Environmental Studies PYQs

The Correct Answer is Stratosphere.

Key Points  

• Ninety percent of the ozone in the atmosphere is occupied by the stratosphere, the layer of the atmosphere between about 10 and 50 kilometres altitude.
• The natural level of ozone in the stratosphere is a result of a balance between sunlight that creates ozone and chemical reactions that destroy it.
• The Earth's atmosphere consists of several layers.
• The lowest layer, the troposphere, extends from the Earth's surface up to about 6 miles or 10 kilometres in altitude.
• The next layer, the stratosphere, continues from 6 miles to about 31 miles.
• Ozone is a molecule that contains three oxygen atoms.
• Ozone molecules are constantly formed and destroyed in the stratosphere.
• The ozone layer in the stratosphere absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface.
• It absorbs the portion of the UV light called UVB.

Additional Information

​The atmosphere can be divided into five layers according to the diversity of temperature and density.

• They are:-

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere (Ionosphere)
5. Exosphere

• Troposphere - It is considered the lowest layer of the Earth’s atmosphere.
• The troposphere starts at the surface of the Earth and goes up to a height of 7 to 20 km.
• All-weather occurs within this layer.
• Temperature decreases at the rate of 1 degree Celsius for every 165 m of height.
• Tropopause separates the troposphere and stratosphere.​
• Stratosphere - It is the second layer of the atmosphere found above the troposphere.
• It extends up to 50 km in height.
• This layer provides some advantages for flight because it is above stormy weather and has steady, strong, horizontal winds.
• The ozone layer is found in this layer.
• The ozone layer absorbs UV rays and safeguards the Earth from harmful radiation.
• Stratopause separates the stratosphere and mesosphere.​
• Mesosphere - The mesosphere is found above the stratosphere.
• It is the coldest of the atmospheric layers.
• The mesosphere starts at 50 km above the surface of the Earth and goes up to 85 km.
• By 80 km it reaches -100 degrees Celsius.
• Meteors burn up in this layer.
• The upper limit is called Mesopause which separates the mesosphere and thermosphere​.
• Thermosphere - This layer is found above Mesopause from 80 to 400 km.
• Radio waves that are transmitted from the Earth are reflected by this layer.
• The temperature increases with height.
• Aurora and satellites occur in this layer.
• Exosphere - It is the outermost layer of the atmosphere.
• The zone where molecules and atoms escape into space is mentioned as the exosphere.
• It extends from the top of the thermosphere up to 10,000 km.

Hence, the atmospheric zone in which the ozone layer lies is called the stratosphere.

Environmental studies refer to an extensive and systematic study of nature/environment and of its physical, biological, social, and cultural factors, and the nature and characteristics of the relationship between man and environment. 

• The learning situations/experiences of EVS help children to explore and connect with their natural and human-made surroundings. EVS helps children develop their own insights into the functioning of several things in their environment.
• Such interactions with their surrounding environment are immensely important in the healthy development of children. Such interactions also enhance children’s learning capabilities by providing concrete learning experiences.

Important Points

• EVS class helps children to develop desirable attitudes, values, and behavior patterns necessary for an environment-friendly lifestyle. Many a time, a teacher faces some problems during the teaching-learning process of EVS.
• In the above-mentioned situation, the best corrective measure is to find out the reasons for irregularities and council Rakesh as it will help the teacher to:
• become more vigilant towards Rakesh.
• recognize the root of Rakesh's problem.
• better relate to his unacceptable behavior.
• assist him with proper guidance in the right way.

Key Points

• If the student is not doing an assignment, there are a number of ways by which a teacher can address the situation:
• Encourage students to come up with a reason.
• Find the cause for the problem & Council the student.
• Find the difficulty area of the student where he/she is lacking.
• Talk to the student and find out the reasons for his irregularities.

Thus, it is concluded that in the above-mentioned situation, the best corrective measure is to find out the reasons for irregularities and council Rakesh

The correct answer is Bhopal.

Key Points

• Bhopal is the capital city of Madhya Pradesh.
• Famous as the City of Lakes with the various natural and artificial lakes.
• It has many natural and artificial lakes and for being it is also one of the greenest cities in India.
• Bhopal is the capital city of Madhya Pradesh it is the 16^th largest city in India.
• Bharat Bhawan is located in this capital city.
• Charles Correa is the architect of Bhavan, it got opened in 1982 and faces the upper lake of Bhopal.

