PSEB Notes

This PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline

→ A system made up of plants, animals, and micro-organisms are called a forest.

→ The top layer of the forest is Canopy Layer, the mid-layer is the Crown layer and the lower layer is the Understory layer.

→ Forests protect the soil from erosion.

→ Soil helps in the growth and development of trees.

→ Humus shows that nutrients from the bodies of dead plants and animals have been incorporated into the soil.

→ Forests act like green lungs and produce many products. That is why forests are so important.

→ A forest is an area whose uppermost layer is topped by trees.

→ Forests are always green.

→ A variety of animals, plants, and insects are found in forests.

→ All wild animals, herbivores or carnivores, depend on plants for food in one or the another way.

→ Forests continue to grow and develop and can regenerate.

→ Forests affect climate, water cycle, and air quality.

→ Trees, shrubs, vegetation, herbs, etc. all are found in forests.

→ According to the height of trees and plants, forests are divided into three categories:

• Canopy
• Crown
• Understory

→ Forest soil helps in regeneration.

→ Forest plants emit vapours and help bring rain and regulate the temperature of the environment.

→ Different layers of vegetation in forests provide food and shelter to animals, birds, and insects.

→ In the forest, soil, water, air, and living things have interdependence on each other.

→ Forests provide important basic necessities for communities living in forested areas.

→ Forests maintain and regulate climate, water cycle, and air quality.

→ Decomposers depend on the dead bodies of plants and animals and turn them into simple substances.

→ Deforestation causes global warming, decreases rainfall, increases pollution, and erodes soil.

→ To maintain balance in nature and maintain habitat for wild animals and plants forest plays an important role.

→ Forest: A forest is an area where there is a lot of dense vegetation, including animals, trees, bushes, and weeds that grow naturally.

→ Canopy: The top layer of tree branches forms a dense top layer of trees on earth which is called the canopy.

→ Crown layer: The layer in which the branches and trunks of trees come, is called the crown or crown layer.

→ Understory Layer: The shaded area below which there is very little light, is called the lower or understory layer.

→ Ecosystems: Living things and their environment work together to create ecosystems. Plants, animals, and microorganisms are the biological components of the ecosystem. These are divided into different categories of producers, consumers, and decomposers.

→ Food chain: In ecology, the sequence of transfer of matter and energy in the form of food from one organism to another organism is called a food chain.
For example:

→ Food Web: A food web consists of a network of many food chains. A food chain helps provide food to organisms at the next food level.

→ Afforestation: The process of planting trees on a large scale is called Afforestation.

→ Decomposers: Microorganisms that decompose the dead bodies of plants and animals into humus, are called Decomposers.

→ Erosion: In the absence of trees and plants top layer of soil is lost, This process of carrying away the topsoil by wind and water is called soil erosion.

→ Replenishment of forest: Planting a large number of plants and trees in the forest area is called forest replenishment.

This PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource

→ All living things need water to survive.

→ The three states of water are solid, liquid and gas.

→ Less than 1% of the world’s water is freshwater or out of all Earth’s water, only about 0.00367% is available for human consumption.

→ Our future depends on the availability of water.

→ Every year March 22 is celebrated as World Water Day.

→ The minimum recommended amount of water per person is 50 Litres per day.

→ Water scarcity has become a global concern.

→ About 71% of the earth’s surface is covered by water.

→ Almost all the water on the earth is found in the oceans, seas, rivers, land, and atmosphere.

→ Useful water is freshwater.

→ Salt-free water present on Earth is 0.006% of the total amount of water available on Earth.

→ In solid-state water is present as ice and snow found in the snow-covered mountains at the poles of the earth and as glaciers.

→ Water in the liquid state is found in oceans, lakes, rivers as well as groundwater below ground level.

→ In the gas state, water is present in the air in the form of Vapours in the atmosphere.

→ Rainwater is considered to be the purest form of water.

→ The transfer of water is done by the water cycle.

→ The main source of water is groundwater.

→ Groundwater accumulates in the layers of stable hard rocks.

→ Population growth, increase in industrial and agricultural activities, etc. affect the groundwater level.

→ Groundwater level decreases due to high utilization of groundwater and low absorption of water by land.

