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Notes of Chapter 2 The Origin and Evolution of the Earth Class 11th Geography

Early Theories

Origin of the Earth

Nebular hypothesis

• Proposed by German philosopher Immanuel Kant.

• Mathematician Laplace revised it in 1796.

• Nebular Hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating.

• Later in 1900, Chamberlain and Moulton considered that a wandering star approached the sun.

• As a result, a cigar-shaped extension of material was separated from the solar surface.
→ As the passing star moved away, the material separated from the solar surface continued to revolve around the sun and it slowly condensed into planets.

Binary Theories

Later, the arguments considered of a companion to the sun to have been coexisting.

Revised 'Nebular hypothesis'

• Given by Otto Schmidt in Russia and Carl Weizascar in Germany in 1950.

• They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust.

• The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.

Modern Theories

Origin of the Universe

Big Bang Theory

• Also called expanding universe hypothesis.

• Edwin Hubble, in 1920, provided evidence that the universe is expanding.

• This theory considers the following stages in the development of the universe:

→ In the beginning, all matter forming the universe existed in one place in the form of a “tiny ball” (singular atom) with an unimaginably small volume, infinite temperature and infinite density.

→ At the Big Bang the “tiny ball” exploded violently. This led to a huge expansion. It is now generally accepted that the event of big bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy was converted into
matter. There was particularly rapid expansion within fractions of a second after the bang. Thereafter, the expansion has slowed down. Within first three minutes from the Big Bang event, the first atom began to form.

→ Within 300,000 years from the Big Bang, temperature dropped to 4,500 K (Kelvin) and gave rise to atomic matter. The universe became transparent.

• The expansion of universe means increase in space between the galaxies.

The Star Formation

• A galaxy contains a large number of stars.

• Galaxies spread over vast distances that are measured in thousands of light-years.

• A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula.
→ Eventually, growing nebula develops localised clumps of gas.

• These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars.

• The formation of stars is believed to have taken place some 5-6 billion years ago.

Formation of Planets

• The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.

• The gas cloud starts getting condensed and the matter around the core develops into small-rounded objects. These small-rounded objects by the process of cohesion develop into what is called planetesimals.

• Larger bodies start forming by collision, and gravitational attraction causes the material to stick together. Planetesimals are a large number of smaller bodies.

• These large number of small planetesimals accrete to form a fewer large bodies in the form of planets.

Our Solar System

• Our solar system consists of the sun (the star), 8 planets, 63 moons, millions of smaller bodies like asteroids and comets and huge quantity of dust-grains and gases.

• Out of the eight planets, mercury, venus, earth and mars are called as the inner planets as they lie between the sun and the belt of asteroids the other four planets are called the outer planets.

• Alternatively, the first four are called Terrestrial, meaning earth-like as they are made up of rock and metals, and have relatively high densities.

• The rest four are called Jovian or Gas Giant planets which means jupiter-like.

• All the planets were formed in the same period sometime about 4.6 billion years ago.

The difference between terrestrial and jovian planets:

• The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location.

• The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.

• The terrestrial planets are smaller and their lower gravity could not hold the escaping gases.

The Moon

• The moon is the only natural satellite of the earth.

Origin Theory

• In 1838, Sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating body.

• The whole mass became a dumb-bell-shaped body and eventually it broke.

• It was also suggested that the material forming the moon was separated from what we have at present the depression occupied by the Pacific Ocean.

Giant Impact or The Big Splat Theory

• A body of the size of one to three times that of mars collided into the earth sometime shortly after the earth was formed.

• It blasted a large part of the earth into space.

• This portion of blasted material then continued to orbit the earth and eventually formed into the present moon about 4.44 billion years ago.

Evolution of Earth

• The planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium.

• The earth has a layered structure.

• From the outermost end of the atmosphere to the centre of the earth, the material that exists is not uniform.

• From the surface to deeper depths, the earth’s interior has different zones.

Evolution of Lithosphere

• During its primordial stage, the earth was mostly in a volatile state.

• Due to gradual increase in density the temperature inside has increased.

• As a result the material inside started getting separated depending on their densities.

• This allowed heavier materials (like iron) to sink towards the centre of the earth and the lighter ones to move towards the surface.

• With passage of time it cooled further and solidified and condensed into a smaller size.

• This later led to the development of the outer surface in the form of a crust.

• During the formation of the moon, due to the giant impact, the earth was further heated up. It is through the process of differentiation that the earth forming material got separated into different
layers.

• Starting from the surface to the central parts, we have layers like the crust, mantle, outer core and inner core.

• From the crust to the core, the density of the material increases.

Evolution of Atmosphere and Hydrosphere

• The present composition of earth’s atmosphere is chiefly contributed by nitrogen and oxygen.

• There are three stages in the evolution of the present atmosphere.
→ The first stage is marked by the loss of primordial atmosphere.
→ In the second stage, the hot interior of the earth contributed to the evolution of the atmosphere.
→ Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis.

• The early atmosphere, with hydrogen and helium, is supposed to have been stripped off as a result of the solar winds.

• During the cooling of the earth, gases and water vapour were released from the interior solid earth which started the evolution of the present atmosphere.

• Continuous volcanic eruptions contributed water vapour and gases.

• As the earth cooled, the water vapour released started getting condensed.

• The carbon dioxide in the atmosphere got dissolved in rainwater and the temperature further decreased causing more condensation and more rains.

• The rainwater falling onto the surface got collected in the depressions to give rise to oceans.

NCERT Solutions of Chapter 2 The Origin and Evolution of the Earth

Notes of Chapter 3 Motions of the Earth Class 6th Geography

• The earth has two types of motions

→ Rotation

→ Revolution.

• Rotation is the movement of the earth on its axis.

• The movement of the earth around the sun in a fixed path or orbit is called Revolution.

• Orbital plane: The axis of the earth which is an imaginary line, makes an angle of 66½° with its orbital plane. The plane formed by the orbit is known as the orbital plane.

• Tilt of Axis: Earth’s axis is tilted at an angle of 66.5oon its orbital plane. On the other hand; the earth’s axis is tilted at 23.5o on the line which is perpendicular to its orbital plane.

• The circle that divides the day from night on the globe is called the circle of illumination.

• The earth takes about 24 hours to complete one rotation around its axis.

→ The period of rotation is known as the earth day means daily motion of the earth.

• The time taken by the earth to complete one revolution is called one year.

→ One year has 365 and ¼ days (365 days and 6 hours).

What Would Happen if the Earth Did Not Rotate?

• If there had been no rotation of the earth; one half of the earth would have been constantly in daylight and another half would have been constantly in dark.

→ The portion under sunlight would have been too hot.

• On the other hand, the portion in dark would have been freezing cold.

→ Such extremes of temperature could have made it impossible for life to thrive on our planet.

• Perihelion: The point at which a planet is nearest to the sun is called perihelion.

• Aphelion: The point at which a planet is farthest from the sun is called aphelion.

• On 21st March and 23rd September, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.

Summer Solstice

• On 21st June, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat.

• The areas near the poles receive less heat as the rays of the sun are slanting. The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months.

• Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the regions north of the equator.

• The longest day and the shortest night at these places occur on 21st June. At this time in the Southern Hemisphere all these conditions are reversed. It is winter season there.

• The nights are longer than the days.

Winter Solstice

• On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it.

• As the sun’s rays fall vertically at the Tropic of Capricorn (23½° S), a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights.

• The reverse happens in the Northern Hemisphere.

NCERT Solutions of Chapter 3 Motions of the Earth

Notes of Chapter 3 Interior of the Earth Class 11th Geography

Sources of Information about the Interior

• The earth’s radius is 6,370 km.

• As no one can reach the centre of the earth, most of our knowledge about the interior of the earth is largely based on estimates and inferences.

• There are two types of source of information available:

→ Direct Sources

→ Indirect Sources (Analysis of materials)

Direct Sources

• Surface rock or the rocks we get from mining areas.

→ Example: Gold mines in South Africa which are as deep as 3-4 km.

• Scientists have taken up a number of projects to penetrate deeper depths to explore the conditions in the crustal portions.

→ Example: “Deep Ocean Drilling Project” and “Integrated Ocean Drilling Project”. The deepest drill at Kola, in Arctic Ocean, has so far reached a depth of 12 km.

• Volcanic eruption.

→ As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis.

Indirect Sources

• We know through the mining activity that temperature and pressure increase with the increasing distance from the surface towards the interior in deeper depths.

→ Moreover, it is also known that the density of the material also increases with depth.

→ Knowing the total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of materials at different depths.

• Another source of information are the meteors that at times reach the earth.

→ However, it may be noted that the material that becomes available for analysis from meteors, is not from the interior of the earth but the material and the structure observed in the meteors are similar too that of the earth.

→ They are solid bodies developed out of materials same as, or similar to, our planet.

• The other indirect sources include gravitation, magnetic field, and seismic activity.

→ The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator.

→ Magnetic surveys also provide information about the distribution of magnetic materials in the crustal portion, and thus, provide information about the distribution of materials in this part.

→ Seismic activity is one of the most important sources of information about the interior of the earth.

Earthquake

• An earthquake in simple words is shaking of the earth.

• It is caused due to release of energy, which generates waves that travel in all directions.

Why does the earth shake?

• Rocks along a fault tend to move in opposite directions.

• As the overlying rock strata press them, the friction locks them together. However, their tendency to move apart at some point of time overcomes the friction.

→ As a result, the blocks get deformed and eventually, they slide past one another abruptly. This causes a release of energy, and the energy waves travel in all directions.

• The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre.

• The point on the surface, nearest to the focus, is called epicentre. It is the first one to experience the waves.

Earthquake Waves

• All natural earthquakes take place in the lithosphere (depth up to 200 km from the surface of the earth.)

• An instrument called ‘seismograph’ records the waves reaching the surface.

• Earthquake waves are basically of two types

→ Body waves

→ Surface waves.

• Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth.

• The body waves interact with the surface rocks and generate new set of waves called surface waves. → These waves move along the surface.

• Body Waves are of two types - P-Waves and S-Waves

P-Waves

• These waves move faster and are the first to arrive at the surface and are also called ‘primary waves’.

• These are similar to sound waves and travel through gaseous, liquid and solid materials as sound.

• P-waves vibrate parallel to the direction of the wave.

S-Waves

• These waves arrive at the surface with some time lag and are called secondary waves.

• These waves can travel only through solid materials which has helped scientists to understand the structure of the interior of the earth.

• Reflection causes waves to rebound whereas refraction makes waves move in different directions.

• These waves are more destructive as they cause displacement of rocks, and hence, the collapse of structures occurs.

• The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass.

Shadow Zone

• Earthquake waves get recorded in seismo-graphs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’.

• A zone between 105° and 145° from epicentre was identified as the shadow zone for both the types of waves.

• The entire zone beyond 105° does not receive S-waves. The shadow zone of S-wave is much larger than that of the P-waves.

• The shadow zone of P-waves appears as a band around the earth between 105° and 145° away from the epicentre.

Types of Earthquakes

• Tectonic Earthquakes: generated due to sliding of rocks along a fault plane.

• Volcanic Earthquakes: A special class of tectonic earthquake. These are confined to areas of active volcanoes.

• Collapse earthquakes: In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors.

• Explosion earthquakes: Ground shaking may also occur due to the explosion of chemical or nuclear
devices.

• Reservoir induced earthquakes: The earthquakes that occur in the areas of large reservoirs.

Measuring Earthquakes

• The earthquake events are scaled either according to the magnitude or intensity of the shock.

Richter Scale

• The magnitude scale is known as the Richter scale. The magnitude is expressed in absolute numbers, 0-10.

