BIOLOGY

INDEX
S NO NAME OF THE CHAPTER PAGE
1 LIFE PROCESSES 1-26
2 CONTROL AND COORDINATION 27-44
3 HOW DO ORGANISMS REPRODUCE 45-72
4 HEREDITY 73-80
5 OUR ENVIRONMENT 81-92
6 QUESTIONS AND ANSWERS 93-118
 1. LIFE PROCESSES
Def: The basic functions performed by living organisms to maintain their life.

Basic life processes common to all the living organisms:

 Nutrition: The process that involves in taking of food inside the body and converting
it into smaller molecules which can be absorbed by the body.
 Respiration: The process which releases energy from the food absorbed by the body.
 Transport: The process in which a substance absorbed or made in one part of the body
is moved to other parts of the body.
 Excretion: The process in which the waste materials produced in the cells of the body
are removed from the body.
 Control and coordination (or response to stimuli): The process which helps the living
organisms to survive in the changing environment around them.
 Growth: The process of that involves in change from a small organism to a big
organism (or an adult organism).
 Movement: The process by which the organism either moves from one place to
another or moves its body parts while remaining at the same place.
 Reproduction: The process of that involves in making of more organisms from the
existing ones, so that organisms could live on this earth for ever

ENERGY:

All the living organisms need energy to perform various life processes. The energy required
by an organism comes from the food that the organism eats.

Food is a kind of fuel which provides energy to all the living organisms.

The living organisms use the chemical energy for carrying out various life processes. They get
this chemical energy from food through chemical reactions

NUTRITION:

Def: The process of taking in food (consuming food) and utilising it.

Nutrient:

A substance which an organism obtains from its surroundings and uses it as a source of energy
or for the biosynthesis of its body constituents (like tissues and organs).

 Carbohydrates and fats are the nutrients used as a source of energy and proteins and
mineral salts are used for the biosynthesis of its body constituents like skin, blood, etc.
 Carbohydrates, fats and proteins are macronutrients and Vitamins and minerals are
micronutrients.
 Organic nutrients: The nutrients that contain carbon in their structural makeup
o carbohydrates, lipids, proteins and vitamins
 Inorganic nutrients: The nutrients that do not contain carbon.
o Minerals
 MODES OF NUTRITION

The methods of procuring food or obtaining food by an organism.

Depending on the mode of obtaining food, all the organisms can be classified into:

AUTOTROPHIC MODE OF NUTRITION:

The mode of nutrition in which an organism makes (or synthesizes) its own food from the
simple inorganic materials like carbon dioxide and water present in the surroundings (with
the help of sunlight energy).

 Eg: Green plants, blue-green algae and Autotrophic bacteria

Autotrophs: The organisms which can make their own food from carbon dioxide and water.

Type of autotrophs:

 Photoautotrophs: They harvest energy from light to produce organic matter.

 Chemoautotrophs: They use energy from inorganic reactions in the environment to
drive the creation of organic matter

HETEROTROPHIC MODE OF NUTRITION:

The mode of nutrition in which an organism cannot make (or synthesize) its own food from
simple inorganic materials like carbon dioxide and water, and depends on other organisms
for its food.

 Eg: All the animals, most bacteria and fungi

These animals are called heterotroph heterotrophic animals

Types of Heterotrophic nutrition

 Holozoic Nutrition: The nutrition in which an organism takes the complex organic food
materials into its body by the process of ingestion, the ingested food is digested and
then absorbed into the body cells of the organism
Eg: Most of the animals
 Saprophytic Nutrition: The nutrition in which an organism obtains its food from
decaying organic matter of dead plants, dead animals and rotten organic matter
(rotten bread).
Eg: Fungi (like bread moulds, mushrooms, yeast), and many bacteria

 Parasitic nutrition: The nutrition in which an organism derives its food from the body
of another living organism (called its host) without killing it
Eg: Several fungi, few plants like Cuscuta (amarbel) and some micro-organism
like Plasmodium and roundworms.
 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. Chlorophyll is present in the green coloured bodies called ‘chloroplasts

Photosynthesis: The process by which green plants make their own food (like glucose) from
carbon dioxide and water by using sunlight energy in the presence of chlorophyll.

Steps of photosynthesis:

 Sunlight activates chlorophyll; which leads to splitting of water molecule.

 The hydrogen released by splitting of water molecule is utilized for reduction of carbon
dioxide to produce carbohydrates.
 Oxygen is the by-product of photosynthesis.
 Carbohydrate is subsequently converted into starch and is stored in leaves and other
storage parts.
 The splitting of water molecules is part of the light reaction.
 Other steps are part of the dark reaction during photosynthesis.
Raw materials for photosynthesis

 Sunlight – chlorophyll, the green pigment present in green plants, traps solar energy.
 Water – roots absorb water from the soil provided by irrigation or even rains.
 Carbon dioxide – through gaseous exchange carried out by stomata.

Significance of photosynthesis:

 It is the main way through which the solar energy is made available for different living
beings.
 Green plants are the main producers of food in the ecosystem.
 All other organisms directly or indirectly depend on green plants for food.
 It also helps in maintaining the balance of carbon dioxide and oxygen in the air.

Stomata:

 These are tiny pores present on the surface of the leaves, stems and other parts of
plant.
 It plays an important role in gaseous exchange and photosynthesis.
 It facilitate carbon dioxide uptake and release of oxygen during the process of
photosynthesis.
 It helps in transpiration and removal of excess water in the form of water vapour.
 Stomatal closure at night prevents water from escaping through pores.
 It maintains the moisture balance according to weather by opening and closing.
 The mechanism of stomatal opening and closure:
o The opening and closing of the stroma is a function of the guard cells, which
depend on the turgor pressure, caused by the osmotic flow of water in the
guard cells.
o When the guard cells are turgid, they expand resulting in the opening of
stomata.
o When the guard cells lose water, they become flaccid leading to stomatal
closure.
o Stomata normally open when the light strikes the leaf and close during the
night.
 ANIMAL NUTRITION

Heterotrophic Nutrition: When an organism takes food from another organism

All the animals can be divided into three groups on the basis of their food habits (or eating
habits).

STEPS OF HOLOZOIC NUTRITION

Ingestion: The process of taking in the food is called ingestion.

Digestion: The process in which the food containing large, insoluble molecules is broken down
into small, water soluble molecules (which can be absorbed by the body)

Absorption: The process of absorption of digested food is called absorption.

Assimilation: The process of utilization of digested food; for energy and for growth and repair
is called assimilation.

Egestion: The process of removing undigested food from the body is called egestion.

NUTRITION IN AMOEBA

 Amoeba is a unicellular animal which follows holozoic mode of nutrition.

 The cell membrane of amoeba keeps on protruding into pseudopodia.
 Amoeba surrounds a food particle with pseudopodia and makes a food vacuole.
 The food vacuole contains the food particle and water.
 Digestive enzymes are secreted in the food vacuole and digestion takes place.
 After that, digested food is absorbed from the food vacuole.
 Finally, the food vacuole moves near the cell membrane and undigested food is
expelled out.

NUTRITION IN PARAMECIUM,

 It is also a unicellular organism, the cell has a definite shape and food is taken in at a
specific spot.
 Food is moved to this spot by the movement of cilia which cover entire surface of the
cell.
 STRUCTURE OF THE HUMAN DIGESTIVE SYSTEM

MOUTH OR BUCCAL CAVITY:

 The mouth has teeth and tongue.

 Salivary glands are also present in the mouth.
 The tongue has gustatory receptors which perceive the sense of taste.
 Tongue helps in turning over the food, so that saliva can be properly mixed in it.

Teeth:

 They help in breaking down the food into smaller particles so that swallowing of
food becomes easier.
 There are four types of teeth in human beings.
 The incisor teeth are used for cutting the food.
 The canine teeth are used for tearing the food and for cracking hard substances.
 The premolars are used for coarse grinding of food.
 The molars are used for fine grinding of food.

Salivary glands:

 They secrete saliva.

 Saliva makes the food slippery which makes it easy to swallow the food.
 Saliva also contains the enzyme salivary amylase or ptyalin. (biological catalysts)
 Salivary amylase digests starch and converts it into sucrose
OESOPHAGUS:

 From the mouth, the food is taken to the stomach through the food-pipe or
oesophagus

STOMACH:

 Stomach is a bag-like organ.

 Highly muscular walls of the stomach help in churning the food.
 The walls of stomach secrete hydrochloric acid, pepsin and mucus.
 Hydrochloric acid kills the germs which may be present in food.
 Moreover, it makes the medium inside stomach as acidic.
 Hydrochloric acid creates an acidic medium which facilitates action of the enzyme
pepsin.
 The enzyme pepsin: It does partial digestion of protein.
 The mucus: Saves the inner lining of stomach from getting damaged from hydrochloric
acid.
 The exit of food from the stomach is regulated by a sphincter muscle which releases
it in small amounts into the small intestine

SMALL INTESTINE:

 It is longest part of the alimentary canal and highly coiled tube-like structure.
(Herbivores eating grass need a longer small intestine to allow the cellulose to be
digested. Meat is easier to digest, hence carnivores like tigers have a shorter small
intestine)
 The small intestine is longer than the large intestine but its lumen is smaller than that
of the large intestine.
 Complete digestion of carbohydrates, proteins and fats by liver and pancreatic
enzymes
 The small intestine is divided into three parts, viz. duodenum, jejunum and ileum.

