Momentum notes of class 9

MOMENTUM, Chapter Notes, Class 9, Science

Created by: Suraj Gour

Forces and Laws of Motion

MOMENTUM

Momentum is the power of motion of an object.

The product of velocity and mass is called the momentum. Momentum is denoted by ‘p’.

Therefore, momentum of the object = Mass x Velocity.
Or, p = m x v

Where, p = momentum, m = mass of the object and v = velocity of the object.
Consider the following explanations to understand the momentum:
A person get injured in the case of hitting by a moving object, such as stone, pebbles or anything because of momentum of the object.

Even a small bullet is able to kill a person when it is fired from a gun becasue of its momentum due to great velocity.

A person get injured severely when hit by a moving vehicles, becasue of momentum of vehicle due to mass and velocity.

MOMENTUM AND MASS AND VELOCITY:

Since, momentum is the product of mass and velocity (p = m x v) of an object. This means momentum is directly proportional to mass and velocity. Momentum increases with increase of either mass or velocity of an object.

This means if a lighter and a heavier object is moving with same velocity, then heavier object will have more momentum than lighter one.
If a small object is moving with great velocity, it has tremendous momentum. And because of momentum, it can harm an object more severely. For example a small bullet having a little mass even kills a person when it is fired from a gun.

Usually, road accidents prove more fatal because of high speed than in slower speed. This happens because vehicles running with high speed have greater momentum compare to a vehicle running with slower speed.

MOMENTUM OF AN WHICH IS IN THE STATE OF REST:

Let an object with mass 'm' is in the rest.

Since, object is in rest, therefore, it's velocity, v = 0
Now, we know that,
Momentum = mass x velocity
Or, p = m x 0 = 0
Thus, the momentum of an object in the rest, i.e. non-moving,is equal to zero.
Unit of momentum:
The SI unit of mass = kg
The SI unit of velocity = meter per second i.e. m/s

We know that, momentum (p) = m x v
Therefore,
p = kg x m/s
Or, p = kg m/s
Therefore, SI unit of momentum = kg m/s.

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Sources of energy

Classification of Sources of Energy, Fossil Fuels, Hydro and Wind Energy, Class 10, Science
Sources Of Energy

Good Sources of Energy

A good source of energy would be one :
1. Which would do a large amount of work per unit volume or mass.
2. Be easily accessible
3. Be easy to store and transport.
4. The source of energy has to be economical.
Classification of Sources of Energy

We can classify energy sources in different ways. One classification is based on the reserves (supply) of an energy source. Another is based on how long we have been using it.

Renewable and nonrenewable sources of energy
Renewable sources of energy are those which can be generated by us or which are constantly being generated by natural processes or whose supply is unlimited.

Nonrenewable sources of energy

are those which were produced in the past by natural processes, whose supply is limited and which we cannot generate ourselves .
Coal, natural gas and petroleum are nonrenewable sources of energy. Wood is a renewable source of energy although its supply is limited. But if we replant and use trees in a planned manner, we can be assured of a continuous supply of firewood. The sun, wind and flowing water are also renewable sources because of their unlimited availability. Unlike fuels like coal, nuclear fuels such as uranium are required in very small quantities to generate electricity. So, their reserves will last for a long, long time. They are therefore classified as renewable sources of energy.

Conventional and nonconventional sources of energy

Sources of energy that have been in use for centuries are called conventional sources of energy. Conventional sources include wood, coal, petroleum and flowing water. Conventional sources like coal and petroleum are nonrenewable, while sources like flowing water are renewable.
Sources of energy that we have started using in new ways or only in recent times are called nonconventional or alternate sources of energy. These include energy from the sun, the heat inside the earth (geothermal energy), tides, ocean waves, etc. Nuclear energy is also a nonconventional source. Note that nonconventional energy sources are renewable.
We have been using wind and biomass (like cow dung) for energy for ages. In that sense they are conventionual sources. However, they were not used conventionally to do tasks like electricity generation, which has now been made possible with improvement in technology. In that sense they can also be called nonconventional sources of energy.

FOSSIL FUELS

Fuels that were formed from the remains of dead plants and animals are called fossil fuels. These were produced by complex processes with the help of a series of natural events over millions of years. The most widely used fossil fuels are coal, petroleum and natural gas. Plants trap solar energy in the form of food, and animals get energy when they eat the plants. Since fossil fuels came from plants and animals, their ultimate source of energy is the sun.

We get a number of different fuels from coal and petroleum. For example, we get petrol, diesel, kerosene and LPG from petroleum, and coke and natural gas from coal. When burnt in air, fossil fuels give off heat, which is used for various purposes-from cooking to generating electricity. However, these fuels are nonrenewable, and their reserves are running out. Unfortunately, we cannot repeat the events that led to their formation.
Fossil fuels have played an important role in the technological advances made in the last three hundred years or so. Even today, most of the energy requirements of homes, industries and transport are met by fossil fuels. It is estimated that about 25% of our total energy consumption comes from coal. More than 90% of this coal is used for electricity generation  in thermal power plants.

Summary of Chapter

We cannot imagine the world without energy. The source of energy is important as well. There are various sources of energy available today to the mankind. On a broad sense, sources of energy can be categorized into non-renewable and renewable. Wood, coal, oil, natural gas are some of the non-renewable sources as they cannot be renewable. These are also called the conventional sources of energy. Nuclear fuels like uranium produce energy by fission process. Nuclear energy from sun is obtained by nuclear fusion process.

Conventional fuels and sources of energy cause a lot of pollution to mankind and hence there is a need for looking towards alternate sources of energy, which are most likely to be renewable. Solar energy, energy from wind, hydro energy, geothermal energy and energy from biomass are some of the alternate sources of energy. Wind energy can be harnessed by using wind mills that can be erected at suitable locations. Hydroelectric plants make use of hydro energy. In most of the rural areas biomass is utilized.


Characteristics of a Good Source of Energy

       •  Enables us to do a large amount of work per unit volume or mass.
       •  Is easily accessible.
       •  Is easy to store and transport.
       •  Is economical.

Burning coal or petroleum products causes acidic oxides to be released. Thermoelectric production of electricity involves turbines. In thermal power stations, fossil fuels are burned to produce steam, basically a form of heat energy. This steam runs a turbine, which rotates a generator to produce electricity.

In hydroelectric power stations, the kinetic energy of flowing water, which is actually the potential energy of water stored at a height, is converted into electricity. Plant and animal products, wood and cow-dung cakes, are used as fuels. The source of these fuels is called bio-mass.

Burning a given mass of charcoal generates more heat than burning an equal mass of wood. Cow-dung, crop residue, garbage and sewage are decomposed in the absence of oxygen to produce bio-gas.

Advantages of Bio-Gas:
       •  It is an excellent fuel with 75% methane.
       •  It burns without smoke.
       •  It has a high heating capacity.
       •  It is also used for lighting.

Wind is another freely available resource that is used for generating energy.

Alternative or Non-Nonventional Sources of Energy:
       •  Energy from the sun
       •  Energy from the sea
       •  Geothermal energy
       •  Nuclear energy

Black surfaces absorb more heat when compared to white under identical conditions.

Three Types Energy From the Sea:
       •  Tidal energy
       •  Wave energy
       •  Ocean thermal energy

Molten rock in the earth’s crust is pushed upward and trapped in certain regions called hot spots.

Nuclear energy is produced either by nuclear fission or nuclear fusion. Exploiting various sources of energy causes disturbances in the environment.

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Magnetic effect of electric current

Magnetic Effect of Electric Current Class 10 Notes 

➣  Magnet: (i) is an object that attracts objects made of iron, cobalt & nickel. (ii)  Comes to rest in North-South direction, when suspended freely.

➣  Magnets are used: (i)  In radio & stereo speakers, (ii)  In refrigerator doors, (iii) on audio &
video cassettes players, (iv) On hard discs & floppies of computers & (v) in children‘s toys.

➣  Magnetic field:  The area around a magnet where a magnetic force is experienced is called a magnetic field. It is a quantity that has both direction & magnitude.

➣  Magnetic field lines: Magnetic field is represented by field lines. They are lines drawn in a Magnetic field along which a North magnetic pole moves.  Magnetic field lines are called as Magnetic lines of force.
Refer to figure 13.3 & 13.4 page no. 225 of N.C.E.R.T  Text book)
➣  Properties of Magnetic field lines:
(i)   They do not intersect each other.
(ii)   It is taken by convention that magnetic field lines emerge from North pole and merge at the South pole. Inside the magnet, their direction is from South pole to North pole. Therefore magnetic field lines are closed curves.

➣ Magnetic field lines due to a current through a straight conductor (wire)- consist of series of concentric circles whose direction is given by the Right hand thumb rule.

