called tracheae, for gaseous exchange.
  • Earthworms breathe through the surface of their moist skin.
  • In animals like cows, dog, buffaloes and cats, the respiratory organs and the process of breathing are similar to those in human.

Respiration in aquatic animals
  • Frogs respire through both lungs and their skin.
  • Fishes have special structure called gills for breathing.

Respiration in Plants
  • Stomata help in gaseous exchange.
  • Roots of plants respire through air spaces present in the soil.Chapter 18: Wastewater Story
❖ Water mixed with waste matter is known as waste water.
❖ Cleaning of water is the process of separating pollutants from the wastewater before it is released into a water body or is reused.
❖ Sewage is the wastewater carried away in sewers or drains.
❖ It is a mixture of various contaminants, which include the following.
• Suspended solids
• Organic impurities such as animal waste, urine or human faecal, pesticides, kitchen waste, etc.
• Inorganic impurities such as chemicals (nitrates, phosphates, etc.)
• Nutrients such as phosphorus and nitrogen
• Disease-causing bacteria and other microbes

Sewage treatment plant
• It reduces the pollutants in waste matter.
Sludge is the end product of sewage treatment. It is a thick, viscous matter that settles at the bottom of the tank.
• Sludge is decomposed by anaerobic bacteria to form biogas. Biogas is used as fuel or to produce electricity.
• Dried sludge is used as manure to increase the fertility of soil.
• Chemicals such as chlorine and ozone are used to disinfect water before releasing it into the distribution system.

House keeping practices to minimize addition of pollutants to water
• Always throw oil and fats in dustbins.
• Do not throw chemicals such as paints, solvents, insecticides, etc. into drains.
• Do not throw used tea leaves, food remains, cotton, etc. into drains..

Disease-causing microbes
• Poor sanitation and contaminated water causes diseases such as cholera, typhoid, meningitis, hepatitis, etc.
• Untreated human excreta may cause water and soil pollution.

Methods of sewage disposal
• Use low cost onsite sewage disposal systems such as septic tanks, chemical toilets, compositing pits, etc. to improve sanitation.
• Maintain sanitation at public places
• Do not throw litter in public places. Always use dustbins.
Chapter 17: Forests - Our Lifeline

Forest: It is a large area of land where a large number of tall trees, herbs, and shrubs grow naturally.

Canopy: It is the covering of large trees that serve as a roof to shelter an area or other plants in forests.

In a forest, the tall trees form the top layer, which is followed by shrubs, and then herbs, which form the lowermost layer of vegetation.

Importance of Forests
• It maintains the balance of nature. All the components of forests are interconnected with each other in the form of food chain.
• Decomposers increase the soil fertility. They convert dead plants and animals into humus. Humus is the topmost, dark brown, fertile layer of soil.
• Forests are called green lungs since they maintain the balance of oxygen and carbon dioxide.
• They improve the quality of air by absorbing the harmful CO2 gas from atmosphere and give out oxygen.
• Prevent soil erosion and natural calamities such as flood and drought.
• Forests are the habitats of wild animals.
• It also fulfils the basic human requirements such as food, shelter, water, and medicines.
• Forests act as natural absorbers of rainwater and maintain the water table, thereby preventing floods.

Causes of deforestation
• Construction of roads, buildings, and other increasing demands of humans
• Industrial development
• Clearing land for crops and for grazing cattle

Consequences of deforestation
• Erosion of soil
• Increase in earth’s temperature
• Disruption of water cycle
• Habitats of various animals get disrupted.
• Floods and droughts
Chapter 16: Water - A Precious Resource
22nd March - World Water day.

About 71% of the earth’s surface is covered with water. It is present as ground water, in seas, oceans, rivers, lakes, ice caps, and in atmosphere.

Forms in which water is found.
Solid − snow and ice
Liquid − oceans, lakes, rivers, and underground
Gaseous − water vapour in the atmosphere

Groundwater is an important source of water for living organisms.