Additional Information

• Indore:
• It is also known as mini Bombay, it is located in the state of Madhya Pradesh.
• It is the cleanest city in India, under the Swachh Bharat Mission.
• Jabalpur:
• It is also known as marble city and Sanskaardhani of Madhya Pradesh.
• The famous waterfall Bhedaghat is located in this district
• Ujjain:
• It is an ancient city beside the Kshipra River in the central Indian state of Madhya Pradesh.
• It is a famous religious pilgrimage centre with the Kumbh Mela held here every 12 years.
• The famous temple of Mahakaleshwar Jyotirlinga is also located in this city.
• There are around 14 lakes in Bhopal.

Some of them are as follows:

• Upper Lake.
• Lower Lake
• Shahpura Lake
• Navab Siddiqui Hasan Talab
• Motia Talab.

A teacher is one who plays diverse roles like an innovator, action researcher, planner, manager, content provider, facilitator, leader, co-creator, etc.

Key Points

• A great teacher is warm, accessible, enthusiastic, and caring. This is the teacher to whom students know they can go with any problems or concerns.
• Teachers have to tackle many problems associated with students as children with numerous problems of behaviour are found in every educational programme.

Important PointsStudent's faith is very important for teachers. If the students are having faith in their teachers, teachers can teach them more effectively.

• Faith is a trust that is very important for teachers to build up.
• Faith in education encourages the development of the whole person.
• Great teachers inspire both students outside and inside the classroom.
• Students need to trust their teachers that they are creators of their life and teach them effectively with full dedication and commitment.

Thus, it is concluded that a teacher's most precious item is his Student's faith.

Etymologically, the hypothesis is made up of two words 'hypo' (less than) and 'thesis', which means less than a thesis. It is the presumptive statement of a proposition or a reasonable guess, based upon the available evidence, which the researcher seeks to prove through his\her study.

• The hypothesis is an assumption or proposition whose testability is to be tested based on the compatibility of its implications with empirical evidence with previous knowledge.
• It is also a declarative statement in which the investigator makes a prediction or a conjecture about the outcome of the relationship. The conjecture or the prediction is not simply an"educated guess", rather it is typically based on past researches, which investigators gathered as evidence to advance the hypothesized relationship between variables.
• In the formulation of a hypothesis, the investigator looks for the statements where she relates one or more variables to make predictions about the relationships. The hypothesis tells the researcher what to do and why to do it in the context of the problem.
• A hypothesis is often considered a tentative and testable statement of the possible relationship between two or more events/variables under investigation.
• A hypothesis does not have to be right or wrong, but the person formulating the hypothesis does have to be prepared to test the theory to its limits.
• A hypothesis is a proposed explanation for an observable phenomenon.

Important Points

• The theory is an accepted hypothesis. It summarizes the hypothesis or a group of hypotheses that have been supported with repeated testing.
• A theory is valid as long as there is no evidence to dispute it. Therefore theory can be disproved.
• A hypothesis is a theory that can after testing be accepted or rejected.

​Thus, it is concluded that a hypothesis tested repeatedly and not found incorrect becomes a theory.

Additional Information

• Law: A true empirical generalization, either affirmative (All A’s are B) or conditional (If A, then B) is called a law, which is accepted as true.
• Discovery: Discoveries involve finding or gaining knowledge about something previously unknown or unseen.
• Basic concept: They are ordinary ideas that occur in the mind, thought, etc.

There are a variety of teaching methods that can be used by the teacher for teaching theory and skills in the classroom setting. These are broadly classified as Teacher centered teaching methods and Student-centered teaching methods

Key Points

• ​Both seminar and project methods are suitable teaching methods as they are student-centered methods. They help in improving knowledge scores, skill scores, active learning ability, student collaboration, classroom atmosphere. These methods build interaction between teachers and students.

Seminar:

• Seminars are the gatherings of students who discuss the same topic at a common location. Presentation of research papers also takes place. The primary aim is to get a better picture, brainstorm, know the latest updates on the given topic.
• The purpose of the seminar is to provide an opportunity for students to actively participate in finding answers to questions or solutions to problems using the scientific approach of doing analysis and synthesis of facts observed.

Project:

• The project method of teaching is one of the modern methods of teaching in which the curriculum content is considered from the child's point of view and is related to his needs and interest in the context of real-life situations.
• It implies that activities in the schools need to be closely connected with the child's daily life and needs. The project can be carried out by the individual students, solved individually by each member of a group, or dealt with by a group of students or the class as a whole.