➣  Right hand thumb rule: If a current carrying straight conductor is held in your right hand such that the thumb points towards the direction of current, then the wrapped fingers show the direction of magnetic field lines.
(Refer to figure 13.7, page no. 228 of N.C.E.R.T  Text book)
➣ Magnetic field lines due to a current through a circular loop
(Refer to figure 13.8, page no. 228 of N.C.E.R.T  Text book)
➣  The strength of the magnetic field at he centre of the loop(coil)depends on:
(i)  The radius of the coil- The strength of the magnetic field is inversely proportional to the radius of the coil.  If the radius increases, the magnetic strength at the centre decreases.
(ii)  The number of turns in the coil: As the number of turns in the coil increase, the magnetic strength at the centre increases, because the current in each circular turn is having the same direction, thus the field due to each turn adds up.
(iii)  The strength of the current flowing in the coil:  as the strength of the current increases, the strength of thee magnetic fields also increases.v  Solenoid:
(Refer to figure 13.10, page no. 229 of N.C.E.R.T Text book)
➣ Solenoid (i) A coil of many turns of insulated copper wire wrapped in the shape of a cylinder is called a Solenoid.
(ii) Magnetic field produced by a Solenoid is similar to a bar magnet.
(iii)  The strength of magnetic field is proportional to the number of turns & magnitude of current.
➣ Electromagnet: An electromagnet consists of a long coil of insulated copper wire wrapped on a soft iron core.
(Refer to figure 13.11, page no. 229 of N.C.E.R.T Text book)

➣  Fleming‘s Left hand rule: Stretch the thumb, forefinger and middle finger of left hand such that they are mutually perpendicular. Forefinger points in the direction of magnetic field and centre finger in the direction of current, then the thumb gives the direction of force acting on the conductor.
(Refer to figure13.13, page no. 231 13.13 of N.C.E.R.T Text book)
➣  Electric motor:   A device that converts electric energy to mechanical energy. (Refer to figure 13.15, page no. 232 of N.C.E.R.T Text book)
➣  Principle of Electric motor: When a rectangular coil is placed in a magnetic field and a current is passed through it, force acts on the coil, which rotates it continuously.  With the rotation of the coil, the shaft attached to it also rotates.
➣  Electromagnetic induction:  Electricity production as a result of magnetism (induced current) is called Electromagnetic induction.
➣    Fleming‘s Right hand rule: gives the direction of induced current.Stretch the thumb, forefinger and middle finger of right hand such that they are mutually perpendicular. Forefinger points in the direction of magnetic field and centre finger in the direction of induced current, then the thumb gives the direction of motion of the conductor.

➣  Electric generator: A devise that converts mechanical energy to electric energy.
(Refer to figure 13.19, page no. 236 of N.C.E.R.T Text book)
Electric generator is of two types- (i) A.C generator (ii) D. C generator
➣  Principle of Electric generator:  Electromagnetic induction
➣  Domestic electric circuits:
(Refer to figure 13.20, page 238 of N.C.E.R.T Text book)
➣  We receive electric supply through mains supported through the poles or cables. In our houses we receive AC electric power of 220V with a frequency of 50Hz. The 3 wires are as follows-
(i) Live wire- (Red insulated, Positive)
(ii)  Neutral wire- (Black insulated, Negative)
(iii) Earth wire- (Green insulated) for safety measure to ensure that any leakage of current to a metallic body does not give any serious shock to a user.
➣  Short circuit: is caused by touching of live wires and neutral wire
➣  Fuse: is a protective device used for protecting the circuits from short circuiting and over loading.

➣  Important diagrams-

1.   Magnetic field lines around a bar magnet.
2.   Right hand thumb rule
3.   Magnetic field lines through and around a current carrying solenoid.
4.   An electromagnet.
5.   A simple electric motor
6.   Electric generator

➣  Important activities-

1.   Magnetic field lines around a bar magnet
2.   Direction of electric current in a simple electric circuit.
3.   Direction of Magnetic field lines depends on the direction of electric current.

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Electricity class 10 th

Introduction to Electricity - Electricity, Class 10, Science
Electricity
The source of all electricity is charge. As charge is the basis of all electrical phenomena, we need to know the amount of charge on a body. It is measured in coulombs. The coulomb is the SI unit of charge and its symbol is C.
Matter is generally made of protons, electrons and neutrons. Each proton carries a charge of
1.6 × 10-19 coulomb, and each electron carries an equal negative charge. Neutrons do not carry any net charge. Normally, a body has equal number of protons and electrons, and is therefore, electrically neutral. In certain situations, the balance of charges in a body is disturbed. For example, when a glass rod is rubbed with a silk cloth, some electrons get transferred from the glass rod to the silk. The silk cloth, which gains electrons, becomes negatively charged. And the glass rod, which is left with more protons than electrons, becomes positively charged.
Charged particles or objects can exert forces on each other. While like (similar) charges repel each other, unlike charges attract. Another important thing about charged particles is that they can flow, i.e., they can move in a particular direction. This flow of charged particles is called an electric current. Charged particles such as electrons are present in all substances. But they do not flow on their own. For flow of charges, there has to be a potential difference.
POTENTIAL DIFFERENCE AND THE FLOW OF CHARGE

The potential difference between two points A and B is the work done per unit charge in taking a charge from B to A. We express this mathematically as

Here, V is the potential difference between the points A and B, and VA and VB are the potentials at these points. The potential at infinity is chosen as zero.
If B be the reference point, the potential at B is VB = O. From Equation, the potential at A is
VA = W/q. So, the potential at a point is the work done per unit charge in taking a charge to that point from a chosen reference point. Equation may also be written as
W= qV.
The work done on the charge q is stored as the electric potential energy (U) of the group of charges. So,
U = qV
Unit of potential difference
The unit of potential difference (and potential) is the volt, whose symbol is V. One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.

The potential difference between two points is sometimes also called the voltage.
Flow of Charge
Consider two identical metallic spheres P and N, carrying equal amounts of positive and negative charges respectively. A positive charge is to be taken from B to A. It is attracted by the negatively charged sphere N and repelled by the positively charged sphere P. So, to move the charge towards A, one has to apply a force on it towards the left. Thus, the work done is positive. Hence, the potential difference VA - VB is positive. This means VA > VB'
As one moves towards P, the work done increases; so, the potential increases. And on moving towards N, the potential decreases. So, the potential of P is higher than that of N. In general, the potential of a positively charged body is taken as higher than that of a negatively charged body



What happens when a free-to-move charge is placed between the spheres? A positive charge will move towards the negatively charged sphere. And a negative charge will move towards the positively charged sphere. That is, a free positive charge moves towards lower potential. And a free negative charge moves towards higher potential.
If the two spheres are connected by a metal wire, electrons from the negatively charged sphere (at a lower potential) will flow to the positively charged sphere (at a higher potential). Eventually, the flow of electrons causes the charges on the spheres to become balanced. When that happens, the spheres no longer carry a net charge, and therefore, have equal potential. So, the flow of electrons stops. So we can say that a potential difference causes charges to flow.


A Cell Provides a Constant Potential Difference
The potential difference provided by things like charged spheres reduces to zero quickly once charges start to flow. So, we have to use cells to provide constant potential difference for a long time. Cells have chemicals inside. Reactions in the cell cause positive and negative charges to gather separately. This creates a potential difference between the terminals of the cell. The terminal at a higher potential is called the positive terminal and the one at a lower potential is called the negative terminal.
The cells that we commonly use are called dry cells (Figure). In a common dry cell, the small metallic cap at one end is the positive terminal, while the flat metallic plate at the other end is the negative terminal. It provides a potential difference of 1.5 V. A cell is represented by the symbol shown in fig (b). The larger line represents the positive terminal, while the shorter line represents the negative terminal.
A combination of cells is called a battery
Quite often, multiple cells are combined to get a potential difference that is higher than that of a single cell. For example, we connect two 1.5V cells to get a potential difference of 3V (Figure (c)) This is shown using symbols in Figure (d).
 

ELECTRIC CURRENT
Consider a metallic wire ACB connected across a cell of potential difference V. Since the end A is connected to the positive terminal, it is at a higher potential than the end B. In metals, some electrons are loosely bound to the atoms, and can move within it. These are called free electrons. In the metallic wire, these electrons (negative charges) move from the low-potential side B to the high-potential side A. After reaching A, they enter the cell. The chemical reactions in the cell drive these electrons to the negative terminal. From there, they re-enter the wire at the end B. Thus, there is a continuous flow of electrons in the wire from B to C to A. We say that there is an electric current in the wire. In a metal, the flow of negative charges constitutes the current.