Water table
The underground surface below which the ground is highly saturated with water. It varies from place to place.
Groundwater is the water found below the water table.
Infiltration is the process of seeping of water into ground. It recharges the ground water.
Aquifer is the underground layer that yields ground water for tube wells or hand pumps.

Causes of water depletion
Increasing population
Rapid growth of industrialization
Growing agricultural practices
Mismanagement of water
Rainfall increases the groundwater level.

Mismanagement of water
Wastage during supply of water through pipes
Leaking taps in building and at other places

Practices to conserve water
Water harvesting or Rainwater harvesting – The maximum amount of rainwater that falls on land is collected and can be used to recharge the groundwater.
Revive the traditional way of collecting water through Bawri
Adopt drip irrigation method to deliver water directly at the base of the plant.
As an individual, we ourselves should acquire the habit of turning off the taps while brushing.
Mop the floor instead of washing.

Water should be conserved since it is required for the important process of photosynthesis.Chapter 15: Light
Light always travels along a straight line. This is called rectilinear propagation of light.
Change in direction of light from an object is called reflection of light.
Any polished or shiny surface can change the path of light. A mirror, a shiny plate or spoon, water, etc. can change the path of light.
Reflection of light from an object makes the object visible.
The image formed by a plane mirror is erect, of the same size as the object, and at the same distance behind the mirror as the object is in front of the mirror.
The left of an object appears right and the right of the object appears left in the image formed by a plane mirror. This is called lateral inversion.
Two types of spherical mirrors

 The image formed by a convex mirror is erect and diminished. It is formed behind the mirror.
The image formed by a concave mirror can be erect as well as inverted, diminished as well as magnified, behind the mirror as well as in front of the mirror, depending on the distance of the object from the mirror.
Real image: The image that can be obtained on a screen.
Virtual image: The image that cannot be obtained on a screen.
The image formed by a convex mirror is always virtual.
The image formed by a concave mirror can be real as well as virtual.
Concave mirror is used as the reflector of a torch, dentist mirror, etc. It is also used in solar furnaces.
Convex mirror is used as a rear view mirror in vehicles.
Two types of lenses

 The image formed by a convex lens can be real as well as virtual, erect as well as inverted, behind as well as in front of the lens, depending on the distance of the object from the lens.
The image formed by a concave lens is virtual, erect, and in front of the lens.
White light is composed of seven colours − red, orange, yellow, green, blue, indigo, and violet.
A rainbow consists of all the seven colours of white light.
A prism splits white light into its seven constituent colours.
Chapter 14: Electric Current and its Effect
Symbols of Electric components
Electric component Symbol
Electric cell
Electric bulb
Switch in ON position
Switch in OFF position
Combination of cells: Positive (or negative) terminal of a cell is connected to the negative (or positive) terminal of the other cell. This combination is called a battery.

Heating effect of electric current:
When an electric current flows through a wire, the wire becomes hot.
• Devices such as kitchen heater, electric bulb, electric iron, electric fuse, water heater, etc. work on the principle of heating effect of electric current.
When the amount of current flowing through the element of an electric fuse exceeds the limiting value, it melts and breaks the circuit.

Magnetic effect of electric current: When an electric current flows through a wire, it behaves as a magnet and is called electromagnet.

Electric bell works on the principle of magnetic effect of electric current.

A compass needle shows deflection when brought near a current carrying wire.

An iron nail behaves as a magnet when a current is allowed to flow through a wire, which is wrapped around the nail.