Mercalli Scale

• The intensity scale is named after Mercalli, an Italian seismologist. The range of intensity scale is from 1-12.

Effects of Earthquakes

(i) Ground Shaking
(ii) Differential ground settlement
(iii) Land and mud slides
(iv) Soil liquefaction
(v) Ground lurching
(vi) Avalanches
(vii) Ground displacement
(viii) Floods from dam and levee failures
(ix) Fires
(x) Structural collapse
(xi) Falling objects
(xii) Tsunami

• The first six listed above have some bearings upon landforms, while others may be considered the effects causing immediate concern to the life and properties of people in the region.

• The effect of tsunami would occur only if the epicentre of the tremor is below oceanic waters and the magnitude is sufficiently high.

Structure of the Earth

The Crust

• It is the outermost solid part of the earth.

• It is brittle in nature.

• The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust.

• The continental crust is thicker in the areas of major mountain systems.

• The type of rock found in the oceanic crust is basalt. The mean density of material in oceanic crust is 2.7 g/cm³.

The Mantle

• The portion of the interior beyond the crust is called the mantle.

• It extends from Moho’s discontinuity to a depth of 2,900 km.

• The upper portion of the mantle is called asthenosphere.
→It is the main source of magma that finds its way to the surface during volcanic eruptions.

• The crust and the uppermost part of the mantle are called lithosphere.
→ Its thickness ranges from 10-200 km.

• The lower mantle extends beyond the asthenosphere. It is in solid state

The Core

• The core-mantle boundary is located at the depth of 2,900 km.

• The outer core is in liquid state while the inner core is in solid state.

• The density of material at the mantle core boundary is around 5 g/cm³3

.

• The core is made up of very heavy material mostly constituted by nickel and iron.

• It is sometimes referred to as the nife layer.

Volcanoes and Volcanic Landforms

• A volcano is a place where gases, ashes and/or molten rock material – lava – escape to the ground.

• A volcano is called an active volcano if the materials mentioned are being released or have been released out in the recent past.

• Volcanoes are classified on the basis of:
→ Nature of eruption
→ Form developed at the surface.

Types of Volcanoes

Shield Volcanoes

• Barring the basalt flows, the shield volcanoes are the largest of all the volcanoes on the earth.

• The Hawaiian volcanoes are the most famous examples.

• These volcanoes are mostly made up of basalt, a type of lava that is very fluid when erupted.

• They become explosive if somehow water gets into the vent; otherwise, they are characterised by low-explosivity.

Composite Volcanoes

• These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt.

• These volcanoes often result in explosive eruptions.

• The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province.

Mid-Ocean Ridge Volcanoes

• These volcanoes occur in the oceanic areas.

• There is a system of mid-ocean ridges more than 70,000 km long that stretches through all the ocean basins.

• The central portion of this ridge experiences frequent eruptions.

Volcanic Landforms

Intrusive Forms

• The lava that is released during volcanic eruptions on cooling develops into igneous rocks.

• The cooling may take place either on reaching the surface or also while the lava is still in the crustal portion.

• Depending on the location of the cooling of the lava, igneous rocks are classified as volcanic rocks (cooling at the surface) and plutonic rocks (cooling in the crust).

• The lava that cools within the crustal portions assumes different forms and these forms are called intrusive forms.

Caldera

• These are the most explosive of the earth’s volcanoes.

• They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure.

• The collapsed depressions are called calderas.

Flood Basalt Provinces

• These volcanoes outpour highly fluid lava that flows for long distances.

• Some parts of the world are covered by thousands of sq. km of thick basalt lava flows.

Batholiths

• Batholiths are the cooled portion of magma chambers.

• They appear on the surface only after the denudational processes remove the overlying materials.

• They cover large areas, and at times, assume depth that may be several km. These are granitic bodies.

Lacoliths

• These are large dome-shaped intrusive bodies with a level base and connected by a pipe-like conduit from below.

• It resembles the surface volcanic domes of composite volcano, only these are located at deeper depths.

• It can be regarded as the localised source of lava that finds its way to the surface.

Lapolith, Phacolith and Sills

• As and when the lava moves upwards, a portion of the same may tend to move in a horizontal direction wherever it finds a weak plane.

• It may get rested in different forms. In case it develops into a saucer shape, concave to the sky body, it is called lapolith.

• A wavy mass of intrusive rocks, at times, is found at the base of synclines or at the top of anticline in folded igneous country. Such wavy materials have a definite conduit to source beneath in the form of magma chambers (subsequently developed as batholiths). These are called the phacoliths.

• The near horizontal bodies of the intrusive igneous rocks are called sill or sheet, depending on the thickness of the material. The thinner ones are called sheets while the thick horizontal deposits are called sills.

Dykes

• When the lava makes its way through cracks and the fissures developed in the land, it solidifies almost perpendicular to the ground.

• It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes.

• These are the most commonly found intrusive forms in the western Maharashtra area.

NCERT Solutions of Chapter 3 Interior of the Earth

Extra Questions for Class 10th: Ch 7 Control and Coordination (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Name any two types of tropic movement in plants.

Answer
(i) Geotropism (ii) Chemotropism

Q2. Name the plant hormone that inhibits growth and also help in wilting of leaves.

Answer
The plant hormone that inhibits growth and also helps in wilting of leaves in abscisic acid.

Q3. Which hormone is responsible for the secondary sexual characters in male human beings?

Answer
Testosterone is responsible for the secondary sexual characters in male human beings.

Q4. Name the sensory receptors found in the nose and the tongue.

Answer
Olfactory receptors and gustatory receptors are the sensory receptors found in nose and on the tongue respectievely.

Q5. . How do the shoot and roots of a plant respond to the pull of earth's gravity ?

Answer
Roots grow downwards, towards gravity while shoot usually grow upwards and away from earth.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. Name one plant hormone which inhibit growth. Write its one more function.

Answer

Abscisic acid is a plant hormone which inhibits growth.

It’s one more function is that it helps in closure of stomata to decrease loss of water.

Q2.(i) Name the part of brain which controls

(a)Voluntary actions

(b)Involuntary actions

(ii) What is the significance of the peripheral nervous system? Name the components of nervous system?

Answer

(i) Voluntary actions: are controlled by cerebellum

(ii) Involuntary actions: are controlled by medulla

Q3. How does feedback mechanism regulate the hormone secretion?

Answer

The feedback mechanism regulates the timing and amount of hormone to be secreted. For example, if a person has more sugar in his blood, it is detected by cells of pancreas. As a result, more insulin will be secreted to oxidise the sugar. In opposite case, the secretion of insulin will be depleted.

Q4. Explain the cause of shoots of the plant bending towards light.

Answer

Stems are positively phototrophic and bend towards the direction of light. The movement is due to occurrence of more auxin on the darker side and lesser auxin on the illuminated side. As a result, there is more growth on the darker side which causes the stem to bend towards light.

Short Answer Questions-II (SAQs-II): 3 Marks

Q1. How do auxins promotes the growth of a tendril around a support. Describe in berief?

Answer

Auxins produced in the shoot tip move downwards in the plant. These auxins cause cell elongation in the growing tissues.

In the tendrils, auxins move away from the point of contact with the supporting object. More growth occurs on the side away from the support. As a result of unequal growth on the two sides, the tendril coils around the support.

Q2. (a) State the function of plant hormones. Name a plant hormone which is essential for cell division. (b) Name the hormone which is involved in phototropism. Explain its role.

Answer

(a) Plant hormones are the chemicals secreted by the plants which helps to co-ordinate growth, development and responses to the environment.

Cytoldnin is hormone involved in phototropism.

(b) Auxin

When growing plant detects light, auxin is synthesized at the shoot tip and helps the cell to grow longer. When light comes from other side of the plant, auxin diffuses to shady side of the shoot.

Q3. Hormones are needed by our body in an appropriate amount, slightly more or less secretion causes disorder in our body. Illustrate this by using three example.

Answer

(a) Hypersecration (more secration) and hyposecration (less secration) of different hormones may cause certain disorders.

They are

(i) Gigantism and dwarfism: Hypersecration of growth hormone can cause gigantism. Hyposecration of growth harmone can cause dwarfism.

(ii) Goitre: Iodine acts as the necessary component for the synthesis of thyroxin harmone from thyroid gland.

(iii) Diabetis mellitus: Insuline secrated from pancreas helps to lower the blood glucose level. When secrated in lower amount, body suffers from diabetes.

Q4. List three differences in the movement of leaves of a Touch-me-not plant (the plant of Mimosa family) when touched and movement of a tendril towards a support.

Answer

Mimosa Leaves	Tendril
(i) Growth independent response,.	(i) Growth dependent.
(ii) It is a fast process.	(ii) It is a slow process.
(iii) It is non-directonal.	(iii) It is directional.

Long Answer Questions (LAQs): 5 Marks

Q1. Why we call pituitary gland as master gland? Where is it located and what are the functions?

Answer

The pituitary glands in our body is meant to control various activities of other glands. Hence called the master glands.

It is located just below the hypothalamus at the base of the brain.

It secretes five important hormones which are:

(i) Growth Hormone: It regulates the growth and development of bones and muscles.

(ii) Tropic Hormone: It regulates the secretion from other endocrine glands.

(iii) Prolactin Hormone: It regulates function of mammary glands in females.

(iv) Vasopressin Hormone: It regulates water and electrolyte balance of the body.
(v) Oxytocin hormone: It regulates ejection of milk during lacation.

Q2. (a) Write the names and one function of each of any three growth hormones in plants. (b) In the absence of muscle cells, how do plant cells show movement?

Answer

(a) Three growth hormones in plants are:

(i) Auxin—It is synthesised in the young tip of roots and shoots. It promotes elongation and division of cell and root formation.

(ii) Gibberellins—They help in the growth of the stem.
(iii) Cytokines—They promote cell division and delay leaf ageing

(b) The ability of a plant to detect change and respond to that change is termed as the sensitivity of the plant. Yet plants have no nervous system and no muscle tissue, they use electrical and chemical means to convey the information from one cell to another cell. The leaves of the sensitive plant (Mimosa pudica) folds up in response to touch. These leaf movements are independent of growth whereas, the directional movement of the shoot of a germinating seedling breaking through the soil is growth dependent.

NCERT Solutions of Chapter 7 Control and Coordination

Notes of Chapter 7 Control and Coordination

Extra Questions for Class 10th: Ch 8 How do Organisms to Reproduce? (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Name the part of Bryophyllum where the buds are produced for vegetative propagation.

Answer

Leaf notches.

Q2. Name the method by which Hydra reproduces. Is this method sexual or asexual ?

Answer

Hydra reproduces by Budding. It is an asexual reproduction.

Q3. Name the causative agent of the disease "Kala-azar" and its mode of asexual reproduction.

Answer

Leishmania, Binary fission.

Q4. List two functions of ovary of human female reproductive system.

Answer

Two functions of Ovary :

(i) To Produce female gamete / ovum.

(ii) To secrete femele hormones / estrogen and Progesterone

Q5. In the human female reproductive system where does fertilization occur?

Answer

Oviduct or Fallopian tube.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. What is binary and multiple fission? Name the organisms in which they occur.

Answer

Binary fission is the division of one parent cell into two identical daughter cells. It takes place in Amoeba, Paramecium, Euglena and other protozoa.

Multiple fission is the process in which one single celled organism divides into many daughter cells within a cyst. These are released when the cyst breaks. This takes place in Plasmodium (malarial parasite).

Q2. What is budding? Name two organisms that reproduce asexually by budding.

Answer

In budding a small part of the parents body grows out as a bud which then detaches

and becomes a new organism. Hydra and yeast reproduce by budding.

Q3. What is germination of seed?