An electric current can also be a flow of positive charges. So, a flow of charge is called an electric current.By convention, the direction of current is taken as the direction of flow of positive charges. Thus, the direction of current is opposite to the direction of flow of negative charges. So, when a wire is connected to a cell, the current in the wire is from the positive-terminal end to the negative-terminal end.

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Control and coordination

Study Material and Notes of Ch 7 Control and Coordination Class 10th Science

Topics in the Chapter

• Introduction
• System for control and coordination in animals
• Nervous System
→ Receptors
• Neuron
→ Functioning of Neuron
→ Parts of Neuron
→ Synapse
• Reflex Action
→ Types of Responses
→ Need for Reflex Action
• Human Nervous System
• Human Brain
→ For-Brain
→ Mid-Brain
→ Hind-Brain
→ Protection of Brain and Spinal Cord
→ Coordination between Nervous and Muscular Tissue
→ Limitation of Electric communication/Nervous System
→ Chemical combination
• Coordination in Plants
→ Independent of growth
→ Dependent of growth
• Plant Hormones
• Hormones in Animals
→ Endocrine gland and their functions
• Importance of iodine
• Diabetes
→ Cause of Diabetes
→ Treatment of Diabetes
→ Feedback Mechanism

Introduction

→ All the living organisms respond and react to changes in the environment around them.

→ The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch etc.
→ Both plants and animals respond to stimuli but in a different manner.

Systems for Control and Coordination in Animals

→ Control and Coordination in animals is done with the help of two main systems:
(i) Nervous system
(ii) Endocrine system

Nervous System

→ Control and coordination are provided by nervous and muscular tissues.

→ Nervous tissue is made up of an organized network of nerve cells or neurons which is specialized for conducting information via electrical impulses from one part of the body to another.

Receptors

→ These are specialized tips of some nerve cells that detect the information from the environment. `These are located in our sense organs.

(i) Ear: It acts as phonoreceptors (receiving sound). It helps in hearing and maintaining the balance of body.

(ii) Eyes: It acts as photoreceptors (receiving light). It helps in seeing

(iii) Skin: It acts as thermoreceptors (feels temperature). It helps in feeling heat or cold and touch.

(iv) Nose: It acts as olfactory receptors (sense of smell). It helps in the detection of the smell.

(v) Tongue:  It acts as Gustatory receptors (sense of test). It helps in the detection of taste.

Neuron

It is the structural and functional unit of nervous system.



Functioning of Neuron

→ The information from receptors is acquired at the end of the dendritic tip of a nerve cell as chemical reaction that creates an electrical impulse.

→ This impulse travels from the dendrite to the cell body and then at the end of the axon.

→ Chemicals are released at the end of the axon by the effect of electrical impulse.

→ These chemicals cross the gap (synapse) and start a similar electrical impulse in a dendrite of the next neuron.

→ The similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.


Parts of Neuron

(i) Dendrite: It acquires information.

(ii) Cell body: The information acquired by it travels as an electrical impulse.

(iii) Axon: It is the longest fibre on the cell body is called axon. It transmits electrical impulse from cell body to dendrite of next neuron.

Synapse: It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here, electrical signal is converted into chemical signal for onward transmission.

Reflex Action

→ Reflex action is quick, sudden and immediate response of the body to a stimulus.
Example: Knee jerk, withdrawal of hand on touching hot object.

→ Stimulus: It is observable or detectable change in the external or internal environment to which an organism reacts.

→ Reflex arc: The pathway through which nerve impulses pass during reflex action is called reflex arc.

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Notes of Ch 7 Control and Coordination| Class 10th Science



Study Material and Notes of Ch 7 Control and Coordination Class 10th Science

Topics in the Chapter

• Introduction
• System for control and coordination in animals
• Nervous System
→ Receptors
• Neuron
→ Functioning of Neuron
→ Parts of Neuron
→ Synapse
• Reflex Action
→ Types of Responses
→ Need for Reflex Action
• Human Nervous System
• Human Brain
→ For-Brain
→ Mid-Brain
→ Hind-Brain
→ Protection of Brain and Spinal Cord
→ Coordination between Nervous and Muscular Tissue
→ Limitation of Electric communication/Nervous System
→ Chemical combination
• Coordination in Plants
→ Independent of growth
→ Dependent of growth
• Plant Hormones
• Hormones in Animals
→ Endocrine gland and their functions
• Importance of iodine
• Diabetes
→ Cause of Diabetes
→ Treatment of Diabetes
→ Feedback Mechanism

Introduction

→ All the living organisms respond and react to changes in the environment around them.

→ The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch etc.
→ Both plants and animals respond to stimuli but in a different manner.

Systems for Control and Coordination in Animals

→ Control and Coordination in animals is done with the help of two main systems:
(i) Nervous system
(ii) Endocrine system

Nervous System

→ Control and coordination are provided by nervous and muscular tissues.

→ Nervous tissue is made up of an organized network of nerve cells or neurons which is specialized for conducting information via electrical impulses from one part of the body to another.

Receptors

→ These are specialized tips of some nerve cells that detect the information from the environment. `These are located in our sense organs.

(i) Ear: It acts as phonoreceptors (receiving sound). It helps in hearing and maintaining the balance of body.

(ii) Eyes: It acts as photoreceptors (receiving light). It helps in seeing

(iii) Skin: It acts as thermoreceptors (feels temperature). It helps in feeling heat or cold and touch.

(iv) Nose: It acts as olfactory receptors (sense of smell). It helps in the detection of the smell.

(v) Tongue:  It acts as Gustatory receptors (sense of test). It helps in the detection of taste.

Neuron

It is the structural and functional unit of nervous system.



Functioning of Neuron

→ The information from receptors is acquired at the end of the dendritic tip of a nerve cell as chemical reaction that creates an electrical impulse.

→ This impulse travels from the dendrite to the cell body and then at the end of the axon.

→ Chemicals are released at the end of the axon by the effect of electrical impulse.

→ These chemicals cross the gap (synapse) and start a similar electrical impulse in a dendrite of the next neuron.

→ The similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.


Parts of Neuron

(i) Dendrite: It acquires information.

(ii) Cell body: The information acquired by it travels as an electrical impulse.

(iii) Axon: It is the longest fibre on the cell body is called axon. It transmits electrical impulse from cell body to dendrite of next neuron.

Synapse: It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here, electrical signal is converted into chemical signal for onward transmission.

Reflex Action

→ Reflex action is quick, sudden and immediate response of the body to a stimulus.
Example: Knee jerk, withdrawal of hand on touching hot object.

→ Stimulus: It is observable or detectable change in the external or interDnal environment to which an organism reacts.

→ Reflex arc: The pathway through which nerve impulses pass during reflex action is called reflex arc.




→ Response: It is the final reaction after the reflex action.

Three types of responses:

(i) Voluntary: Controlled by fore brain. Example: talking, writing.

(ii) Involuntary: Controlled by mid and hind brain. Example: heart beat, vomiting, respiration.

(iii) Reflex action: Controlled by spinal cord. Example: withdrawal of hand on touching a hot object.

Need for Reflex Actions

→ In some situations such as touching a hot object, pinching etc. we need to act quickly, otherwise our body would be harmed. Here response is generated from spinal cord instead of brain. In this way, time for taking action is reduced which save us from injury.

Human Nervous System

→ Human nervous system consists of two parts, Central nervous system (CNS) and Peripheral nervous system (PNS).

→ Central nervous system consists of Brain and Spinal Cord.

→ Peripheral nervous system consists of Cranial Nerves which arise from the brain and Spinal Nerves which arise from the Spinal cord.

Human Brain

→  Brain is the main coordinating centre of the body. It has three major parts:

(i) Fore-brain
(ii) Mid-brain
(iii) Hind-brain



Fore-brain

→  It is the most complex or specialised part of the brain. It consists of cerebrum.

→  Functions of Fore-brain:

(i) Thinking part of the brain.
(ii) Control the voluntary actions.
(iii)Store information (Memory).
(iv) Receives sensory impulses from various parts of the body and integrate it.
(v) Centre associated with hunger.

Mid-brain

→ Controls involuntary actions such as change in pupil size and reflex movements of head, neck and trunk.

Hind-brain

It has three parts:

(i)  Cerebellum : Controls posture and balance. Precision of voluntary actions. Example: picking pen.

(ii) Medulla : Controls involuntary actions. Example: blood pressure, salivation, vomiting.

(iii) Pons : Involuntary actions, regulation of respiration.

Protection of Brain and Spinal Cord

→ Protection of Brain: Brain is protected by a fluid filled balloon which acts as shock absorber and is enclosed in cranium (skull or brain box).

→ Protection of Spinal Cord: Spinal cord is enclosed in vertebral column.