Thus, it is concluded that Seminar and Project is a suitable method of teaching.

Hint

• The dictation method is a student-centered method that helps them in only improving listening skills and vocabulary.
• A lecture is a teacher-centered method of teaching whereby the teacher attempts to explain facts or principles to help students to understand. In this method, the teacher is an active participant, the students are passive listeners.
• The assignment method is a technique that can be usually used in the teaching and learning process. It is an instructional technique that comprises guided information, self-learning, writing skills, and report preparation among the learners.

Helium is a Nobel Gas or inert gas it does not act as a greenhouse gas.

Explanation:

Greenhouse Effect:

• Solar energy trapped by the earth atmosphere and radiate slowly so as to cover our earth with a warm blanket.
• This is the natural process of the greenhouse effect on earth to maintain its temperature and makes the earth perfect for life.

Greenhouse gases are carbon dioxide, other greenhouse gases are methane, water vapour, nitrous oxide, CFCs and ozone. 

Values of radiation absorbed by the greenhouse gases are as follow:

From the above table, it is clear that carbon dioxide absorbs the maximum radiation in the earth’s atmosphere

Hence the correct option is Helium which is not a greenhouse gas

Important Points

Global warming: If the amount of greenhouse gases crosses by delicate proportion, the natural greenhouse balance may get disturbed and there is a continuous rise in temperature of the earth by trapping the solar heat continuously. This creates the overall effect of Global warming.

Explanation:

Noise pollution:

• Noise pollution is that unpleasant sound that causes uneasiness to the ear and can lead to serious health hazards.
• It is more prevalent in metropolitan cities compared to suburban areas.
• Traffic is the main noise pollution in urban areas.

Key Points

• Noise pollution, unwanted or excessive sound can have deleterious effects on human health, wildlife, and environmental quality.
• Noise pollution is commonly generated inside many industrial facilities and some other workplaces, but it also comes from the highway, railway, and aeroplane traffic and from outdoor construction activities.
• Sound waves are vibrations of air molecules carried from a noise source to the ear.
• Sound is typically described in terms of the loudness (amplitude) and the pitch (frequency) of the wave.
• Loudness (also called sound pressure level, or SPL) is measured in logarithmic units called decibels (dB).
• The normal human ear can detect sounds that range between 0 dB (hearing threshold) and about 140 dB, with sounds between 120dB and 140 dB causing pain (pain threshold).

The unit used for measuring noise pollution is Decibel.

Additional Information

Concept:

• There are 8 major river systems in India, with more than 400 rivers in total.
• Rivers play an important role in the lives of the Indian people due to their crucial importance in sustenance and their place in Indian religions.

Explanation:

Thus, the Subarnrekha river falls into the Bay of Bengal.

Key Points

Glacial valley: 

• Valleys are the most predominant landforms on the face of the earth.
• They are found on virtually every continent on planet earth, along sea bottoms, and other planets.
• Valleys usually feature rounded sides that mimic a V or a U shape.
• Glacial valleys are formed by moving glaciers.
• Glacier movement is driven by gravity.
• Glacial ice forms over many years as a result of the accumulation of snow.
• A time comes when the glacier becomes heavy, and with the aid of gravitational force, it starts to move.
• In the course of glacial movement across the landscape, they weather away and carve out valleys the same way a bulldozer digs a trench.
• This is why they have been nicknamed ‘’nature’s bulldozers”.
• Due to the weight and breadth of glaciers, the valleys formed are wider and flat bottoms with a shape looking like a U.
• Examples of valley glaciers include the Fjaerland Fjord in Norway and Mattertal in Switzerland.
• U-shaped valleys form through glacial erosion.
• U-shaped valleys are found in mountainous regions throughout the world including the Andes, Alps, Caucasus Mountains, Himalaya, Rocky Mountains, New Zealand, and the Scandinavian Mountains.

Thus,‘U’ shaped valley is formed by the action of glaciers.

Additional InformationV-shaped Valleys:

• V-shaped Valleys occur when a river is near its source.
• It often develops a V-shaped valley as the river erodes down (this is called vertical erosion).
• At the same time, weathering breaks up material on the valley slopes.
• This material is carried by the river and erodes the riverbed through abrasion.
• The V-shaped valley has been typically eroded by running water.