Liver:

 Liver is the largest organ in the human body.

 Liver manufactures bile, which gets stored in gall bladder.
 From the gall bladder, bile is released as and when required.
 The acidic food from stomach is made into alkaline by bile for pancreatic enzymes
to act.

Pancreas:

 Pancreas is situated below the stomach.

 It secretes pancreatic juice which contains many digestive enzymes. (Lipase,
Trypsin and chymotrypsin)
 Bile and pancreatic juice go to the duodenum through a hepato-pancreatic duct.
  Fats are present in the intestine in the form of large globules which makes it
difficult for enzymes to act on them.
 Bile salts break them down into smaller globules increasing the efficiency of
enzyme action. This process is called emulsification of fat.
 After that, the enzyme lipase digests fat into fatty acids and glycerol.
 Trypsin and chymotrypsin are enzymes which digest protein into amino acids.
 The enzymes present in small intestine convert the proteins to amino acids,
complex carbohydrates into glucose and fats into fatty acids and glycerol.
 A major part of digestion takes place in the duodenum.

Jejunum:

 No digestion takes place in jejunum.

 The inner wall in the ileum is projected into numerous finger-like structures; called
villi.
 Villi increase surface area inside the ileum so that optimum absorption can take
place.
 The villi are richly supplied with blood vessels which take the absorbed food to
each cell of the body, where it is utilised for obtaining energy, building up new
tissues and the repair of old tissues.
 Moreover, villi also reduce the lumen of the ileum so that food can stay for longer
duration in it for optimum absorption.
 Digested food is absorbed by villi.

LARGE INTESTINE:

 Large intestine is smaller than small intestine.

 Undigested food goes into the large intestine.
 Some water and salt are absorbed by the walls of the large intestine.
 After that, the undigested food goes to the rectum; from where it is expelled out
through the anus.
 The act of expelling the faeces is called egestion or defecation
 The exit of this waste material is regulated by the anal sphincter
DENTAL CARIES:

 The hard, outer covering of a tooth is called enamel. Tooth enamel is the hardest
material in our body. It is harder than even bones.
 The part of tooth below enamel is called dentine, which is similar to bone.
 Inside the dentine is pulp cavity which contains nerves and blood vessels.
 Dental caries: The formation of small cavities (or holes) in the teeth due to the action
of acid-forming bacteria and improper dental care.
 It begins when bacteria acting on sugars produce acids that softens or demineralises
the enamel.
 Masses of bacterial cells together with food particles stick to the teeth to form dental
plaque.
 Saliva cannot reach the tooth surface to neutralise the acid as plaque covers the teeth.
 Brushing the teeth after eating removes the plaque before the bacteria produce acids.
If untreated, microorganisms may invade the pulp, causing inflammation and infection
 RESPIRATION

The process by which a living being utilizes the food to get energy is called respiration.

Respiration is an oxidation reaction in which carbohydrate is oxidized to produce energy.

Mitochondrion is the site of respiration and the energy released is stored in the form of ATP
(Adenosine triphosphate).

ATP is stored in mitochondria and is released as per need.

STEPS OF RESPIRATION:

Breaking down glucose into pyruvate:

 This step happens in the cytoplasm.

 Glucose molecule of 6 carbon atoms, is broken down into pyruvic acid of 3 carbon
atoms.

Fate of Pyruvic Acid:

 Further breaking down of pyruvic acid takes place in mitochondria and the molecules
formed depend on the type of respiration in a particular organism.
 Respiration is of two types, viz. aerobic respiration and anaerobic respiration.

TYPES OF RESPIRATION:

Aerobic Respiration:

 This type of respiration happens in the presence of oxygen.

 Pyruvic acid is converted into carbon dioxide. Energy is released and water molecule
is also formed at the end of this process.

Anaerobic Respiration:

 This type of respiration happens in the absence of oxygen.

 Pyruvic acid is either converted into ethyl alcohol or lactic acid.
 Ethyl alcohol is usually formed in case of anaerobic respiration in microbes, like yeast
or bacteria.
 Lactic acid is formed in some microbes as well as in the muscle cells
ATP (Adenosine triphosphate):

 It is the energy currency for most cellular processes.

 The energy released during the process of respiration is used to make an ATP molecule
from ADP and inorganic phosphate.
 Endothermic processes in the cell then use this ATP to drive the reactions.
 When the terminal phosphate linkage in ATP is broken using water, the energy
equivalent to 30.5 kJ/mol is released.
 ATP can be used in the cells for the contraction of muscles, protein synthesis,
conduction of nervous impulses and many other activities.

Pain in Leg Muscles on Running:

 When someone runs too fast, he may experience a throbbing pain in the leg muscles.
 This happens because of anaerobic respiration taking place in the muscles.
 During running, the energy demand from the muscle cells increases.
 This is compensated by anaerobic respiration and lactic acid is formed in the process.
 The deposition of lactic acid causes the pain the leg muscles. The pain subsides after
taking rest for some time.

RESPIRATION IN PLANTS

 The plants get the energy by the process of respiration.

 Plants also use oxygen of air for respiration and release carbon dioxide.
 Thus, the respiration in plants also involves the exchange of oxygen and carbon
dioxide.
 So, oxygen and carbon dioxide are called respiratory gases.
 The exchange of respiratory gases in the leaves takes place by the process of diffusion
through stomata.
 Oxygen from air diffuses into a leaf through stomata and reaches all the cells where it
is used in respiration.
 The carbon dioxide produced during respiration diffuses out from the leaf into the air
through the same stomata.
 During daytime, when photosynthesis occurs, the net gas exchange in leaves during
daytime is: O2 diffuses out & CO2 diffuses in.
 At night time, when no photosynthesis occurs and oxygen from air diffuses into leaves
to carry out respiration, the net gas exchange in leaves at night is: O2 diffuses in & CO2
diffuses out.
 RESPIRATION IN ANIMALS

In aerobic respiration, organisms need a continuous supply of oxygen, and carbon dioxide
produced during the process needs to be removed from the body.

Different animals have different modes of respiration.

 In simple unicellular animals like Amoeba, respiration takes place by the simple
diffusion of gases through the cell membrane.
 Most of the animals have, however, specific organs for respiration.
 The animals like earthworms which live in the soil use their skin to absorb oxygen from
air and remove carbon dioxide. So, the respiratory organ in the earthworm is the skin.
 The aquatic animals like fish, prawns and mussels have gills as the respiratory organs
which extract oxygen dissolved in water and take away carbon dioxide from the body.
 In the insects like grasshopper, cockroach, housefly and a mosquito, the tiny holes
called spiracles on their body and the air tubes called tracheae are the respiratory
organs
 Terrestrial organisms use the oxygen in the atmosphere for respiration. The
respiratory organs of man (humans), birds, lizard, dog, and frog, etc., are the lungs.
(Frogs, however, breathe both by lungs and skin).

RESPIRATION IN HUMANS

The human respiratory system is composed of a pair of lungs.

These are attached to a system of tubes which open on the outside through the nostrils.

The lungs lie in the chest cavity or thoracic cavity which is separated from abdominal cavity
by a muscular partition called diaphragm.

The lungs are covered by two thin membranes called pleura and enclosed in a rib cage made
of bones called ribs.
Following are the main structures in the human respiratory system:

Nostrils:

 There two nostrils which converge to form a nasal passage.

 The inner lining of the nostrils is lined by hairs and remains wet due to mucus
secretion.
 The mucus and the hairs help in filtering the dust particles out from inhaled air.
 Further, air is warmed up when it enters the nasal passage.

Pharynx:

 It is a tube-like structure which continues after the nasal passage.

Larynx:

 This part comes after the pharynx. This is also called the voice box.

Trachea:

 This is composed of rings of cartilage and known as windpipe.

 Cartilaginous rings prevent the collapse of trachea in the absence of air.

Bronchi:

 A pair of bronchi comes out from the trachea; with one bronchus going to each lung.

Bronchioles:

 A bronchus divides into branches and sub-branches; inside the lung.

Alveoli:

 These are air-sacs at the end of bronchioles which are balloon-like structures.
 Alveolus is composed of a very thin membrane and is the place where blood capillaries
open.
 Here oxygen mixes with the blood and carbon dioxide exits from the blood.
 This exchange of gases in alveoli takes place due to pressure differential.
Breathing Mechanism:

 The breathing mechanism of lungs is controlled by the diaphragm and the intercostals
muscles.
 Diaphragm is a membrane which separates the thoracic chamber from the abdominal
cavity.
 When diaphragm moves down, the lungs expand and air is inhaled.
 When diaphragm moves up, the lungs contract and air is exhaled.
 The average breathing rate in an adult man at rest is about 15 to 18 times per minute
 Rapid breathing supplies more oxygen to body cells for producing more energy
required for doing physical exercise

Exchange and transport of gases:

 Haemoglobin transports oxygen molecule to all the body cells for cellular respiration.
 The haemoglobin pigment present in the blood gets attached to four O 2 molecules
that are obtained from breathing.
 It thus forms oxyhaemoglobin and the blood becomes oxygenated.
 This oxygenated blood is then distributed to all the body cells by the heart.
 After giving away O2 to the body cells, blood takes away CO2 which is the end product
of cellular respiration.
 Now the blood becomes de-oxygenated.
 Since haemoglobin pigment has less affinity for CO2, CO2 is mainly transported in the
dissolved form.
 This de-oxygenated blood gives CO2 to lung alveoli and takes O2 in return.
How are the lungs designed in human beings to maximize the area for exchange of gases?