→ Rainwater is used for rainwater harvesting.

→ Factors affecting groundwater levels are deforestation and excessive water absorption.

→ Bawris and Drip irrigation systems are some of the techniques that can be used to meet water scarcity.

→ Without water, greenery will disappear from the earth, which means the end of life.

→ Time demands that everyone should use water sparingly. Hence the unwanted and excessive use of groundwater should be avoided.

→ When plants are not watered for a few days, they wither away and eventually die.

→ The Punjab Government had passed the Water Conservation Act 2009 of Punjab in the year 2009 under which the date of transplantation of Paddy crop for the first time was fixed on 10th June. This was later changed to June 15, 2015.

→ The Dead Sea is a salty lake bounded on the east by Jordan and on the west by Israel and Palestine.

→ It is 8.6 times saltier than the other oceans having more alkalinity, the cause non-existence of plants and living creatures, which is why it is called the Dead Sea.

→ Water Cycle: Many processes such as evaporation of water into the air, formation of clouds through condensation, and the occurrence of precipitation which maintains water on the earth, even though the whole world uses it is called the water cycle.

→ Fresh Water: The water that is suitable for drinking is freshwater. It contains a very small amount of salt. This is about 3% of the total water on earth, which is found in rivers, lakes, glaciers, snow-capped peaks, and underground.

→ Water table: At a depth near the water source where the space between the rocks is filled with water is called groundwater area or saturated area. The surface of this water is called the water table.

→ Wet Rock layer: Groundwater between layers of hard rock below the water table is called the wet rock layer. This water is drained through tube wells.

→ Infiltration: Water from various sources such as rain, rivers, and ponds is going even deep inside the earth due to gravity. This is called infiltration.

→ Water management: The efficient distribution of water is called water management.

→ Drip Irrigation System: This is an irrigation technique in which water is dripped through pipes to the plant.

→ Water Storage: The process of collecting rainwater and using it when needed is called water storage. This is done to compensate for the water level.

→ Bawris: This is the ancient method of water storage. This method is still practiced in many parts of India today.

This PSEB 7th Class Science Notes Chapter 15 Light will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 15 Light

→ A ray coming from a source of light falls on the object and after reflection enters our eyes so that we see the objects.

→ Light always travels in a straight line.

→ The reflection from the surface of the object must be the same to see the image.

→ After hitting a surface, the light returns to the same medium in a certain direction. The process of coming back of the light is called reflection of light.

→ The ray of light that strikes an object is called an incidental ray and the ray of light which after hitting an object returns to the same medium in a particular direction it is called a reflected ray.

→ The angle between the incident ray and the perpendicular drawn at the point of incidence is called the Angle of Incidence.

→ The angle between the reflected ray and the perpendicular drawn at the point of reflection is called the angle of reflection.

→ The angle of incidence and the angle of reflection are always equal. This is called the law of reflection.

→ The image formed on the screen is called a Real image.

→ The image that cannot be obtained on the screen even if the reflected rays appear to meet is called a Virtual image.

→ The image formed by a plane mirror is always formed behind the mirror. This image is virtual is erect and of the same size as that of the object.

→ The image formed by a plane mirror is at the same distance behind the mirror as the object is placed in front of the mirror.

→ The image formed by a plane mirror is laterally inverted i.e. the left side of the object becomes to the right of the image and the right side of the object is seen to be left of the image.

→ A concave mirror is a spherical mirror with a reflecting surface facing inwards.

→ A convex mirror is a spherical mirror with a reflecting surface facing outwards.

→ The rays of light coming from a distant object are considered to be parallel to each other and the point at which they actually meet after being reflected from the mirror or appear to meet is called the focal point of the mirror.

→ For a concave mirror, a virtual, erect, and large image is formed only when the object is placed between the principal focus and the mirror.

→ For a convex mirror, the image formed is erect, virtual, and smaller in size than the size of the object.

→ The lens is a piece of transparent medium surrounded by two surfaces. The two main types of lenses are

• Convex lens
• Concave lens

→ The convex lens is thicker in the middle and thinner at the edges.

→ The concave lens is thin in the middle than at the edges.

