1. About Life Processes & Nutrition

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1. About Life Processes & Nutrition

Chapter 6

Life Processes


  • Nutrition: The process by which an organism takes food and utilizes it, is called nutrition.
  • Need for Nutrition: Organisms need the energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
  • Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
  • Modes of Nutrition
    1. Autotrophic Nutrition.
    2. Heterotrophic Nutrition.

Autotrophic Nutrition

  • The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
  • The organisms which carry out autotrophic nutrition are called autotrophs (green plants).
  • Autotrophic nutrition is fulfilled by the process, by which autotrophs intake CO2 and H2O, and convert these into carbohydrates in the presence of chlorophyll, sunlight is called photosynthesis.
  • Nutrition in Plants: Green plants prepare their own food. They make food in the presence of sunlight. Sunlight provides energy’, carbon dioxide and water are the raw materials and chloroplast is the site where food is made.

The site where photosynthesis occurs is known as chloroplast. They contain a green colour pigment known as chlorophyll that traps sunlight for photosynthesis.

The steps of photosynthesis are as follows-

  • Absorption of light by chlorophyll.
  • Conversion of light energy into chemical energy.
  • Splitting of water into hydrogen and oxygen.
  • Finally, reduction of carbon dioxide into carbohydrates.

Leaves contain small openings known as stomata which helps in the exchange of gases. The stomata/stoma is surrounded by a guard cell which guards the opening and closing of stomata. Guard cells also contain chloroplast.

Heterotrophic Nutrition

In this mode of nutrition, an organism is unable to synthesise its food. It is of the following types-

  1. Holozoic nutrition is a type of nutrition where an organism takes in whole food and breaks it inside the body. For example, Amoeba.
  2. Saprophytic nutrition is nutrition in which organisms feed on dead and decaying matter. For example, fungi.
  3. Parasitic nutrition is nutrition in which an organism feeds on a living host. For example, Cuscuta.

Nutrition in Amoeba

  • Amoeba feeds by holozoic mode of nutrition.
  • It engulfs the food particle using pseudopodia, the process is called phagocytosis.
  • The engulfed food gets enclosed in a food vacuole.
  • As the food vacuole passes through the cytoplasm, digestion, absorption and assimilation take place.
  • When the food vacuole opens to outside, the egestion of undigested food takes place.

Nutrition in Paramecium

  • Paramecium also exhibits holozoic nutrition.
  • However, they have cilia that help them to engulf the food through the oral groove.
  • A food vacuole is created enclosing the food.
  • It moves through the cytoplasm, the process is called cyclosis.
  • Food digested in the food vacuole is absorbed by the cytoplasm.
  • Undigested food is given out to a tiny pore called anal pore or cytopyge.

 Nutrition in Human beings

Humans consist of the alimentary canal which starts from the mouth and ends at the anus. The parts of the alimentary canal are as follows-

  1. Mouth
  2. Pharynx
  3. Oesophagus/food pipe
  4. Stomach
  5. Small intestine
  6. Large intestine
  7. Rectum
  8. Anus


Human Digestive System 

Mouth is the first portion of the alimentary canal. The mouth consists of a muscular tongue and teeth. The cavity inside the mouth is known as the oral cavity.

Mechanism of Digestion of Food

  • Food digestion process begins in the mouth. Food is complex in nature.
  • To break down food and absorb it, we need biological catalysts known as enzymes.
  • The mouth contains salivary glands that secrete saliva. Saliva contains an important enzyme known as the salivary enzyme that breaks down starch into simple sugars.
  • The food then passes via the oesophagus into the stomach. The movement of the food inside the oesophagus occurs via rhythmic contraction of muscles, this is known as peristalsis.
  •  The stomach contains gastric glands that secrete mucus, hydrochloric acid and pepsin. Pepsin is a protein-digesting enzyme.
  • After the stomach, food then enters the small intestine. The small intestine is larger in herbivores due to cellulose digestion compared to carnivores.
  • Complete digestion of carbohydrates, proteins and fats occurs in the small intestine.
  • The small intestine receives secretions from the pancreas and bile from the liver. Bile helps in the emulsification of fats whereas the pancreas secretes enzymes such as trypsin for protein digestion. The intestinal wall also contains glands that secrete intestinal juice.
  • The small intestine has villi that increase the surface area for the absorption of food.
  • The unabsorbed food is then transferred to the large intestine where water is absorbed.
  • Undigested food is then expelled out from the anus.

1. Animals Nervous System

Chapter 7

Control and Coordination


Different organs work together in an organism to carry out different functions, this is known as coordination. Proper control and coordination is necessary to carry out essential functions of the life.

Animal Nervous Tissue

  • Animals’ nervous system consists of specialized nerve cells also known as neurons.
  •  A typical neuron consists of cell body, axon and dendrites.
  • Cell body contains nucleus.
  • Dendrites detects the information from the environment. This information is picked up by the dendritic tips and sets off the electrical impulse which travels from dendrite to cell body and then to axon.

Structure of Neuron

Reflex Action
A sudden response to some environment stimulus is known as reflex. For example, we sudden take off our hand from the flame without thinking.

Reflex Arch
Sensory neurons synapse in the spinal cord before it passes to the brain. This pathway is known as reflex arch.

Reflex Arch

Human Brain

Brain is divided into forebrain, midbrain and hindbrain.

  • Forebrain consists of cerebrum, hypothalamus and thalamus. Forebrain is specialized in hearing, sight, smell etc. It also controls voluntary movements in our body such as movement of leg muscles. Centre for hunger is also located in the separate part of forebrain. Cerebrum or the cerebral cortex consists of 4 lobes- parietal lobe, temporal lobe, occipital lobe and frontal lobes.

Different Lobes of the Brain 

  • Midbrain is located between the forebrain and hindbrain. It controls certain involuntary actions in the body.
  • Hindbrain consists of pons, medulla and cerebellum. It controls salivation, blood pressure and vomiting. Cerebellum also controls certain important functions such as riding a bicycle, picking up a pencil. It also maintains posture and balance of the body. 

Structure of Human Brain 

Brain is protected in a bony case known as cranium. Cranium also contains a fluid filled in it known as cerebrospinal fluid (CSF) that protects the brain from mechanical shock and injury. And spinal cord is protected by vertebral column.

How nervous tissue causes action?   