Electromagnets can be used to separate iron objects from a heap of garbage.Chapter 12: Reproduction in Plants
Reproduction: It is the ability of living organisms to produce new individuals.
Two modes of reproduction
 Asexual reproduction – New plants are formed without seeds.
Sexual reproduction – Plants are involved in the formation of new plants with seeds.
Vegetative propagation is the ability of a plant to produce new plants asexually from roots, stem, leaves, and buds. Its a type of asexual reproduction. 
Stem propagation The surface of potato has several buds called eyes that develop into new plants.
Propagation by leaf The leaves of Bryophyllum have several buds at their margins that develop into tiny plants.
Propagation by roots   The roots of sweet potato, dahlia get detached from parent plant and give rise to a new plant.
Propagation by stems   Sugarcane, rose, money plant, etc. reproduce by stem cutting
Advantages of vegetative propagation
 Method of propagation for seedless plants such as sugarcane, potato, rose, etc.
 Exact copies of parent plant are produced.
 Large numbers of offsprings are produced in less time.
 Disease free plants can be propagated.
 Involves formation of a new individual from bulb-like projections called bud
 An example of an organism that reproduces through budding is yeast.
 It is a form of asexual reproduction where new individuals are formed from the fragments of parent body.
 Asexual reproduction in Spirogyra is by fragmentation only.
Spore formation
Bread mould, mushrooms etc. reproduce through spore formation.
 Spores are asexual reproductive bodies.
Sexual reproduction
A plant reproduces sexually with the help of flowers.
Stamen and pistil are the reproductive parts of a flower.
Stamen is the male reproductive part and pistil is the female reproductive part.
Bisexual flowers have both stamen and pistil. Examples – Lily, rose, hibiscus, mustard, petunia
Unisexual flowers have either stamen or pistil. Examples – Corn, papaya, cucumber, etc.
Stamen is the male reproductive part and consists of filament and anther.
 Anther produces numerous pollen grains.
 Pollen grains contain male gametes.
Pistil is the female reproductive part and consists of stigma, style, and ovary.
Ovary contains one or more ovules.
Ovules contain female egg cell called female gamete.

Pollination – It is the process of transfer of pollen from anther to stigma.
Pollens are transferred from one flower to another with the help of insects, birds, or wind.
Self Pollination: Occurs in bisexual flower or bisexual plants.
Pollen from the anther is transferred to stigma of the same flower.
Cross pollination: Pollens are transferred from the stamen of one flower to stigma of another flower of same plant or stamen of one flower of one plant to stigma of another flower of another plant of same species.
Occurs in both unisexual and bisexual flowers
Fertilization – It is the process of fusion of male and female gametes to produce zygote.
Zygote divides to form an embryo.
Events that occur after fertilization are:
 Fertilized ovule forms seed and ovary forms the fruit.
 Floral parts such as sepals, petals, stamens, style, and stigma fall off.

Seed dispersal: Distribution of seeds to new places is known as seed dispersal.

Importance of seed dispersal
Reduces competition between plant and plant seedlings
Increases the survival of plants in a new suitable habitat
Prevents overcrowding
Seed dispersal occurs with the help of animal, wind, water, and explosion.
Dispersal by animals
Birds and animals eat fruit and excrete the seeds away from the parent plant.
 Fruits such as Xanthium and Urena have hooks. These hooks cling to the fur of animals.
 Some seeds have barbs that get tangled in the animal’s body.
Dispersal by wind
Winged seeds of drumsticks and hairy fruit of sunflower are seeds that are dispersed by wind.
Dispersal by water
Coconut can float and is dispersed by water to new locations.
Dispersal by explosion
 The seeds of castor and balsam get scattered by bursting of fruits and they get distributed far from the parent plant.
Chapter 13: Motion and Time
Rectilinear Circular Periodic
Along straight line Along circular path Along same path in equal intervals of time
Speed=Total distance coveredTotal time taken
• If speed is same throughout a journey, then the motion is uniform.
If speed varies, then the motion is non-uniform.

Time measurement
Time-measuring device – watch or clock
Motion of hands of clock is periodic.
Motion of pendulum is periodic and oscillatory (to-and-fro).

Time period: It is the time taken by a pendulum to complete one oscillation.

