HISTORY OF THE EARTH

1) State and explain the hypothesis of the origin of solar system.
2) What is the estimated age of the earth? In which era did the human beings evolve?
3) On what basis scientists have said human beings and the earth did not come into existance at the same?
4) Differentiate between mesozoic era and cenozoic era.
5) What is era? Which era did the dinosaurs evolve? What is the time period of that era?
6) Write the major events that happened in Triassic, Jurassic and creataceous period?
7) Name the eras in which the following changes took place on earth?
(i) (Evolution of unicellular organism
(ii) (Evolution of human beings)
8) Write two features of palaeozoic era?
9) How is the information about ancient living beings taken?
10) In which era, were the following living beings originated?
(i) Dinosar)
(ii) (Man)
(ii) (Fish)
11) How was the evolution of living beings occured?

B. Questions Related to Fossils
1) What is fossil? What is its importance?
2) Give two conditions of fossils found in nature?
3) How is fossils formed? Explain.
4) Can all organisms be fossils? Give conditions for them to be fossils?
5) How do you identify the fossils?
6) Why do we study of fossils? Fossils are found only in sedimentary rock why?
7) What is carbon dating? What is the use of carbon dating?
8) What is external morphology?
9) How does the study of fossils helps in the evolution?
10) Name two substances where the fossils are preserved?

1) What is fossils fuel? Give example.
2) What is coal? How is coal formed? Explain.
3) Write down the importance of coal?
4) What is meneral oil?
5) Explain the formation of mineral oil?
6) What are the importance of mineral oil?
7) What is LPG? Write its importance?
8) Why is coal called fussel fuel?
9) What are the economic importance of coal?
10) In which rocks coal are found?
11) Where are the natural gases formed? Why is it called clean fuel?
12) What are the characteristics of good fuel?

MATERIALS USED IN DAILY LIFE

Cement
 Cement is a fine gray powder, which when mixed with water and materials such as sand, gravel,
pebble, etc., forms a paste which binds other together.

* For the manufacture of cement clay and calcium carbonate are taken in the ratio 1:2.These two are
then powdered and mixed with water to form a paste called slurry. The slurry is then put into a rotary
furnace called kiln and heated to 16000 0 C. After heating a mixture of calcium aluminate and calcium silicate is formed which is called cement clinker. Finally 1-2% gypsum is added & the mixture is grinded to form cement.

* Chemically cement is a mixture of calcium silicate and calcium aluminate

* During manufacture of cement when slurry is heated in the furnace, it changes into lump of chemical which is called cement clinker. By grinding the cement clinker with gypsum salt (1-2%) cement is made.

Uses of cement are
a. A mixture of cement, gravel, pebble and water is called concrete, which is used fior roofing
and flooring.
b. A thick paste of cement, sand and water is called mortar which is used for plastering walls
and to join bricks, stones etc.
c. Cement is used in the construction of buildings, roads, bridges etc.
d. Gypsum is added in the manufacture of cement to increase the setting time of cement. It makes
convenient to use the cement.

Artificial fibers
a.Man made fibers is called artificial fibers. They are of two types
o Recycled or Regenerated fibers
o Synthetic fibers
b. Rayon is an artificial silk made from cellulose of cotton and wood pulp. It is recycled fiber. Rayon is used in making fabrics, tyres cords, carpets, etc
c. Fibres made by chemical process are called synthetic fibers. Nylon, terylene, polyester, accryline,
olefin, etc are its examples.
d. Nylon is the first synthetic fiber because it is manufacture by polymerization of adipic acid and
hexamethyne-diamide.
e. Nylon fiber is widely used as
o In making socks, ropes, tyre cords, bristles for tooth brush, nets etc.
o In making fabrics in textiles.
f. Nylon fiber melts at low temperature , absorbs less water, therefore, quickly dry up when washed A polymer of ester molecule is Terylene fiber or polyester.
g. Terylene fibers are used in making fabrics, sails for boats, conveyor belt etc.
h. The common properties of synthetic fibers are
o They are fine, light, strong, durable and not eaten by insects.
o They absorb less water and therefore dry up quickly.

HERIDITY

Transformation of characters from parents into offspring is called heredity.

Variation
The dissimilarity between the individuals of the same species is called variation. The main causes of
variation are:

o Different organisms have different sets of chromosomes.
o Formation of gametes by meiosis cell division.
o Transformation of characters from father and mother both.
o Environmental influence or environmental cause.

Genetics
The branch of biology concerned with the study of the mechanism of heredity and variation is called
Genetics.Gregor Johann Mendel is called Father of Genetics.

Monohybrid cross
In a cross, the character which can express itself is called dominant character and that which is hidden by dominant character is called recessive character. For example, if a cross is made between pure tall and pure short pea plants (monohybrid cross), in F 1 generation all the pea plants are found tall. Here tall is dominant character and short is recessive character.

Genotype and Phenotype
External appearance of an organism is called phenotype and genetic make up of an organism is called
genotype of that organism. For example, a tall pea plant having trait. Tt has phenotype tall but genotype tall and short both.