 If the alveolar surface were spread out, it would cover about 80 m 2.

 Each lung contains 300-350 million alveoli.
 These numerous alveoli increase the surface area for gaseous exchange making the
process of respiration more efficient

Tobacco use:

 Using tobacco directly or any product of tobacco in the form of cigar, cigarettes, bidis,
hookah, gutkha, etc., is harmful.
 Use of tobacco most commonly affects the tongue, lungs, heart and liver.
 Smokeless tobacco is also a major risk factor for heart attacks, strokes, pulmonary
diseases and several forms of cancers.
 There is a high incidence of oral cancer in India due to the chewing of tobacco in the
form of gutkha.
 Lung cancer is one of common causes of deaths in the world.
 The upper part of respiratory tract is provided with small hair-like structures
called cilia.
 These cilia help to remove germs, dust and other harmful particles from
inhaled air.
 Smoking destroys this hair due to which germs, dust, smoke and other harmful
chemicals enter lungs and cause infection, cough and even lung cancer.

TRANSPORTATION

Transport is a life process in which a substance absorbed (or made) in one part of the body of
an organism is carried to other parts of its body.

TRANSPORTATION IN HUMAN BEINGS

Circulatory System:

 The circulatory system is responsible for transport of various substances in human

beings.
 It is composed of the heart, arteries, veins and blood capillaries.
 Blood plays the role of the carrier of substances.

HEART

 Heart is a muscular organ; which is composed of cardiac muscles.

 Its size is that of adult’s fist.
 The heart is a pumping organ which pumps the blood.
 As both oxygen and carbon dioxide have to be transported by the blood, the heart has
different chambers to prevent the oxygen-rich blood from mixing with the blood
containing carbon dioxide
 It has four chambers, viz. right auricle or atrium, right ventricle, left auricle and left
ventricle.
 The carbon dioxide-rich blood reaches right atrium then to right ventricle then it is
sent to the lungs for the carbon dioxide to be removed, and the oxygenated blood
from the lungs reaches left atrium then to left ventricle of heart.
  When ever the atrium or ventricle relaxes it dilates and receives blood and when it
contracts it pump blood into next chamber.
 This oxygen-rich blood is then pumped to the rest of the body by left ventricle
 Systole: Contraction of cardiac muscles is called systole.
 Diastole: Relaxation of cardiac muscles is called diastole.

Arteries:

 These are thick-walled blood vessels which carry oxygenated blood from the heart to
different organs.
 Pulmonary arteries are exceptions because they carry deoxygenated blood from the
heart to lungs, where oxygenation of blood takes place.

Veins:

 These are thin-walled blood vessels which carry deoxygenated blood from different
organs to the heart.
 Pulmonary veins are exceptions because they carry oxygenated blood from lungs to
the heart. Valves are present in veins to prevent backflow of blood.
Capillaries:

 Arteries on reaching an organ or tissue, divides into smaller and smaller vessels to
bring the blood in contact with all the individual cells
 These are the blood vessels which have single-celled walls.
 They then join together to form veins that convey the blood away from the organ or
tissue

Blood:

 It is a connective tissue which plays Role of the carrier for various substances in body.
 Blood is composed of plasma, blood cells and platelets.

Blood Plasma:

 It is a pale colored liquid which is mostly composed of water.

 It forms the matrix of blood.
 It contains dissolved substances such as proteins, digested food, common salt, waste
products (like carbon dioxide and urea), and hormones.
 Plasma carries all these dissolved substances from one part to another part in the body

Blood Cells:

 There are two types of blood cells: Red Blood Cells (RBC) and White Blood Cells (WBC).

Red Blood Corpuscles (RBCs):

 These are of red color because of the presence of haemoglobin which is a pigment.
 Haemoglobin readily combines with oxygen and carbon dioxide.
 The transport of oxygen and carbon dioxide happens through haemoglobin.
 They do not have nuclei
 Normal haemoglobin level in humans is 13.2 to 16.6 grams per decilitre in males and
11.6 to 15 grams per decilitre in females and Normal haemoglobin level in domestic
animals is Cow 10-15, buffalo 12.5-14.5, dog=8-12;

White Blood Corpuscles (WBCs):

 These are of pale white color. They play important role in the immunity.

Platelets:

 It is responsible for blood coagulation.

 Blood coagulation (clotting) is a defense mechanism which prevents excess loss of
blood, in case of an injury.

Lymph:

 Lymph is similar to blood, but RBCs are absent in lymph.

 Lymph is formed from the fluid which leaks from blood capillaries and goes to the
intercellular spaces in the tissues.
 This fluid is collected through lymph vessels and finally returns to the blood capillaries.
 Lymph also plays an important role in the immune system.
Double Circulation:

 In the human heart, blood passes through the heart twice in one cardiac cycle.
 This type of circulation is called double circulation.
 One complete heartbeat in which all the chambers of the heart contract and relax
once is called cardiac cycle.
 The heart beats about 72 times per minute in a normal adult. In one cardiac cycle, the
heart pumps out 70 mL blood and thus about 4900 mL blood in a minute.
 Double circulation ensures complete segregation of oxygenated and deoxygenated
blood which is necessary for optimum energy production in warm-blooded animals.
 It helps in mammals that constantly use energy to maintain their body temperature.
 In animals that do not use energy as the body temperature depends on the
temperature in the environment like amphibians (like frogs) and reptiles (like lizards)
have three-chambered heart and tolerate some mixing of the oxygenated and de-
oxygenated blood streams.
 Fishes, on the other hand, have only two chambers to their hearts, and the blood is
pumped to the gills, is oxygenated there, and passes directly to the rest of the body.
Thus, blood goes only once through the heart in the fish during one cycle of passage
through the body.

Pulse

 The expansion of an artery each time the blood is forced into it, is called pulse.
 Each heartbeat generates one pulse in the arteries, so the pulse rate of a person is
equal to the number of heart beats per minute.
 As the heart beats about 70 to 72 times per minute, therefore, the pulse rate of an
adult person while resting is 70 to 72 per minute.

Blood Pressure

 The pressure at which blood is pumped around the body by the heart is called blood
pressure.
 The blood pressure of a person is always expressed in the form of two values called
systolic pressure and diastolic pressure.
 The normal blood pressure values are: Systolic pressure: 120 mm Hg Diastolic
pressure: 80 mm Hg. This is usually written as 120/80.
 High blood pressure is called hypertension.
 It is measured by using an instrument called sphygmomanometer
 TRANSPORTATION IN PLANTS

Plants have specialized vascular tissues for transportation of substances.

There are two types of vascular tissues in plants i.e., xylem and phloem.

Xylem:

 Xylem is responsible for transportation of water and minerals.

 It is composed of tracheid’s, xylem vessels, xylem parenchyma and xylem fibres.
 Tracheid’s and xylem vessels are the conducting elements.
 The xylem makes a continuous tube in plants which runs from roots to stem and right
up to the veins of leaves.

Phloem:

 Phloem is responsible for transportation of food.

 Phloem is composed of sieve tubes, companion cells, phloem parenchyma and bast
fibres.
 Sieve tubes are the conducting elements in phloem.
Ascent of Sap

 The upward movement of water and minerals from roots to different plant parts is
called ascent of sap.
 Many factors are at play in ascent of sap and it takes place in many steps.
 They are explained as follows:
 Root Pressure:
o The walls of cells of root hairs are very thin.
o At the roots, cells in contact with the soil actively take up ions.
o This creates a difference in the concentration of these ions between the root
and the soil.
o Water, therefore, moves into the root from the soil to eliminate this difference
o This is osmosis.
o Root pressure is responsible for movement of water up to the base of the stem.
 Capillary Action:
o A very fine tube is called capillary.
o Water or any liquid rises in the capillary because of physical forces and this
phenomenon is called capillary action.
o Water in stem rises to some height because of capillary action.
 Adhesion-cohesion of Water Molecules:
o Water molecules make a continuous column in the xylem because of forces of
adhesion and cohesion among the molecules.
 Transpiration Pull:
o Loss of water vapor through stomata and lenticels in plants is called
transpiration.
o Transpiration through stomata creates vacuum which creates a suction called
transpiration pull.
o The transpiration pull sucks the water column from the xylem tubes and thus
water can rise to great heights in even the tallest plants.

Transport of Food:

 Transport of food in plants happens because of utilization of energy – active transport

 The transport of soluble products of photosynthesis is called translocation
 It occurs in the part of the vascular tissue known as phloem.
 It also transports amino acids and other substances.
 These substances are especially delivered to the storage organs of roots, fruits and
seeds and to growing organs.
 The translocation of food and other substances takes place in the sieve tubes with the
help of adjacent companion cells both in upward and downward directions i.e. it is a
two-way traffic in phloem.
 Material like sucrose is transferred into phloem tissue using energy from ATP.
 This increases the osmotic pressure of the tissue causing water to move into it.
 This pressure moves the material in the phloem to tissues which have less pressure.
 This allows the phloem to move material according to the plant’s needs.
 For example, in the spring, sugar stored in root or stem tissue would be transported
to the buds which need energy to grow
 EXCRETION

 The biological process involved in the removal of these harmful metabolic wastes from
the body.
 Many wastes are produced during various metabolic activities.
 These need to be removed in time because their accumulation in the body can be
harmful and even lethal for an organism.