Basic unit of time is second (s).
Basic unit of speed is metre/second (m/s).
Speed is measured by a speedometer.
Distance moved by a vehicle is measured by an odometer.
Distance covered = Speed × Time

Distance-time graph: A line graph is used for distance-time graph.
    x-axis → time, y-axis distance

Constant speed. Here, the speed of A is greater than that of B
Chapter 11: Transportation in Animals and Plants
Circulatory system is the transportation system of human body. It is composed of three major parts − blood, blood vessel, and heart.
Blood: Blood is a fluid that is pumped throughout the body.
⚬ Its function is to transport oxygen and nutrients to various parts of the body and ultimately to all cells of the body.
⚬ It contains plasma, red blood cells, white blood cells, and platelets.
⚬ Plasma is the fluid part of blood.
⚬ Red blood cell contains a pigment called haemoglobin which carries oxygen and transports it to all parts of the body.
⚬ White blood cell protects body against infections.
⚬ Platelets help in clotting of blood.
•  Blood vessels
Arteries carry oxygen-rich blood from the heart to various organs of the body.
◾ Pulmonary artery is the only artery that carries CO2-rich blood from heart to lungs.
The walls of arteries are thick and elastic in order to tolerate high pressure of the blood.
◾ Pulse is the rhythmic contraction and expansion of arteries with each beat of heart.
The number of beats per minute is the pulse rate.
A resting person usually has a pulse rate between 72 to 80 beats per minute.
Veins carry CO2-rich blood from various organs towards the heart.
They are thin-walled, non-elastic vessels that possess valves to prevent the backflow of blood.
Pulmonary vein is the only vein that carries oxygen-rich blood from lungs to heart.
Capillaries are thin-walled blood vessels. They connect arteries with veins.
• Heart 
⚬ Human heart is four chambered.
⚬ The upper two chambers are called atria while lower two chambers are called ventricles.
⚬ A muscular wall between the chambers prevents the mixing up of blood rich in oxygen and blood rich in carbon dioxide.
⚬ The rhythmic contraction and expansion of heart is the heart beat.
⚬ Stethoscope is used for listening to the heart sounds.
⚬ The human heart beats about 70 to 80 times per minute in an adult.
⚬ Dr. William Harvey discovered the circulation of blood.
⚬ Sponges and Hydra do not have a circulatory system. Functions of blood in them are performed by the water in which they live.
Excretory system
• Excretion – It is the process of removing harmful waste products produced in the cells of living organisms.
• The excretory system in humans
• Kidney is the main excretory organ of the human body.
It plays an important role in the formation of urine. Human kidney produces about 1 – 1.8L of urine in a day.
The urine consists of 95% water, 2.5% urea and 2.5% other waste products.
Ureter carries urine to the bladder. Urinary bladder collects urine which later on expels through Urethra.
The main excretory product in human body is urea while in aquatic animals, it is ammonia.
Salts along with water are removed as sweat. Sweating also helps to cool our body.
In birds, lizards, and snakes, the main excretory product is uric acid.
The process of removing wastes using an artificial kidney is called dialysis.

Transport of water and food in plants
Water and minerals are absorbed by the cells of root hair.
Root hair increases the surface area for absorption of water and minerals.
Xylem and phloem (collectively called as vascular tissue) are transport systems in plants.
• Xylem transports water and minerals from the soil via root hair to the rest of the plant body.
• Phloem transports food materials from leaves to different parts of the plant body.

Excretion in plants
Plants get rid of the excess of water by transpiration.
Transpiration is the evaporation of water from plants.
The water evaporates through stomata.
Chapter 1: Nutrition in Plants   
❖ Nutrition
• Process of obtaining nutrients from the environment.
• An important source of energy for growth and development of body.

❖ Modes of nutrition
• Autotrophic nutrition – Organisms synthesize their own food with the help of raw materials. Example: green plants and algae
• Heterotrophic nutrition – Organisms derive nutrition from the food prepared by plants.
• Autotrophic nutrition
  ⚬ Green plants prepare their food by the process of photosynthesis.
  ⚬ Photosynthesis is the process of synthesizing food from CO2 and water in the presence of sunlight and the green pigment called chlorophyll.
  ⚬ The equation for photosynthesis isCarbon dioxide + Water chlorophyllsunlightCarbohydrate + Oxygen
  ⚬ Green plants absorb CO2 from atmosphere through stomata, present on the surface of leaves.
  ⚬ Water and minerals are absorbed from soil.