→ A convex lens is also called a Convergent lens whereas a Concave lens is called a Divergent lens.

→ The convex lens can be used to see small objects. Hence it is also called magnifying glass or reading glass.

→ On allowing white light to pass through a prism, it splits up into seven colours, which means white light is composed of seven colours.

→ The point at which the rays of light coming from a distant object (such as the sun) meet or appear to meet after suffering refraction from the lens is called the focal point of the lens.

→ When a ray of light enters from one medium to another transparent medium, it changes its path. The phenomenon of light changing its path is called the refraction of light.

→ Reflection of light: When light travelling in a straight line strikes the surface of a mirror or a polished opaque surface, it changes its direction and returns to the same medium. The process of coming back from the light is called the reflection of light.

→ Incidental ray: A ray of light falling on the smooth and polished surface is called an incident ray.

→ Reflected Ray: A ray of light after striking a mirror changes its direction and returns to the same medium, which is called a reflected ray.

→ The angle of incidence: The angle between the incident ray and the perpendicular drawn at the point of incidence is called the angle of incidence.

→ The angle of reflection: The angle formed between the reflected ray and the perpendicular drew at the point of incidence is called the angle of reflection.

→ Point of incidence: The point at which the incident ray strikes the surface of the mirror, is called the point of incidence.

→ Perpendicular: The normal or perpendicular line drawn from point of incidence.

→ Real Image: When the light coming from an object after reflection meets at a point forming an image then such image is called a real image.

→ Virtual reflection: When the rays of light only appear to meet at a point after reflection from a mirror then that point is called a virtual image. A virtual image cannot be obtained on the screen.

→ Spherical Mirror: A mirror whose reflecting surface is a part of a hollow spherical surface.

→ Concave mirror: If the inner surface of a spherical mirror is reflecting, it is called a concave mirror.

→ Convex mirror: If the outer surface of the spherical mirror is reflecting, it is called a convex mirror.

→ Light Reflection: The bouncing back of light after when light strikes a smooth surface.

→ Refraction of Light: When a ray of light enters from one transparent medium to another transparent medium, the ray of light changes its path. The phenomenon of change of path by light is called refraction.

→ Convex lens: This is a piece of transparent shell that is thicker in the middle than the edges. It is also called a converging lens.

→ Concave lens: This is a piece of the transparent medium that is thin in the middle and thick at the edges. This lens is also called a diverging lens.

→ Focus: The point on the principal axis where the parallel rays of light meet or appear to meet after passing through the lens is called the focus.

→ Focal length: The distance between the principal focus and the center of the lens is called the focal length of the lens.

→ Splitting of light: The process of splitting by when white light passes through a transparent medium (such as a prism of glass) of white light into seven colours is called the splitting of light.

→ Spectrum: It is a band of seven colours obtained after passing white light through the prism. These colors from top to bottom are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

This PSEB 7th Class Science Notes Chapter 14 Electric Current and Its Effects will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 14 Electric Current and Its Effects

→ Electrical components can be represented by symbols that are very convenient in representation.

→ The circuit diagram is a diagrammatic representation of an electrical circuit.

→ The symbol of an electric cell is two parallel lines, one of which is a long line and the other a short line.

→ A battery is a combination of two or more cells.

→ Batteries are used in flashlights, transistors, radios, toys, TVs, remote controls, etc.

→ Electric bulbs have a thin filament, which illuminates by the flow of electric current. This is due to the heating effect of the electric current.

→ In electric heaters, room heaters, and testers heating effect of current is used.

→ An electric fuse consists of a special wire having a low melting point so that when it is placed in an electric circuit carrying heavy current it melts.

→ Electrical fuses are used in an electric circuit to save electrical appliances from fire or any other damage when heavy current flows in the circuit.

→ Any metallic wire acts as a magnet when an electric current passes through it. This effect of electric current is called its magnetic effect.

→ When current is passed through an iron bar placed in a coil, it acts like a magnet. A magnet made in this way is called an electric magnet.

→ An electromagnet is a magnet and when an electric current is switched off, it loses its magnetic properties.

→ Electromagnets are used in many devices, such as electric bells and magnetic cranes, etc.