HUMAN EXCRETORY SYSTEM

 It is composed of a pair of kidneys, a tube called ureter comes out of each kidney and
goes to the urinary bladder.
 Urine is collected in the urinary bladder, from where it is expelled out through urethra
as and when required.

Kidney:

 It is a bean-shaped organ which lies near the vertebral column in the abdominal cavity.
 It is composed of many filtering units called nephrons.
 Nephron is called the functional unit of kidney.
Nephron:

 It is composed of a tangled mess of tubes and a filtering part called glomerulus.

 Glomerulus is a network of blood capillaries to which renal artery is attached.
 The artery which takes blood to the glomerulus is called afferent arteriole and the one
receiving blood from the glomerulus is called efferent arteriole.
 Glomerulus is enclosed in a capsule like portion called Bowman’s capsule.
 The Bowman’s capsule extends into a fine tube which is highly coiled.
 Tubes from various nephrons converge into collecting duct which finally goes to the
ureter.

Filtration in Glomerulus:

 Filtration happens because of very high pressure inside the glomerulus.

 The lumen of efferent arteriole is smaller than that of afferent arteriole.
 Due to this, the blood entering the glomerulus experiences very high pressure and the
waste products are filtered out through the thin membrane of capillaries in the
glomerulus.
 The filtered blood is sent to the systemic circulation through efferent arteriole and the
filtrate goes to the Bowman’s capsule.
 Reabsorption of water and some other filtrates takes place in the tubular part of the
nephron.
 This increases the concentration of urine.
 The human urine is mainly composed of water and urea.
 The amount of water re-absorbed depends on how much excess water there is in the
body, and on how much of dissolved waste there is to be excreted.
 The urine forming in each kidney eventually enters a long tube, the ureter, which
connects the kidneys with the urinary bladder.
 Urine is stored in the urinary bladder until the pressure of the expanded bladder leads
to the urge to pass it out through the urethra.
 The bladder is muscular, so it is under nervous control, as a result, we can usually
control the urge to urinate
ARTIFICIAL KIDNEY (HEMODIALYSIS):

 The procedure used for cleaning the blood of a person by separating the waste
substance (urea) from it is called dialysis
 Kidneys are vital organs for survival.
 Several factors like infections, injury or restricted blood flow to kidneys reduce the
activity of kidneys.
 This leads to accumulation of poisonous wastes in the body, which can even lead to
death.
 In case of kidney failure, an artificial kidney can be used.
 An artificial kidney is a device to remove nitrogenous waste products from the blood
through dialysis.
 Artificial kidneys contain a number of tubes with a semi-permeable lining, suspended
in a tank filled with dialysing fluid.
 This fluid has the same osmotic pressure as blood, except that it is devoid of
nitrogenous wastes.
 The patient’s blood is passed through these tubes.
 During this passage, the waste products from the blood pass into dialysing fluid by
diffusion.
 The purified blood is pumped back into the patient.
 This is similar to the function of the kidney, but it is different since there is no
reabsorption involved.
 Normally, in a healthy adult, the initial filtrate in the kidneys is about 180 L daily.
 However, the volume actually excreted is only a liter or two a day, because the
remaining filtrate is reabsorbed in the kidney tubules.

ORGAN DONATION

 Organ donation is a generous act of donating an organ to a person who suffers from
non-function of organ(s).
 Donation of an organ may be done by the consent of the donor and his/her family.
 Anyone regardless of age or gender can become an organ and tissue donor.
 Organ transplants can save or transform the life of a person.
 Transplantation is required because recipient’s organ has been damaged or has failed
by disease or injury.
  In organ transplantation the organ is surgically removed from one person (organ
donor) and transplanted to another person (the recipient).
 Common transplantations include corneas, kidneys, heart, liver, pancreas, lungs,
intestines and bone marrow.
 Most organ and tissue donations occur just after the donor has died or when the
doctor declares a person brain dead.
 But some organs such as kidney, part of a liver, lung, etc., and tissues can be donated
while the donor is alive.

EXCRETION IN PLANTS

Plants have no special organs for removal of wastes.

The waste products of respiration and photosynthesis are used as raw materials for each
other.

Oxygen gas produced as a by-product of photosynthesis is used up during respiration and

carbon dioxide produced during respiration is used up during photosynthesis.

Excretion is carried out in the plants in the following ways:

 The gaseous wastes, oxygen, carbon dioxide and water vapor are removed through
stomata of leaves and lenticels of stems.
 Some waste products collect in the leaves and bark of trees.
 Many plant waste products are stored in cellular vacuoles.
 When the leaves and bark are shed, the wastes are eliminated.
 Some waste products are rendered harmless and then stored in the plant body as solid
bodies.
 Raphides, tannins, resins, gum, rubber and essential oils are some such wastes.
 Plants also excrete some waste substances into the soil around them.
 2. CONTROL AND COORDINATION
The changes in the environment to which the organisms respond and react are called
stimuli.

The response of organisms to a stimulus is usually in the form of some movement of

their body part.

The reaction to stimuli is a characteristic property of the living organisms.

Both, plants and animals react (or respond) to various stimuli around them differently.

The working together of the various organs of an organism in a systematic manner so as

to produce a proper response to the stimulus, is called coordination.

CONTROL AND COORDINATION IN PLANTS

 The plants coordinate their behaviour against environmental changes by the
chemical substances called plant hormones (Phytohormones)
 The stimuli like light, gravity, chemicals, water, and touch, etc., are called
environmental changes
 The hormones in plants coordinate their behaviour by affecting the growth of a plant
slowly.
 The effect on growth of the plant can result in the movement of a part of the plant
like shoot (stem) or root.
 Dormancy: A resting, inactive condition in which metabolism almost stops.
 Seed: The seed of a plant is inactive or dormant.
o A seed must have certain conditions like water, warmth, air and hormones to
break dormancy and germinate to form a seedling (which then grows into a
plant).
 Bud.
o The bud is a young, undeveloped shoot of a plant which on breaking
dormancy can form a branch, a leaf or a flower depending on its position in
the plant.
 The breaking of dormancy of a bud also requires certain plant hormones.

PLANT HORMONES (PHYTOHORMONES):

Also known as plant growth substances

The growth of a plant can be divided into three stages and these stages have particular
locations in a plant:
 Cell division
 Cell enlargement
 Cell differentiation (or cell specialisation)
These three stages of plant growth as well as promotion of dormancy, breaking of
dormancy, stomata control, falling of leaves, fruit growth, ripening of fruits and ageing in
plants are controlled by the various plant hormones.
 Major types of plant hormones (or phytohormones):

Auxins:
 Promote cell enlargement and cell differentiation and also promote fruit growth.
 Controls a plant’s response to light and gravity (phototropic and geotropic).
 It is made by cells at the tip of stems and roots.
 It moves away from light, and towards gravity.
 It has opposite effect on the growth of stem (Speed up) and roots (Slows down).

Gibberellins:
 Promote cell enlargement and cell differentiation in the presence of auxins.
 Help in breaking the dormancy of seeds and buds
 Promote growth in fruits and shoot extensions

Cytokinins:
 Promote cell division, opening of stomata and fruit growth in plants.
 It also help in breaking the dormancy of seeds and buds.
 They delay the ageing in leaves.

Abscisic acid:
 Functions mainly as a growth inhibitor.
 It promotes dormancy in seeds and buds (this is opposite of breaking of dormancy).
 It also promotes the closing of stomata, the wilting and falling of leaves (abscission).
 It also causes the detachment of flowers and fruits from the plants.
 PLANT MOVEMENTS
The movements of the plant part are usually caused by an unequal growth in its two regions
by the action of plant hormones, under the influence of the stimulus.
 The auxin hormone is made and secreted by the meristematic tissue at the tip of
stem (or tip of shoot).
 It speeds up the growth in stems.
 If one side of a stem has more auxin than the other side, then the side of stem
having more auxin hormone will grow faster than the other side.
 This will cause the stem to bend one side, which means showing movement by
growth.

The plant movements made in response to external stimuli fall into two main categories

 Tropisms
 Nasties

TROPISMS
 Directional movement of the part of a plant caused by its growth (growth dependent
movement).
 Def: A growth movement of a plant part in response to an external stimulus in which
the direction of stimulus determines the direction of response.
 If the growth (or movement) of a plant part is towards the stimulus, it is called
positive tropism
 If the growth (or movement) of a plant part is away from the stimulus, then it is
called negative tropism.
 Phototropism: Growing plant is exposed to light from only one side, then it responds
by bending its stem (or shoot) towards the light. It is positive phototropism.

Types of Tropisms
Response of Plants to Light: Phototropism
Plants need sunlight, so the stems (or shoots) respond to sunlight by growing towards it.

The auxin hormone increases the rate of growth in a stem but it decreases the rate of
growth in a root.

Response of Plants to Gravity: Geotropism

Response of Plants to Water: Hydrotropism

Directional Response of Plants to the Touch of an Object: Thigmotropism

There are some plants called ‘climbing plants’ which have weak stems and hence cannot
stand upright (or erect) on their own.
The climbing plants have climbing organs called tendrils.
Tendrils are the thin, thread-like growths on the stems or leaves of climbing plants.
Two types of tendrils:
 Stem tendrils
 Leaf tendrils.
Tendrils are sensitive to the touch (or contact) of other objects.