Answer

When the seed gets the right conditions the embryo within it starts growing to form the shoot and the root. When the embryo emerges out of the seed to form a new seedling it is called the germination of seed.

Q4. What is menstruation? Why does it occur?

Answer

Menstruation is the process of breakdown and removal of the inner lining of the uterus along with the blood vessels in the form of vaginal bleeding. This happens after every 28 days if the egg is not fertilised. This takes place in human females and in some primates.

Short Answer Questions-II (SAQs-II): 3 Marks

Q1. What are three advantages of vegetative propagation ?

Answer

Three advantages of vegetative propagation:

(i) Plants unable to produce viable seeds can be produced by this method.

(ii) By this method, Plants can bear flowers and fruits earlier than those produced from seeds.

(iii) The characters (traits) of the parent plant can be preserved by this method.

Q2 . What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process ? How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?

Answer

Reproduction results in the production offspring similar to parents in body design and form. The exact blue prints of body design is inherited in the offspring due to DNA replication. The imperfect DNA copying results in genetic variations. This can be both useful and harmful for the offspring.

The useful variations gets selected in nature and helps organism to survive in the changing environment while as harmful variation gets eliminated.

If each new generation is to be the combination of the DNA copies from two pre-existing individuals, then each new generation will end up having twice the amount of DNA that the previous generation had. In sexual reproduction, the gametes usually contain half number of chromosomes and same numbers present in the body cells. These haploid gametes when fuse produce a new cell with double number of chromosomes than the gametes and same as the body cells. In this way organisms restrict doubling of DNA and maintain the chromosome number.

Q3. (a) With the help of a diagram, show asexual reproduction in Rhizopus ?
(b) How this method is advantageous for Rhizopus ?

Answer

(a) Spore formation takes place in Rhizopus. Rhizopus consists of fine thread like projection called hyphae. It has a knob like structure which is involved in reproduction called sporangia, containing spores, that develop into new Rhizopus.

More number of spores are produced which can easily help Rhizopus to spread.

Q4. In the context of reproduction of species state the main difference between fission and fragmentation. Also give one example of each.

Answer

Fission : It is the method of asexual reproduction in unicellular forms of life. In this process the parent organism splits to form two or more daughter cells. Example : Ameoba

A Fragmentation : It Is the process found in multicellular organisms. The filament breaks up into two or more pieces upon maturation. These pieces then grow into new individuals.

Example : Spirogyra.

Long Answer Questions (LAQs): 5 Marks

Q1.(a) State in brief the functions of the following organs in the human female reproductive system: Ovary, Fallopian tube, Uterus.

(b) Why mensuration take place?

Answer

(a)

• Functions of Ovary:

(i) Production of female gamete

(ii) Production of female hormone

• Functions of Fallopian tube:

(i) Site of fertilization

(ii) Transfer of female gamete from ovary

Functions of Uterus:
(i) Implantation of zygote/ fertilise egg/embryo.
(ii) Nourishment to the developing embryo.

(b) Menstruation- It is the periodic breakdown of uterine lining and its removal along with blood and mucous in (post puberatal stage of a) human female. Uterine lining is required to nourish the embryo that is formed if fertilization takes place. In absence of fertilization, the lining is not required and hence is shed in the form of menstruation.

Q2. (a) Write the name of the male reproductive organ that produces sperms and secrete a hormone. Name the hormone secreted and state its function.
(b) Write the site of fertilization and the part where the zygote gets implanted in the human female.
(c) State, in brief, how an embryo gets its nourishment inside the mother's body.

Answer

(a) A testosterone is the hormone produced in the testes that stimulates the development of secondary sexual characters in males. Its important functions are :

(i) Development, maturation and functioning of the male accessory sex organs like vas deferens and seminal vesicles.

(ii) Stimulate muscular growth, growth of facial hair, low pitch voice, etc., sperm production. All these activities are hindered in the absence of testosterone.

(b) Fertilization takes place in ampulla region of fallopian tube and zygote gets implanted in the uterus.

(c) Embryo is present in the womb of a mother where it is connected with the uterine wall of mother by placenta. The foetus receives oxygen, nourishment and other life supporting things from mother through this placenta.

NCERT Solutions of Chapter 8 How do Organisms Reproduce?

Notes of Chapter 8 How do Organisms Reproduce?

पठन सामग्री और नोट्स (Notes)| पाठ 2 - संघवाद (Sanghvad) Loktantrik Rajniti Class 10th

संघवाद क्या है?

संघीय शासन व्यवस्था में सर्वोच्च सत्ता केंद्रीय प्राधिकार और उसकी विभिन्न आनुषंगिक इकाइयों के बीच बँट जाती है।

संघवाद की विशेषताएं

1. यहाँ सरकार दो या अधिक स्तरों वाली होती है।

2. अलग-अलग स्तर की सरकारें एक ही नागरिक समूह पर शासन करती हैं पर कानून बनाने, कर वसूलने और प्रशासन का उनका अपना-अपना अधिकार-क्षेत्र होता है।

3. संविधान के मौलिक प्रावधानों को किसी एक स्तर की सरकार अकेले नहीं बदल सकती। ऐसे बदलाव दोनों स्तर की सरकारों की सहमति से ही हो सकते हैं।

4. अदालतों को संविधान और विभिन्न स्तर की सरकारों के अधिकारों की व्याख्या करने का अधिकार है।

5. वित्तीय स्वायत्तता निश्चित करने के लिए विभिन्न स्तर की सरकारों के लिए राजस्व के अलग-अलग स्रोत निर्धारित हैं।

संघों के प्रकार

• दो या अधिक स्वतंत्र राष्ट्रों को साथ लाकर एक बड़ी इकाई गठित करने का| साथ आकर संघ बनाने के उदाहरण हैं-संयुक्त राज्य अमरीका, स्विट्जरलैंड और ऑस्ट्रेलिया वगैरह।

• बड़े देश द्वारा अपनी आंतरिक विविधता को ध्यान में रखते हुए राज्यों का गठन करना और फिर राज्य और राष्ट्रीय सरकार के बीच सत्ता का बँटवारा कर देना। भारत, बेल्जियम और स्पेन इसके उदाहरण हैं।

भारत में संघीय व्यवस्था

• संविधान ने मैलिक रूप से दो स्तरीय शासन व्यवस्था का प्रावधान किया था-संघ सरकार (या हम जिसे केंद्र सरकार कहते हैं) और राज्य सरकारें।

• बाद में पंचायतों और नगरपालिकाओं के रूप में संघीय शासन का एक तीसरा स्तर भी जोड़ा गया।

संविधान में स्पष्ट रूप से केंद्र और राज्य सरकारों के बीच विधायी अधिकारों को तीन हिस्से में बाँटा गया हैं। ये तीन सूचियाँ इस प्रकार हैं:

• संघ सूची में राष्ट्रीय महत्व के विषय शामिल हैं।

• राज्य सूची में राज्य और स्थानीय महत्व के विषय शामिल हैं।

• समवर्ती सूची में शिक्षा, वन, मज़दूरसंघ, विवाह, गोद लेना और उत्तराधिकार जैसे वे विषय हैं जो केंद्र के साथ राज्य सरकारों की साझी दिलचस्पी में आते हैं।

• हमारे संविधान के अनुसार 'बाकी बचे' विषय केंद्र सरकार के अधिकार क्षेत्र में चले जाते हैं।

भारतीय संघ की विशेषताएं

• भारत के सभी राज्यों के पास समान शक्तियां नहीं हैं।

• संसद अपने स्वयं के शक्ति साझाकरण में परिवर्तन नहीं कर सकती है। इन परिवर्तनों के लिए कम से कम दो तिहाई बहुमत के साथ संसद के दोनों सदनों की मंजूरी की आवश्यकता है।

• न्यायपालिका संवैधानिक प्रावधानों और प्रक्रियाओं के कार्यान्वयन की देखरेख करती है।

संघीय व्यवस्था कैसे चलती है?

भाषायी राज्य

1947 में, नए राज्य बनाने के लिए भारत के कई पुराने राज्यों की सीमाएं बदल गए हैं:

• भाषा के आधार पर।

• संस्कृति के आधार पर।

भाषा नीति

• हमारे संविधान में किसी एक भाषा को राष्ट्रभाषा का दर्जा नहीं दिया गया है दिया गया|

• हिंदी को अनुसूचित भाषा के रूप में पहचाना गया है।

• हिंदी के अलावा, संविधान द्वारा अनुसूचित भाषाओं के रूप में मान्यता प्राप्त 21 अन्य भाषाएं हैं।

• राज्यों की भी अपनी राजकीय भाषाएँ हैं।

• हिंदी के साथ अंग्रेजी का भी प्रयोग राजकीय उद्देश्यों के लिए किया जाता है।

केंद्र-राज्य सम्बन्ध

• संविधान द्वारा केंद्र और राज्यों के बीच शक्तियों के साझाकरण ने भारत में संघवाद को भी मजबूत किया है।

• 1990 के बाद से की अवधि में देश के अनेक राज्यों में क्षेत्रीय दलों का उदय हुआ। यही दौर केंद्र में गठबंधन सरकार की शुरुआत का भी था। चूंकि किसी एक दल को लोकसभा में स्पष्ट बहुमत नहीं मिला इसलिए प्रमुख राष्ट्रीय पार्टियों को क्षेत्रीय दलों समेत अनेक पार्टियों का गठबंधन बनाकर सरकार बनानी पड़ी।

• इससे सत्ता में साझेदारी और राज्य सरकारों की स्वायत्तता का आदर करने की नई संस्कृति पनपी। इस प्रवृत्ति को सुप्रीम कोर्ट के एक बड़े फैसले से भी बल मिला। इस फैसले के कारण राज्य सरकार को मनमाने ढंग से भंग करना केंद्र सरकार के लिए मुश्किल हो गया।

भारत में विकेंद्रीकरण

• जब केंद्र और राज्य सरकार से शक्तियां लेकर स्थानीय सरकारों को दी जाती हैं तो इसे सत्ता का विकेंद्रीकरण कहते हैं।

• 1992 से पहले, स्थानीय सरकारें सीधे राज्य सरकारों के अधीन थे।
→ नियमित चुनाव नहीं होते थे।
→ स्थानीय सरकारों के पास अपने स्वयं के संसाधन या शक्तियां नहीं थीं।

• वास्तविक विकेंद्रीकरण की दिशा में एक बड़ा कदम 1992 में उठाया गया। संविधान में संशोधन करके लोकतांत्रिक शासन व्यवस्था के इस तीसरे स्तर को ज्यादा शक्तिशाली और प्रभावी बनाया गया।
→ अब स्थानीय स्वशासी निकायों के चुनाव नियमित रूप से कराना संवैधानिक बाध्यता है।
→ निर्वाचित स्वशासी निकायों के सदस्य तथा पदाधिकारियों के पदों में अनूसचित जातियों, अनुसूचित जनजातियों और पिछड़ी जातियों के लिए सीटें आरक्षित हैं।
→ कम से कम एक तिहाई पद महिलाओं के लिए आरक्षित हैं।
→ हर राज्य में पंचायत और नगरपालिका चुनाव कराने के लिए राज्य चुनाव आयोग नामक स्वतंत्र संस्था का गठन किया गया है।
→ राज्य सरकारों को अपने राजस्व और अधिकारों का कुछ हिस्सा इन स्थानीय स्वशासी निकायों को देना पड़ता है। सत्ता में भागीदारी की प्रकृति हर राज्य में अलग-अलग है।

गाँव की स्थानीय सरकार

पंचायती राज नाम से लोकप्रिय रूप से जाना जाता है।

→ ग्राम पंचायत: यह पूरे गांव के लिए निर्णय लेने वाला परिषद है।

→ पंचायत समिति: कई ग्राम पंचायतों को मिलाकर पंचायत समिति का गठन होता है|

→ जिला परिषद: किसी जिले की सभी पंचायत समितियों को मिलाकर जिला परिषद् का गठन होता है।

शहरों की स्थानीय सरकार

• शहरों में नगर पालिका होती है। बड़े शहरों में नगरनिगम का गठन होता है।

• नगरपालिका प्रमुख नगरपालिका के राजनीतिक प्रधान होते हैं। नगरनिगम के ऐसे पदाधिकारी को मेयर कहते हैं।

NCERT Solutions of पाठ 2 - संघवाद

Extra Questions of पाठ 2 - संघवाद

Notes of Chapter 3 Motions of the Earth Class 6th Geography

Maps

• A map is a representation or a drawing of the earth’s surface or a part of it drawn on a flat surface according to a scale. But it is impossible to flatten a round shape completely.