Hybrid
Hybrid is that individual which has different phenotype and genotype. For example by pea plant having traits Tt is not pure tall but hybrid tall because its phenotype is tall but genotype is both tall and short.

Allele
A pair of genes controlling a pair of contrasting characters is known as an allelic pair and the members of an allelic pair are called allele of each other. For example, in Tt, T is allele of t and vice-versa.

Mendel selected a pea plant for his experiment because the following characters are found in a pea plant
(Pisum sativum)

o It is a naturally self pollinated and cross pollination also can be made artificially in it.
o It has a number of distinguishable contrasting characters.
o The hybrid plants obtained as a result of cross pollination are fertile.
o A large number of progeny can be obtained from a single plant.
o The life cycle is of short duration.
o The plants are convenient to handle.

Mendel’s Laws
Law of Dominance: This law states that “When a cross is made between a pure contrasting characters, only one of them is able to express itself phenotypically where others remains hidden in F 1 generation. The one, which is expressed, is dominant and the other is recessive.” For example, when a cross is made in between pure tall (TT) and pure short (tt) pea plants, in F 1 generation, all the pea plants are found tall (Tt).

Law of segregation / Law of purity of gametes:
This law stated that – “The two members of a pair of factors separate during the formation of gametes. They do not blend with each other but segregate out into different gametes.” For example, in Mendel’s experiment when selfing occurred in two monohybrid pea plants (Tt) if F 1 generation, in F 2 generation, the tall and short pea plants were found in the ration of 3 :1 (Phenotypic ration), while the genotypic ratio was 1:2:1.

Law of independent assortment:
This law states that “When two pairs of allele are brought together in the hybrid (F 1 ), they, at the time of gamete formation, segregate or assort independently at random and freely.”

FORCE

It is defined as a push or pull that changes or tends to change the state of rest or of uniform motion of
a body along a straight line.

Newton’s Universal law of gravitation
“Everybody in this universe attracts every another body with a force which is (i) directly
proportional to the product of their masses and (ii) inversely proportional to the square of the
distance between their centers”.

Consider a body of mass m 1 attracts another body of mass m 2 with a force F towards its centre O 1 .
The body of mass m 2 in turn attracts the body of mass m 1 with the same force F towards its centre
O 2 . Suppose the distance between their centers is‘d’ then, according to Newton’s universal law of
gravitation, we have

F∞m 1 .m 2 ………….(i)

And F∞1/d^2.………..(ii)
Combining these two equations (I) and (ii), we have

F∞Fm1m2/d^2

Or, F = GFm1m2/d^2 ………….(iii)
Where G is called a proportionally constant or universal gravitational constant. The value of The
G is determined form experiment.

Hence, the equation (iii) gives the measure of the gravitational force between two masses.
Universal gravitational constant ‘G’
Universal gravitational constant ‘G’ can be defined as the force of gravitation that is exerted between
two unit masses, separated from one another by a unit distance.
The SI unit of G is Nm 2/ kg -2 .
The approximate value of G is 6.6710 -11 Nm 2/kg -2 .

Properties of G
i. The value of G is independent of the nature and chemical composition of the masses of the
bodies, and the medium in which the bodies are occurred.
ii. The value of G is unaffected by temperature and pressure.

Consequences of gravitational force
i. The presence of solar system and planets revolve round the sun due to the presence of
gravitational force.
ii. The presence of atmosphere on the earth is due to the gravitational force.
iii. The gravitational force of the earth keeps us firmly on the surface of the earth.
iv. Tides in seas and oceans are due to the gravitational force of the sun and moon.

Special features of gravitational force
i. The gravitational forces between two bodies constitute on action and reaction pair.
ii. The gravitational force between two bodies does not depend upon the nature of the
intervening medium.
iii. The gravitational force between light bodies is extremely small and hence such smaller
force is not felt in practice. However, it becomes appreciable in case of massive bodies.

Gravity or weight
The force of attraction of the earth on a body is called force of gravity or simply the weight of the
body on earth.
Let a body of mass m be placed on the surface of the earth of mass M as shown in the figure. The
distance between them can be taken to be equal to the radius (R) of the earth. The weight (W) of the
body on the surface of the earth is given by,

W = GMm/R^2 …………….. (i) (
If m is kept constant,

W∞M/R^2 ……….. (ii)
Equation (ii) shows that weight (W) of a body on the surface of a planet/ satellite is directly
proportional to mass (M) of the planet /satellite. Greater the mass of the planet /satellite, larger its
gravity is i.e., greater will be the weight of the body on the planet/satellite.
Equation (ii) also shows that weight (W) of a body on the surface of a planet/satellite is inversely
proportional to the square of the radius (R) of the planet/satellite. The weight of the body will be less
if it becomes large.