Coordination between Nervous and Muscular Tissue

→ For taking place the voluntary actions, the brain has to send messages to muscles.

→ The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.

→ The brain thus allows us to think and take actions based on that thinking. This is accomplished through a complex design, with different parts of the brain responsible for integrating different inputs and outputs.


Limitations of Electric communication/Nervous system

(i) Electric impulse will reach only to those cells that are connected by nervous tissue.

(ii) After generation and transmission of an electrical impulse, the cell takes some time to reset its mechanism before transmitting another impulse. So cells cannot continually create and transmit impulse.

(iii) Plants do not have any nervous system.

Chemical communication

→ It helps in overcoming the limitations of electric communication.

Coordination in Plants

→ There are three types of movements in plants.

(i) Independent of growth
(ii) Dependent on growth

Independent of growth

→ Independent growth has immediate response to the stimulus.

• Plants use electrical-chemical means to convey information from cell to cell.

• For movement to happen, cells change their shape by changing the amount of water in them, resulting in swelling or shrinking of cells.

Example: Drooping of leaves of ‘Touch-me-not’ plant on touching it.

Dependent on growth

→ These movements are tropic movements i.e., directional movements in response to stimulus.

• Tendrils: The part of tendril away from the object grows more rapidly as compared to the part near the object. This causes circulating of tendril around the object.

• Phototropism: Movement towards light.

• Geotropism: Movement towards/away from gravity.

• Chemotropism: Growth of pollen tube towards ovule.

• Hydrotropism : Movement towards water.

Plant Hormones

→ These are chemical compounds which help to coordinate growth, development and responses to the environment.

→ Main plant hormones are:

• Auxin:  This hormones synthesized at shoot tip. It helps the cells to grow longer and involved in phototropism (response towards light).

• Gibberellin : It helps in the growth of the stem.

• Cytokinins: It promotes cell division. This is present in greater concentration in fruits and seeds

• Abscisic Acid: It inhibits growth. It also cause wilting of leaves and also known as stress hormone.

Hormones in Animals

→ Hormones are the chemical substances which coordinate the activities of living organisms and also their growth.

• Endocrine glands : These glands secrete their product (hormone) into the blood and the main organ for releasing the hormones.

• The list of endocrine gland with the hormones names and their functions are given below:


(i) Thyroxine: This hormone is secreted by Thyroid. The Thyroid is located in Neck/Throat region. It regulates the metabolism of carbohydrates, fats and proteins.

(ii) Growth hormones: This is secreted by Pituitary (master gland). This gland is located in Mid-brain. It regulates growth and development.

(iii) Adrenaline: This hormone is secreted by Adrenal. The adrenal gland is located above both kidneys. It regulates blood pressure (increasing), heart beat, carbohydrate metabolism (during emergency).

(iv) Insulin: This hormone is secreted by Pancreas. The pancreas is located below stomach. It reduces and regulates blood sugar level.

(v) Sex hormones:
(a) Testosteron in males: This hormone is secreted by testis. The testis is located in genital area. Its changes associated with puberty (Sexual maturity).

(b) Estrogen in females: This hormone is secreted by Ovaries. The ovaries are located in lower abdomen area. Its changes associated with puberty (Sexual maturity).

Importance of iodine

Iodised salt is necessary because iodine mineral is essential part of thyroxine hormone secreted by thyroid gland. Thyroxine regulates metabolism of carbohydrates, fats and proteins. So, we must consume iodised salt which is necessary for proper working of thyroid gland. It’s deficiency causes a disease called goiter (Swollen neck).

Diabetes

Diabetes is a disease in which blood sugar level increases.

Cause of Diabetes

The disease is caused due to the deficiency of insulin hormone secreted by pancreas that is responsible to control blood sugar levels.

Treatment of Diabetes

Injections of insulin hormone can help in the treatment of diabetes.

Feedback Mechanism

→ The excess or deficiency of hormones has a harmful effect on our body. Feedback mechanism makes sure that hormones should be secreted in precise quantity and at right time.

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Notes of life process

Life Processes Class 10 Notes Biology
NCERT CBSE Chapter 6

➣  Life processes – The processes that are necessary for an organism to stay alive. Eg. Nutrition,respiration, etc.
➣ Criteria of life- (i) Growth  (ii) Movement
➣  Nutrition- The process in which an organism takes in food, utilizes it to get energy, for growth, repair and maintenance, etc. and excretes the waste materials from the body
 Types of nutrition
1.   Autotrophic nutrition (Auto =self:  trophos = nourishment) E.g. Plants, Algae, blue green bacteria.
o Process – Photosynthesis (Photo=light; Synthesis= to combine)
o Raw materials- (i) Carbon dioxide (ii)Water
o Equation-             

o Energy conversion- Light/Solar energy to Chemical energy
o Role off Chlorophyll- To trap the sun‘s energy for photosynthesis
o Factors for Autotrophic nutrition -
(i) Carbon dioxide
(ii) Water
(iii)  Light
(iv) Temperature
o Events/ Steps of photosynthesis-
(i)   Absorption of light energy by chlorophyll
(ii)  Conversion of light energy to chemical energy & Splitting of water molecule into Hydrogen & oxygen
(iii) Reduction of Carbon dioxide to Carbohydrate
o Gaseous exchange-
(i) Gas used- Carbon dioxide
(ii)  By product - Oxygen
o Source of raw materials-
(i)     Carbon dioxide –Land plants- Air, Aquatic plants- Water
(ii)  Water & Minerals - Soil
2.   Heterotrophic nutrition (Hetero =others:  trophos =ourishment) Eg. Animals, plants lacking chlorophyll like fungi.
(a) Saprophytic nutrition: Organisms feeds on dead decaying plants or animals material. E.g. Fungi, Bacteri
(b) Parasitic nutrition: Organisms obtain food from the body of another living (host)
o Endoparasite : Parasite lives inside the body of the host e.g. tapeworm, roundworm.
o Exoparasite :  Parasite lives on the body of the host. E.g. lice, leech.
Note- The parasite benefits while the host is usually harmed e.g. Cuscutta-plant parasite (amar bel), plasmodium (malarial parasite).
(c) Holozoic nutrition: Organism (mostly animals) take in whole food and then digest it into smaller particles with enzyme. Eg.Amoeba, Paramoecium. Animals, human beings.
o Steps in Holozoic nutrition
(i) Ingestion: taking in of food.
(ii) Digestion: breaking down of complex food into simpler, absorbable form.
(iii Assimilation: Utilization of digested food from the body.
(iv)Egestion: Removing undigested food from the body
o Nutrition in human beings
♦    Alimentary canal-
Mouth Oesophagus Stomach Small intestine Large intestine
♦    Important gland/juices
(Refer to figure 6.6 page no.97 of N.C.E.R.T  Text book)

Organ
Gland
Enzyme/Juice
Function
Mouth
Salivary
glands
Salivary Amylase
Converts starch into sugar
Stomach
Gastric glands
Gastric juice-
(i) Hydrochloric
acid             

(a) Kills harmful bacteria that enters with the food.

(b) Makes the medium alkaline for the action of Pepsin


(ii)  Pepsin       
Digests proteins




(iii) Mucus
Protects the inner lining of the stomach from the corrosive action of Hydrochloric acid.
Small
intestine
1) Liver



(i) Bile juice   



(a) Makes the medium acidic
for the action of Pancreatic enzymes.

(b) Breaks down large fat molecules into smaller globules so that enzymes can act upon them.