Response of Plants to Chemicals: Chemotropism

 The growth (or movement) of a plant part due to chemical stimulus is known as
chemotropism.
 The growth (or movement) of a pollen tube towards the ovule induced by a sugary
substance as stimulus.
 The pollen grain responds to this stimulus by growing a pollen tube in the downward
direction into the style of the carpel and reaches the ovule in the ovary of the flower
for carrying out fertilisation.
 NASTIES (OR NASTIC MOVEMENTS)
 Growth movements or growth-independent movements
 The movement of a plant part in response to an external stimulus in which the
direction of response is not determined by the direction of stimulus is called nastic
movement.
 The main difference between tropic and nastic movements is that tropic movement
is a directional movement of a plant part but nastic movement is not a directional
movement of the plant part with respect to the stimulus.

Thigmonasty
Def: The non-directional movement of a plant part in response to the touch of an object.

 The nastic movement in plants caused by touch is provided by the sensitive plant
Mimosa pudica.

Mimosa pudica:
 It also known as touch-me-not plant (chhui-mui in Hindi).
 The sensitive plant has pad-like swellings called pulvini at the base of each leaf.
 The pulvini contain a lot of water in their cells.
 Due to the internal water pressure in them (called turgor), all the pulvini are very
firm and hold the leaves above them upright.
  The pulvini have also large intercellular spaces (empty spaces) between their cells.
 When the leaves of sensitive plant are touched with a finger, then an electrical
impulse is generated which travels through ordinary cells.
 This electrical impulse acts on a plant hormone.
 The plant hormone makes the water migrate from the cells of one half of a pulvinus
to the intercellular spaces in the other half of pulvinus.
 This leads to lose their firmness causing the leaves to droop and fall.

Photonasty
Def: The non-directional movement of a plant part (usually petals of flowers) in response to
light.

 A dandelion flower opens up in the morning in bright light but closes in the evening
when the light fades and it gets dark.
 The petals of moonflower close during the day when there is bright light but open up
at night when it is dark and there is no light.

Functions of Plant Hormones (or Phytohormones)

The plant hormones (or phytohormones) regulate many functions in plants:

 Germination of seeds (or Breaking the dormancy of seeds),

 Growth of root, stem and leaves,
 Movement of stomata (or stomatal movement) in leaves,
 Flowering of plants,
 Ripening of fruits, and
 Phototropism, geotropism, chemotropism, hydrotropism, thigmotropism and nastic
movements.
 COORDINATION IN ANIMALS
The multicellular animals (except sponges) have specialised cells called nerve cells (or
neurons) to respond to stimuli and coordinate their activities.
A system made up of nerve cells is called nervous system.

The control and coordination in higher animals called vertebrates takes place through nervous
system as well as hormonal system called endocrine system.
A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type
of stimulus (or a particular type of change in the environment) such as light, sound, smell,
taste, heat, pressure, etc.

 Photoreceptors detect light (they are present in eyes),

 Phonoreceptors detect sound (they are present in inner ears),
 Olfactory receptors detect smell (they are present in nose),
 Gustatory receptors detect taste (they are present in tongue)
 Thermoreceptors detect heat or cold (they are present in skin).
A stimulus is a kind of energy such as light, sound, smell, taste, heat, or mechanical pressure,
etc.
At a receptor, the energy provided by a stimulus sets off a chemical reaction which converts
the energy of stimulus into an electrical signal called ‘electrical impulse’ (nerve impulse or
impulse).
The receptors in the sense organs receive stimuli from the surrounding environment and send
the message conveyed by them to the spinal cord and brain in the form of electrical impulses
through the sensory nerves.
Another type of nerves called motor nerves transmit the response from the brain and spinal
cord to the effectors in the form of electrical impulses.
An effector is a part of the body which can respond to a stimulus according to the instructions
sent from the nervous system (spinal cord and brain).
The effectors are mainly the muscles and glands of our body.

All our muscles and glands respond to electrical impulses sent from the nervous system
through motor nerves.
 CONTROL AND COORDINATION IN HUMANS
There are two systems of coordination of activities in humans. These are:

 Nervous system, and

 Endocrine system (or Hormonal system).

HUMAN NERVOUS SYSTEM

The function of nervous system is to coordinate the activities of our body.
It is the control system for all our actions, thinking and behaviour.
It helps all other systems of our body to work together.

The Unit of Nervous System: Neuron

Neuron is the largest cell in the body.
A neuron (or nerve cell) has three components:

 Cell body
 Dendrites
 Axon

The cell body of a neuron is like a typical animal cell which contains cytoplasm and a nucleus.
A number of long and thin fibres are stretching out from the cell body of a neuron are called
nerve fibres.
The shorter fibres on the body of a neuron are called dendrites.
The longest fibre on the cell body of a neuron is called axon.
The axon has an insulating and protective sheath of myelin around it (fat and protein).

Transmission of impulse:
Neurons are of three types:
 Sensory neurons transmit impulses from the sensory cells (or receptors) towards the
central nervous system (spinal cord and brain).
 Motor neurons transmit impulses from the central nervous system (spinal cord and
brain) towards the muscle cells (or effectors).
 Relay neurons occur in the central nervous system (brain and spinal cord) where
they serve as links between other neurons.

Synapse:
 Any two neurons in the nervous system do not join to one another completely.
 There is always a very, very small gap between the two neurons (where they join)
called synapse.
 The nerve impulses are carried over this small gap between a pair of neurons by
means of a chemical substance called neurotransmitter substance.
 Def: A microscopic gap between a pair of adjacent neurons over which nerve
impulses pass when going from one neuron to the next
 THE ORGANS OF HUMAN NERVOUS SYSTEM
The main organs of the nervous system are:

 Brain,
 Spinal cord
 Nerves.

The Parts of the Nervous System

Reflex Action and Reflex Arcs

  The simplest form of response in the nervous system is reflex action.
 This is a rapid, automatic response to a stimulus which is not under the voluntary
control of the brain.
 It is described as an involuntary action.
 Thus, a reflex action is one which we perform automatically.
 The pathway (or route) taken by nerve impulses in a reflex action is called reflex arc
 The reflexes of this type which involve only the spinal cord are called spinal reflexes.
 Most of the reflex actions involve only the spinal cord.
 Those reflex actions which involve brain are called cerebral reflexes.
 Eg: The contraction of pupil of our eye automatically in the presence of bright light

Autonomic Nervous System

 The term autos means self and nomos means governing, so autonomic nervous
system means self-governing nervous system.
 It controls and regulates functions of internal organs of our body involuntarily (on its
own).
 Like breathing, heart beat, digestion, sweating, etc

Voluntary Nervous System

The voluntary nervous system helps us take voluntary actions which are under the conscious
control of the brain.
 CENTRAL NERVOUS SYSTEM
The central nervous system (CNS) consists of the brain and the spinal cord.

BRAIN
It is the highest coordinating centre in the body.
It is protected by a bony box in the skull called cranium.
The brain is surrounded by three membranes called meninges, which help to protect it.

The space between the membranes (or meninges) is filled with a cerebro spinal fluid which
protects the brain from mechanical shocks.
Pairs of cranial nerves arise from the brain.
The brain is broadly divided into three regions:

 The forebrain consists mainly of cerebrum.

 The midbrain does not have any further divisions.
 The hindbrain consists of three centres called pons, cerebellum and medulla.

Cerebrum:
 The cerebrum (or forebrain) is the main thinking part of the brain.
  It is the site of our faculties such as learning, reasoning, intelligence, personality and
memory.
 All our thoughts, sensations, actions and movements are controlled by the cerebrum.
 All the voluntary actions of the body are coordinated by the cerebrum.
MID BRAIN:
 It controls reflex movements of the head, neck and trunk in response to visual and
auditory stimuli.
 It also controls the reflex movements of the eye muscles, changes in pupil size and
shape of the eye lens.
HIND BRAIN:
The pons takes part in regulating respiration. The cerebellum:
 It helps in maintaining posture and balance of the body.
 It also enables us to make precise and accurate movements.
 It coordinates smooth body movements such as walking, dancing, riding a bicycle
and picking up a pencil, etc.
THE MEDULLA:
 It controls various involuntary actions such as heartbeat (blood circulation),
breathing, blood pressure and peristaltic movements of alimentary canal.
 It is also the controlling centre for reflexes such as swallowing, coughing, sneezing,
secretion of saliva and vomiting.

SPINAL CORD
It is a cylindrical structure.

It begins in continuation with medulla and extends downwards. It is enclosed in a bony cage
called vertebral column.
It is also surrounded by membranes called meninges.
As many as 31 pairs of nerves arise from the spinal cord.