→ Conductor: A substance that allows an electric current to pass through it, is called a conductor.

→ Resistance: A substance that opposes the flow of electric current from passing through it, is called resistance.

→ Switch: This is a simple device that is used to complete the path for the flow of current or to break it, is called a switch.

→ Circuit: The path which electric current follows from the positive terminal of cell/battery to its negative terminal via bulb, resistance, and switch.

→ Bulb: A simple device that converts electrical energy into light energy.

→ Filament: A thin wire of tungsten metal that gets heated due to the passage of electric current and emits light, is called Filament.

→ Battery: This is a combination of two or more electrochemical cell that converts their chemical energy into electrical energy.

→ Electromagnetism: Place a soft piece of iron inside the coil and pass an electric current through the coil. With this comes the property of a magnet inside a piece of iron. This technique is called electromagnetism.

→ Electric bell: A mechanical device that works on the principle of an electromagnet and produces repeated sounds on passing electric current.

→ Electric Crane: It consists of a crane with a large powerful magnet attached to one end that is used to lift, heavy objects made of iron and move them from one place to another place.

This PSEB 7th Class Science Notes Chapter 13 Motion and Time will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 13 Motion and Time

→ If an object does not change its position with respect to the objects around it and with time, then that object is called at rest.

→ If an object changes its position according to the objects around it and with time, then it is in motion.

→ The motion in a straight line of an object is called straight-line motion.

→ The motion of an object on a circular path is called circular motion.

→ If an object moves around its center position, the motion of that object is called Periodic motion.

→ If an object takes very little time to cover a short distance then the speed of the object is fast and if the object takes more time to cover the same distance then its speed is called slow.

→ The distance covered in 1 unit time is called the Speed. Its S.I. unit is meter per sec (m/s).

→ The Speed can be calculated using the following formula: ccc

→ The motion of an object moving at a speed along a straight line is called a Uniform Motion when the motion of an object moving at different speeds on a straight line is called Non-uniform Motion.

→ The motion of the hour hand of the clock, the motion of the earth around the sun, and the motion of a simple pendulum all are examples of uniform motion.

→ Nowadays we measure time with wall clocks, table clocks, wristwatches, or mobile phones. The SI unit of time in seconds.

→ Heavy mass (metal sphere) tied to a thread and hung in a fixed place or stand is called a simple pendulum.

→ The movement of a simple pendulum back and forth a point is called a recurring or oscillating motion.

→ The time taken to complete one oscillation is called the time period.

→ The number of oscillations completed in a second is called frequency. The S.I. unit of frequency is hertz.

→ A device that measures the speed of vehicles is called a Speedometer.

→ The speedometer measures the speed of vehicles in kilometers/hour.

→ An instrument used to measure the distance covered by vehicles is called an Odometer.

→ The graph illustrates the comparison of one quantity with another.

→ There are generally three types of graphs prevalent:

• Linear graph
• Bar graph
• Pie chart

→ The distance-time graph is a linear graph.

→ It represents the graph between the distance and time covered by the object.

→ The amount that is independent is represented on X-axis (horizontal axis) and the other amount which is dependent is on the Y-axis (vertical axis).

→ If an object is at rest, its distance-time graph is a straight line parallel to the X-axis.

→ Graph: If two quantities depend on each other then their representation is called a graph.

→ Speed: The distance covered by the object in the unit time interval is called the speed.

→ Uniform motion: When an object travels equal distances in equal time intervals, the motion is uniform.

→ Non-uniform motion: The motion of an object when it does not cover the same distance in equal time intervals is called non-uniform-motion.

→ Simple pendulum: A small piece of metal or stone hanging with the help of thread from a fixed point is called a simple pendulum.

→ Oscillation: When a freely hanging object moves from its center position to one extreme side and then to the other extreme side and finally reaches its previous position i.e. middle position, the object is said to complete an oscillation.

→ Time period: The time taken by a simple pendulum to complete an oscillation is called a time period.

→ Uniform speed: When an object travels equal distances in equal time intervals, no matter how small the time interval, the speed of the object is called uniform speed.