Different types of Maps

Physical Maps

• Maps showing natural features of the earth such as mountains, plateaus, plains, rivers, oceans etc. are called physical or relief maps.

Political Maps

• Maps showing cities, towns and villages, and different countries and states of the world with their boundaries are called political maps.

Thematic Maps

• Some maps focus on specific information; such as road maps, rainfall maps, maps showing distribution of forests, industries etc. are known as thematic maps.

Components of Maps

Distance

• Maps are two-dimensional drawings. It reduces the entire world or a part of the world on a small sheet of paper. While making a map, cartographers pay attention to properly represent the distance between two places. This helps us in finding the actual distance between two places.

• Small Scale Map: When a large area is shown on a small map, such a map is called a small scale map. Example; map of a country or state.

• Large Scale Map: When a small area such as a village is shown on a map, such a map is called a large scale map. A map of a neighbourhood is another example of large scale map. A large scale map gives more details compared to a small scale map.

Direction

• A map also contains information about directions.

• On most of the maps, you will usually see an upward arrow and the letter ‘N’. This shows the north direction. Once we know the north, we can easily find the other directions. North, South, East and West are the four major directions. These are called Cardinal Directions.

• Some maps also show the intermediate directions, viz. north-east, south-east, south-west and north-west.

Compass

• Compass is very useful for finding directions at a place.

• This is a small circular box with a magnetic needle inside.

• The needle of the compass always points in the north-south direction.

• Compass has been used by travellers and sailors since ages.

Symbols

• Cartographers also need to show various details; like important structures, landmarks, etc. on a map. These things are shown by some standard symbols on the map.

• While using colours to show different themes and items on a map; certain conventions are followed. Mountains are usually shown in brown colour, plains in green, water body in blue and plateau is shown in yellow.

Sketch

• A drawing based on memory is called a sketch. A sketch is not made to scale. A sketch map is useful when you need to show directions to your house to your friend.

Plan

• Drawing of a small area on a large scale is called a plan. Architects usually make plans to show the layout of a house.

NCERT Solutions of Chapter 4 Maps

Extra Questions of Chapter 4 Maps

Notes of Chapter 5 Major Domains of the Earth Class 6th Geography

• The surface of the earth is a complex zone. It can be divided into three main portions, viz. lithosphere, atmosphere and hydrosphere.

Lithosphere

• The solid portion of the earth is called lithosphere.

• It is composed of rocks of the earth’s crust.

• There is a thin layer of soil on top that contains mineral nutrients which sustain various organisms.

• The earth’s surface can be divided into two main parts, viz. the continents and the ocean basins.
→ Continents: The huge landmasses on the earth are called continents.
→ Ocean Basins: The huge water bodies on the earth are called ocean basins.

Continents

• There are seven continents and all of them are separated by large water bodies. The seven continents of the world are; Asia, Europe, Africa, North America, South America, Australia and Antarctica.

• Asia: This is the largest continent. Asia covers about one-third of the total land area of the earth. This continent lies in the eastern hemisphere.

• Europe: Europe lies to the west of Asia and is much smaller than Asia. It is bound by water bodies from three sides.

•Africa: Africa is the second largest continent. The major portion of Africa lies in the northern hemisphere.

• North America: It is the third largest continent. North America and South America are connected to each other by the Isthmus of Panama.

• Isthmus: A narrow strip of land which joins two landmasses is called isthmus. North America lies in the northern hemisphere and western hemisphere.

• South America: A major portion of South America is in southern hemisphere. This continent is surrounded by two oceans, viz. the Atlantic and Pacific oceans.

• Australia: This is the smallest continent. It lies entirely in the southern hemisphere. Since Australia is surrounded on all sides by ocean hence it is called the island continent.

• Antarctica: This is a huge continent and is present on the South Polar Region. In fact, the South Pole lies at the centre of this continent.

Oceans

• All the oceans of the world are connected to each other. Due to this, the level of sea water is same everywhere. Elevation of land is measured from the sea level and the sea level is taken as zero.

• Waves, tides and ocean currents are the three main movements of ocean water. There are five major oceans, viz. Pacific, Atlantic, Indian, Arctic and Southern oceans.

• Pacific Ocean: This is the largest ocean. It is almost circular in shape. The Pacific Ocean is surrounded by Asia, Australia, North America and South America.

• Atlantic Ocean: This is the second largest ocean. It is S-shaped. North America and South America are to the west of this ocean. Europe and Africa are on the east of this ocean.

• Indian Ocean: Indian Ocean is the only ocean to be named after a country. This ocean is almost triangular in shape. Asia is towards north, Africa is towards west and Australia is towards east of this ocean.

• Southern Ocean: This Ocean encircles Antarctica. It extends northwards up to 60oS latitude.

• Arctic Ocean: This Ocean is within the Arctic Circle. It surrounds the North Pole. It is bound by the northern coasts of North America and Eurasia.

Atmosphere

• Atmosphere plays an important role in the environment on earth.

• Atmosphere is made of air which is composed of many gases, water vapour and dust particles.

• Composition of Air: Air is mainly composed of nitrogen and oxygen. 78% of the air is composed of nitrogen, 21% is composed of oxygen and rest 1% is composed of carbon dioxide, argon and many other gases.

• Role of Nitrogen: Nitrogen is important for plants because plants make many important molecules from nitrogen.

• Role of Oxygen: Oxygen is required by living beings for respiration. Moreover, oxygen is also required for burning various fuels.

• Role of Carbon Dioxide: Carbon dioxide is utilized by plants during photosynthesis. You may recall that photosynthesis is the process by which plants make food.

Layers of Atmosphere

• The atmosphere can be divided into many layers.

• Troposphere is at the bottom. This is followed by stratosphere, mesosphere, thermosphere and exosphere.

• The density of atmosphere changes with height. Air is at maximum density at the sea level and becomes rarer as we go higher.

• Humans are comfortable while breathing under normal pressure. When the atmospheric pressure becomes low, it becomes difficult to breathe.

• Atmospheric pressure is very low at high mountains. Due to this, mountaineers need to carry oxygen cylinders so that they can breathe comfortably at high altitude. The difference in pressure also plays a role in wind movements.

• Air moves from high pressure to low pressure. Moving air is called wind.

Hydrosphere

More than 71% of the earth’s surface is covered with water. But 97% of the total water on earth is available as saline water in oceans and seas.

Biosphere

• The narrow zone of contact between the lithosphere, hydrosphere and atmosphere is called biosphere.

• Life exists in this zone. A variety of organisms exist on earth. All the living beings are linked to each other for their survival. They are also linked to various non-living things for their survival.

NCERT Solutions of Chapter 5 Major Domains of the Earth

Notes of Chapter 6 Major Landforms of the Earth Class 6th Geography

• Landform is a natural feature of the earth’s surface.

• The surface of the earth varies from one place to another. The main landforms are; mountains, plateau and plains.

• There are two processes which lead to formation of different landforms:

→ Internal process

→ External process

Internal Process

• The movement of earth’s surface results in internal process.

• The internal process results in a portion of the earth’s surface getting elevated or getting sunk.

External Process

• Continuous wearing down and rebuilding of the earth’s surface is the result of external process.

Erosion

• Removal of materials is called erosion.

• Erosion results in lowering of the earth’s surface.

• It is carried out by various agents; like wind and water.

Deposition

• Deposition of materials results in rebuild of the earth’s surface. It also results in the surface getting elevated. Wind and water are the main agents of deposition.

Glacier

• Permanently frozen rivers of ice are called glaciers. Glaciers are found in some of the very high mountains.

Mountains

• A mountain is the natural elevation of the earth’s surface.

• It may be narrow at top and broad at the base.

• The elevation of mountain is considerably more than that of surrounding area.

• Temperature reduces with increase in altitude. Due to this, very high mountains are usually covered with snow.

Population at Mountains

• Because of steep slopes, less amount of land is available for farming on mountains. This is also difficult to build houses on steep slopes. Hence, less number of people lives on the mountains.

Mountain Range

• When mountains are arranged in a line, then it is called a mountain range.

• Some of the mountain systems contain ranges spread over hundreds of kilometres.

Types of Mountains

• There are three types of mountains, viz. fold mountains, Block Mountains and volcanic mountains.

→ Fold Mountains: When a tectonic plate gets pressure from two sides, it gets folded. Some of its portion becomes elevated and forms the mountains. The depressions form the valleys. The Himalayas, The Andes and the Alps are examples of Fold Mountain.

→ Block Mountains: When large areas are broken and displaced vertically, Block Mountains are formed. In this case, the uplifted blocks are called horsts.

→ Volcanic Mountains: A mountain formed due to volcanic activity is called Volcanic Mountain. Examples of Volcanic Mountains are; Mt. Kilimanjaro and Mt. Fujiyama.

Importance of Mountains

• Mountains are rich sources of water. Many important rivers originate from glaciers on mountains.

• River valleys and terraces are ideal for cultivation.

• Mountains are rich in flora and fauna.

• Mountains provide many forest produce; like wood, herbs, medicinal plants, honey, catechu, etc.

• Mountains are ideal tourist spots.

Plateau

• A plateau is a flat and elevated land.

• A plateau is at higher elevation than the surrounding areas.

• It may have one or more sides with steep slopes.

• It can be young or old.

• The height of plateau can be from a few hundred meters to several thousand meters.

Importance of Plateau

• Plateaus are rich in mineral deposits. Many mining belts in the world are located in the plateau areas.

• Most of the mining areas in India are in the Chhotanagpur Plateau in Jharkhand, Orissa and Chhattisgarh.

• The African plateau is famous for mines of gold and diamond.

Plains

• Plains are flat lands and are generally not more than 200 m above mean sea level. Some plains are extremely level, while others may be slightly rolling and undulating.

Importance of Plains

• Plains are usually highly fertile and hence most ideal for cultivation.

• It is very easy to make transport network in the plains.

• Due to above mentioned factors, plains are the best areas for human habitation.

• Most of the densely populated areas of the world are in the plains.

• The Indo-Gangetic Plains in India is among the most densely populated regions of the world.

Landforms and the People

• Humans have been living in most of the terrains.

• Life is difficult in mountain areas because of rugged terrain. Hence, mountain areas are sparsely populated.

• Life is somewhat easier in the plateaus; compared to in mountains.

• Life is the easiest in the plains.

• In all types of terrains, natural calamities always pose threat. Earthquakes, storms and floods can hit any area. Volcanic eruption can be potential risk in areas near volcanic activity.

• But people need to learn to live with natural disasters. Proper precautions can help save life and property; in case of natural disasters.

NCERT Solutions of Chapter 6 Major Landforms of the Earth

Extra Questions for Class 10th: Ch 9 Heredity and Evolution (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Define heredity.
Answer
Heredity deals with the inheritance of characters from one generation to the next.