2)  Pancreas

( ii)  Pancreatic
Juice
♦ Amylase

Converts Carbohydrates to glucose


♦   Trypsin
Converts Proteins to Amino acids


♦    Lipase 
Converts Fats into Fatty acids & Glycerol


  Aerobic espiration

Anaerobic respiration



1.  Takes place in presence of Oxygen.
2.  End products- Carbon dioxide & Water
3. More energy is released.
4.  Takes place in Cytoplasm & Mitochondria
5. Complete oxidation of glucose takes place.
6. It occurs in most organisms.
7.  Equation-
Glucose→ Pyruvate→ CO2   + H2O + Energy
1.  Takes place in absence of Oxygen.
2. End products- Ethanol & Carbon dioxide
3. Less energy is released.
4.  Takes place in only in Cytoplasm.
5. Incomplete oxidation of glucose takes place.
6.  It occurs in certain bacteria, Life Processes Class 10 Notes Biology
NCERT CBSE Chapter 6 Download in Pdf

➣  Life processes – The processes that are necessary for an organism to stay alive. Eg. Nutrition,respiration, etc.
➣ Criteria of life- (i) Growth  (ii) Movement
➣  Nutrition- The process in which an organism takes in food, utilizes it to get energy, for growth, repair and maintenance, etc. and excretes the waste materials from the body
 Types of nutrition
1.   Autotrophic nutrition (Auto =self:  trophos = nourishment) E.g. Plants, Algae, blue green bacteria.
o Process – Photosynthesis (Photo=light; Synthesis= to combine)
o Raw materials- (i) Carbon dioxide (ii)Water
o Equation-             

o Energy conversion- Light/Solar energy to Chemical energy
o Role off Chlorophyll- To trap the sun‘s energy for photosynthesis
o Factors for Autotrophic nutrition -
(i) Carbon dioxide
(ii) Water
(iii)  Light
(iv) Temperature
o Events/ Steps of photosynthesis-
(i)   Absorption of light energy by chlorophyll
(ii)  Conversion of light energy to chemical energy & Splitting of water molecule into Hydrogen & oxygen
(iii) Reduction of Carbon dioxide to Carbohydrate
o Gaseous exchange-
(i) Gas used- Carbon dioxide
(ii)  By product - Oxygen
o Source of raw materials-
(i)     Carbon dioxide –Land plants- Air, Aquatic plants- Water
(ii)  Water & Minerals - Soil
2.   Heterotrophic nutrition (Hetero =others:  trophos =ourishment) Eg. Animals, plants lacking chlorophyll like fungi.
(a) Saprophytic nutrition: Organisms feeds on dead decaying plants or animals material. E.g. Fungi, Bacteri
(b) Parasitic nutrition: Organisms obtain food from the body of another living (host)
o Endoparasite : Parasite lives inside the body of the host e.g. tapeworm, roundworm.
o Exoparasite :  Parasite lives on the body of the host. E.g. lice, leech.
Note- The parasite benefits while the host is usually harmed e.g. Cuscutta-plant parasite (amar bel), plasmodium (malarial parasite).
(c) Holozoic nutrition: Organism (mostly animals) take in whole food and then digest it into smaller particles with enzyme. Eg.Amoeba, Paramoecium. Animals, human beings.
o Steps in Holozoic nutrition
(i) Ingestion: taking in of food.
(ii) Digestion: breaking down of complex food into simpler, absorbable form.
(iii Assimilation: Utilization of digested food from the body.
(iv)Egestion: Removing undigested food from the body
o Nutrition in human beings
♦    Alimentary canal-
Mouth Oesophagus Stomach Small intestine Large intestine
♦    Important gland/juices
(Refer to figure 6.6 page no.97 of N.C.E.R.T  Text book)

Organ
Gland
Enzyme/Juice
Function
Mouth
Salivary
glands
Salivary Amylase
Converts starch into sugar
Stomach
Gastric glands
Gastric juice-
(i) Hydrochloric
acid             

(a) Kills harmful bacteria that enters with the food.

(b) Makes the medium alkaline for the action of Pepsin


(ii)  Pepsin       
Digests proteins




(iii) Mucus
Protects the inner lining of the stomach from the corrosive action of Hydrochloric acid.
Small
intestine
1) Liver



(i) Bile juice   



(a) Makes the medium acidic
for the action of Pancreatic enzymes.

(b) Breaks down large fat molecules into smaller globules so that enzymes can act upon them.


2)  Pancreas

( ii)  Pancreatic
Juice
♦ Amylase

Converts Carbohydrates to glucose


♦   Trypsin
Converts Proteins to Amino acids


♦    Lipase 
Converts Fats into Fatty acids & Glycerol


  Aerobic espiration

Anaerobic respiration



1.  Takes place in presence of Oxygen.
2.  End products- Carbon dioxide & Water
3. More energy is released.
4.  Takes place in Cytoplasm & Mitochondria
5. Complete oxidation of glucose takes place.
6. It occurs in most organisms.
7.  Equation-
Glucose→ Pyruvate→ CO2   + H2O + Energy
1.  Takes place in absence of Oxygen.
2. End products- Ethanol & Carbon dioxide
3. Less energy is released.
4.  Takes place in only in Cytoplasm.
5. Incomplete oxidation of glucose takes place.
6.  It occurs in certain bacteria, yeast & certain tissues of higher organisms. E.g. In humans during vigorous exercise, when the demand for Oxygen is more than the supply, muscle cells respire anaerobically for some time.
7.  Equation- In Yeast-
Glucose→ Pyruvate→ Ethanol + H2O + Energy
In muscle cells - Glucose→ Pyruvate→ Lactic acid + Energy
o Some common features of Respiratory organs-
(i) Large surface area- for greater rate of diffusion of respiratory gases.
(ii)  Thin permeable walls – to ensure easy diffusion & exchange of gases.
(iii)  Extensive blood supply- Respiratory organs are richly supplied with blood vessels for quick transport of gases.
o Gaseous exchange in plants-

♦    Process – Diffusion
♦    Direction of diffusion depends on-
(i) Environmental conditions
(ii)  Requirement of the plant.
♦    Day time- Carbon dioxide given out during respiration is used for photosynthesis.Therefore only Oxygen is released, which is a major activity during the day.
♦    Night time – Only respiration takes place. Therefore only Carbon dioxide is released, which is a major activity during the night.
o  Gaseous exchange in animals-

♦    Terrestrial animals- take Oxygen from the atmosphere.
♦    Aquatic animals- take Oxygen dissolved in water. (Oxygen content is low in water, therefore they breathe faster.

o Human Respiratory system-
External nostrils → Nasal cavity → Trachea→ Bronchi → Bronchioles →Alveoli
♦   Rings of cartilage present in the throat ensure that the trachea (air passage) does not collapse when there is less air in it.
♦    Lungs –
(i) Present in the thoracic cavity.
(ii)  They are spongy, elastic bags consisting of Bronchi, Bronchioles and Alveoli

Refer to figure 6.9 page no. 104 of N.C.E.R.T  Text book)
o Respiration occurs in two phases-
o (i) External-Breathing, which is a mechanical process.
(ii) Internal - Cellular respiration
o Mechanism of breathing – It includes :
(i)Inhalation
(ii) Exhalation
o Exchange of gases-
♦    Unicellular organisms- By Diffusion
♦    Animals-
(i) As the body size is large, diffusion alone is not enough.
(ii)  Respiratory pigments also required.
(iii) Respiratory pigment in human beings is Haemoglobin, which is present in red blood corpuscles.
(iv) It has very high affinity for Oxygen.
(iv) Carbon dioxide is more soluble in water than Oxygen, so it
Gets dissolves in blood and is thus transported.
v  Transportation
o Transportation in human beings-
♦    Blood-
(i) It is a fluid connective tissue.
(ii) Components-
(1) Fluid medium- Plasma (2) Red blood corpuscles (3) White blood corpuscles
(4) Platelets suspended in plasma
(iii)  Plasma transports food, Oxygen, Carbon dioxide, Nitrogenous wastes, etc.
♦    Functions of blood-
(i) Transport of respiratory gases.
(ii) Transport of nutrients.
(iii) Transport of waste products.
(iv) Defence against infection
♦    Blood vessels- (i) Arteries (ii) Veins (iii) Capillaries

Arteries
Veins
1.  Thick walled.
2.  Deep seated.
3.  Carry blood away from the heart.
4.  Carry Oxygenated blood.
5.  Valves absent.
1.  Thin walled.
2.  Superficial.
3.  Carry blood to the heart.
4. Carry Deoxygenated blood.
5.  Valves present
♦   Heart- 
(Refer to figure 6.10 page no. 106 of N.C.E.R.T  Text book)

(i) It is a muscular organ, which works as a pump in the circulatory system.
(ii)  It is the size of our fist.
(iii)  It has two sides, which are separated by a partition so that the oxygenated and deoxygenated blood do not get mixed up.
(iv) It has four chambers-

Two upper chambers called Atria.
Two lower chambers called Ventricles.
♦    Working of heart- Left side-

(i)  Left atrium relaxes & the  Oxygenated blood enters it from the lungs through the pulmonary vein.
(ii)  Left atrium contracts & the blood enters the left ventricle through the valve.
(iii) Left Ventricle contracts and the blood is pumped into the
largest artery ‗Aorta‘ and is carried to all parts of the body.
♦ Working of heart-Right side-

(i) Right atrium relaxes & the deoxygenated blood from the body  enters it through superior and inferior Vena cava.
(ii)  Right atrium contracts & the blood enters the right Ventricle through the valve.
(iii) Right Ventricle contracts and the blood is pumped into the Pulmonary artery and is carried to lungs.
♦    Valves- Unidirectional to prevent the backward flow of blood.
♦    Pulmonary vein is the only vein that carries Oxygenated blood.
♦    Aorta is the only artery that carries Deoxygenated blood.
♦    Double circulation in man- because the blood passes through the heart twice in one complete cycle of the circulation.
♦    Capillaries-

(i) Form the connection between arteries & veins.
(ii) Walls are one cell thick only for easy exchange of blood.