→ Non-uniform speed: When an object does not cover equal distances in equal time intervals, no matter how short the time interval, the speed of that object is called non-uniform speed.

This PSEB 7th Class Science Notes Chapter 12 Reproduction in Plants will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 12 Reproduction in Plants

→ Plants reproduce in two ways Sexual reproduction and Asexual reproduction.

→ Asexual reproduction is a method of reproduction by which new plants are bom from a single parent.

→ There are different methods of asexual reproduction like reproduction by sprouting, reproduction by seeds, fragmentation.

→ In the fragmentation reproductive process, the organism is divided into equal parts which grow into two individuals.

→ During sexual reproduction, the male and female reproductive organs of plants produce male gametes and female gametes which fuse together to form zygotes. The zygote develops into a new plant.

→ Sexual reproduction occurs only in flowering plants.

→ Vegetative propagation is a method of reproduction in which new plants grow through organs like roots, stems, or leaves. In this method of reproduction, neither the genitals nor the seed participates.

→ There are also many artificial methods of reproduction in plants. These are grafting, cutting, and burring under the ground.

→ The transfer of mature pollen grains from the anther to the stigma is called pollination. They reach the stigma of the same flower or another flower.

→ Flowerless plants like moss breed through fragmentation, through yeast breed through buds, while fungi and moss breed through spores.

→ The fusion of the male gamete and the female gamete in the ovum is called fertilization.

→ After fertilization of the ovaries, the ovaries develop into fruit and the ovum develops into seeds.

→ In order to move the seeds away from the germinating plants, it is necessary to scatter the seeds so that the seeds can grow into new plants.

→ Reproduction: The ability to live beings to produce new creatures like themselves is called reproduction.

→ Asexual reproduction: A method that does not require seeds to grow new plants. A single parent is required for reproduction.

→ Sexual Reproduction: Sexual reproduction is a method to produce a new organism through the combination of male and female gametes.

→ Vegetative propagation: When a new plant is obtained from any part of the plant except seed, it is called vegetative propagation.

→ Fragmentation: The formation of a new organism by dividing the body of an animal into Two or more parts is called fragmentation.

→ Unisexual Flower: A flower that has only stamens or only pistil is called a unisexual flower.

→ Bisexual flower: A flower in which both stamens and pistil are present is called a bisexual flower.

→ Fertilization: The combination of male and female gametes is called the action of fertilization.

→ Pollination: The transfer of mature pollen from the pollen cell to the stigma is called pollination.

→ Self-pollination: Pollination in flowers, when the pollen grains land on the same flower this action is called self-pollination.

→ Cross-pollination: Pollination action in which the pollen goes from the anther of one flower to the stigma of another flower. This type of pollination is done by two flowers of the same plant or flowers of the same species.

→ Germination of seeds: Reaching the moist soil, the seeds absorb water and swell. As the embryo begins to germinate, the root sprouts sink into the soil, and the stem sprouts up into the air. The leaves come out. This process is called seed germination.

This PSEB 7th Class Science Notes Chapter 11 Transportation in Animals and Plants will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 11 Transportation in Animals and Plants

→ All living things need energy for various activities and this energy is received from food.

→ The leaves need water and CO₂ to make food through photosynthesis.

→ In animals, food, oxygen, and water are delivered to every cell in the body, and waste products are transported from the cells to the body’s excretory organs.

→ The movement of substances from one place to another in an organism is called transportation.

→ The circulatory system of developed organisms consists of the heart, blood vessels, and blood, which carry oxygen, carbon dioxide, food, hormones, and enzymes from one part of the body to another.

→ The single-cell organism does not have a circulatory system.

→ Blood contains red blood cells, white blood cells, platelets, and plasma.

→ The red color of the blood is caused by a pigment called Haemoglobin.

→ The heart is a muscular organ that constantly beats like a pump for the circulation of blood.

→ The number of heartbeats per minute is called the pulse rate.

→ The arteries contain oxygenated blood and the veins contain carbon dioxide-rich blood.

→ Cells exchange nutrients, gases, and follicles between blood and tissue fluids.

→ The human excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.

→ The kidney produces waste products in the form of urine, lungs in the form of carbon dioxide, and skin in the form of sweat.