Q2. How does the creation of variations in a species promote survival?
Answer
Variations increases the adaptability of an organism to its changing environmental conditions.

Q3. Name two human traits that show variations.
Answer
Colours of eyes and shape of external ears.

Q4. Which of the two sperm or egg–decides the sex of the child?
Answer
The sperm decides the sex of the child.

Q5. The forelimbs of frog, reptiles, birds and arms of man show the same basic design. What kind of organs are these?
Answer
Homologous organs.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. What is microevolutions?

Answer

Microevolutions is the evolution that takes place on a relatively small scale at the population level and can change the common characteristics of particular species.

Q2. What is speciation?

Answer

Speciation is the process of formation of a new species from the already existing species by accumulation of variations, natural selection, gene flow, genetic drift, etc.

Q3. How can we trace evolutionary relationships?

Answer

Evolutionary relationships can be traced by studying fossils, by studying homologous and analogous organs, by comparing the embryos of different animals and by comparing the DNA’s of different species.

Q4. What term did Mendel use for genes? Where are the genes located?

Answer

Mendel used the term ‘factors’ for genes. Genes are portions of DNA which code for a single protein.

Q5. How many pairs of chromosomes do human beings have, specify the types of chromosomes also?

Answer

Human beings have 23 pairs of chromosomes the first 22 pairs are called autosomes are similar in males and females. The 23rd pair is called the sex chromosome. In males it is XY and in females it is XX.

Short Answer Questions-II (SAQs-II): 3 Marks

Q1. What is the effect of DNA copying which is not perfectly accurate on the reproduction process?

Answer

If DNA copying is not perfectly accurate then the variations occurs among the species of same organisms.

Q2. Define variation in relation to a species: Why is variation beneficial is the species.

Answer

Variations are differences that occur between the organisms of the same species in spite of the same basic features.
Variation in species promotes survival of an organism in changing environment by increasing the adaptability.

Q3. ‘‘Variations that confer an advantage to an individual organism only will survive in population’’. Justify.

Answer

Variation is the difference in the characters or traits among the individuals of a species. Sexual reproduction of organisms produces variation. The variations produced in organisms during successive generations gets accumulated in the organism. The significance of variations shows up only if it continues to be inherited by the offspring for several generation.

Q4. What is speciation? How does it occur?

Answer

Formation of new species from the existing ones over the period of time is called speciation.
Speciation takes place due to gene flow, genetic drift, reproductive isolation and finally natural selection.

Long Answer Questions (LAQs): 5 Marks

Q1. How do we know how old fossils are?

Answer

We can find the relative of the fossil by the depth at which the fossil is found. The ones that are found near the surface are more recent than the fossils found in the deeper layer.
The second way of dating fossils in detecting the ratios of different isotopes of the same element in the fossils material.

Q2. (i) What is genetics?
(ii) Give the common name of the plant on which Mendel performed its experiments.
(iii) What for did Mendel use the term factors and what are these factors called now?
(iv) What are genes? Where are the genes located?

Answer

(i) Science which deals with the study of heredity and variations is called genetic.
(ii) Pea plant.
(iii) Mendel used the term factors for ‘genes’.
(iv) Genes is the unit of inheritance. It is a part of the chromosome which controls the appearance of a set of hereditary character. Genes are located on the chromosome.

NCERT Solutions of Chapter 9 Heredity and Evolution

Notes of Chapter 9 Heredity and Evolution

Extra Questions for Class 10th: Ch 10 Light - Reflection and Refraction (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. What is magnification of plane mirror?

Q2. When a convex lens will act as magnifying Glass?

When the object is kept on focal length of the convex lens, it is called magnifying glass.

Q3. Name the mirror

(a) Used by dentist

(b) Used for rear view mirror

(a) Concave mirror

(b) Convex mirror

Q4. The radius of curvature of a convex mirror is 20cm. What is its focal length?

Focal length =(radius of Curvature)/2

Focal length= 20cm/2 = 10cm

Q5. What is power of Lens of focal length of 20cm?

1/20cm = 1/0.2m=100/20= 5 Diopter.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively. If speed of light in glass is 2×10⁸ m/s, find the speed of light in water.

Refractive index of a medium = Speed of light in air/Speed of light in the medium
⇒ 3/2 = Speed of light in air/2×10⁸ m/s
Speed of light in air = 3×10⁸ m/s
Speed of light in water = (3×10⁸ m/s)/(4/3) = 2.25×10⁸ m/s

Q2. What is meant by power of a lens ? Write its SI unit.

The power of a lens is defined as the reciprocal of its focal length (I) expressed in meters. SI unit of power is diopter. One diopter is defined as the power of a lens whose focal length is 1 meter.

Q3. Draw the ray diagram of image formation in following Case? Write size, position and nature of image formed?

Image formed is virtual, erect and demised.

Q4. State two positions in which a concave mirror produces a magnified image of a given object List two difference between them.

Position	Between its pole and focus	Between the focus and center of curvature
Difference 1	The image is virtual and erect.	The image is real and inverted
Difference 2	Image is formed behind mirror.	The image is formed in front of mirror

Q1. The image of an object formed by a mirror is real, inverted and is of magnification -1. If the image is at a distance of 40 cm from the mirror, where is the object placed ? Where would the image be if the object is moved 20 cm towards the mirror? State reason and also draw ray diagram for the new position of the object to justify your answer.

The mirror is concave mirror. Since, magnification is -1, it means the size of image is equal to size of object. Also, by the formula of magnification,

M= -v/u = -1

⇒v=u

⇒ (Image distance)=(Object distance)=40cm

This is the case, when object is placed at center of curvature or twice the length of focal length.

So, twice the focal length is 40cm

Focal length= 40cm/2 = 20cm.

When object is placed at focal length, the image is formed at infinity.

Q2. A student wants to project the image of a candle flame on a screen 80 cm in front of a mirror by keeping the candle flame at a distance of 20 m from its pole. (i) Which type of mirror should the student use ? (ii) Find the magnification of the image produced. (iii) Find the distance between the object and its image.

(i) Concave Mirror

(ii) It is given, object distance u=-20m , Image distance v=-80m

Magnification is given as M=-v/u

M=-v/u= -(-80m/-20m) = 4

Distance between object and image v-u =-80m-(-20m)= 60m

Q3. (i) Name the spherical mirror used as : (a) Shaving mirror (b) Rear view mirror in vehicles (c) Reflector in search-lights. (ii) Write any three differences between a real and a virtual image.

Shaving mirror— Concave mirror

Rear view mirror — Convex mirror

Reflector in search-lights — Concave mirror .

Real image can be obtained on screen but virtual image cannot be obtained.

Reflected / Refracted rays actually meet where real image is formed while for virtual they only appear to meet. 'A Real image is always inverted while virtual image is always erect.

Q5. An object is kept at a distance of 18 cm, 20 cm, 22 cm and 30 cm, from a lens of power + 5D. (i) In which case or cases would you get a magnified image ? (ii) Which of the magnified image can we get on a screen ? (b) List two widely used applications of a convex lens.

Focal length = 1/power = 1/5D = 1/5m = 20cm

It is a convex lens of focal length 20cm.

So, magnified image will be formed in all cases, 20cm is focus, 18cm is on focal length, 22cm and 30cm is between focus and focus and center of curvature. In all cases, magnified image is formed.

(ii) In case of 22cm and 30cm image formed is real and hence can be obtained on screen.

Long Answer Questions (LAQs): 5 Marks

Q1. (a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum.

(b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is 2x10⁸ m/s, calculate the speed of light in : (i) vacuum, (ii) medium 'A'

Laws of Refraction

(i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.

(ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour and for the given pair of media. This law is also known as Snell’s law of refraction.

μ=sin⁡i/sin⁡r

Q2. A convex lens can form a magnified erect as well as magnified inverted image of an object placed in front of it". Draw ray diagram to justify this by statement stating the position of the object with respect to the lens in each case. An object of height 4 cm is placed at a distance of 20 cm from a concave lens of focal length 10 cm. Use lens formula to determine the position of the image formed.

Convex lens form magnified erect image when object is placed between optical center and F! of the lens.

Virtual erect same size of image is formed in this case.

Convex lens form magnified inverted image when object is placed at F1. Image formed is real, inverted and enlarged at infinity.

NCERT Solutions of Chapter 10 Light-Reflection and Refractiom

Notes of Chapter 10 Light-Reflection

Notes of Chapter 10 Light-Refraction

Notes of Chapter 7 Our Country - India Class 6th Geography

India: An Overview

• India is the seventh largest country in the world in terms of area.

• India is the second most populous country in the world.

• According to the 2011 census, the population of India is more than 1.2 billion.

Locational Setting of India

• India is located in the northern hemisphere.

• From south to north, the main land of India extends between 8°4' N and 37°6' N. From west to east, the main land of India extends between 68°7' E and 97°35' E.

Indian Standard Time

• The longitudinal extent of India is 29° which is huge. Hence, there could be wide differences in local timings.

• Due to great longitudinal extent, the sun rises about two hours earlier in Arunachal Pradesh than in Gujarat. To keep things simple, the local time has been fixed as per the longitude 82°30' E. This longitude is called the Standard Meridian of India.

India’s Neighbours

• Afghanistan and Pakistan are towards west of India. China, Nepal and Bhutan are towards north of India.

• Bangladesh and Myanmar are towards east of India.

• Sri Lanka and Maldives are towards south of India.
→ Sri Lanka is separated by India by the Pak Straits.

Political and Administrative Divisions

• India has been divided into 29 states.

• Rajasthan is the largest state and Goa is the smallest state.

• There are 7 union territories in India.

• All the states are further divided into smaller administrative units; called districts.

• Delhi is the National Capital of India.

Physical Divisions

• India is a diverse country; in terms of physical features. It can be divided into following physical divisions:
→ The Himalayan Mountains
→ The Northern Plains
→ The Great Indian Desert
→ The Deccan Plateau
→ Western Ghats and Eastern Ghats

The Himalayan Mountains

• The Himalayan Mountains are in the north of the Indian subcontinent.

• The Himalayan Mountains are divided into three parallel ranges, viz. the Great Himalaya or Himadri, the Middle Himalaya or Himachal and the Shivalik.

→ The Great Himalaya: This is the northernmost range. The highest peaks of the world are located in this range.

→ The Middle Himalaya: This range is towards south of the Great Himalayas. Many popular hill stations are in this range.

→ The Shivalik: This is the southernmost range. The elevation in this range is low compared to in the other two ranges.

The Northern Plains

• The Northern Plains lie to the south of the Himalayas.

• These plains are formed by the rivers; the Indus, the Ganges and the Brahmaputra and their tributaries.

• The lands are highly fertile in this region. Hence, this region has very high population density.

The Great Indian Desert

• The Great Indian Desert lies in the western part of India.

• This is a dry, hot and sandy stretch of land.

• There is very little vegetation in this region. This is also called the Thar Desert.

The Deccan Plateau

• The Deccan Plateau lies towards south of the Northern Plains.

• This is triangular in shape.

• There are many hill ranges and valleys in this region, e.g. Aravali hills, the Vindhyas and the Satpuras.

• The Deccan Plateau is rich in minerals.

• Narmada and Tapi are important rivers which flow through the Deccan Plateau. These rivers flow towards west and drain into the Arabian Sea.

• Western Ghats and Eastern Ghats

→ The Western Ghats mark the western boundary of the Deccan Plateau, while the Eastern Ghats mark the eastern boundary.

→ The Western Ghats are almost continuous but the Eastern Ghats are broken and uneven.

The Coastal Plains

• The Coastal Plains lie to the west of the Western Ghats and to the east of the Eastern Ghats.

• The western coastal plains are very narrow.

• The eastern coastal plains are much broader.