Information is received by nervous tissue, then it passes to brain muscles and then it causes the action. The junction between the two neurons is known as synapse. Information are passed from one neuron to another neuron via electrical or chemical transmission.


1. What is Reproduction?

How do organisms reproduce

Sample question paper

  • What is difference between sexual reproduction and asexual reproduction
  • What is difference between binary fission and multiple fission
  • Explain the binary fission in case of amoeba
  • What do you mean by vegetative propagation and what are its advantages
  • Define grafting
  • What are artificial methods of reproduction what is the difference between cutting and layering
  • What do you mean by pollination what are the two different types of pollination explain them along with figure
  • What do you mean by fertilization
  • What are four different parts of the flower explain all of them along with their function
  • What is the other name of female part of a flower
  • What are angiosperm flowers


In order to get the answers of the sample paper  and recorded video lecture on different topics WhatsApp number 7007 8207 83


1. What is Reproduction?

Chapter 8

How do organisms reproduce?

Reproduction: It is the process by which living organisms produce new individuals similar to themselves.

  • Reproduction ensured continuity of life on earth.
  • It is a bridge to hereditary transmission.
  • It involves a continuation of characters from the parents to daughter cells by copying of DNA (Deoxyribose Nucleic Acid) molecules present in the chromosomes of the cell.
  • Copying of DNAs is also not a fool proof exercise, even minute changes bring about variation in the blue print of the off springs.
  • The useful variations are retained while the harmful ones do not go beyond.
  • Actually, variations help the species to withstand drastic environmental changes, thus save the species from becoming extinct and promotes its survival for a longer time.
  • This inbuilt tendency of variation is the “basis” for Evolution.

Sexual Reproduction: When reproduction takes place as a result of the fusion between two gametes, one from each parent, it is called sexual reproduction.

  • This process of fusion between two gametes is called fertilization.
  • The formation of gametes involves an exchange of chromosomal (genetic) fragments between homologous chromosomes causing genetic recombination which leads to variation.

Asexual Reproduction

  • It involves only one parent.
  • There is no formation and fusion of gametes. 
  • The young ones formed are almost identical to each other as well as to the parent cell. 
  • Asexual reproduction generally occurs during favorable environmental conditions and when there is an abundance of food.
  • It is a faster method of reproduction.

Importance of variation
Using the ability to reproduce, living organisms increase their population and feed on available resources in their niche. Changes in DNA and body design may result in difficulty to sustain themselves in their habitat. But we know that the environment is not consistent. It changes with the change in different factors like climate, temperature, availability of resources, etc. During these environmental changes, if a particular species is too adamant to change, it can’t survive in that habitat. Here comes the role of variation. Variations in species help them to adapt themselves to that particular environment and give them a chance of survival.

1. Heredity

Chapter 9

Heredity and Evolution

Heredity is defined as the transmission of characteristics from parents to offspring.
The differences in characters of parents and offspring are known as variations
There are two types of variations - somatic variations and genetic variation.

  • Somatic variations occur in the somatic cell of the body. They are not inherited or transmitted in the next generation. So, they are also known as acquired traits.
  • Gametic variations occur in the germ cells of the body. They are inherited in the next generation. So, they are known as inherited traits.

Importance of Variations

  • It is the basis of heredity.
  • It is the basis of evolution also.
  • It increases the chances of the survival of the organism according to the changing environment.

 Causes of variation
The most common causes of variations are mutation, recombination and random mating. Recombination or crossing over is one of the important reasons for variation. It is an exchange of chromosome segments at the time of gamete formation.

Mendel and his contribution to Genetics
G.J. Mendel started his work on Pisum sativum (garden pea). He was known as the Father of genetics. He had chosen seven pairs of contrasting characters-

The reason for choosing garden peas for the experiment was-

  • Short life cycle
  • A large number of seeds produced
  • Self-pollination
  • Several contrasting characters can be found

Mendel Laws 

  • Law of Dominance: If the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance; the other, the recessive allele, has no noticeable effect on the organism’s appearance.
  • Law of Segregation: The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes.
  • Law of Independent Assortment: Each pair of alleles segregates independently of other pairs of alleles during gamete formation

Monohybrid cross
When one pair of contrasting characters is taken to cross two pea plants, it is known as a monohybrid cross.

Monohybrid Cross

 The image depicts the monohybrid cross between the true-breeding yellow pod and the true-breeding green pod. All the pods obtained were green in colour. The offspring obtained are known as F1 progeny or First filial generation.
In the case of the heterozygous condition,

Monohybrid cross with heterozygous parents

In this Image, the parents are heterozygous, so phenotypically 3 purple flowers and 1 white flower were produced. But genotypically, 1 homozygous dominant (BB), 2 heterozygous dominant (Bb) and one homozygous recessive (bb).

Dihybrid cross

When two pairs of contrasting characters are taken to cross two plants, it is known as a dihybrid cross. 

Dihybrid Cross

The phenotypic ratio was found to be 9:3:3:1
9 are round yellow
3 are round green
3 are wrinkled yellow
1 is wrinkled green
But the genotypic ratio was found to be 1:2:1: 2:4:2: 1:2:1.

Sex determination

Sex determination is used to define the sex of the offspring. Environment and genetic factors determine the sex of the offspring. Environmental factors, such as gender in turtles, are determined according to the temperature.

Types of Sex Determination

  • Different types of sex determination are- XX-XY type (humans), XX-XO type (insects), ZW-ZZ type (chicken) and ZO-ZZ type (moths and butterflies).
  • Genetic factors include the presence of sex chromosomes. For example, in humans, the presence of two X chromosomes leads to female offspring whereas the presence of one X and one Y chromosome forms male offspring.
  • In human beings, there are 23 pairs of chromosomes. Out of these 22 pairs of chromosomes are known as autosomes whereas the 23rd pair of chromosomes are known as sex chromosomes or allosomes. The sex of the offspring is determined by the chromosome inherited from the father.

2. Respiration

notes added by teacher sudhanshu in section a

no need to add by Manas from section B

2. Respiration



  • Respiration broadly means the exchange of gases.
  • Animals and plants have different means of exchange of gases.
  • At a cellular level, respiration means the burning of the food for generating the energy needed for other life processes.
  • Cellular respiration may take place in the presence or absence of oxygen.

Cellular Respiration

Cellular respiration is set of metabolic reactions occurring inside the cells to convert biochemical energy obtained from the food into a chemical compound called adenosine triphosphate (ATP).