♦    Platelets- Plug the leaks of arteries and veins by clotting the blood.
♦    Lymph- Extracellular fluid similar to plasma but colourless with lesser protein.
♦    Function of lymph-
(i) Transportation of digested & absorbed fats from the small intestine.
(ii)  Drains excess fluid from the intercellular spaces back in the blood.

♦    Higher animals- E.g., birds, mammals.

(i)Oxygenated blood & Deoxygenated blood are completely separate for efficient Oxygen supply.
(ii)This is  to fulfil higher energy needs and to maintain body temperature (warm blooded animals).

♦    Amphibians & reptiles- have 3 chambered heat where little mixing of  Oxygenated blood & Deoxygenated blood takes place. Therefore their body temperature varies with the temperature of the environment. (cold blooded animals)

o Transportation in plants-

♦    Plants need less energy needs- because they do not move and therefore have a slow
transport system
♦    Transport of water-
(i) Takes place by xylem tissue present in roots, stem, leaves and is therefore interconnected.
(ii) Root cells take up ions from the soil, which creates a concentration difference between root and soil. Column of water therefore rises upwards.

♦    In very tall plants- transpiration creates a suction pressure, which pulls the water upwards.
♦    Importance of transpiration-

(i) Helps in upward movement of water in plants.
(ii) It regulates the temperature in plants.
♦    Transport of food-

(i)  Takes place by phloem tissue.
(ii) Movement of prepared food in plants is called translocation.

➣  Excretion- The biological process of removal of harmful metabolic wastes in living organisms.
➣  Excretion in human beings-

(Refer to figure 6.13 page no. 110 of N.C.E.R.T  Text book)
♦    Organs of excretory system-

(i) Kidneys        (iii) Urinary bladder
(ii) Ureters         (iv) Urethra

♦     Kidneys-

(i)         Two in number
(ii)        Bean shaped
(iii)       Present in abdomen on either side of the backbone
(iv)       Basic unit is nephron.

a) Glomerulus- Group of capillaries (cluster) present in Bowman‘s
capsule to receive blood from renal artery and filters it.

b) Bowman‘s capsule- Cup shaped structure, which contains glomerulus.

c) Convoluted tubule- is long and reabsorbs vital nutrients like glucose, amino acids, salts, urea and water.
Note-Vital functions of kidneys-
(a) Filtration & removal of Nitrogenous wastes
(b) Reabsorption of vital nutrients

♦    Ureters- Transport the urine formed in the kidneys to the urinary bladder.
♦    Urinary bladder- Muscular bag like structure to store urine.
♦    Urethra- Helps in removal of urine when the Urinary bladder is full.
♦    Artificial kidney- Principle: Dialysis

➣ Excretion in plants-

♦    Gaseous wastes- CO2  in respiration & O2 in photosynthesis are removed by the process of diffusion.
♦    Excess water- is removed by transpiration.
♦    Other wastes-
(i) Stored in cellular vacuoles or in leaves, which fall off or as gums, resins, etc. in old xylem.
(ii)  Excreted in soil.

➣  Important diagrams-

1.   Open & close stomata
2.   Steps of nutrition in Amoeba
3.   Alimentary canal of human beings/ Digestive system of human beings
4.   Respiratory system of human beings
5.   Structure of heart.
6.   Excretory system of human beings
7.   Structure of nephron

➣ Important activities-

1.   To prove that chlorophyll is necessary for photosynthesis.
2.   To prove that Carbon dioxide is necessary for photosynthesis.
3.   To prove that light is necessary for photosynthesis.
4.   To prove that product of fermentation is Carbon dioxide.
5.   To prove that leaves lose water by transpiration.
6.   To study the action of salivary amylase on starch.
7.   To demonstrate that Carbon dioxide is present in exhaled air.
8.   To demonstrate the process of transpiration in plants.

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Management of Natural Resources, class 10th

Management of Natural Resources for Class 10th

Science Class 10 Notes for Management of Natural Resources

1. Anything in the environment which can be used is called a natural resource.

Controlling system for the use of natural resources in such a way as to avoid their wastage and to use them in the most effective way is called management of natural resources.

Ganga Action Plan (GAP) was formulated to reduce pollution load of river Ganga by more than 75%. The water quality has been tested from time to time by checking coliform (group of harmless bacteria in human intestine) number/ 100 ml.

2. Forest and wild life :

Forests are vast areas, located far away from human inhabitation where wild plants of various kinds grow and animals of different varieties live without the intervention of humans.

Forests are “biodiversity hot spots”.

A person with an interest or concern in something is called a stakeholder.

(A) To consider the conservation of forests, we need to look at the stakeholders who are :-

(i) The people who live in or around forests, are dependent on forest products for various aspects of their life.

(ii) The Forest Department of the Government which owns the land and controls the resources from forests.

(iii) The industrialists — from those who use `tendu’ leaves to make bidis to the ones with paper mills — who use various forest produce.

(iv) The wild life and nature enthusiasts who want to conserve nature in its pristine form.

A major programme called silviculture has been started to replenish the forests by growing more trees and plants.

Steps for conservation of energy resources are :

(i) Save electricity, water etc by not using useless.

(ii) Use energy efficient electrical appliances to save electricity.

(iii) Use pressure cooker for cooking food.

(iv) Use solar cookers.

(v) Encourage the use of biogas as domestic fuel.

(vi) Fuel efficient motor vehicle should be designed to reduce consumption of petrol and diesel.

3. Pollution

(A) When coal and petroleum based fuels (like petrol and diesel) are burnt, the products of combustion are : Carbon dioxide, Water, Sulphur dioxide and Nitrogen oxides and if combustion take place in an insufficient supply of air (or oxygen), then some carbon monoxide is also produced. Out of all the products of combustion

of these fuels, only water is harmless and does not affect the environment. All other products are harmful and hence pollute the environment.

(B) The harnessing of water resources by building dams has social, economic and environmental implications. Alternatives to large dams exist. These are locale-specific and may be developed so as to give local people control over their local resources.

The fossil fuels, coal and petroleum, will ultimately be exhausted. Because of this and because their combustion pollutes our environment, we need to use these resources judiciously.

The destruction of forests affects not just the availability of forest products but also the quality of soil and the sources of water.

Large scale killing of snakes disrupts the food chains in which snakes occur and creates and imbalance in nature.

The various sources of water which are available to us are: Rains, Rivers, Lakes, Ponds, Wells, Oceans and Glaciers (Snow mountains). Rain is a very important source of water.

The pollution of river water is caused by the dumping of untreated sewage and industrial wastes into it.

The contamination of river water can be usually found from two factors :

(i) the presence of coliform bacteria in river water, and

(ii) measurement of pH of river water.

(a) Rain water harvesting is an age-old practice in India. Water-harvesting techniques used depend on the location where it is to be used.

Various advantages of water stored in the ground are :-

(i) The water stored in ground does not evaporate.

(ii) The water stored in ground spreads out to recharge wells and provides moisture for crops over a wide area.

(iii) The water stored in ground does not promote breeding of mosquitoes (unlike stagnant water collected in ponds or artificial lakes).

(iv) The water stored in ground is protected from contamination by human and animal

(b) Traditional Water Harvesting Systems.

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Environment, class 10th

Environment for Class 10th

Science Class 10 Notes for Our Environment

Introduction

The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land) and all the organisms such as plants, animals, human beings and micro organisms like bacteria and fungi (called decomposers).



The waste materials produced by the various activities of man and animals are poisonous to some extent and can be divided into two main groups :

1. Biodegradable wastes, and
2. Non-biodegradable wastes.

Ecosystem

An ecosystem is a self-contained unit of living things (plants, animals and decomposers), and their non-living environment (soil, air and water). e.g. a forest, a pond, a lake, a greenland etc.
There are two components of an ecosystem : biotic component and abiotic component.
Biotic component : It includes three types of organisms:
Producer
Consumer
Decomposer/saprophyte
Abiotic component
Consumers can be further divided into three groups : herbivores, carnivores and omnivores.
Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean. Planktons are of two types : Phytoplanktons and Zooplanktons.
The microscopic aquatic plants freely floating on the surface of water are called phytoplanktons.
The microscopic aquatic animals freely floating on water are called zooplanktons. The freely floating protozoa are an example of zooplankton.
The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces, urine, etc. into simpler substances are called decomposers.
Food Chains and Webs

The sequence of living organisms in a community in which one organism consumes another organism to transfer food energy, is called a food chain.

A food chain is unidirection where transfer of energy takes place in only one direction.