    ⚬ Plants cannot obtain nitrogen from the atmosphere. Some bacteria (Rhizobium) convert atmospheric nitrogen into usable form.

❖ Heterotrophic nutrition in plants
   ⚬ Parasites: Organisms that do not prepare their own food but derive nutrients from a host. Example: Cuscuta (Amarbel)
   ⚬ Insectivorous plants: Pitcher plant is an insectivorous plant (insect-eating plant).
      Its leaf gets modified into a pitcher-like structure, which traps the insects. It has both autotrophic and heterotrophic mode of nutrition.
   ⚬ Saprotrophs: They obtain nutrition from dead or decaying organic matter. Example: Fungi.
   ⚬ Symbiosis: It is the association between two organisms where they live together and share shelter and nutrients without harming each others.
      Lichens are organisms formed by a symbiotic relationship between algae (provide food) and fungi (absorb water and nutrients).

 ❖ Nutrients replenishment in Soil
   ⚬ Manures and fertilizers fulfil the nutrient requirement of plants.
   ⚬ A bacterium, called Rhizobium, fixes atmospheric nitrogen and converts it into a usable form for the plant. It shows symbiotic relationship with legume plants.Chapter 9: Soil
Soil is a naturally occurring substance that is valuable in sustaining life on earth.
Humus – It is a partially decomposed organic matter of soil.
Weathering – It is the process of formation of soil by breaking down of rocks. It occurs by the action of wind, water, and climate.
Soil profile – It is a vertical section through various layers of soil. These various layers are known as horizons.
There are four types of horizons.
  • A-horizon or topsoil – It is the top most soil, which is dark in colour and rich in humus. It is soft, porous, and has the ability to retain water.
  • B-horizon – It is the middle next layer of the soil profile. It has lesser humus and more minerals. The layer is harder and more compact.
  • C-horizon – It is the third layer made up of small lumps of rocks with cracks and crevices.
  • Bedrock – It is the lowermost hard layer and difficult to dig with a spade.

Soil Types: Soil is a mixture of rock particles and humus.
  • Soil → Rock particle + Humus
  • Living organisms such as microbes, earthworm, and plant roots are found in soil.

Classification of soil
  • Sandy soil
  ⚬ Sand particles are large that cannot fit together.
  ⚬ Larger spaces are present between particles.
  ⚬ It is light, well aerated, and dry.
  • Clayey soil
  ⚬ Clay particles are smaller and tightly packed together.
  ⚬ It has little space for air and can hold water between particles.
  • Loamy soil
  ⚬ It is the best top soil for the growth of plants.
  ⚬ It is the mixture of sand, clay, and silt.
  ⚬ It contains humus and has the right water holding capacity.