  • Metabolism refers to a set of chemical reactions carried out for maintaining the living state of the cells in an organism. These can be divided into two categories:These can be divided into two categories:
  • Catabolism – the process of breaking molecules to obtain energy.
  • Anabolism – the process of synthesizing all compounds required by the cells.
  • Therefore, respiration is a catabolic process, which breaks large molecules into smaller ones, releasing energy to fuel cellular activities.
  • Glycolysis, Krebs cycle and electron transport chain are the important processes of the cellular respiration.


  • It is the energy currency of the cell. 
  • ATP stands for Adenosine Triphosphate.
  • This molecule is created as a result reactions like photosynthesis, respiration etc.
  • The three phosphate bonds present in the molecule are high-energy bonds and when they are broken, a large amount of energy is released.
  • Such released energy is then used for other metabolic reactions.

Types of Respiration

1. Aerobic respiration

Aerobic respiration is a process in which the food i.e. glucose is converted into energy in the presence of oxygen.

  • The general equation of aerobic respiration as a whole is as given below-

Glucose + oxygen  Carbon dioxide + Water + Energy

  • This type of respiration takes place in animals, plants and other living organisms.

2. Anaerobic respiration

  • Respiration in muscles can be anaerobic when there is not enough oxygen.
  • Glucose gets broken down into carbon dioxide and lactic acid.
  • This results in the accumulation of lactic acid that makes the muscles sore.
  • This type of anaerobic respiration is also known as lactic acid fermentation. 

Respiration in Humans

  • The human respiratory system is more complex and involves breathing, exchange of gases and cellular respiration.
  • A well-defined respiratory system helps breathing and exchange of gases.
  • Breathing involves the inhalation of oxygen and exhalation of carbon dioxide.
  • The gaseous exchange takes place in the lungs and oxygen is supplied to all cells of the body.
  • Cellular respiration takes place in each and every cell.

 Human Respiratory system

  • The human respiratory system involves the nose, nasal cavities, pharynx, larynx, trachea/windpipe, bronchi, bronchioles and alveoli.
  • Bronchioles and alveoli are enclosed in a pair of lungs.
  • The rib cage, muscles associated with the rib cage and diaphragm, all help in inhalation and exhalation of gases.
  • Exchange of gases takes place between an alveolar surface and surrounding blood vessels.
  • Alveoli provide a large surface area for exchange of gases.

Physiology of Respiration

  • Breathing in humans is facilitated by the action of internal intercostal and external intercostal muscles attached to the ribs and the diaphragm.
  • When the dome-shaped diaphragm contracts and becomes flattened and the rib cage is expanded due to the action of intercostal muscles, the volume of the lungs increases, pressure there drops down and the air from outside gushes in. This is inhalation.
  • To exhale, the diaphragm relaxes, becomes dome-shaped again, chest cavity contracts due to the action of intercostal muscles, the volume inside the lungs decreases, pressure increases and the air is forced out of the lungs.
  • Inhaled air increases the concentration of oxygen in the alveoli, so oxygen simply diffuses into the surrounding blood vessels.
  • Blood coming from cells has more concentration of carbon dioxide than outside air and thus carbon dioxide simply diffuses out of the blood vessels into the alveoli.
  • Thus, breathing takes place due to the combined action of intercostal muscles and diaphragm while the exchange of gases takes place due to simple diffusion.

  ​​​​​​​Inhalation and Exhalation

  • The process of taking in air rich in oxygen is called inhalation.
  • Similarly, the process of giving out air rich in carbon dioxide is called exhalation.
  • One breath comprises one inhalation and one exhalation.
  • A person breathes several times in a day.
  • The number of times a person breathes in one minute is termed as his/her breathing rate.

3. Transportation

Transportation in Human beings


  • All living organisms need a few necessary components like air, water, and food for their survival.
  • On a regular basis, animals ensure these elements by breathing, drinking and eating.
  • The required elements are transported to their body cells and tissues by a transportation system.
  • In plants, the vascular tissue is responsible for transporting the substances.

Transportation in humans

  • Transportation in humans is done by the circulatory system.
  • The circulatory system in humans mainly consists of blood, blood vessels and the heart.
  • It is responsible for the supply of oxygen, and nutrients, and the removal of carbon dioxide and other excretory products.
  • It also helps to fight infections.

Human Heart

  • The muscular organ which is located near the chest slightly towards the left in the thoracic region.
  • The heart is the main pumping organ of the body.
  • The human heart is divided into four chambers which are involved in the transportation of oxygenated and deoxygenated blood.
  • The upper two chambers are called atria whereas the lower two chambers are called as ventricles.

Blood vessels

  • Blood vessels carry blood throughout the body.
  • There three types of blood vessels; arteries, veins and blood capillaries.
  • Arteries carry oxygenated blood and veins carry deoxygenated blood.
  • Gaseous exchange takes place between blood and cells at capillaries.

Difference between Arteries and Veins

Blood Pressure

The pressure exerted by the blood when it flows through the blood vessels is called blood pressure.

  • There are two different variants of blood pressure; systolic and diastolic blood pressure.
  • The pressure exerted on the walls of arteries when the heart is filling with blood is called diastolic pressure. It constitutes the minimum pressure on arteries.
  • The normal range of diastolic blood pressure should be 60 – 80 mm Hg.
  • The pressure exerted on the walls of arteries when the heart is pumping the blood is called systolic pressure. It constitutes the maximum pressure applied to the arteries.
  • The normal range of systolic blood pressure should be 90 – 120 mm Hg.

Transportation in Plants

  • Transportation is a vital process in plants.
  • The process involves the transportation of water and necessary nutrients to all parts of the plant for its survival.
  • Food and water transportation takes place separately in plants.
  • Xylem transports water and phloem transports food.


  • The phloem is responsible for translocation of nutrients and sugar like carbohydrates, produced by the leaves to areas of the plant that are metabolically active.
  • Sieve tubes, companion cells, phloem  fibres, and phloem parenchyma cells are the components of this tissue
  • The flow of material through phloem is bidirectional.