Effects of gravity
1. We are able to stand up, run and perform other activities freely due to gravity of the earth.
2. Construction of building and bridges is possible due to the gravity of the earth.
3. There will be no atmosphere around the earth in the absence of gravity of the earth.
4. If a body is thrown upwards, its notion is opposed by gravity of the earth. So, it falls back
to the earth.
5. Tides occur by the gravity of the moon on ocean water.

ATMOSPHERE

The earth is surrounded by air. Air is also found in soil, water and porous things like sponges, bricks,
chalk, etc. Air makes a very thick layer around the earth called atmosphere. It is extended from the earth’s surface to the space. Atmosphere also contains smoke, dust particles and water vapour in it. According to the height of the atmosphere and its nature, temperature and components are found different. On the basis of height, components and nature, atmosphere is divided into the following five layers.
i. Troposphere
ii. Stratosphere
iii. Mesosphere
iv. Thermosphere
v. Exosphere
Troposphere
It is the lowest and the thinnest layer of the atmosphere. It is extended up to the height of 16km from
the earth’s surface. The layer has the maximum pressure. It contains clouds. Changes in this layer cause the change in weather. This layer is highly influenced by our activities. Rain, hail, dew, and snow come form this layer. As the height in this layer increases, the temperature decreases. Major components of this layer are: N 2 , O 2 , CO 2 water-vapor, dust, etc.

Stratosphere
Stratosphere is found above the troposphere. It is extended between the height of 16 to 50 km from
the earth’s surface. It contains less oxygen and more ozone. The layer of ozone is called ozonosphere, which is a protective layer for us. It protects us from the harmful effects of ultraviolet rays coming from the sun. In this layer the temperature increases, with the increment of height. Jet planes fly in this layer. This layer is also influenced in some extent by our activities.

Mesosphere
Mesosphere is the third layer of the atmosphere. It is extended between 50-80 km height from the
earth’s surface. This layer has very less ozone in it. This layer has very strong wind in it. The wind blows eastward in winter and westward in summer. In this layer the temperature decreases when the height increases.

Thermosphere
Exosphere is the outermost layer of the atmosphere. It is extended beyond 72 km height from the
earth’s surface. This layer is extended 9600 km. It is the outer limit of the atmosphere. It is the uppermost layer; therefore here is so less gravity that some atoms of its components escape into the space. The major components of it are hydrogen and helium atoms.

Atmosphere Review
i. Temperature decreases as the height increases by 6.5 0 c per km.
ii. Upper most part of the troposphere is called tropopause.
iii. Troposphere is responsible to determine the weather and climate (e.g. Raining, cloud, storming, fogs etc.)
iv. Temperature increases as the height increases in stratosphere.
v. The upper layer of stratosphere is called stratopouse.
vi. The region where the ozone (O 3 ) lies in the stratopause is called ozone layer.

Ozone Layer
i. The ozone layer absorbs about 99% ultraviolet radiation coming from the sun.
ii. Ozonosphere is about 35 km thick.
iii. Ozone is formed the following ways by radiation
O 2 --- O+O
O 2 + O ---- O 3 (Ozone)
iv. The reduction of ozone layer due to chloro fluoro carbon, methyl chloro form carbon tetra chloride and methyl bromide is called depletion of ozone layer.
Effects of depletion of ozone layer.
i. It causes skin burning, lung and breast cancer, leukemia, blindness
ii. Growth of aquatic and amphibian plants are affected.
iii. Loss of productivity of living beings
iv. The depletion of O 3 layer may bring about significant changes in climate and cause green house
effect.
v. The depletion of ozone layers causes eye cancer in cattles.

Protection of ozone layer
i. By banning the production and use of CFC.
ii. By bringing awareness of ozone depletion in people.
iii. By recapturing CFC released from the air conditioners, refrigerators and other machinery using
them.

Green House Effect
i. The house made up of green glasses which can trap the solar radiation in it is called a green house.
ii. Off season fruits and vegetables can be grown with the help of green house.
iii. Carbon dioxide, nitrous oxide, methane; CFC, water vapour protect the solar radiation to wards
the earth. That means these gases help the earth to act as a green house. So these gases are called
green house gases and when amount of these gases increased the temperature of the earth is also
increased. This increment in temperature is called green house effect.

Effects of green house effect
i. It increases the temperature of the atmosphere
ii. On human, it helps spreading diseases like malaria.
iii. It helps breeding, growth and spreading of insects.
iv. Reduces crop yields by reducing the soil moisture.
v. The changes in climate pattern changes the crop pattern.

Ways of controlling green house effect
i. By increasing forestation.
ii. By reducing the use of fossil fuels.
iii. By banning deforestation.
iv. By banning the use of CFC.
v. By using unleaded petrol in vehicles.
vi. By using biogas for domastic purposes.

Industrial gases
i. The gas like SO 2 , CO 2 , CO, NO 2 dust and smoke are produced by industries are called industrial gases.
ii. The increment in the amount of industrial gas in the atmosphere pollute the air. Which is called air
pollution.

Effects of air pollution
i. Produce diseases of neck, breast and longs.
ii. Leukemia
iii. Acid rain
iv. Raise in temperature)