• The rivers Mahanadi, Godavari, Krishna and Kaveri flow in this region. These are east-flowing rivers and drain into the Bay of Bengal. These rivers have formed deltas at their mouth.

• These deltas are highly fertile.

• Delta is a landform which is formed at the mouth of a river.

• The place where a river meets an ocean is called the mouth of the river.

The Islands

• Lakshadweep Islands and the Andaman and Nicobar Islands are also part of India.

• The Lakshadweep Islands are in the Arabian Sea and are coral islands.
→ A coral island is formed by corals and other organic materials.

• The Andaman and Nicobar Islands are in the Bay of Bengal.

NCERT Solutions of Chapter 7 Our Country - India

Notes of Chapter 8 India - Climate, Vegetation and Wildlife Class 6th Geography

Weather

• The day to day changes in atmosphere is called weather.

• Weather includes changes in temperature, sunshine and rainfall.

Seasons in India

• There are four major seasons in India, viz. cold season, hot season, southwest monsoon and retreating monsoon.

→ Cold Weather Season or Winter Season: The winter season continues from December to February in India. During this season, the sun rays do not fall directly on India.

→ Hot Weather Season or Summer Season: The summer season continues from March to May in India. During this season, the sun rays fall more or less directly on India. Due to this, the temperature remains high during this period.

→ Southwest Monsoon Season or Rainy Season: The rainy season falls from June to September. The onset and advancement of monsoon takes place in this season.

→ Season of Retreating Monsoon or Autumn: This season falls in October and November. During this season, the monsoon winds move from the mainland to Bay of Bengal and hence it is called the retreating monsoon.

Climate

• Overall pattern of weather at a place is called climate.

• For this, weather pattern of at least 20 years is taken into consideration.

• The climate of India is called monsoon climate.

• This is hot and humid in most parts of the country.

Natural Vegetation

• Plants which grow on their own without human intervention are called natural vegetation.

• It depends on various climatic conditions and especially on rainfall.

• There are five types of natural vegetation in India.

→ Tropical Rain Forest: Tropical rainforest is found in those areas which receive heavy rainfall. The tropical rainforest is so dense that sunlight does not reach the ground. The trees of the tropical rainforest shed their leaves at different times of the year

→ Tropical Deciduous Forest: These are also called monsoon forests. The trees of deciduous forest shed their leaves at a particular time of the year. Hence, such a forest is called deciduous forest.

→ Thorny Bushes: This type of vegetation is found in dry areas. The leaves are in the form of spines. This helps the plant to reduce loss of water.

→ Mountain Vegetation: Different types of species are found in the mountains at different altitudes. At the height between 1500 meter and 2500 meter, most of the trees are conical in shape. Due to this, they are called coniferous trees.

→ Mangrove Forest: Mangrove plants can survive in saline water. They are mainly found in the Sunderbans in West Bengal and in the Andaman and Nicobar Islands. Sundari is a well known tree in the mangrove forest of Sunderban.

Importance of Forest

• Plants absorb carbon dioxide and release oxygen. Oxygen is utilized by us for breathing.

• Roots of plants bind the soil. Thus, plants prevent soil erosion.

• Forests provide us timber for furniture and firewood. They also provide fodder, medicinal plants and herbs. We also get lac, honey and gum from forests.

• Forests are the natural habitat of wildlife.

Loss of Natural Vegetation

• Humans have destroyed a large tract of forest by recklessly cutting trees for various purposes.

• Forests are cleared for making way for agriculture and for making townships and factories. This is creating environmental problems for us.

• Van Mahotsav is being organized to educate people about the importance of forests.

Wildlife

• Animals which live in natural vegetation are called wild animals. Thousands of animal species live in forests.

• Tiger is the national animal of India. It is found in various parts of our country.

• The Asiatic lions live in the Gir forest in Gujarat.

• Elephants are found in Kerala, Karnataka and Assam. Assam is also the home for one-horned rhino.

• Wild goats, snow leopards, bears, etc. are found in the Himalayan region.

• Peacock is out national bird.

• Parrots, pigeons, mynah, geese, bulbul and ducks are the other common birds.

• Due to large scale cutting of forests, natural habitat of many wild animals has become less. Many animals are in danger of becoming extinct. Many animals have already become extinct.

• Extinct Species: A species which no longer exists is called and extinct species.

• Endangered Species: A species which is in danger of becoming extinct is called endangered species.

NCERT Solutions of Chapter 8 India - Climate, Vegetation and Wildlife

Extra Questions for Class 10th: Ch 11 Human Eye and Colourful World (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. State one function of iris in human eye.

Answer
Function of iris: It controls the size of the pupil.

Q2. Name the part of the eye ?
(i)that controls the amount of light entering into the eye.
(ii) that had real, inverted image of the object formed on it.
Answer
(i) Pupil
(ii) Retina

Q3. What is meant by dispersion of light ?
Answer
The splitting of light into its component colours is called dispersion of light.

Q4. The sky appears dark instead of blue to an astronaut. State its reason.
Answer
The sky appears dark to the astronaut as scattering does not take place at very high attitude due to the absence of atmosphere.

Q5. What is the cause of dispersion of light on passing through a prism ?
Answer
The refractive index of the material of a prism is different for different colours of light as different colours have different speed in the material of a prism.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. What is the cause of dispersion of light on passing through a prism? Which coloured component bends the least during the dispersion of white light through prism ?

Answer

The refractive index of the material of a prism is different for different colours of light as different colours have different speed in the material of a prism. Also, prism has non-parallel surfaces.

Q2. Why does it takes some time to see objects in a cinema hall when we just enter the hall from bright sunlight ? Explain in brief.

Answer

(a) The pupil regulates and controls the amount of light entering the eye.
(b) In bright sunlight, the size of the pupil is small and when we enter the cinema hall it takes some time for the pupil to expand in size due to dim light.

Q3. How is a normal eye able to see distinctly distant as well as nearer objects ?

Answer

Eye lens is made up of fibrous material. Its curvature can be changed by ciliary muscles which changes its focal length.
When muscles are relaxed, the lens becomes thin and focal length increases and the eye is able to see distant objects.
Similarly, when ciliary muscles contract, focal length decreases and eye is able to see nearer objects.

Q4. An old person is unable to see clearly nearby object as well as distant objects :
(i) What defect of vision is he suffering from ?
(ii) What kind of lens will be required to see clearly the nearby as well as distant objects ? Give reason.

Answer

(i) Presbyopia.
(ii) He shall have to use both kinds of lenses. Convex lens for long sightedness and concave lens for short-sightedness.

Q5.(i) What is the least distance of distinct vision
(ii) How does the thickness of the eye lens change when we shift looking from a distant tree to reading a book ?

Answer

(i) It is the minimum distance to which, normal eye can see two similar object distinctly.
(ii) Eye lens will become thicker.

Short Answer Questions-I (SAQs-II): 3 Marks

Q11. Examine this diagram and answer the followed questions.

(a) Name the defect of vision the eye shown in diagram is going through.
(b) Name two reasons for the defect
(c) What type of lens is required to correct this defect of vision?

Answer

(a) Hypermetropia
(b) The reasons for this defect are
(i) The focal length of eye lens is increased
(ii) The eye balls become small
(c) A proper convex lens is required to correct this defect of vision.

Q12. (a) What do you mean by far point? What is far point of normal adult human eye?
(b) Name the defect of vision which result in alteration of far point.

Answer

(a) The maximum distance at which objects can be seen clearly is known as far point of eye. The far point for normal adult human eye is infinity.
(b) In refraction, we have studied about power of Lens. It is the inverse of focal length. The ability of the eye lens to adjust its focal length/power is called accommodation.

Q13. The near point of hypermetropic eye is 80 cm. What is the nature and power of the lens required to enable him to read a book placed at 25 cm from the eyes?

Answer

Given,
Near point of hypermetropic eye = 80cm
That means the image of an eye can be seen at 80cm.
Object is at 25cm, which is needed to be seen clear.
So, u =-25cm
So, corrective lens of focal length(f) is needed to show object at 80cm in front of eye.
By the lens formula,
Near point = 80 cm
Object distance u = – 25 cm
ν= – 80 cm (convex lens in case of hypermetropia)

So, the required focal length of lens is 36.36cm.

Q14. What do you mean by atmospheric refraction? When we see any object through the hot air over the fire, it appears to be wavy, moving slightly. Explain.

Answer

In a hot weather the air becomes hotter and rises above. The risen hot air is optically rarer than cold air which is optically denser. These there is difference in optical density (or refractive index) between different layers of air. The objects beyond the hot air appears to be wavy because the medium for light to pass through changes, the light passes from denser to rarer and then again to denser medium thereby causing refraction in the air. Moreover the refractive index of the hot air keeps changing which leads to give the wavy appearance of the object.

Long Answer Questions (LAQs): 5 Marks

Q1. What is Tyndall effect ? What is its cause? Explain two phenomena observed in daily life which are based on Tyndall effect.

Answer

Tyndall effect : When a beam of light is passed through a colloidal solution, placed in a dark room, the path of beam becomes illuminated when observed through a microscope placed perpendicular to the path of light. This effect is called Tyndall effect.

Cause of Tyndall effect: The size of the colloidal particle is relatively larger than the solute particle of a true solution. The colloidal particles first absorb energy from the incident light and then scatter a part of this energy from their surfaces. Thus, Tyndall effect is due to scattering of light by the colloidal particles and the colloidal particles are seen to be moving as points of light moving against a dark background.

Daily life Examples:
(i) When sunlight passes through a canopy of a dense forest, the tiny water droplets in the mist scatter light and become visible.
(ii) When a fine beam of sunlight enters a smoke filled room through a small hole, the smoke particles become visible due to the scattering of light.

Q2. (a) What is myopia? State the two causes of myopia and with the help of a labelled ray diagrams show:
(i) the eye defect myopia.
(ii) correction of myopia using a lens.
(b) Why is the normal eye unable to focus on an object placed within 10 cm from the eye?

Answer

(a) Myopia: Eye can see objects at short distance. Inability of the eye in viewing long distant objects. The image falls before retina.

Causes of Myopia:
(i) Elongation of eye ball.
(ii) Excessive curvature in cornea.
Correction of Myopia: By using concave lens (diverging lens), which shifts the image to the retina by diverging the rays further.

The above diagram represents myopia and its correction via concave lens.

(b) A normal eye is unable to clearly see the objects placed closer than 25 cm because the ciliary muscles of eyes are unable to contract beyond a certain limit.
If the object is placed at a distance less than 25 cm from the eye, then the object appears blurred and produces strain in the eyes.

NCERT Solutions of Chapter 11 Human Eye and Colourful World

Notes of Chapter 11 Human Eye and Colourful World

Notes of Chapter 1 What, Where, How and When Class 6th History

Where did people live?

• In India, the earliest people lived along the banks of the river Narmada for several hundred thousand years.

• They were skilled Gatherers and used to gather food.

• They had very vast knowledge of the plants growing around them. They also used to hunt animals for food.

• Sulaiman and Kirthar hills to the northwest of India in these areas where women and men first began to grow crops such as wheat and barley about 8000 years ago are located here. People also began rearing animals like sheep, goat, and cattle, and lived in villages.

• Garo hills to the north-east and the Vindhyas in central India. These were some of the other areas where agriculture developed. The places where rice was first grown are to the north of the Vindhyas.

• The river Indus and its tributaries (tributaries are smaller rivers that flow into a larger river). About 4700 years ago, some of the earliest cities flourished on the banks of these rivers.

• Later, about 2500 years ago, cities developed on the banks of the Ganga and its tributaries, and along the sea coasts.