​Lapies:

• Lapiaz is a weathered limestone surface with sharp pinnacles, grooves and ridges.
• When water flows over a surface having limestone along with other hard rocks then Lapiaz is formed.
• Limestone is a soft rock that erodes to form various narrow and deep structures, clients, and grikes separated by pinnacles roughly parallel to each other.
• It is one of the features of Karst topography.

Waterfall:

• A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below.
• Waterfalls are also called cascades.
• The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls.

Key Points

Atmospheric pressure:

• The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called atmospheric pressure.
• The atmospheric pressure is expressed in units of millibar.
• Air pressure is measured with the help of a mercury barometer or the aneroid barometer.​

Important Points Barometer:

• The barometer is used to measure atmospheric pressure.
• A barometer is a scientific instrument used to measure atmospheric pressure, also called barometric pressure.
• A simple barometer consists of a long glass tube (closed at one end, open at the other) filled with mercury and turned upside down into a container of mercury.
• The barometer works by balancing the mercury in the glass tube against the outside air pressure, just like a set of scales.

​Thus, the instrument used to measure the atmospheric pressure is Barometer.

Additional Information

• A transgenic crop is a crop whose genes have been altered by manipulation.
• This crop is known as genetically modified crops (GM crops).
• GM plants can reduce reliance on chemical pesticides (pest-resistance crops).
• Transgenic means that one or more DNA sequences from another species have been introduced by artificial means.
• Transgenic plants can be made by introducing foreign DNA into a variety of different tissues.
• It is a plant that has a novel combination of genetic material obtained through biotechnology that adds a new quality to the parent crop like herbicide-tolerance.

Key Points

Bt Cotton- 

• Bt cotton is the only permitted GM crop in India.
• In which the soil is obtained by hybridization of two foreign genes with the bacterium "Bacillus thuringiensis" (BT).
• These genes help the cotton crop secrete a toxic protein to protect it from an insect called the common pink bollworm.​
• Some strains of Bt produce proteins that kill certain insects such as lepidopterans, coleopterans, and dipterans.
• Bt forms protein crystals during a particular phase of their growth.
• These crystals contain a toxic insecticidal protein.

​Thus, Bt cotton is a transgenic plant.

Additional Information

Golden rice-

• Rice is a staple food in many countries.
• By inserting two genes from daffodil and one gene from a bacterial species into the rice.
• Scientists produced rice capable of synthesizing β - carotene.

Tomato-

• Transgenic variety of Tomato - Flvar Savr.
• Due to inhibition of polygalacturonase enzyme which degrades pectin.
• So tomato variety remains fresh.

Along with harming human health, air pollution can cause a variety of environmental effects that affect the overall environment, acid rain being one of them.

Key Points

Acid Rain:  

• Acid rain means the precipitation of acidic components such as Sulfuric or Nitric acid.
• Sulfur dioxide and oxides of nitrogen get into the upper atmosphere by wind or air currents and get mixed with water.
• The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.
• Normal rain has a pH value of 5.6.
• It is slightly acidic due to the presence of carbon dioxide which gets dissolved into the water forming weak carbonic acid.
• However, acid rain usually has a pH between 4.2 and 4.4 because of the large quantity of acids.
• The major sources of sulphuric dioxide and oxides of nitrogen are the burning of fossil fuels, emission from vehicles, oil refineries, etc.

Thus, acid rain is chiefly due to atmospheric pollution by SO2.

Additional Information

​Controlling Acid rain:

• Reducing the amount of SO2 and NO2 being released into the atmosphere decreases the chances of acid rain.
• The main source of SO2 is coal fuel power plants in which SO2 emission can be reduced by new combustion techniques.
• Whereas the main source of NO2 in the atmosphere is through vehicular exhaust which can be controlled by using internal combustion engines.

• Productivity in an ecosystem refers to the percentage of energy that enters the ecosystem in the form of biomass at a particular trophic level.
• It is the rate at which **biomass is formed in the ecosystem.**​

Key Points

Tropical Rain Forests:

• ​Tropical rain forests are dense, multi-layered, and harbour many types of plants and animals.
• Found in areas receiving more than 200 cm of rainfall and having a temperature of 15-30 degrees Celsius.
• They are generally found in the equatorial and tropical regions from 23½ degrees north to 23½ degrees south.
• These forests are found in the areas receiving heavy rainfall (more than 200 cm annual rainfall).
• Therefore, these forests always appear green and are known as evergreen forests.
• The greatest single area of tropical evergreen forest is the Amazon Basin, in the northern half of South America.
• This forest has high soil moisture, high availability of nutrients so it has high net productivity.
• Hence, they are the most stable ecosystem.
• In terms of Net Primary Productivity (NPP) per unit area, the most productive systems are tropical rain forests.