Transport of food in the plant

  • Transport of food in the plant through phloem via a process such as mass flow is called as translocation.
  • Photosynthates i.e. sugars and organic molecules such as amino acids, organic acids, proteins and inorganic solutes like potassium, magnesium, nitrate, calcium, sulfur and iron from source tissues (mature leaves) to the sink cells (areas of growth and storage) are transported through the phloem.
  • Material like sucrose is loaded from leaves to phloem using the energy of ATP.
  • Such a transfer increases the osmotic pressure causing the movement of water from nearby cells into phloem tissue and the material gets transported through the phloem.
  • The same pressure is also responsible for the transfer of substances from phloem to tissues where food is required.
  • Thus the bulk flow of material through phloem takes place in response to an osmotically generated pressure difference.


  • Xylem tissue transports water in plants from root to all other parts of the plant.
  • Xylem tissue is made up tracheids, vessels, xylem fibres and xylem parenchyma.

The flow of water and minerals through xylem is always unidirectional.

 Root pressure

  • Conduction of water through the xylem, from roots to upper parts of plants, is due to many forces acting together.
  • One of the forces responsible for this is root pressure.
  • Root pressure is osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves.
  • Root pressure helps in the initial transport of water up the roots.

Transport of water

Water is absorbed by the roots and is transported by xylem to the upper parts of the plant.
Imbibition, osmosis, root pressure and transpiration are the forces that contribute towards the upward movement of water, even in the tallest plants.

  • Imbibition is a process in which water is absorbed by the solids. E.g. seeds take up water when soaked.
  • Osmosis is a process where water moves from the area of its lower concentration to the area of its higher concentration.
  • At the roots, the cells take up ions by an active process and this results in the difference of concentration of these ions.
  • It leads to movement of water, in the root cells, by osmosis.
  • This creates a continuous column of water that gets pushed upwards. This is root pressure.
  • Transpiration contributes to the upward movement of water by creating a staw effect.
  • It pulls the water column upwards as there is a continuous loss of water from leaves.
  • All these forces act together for water transport through the xylem.

4. Excretion

Excretion in Humans

Excretion is the process of removal of metabolic waste material and other non-useful substances.

  • Organisms like animals have an advanced and specialized system for excretion.
  • But plants lack a well-developed excretory system like that in animals.
  • They do not have special organs for excretion and thus excretion in plants is not so complex.

Excretion in Unicellular organism

  • In unicellular organisms such as amoeba and bacteria, the waste product is removed by simple diffusion through the general body surface.
  • Unicellular organisms like the amoeba, and paramecium excrete excess through tiny organelles called contractile vacuoles.
  • Undigested food in unicellular animals is excreted when the food vacuole merges with the general body surface and opens to the outside.

Excretory system in humans

  • The excretory system in humans includes
  • a pair of kidneys,
  • a pair of ureters,
  • a urinary bladder and
  • urethra.
  • It produces urine as a waste product.


  • Paired kidneys are the main excretory organs of the body.
  • They are basically the filtration units of the human body.
  • Each kidney is made up of many tiny filtration units called nephrons.
  • Kidneys perform crucial functions like: 
  • Filtering waste materials, medications, and toxic substances from the blood.
  • Regulation of osmolarity i.e., fluid balance of the body.
  • Regulation of ion concentration in the body.
  • Regulation of pH.
  • Regulation of extracellular fluid volume.
  • Secreting hormones that help produce red blood cells, promote bone health, and regulate blood pressure.


Nephrons are the structural and functional unit of kidney.

  • Each kidney has millions of nephrons and it forms the basic structural and functional unit of the kidney.
  • Each nephron has two parts: Malpighian body and renal tubule.
  • Malpighian body is made up of cup-like structure called Bowman’s capsule which encloses a bunch of capillaries called glomerulus.
  • They together filter waste materials along with many useful substances.
  • Renal tubule has regions called proximal convoluted tubule, Loop of Henle and distal convoluted tubule.
  • These regions absorb back useful substances into the blood and also filter remaining waste substances.
  • The output from nephrons is called urine.


When the kidneys fail, it results in a lot of complications and to compensate this situation a technology called dialysis has been developed.
It uses a machine filter called a dialyzer or artificial kidney.
This is to remove excess water and salt, to balance other electrolytes in the body and remove waste products of metabolism.
Blood from the body is removed and flowed through a series of tubes made up of a semipermeable membrane.
A dialysate flows on the other side of the membrane, which draws impurities through the membrane.

Excretion in plants

  • The cellular respiration, photosynthesis, and other metabolic reactions produce a lot of excretory products in plants.
  • Carbon dioxide, excess water produced during respiration and nitrogenous compounds produced during protein metabolism are the major excretory products in plants.
  • Plants produce two gaseous waste products i.e., oxygen during photosynthesis and carbon dioxide during respiration.
  • Excretion of gaseous waste in plants takes place through stomatal pores on leaves.
  • Oxygen released during photosynthesis is used for respiration while carbon dioxide released during respiration is used for photosynthesis.
  • Excess water is excreted by transpiration.
  • Organic by-products generated by the plant are stored in different forms in different parts.
  • The gums, oils, latex, resins, etc. are some waste products stored in plant parts like barks, stems, leaves, etc.
  • Eventually, plants shed off these parts.
  • Few examples of the excretory products of plants are oil produced from orange, eucalyptus, jasmine, latex from the rubber tree, papaya tree, and gums from acacia.
  • Sometimes plants even excrete into the soil.

2. Coordination in Plants

Basics Revisited


An equation is a statement that two mathematical expressions having one or more variables are equal.

Linear Equation

Equations in which the powers of all the variables involved are one are called linear equations. The degree of a linear equation is always one.

General form of a Linear Equation in Two Variables

The general form of a linear equation in two variables is ax + by + c = 0, where a and b cannot be zero simultaneously.

Representing linear equations for a word problem

To represent a word problem as a linear equation

  • Identify unknown quantities and denote them by variables.
  • Represent the relationships between quantities in a mathematical form, replacing the unknowns with variables.

Solution of a Linear Equation in 2 variables

The solution of a linear equation in two variables is a pair of values, one for x and the other for y, which makes the two sides of the equation equal.
Eg: If 2x+y=4, then (0,4) is one of its solutions as it satisfies the equation. A linear equation in two variables has infinitely many solutions.

Geometrical Representation of a Linear Equation

Geometrically, a linear equation in two variables can be represented as a straight line.
2x – y + 1 = 0

⇒ y = 2x + 1

CBSE Class 10 Maths Notes Chapter 3 graph-1

Graph of y = 2



Plotting a Straight Line

The graph of a linear equation in two variables is a straight line. We plot the straight line as follows:

Pair of Linear Equations in Two Variables Class 10 Notes Chapter 3-1

Any additional points plotted in this manner will lie on the same line.