Properties of Soil
  • Precolation rate of water varies in different soil types.
  • Precolation rate of water is highest in sandy soil and least in clayey soil.
  • The soil moisture and water absorption capacity of soil also varies among different soil types.
  • Loamy soil has the maximum accurate water holding capacity while sandy soil has the least.
  • Climatic factors such as wind, rainfall, temperature, light, and humidity affect the soil.
  • Soil and crops
S.No. Crops Grown Soil Types
1. Wheat and gram Clayey and loamy
2. Paddy Clayey soil
3. Lentils (Masoor) and other pulses Loamy soil
4. Cotton Sandy-loam or loamy soil
• The soil capacity to hold water is important for the cultivation of various crops.Chapter 8: Winds, Storms and Cyclones
Air exert pressure: In an anemometer, moving air exerts pressure on the bowls. Hence, this indicates the direction of wind.
High speed winds are always accompanied by reduced air pressure.
A paper ball acquires zigzag motion and does not go into a bottle when air is blown on it to force it into the bottle.
The balloons move towards each other when air is blown between them.
Air moves from high air pressure region to low air pressure region. The greater the difference in air pressure, the faster the air moves.
Air expands on heating: A deflated balloon inflates slightly when tied over the neck of a tube and immersed into boiling water.
Hot air moves upwards : Air inside the left bag expands on heating. Hence, this bag rises up because warm air is lighter than cold air.
Uneven heating on the earth generates wind. The monsoon winds carry water with it that falls down as rain.
Thunderstorms develop in hot and humid tropical areas. These are very frequent in India.
High speed wind and difference in air pressure cause cyclones.
Factors such as wind speed and direction, temperature, and humidity contribute to the development of cyclones.
Eye of a cyclone is a low pressure region.
Closed areas are the safest places during thunderstorms and cyclones.Chapter 7: Weather, Climate, and Adaptations of Animals to Climate
❖ Weather is the daily condition of the atmosphere at a place in terms of temperature, humidity, rainfall, wind-speed, etc. It vary over short period of time.
The maximum temperature of a day is recorded in the afternoon, while the minimum temperature of the day is recorded early in the morning.
Changes in weather are caused by sun.
❖ Climate is the average weather pattern in some location over a long period of time.
The climate of a place that receives very little rainfall and has high temperature throughout the year is hot and dry. Example: deserts
The climate of a place that receives plenty of rainfall is wet and humid. Example: the North-East region of India
The polar region and the tropical rainforest are the two regions of the earth with extreme climatic conditions.
Polar region
  • It is marked by extreme climatic conditions.
  • It is very cold for maximum part of the year.
  • In this region, sun does not set for six months and does not rise for the remaining six months.
  • The animals found in Polar Regions are polar bear and penguins.
  • Adaptive features of polar bear  
    ⚬ White fur to escape predator
    ⚬ Strong sense of smell to locate and catch its prey
    ⚬ Two thick layers of fur and a layer of fat to keep the body warm in cold conditions
    ⚬ Wide and large paws for swimming and walking
  • Adaptive features of penguin
    ⚬ White fur
    ⚬ Thick skin and layer of fat under skin
    ⚬ Streamlined body
    ⚬ Feet have webs for swimming
    ⚬ Birds found in polar region migrate to escape extreme cold conditions

❖ Tropical rainforest
  • The climate of tropical rainforest is generally hot and wet with continuous rain.
  • Tropical rainforests are found in Western Ghats and Assam in India, Southeast Asia, Central America and Central Africa.
  • The hospitable climatic condition supports huge populations of plants and animals.
  • Intense competition for food and shelter is found in Tropical rainforests.
  • Adaptive features of animals found in tropical regions
    ⚬ Red-eyed frog develops sticky pads on its feet to climb trees.
    ⚬ Monkeys have long and sturdy tail (for grasping branches), loud voice, etc.
    ⚬ Toucan has a long and large beak to reach fruits present on the branches.
    ⚬ Carnivores such as lions or tigers have thick, sensitive skin and stripes on their bodies to move fast.
    ⚬ An elephant uses its trunk as nose and tusk to tear the bark of trees.
      The soles of their feet are covered with thick pads to handle their enormous weight and they have large ears for hearing.
    ⚬ Animals living in tropical regions have the ability to camouflage to protect themselves from predators.Chapter 6: Physical and Chemical Changes
Changes classified into two types − physical and chemical.
Physical Change Chemical Change
• The physical composition of a substance does not change. • The chemical composition of a substance changes.
• Most changes are reversible. • Most changes are irreversible.
• No new substances are formed.
  For example,
  Ice Water Steam
• New substances are formed.
  For example,
  Paper Ashes