It is concerned with spinal reflex actions and the conduction of nerve impulses to and from
the brain.
The various functions of brain are as follows:
 The brain receives information-carrying nerve impulses from all the sensory organs of
the body.
 The brain responds to the impulses brought in by sensory organs by sending its own
instructions (through motor nerves) to the muscles and glands causing them to
function accordingly.
 The brain correlates the various stimuli from different sense organs and produces the
most appropriate and intelligent response.
 The brain coordinates the body activities so that the mechanisms and chemical
reactions of the body work together efficiently.
 The brain stores ‘information’ so that behaviour can be modified according to the
past- experience. This function makes the brain the organ of thought and intelligence.
 THE ENDOCRINE SYSTEM
A group of endocrine glands which produces various hormones is called an endocrine system.
The endocrine system is also called hormonal system.
Hormones:

 These are the chemical substances which coordinate the activities of living organisms
and their growth.
 They are secreted in small amounts by the endocrine glands.
 They are poured directly into the blood and carried throughout the body by blood
circulatory system.
 They have their effect at the sites different from the sites where they are made. So,
called chemical messengers.
 They act on specific tissues or organs (called target organs).
 They act as messengers between the nervous system and the organs of our body.
They coordinate the activities of the body and its growth.
Glands:
A gland is a structure which secretes a specific substance (or substances) in the body. A gland
is made up of a group of cells or tissue.
There are two types of glands in the body:
Exocrine glands
 Def: A gland which secretes its product into a duct (or tube)
 Eg: The salivary gland secretes the saliva into a duct called salivary duct.
Endocrine glands
 Def: A gland which does not have a duct and secretes its product directly into the
blood stream. These are are ductless glands.
 It secretes a chemical substance called hormone.
 They release hormones directly into the blood of a person.
 These hormones reach the concerned body part through the blood and act on it.
 The glands are Pineal gland, Hypothalamus gland, Pituitary gland, Thyroid gland,
Parathyroid glands, Thymus, Pancreas, Adrenal glands, Testes (only in males) and
Ovaries (only in females).
Both Exocrine and endocrine glands:
The pancreas, testes and ovary are such glands.
The Pancreas:
 It acts as an endocrine gland and secretes the hormone insulin.
 It also acts as an exocrine gland and secretes pancreatic juice containing digestive
enzymes into the pancreatic duct that leads to the alimentary canal.
The testes:
 They act as endocrine glands and secrete the hormone called testosterone.
 They act as exocrine glands and release sperms (male sex cells) into the duct.
The ovaries:
 They act as endocrine glands and secrete the hormones oestrogen and progesterone.
 They act as exocrine glands and release ova or eggs (female sex cells) into the duct.
Anatomical location of endocrine glands:
PITUITARY GLAND

OTHER GLANDS
HORMONAL DISORDERS
 3. HOW DO ORGANISMS REPRODUCE
Introduction:
Def: The production of new organisms from the existing organisms of the same species.
It is essential for the survival of a species on this earth.
It ensures continuity of life on earth.

It gives rise to more organisms with the same basic characteristics as their parents.

Types of Reproduction

Asexual Reproduction:
Def: The production of a new organism from a single parent without the involvement of sex
cells (or gametes).
 Binary fission in Amoeba; budding in Hydra; spore formation in Rhizopus fungus (or
bread mould); regeneration in Planaria (flatworm); fragmentation in Spirogyra and
vegetative propagation in flowering plants (like rose plants).

Sexual Reproduction:
Def: The production of a new organism from two parents by making use of their sex cells (or
gametes).
 The humans, fish, frogs, hens, cats, dogs, cows, horses, deer, rabbits, lions and tigers.
Most of the flowering plants
 ASEXUAL REPRODUCTION
1. FISSION
In the process of fission, a unicellular organism splits (or divides) to form two (or more) new
organisms.
It is of two types, depending on whether the parent organism splits to form two new
organisms or more than two organisms
 Binary fission
 Multiple fission
(i) Binary Fission
It is an asexual method of reproduction of organisms.
The parent organism splits (or divides) to form two new organisms.

When this happens, the parent organism ceases to exist and two new organisms come into
existence.

 Unicellular organisms like Amoeba, Paramecium, Leishmania, bacteria, etc.

Amoeba:
 Amoeba cell has reaches its maximum size of growth.
 The nucleus of Amoeba lengthens and divides into two parts.
 The cytoplasm of Amoeba divides into two parts, one part around each nucleus.
 One parent Amoeba divides to form two smaller Amoebae (daughter Amoebae).
Paramecium:
It is a unicellular animal having short thread-like structures called cilia over its surface.

Leishmania
It is a unicellular animal (protozoan)

It is a parasite which causes the disease known as kala-azar (or black fever).

(ii) Multiple Fission

It is also an asexual method of reproduction in organisms.
The parent organism splits (or divides) to form many new organisms at the same time.

Plasmodium:
 A cyst or protective wall is formed around the cell of a single-celled organism
 Inside the cyst, the nucleus of cell splits (or divides) several times to form many smaller
nuclei called daughter nuclei.
 Little bits of cytoplasm collect around each daughter nuclei and thin membranes are
formed around them.
 In this way, many new daughter cells are formed from a single parent cell within cyst
 2. BUDDING
The small part of the body of the parent organism grows out as a ‘bud’ which then detaches
and becomes a new organism.

i. Hydra:
 It is a simple multicellular animal.
 First a small outgrowth called ‘bud’ is formed on the side of its body by the repeated
mitotic divisions of its cells.
 This bud then grows gradually to form a small Hydra by developing a mouth and
tentacles
 And finally the tiny new Hydra detaches itself from the body of parent Hydra and lives
as a separate organism

ii. Yeast

 It is tiny, unicellular, non-green plant (which is a fungus).

 First a bud appears on the outside of the cell wall.
 The nucleus of parent yeast cell then divides into two parts and one part of the nucleus
moves into the bud.
 Ultimately, the bud separates off from parent yeast cell and forms a new yeast cell.
 3. SPORE FORMATION
Spores are the microscopic ‘asexual reproductive bodies’ which are covered by a hard
protective coat.
When the spore case of the plant bursts, then the spores spread into air.
This coat enables them to survive under unfavourable conditions like lack of food, lack of
water and extreme temperatures.
But when the conditions are favourable then the spores germinate to produce new plants.
Eg: Most of the fungi (like Rhizopus, Mucor, etc.), bacteria and non-flowering plants such as
ferns and mosses.
i. Bread mould (Rhizopus fungus)

 The tiny spores of ‘bread mould’ (a fungus plant) are almost always present in the air.
 If we keep a moist slice of bread aside for a few days, then the spores of bread mould
plant present in air settle on the moist bread and germinate to form new fungus
plants.
 The bread mould plants first look like a white cottony mass covering the bread slice
which later on turns black.

 The common bread mould plant consists of fine, threadlike projections called hyphae
and thin stems having knob-like structures called sporangia.
 Each knob-like structure (or sporangium) contains hundreds of minute spores
enclosed in a spore case.
 When the spore case bursts, the tiny spores are dispersed in air.
 These spores are the asexual reproductive units which can produce more bread mould
plants under suitable conditions.
 4. REGENERATION
The process of getting back a full organism from its body parts is called regeneration.
The regeneration of an organism from its cut body part occurs by the process of growth and
development.
This happens as follows:
 The cells of cut body part of the organism divide rapidly to make a ‘ball of cells’.
 The cells present in the ‘ball of cells’ move to their proper places within the ball where
they have to form various organs and body parts of the organism.
 The cells then change their shapes (or become specialised) to form different types of
tissues.
 These different tissues form various organs and body parts of the organism.
i. Planaria:
 It is a flatworm which is found in freshwater ponds and slow moving streams.
 It possesses great power of regeneration.
 If the body of it somehow gets cut into a number of pieces, then each body piece can
regenerate into a complete planaria by growing all the missing parts.

ii. Hydra
 If it gets cut into a number of pieces, then each body piece of it can grow into a
complete Hydra
 5. FRAGMENTATION
Def: The breaking up of the body of a simple multicellular organism into two (or more) pieces
on maturing, each of which subsequently grows to form a complete new organism.
The main difference between fission and fragmentation is that in fission, a unicellular
organism breaks up to form two (or more) daughter organisms, whereas in fragmentation, a
multicellular organism breaks up to form two (or more) daughter organisms.
 Spirogyra & sea anemones (marine animals)
i. Spirogyra:
 It is a green, filamentous alga plant which is found in ponds, lakes and slow moving
streams.
 Its filament simply breaks into two or more fragments on maturation, and each
fragment then grows into a new Spirogyra.
 This breakup of the filament of a mature Spirogyra on its own brings about asexual
reproduction.

6. VEGETATIVE PROPAGATION
The new plants are obtained from the parts of old plants (like stems, roots and leaves),
without the help of any reproductive organs.
The green grass grows in the fields after rains from the dry, old stems of grass plants present
in the fields, by the method of vegetative propagation
 Bryophyllum, Guava, Potato, Onion, Banana, Garlic, Water hyacinth, Tulip, Mint,
Strawberry and Lily.
i. Bryophyllum plants:
 It can be reproduced by vegetative propagation by using either a piece of its stem or
its leaves.

This happens as follows:

 The leaves of a Bryophyllum plant have special type of buds in their margins (or edges).
 These buds may get detached from the leaves or together with the leaf, fall to the
ground and then grow to produce new Bryophyllum plants.
ii. Money plant:
 It can also be grown by vegetative propagation by using a piece of its stem.
 A piece of stem of money plant in such a way that it contains at least one leaf on it is
detached.
 Dip one end of this stem in water.
 The new roots appear at the point where leaf was attached.
 The piece of stem will gradually grow into a new money plant.

iii. Tubers:
 A tuber is the thickened, underground stem (or root) of a plant which is swollen with
stored food.
 It has a number of ‘buds’ (called ‘eyes’).
 Each bud (or eye) of the tuber grows into a new plant when the old tuber is planted in
the soil in the next growing season.
 There are two types of tubers:
o Stem tubers: Potato
o Root tubers. Sweet potato
Potato tuber:
 It is an underground stem of the potato plant.
 It can be used for the vegetative reproduction of potato plants.
 Each potato tuber can produce more than one plant
 ARTIFICIAL PROPAGATION OF PLANTS
Def: The process of growing many plants from one plant by manmade methods.
A number of methods of artificial propagation of plants are used in agriculture (for raising
crops), and horticulture (cultivation of vegetables, fruits and flowers).
A number of methods of artificial propagation of plants are used in agriculture (for raising
crops), and horticulture (cultivation of vegetables, fruits and flowers).
The three common methods for the artificial propagation of plants are:
 Cuttings
 Layering
 Grafting
1. Cutting:
 Def: A small part of a plant which is removed by making a cut with a sharp knife.
 It may be a piece of stem, root or even a leaf with some buds on it.
 Eg: rose, Bougainvillea, Chrysanthemum, grapes, sugarcane, bananas, and cactus.