All about Lines

General form of a pair of linear equations in 2 variables

A pair of linear equations in two variables can be represented as follows

Pair of Linear Equations in Two Variables Class 10 Notes Chapter 3-2

The coefficients of x and y cannot be zero simultaneously for an equation.

Nature of 2 straight lines in a plane

For a pair of straight lines on a plane, there are three possibilities

i) They intersect at exactly one point

CBSE Class 10 Maths Notes Chapter 3 graph-2

pair of linear equations which intersect at a single point.

ii) They are parallel

CBSE Class 10 Maths Notes Chapter 3 graph-3

pair of linear equations which are parallel.

iii) They are coincident

CBSE Class 10 Maths Notes Chapter 3 graph-4

pair of linear equations which are coincident.

Graphical Solution

Representing pair of LE in 2 variables graphically

Graphically, a pair of linear equations in two variables can be represented by a pair of straight lines.

Graphical method of finding solution of a pair of Linear Equations

Graphical Method  of finding the solution to a pair of linear equations is as follows:

  • Plot both the equations (two straight lines)
  • Find the point of intersection of the lines.

The point of intersection is the solution.

Comparing the ratios of coefficients of a Linear Equation

Pair of Linear Equations in Two Variables Class 10 Notes Chapter 3-3

Algebraic Solution

Finding solution for consistent pair of Linear Equations

The solution of a pair of linear equations is of the form (x,y) which satisfies both the equations simultaneously. Solution for a consistent pair of linear equations can be found out using

i) Elimination method

ii) Substitution Method

iii) Cross-multiplication method

iv) Graphical method

Substitution Method of finding solution of a pair of Linear Equations

Substitution method:

y – 2x = 1

x + 2y = 12

(i) express one variable in terms of the other using one of the equations. In this case, y = 2x + 1.

(ii) substitute for this variable (y) in the second equation to get a linear equation in one variable, x. x + 2 × (2x + 1) = 12

⇒ 5 x + 2 = 12

(iii) Solve the linear equation in one variable to find the value of that variable.
5 x + 2 = 12
x = 2

(iv) Substitute this value in one of the equations to get the value of the other variable.

y = 2 × 2 + 1

⇒y = 5

So, (2,5) is the required solution of the pair of linear equations y – 2x = 1 and x + 2y = 12.

Elimination method of finding solution of a pair of Linear Equations

Elimination method
Consider x + 2y = 8 and 2x – 3y = 2

Step 1: Make the coefficients of any variable the same by multiplying the equations with constants. Multiplying the first equation by 2, we get,

2x + 4y = 16

Step 2: Add or subtract the equations to eliminate one variable, giving a single variable equation.
Subtract second equation from the previous equation
2x + 4y = 16
2x  – 3y =  2
–     +       –
0(x) + 7y =14
Step 3: Solve for one variable and substitute this in any equation to get the other variable.

y = 2,

x = 8 – 2 y

⇒ x = 8 – 4

⇒ x = 4

(4, 2) is the solution.

2. Coordination in Plants

Coordination in plants

Plants though do not have nervous system or muscles but they also respond towards the stimulus. For example, when we touch Mimosa pudica (touch-me-not plant), its leaves fold up and droop. There are two types of movements in plants -dependent on growth and independent of growth. When we touch the Mimosa pudica, its leaves fold up but no growth occurs, so it does not involve any growth. But movement of seedling is due to growth. Plants convey information from cell to cell through electrical-chemical means.

Hormone produced by plants


Movement due to Growth

The most common example of movement of growth are tendrils. Tendrils are sensitive to touch. When they come in contact with some object, the part of tendril away from the object will grow fast compare to the part of tendril which is in contact with the object. So it is a directional movement and it appears as if the plant is moving.
Directional movements of the plants are known as tropic movements. The movement can be towards the stimulus or away from the stimulus. Examples of some movements in plants are mentioned below-

 Many plant hormones are responsible for various kinds of movements in plants. Movements in plants can be divided into two main types:

1. Tropic movement
2. Nastic movement

1. Tropic Movement: The movements which are in a particular direction in relation to the stimulus are called tropic movements. Tropic movements happen as a result of growth of a plant part in a particular direction. There are four types of tropic movements.

(i) Geotropic movement: The growth in a plant part in response to the gravity is called geotropic movement. Roots usually show positive geotropic movement, i.e. they grow in the direction of the gravity. Stems usually show negative geotropic movement.
(ii) Phototropic Movement: The growth in a plant part in response to light is called phototropic movement. Stems usually show positive phototropic movement, while roots usually show negative phototropic movement. If a plant is kept in a container in which no sunlight reaches and a hole in the container allows some sunlight; the stem finally grows in the direction of the sunlight. This happens because of a higher rate of cell division in the part of stem which is away from the sunlight. As a result, the stem bends towards the light. The heightened rate of cell division is attained by increased secretion of the plant hormone auxin in the is away from sunlight.
(iii) Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water. This shows a positive hydrotropic movement.
(iv) Thigmotropism Movement: The growth in a plant part in response to touch is called thigmotropism movement. Such movements are seen in tendrils of climbers. The tendril grows in a way so as it can coil around a support. The differential rate of cell division in different parts of the tendril happens due to action of auxin.

2. Nastic Movement: The movement which do not depend on the direction from the stimulus acts are called nastic movement. For example, when someone touches the leaves of mimosa, the leaves droop. The drooping is independent of the direction from which the leaves are touched. Such movements usually happen because of changing water balance in the cells. When leaves of mimosa are touched, the cells in the leaves lose- water and become flaccid, resulting in drooping of leaves.

3. Animals Hormones


Hormones: These are the chemical messengers secreted in very small amounts by specialized tissues called ductless glands. They act on target tissues/organs usually away from their source. Endocrine System helps in control and coordination through chemical compounds called hormones.