→ The blood cells in the human kidneys filter the blood.

→ Dialysis is the process by which a machine removes unwanted substances and excess fluid from the blood.

→ Diffusion is a process in which a matter moves from a region of higher concentration to a region of low concentration.

→ Dispersion is the process by which a solvent passes through a semi-permeable membrane. And the movement is from low-density solution to high-density solution.

→ Single-cell organism exchanges substances in the external environment from the cell surface.

→ Photosynthesis: The process of formation of carbohydrates (food) by green plants from simple compounds such as carbon dioxide and water in the presence of chlorophyll in the presence of sunlight is called photosynthesis.

→ Dispersion: This is the process in which solvents pass through a semi-permeable membrane from a low concentration solution to a solution with a higher concentration so that the concentration of the solution on both sides becomes equal. This type of transport is for short distances. Plant roots absorb water from the soil by this process.

→ Transpiration: The vaporization of water through the leaves of plants is called transpiration.

→ Transportation: The transfer of food from the leaves to other parts of the plant is called transportation.

→ Phloem: Plant tissues that carry food from the leaves to other parts of the plant, is called Phloem.

→ Arteries: The tubes that carry oxygen-rich blood from the heart to different parts of the body, are called arteries.

→ Veins: The capillaries that carry blood from different parts of the body to the heart, are called veins.

→ Excretion: The process of expelling harmful and waste products from the body is called excretion.

→ Dialysis: The process of removing urea and other toxic substances from the kidneys of the body with the help of an artificial machine is called dialysis.

This PSEB 7th Class Science Notes Chapter 10 Respiration in Organisms will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 10 Respiration in Organisms

→ Breathing is a part of the process of Respiration during which the living beings take in (inhale) oxygen and give out (exhale) carbon dioxide into the air.

→ The oxygen we take in when we breathe breaks down glucose into water and carbon dioxide and also releases the energy that is necessary for the existence of living beings.

→ During cellular respiration, glucose is broken down in the cells of an organism.

→ During Aerobic respiration, glucose is broken down in the presence of oxygen.

→ During Anaerobic respiration, the breakdown of glucose occurs in the absence of oxygen.

→ During hard physical activities such as heavy exercise, fast running, and cycling, etc, energy demand is high but oxygen to produce energy is limited so anaerobic respiration takes place.

→ The breathing rate also increases during heavy physical activity.

→ Different organs are present in different organisms for respiration.

→ Lungs expand when oxygen is inhaled and contract again when exhaled.

→ The blood contains haemoglobin which carries oxygen to different parts of the body.

→ In cows, buffaloes, dogs, cats, and other mammals, the respiratory organs are similar to the human respiratory organs and the respiratory function is similar to that of humans.

→ In earthworms, gases in the gut are exchanged through moist skin.

→ In fish, this action takes place through the gills and in insects through the respiratory tract.

→ The breakdown of glucose in plants is similar to that in other organisms.

→ The roots of plants take air from the soil.

→ The leaves have small pores or holes called stomata, through which gases are exchanged.

→ Respiration: It is a biochemical reaction in organisms that involves the oxidation of complex organic foods. This results in the formation of carbon dioxide and water and releases energy.

→ Aerobic Respiration: Respiration that occurs in the presence of oxygen is called aerobic respiration.

→ Anaerobic Respiration: Breathing that occurs in the absence of oxygen is called Anaerobic Respiration.

→ Stomata: A special type of pores are present on the top layer of leaves for the exchange of air and water vapours, called stomata.

→ Respiration: This is a simple mechanical activity in which oxygen-rich air is pulled and goes into the lungs (respiratory organs). This action is called breathing. Carbon dioxide, rich air is released into the atmosphere after respiration called exhalation. This complete process is called Respiration.

→ Breathing: The act of filling the respiratory organs (lungs) with oxygen-rich air from the atmosphere is called breathing.

→ Exhalation: An activity in which carbon dioxide-rich air is expelled out of the lungs.

→ Cellular Respiration: The process that takes place inside a cell in which energy is produced after the chemical decomposition of food is called cellular respiration.

→ Breathing rate: The number of times a person breathes in a minute is called breathing rate.