• The Ganga and its tributary called the Son. In ancient times the area along these rivers to the south of the Ganga was known as Magadha now lying in the state of Bihar. Its rulers were very powerful, and set up a large kingdom.

• Travelling enriched the cultural traditions and sharing of ideas between people. People shared new ways of carving stones, composing music and cooking for several hundreds of years.

Names of the land

• The name India came from the river Indus (Sindhu in Sanskrit). 2500 years ago, the Iranians and the Greeks who came to India from the Northwest side called the river Indus as 'Hindos' or 'Indos'. And the land to the east of this river was called India.

• The name Bharata refers to a group of people who lived in North West part of India. They are also mentioned in Rig Veda some 3500 years ago. Later this name was use for the country.

Finding out about the past

• There are several ways of finding out about the past. One is to search for and read books that were written long ago. These are called manuscripts, because they were written by hand (this comes from the Latin word ‘manu’, meaning hand).

• These were usually written on palm leaf, or on the specially prepared bark of a tree known as the birch, which grows in the Himalayas.

• Many of these were written in Sanskrit, others were in Prakrit (languages used by ordinary people) and Tamil.

Inscriptions

• These are writings on relatively hard surfaces such as stone or metal. Sometimes, kings got their orders inscribed so that people could see, read and obey them.

• There are other kinds of inscriptions as well, where men and women (including kings and queens) recorded what they did. For example, kings often kept records of victories in battle.

• An archaeologist is a person who studies the people and what they did in the past by the things they left behind.

• They look for artifacts, which are the things made by the people and these artifacts reveal more about the past. They also carry on excavations (Digging the surface of the earth)

• Archaeologists also study bones of animals, birds and fish to find out the food habits of the people of past. They even study the plant remains, but the plant remains barely survive for so long.

• The evidences found by the Archaeologists are called Features.

What do dates mean?

• CE (Common Era) or AD Anno Domini, means in the year of Lord. BCE (Before Common Era) or BC-Before Christ.

• All the dates before the birth of the Christ are counted Backwards.

NCERT Solutions of Chapter 1 What, Where, How and When

Notes of Chapter 2 On the Trail of the Earliest People Class 6th History

The earliest people: why were they on the move?

Hunter-gatherers

• The name comes from the way in which they got their food.

• Generally, they hunted wild animals, caught fish and birds, gathered fruits, roots, nuts, seeds, leaves, stalks and eggs.

• The reasons why hunter-gatherers moved from place to place:-

→ They eaten up all the available plants and animals resources where they stay for the long time, for the search of food they have to move from place to place.

→ Some of the animals move from place to place in search for food that is why the hunters have to follow their movement.

→ Because of seasons change some of the plants and trees don’t bear fruits so people have to move place to place in search of different kinds of plants.

→ Plants, animals and people needs water, people need water during dry seasons that’s why they travelled on foot from place to place.

How do we know about these people?

• Archaeologists have found some of the things hunter-gatherers made and used. It is likely that people made and used tools of stone, wood and bone, of which stone tools have survived best.

Choosing a place to live in

• Many sites of hunter-gatherers were located near sources of water, such as rivers and lakes.

• Places where stone was found and where people made tools are known as factory sites.

• The blocks of stone, tools that were made and perhaps discarded because they were not perfect, and chips of waste stone left behind at these sites. Sometimes, people lived here for longer spells of time. These sites are called habitation-cum-factory sites.

• Making stone tools:

→ Stone on stone:- The tool which is made up of two stones in which one stone is act as hammer and other stone is used to strikes off flakes from the first, till the required shape was obtained.

→ Pressure flaking: The core was placed on a firm surface. The hammer stone was used on a piece of bone or stone that was placed on the core, to remove flakes that could be shaped into tools.

→ Kurnool caves: Traces of ash have been found here. They must have used the fire of many things like cooking, lightening the house and scaring the animals away.

• Around 12,000 years ago, there were major changes in the climate of the world, with a shift to relatively warm conditions. In many areas, this led to the development of grasslands.

• The caves in which these early people lived have paintings on the walls. Some of the best examples are from Madhya Pradesh and southern Uttar Pradesh. These paintings show wild animals, drawn with great accuracy and skill.

• There is no clear evidence but it is proposed that both men and women may have done their work together or they may be some tasks which were to be performed only by men or women alone. There may have been different practices in different parts of the sub-continent.

• Hunsgi: A number of early Palaeolithic sites were found here. At some sites, a large number of tools, used for all sorts of activities, were found. These were probably habitation-cum factory sites. In some of the other, smaller sites, there is evidence to suggest that tools were made. Some of the sites were close to springs. Most tools were made from limestone, which was locally available.

NCERT Solutions of Chapter 2 On the Trail of the Earliest People

Study Material and Notes of Ch 5 Working of Institutions Class 9th Civics

Need for Political Institutions

• The Prime Minister and the Cabinet are institutions that take all important policy decisions.

• The Civil Servants, working together, are responsible for taking steps to implement the ministers’ decisions.

• Supreme Court is an institution where disputes between citizens and the government are finally settled.

Parliament

• In democracies, an assembly of elected representatives exercises supreme political authority on behalf of the people.
→ In India such a national assembly of elected representatives is called Parliament.

Two Houses of Parliament

• In our country, the Parliament consists of two Houses. The two Houses are known as the Council of States (Rajya Sabha) and the House of the People (Lok Sabha).

• The total number of elected members of Lok Sabha is 543+2 Anglo Indian nominated members.
→ The total number of members of Rajya Sabha is 238+12 nominated members.

Executive

• At different levels of any government there are various functionaries who take day-to-day decisions and implement those decisions on behalf of the people.

→ All those functionaries are collectively known as the executive.

Political and Permanent Executive

• The one which is elected by the people for only a specific period of time is called the Political Executive.
→ It signifies the government of a country.

• The one where people are appointed on a long-term basis is called the Permanent Executive or the Civil Services.
→ People working for the civil services are called the civil servants.

Prime Minister

• Prime Minister is the most important political institution in the country.

Powers of the Prime minister

• He chairs Cabinet meetings.

• He coordinates the work of different Departments.

• His decisions are final in case disagreements arise between Departments.

• He exercises general supervision of different ministries. All ministers work under his leadership.

• The Prime Minister distributes and redistributes work to the ministers.

• He also has the power to dismiss ministers.

• When the Prime Minister quits, the entire ministry quits.

Council of Ministers

• Council of Ministers is the official name for the body that includes all the Ministers.

• It usually has 60 to 80 Ministers of different ranks.

Types of ministers

• Cabinet Ministers are usually top-level leaders of the ruling party or parties who are in charge of the major ministries.

• Ministers of State with independent charge are usually in-charge of smaller Ministries.

• Ministers of State or Deputy ministers are attached to and required to assist Cabinet Ministers in their work.

Coalition Government

• A government formed by an alliance of two or more political parties, usually when no single party enjoys majority support of the members in a legislature.

The President

• The President is elected by all the Members of Parliament (MPs) and Members of State Legislative Assemblies (MLAs).

Powers of the President

• The President supervises the overall functioning of all the political institutions in the country.

• All governmental activities take place in the name of the President.

• All laws and major policy decisions of the government are issued in her name.

• All major appointments such as the Chief Justice of India, the Judges of the Supreme Court and the High Courts, the Governors, the Election Commissioners, ambassadors to other countries are made in the name of the President.

• All international treaties and agreements are made in the name of the President.

• The President is the supreme commander of the defence forces of India.

• However, President exercises all these powers only on the advice of the Council of Ministers.

Judiciary

• All the courts at different levels in a country put together are called the judiciary.

• The Indian judiciary consists of a Supreme Court for the entire nation, High Courts in the states, District Courts and the courts at local level.

Independence of the judiciary

• Independence of the judiciary means that it is not under the control of the legislature or the executive.

NCERT Solutions of Chapter 5 Working of Institutions

Extra Questions for Class 9th: Ch 5 Working of Institutions Social Studies (S.St) Important Questions Answer Included

Very Short Answer Questions (VSAQs):

1. Name the three institutions that play a key role in major decisions in India.
Answer

In India, three institutions play a key role in major decisions that are the legislature, executive and judiciary.

2. Who is the Head of the State and the highest formal authority in the country?
Answer

The President is the head of the state and is the highest formal authority in the country.

3. Write one recommendation of Mandal Commission.
Answer

27% of government jobs be reserved for the socially and economically backward classes.

4. What is meant by coalition government?
Answer

A government formed by an alliance of two or more political parties when no single party enjoys majority support is known as coalition government.

5. How many members are nominated by the President in Rajya Sabha?
Answer

12 members.

6. When does a bill become a law?
Answer

A bill passed by the Parliament becomes a law only after the President’s assent.

7. Write one function of the Parliament.
Answer

Parliament makes new laws, changes the existing laws.

Short Answer Questions (SAQs):

1. “The Indira Sawhney and others vs Union of India Case”, was filed in which concern? Describe it.

Answer

The Second Backward Classes Commission in India was established in 1979 by the Janata Party Government under the then Prime Minister Morarji Desai. It was headed by Indian Parliamentarian B.P. Mandal. Hence, it was popularly known as the Mandal Commission.

• The Commission was asked to determine the criteria to identify the socially and educationally backward classes in India and recommend steps for their advancement.

• The Commission gave its report in 1980 and made many recommendations. One of these was that 27% of government jobs be reserved for the socially and economically backward classes (SEBC). The reservation issue was very strongly protested after the implementation of the Commission Report in 1990. People reacted vehemently because this decision affected thousands of job opportunities.

• Some people felt that reservations were necessary to balance the inequality among people of different castes in India. Others felt that reservations were unfair and would deny equal opportunities to those who did not belong to backward communities.

• Following the nation-wide outrage against the order and protest, a court case was filed against the order. These cases were grouped together by the supreme court and called the ‘Indira Sawhney and others Versus the Union of India Case’.

2. Why are political institutions important? Give any three points.

Answer

• Institution makes rules and regulations.

• It provides an opportunity for a wider set of people to be consulted in any decision.

• It implements decisions, if a dispute arises there should be someone to determine what is wrong and what is right.

3. Define the Parliament and the Legislature of India and write any one important role of it.

Answer

In India, a national assembly of elected representatives who exercises supreme political authority on behalf of the people is called the Parliament. At the state level, this is called Legislature or Legislative Assembly. One important role: The Parliament is the final authority for making laws in our country.

4. Describe the role played by the contemporary Prime Minister of India in the implementation of the Mandal Commission Report.

Answer

• The Prime Minister informed the Parliament about the decision through a statement in both the Houses of Parliament.

• The decision of the cabinet was sent to the department of personnel and training.

• The senior officers of the department drafted an order in line with the cabinet decision and took the minister’s approval.

5. “The Lok Sabha controls the Council of Ministers.” Justify this statement.

Answer

• Only a person who enjoys the support of the majority of the members in the Lok Sabha is appointed as the Prime Minister.

• If the majority of the Lok Sabha members say they have “no confidence” in the Council of Ministers, then all the ministers including the Prime Minister have to quit.

Long Answer Questions (LAQs):

1. What is meant by independence of the judiciary? Explain.

Answer

Independence of the judiciary:
• Judiciary is not under the control of the legislature or the executive.
• The judges do not act on the direction of the government or according to the wishes of the party in power.
• The Constitution of India provides the security to service of the judges. Once appointed by the President, their service cannot be terminated by will or by any authority whatever.
• There is a security of pay and allowances of the judges. Their salaries cannot be reduced
• The Supreme Court and the High Courts are free to decide their own procedure of work and establishment.
• Judge is not allowed to practice after retirement so that they cannot influence judgements of the court.

2. Which house of the Parliament is more powerful in India and why? Give any three reasons to justify your answer.
OR
In which three ways is the Lok Sabha more powerful than the Rajya Sabha Election Procedure of the two Houses of Parliament?