2. Layering

 In this method, a branch of the plant is pulled towards the ground and a part of it is
covered with moist soil leaving the tip of the branch exposed above the ground.
 After some time, new roots develop from the part of the branch buried in the soil.
 The branch is then cut off from the parent plant.
 The part of the branch which has developed roots grows to become a new plant (just
like the parent plant).
 The layering method is used for the propagation (or reproduction) of plants like :
Jasmine, Strawberry, Raspberry, Lemon, Guava, Hibiscus (China rose), Bougainvillea
and many slender ornamental plants.
Natural layering method:
 The natural layering occurs because these plants form runners (which are soft
horizontal stems running above the ground).
 Wherever the ends of such runners touch the ground, new plants are formed at those
places.
 In this way, many more strawberry or raspberry plants are formed from the parent
plant in a natural way.
i. Jasmine plant (chameli):

3. Grafting
It is a method in which the cut stems of two different plants (one with roots and other without
roots) are joined together in such a way that the two stems join and grow as a single plant.
Grafting is used to breed fruit trees and flowering bushes.
Apple, peach, apricot and pear trees are often grafted.
This new plant will have the characteristics of both the original plants.

 The cut stem of a plant having roots is called stock.

 The cut stem of another plant (without roots) is called scion.

In carrying out grafting, two plants (or trees) are chosen which are to be used as scion and
stock.
 First, the stem/ branch is removed from the plant chosen to be made scion by making
a slanting cut (scion).
 The stem of second plant (or tree) to be used in grafting is also cut in a slanting way
(stock).
 The scion is placed over the stock.
 The cut surfaces of the scion and stock are fitted together and bound tightly with a
piece of cloth and covered properly with polythene sheet (so as to prevent harmful
infection by bacteria or fungus, and loss of water and plant sap from the cut and joined
ends of stock and scion).
 The cambium layer of scion is in contact with the cambium layer of stock (cambium
layer in the stem is responsible for growth).
 The stock and scion of two plants grow together and become one plant.
  The scion continues to produce its original leaves, flowers and fruits but it gets water
and minerals for making food from the chosen stock.
 So, the fruits will have the characteristics of both the plants.

The advantages of the grafting method of artificial propagation:

 Grafting enables us to combine the most desirable characteristics of the two plants
(scion and stock) in its flowers and fruits.
 By grafting method, a very young scion (shoot part of a plant) can be made to flower
and produce fruits quite fast when it is grafted to the stock (stem having roots) of a
mature plant.
 It enables us to obtain flowers and fruits having different desired characteristics by
grafting scions from different varieties of plants on the same stock. Many varieties of
mango have been produced by grafting method.
 Grafting can be used to produce varieties of seedless fruits.
Artificial vegetative propagation:
It is usually used for the propagation (or reproduction) of those plants which produce either
very few seeds or do not produce viable seeds.
Some examples of such plants which are reproduced by artificial vegetative propagation
methods are : Banana, Pineapple, Orange, Grape, Rose.
Advantages of Artificial Vegetative Propagation
 The new plants produced by artificial vegetative propagation will be exactly like the
parent plants. Any desirable features of the parent plant will be replicated in the new
plants.
 The fruit trees grown from seeds may take many years before they start to bear fruit.
But the fruit trees grown from cuttings or by grafting start to bear fruits much earlier
(only after a few growing seasons).
 The plants grown by vegetative propagation usually need less attention in their early
years than the plants grown from seeds.
 Many plants can be grown from just one parent plant by artificial propagation.
 We can also get seedless plants by artificial propagation.

TISSUE CULTURE
Def: The production of new plants from a small piece of plant tissue / cells removed from the
growing tips of a plant in a suitable growth medium.

The growth medium contains various plant nutrients in the form of ‘jelly’ (agar) and plant
hormones which are necessary for plant growth.
The process of tissue culture for producing new plants is carried out as follows:
 A small piece of plant tissue being taken from the growing point (tip) of a plant into
growth medium.
 Plant tissue grows to form callus(shapeless lump of mass)
 Callus develops roots and shoots
 Many plantlets are produced.
 These can be transplanted into pots or soil
The tissue culture technique is being used increasingly for the production of ornamental
plants like orchids, dahlia, carnation, Chrysanthemum, etc.
The production of plants by the method of tissue culture is also known as micro propagation.
Advantages of Tissue Culture
 Tissue culture is a very fast technique. Thousands of plantlets can be produced in a
few weeks’ time from a small amount of plant tissue.
 The new plants produced by tissue culture are disease free.
 Tissue culture can grow plants round the year, irrespective of weather or season.
 Very little space is needed for developing new plants by tissue culture.

Do Organisms Create Exact Copies of Themselves in Asexual Reproduction

Asexual reproduction usually results in the production of genetically identical offspring’s, the
only genetic variation arises as a result of occasional inaccuracies in DNA replication (or DNA
copying) at the time of cell division.
The material which carries genetic information from the parents to the offsprings is DNA–
Deoxyribo Nucleic Acid (as chromosomes in the nuclei of all the cells).
Mitosis is the division of a nucleus into two identical daughter nuclei.
Each daughter nucleus has the same genetic make up because of the replication of DNA (or
copying of DNA) of the parent cell.

The new organisms (or offsprings) produced by one parent through asexual reproduction
(which are genetically identical to the parent) are called clones.
 This method is called cloning.
These slight variations in the replication of DNA molecule will lead to slight variations in the
offsprings produced by asexual reproduction.
The importance of variations in organisms introduced during reproduction is that it helps the
species of various organisms to survive and flourish even in adverse environment.
 SEXUAL REPRODUCTION
 It takes place by the combination of special reproductive cells called sex cells.
 Sex cells are of two types: male sex cells and female sex cells.
 The sex cells are commonly known as gametes.
 In sexual reproduction a male gamete fuses with a female gamete to form a new cell
called zygote.
 This zygote then grows and develops into a new organism in due course of time.

SEXUAL REPRODUCTION IN FLOWERING PLANTS

The plants in which the sex organs are carried within the flowers and the seeds are enclosed
in a fruit are called angiosperms.

Angiosperms are commonly known as flowering plants.

The sex organs (or reproductive organs) of a plant are in its flowers.
The function of a flower is to make male and female gametes and to ensure that fertilisation
will take place to make new seeds for the reproduction of plant.
Steps of sexual reproduction in plants:
 The male organ of flower called stamen makes the male gametes present in pollen
grains.
 The female organ of a flower called carpel makes the female gametes present in
ovules, also called ova, egg cells or just eggs.
 The male gametes present in pollen grains fertilise the female gametes or egg cells
present in ovules.
 The fertilised egg cells grow within ovules and become seeds.
 The seeds produce new plants on germination (under suitable conditions).
 MAIN PARTS OF A FLOWER
Receptacle:
 The base of a flower to which all the parts of a flower are attached.
Sepals:
 The green, leaf-like parts in the outermost circle of a flower.
 All the sepals taken together are called calyx.
 The function of sepals (or calyx) is to protect the flower in its initial stages when it is
in the form of a bud.
Petals:
 The colourful parts of a flower.
 The petals lie inside the sepals.
 All the petals taken together are called corolla.
 The petals are usually scented.
 The function of petals (or corolla) is to attract insects (for pollination) and to protect
the reproductive organs which are at the centre of the flower.

Stamen:
 The little stalks with swollen tops just inside the ring of petals in a flower.
 It is the male reproductive organ of the plant.
 It produces pollen grains.
 It is made of two parts: a filament and an anther.
o Filament:
 The stalk of stamen
o Anther:
 The swollen top of stamen.
 It is actually the anther which makes the pollen grains and stores them.
 The pollen grains appear to be yellow, powder-like substance to us.
 Pollen grains contain the male gametes of the plant.
 The flower usually has a number of stamens in it.
Carpel:
 This is a flask shaped organ in the centre of a flower.
 The female organ of a plant is known by two names: carpel and pistil
 It is made of three parts:
o Stigma:
 It is the top part of carpel.
 It receives pollen grains from the anther of stamen during pollination.
 It is sticky so that pollen can stick to it.
o Style:
 It is the middle part of carpel.
 It is a tube which connects stigma to the ovary.
o Ovary:
 It is the swollen part at the bottom of a carpel.
 It makes ovules and stores them.
 Ovules contain the female gametes (or female sex cells) of the plant.
 There are usually many ovules in the ovary.
 Each ovule contains only one female gamete of plant called ovum or
egg.
Unisexual Flowers:
 These flowers which contain only one sex organ, either stamens or carpels.
 The flowers of papaya and watermelon plants
Bisexual flowers:
 The flowers which contain both the sex organs, stamens as well as carpel.
 The flowers of Hibiscus and mustard plants.