→ The average person’s breathing rate is 12 to 20 breaths per minute.

→ Gills: These blood vessels are special wing-like organs that are present in some aquatic organisms, such as fish, breathe with help of gills. The water and blood flow in opposite directions which increases the diffusion of oxygen.

This PSEB 7th Class Science Notes Chapter 9 Soil will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 9 Soil

→ The top layer of the earth in which crops and plants can grow is called soil.

→ Soil is made up of broken rocks, organic matter, animals, plants, and microorganisms.

→ There are different layers of soil, which can be seen in the soil profile.

→ Soil is made up of both organic and inorganic components.

→ The dead and rotten leaves of plants or the bodies of plants, insects, or dead animals buried in the soil, animal dung, etc. combine to form organic matter called humus.

→ Soil that contains a mixture of organic and inorganic substances is very useful for crops.

→ Depending on the size of the particles, the soil is clayey, sandy, rocky, and loamy.

→ Depending on the chemical nature of the soil, the soil may be acidic, basic, or neutral.

→ Acid soils have a pH of 1 to 6.

→ Alkaline soils have a pH of 8 to 14.

→ Neutral soil has a pH of 7.

→ Ph paper is used to determine the nature of the soil.

→ Black soil contains iron salts and is good for growing cotton.

→ Soil containing sulphur is good for growing onions.

→ Different types of soil are required to grow different types of crops.

→ It takes many years for the formation of the top layer of soil.

→ Removal of topsoil due to floods, winds, storms, and mining is called Erosion.

→ By digging the soil, the animals with their feet loosen the soil and the soil, which has been loosened, gets eroded quickly by wind and water.

→ By planting trees, building check dams, planting grass on the sides of farmland, and building along sides of rivers and canals soil erosion can be prevented.

→ Soil: A mixture of rock/horizontal particles and humus is called soil.

→ Soil Profile: A vertical section through different layers of soil is called the soil profile.

→ Humus: The dead and decaying organisms present in soil are called humus.

→ Soil Moisture: Soil retains water in it, which is called soil moisture.

→ Soil erosion: The removal of the top layer of soil by water, wind, or ice is called Soil erosion.

→ Weathering: It is a method in which soil is formed by the breakdown of rocks by the action of wind, water, and climate.

This PSEB 7th Class Science Notes Chapter 8 Winds, Storms and Cyclones will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 8 Winds, Storms and Cyclones

→ The air around us exerts pressure.

→ Moving air is called wind.

→ Very strong wind lowers the pressure.

→ Air expands on heating and contracts on cooling.

→ Hot air is lighter than cold air.

→ The wind moves from high-pressure areas to low-pressure areas.

→ Wind speed is measured with an Anemometer.

→ The direction of wind speed is measured by the wind vane.

→ Wind currents (movement) are caused by the uneven heating of the earth.

→ Monsoon winds are filled with moisture (water vapours) and bring rain.

→ Cyclones are destructive.

→ A cyclone crossed the coast of Orissa on October 18, 1999.

→ Cyclones have higher wind speeds.

→ A cyclone is a very strong whirlwind that revolves around very low-pressure areas.

→ A hurricane is a storm with strong winds blowing through, in a funnel-shaped cloud.

→ The loud noise produced during lightning is called thunder.

→ Heavy rain with strong winds is called a storm.

→ Hurricanes in the United States and typhoons in Japan are cyclones.

→ Tornadoes are dark cone-like clouds that form between the earth’s crust and the sky.

→ All kinds of natural disasters like cyclones, tornadoes, etc. destroy trees, wires, and communication systems.

→ Special policies are adopted during disasters.

→ A cyclone warning is given 48 hours in advance with the help of satellite and radar.

→ And self-help is the best help. So it would be helpful to plan your safety in advance and take precautionary measures before any cyclone actually strikes.

→ Wind: Fast-moving air is called wind.

→ Monsoon winds: The winds that come from the sea and carry water are called monsoon winds.

→ Tornado: Dark coloured cone-like clouds whose cone structure is from sky to earth is called Tornado.

→ Cyclone: A violent wind that moves in a circle causing a storm is called a cyclone.