Endocrine Glands 

They are the chemical messengers that are secreted in small quantities. There are two types of glands-endocrine glands and exocrine glands. Endocrine glands do not have ducts to carry the secretion and they produces the hormones.
Exocrine glands do have ducts to carry their secretion. List of different hormones secreted, and their function are given below-


2. Modes of Reproduction-Single Organisms

Types of Asexual Reproduction is Unicellular organism

(i) Binary Fission: 

  • Seen in bacteria, protozoa like Amoeba, Paramecium.
  • In these first pseudopodia withdrawn (karyokinesis) the nucleus of the parent cell divides and then the cytoplasm divides (cytokinesis) resulting in the formation of two daughter cells.
  •  It occurs during highly favourable conditions.
  •  The cell division can occur in any plane as in case of Amoeba.
  • However, organisms like Leishmania. (Cause Kala-azar), which have a whip like flagella at one end, binary fission occurs in a definite orientation in relation to the flagellum.

Cytokinesis: Division of cytoplasm.
Karyokinesis: Division of Nucleus.

(ii) Multiple Fission: 

  • Seen in Plasmodium, (a malarial parasite).  
  • During unfavorable conditions, the parent cell develops a thick resistant wall around itself forming a cyst.
  • Within the wall, the cytoplasm divides many times to form many plasmodia.
  • When conditions become favorable, the cyst wall breaks and the Plasmodium are released.

(iii) Budding: 

  • Seen in Yeast (a fungus). 
  •  The parent yeast cell develops a protrusion or an outgrowth at its upper end.
  •  The nucleus of the parent cell divides and one of them moves into the outgrowth which grows bigger and finally separates from the parent cell to lead an independent existence.
  • Very often if the conditions are highly favorable, a chain of buds is formed.

Types of Asexual Reproduction in Multicellular Organisms:

(i) Fragmentation: 

  • Seen in multicellular organisms which have a relatively simple body organisation like Spirogyra.
  • Spirogyra has a filamentous body. (If it breaks into smaller pieces or fragments). Each fragment has the capacity to form a new individual.
  • However, all multicellular organisms cannot show cell-by-cell division as cells from tissues which form organs.
  •  These organs are placed at definite positions in the body. Hence, they need to use more complex methods of reproduction.

(ii) Regeneration: 

  • It is the ability of organisms to develop their lost parts. 
  • Some organisms show have high regenerative capacity it is also a means of reproduction for example; Planaria.
  • Regeneration is carried out by specialized cells which re divide to form a mass of cells from which different cells undergo changes to become different cell types and tissues.
  • These changes occur in an organized sequence known as development.

(iii) Budding: 

  • Seen in Hydra.  
  • Parent Hydra develops a bud at its lower end.
  • This grows in size and finally breaks off to live independently.

(iv) Spore Formation: 

  • Seen in Rhizopus (a fungus).   
  • Rhizopus body is made up of thread-like structures called hyphae.
  • The erect hyphae bear sporangia inside which reproductive structures called spores are formed.
  •  Spores are asexually reproducing bodies having a thick protective wall.
  • They are produced during unfavourable times and help to tide over the unfavourable environmental conditions.
  • When the spores fall on a suitable medium, each one forms a new individual.

(v) Vegetative Propagation: 
Method by which plants reproduce by their vegetative parts such as roots, stems, and leaves.
Types of Vegetative Propagation: It is two types

  • Natural vegetative propagation.
  • Artificial vegetative propagation (Tissue culture).

Mint reproduces naturally by roots. Sugarcane, jasmine by stems and Bryophyllum by leaves. In bryophyllum, buds are produced in the notches along the leaf margins and when they fall on the soil, they develop into new plants.
Importance of Vegetative Propagation

  • Plants can bear flowers and fruits earlier.
  • Plants which have lost the ability to produce viable seeds can also reproduce by vegetative propagation.
  • All plants are genetically almost similar to the parent plant.
  • Seedless varieties can be obtained.
  • The property of vegetative propagation is used by horticulturists in developing methods like layering, grafting to grow many plants like sugarcane, roses, or grapes.

3. Sexual Reproduction

Sexual Reproduction: 

  • Sexual reproduction occur in plants & in human beings. The mode of reproduction that takes place with the involvement of two individuals of two different sexes i.e. male and female.
  • During sexual reproduction, male organism having male sex organs produces male gametes i.e. sperms which are small and motile and the female organism having female sex organs produces ova which are generally large and store food.
  • Male and female gametes fuse to form a zygote that grows into a new organism.

Significance of Sexual Reproduction:

  • Sexual reproduction involves DNA as well as cellular apparatus of two different organisms which promotes diversity of characters in the offspring.
  • Since gametes are derived from two different organisms, it results in a new combination of genes which increases the chances of genetic variations.
  • Sexual reproduction results in the origin of new species.
  • Sexual reproduction involves division in the sex organs that reduces the DNA matter to half so that the zygote formed after fusion has the same amount of DNA as the parents it maintains DNA in a species.

Limitation of Sexual Reproduction: Sexual reproduction involves the process of combining DNA from two different organisms which may bring some undesirable features also.
Sexual reproduction in flowering plants

  • The reproductive parts are present in the flower.
  • The parts of the flower are sepals, petals, stamens and carpels.
  • Sepals are green structures that protect the inner parts when the flower is in bud stage.
  • Petals are colourful and attract the insects for pollination.
  • Stamens are male reproductive parts and produce pollen grains that contain male gametes. Each stamen has two parts—
  • Filament i.e. stalk and Anther i.e. swollen top part which has large number of pollen grains.

The carpel is the female reproductive part and produces ovules that contain female gametes. It has three parts—Stigma which is top sticky part and receives pollen grains during pollination. Style which is the middle long part and ovary which is the swollen part and contains ovules. Each ovule has an egg cell i.e. female gamete.

The flowers may be bisexual i.e. having both stamens and carpels for example; Mustard China Rose (Hibiscus).The flower may be unisexual i.e. paving either stamens or carpels for example; Papaya, Watermelon.
Pollination: The process of transfer of pollen grains from an anther to the stigma of the flower is pollination. Two types of pollination are:
(i) Self-pollination: The transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same plant.
(ii) Cross-pollination: The transfer of pollen grains from the anther to the stigma of another flower or another flower of a different plant of the same species. It generally takes place with the help of some agents like insects, birds, wind and water.

Fertilization: Fertilization is the process of fusion of male and female gamete to form a zygote during sexual reproduction. Pollination is followed by fertilisation in plants.

The events are as follows:
Pollen grains land on the stigma of the ovary.
Pollen tubes grow out of the pollen grains, travel through the style and reach the ovary, through micropyle.
Pollen tube has two male germ cells. Each ovule has two polar nuclei and a female germ cell (egg).