In aquatic ecosystem of the biosphere, like fresh water ponds, lakes or sea, the food chain starts with microscopic free floating plants (phytoplankton)



The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.

The inter-connected food chains operating in an ecosystem which establish a network of relationships between various species, is called a food web.

How do our activities affect the environment Global Warming

The addition of certain pollutants like the carbon dioxide gases increases the temperature of the earth.

The reduction in the forest cover also contributes to the heating of earth. This is called global warming.

Ozone Layer formation and importance Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone, is a deadly poison. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms.

Ozone at the higher levels ofthe atmosphere is a product of UV radiation acting on oxygen (O2) molecule. The higher energy UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms.

The deplation of ozone layer is due to CFC (chloro fluorocarbons).

SOME IMPORTANT POINTS

Flow of materials in an ecosystem is cyclic but flow of energy is unidirectional.

There is a continuous transfer of energy from one trophic level of organisms to the next in a food chain.

Ten percent law states that only 10 percent of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.

The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification.

The disposal of waste should be done in a scientific way. There are different methods of waste disposal. The method to be used depends on the nature of the waste. Some of the important modes of waste disposal are :

(i) Recycling
(ii) Preparation of compost
(iii) Incineration
(iv) Landfill
(v) Sewage treatment

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The Human Eye and the Colourful World, class 10th

The Human Eye and the Colourful World for Class 10th 

Science Class 10 Notes for The Human Eye and the Colourful World

1. The Human Eye It is a natural optical instrument which is used to see the objects by human beings. It is like a camera which has lens and screen system.

(i) Retina : It is a light sensitive screen inside the eye on which image is formed. It contains rods and cones.

(ii) Cornea : It is a thin membrane which covers the eye ball. It acts like a lens which refracts the light entering the eye.

(iii) Aqueous humour : It is fluid which fills the space between cornea and eye lens.

(iv) Eye lens : It is a Convex lens made of transparent and flexible jelly like material. Its curvature can be adjusted with the help of ciliary muscles.

(v) Pupil : It is a hole in the middle of iris through which light enters the eye. It appears black because light falling on it goes into the eye and does not come back.

(vi) Ciliary muscles : These are the muscles which are attached to eye lens and can modify the shape of eye lens which leads to the variation in focal lengths.

(vii) Iris : It controls the amount of light entering the eye by changing the size of pupil.

(viii) Optical nerve : These are the nerves which take the image to the brain in the form of electrical signals.

2. Accomodation power : The ability of eye to change the focal length of eye lens with the help of ciliary muscles to get the clear view of nearby objects (about 25 cm) and far distant objects (at infinity).

3. Colour blindness : Some people do not possess some cone cells that respond to certain specific colours due to genetic disorder.

4. Myopia (Short sightedness) : It is a kind of defect in human eye due to which a person can see near objects clearly but he can not see the distant objects clearly. Myopia is due to

(i) excessive curvature of cornea.

(ii) elongation of eye ball.

5. Hypermetropia (Long sightedness) : It is a kind of defect in human eye due to which a person can see distant objects properly but cannot see the nearby objects clearly. It happens due to

(i) decrease in power of eye lens i.e., increase in focal length of eye lens.

(ii) shortening of eye ball.

6. Presbyopia : It is a kind of defect in human eye which occurs due to ageing. It happens due to

(i) decrease in flexibility of eye lens.

(ii) gradual weakening of cilliary muscles.

7. Astigmatism : It is a kind of defect in human eye due to which a person cannot see (focus) simultaneously horizontal and vertical lines both.

8. Cataract : Due to the membrane growth over eye lens, the eye lens becomes hazy or even opaque. This leads to decrease or loss of vision.

The problem is called cataract. It can be corrected only by surgery.

9. Dispersion of white light by a glass prism : The phenomenon of splitting of white light into its seven constituent colours when it passes through a glass prism is called dispersion of white light. The various colours seen are Violet, Indigo, Blue, Green, Yellow, Orange and Red. The sequence of colours remember as•VIBGYOR. The

band of seven colours is called spectrum.

10. Composition of white light : White light consists of seven colours i.e., violet, indigo, blue, green, yellow, orange and red.

11. Monochromatic light: Light consisting of single colour or wavelength is called monochromatic light, e.g., sodium light

12. Polychromatic light : Light consisting of more than two colours or wavelengths is called polychromatic light, e.g. white light.

13. Recombination of white light : Newton found that when an inverted prism be placed in the path of dispersed light then after passing through prism, they recombine to form white light.

14. Formation of rainbow : The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.

15. Atmospheric Refraction : The refraction of light caused by the earth’s atmosphere (having air layers of varying optical densities) is called atmospheric refraction.

16. Why, the duration of day becomes approximately 4 minutes shorter if there is no atmosphere on earth : Actual sun rise happens when it is below

the horizon in the morning. The rays of light from the sun below the horizon reach our eyes because of refraction of light. Similarly, the sun can be seen about few minutes after the actual sun set. Thus the duration of, day time will increase by 4 minutes.

17. Scattering of light : According to Rayleigh’s law of scattering the amount of scattered light

α/(wavelength )4

So that the wavelength of violet, blue and indigo is small as compared to the rest of the colours. So sky appears blue in colour.

18. Colour of the Sun at sunrise and sunset : At noon, the light of sun travels relatively shorter distance through earth’s atmosphere thus appears white as only a little of blue and violet colours are scattered. Near the horizon, most of the blue light and shorter wavelengths are scattered and sun appears red.

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Light (Reflection and Refraction) , class 10th

Light (Relection and Refraction) for Class 10th

Science Class 10 Notes for Light (Reflection and Refraction)

1. Ray of Light : A line drawn in the direction of propagation of light is called a ray of light.

2. Beam of Light : A group of rays of light emitted by a source of light is called a beam of light. A light beam is of three types.

(i) Parallel beam : A group of light rays parallel to each other is known as parallel beam of light. 7.

(ii) Divergent beam : A group of light rays spreading out from a source of light is called divergent beam of light.

(iii) Convergent beam : A group of light rays meeting at a point is called convergent beam 8. of light.

3. Reflection of Light : There are some surfaces which have ability to send the light back in the same medium when light strikes it. This 9. phenomena of sending the light back in the same medium by a surface is called reflection of light.

(i) The incident ray, the reflected ray and the normal at the point of incidence, all lie in a same plane.

(ii) The angle of incidence is always equal to the angle of reflection, ∠i = ∠r.

4. Image : When light rays meet or appear to meet after reflection from a mirror,then it is called an image.

1. Real Image : It is a kind of image which is formed by actual intersection of light rays after reflection.

2. Virtual Image : It is a kind of image which is formed by producing the reflected rays backward after reflection.

5. Plane Mirror : Plane mirror is a piece of glass whose one side is polished by using silver paint, which is covered by a coating of red paint to protect the silver layer.

6. Spherical Mirrors : It is part of hollow glass sphere whose one surface is polished.

There are two types of spherical mirror.

(i) Concave Mirror : It is a spherical mirror whose outer surface is polished and inner or concave side is reflecting surface.

(ii) Convex Mirror : It is a spherical mirror whose inner is polished and outer side or convex side is the reflecting surface.

Principal Focus :

A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appear to meet after reflection from the mirror.

Focal Length :

The distance between the pole (P) and principal focus(F) of a spherical mirror is called the focal length of the mirror. It is denoted by f.

Uses of Concave Mirror :

(i) It is used as a shaving mirror because when it is placed close to the face, it forms a large image.

(ii) It is used in solar heating devices like solar cooker, because it converges Sun’s rays over a small area to produce high temperature.

(iii) It is used for security checking purposes.

10. Uses of Convex Mirror :

(i) It is used as rear view mirror in automobiles because it gives erect image as well as diminished due to which Pt has wider field of view.

(ii) It is also used in street lights.

11. Mirror Formula :

It is a relation between distance of object, distance ofimage from the pole ofthe mirror and it’s focal length, i.e., relation between ‘u’, ‘v and It is given by

12. Magnification : It is defined as the ratio of height of image to the height of the object. It is denoted by letter m.

13. Refraction of Light : The bending of ray of light when it passes from one medium to another is called refraction of light.

Laws of Refraction :

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

(ii) When a ray of light undergoes refraction then the ratio of sine of angle of incidence to the sine of angle of refraction is constant.

14. The Refractive Index : The refractive index of medium 2 with respect to medium is given by the ratio of the speed of light in medium 1 and the speed of light in medium 2. This is usually represented by the symbol n21. This can be expressed in an equation form as

15. Refraction by spherical lenses : Lens is a transparent medium which is formed by joining two pieces of spherical glass. There are two types of lenses.

(i) Convex Lens : It is a lens which is thicker at the centre and thinner at the edges.