Rusting is an example of chemical change which require the presence of both air and moisture.
Rusting can be prevented by
  • Cutting the contact of either air or water or both with iron.
  • Greasing, oiling and painting
  • Galvanisation: the process of depositing a layer of zinc on iron is called galvanization
  •  Alloying iron with other elements.
     For example, Stainless steel is an alloy of iron with carbon, chromium, nickel, and manganese.
Crystallization is an example of physical change. The process of crystallization is used for purification of some substances.Chapter 5: Acids, Bases, and Salts
Substances that are sour in taste are acidic in nature and those that are bitter in taste and soapy to touch are basic in nature.
Indicators: Chemicals that are used to check acidic or basic nature of substances are called indicators.
Natural Indicators Action on acid Action on base
Litmus paper Blue litmus paper to red Red litmus paper to blue
China rose Turns dark pink Turns to green
Turmeric paste Remains yellow Turns red
Neutral Substances: Substances that are neither acidic nor basic in nature are called neutral substances. Neutral substances do not affect the colour of indicators.
Neutralisation reaction:
    Acid + Base → Salt +Water + Heat
    Heat is also produced during the neutralization reaction.
The salt produced during neutralization reactions can be acidic, basic, or neutral in nature.
Ant sting contains formic acid.
    The effect of this acid is neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution which contains zinc carbonate.Chapter 4: Heat
❖ The measure of degree of hotness of a substance is called its temperature.
❖ The device that is used to measure the temperature of a substance is called thermometer.
   • Clinical Temperature - used for measuring temperature of human body. temperature range is 35- 42°C
   • Laboratory Thermometer - used for measuring temperature of common objects). Temperature range is –10 - 110°C.
❖ The unit for temperature is °C. The normal temperature of human body is 37°C.
❖ The transfer of heat takes place from a hotter object to a colder object.
❖ Three ways of heat transfer are
   • Conduction: The transfer of heat in solids usually takes place by this method.
     Substances that allow heat to pass through them quite easily are called conductors and those that do not, are called insulators.
   • Convection: The transfer of heat in liquids and gases takes place by convection.
     Land breeze and sea breeze are a result of unequal heating of air present over land and sea by the sun.


   • Radiation: Transfer of heat by radiation requires no medium. Heating of earth by sun is an example of heat transfer by radiation.