Pollen tube releases two male germ cells inside the ovule, one of them fuses with female germ cell and forms a zygote which grows into the baby plant i.e. embryo, the fusion is known as syngamy.
The other male germ cell fuses with two polar nuclei, the process is known as triple fusion. So in flowering plants two fusions take place during fertilisation. It is called double fertilisation.
Post-fertilisation changes: After fertilisation the following changes takes place in the flower.
Zygote divides several times and forms an embryo inside the ovule.

  • The ovule develops a tough coat and changes into the seed.
  • The ovary grows rapidly and ripens to form a fruit.
  • Petals, sepals, stamens, style and stigma shrivel and fall off.

Seed and its parts: The advantage of seed is that it protects the future plant i.e. embryo.
Seed has two parts: Cotyledons and Embryo Cotyledons store food for the future plant.
Embryo has two parts: Plumule and radicle. Plumule develops into shoot and radicle develops into root.
The process of development of a seedling from the embryo under appropriate conditions is known as germination.

Reproduction in Human Being: 

  • Human beings show sexual reproduction.
  •  Male parent produces male gametes called sperms.
  • Female parent produces female gametes called ova.
  • Sperms have tail and are therefore, motile. They are produced in large numbers in the testes.
  •  Ovum is bigger, non-motile and only one ovary produces one ovum in one month.
  • There is no food stored in the sperms whereas ova contain stored food.
  • Both the gametes are microscopic unicellular and have half the number of chromosomes as compared to the body cells.
  • Human beings become reproductively active from the onset of puberty.
  • Puberty is the period during adolescence when the rate of general body growth begins to slow down and reproductive tissues begin to mature.
  • Onset of puberty in human males is between 11 to 13 yrs of age, while in human females is between 10 to 12 yrs. of age.
  •  Puberty is associated with many physical, mental, emotional and psychological changes in boys and girls which occur slowly over a period of time. These are called secondary sexual characters.
  • For instance thick dark hair start growing in new parts of the body such as arm pits and genital area between the thighs. Thinner hair appear on legs, arms and face. Skin becomes oily and pimples may appear on the face. Individuals become more conscious of their bodies become more independent, more aggressive etc.
  • In case of boys, beard and moustache start appearing, voice begins to crack, reproductive organs develop and start producing releasing sperms.
  • In case of girls, breast size begins to increase, skin of the nipples darkens, menstruation starts.
  • The act of mating between the male and female partner is termed as copulation.

2. Evolution


 The sequence of gradual changes that take place in an organism over a million years and leads to the formation of new species is known as evolution.
J.B. Lamarck was the first scientist who gave the theory of evolution. He gave the theory of inheritance of acquired characters. Later on, Charles Darwin came and gave the theory of natural selection or Darwinism. According to his theory, evolution occurs through natural selection.

Theory of Lamarckism

This theory is also known as the “Theory of inheritance of acquired characters”. Lamarckism is based on the following postulates-

  • Living organisms tend to increase in size.
  • New needs lead to the formation of new organs.
  • Continued use of a particular organ makes it more developed and disuse of an organ leads to its degeneration.
  • New characters are acquired by individuals during their lifetime.

Theory of Darwin
Darwin's theory was also known as the “Theory of Natural selection”.
Postulates of Darwin Theory

  • Speciation (formation of species) - Useful variations from generation to generation gives rise to the formation of new species.
  • The struggle of existence due to the multiplication of organisms and limited food and space, there exists competition among the organisms.
  • Survival of the fittest or Natural selection Nature selects those characteristics or organisms that are useful and are best adapted to the prevailing conditions. “For example, industrial melanism observed in peppered moths in Britain”

The origin of new species from already existing species is known as speciation. Speciation can take place through-

  • Gene flow can lead to speciation. It is a transfer of genetic variation from one population to another
  • Random change in allele frequency known as genetic drift can also lead to speciation.
  • Natural selection is another reason through which speciation can take place
  • Geographical barriers such as mountains, rivers can also lead to speciation. This is known as geographical isolation. 

3. Evolution and Classification

Evolution and classification

Evolution and classification are linked to each other. There is different evidence of evolution given-

  • Homologous organs are the organs evolved from the same ancestors but they have different functions. For example, the forelimb of a horse and the wings of a bat. The Flippers of the whale, the human hand are other examples of homologous organs.

Examples of homologous organs

  • Analogous organs are the organs that arise from different ancestors but have the same function. For example, wings of bats, wings of birds, wings of insects etc.

Examples of analogous organs 

  • Paleontological (fossil) evidence was also given for evolution. The dead remains of the organisms are known as fossils. For example, Archaeopteryx possesses features of both reptiles and birds. This concludes that birds evolved from reptiles. There are two methods for finding the age of the fossils- one is carbon dating and the other is by digging. In the digging method, the deeper the fossil is, the older it is. Biogenetic law states that stages of development of an animal embryo are the same as adult animal stages. 
  • Vestigial organs are rudimentary in nature. They have lost their function through evolution. For example, appendix in humans, muscles of ears, wisdom tooth etc.

Evolution by Stages
Evolution can take place in stages also. For example, the evolution of eyes. Flatworms have rudimentary eyes, whereas insects possess compound eyes. In the last humans have binocular vision.
The evolution of feathers is also an example of evolution by stages. For example, dinosaurs have feathers but are unable to fly. But later on, birds used feathers for flying.

Molecular Phylogeny
It is also evidence for evolution. According to this, changes in DNA during reproduction are the basic events of evolution. Organisms that are related to each other most distantly will have greater differences in their DNA.

Evolution by Artificial Selection
Artificial selection selects special phenotypic characters to produce organisms with enhanced characteristics. For example, plants that are disease or insect resistant. Artificial selection can be used to produce different cabbage varieties such as broccoli, cauliflower, red cabbage etc.

Human Evolution
Excavating fossils, time dating and determination of DNA sequences are used to study human evolutionary relationships. The study of human evolution indicates that all of us belong to a single species that evolved in Africa and then spread across the world in stages.

The stages of human development are as follows-


4. Reproduction in Human Beings

Male Reproductive System: Male reproductive system consists of the following components

  • 1 pair of testes
  • A system of ducts
  • Epididymis
  • Vas deferens or the sperm duct
  • Urethra
  • A system of glands
  • Seminal vesicles
  • Prostate gland
  • Cowper’s gland
  • A copulatory organ called a penis.