(ii) Concave Lens : It is a lens which is thinner at the centre and thicker at the edges.

16. Terms related to a lens

Optical Centre of Lens : It is the centre of the lens through which light can pass without any deviation.

Principal Axis : It is the line passing through optical centre and is perpendicular to the line joining its edges.

Principal Focus : It is a point on the principal axis where all light rays which are parallel to principal axis either converge or appear to diverge from, after refraction.

17. Lens formula :

18. Magnification : Magnification, m = h2/h1

Ratio of height of image to the height of object.

It is also given by v/u i.e., Ratio of distance of image to the distance of object.

19. Power of a lens : A beam of light parallel to principal axis either gets converged or diverged after refraction by a lens. Some lenses converge the beam of light to a small extent and some lenses converge it to a large extent. This ability of lens to converge or diverge a beam of light is known as the power of lens.

Si unit of power of lens is dioptre : One dioptre is the power of a lens whose focal length is 1 m.

Power of a combination of two or more lenses :

If two or more lenses are placed together to form a combined lens then the power of this combined lens is equal to the sum of the powers of individual lenses.

P = P1 + P2 + P3 + ……

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Heredity and Evolution, class 10th

Heredity and Evolution for Class 10th

Science Class 10 Notes for Heredity and Evolution

1. The transmission of characters from parent to their offsprings is known as heredity.

The study of heredity and variations is known as genetics.

Clones are those organisms which are the carbon copies of one another.

Variation in sexually reproducing organisms are caused due to the following factors like environment, crossing over and recombination of genes and mutation.

The first study of inheritance was done by Gregor Mendel on garden pea.

Paired condition of chromosomes is known as diploid.

Unpaired condition of chromosomes is known as haploid.

DNA (Deoxyribo Nucleic Acid), RNA (Ribo Nucleic Acid) is the genetic material in all organisms.

2. Mendel’s laws of inheritance are

(i) Law of Dominance

(ii) Law of Segregation (Law of purjty of gametes)

(iii) Law of Independent Assortment

3. Genotype is the composition of genes present in an organism and the characteristic which is visible in an organism is called its phenotype.

4. When two parents cross (or breed) to produce progeny (or offsprings), then their progeny is called F1-generation (First Filial Generation) and when the first generation progeny cross among themselves to produce second progeny, then this progeny is called F2-generation or second Filial Generation.

Mendel conducted his famous experiments on garden pea (Pisum sativum).

He used a number of contrasting characters like round / wrinkled seeds, tall/ short plants, white/ violet flowers and so on.

5. During Monohybrid Cross

When tall pea plants are crossed with short pea plants then in Fi generation only tall plants were obtained.

F2 progeny ofFi tall plants are not all tall but one quarter of them are short indicating that both tallness and shortness traits were inherited in F1 but only tallness trait was expressed due to dominance.

In dihybrid cross two pairs of contrasting characters were considered. Tall plant with round seeds were crossed with short plant with wrinkled seeds. In Fi tall plants with round seeds were obtained. On selfing these F, plants with F2 produced tall plants with round seeds, short plant with wrinkled seeds and some new combinations (tall plant with wrinkled seeds and short plant with rounds seeds) were also obtained. The tall/short trait and round wrinkled traits are independently inherited.

The expression of a particular trait is controlled by gene.

6. DNA is the source of making protein in a cell.

The section of DNA that provides information for one protein is called gene.

7. Physical and Chemical Basis of Heredity

Mendel (1866) said that heredity was controlled by particles, called germinal units, or factors.

8 Sex determination is the process by which the sex of a person is determined.

All human chromosomes are not paired. 22 pairs are called autosomes. Women have a perfect pair of sex chromosomes XX. But men have a mismatched pair XY.

9. Evolution

It is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced.

A. The evidences of evolution are :

i. Homologous organs,

ii. Analogous organs, and

Fossils

B. Theories of Evolution

Jean Baptiste Lamarck gave the first theory of evolution.

Darwin’s Theory of Evolution

Charles Robert Darwin (1809-1882) explained the evolutionary principle in his famous book “The origin of species”. The theory proposed by him is popularly known as theory of natural selection or Darwinsim.

The main features of the theory of natural selection are as follows:

(i) Over production

(ii) Limited food and space

(iii) Struggle for Existence

(iv) Variations

(v) Natural Selection or Survival of the Fittest

10. Speciation : The process by which new species develop from the existing species is known as speciation.

The factors which leads to speciation are :

Geographical isolation

Genetic drift and

Variations

11. Classification

Evolutions are of three types :-

(i) Convergent Evolution

(ii) Divergent Evolution, and

(iii) Parallel Evolution.

12. Fossils : The remains of dead plants or animals that lived in the remote past are known as fossils.

Various kinds of fossils are : Ammonite, Trilobite and Dinosaur.

13. Evolution by Stages : Evolution of complex organs have taken place bit-by-bit over generations.

For example eye, feathers of birds have evolved because of survival advantage of intermediate stages.

Thus changes in DNA during reproduction are the main cause of evolution.

14. Human Evolution : All have beings belong to single speceis Homo sapiens, although there were many races of humans.

They have originated in Africa, some ancestors left Africa and migrated to West Asia, Central Asia, Eurasia South Asia, East Asia, Indonesia, Australia, America, while others stayed there.

Excavating, time-dating, studying fossils, determining DNA Sequences have been used for studying human evolution.

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How do Organisms Repoduce? , class 10th

How do Organisms Reproduce for Class 10th

1. The production of new organisms from the existing organisms ofthe same species is known as reproduction.

2. Asexual Reproduction : Modes of sexual reproduction used are binary fission, multiple fission, Budding, spore formation, regeneration, vegetative propagation, tissue culture, fragmentation

3. Sexual Reproduction : In sexual reproduction, a male gamete (germ cells) fuses with a female gamete to form a new cell called ‘zygote’. This zygote then grows and develop into a new organism in due course of time.

When male gamete and female gamete fuse, they form a zygote and the process is known as fertilization.

Fertilization is of two types :– External fertilization and Internal fertilization.

4. Sexual Reproduction in Flowering Plants :

Flower is meant essentially for sexual reproduction.

Pollination is the process in which pollen grains are transferred from the anther to stigma of the carpel. It is of two types self pollination and cross-pollination.

In the fertilization process primary endospermic nucleus is formed.

After the fertilization process, ovary developes into the fruit whereas ovules into the seed.

5. Reproduction in Human Being : The sex organ in males are testes and ova in females.

Male reproductive organ consist of a pair of testes, vasdeferens, a pair of epididymis, a pair of ejaculatory duct, urethra, pairs of accessory gland.

Female reproductive part consist of a pair of ovaries, a pair of fallopian tube, uterus, vagina, external genitalia, mammary glands and accessory glands. Ovary produces the female gametes (eggs or ova) and female sex hormone (estrogen).

If sperms are present, fertilization of ovum takes place in the upper end of the fallopian tube.

Bleeding accompanied by discharge of soft tissue lining the reproductive tract is menstrual flow. It last for 3-5 days.

Secretory phase lasts for 12-14 days.

Fertilization process occurs in fallopian tube. In this process zygote is formed. In this process umbilical cord is produced which is attached to foetus. During this

process two hormones are produced which are estrogen and progesterone.

Progesterone stops mensturation and prevents ovulation. The placenta protects the body against diseases. Due to contraction of uterine muscles young one is expelled and the phenomenon is called parturition.

If the egg is not fertilized, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares it self every month to recieve a fertilized egg.

After the age of 45-50 years menses stop and process is called menopause.

Fertility control can be done chemically, mechanically or surgically.

6. Reproductive Health Barrier methods

(i) Mechanical barrier method:- They prevent contraception by preventing either sperms from entering uterus or preventing implantation if fertilization has occurred.

The instruments are condom, cercival cap, diaphragm & ICDU method.

(ii) Hormonal method: They are used by women for suppressing the production of ovum. i.e. , oral pills, Implants morning after pills.

(iii) Chemical contraception: They are creams, jellies and foaming tables which are placed in vagina for killing the sperms at the time of coitus.

(iv) Surgical techniques:—

(a) Vasectomy: — The two vasa deferential of the male are blocked by cutting a small piece of tying the rest. This prevents the passage of sperms from testes to semen.

(b) Tubectomy:— A portion of both the fallopian tubes is excised to ligated to block the passage of ovum

7. Sexually Transmitted Diseases (STDs)

It is a group of infections caused by different types of pathogens that are transmitted by sexual contact between a healthy person and an infected person. The sexually transmitted diseases are also called venereal diseases (VDs). Some 30 different types of STDs are known. Fol example : Gonorrhoea, Syphilis, Trichomonas, Genital warts, AIDS.

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