Answer

• The Lok Sabha is directly elected by the people and enjoys real power on behalf of the people.
• The Rajya Sabha is elected indirectly and mainly looks after the interest of the regions or federal units.
The Lok Sabha enjoys supreme powers:
• If there is a joint session of the two houses than the will of the Lok Sabha prevails due to its numerical supremacy.
• In money matters, the Lok Sabha is supreme as the Rajya Sabha can only delay a money bill for 14 days or give suggestions.
• The Lok Sabha controls the Council of Ministers through ‘no-confidence motion’.

3. Describe how the Prime Minister and the Council of Ministers are appointed.

Answer

• The President appoints the leader of the majority party or the coalition of parties that commands a majority in the Lok Sabha, as Prime Minister.
• In case no single party or alliance gets a majority, the President appoints the person most likely to secure a majority support.
• The President appoints other ministers on the advice of the Prime Minister.
• The Ministers are usually from the party or the coalition that has the majority in the Lok Sabha.
• The Prime Minister is free to choose ministers as they are members of Parliament. A person who is not a member of Parliament can also become a minister, but he has to get elected to one of the Houses of Parliament within six months of appointment as minister.

High Order Thinking Skills (HOTS):

1. Differentiate between political executive and permanent executive. Which executive is more powerful?

Answer

Political executive:

• It is elected by the people for a specified period.

• Political executive is more powerful than permanent executive.

• The ministers of political executives are elected by the people, so they are answerable to the people for their work. That’s why, the ministers take all the final decisions.

Permanent executive:

• In the second category, people are appointed on a long-term basis, who are called permanent executives.

• Officials working in civil services are called civil servants. They are also called bureaucrats.

• They remain in office even when the ruling party changes. These officers work under political executive and assist them in carrying out day to day administration. Permanent executive is more powerful.

NCERT Solutions of Chapter 5 Working of Institutions

Notes of Chapter 5 Working of Institutions

Extra Questions for Class 10th: Ch 12 Electricity (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. What will happen if switch of a particular bulb among three bulbs connected in series is switched off?

Answer

No current will flow

Q2. How voltmeter should be connected to a resistor in order to find potential difference across it.?

Answer

It is connected parellel to resistor.

Q3. Why resistivity is also known as specific resistance?

Answer

Resistivity is the resistance of a material at specific condition, unit length and unit cross section.

Q4. On what principle is an electric bulb based?

Answer

Heating effect of current.

Q5. Why are coils of electric toasters and electric irons made of alloy rather than pure metals?

Answer

Alloys are preferred to make coils of toasters and irons because they have higher resistivity and do not oxidise easily at high temperature.

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. An ammeter is always connected in series across a circuit element. What happens when it is connected in parallel with a circuit element?

Answer

An ammeter is a low-resistance device. When it is connected in parallel, the resistance of the circuit reduces considerably. Therefore, a large current flows through the circuit, by virtue of circuit element may damage.

Q.2 Which is analogous to temperature : a current or electric potential?

Answer

Electric potential is analogous to temperature. As heat flows from higher temperature to lower temperature, so charges flow from higher potential to lower potential.

Q3. Out of the two wires given, which one is having higher resistance? Given both wire is made up of same material and temperature is constant? Both are having circular cross section whose radius is given.

Answer

Since, both wires are having same material, their resistivity is same at same temperature. It is given as ρ(Let).

Q4. 320J of heat is produced in 10s in a 2Ω resistor. Find amount of current flowing through the resistor?

Answer

Given,

Heat produced H=320J

Time taken t=10s

Resistance of resistor R=2Ω

Current I (let)

Since, H=I² Rt

I²=H/Rt=320J/(2×10s)=(16A)²

I=4A

So, 4A of current is flowing through the resistor.

Q5. Write the factors, the resistance of a wire depends upon.

Answer

The factors are

(i)Temperature: Resistance increases with increase in temperature and vice versa.

(ii) Length of conductor: Resistance increase with increase in temperature and vice versa.

(iii)Cross sectional Area: Resistance decreases with increase in cross sectional Area and vice versa.

Short Answer Questions-I (SAQs-II): 3 Marks

Q10. The resistance of a wire of 0.01 cm radius is 10Ω. If the resistivity of the material of the wire is 50 x10⁸ ohm meter, find the length of the wire.

Answer

Q 1. Derive an expression for electric energy consumed in a device in terms of I,t, and R, where I is the , I is the current drawn in resistance R and t is the time for which the current flows ?

Answer

We know that work done = W = QV

V is potential difference, Q is charge passed.

V=IR

Now, we know current I=Q/t

Q=It

In t times Q charge has been passed.

W=It.IR

W=I²tR

So, electric energy consumed is given as

W=I²Rt

Q 2. Give reason for the following : Why are copper and aluminum wires used as connecting wires ? Why is tungsten used for filament of electric lamps? Why is lead-fin alloy used for fuse wires ?

Answer

These are good conductors of resistance low resistivity. Also, they are much cheaper than silver which is having highest conductivity.

They are having very high melting point and high resistivity.

It is having required melting point, so that it melts at required temperature.

Q 3. State the different ways, three resistors each having resistance r can be connected so that they will draw maximum current from the circuit. Explain

Answer

The three resistors will draw maximum current when are equivalent resistance will be minimum. This is the case when the resistors are connected in parallel with each other. In this case, the equivalent resistance will be R

Then,

1/R=1/r+1/r+1/r

1/R=3/r

R=r/3

In this case, maximum current will be drawn from the battery.

The minimum current will be drawn from the circuit, when resistance is maximum. This is the case, when resistances are connected in series.

The equivalent resistance of the system will be R’=r+r+r=3r

In this case, minimum current will be drawn from the battery.

Q 4. A metallic wire of resistance R is cut into ten parts of equal length. Two pieces each are joined in series and then five such combinations are joined in parallel. What will be the effective resistance of the combination?

Answer

The resistance of a conductor is directly proportional to the length of the conductor. The resistance of each piece of wire, when it is cut into ten parts of equal length, r=R/10, as we know resistance is directly proportional to the length of wire.

Two such pieces are when joined in series, the equivalent resistance of two part will be r+r=R/10+R/10=R/5

5 such elements are connected in parallel. Therefore, total resistance R’ will be equivalent resistance of all resisitors.

1/R' =5/R+5/R+5/R+5/R+5/R=5×5/R=25/R

R'=R/25

Long Answer Questions (LAQs): 5 Marks

Q1. When we say the resistors are in parallel? Write the expression for the resistors in parallel. How many 176 Ω resistors (in parallel) are required to carry 5 A on a 220 V line?

Answer

When we can say that resistors are in parallel if same potential difference is applied across them.

For three resistors, if we connect them in parallel, the equivalent resistance is R

1/R=1/R₁+1/R₂+1/R₃

For x number of resistors of resistance 176Ω, the equivalent resistance of the resistors connected in parallel is given by Ohm's law as V=IR

R = V/I

where,
supply voltage, V = 220 V

Current, I = 5 A

Equivalent resistance of the combination = R,
Given as,

Q2. Two wires X and Y are of equal length and have equal resistances. If the resistivity of X is more than that of Y, which wire is thicker and why ? For the electric circuit given below calculate

Answer

Current in each resistor

Total current drawn from battery

Let length of each resistor be l, let resistivity of wire X be ρ_x, and resistivity of wire Y be ρ_y.

Let cross sectional Area of X be A_xand of Y is A_Y.

ρ_x>ρ_y

But resistance of each wire X and Y be

R_x=R_y

ρ_x l/A_x=ρy l/Ay.

ρ_x.A_y=ρ_y.A_x

Since,

ρ_x>ρ_y

Therefore, A_x>A_y

Hence, the cross sectional area of wire X is more than cross sectional area of wire Y.

Since, all three resistors are in parallel, current through each resistor, is potential difference applied, divided by the resistance of each resistor.

Current through 3Ω

6V/3Ω=2A

Current through 10Ω

6V/10Ω=0.6A

Current through 5Ω

6V/5Ω=1.2A

Total current is current drawn by the circuit is the sum of all three currents

2A+0.6A+1.2A=3.8A

NCERT Solutions of Chapter 12 Electricity

Notes of Chapter 12 Electricity

Study Material and Notes of Ch 6 Democratic Rights Class 9th Civics

What are Rights?

• Rights are reasonable claims of persons recognised by society and sanctioned by law.

Case Study where rights are denied

Prison in Guantanamo Bay

• About 600 people were secretly picked up by the US forces from all over the world.

• They were put in a prison in Guantanamo Bay, an area near Cuba controlled by American Navy.

• They were linked to the attack on New York on 11 September 2001.

• The US army arrested them, interrogated them and decided whether to keep them there or not.

• There was no trial before any magistrate in the US.

• Amnesty International, reported that the prisoners were being tortured in ways that violated the US laws.

• The UN Secretary General said the prison in Guantanamo Bay should be closed down but the US government refused to accept these pleas.

Why do we need rights in a democracy?

• For democratic elections to take place it is necessary that citizens should have the right to express their opinion, form political parties and take part in political activities.

• Rights are guarantees which can be used when things go wrong.

• The government should protect the citizens’ rights.

• In most democracies, the basic rights of the citizen are written down in the constitution.

Rights in the Indian Constitution

• Indian Constitution provides for six Fundamental Rights.

Right to Equality

• According to constitution, the laws apply in the same manner to all, regardless of a person’s status. This is called the rule of law.

• The government shall not discriminate against any citizen on grounds only of religion, race, caste, sex or place of birth.

Right to Freedom

• Freedom means absence of interference in our affairs by others – be it other individuals or the government.

Indian Constitution gives all citizens the right to:

→ Freedom of speech and expression

→ Assembly in a peaceful manner

→ Form associations and unions

→ Move freely throughout the country

→ Reside in any part of the country

→ Practice any profession, or to carry on any occupation, trade or business.

→ No person can be deprived of his life or personal liberty except according to procedure established by law.

→ A government or police officer can arrest or detain any citizen unless he has proper legal justification.

Right against Exploitation

• The Constitution prohibits ‘traffic in human beings’.

• The Constitution also forbids forced labour or beggar in any form.

• The Constitution also prohibits child labour.

Right to Freedom of Religion

• India is a secular state which means it does not establish any one religion as official religion.

• Every person has a right to profess, practice and propagate the religion he or she believes in.

Cultural and Educational Rights

• The working of democracy gives power to the majority therefore it is the language, culture and religion of minorities that needs special protection.

• The Constitution specifies the cultural and educational rights of the minorities:

→ Any section of citizens with a distinct language or culture have a right to conserve it.

→ Admission to any educational institution maintained by government or receiving government aid cannot be denied to any citizen on the ground of religion or language.

• All minorities have the right to establish and administer educational institutions of their choice.

How can we secure these rights?

• The right to seek the enforcement of the fundamental rights is called the Right to Constitutional Remedies.

• This itself is a Fundamental Right which makes other rights effective.

Expanding scope of Rights

• Fundamental Rights are the source of all rights, our Constitution and law offers a wider range of rights.

• Over the years the scope of rights has expanded.

• Various other rights are:

→ Right to freedom of press

→ Right to information

→ Right to education

→ School Education

→ Right to information

→ Right to life

• Constitution provides many more rights, which may not be Fundamental Rights.

→ Right to property and Right to vote in elections are important constitutional rights.

NCERT Solutions of Chapter 6 Democratic Rights

Extra Questions of Chapter 6 Democratic Rights

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Notes of Ch 6 Democratic Rights| Class 9th Civics

Study Material and Notes of Ch 6 Democratic Rights Class 9th Civics