One pair of testes are present in a bag-like structure called scrotum. which lies outside the abdominal cavity, hence they are extra abdominal in position. This is so because the testes have to be maintained at 1-3 degree lesser temperature than the body in order to produce functional sperms. 

Functions of testes

  • To produce male gametes i.e. the sperms.
  • To produce a male reproductive hormone called testosterone which is responsible for producing sperms as well as secondary sexual characteristics in males.

Attached to each testis is a highly coiled tube called epididymis. The sperms are stored here and they mature in the epididymis.
Each epididymis leads into the sperm duct or the vas-deferens. Each vas-deferens rises up and enters into the abdominal cavity. It unites with the duct coming from the urinary bladder to form a common duct called urethra which passes through the penis and opens to the outside. Along the way the ducts of the three glands also open and pour their secretions into the vas deferens.

Function of the vas-deferens: It is meant for the passage of the sperms in the male body.
Functions of the glands: They produce different secretions which provide nutrition as well as medium for locomotion to the sperms.
The secretions of the three glands along with the sperms is known as semen.

Function of the urethra: It is the common passage for both semen and urine from the body to the outside.
Penis: It is the organ which is used to introduce semen into the female body. It is richly supplied with blood vessels.
Female Reproductive System: It consists of the following components

  • 1 pair of ovaries
  • 1 pair of fallopian tubes or oviducts
  • A uterus/womb
  • A vagina/birth canal.

Each ovary is almond shaped and present inside the abdominal cavity. At the time of birth each girl child already contains thousands of immature ova. These ova start maturing only from the time of puberty. Only one ovum is produced by one ovary in one month and each ovary releases an ovum in alternate months. The release of an ovum from the ovary into the abdominal cavity is known as ovulation.
Functions of ovary

  • To produce and release ova
  • To produce female reproductive hormones: estrogen and progesterone.

There are two fallopian tubes. The end lying close to the ovary has finger like structures called fimbriae. The two fallopian tubes unite to form an elastic bag like structure called uterus.
Function of the fallopian tubes: It is the site of fertilization between the male and the female gametes and formation of the zygote early embryo.
The inner lining of the uterus is richly supplied with blood vessels and is known as endometrium. The narrow end of the uterus is called cervix.

Function of the uterus: The embryo formed in the fallopian tube comes down and gets attached to the endometrium (implantation) and develops for the next nine months till the baby is delivered.
Vagina: The uterus opens into the vagina through the cervix. The vagina is a muscular tube through which the baby is delivered at the end of nine months. It also serves as the canal for receiving the semen at the time of copulation.
The semen is discharged into the vaginal tract during copulation. The sperms travel upwards and reach the fallopian tube where one sperm fuses with the ovum to form the zygote. The zygote divides and redivides as it descends into the uterus and the embryo gets implanted in the endometrium. The endometrium thickens so as to receive the embryo.
The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta, which is a disk-like structure embeded in the uterine wall. It contains finger-like villi on the embryo side, while on the mother’s side blood spaces surround the villi. Villi provides a large surface area for glucose and oxygen to pass from the mother to the developing embryo and the wastes to pass from the embryo to the mother through the placenta. When the embryo starts resembling a human is formed, it is termed as a foetus. The foetus continues to develop inside the uterus for almost nine months after which the baby is delivered as a result of rhythmic contractions of the uterine muscles.

  • It is the loss of blood, mucous along with the unfertilized ovum and the ruptured cells and tissues of the endometrium through the vagina of the female.
  •  It is a 28-day cycle which occurs in every reproductively active female (from puberty).
  • The flow of blood continues for 2 to 8 days.
  • If the ovum does not get fertilized, then the endometrium starts sloughing off and there is loss of blood and mucous etc. through the vagina.
  •  In case the ovum gets fertilized, then the endometrium becomes thick and spongy for nourishing the embryo and hence menstruation does not occur.
  • A lady with a developing embryo in her womb is termed as pregnant.
  • The beginning of menstruation at puberty is known as menarche.
  •  The stoppage of menstruation when the woman is 45-55 years of age is called menopause.

Reproductive Health: Reproductive health means total well-being in all aspects of reproduction, i.e., physical, emotional, social and behavioural.

  • Sexually transmitted diseases and birth control.
  • A number of diseases occur as a result of sexual intercourse if one of the partners is infected. These are known as sexually transmitted diseases (STD’s).
  • They can be caused by bacteria for example; syphilis, gonorrhoea; or caused by a virus for example; HIV-AIDS, warts etc.
  •  The transmission of these diseases can be avoided by using birth control measures such as wearing a condom during the sexual act.

Birth control measures: They can be mechanical, chemical and surgical.
Mechanical methods: These are used to prevent the passage of semen to the fallopian tube:
(i) Use of condoms: Condoms are thin rubber tubes worn over the penis before sexual intercourse. The semen gets collected in this and is not discharged into the vagina.
(ii) Diaphragm: It is a thin rubber fixed over a flexible metal ring which is fitted over the cervix in a woman’s body by a doctor.
(iii) Intra Uterine Contraceptive Device (IUCD) or loop: It is inserted in the uterus and its insertion causes certain secretion which prevents the implantation of the embryo in the uterine wall.
Both methods (ii) and (iii) cause side effects.

Chemical methods

  • Use of spermicides: These are strong sperm-killing chemicals available in the form of creams, jellies etc. which are injected into the vagina just before copulation.
  • Oral contraceptive pills: These are hormonal pills which prevent ovulation but do not stop menstruation.

Surgical methods

  • Vasectomy: It involves cutting and ligating the vas deferens in males.
  • Tubectomy: It involves cutting and ligating Reproductive organs the fallopian tubes in females.
  • Medical termination of pregnancy (MTP) or abortions is carried out to eliminate the developing embryo. This practice can, however, be misused to carry out female foeticide which involves the killing of the female foetus. It should be avoided at all cost as it disturbs the male-female ratio in a population.

Contraception: It is the avoidance of pregnancy through different methods—Natural methods, Barrier method, Oral contraceptives, Surgical methods.
Advantages of contraception: Help in birth control, prevent sexually transmitted diseases, prevent unwanted pregnancies, keep population explosion in check.

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