Thus, tropical rain forests are the most productive ecosystem.

Additional Information

Tundra: 

• A tundra has extremely inhospitable conditions.
• It has the lowest measured temperatures of any of the five major biomes with average yearly temperatures ranging from -34 to 12 degrees Celsius.
• They also have a low amount of precipitation, just 15–25 centimetres (six to ten inches) per year.
• As well as poor quality soil nutrients and short summers.

Savanna:​

• There are two types of grasslands: tropical grasslands (sometimes called savannas) and temperate grasslands.
• Savannas are found closer to the equator and can have a few scattered trees with tall grasses.
• They mostly consist of large grazing animals like elephants, buffalo, giraffe etc.
• They cover almost half of the continent of Africa, as well as areas of Australia, India, and South America.

Desert:

• Deserts are dry areas where rainfall is less than 50 centimetres (20 inches) per year.
• They cover around 20 per cent of Earth’s surface.
• Deserts can be either cold or hot, although most of them are found in subtropical areas.
• Because of their extreme conditions, there is not as much biodiversity found in deserts as in other biomes.

Key Points

Calcium carbide:

• Calcium carbide is used to artificially ripen fruits.
• Calcium carbide comes in contact with moisture it produces acetylene gas.
• Calcium carbide is synthesized industrially from calcium oxide (lime), CaO, and carbon in the form of coke at about 2,200 °C (4,000 °F).
• CaC2 is a chemical compound with the chemical name Calcium Carbide.
• For reasons of safe transportation of fruits, mangoes, bananas etc are picked before they ripen fully.
• Slightly green harvested mangoes are subjected to small containers of calcium carbide (CaC₂) with a plastic covering.
• CaC₂ reacts with the moisture in the air to release acetylene (or ethyne) gas as follows:

CaC₂ + 2 H₂O → C₂H₂ + Ca(OH)₂

Thus, Calcium carbide is used for the ripening of mangoes.

Additional InformationCalcium carbonate:

• Calcium carbonate is a chemical compound.
• The chemical formula of Calcium carbonate is CaCO3.
• Limestone is a common type of carbonate sedimentary rock.

Calcium hydroxide:

• The chemical formula of Calcium Hydroxide is Ca(OH)2
• Calcium Hydroxide or Ca(OH)2 is also known as Slaked lime.
• It is a white powder or colourless crystal which is obtained when Quicklime (calcium oxide) is mixed with water.

Calcium chloride:

• Calcium chloride is a hygroscopic compound that means it readily attracts and absorbs water molecules from its surroundings.
• Calcium chloride binds to the water molecules through crystallisation and is therefore used as a drying agent.
• It can also be used to dry solvents like acetone, ethers, esters, etc.

• Diseases are caused by various factors.
• Contaminated water containing microorganisms is a major cause of various diseases.
• It is most prevalent in areas where people live below the poverty line and lack access to safe drinking water.

 

Key Points

 

Typhoid:

 

• Typhoid fever is a systemic infection caused by Salmonella typhi.
• It usually spreads through the ingestion of contaminated food or water.
• It can cause high fever, diarrhea, and vomiting.
• It can be fatal.
• It is more prevalent in areas where frequent handwashing is uncommon.

Thus, typhoid spreads through contaminated drinking water.

Important Points 

HIV-AIDS:

 

• Human Immunodeficiency Virus (HIV) is a virus that attacks the cells that help the body fight infections.
• It makes a person more susceptible to other infections and diseases.
• It spreads through contact with certain bodily fluids of a person with HIV.
• This usually occurs during unprotected sex (sex without condoms or HIV medication to prevent or treat HIV) or through the sharing of injection drug equipment.
• AIDS is the final stage of HIV infection, occurring when the virus severely damages the body's immune system.

Anemia:

 

• Anemia refers to low levels of hemoglobin or iron in the blood.
• Hemoglobin is an iron-rich protein in the blood responsible for transporting oxygen from the lungs to the tissues.
• Iron deficiency leads to low hemoglobin levels, preventing proper oxygen circulation throughout the body.
• Anemia is caused by iron deficiency.
• It is a medical condition that cannot be prevented simply by maintaining proper hygiene.