❖ Dark coloured objects are better absorbers of heat than light coloured objects.
    This is the reason why we prefer light coloured clothes in summers and dark coloured clothes in winters.
❖ Cotton clothes allow air to pass through them and absorb sweat from our body. So, cotton clothes are preferred in summers.
❖ Wool traps a lot of air between its fibres. Since air is a bad conductor of heat, it does not allow heat transfer.
    This is the reason why woollen clothes keep us warm during winters.Chapter 3: Fibre to Fabric
❖ Wool is usually obtained from hair (fleece) of sheep or yak. Other animals that can be used to obtain wool are llama, camel, goat, and alpaca.
❖ Sheep contains two kinds of hair, the coarse beard hair and the soft under hair. Wool is obtained from the soft under hair.
❖ In India, sheep are reared in many states including Jammu & Kashmir, Himachal Pradesh, Uttrakhand, etc.
❖ The steps that are involved in the processing of fleece to wool are given below.
  • Shearing – Process of shaving off the fleece of sheep to obtain wool.
  • Scouring – Process of washing of the fleece to remove dirt and dust.
  • Sorting – The process of separating the fleece on the basis of its texture.
  • The sorted wool is then again scoured with the help of machines and dyed into various colours before it is rolled into a yarn.
❖ Rearing of silkworm to obtain silk is called sericulture.
❖ The life cycle of a silkworm is represented below.
❖ For obtaining silk,
  • Silkworms are reared on a large scale.
  • A female silk moth gives hundreds of eggs on the mulberry leaf.
  • The eggs are then hatched by keeping them under the right temperature and humidity conditions.
  • Then, the silk worms are fed on mulberry leaves.
  • After 20-25 days, caterpillars stop eating and start spinning cocoons around them.
  • Further development of the moth continues inside the cocoon. The moth leaves the cocoon after its development is complete.
  • Once the moth has left the cocoon, it is collected to obtain silk.
  • The cocoons are kept under the sun or boiled or exposed to steam to separate the silk fibres. This process is known as reeling the silk.
  • Silk fibres obtained after reeling are spun into silk threads.Chapter 2: Nutrition in Animals
❖ Animals are heterotrophs. They obtain their food directly or indirectly from plants.
Digestion is the process of breaking down of complex food components into simpler molecules.
❖ Various modes of feeding are scraping, chewing, capturing, swallowing, etc.
❖ The human alimentary canal includes buccal cavity, oesophagus, stomach, small intestine, large intestine, rectum, and anus.
❖ The liver, pancreas and salivary glands are the main digestive glands.
❖ Five important steps in human nutrition are − ingestion, digestion, absorption, assimilation, and egestion.
    • Ingestion is the process of taking food. It takes place through mouth.
    • Mouth includes teeth, saliva, and tongue. Teeth break down the food.
    • Teeth in human jaw
Types of teeth Function Total teeth in lower Jaw
Molars Chewing and grinding 6
Premolar Chewing and grinding 4
Canines Piercing and tearing 2
Incisors Cutting and biting 4
 • In total life span of human two sets of teeth grow – milk teeth and permanent teeth.
 • Saliva is secreted by salivary glands located under the tongue. It contains a digestive enzyme that breaks down starch into sugar.
 • Tongue helps in chewing and swallowing of food.
 • The food from mouth passes down the oesophagus to the stomach, through the movement of walls of oesophagus.
 • Inner lining of stomach secretes:
   ⚬ Mucus – protects the lining of stomach
   ⚬ Hydrochloric acid – creates an acidic medium and dissolves bits of food.
   ⚬ Digestive juices – break down protein into simple substance

• The food from stomach moves into the small intestine.
  ⚬ It is the longest part of alimentary canal.
  ⚬ Complete digestion of carbohydrate, proteins, and fats takes place here.
  ⚬ It receives intestinal juice from two glands – liver and pancreas
  ⚬ Liver - It is the largest gland of the body and secretes bile juice. Bile juice is stored in gall bladder and it plays an important role in the digestion of fats.
  ⚬ Pancreas - Pancreas contains enzymes that help in complete digestion of all food components.
  ⚬ The digestive tract and associated glands together constitute the digestive system.

• Carbohydrate is broken down into glucose.
Proteins are broken down into amino acids while fats broken down into fatty acids and glycerol.
All the digested food is absorbed by the walls of intestine. This process is known as absorption.
Inner lining of small intestine has tiny finger-like projections called villi that increase the surface area for more efficient food absorption.
The absorbed food is delivered to each and every cell of the body where they are used to produce complex substances such as proteins, etc.
   This process is known as assimilation.
The digested food from small intestine goes into blood stream and the undigested and unabsorbed material and water enters the large intestine.
The function of large intestine is absorption of water and some salts from undigested food.
From large intestine, the waste material is stored in rectum in the form of semi-solid faeces.
The undigested, stored waste is excreted out from the body as faeces via anus. This process is known as egestion.

Digestion in other animals:
Cellulose is a type of carbohydrate that can be digested by ruminants such as cows and buffaloes.
Ruminants have sac-like structures called caecum between small and large intestines where cellulose is digested by the action of certain enzymes.
  Caecum is absent in humans.
Rumen is a part of stomach in ruminants that stores the swallowed food.
The partially digested food is called cud. The process of chewing cud is called Rumination.
Amoeba absorbs its food by forming temporary finger-like projections on its cell surface called pseudopodia. The food is broken down inside the food vacuole.

Diarrhoea is the frequent passing of watery stool. It may be caused by food poisoning, infection or indigestion.
The patient of diarrhoea should be given plenty of boiled and cooled water with a pinch of salt and sugar dissolved in it. This is called Oral Rehydration Therapy.
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