Tetanus:

• It is caused by the bacterium Clostridium tetani.
• It causes painful muscle contractions, particularly in the jaw and neck.

 

Additional Information 

Some common communicable diseases are as follows:

 

Greenhouse Effect: 

• Solar energy is trapped by the earth's atmosphere and radiate slowly so as to cover our earth with a warm blanket.
• This is the natural process of the greenhouse effect on earth to maintain its temperature and makes the earth perfect for life.

Key Points

Carbon Dioxide: 

• Carbon dioxide enters the atmosphere through burning fossil fuels, solid waste, trees and wood products.
• It is added as a result of certain chemical reactions.
• Carbon dioxide is removed from the atmosphere when it is absorbed by plants as part of the biological carbon cycle.

Methane: 

• Methane is emitted during the production and transport of coal, natural gas, and oil.
• Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

N₂O:

• Nitrous oxide (N2O), is a greenhouse gas.
• The average level of Nitrogen Oxide Pollution in rural homes without combustion appliances is about half that of outdoors.
• In rural homes with gas stoves, kerosene heaters, or unvented gas space heaters, indoor levels often exceed outdoor levels.

Important Points

Carbon Monoxide:

• Incomplete combustion occurs when the supply of air or oxygen is poor.
• Incomplete combustion of organic material produces carbon monoxide and carbon instead of carbon dioxide.
• Carbon monoxide is a poisonous gas, which is one reason why complete combustion is preferred to incomplete combustion.
• This is not a greenhouse gas.

​Thus, CO is not a greenhouse gas. 

Additional Information

Global Warming:

• An increase in the average temperature of the earth's surface due to the greenhouse effect is called global warming.
• It also refers to the increase in the average temperature of the air and sea at the earth's surface.

Mistake Points

Global warming and the Greenhouse effect both are different things.

The correct answer is: Mustard

Key Points

• Dicotyledonous plants are also called knowns are dicot and they are angiosperms (Flowering plants).
• Its roots develop from the radicle and the seed has two cotyledons or embryonic leaves.
• Their leaves have reticulate venation and have a pentamerous and tetramerous flower.
• Examples: mustard, bitter gourd, watermelon, brinjal, apple, mango, tamarind etc.

Important Points

Basic differences between monocot and dicot plants are: 

Thus, mustard is a dicotyledonous plant.

Key Points

• Plants absorb water and minerals from the roots.
• The roots have root hair.
• The root hair increases the surface area of the root for the absorption of water and mineral nutrients dissolved in water.
• The root hair is in contact with the water present between the soil particles.
• Plants have pipe-like vessels to transport water and nutrients from the soil.
• The vessels are made of special cells, forming the vascular tissue.
• A tissue is a group of cells that perform a specialised function in an organism.
• The vascular tissue for the transport of water and nutrients in the plant is called the xylem.
• Xylem vessels carry water and minerals from the roots to the leaves.​

Thus, uptake of water in plants takes place by xylem.

Additional Information 

• Phloem tubes carry sugar & other organic nutrients made by the plant from the leaves to the rest of the plant.
• Cambium is a thin layer of sap between sapwood and inner bark.
• The palisade layer is a cell layer just below the upper surface of a leaf.

• Vedas are supposed to be the first religious text of the Hindu religion.
• Veda means knowledge.
• There are four Vedas namely,
• Rig Veda - Oldest and most important Veda, contains the knowledge of chemistry and medical science.
• Yajur Veda - Only Veda, which is divided into two parts (i.e. Krishna Yajur Veda and Shukla Yajur Veda), contains the knowledge of all sacrificial formulas and weapons.
• Sam Veda - It is the Origin of Indian classical music.
• Atharva Veda - It contains the knowledge of Ayurveda, also charms and spells hence it is known as black Veda.

Key Points

• The Rigveda is divided into 10 mandalas (books).
• The first and tenth Mandalas are the youngest and the longest.
• The Gayatri mantra is in Rig Veda is taken from Mandala 3.
• Mandala 9 is completely devoted to Soma.
• The 10^th mandala contains the Purusha Sukta which explains the 4 Varnas that were born from the Mouth, arms, thighs, and feet of the Brahma or Purusha.
• Nasadiya Sukta which talks about the origin of the Universe is in the 10^th Mandala.

Thus, Rigveda is the first literacy source.