FORMATION OF NEW SEED OF A PLANT

It is formed when the male gamete present in a pollen grain unites with the female gamete
present in the ovule.

This happens in two steps by pollination and fertilisation.

1. Pollination:
 Def: The transfer of pollen grains from the anther of a stamen to the stigma of a carpel.
 It is done by insects (like bees and butterflies), birds, wind, and water.
 It can occur in two ways:
o Self-pollination:
 When the pollen grains from the anther of a flower are transferred to
the stigma of the same flower (or another flower on the same plant)
o Cross-pollination.
 When the pollen grains from the anther of a flower on one plant are
transferred to the stigma of a flower on another similar plant.
 Insects help in cross-pollination
 When an insect sits on the flower of a plant for sucking nectar.
 The pollen grains from the anther of this flower stick to its body.
  And when this insect now sits on another flower of another
similar plant, then the pollen grains sticking to its body are
transferred to the stigma of this second flower.
 The blowing wind also carries pollen grains from one flower to another
flower and helps in cross pollination

2. Fertilisation.
 It occurs when the male gamete present in pollen grain joins with the female gamete
(or egg) present in ovule.
 When a pollen grain falls on the stigma of the carpel, it bursts open and grows a pollen
tube downwards through the style towards the female gamete in the ovary.
 In ovary, the male gamete of pollen combines with the nucleus of female gamete or
egg present in ovule to form a fertilised egg (called zygote).

Formation of fruits and seeds

Fruit:
 The fertilised egg (or zygote) divides several times to form an embryo within the ovule.
 The ovule develops a tough coat around it and is gradually converted into a seed
(containing the baby plant).
 The ovary of flower develops and becomes a fruit (with seeds inside it).
 Other parts of flower like sepals, petals, stamens, stigma and style dry up & fall off.
 Only the ovary is left behind.
 So, at the place on plant where we had a flower originally, we now have a fruit (which
is the ovary of the flower containing seeds).
 A fruit protects the seeds.
Seed:
 A seed is the reproductive unit of a plant (which can be used to grow a new plant).
 The seed contains a baby plant (or embryo) and food for the baby plant.
 The part of baby plant in seed which develops into shoot with leaves is called plumule
and the part which develops into root is called radicle.
 The part of seed which contains stored food for the baby plant is called cotyledon.

Germination of Seeds
 The seeds obtained from a plant are usually very dry.
 It can remain alive but inactive for long periods, called dormant.
 The beginning of the growth of seeds is called germination of seeds.
 It begins when the seed absorbs water, swells and bursts through the seed coat.
 The water helps the enzymes to function in the seed.
 The enzymes digest the stored food in cotyledons and make it soluble.
 This soluble food makes the radicle and plumule present in the seed to grow.
 The radicle of the seed grows first to form the root
 The root pushes down into the soil and begins to absorb water and minerals from soil.
 After this the plumule grows upwards to form the shoot.
 When the shoot comes up above the ground, it develops green leaves.
 The green leaves of the shoot begin to synthesise own food in the presence of sunlight.
 This seedling grows gradually and ultimately becomes a new plant.
 SEXUAL REPRODUCTION IN ANIMALS
The cells involved in sexual reproduction are called gametes.
Gametes are the sexual reproductive cells (or sex cells).
 These are special type of cells called reproductive cells which contain only half the
amount of DNA (or half the number of chromosomes) as compared to the normal body
cells of an organism.
 Gametes are of two types:
o Male gametes: The male gamete/ sec cells in animals is called sperm
o Female gametes: The female gamete/ sex cells in animals is called ovum or egg.

It leads to a greater variety in population and origin of new species having different
characteristics.

Copulation:
It is the act by which the male animal transfers his sperms into the female animal’s body.

Fertilisation
Def: The fusion of a male gamete with a female gamete to form a zygote during the sexual
reproduction.
 Types of fertilisation:
o Internal Fertilisation.
o External Fertilisation.
Internal fertilisation:
 Def: The fertilisation which occurs inside the female body.
 The female animal’s eggs are fertilised by sperms inside her body.
 Eg: Mammals (including human beings), birds and reptiles.

External fertilisation:

 The fertilisation which occurs outside the female body.

 The female animal’s eggs are fertilised by sperms outside its body.
 The male and female animals release their sperms and eggs in water where
fertilisation takes place by collisions between sperms and eggs
 Eg: Amphibians (like frogs and toads) and fishes.
Puberty

It is the age at which the reproductive organs reach maturity and secondary sexual
characteristics develop.

It is also the age at which the sex hormones (or gametes) begin to be produced and the boy
and girl become sexually mature (able to reproduce).

It start earlier in girls at age of 10 to 12 and boys at the age of 13 to 14 years.

The male gonads called testes start producing male gametes called sperms and male sex
hormone called testosterone
The female gonads called ovaries start producing female gametes called ova (or eggs) and two
female sex hormones, oestrogen and progesterone.
The sex hormones play an important role in the process of reproduction because they make
the reproductive organs to mature and start functioning.
The various changes which occur in boys at puberty are:
 Hair grow under armpits and in pubic regions (genital area) between the thighs.
 Hair also grow on other parts of the body like chest and face (moustache, beard, etc.)
 Body becomes more muscular due to the development of muscles.
 The voice deepens (or cracks).
 Chest and shoulders broaden.
 The external genital organs become larger and testes start to make sperms.
 All these changes in boys are brought about by the male sex hormone ‘testosterone’
made in testes.
The various changes which occur in girls at puberty are:
 Hair grow under armpits and pubic region (This change is the same as in boys).
 Mammary glands (or breasts) develop and enlarge.
 The hips broaden.
 Extra fat is deposited in various parts of the body like hips and thighs.
 External sexual organs enlarge.
 Ovaries start to release eggs.
 Menstruation (monthly periods) start.
 All these changes in girls are brought about by the female sex hormones oestrogen
and progesterone made in ovaries.

THE MALE REPRODUCTIVE SYSTEM

Testes:
 These are the primary reproductive organs in males.
 These are the oval shaped organs which lie in scrotum outside the abdominal cavity
of a man.
 A man has two testes (singular of testes is testis).
 The function of is to make the male sex cells (or male gametes) called sperms and male
sex hormone called testosterone.
 These are outside the abdominal cavity of the body (and not deep inside the body),
because the sperm formation requires 30 lower temperature than the normal body
temperature.
Epididymis:
 The sperms formed in testes come out and go into a coiled tube called epididymis and
are stored temporarily.
Vas Deferens (Sperm duct):
 From epididymis, the sperms are carried by a long tube called vas deferens which joins
with another tube called urethra coming from the bladder.
Seminal vesical and prostate gland:
 It is present along the path of vas deferens,
 They add their secretions to sperms so that the sperms are now in a liquid.
 This liquid plus the sperms it contains is called semen (which is a thick liquid).
 These secretions provide nutrition to the sperms and also make their further transport
easier.
Urethra:

 It forms a common passage for sperms and urine.

 It carries the sperms to an organ called penis which opens outside the body.
Penis:
 It passes the sperms from the man’s body into vagina in the woman’s body during
copulation for the purpose of reproduction.
 In human male there is only one opening for the urine and sperms to pass out of the
body.

THE FEMALE REPRODUCTIVE SYSTEM

Ovaries:
 These are the primary reproductive organs in a woman (or female).
 These are the oval shaped organs which are inside the abdominal cavity of a woman
near the kidneys.
 A woman has two ovaries.
 The function is to make mature female sex cells (or female gametes) called ova or
eggs, and also the female sex hormones (called oestrogen and progesterone).
 Each ovary is composed of several thousand follicles (which are a kind of unripe eggs
or unripe ova).
 At puberty these follicles mature to form the ripe eggs or ripe ova (required for
fertilisation).
Oviducts (fallopian tubes):
 These are the tubes just above the ovaries.
 They are not directly connected to ovaries but have funnel shaped openings which
almost cover the ovaries.
 The ovum (or egg cell) released by an ovary goes into the oviduct through its funnel-
shaped opening.
 The fertilisation of egg (or ovum) by a sperm takes place in the oviduct.
 The two oviducts connect to a bag like organ called uterus at their other ends.
Uterus (womb):
 The growth and development of a fertilised ovum (or fertilised egg) into a baby takes
place in the uterus.
 The uterus is connected through a narrow opening called cervix to another tube called
vagina which opens to the outside of the body.
Vagina:
 It receives the penis for putting sperms into the woman’s body.
 It is a tubular structure.
 It is also called birth canal because it is through this passage that the baby is born after
the completion of development inside the uterus of the mother.
 In woman (or human female) the opening for passing out urine (called urethra) and
the vaginal opening are separate.
Fertilisation
 In human beings, internal fertilisation takes place.
 The sperms (or male gametes) made in the testes of man are introduced into the
vagina of the woman through penis during copulation (or mating).
 In this way, millions of sperms are released into the vagina at one time.
 The sperms are highly active and mobile (moving).
 The sperms move up through cervix into the uterus.
 From uterus, the sperms pass into the oviducts.
 One of the oviducts contains an ovum (or egg cell) released by the ovary during
ovulation.
 Only one sperm fuses with the ovum (or egg) in the oviduct to form a zygote.
 The fertilisation of the ovum (or egg) takes place in the oviduct.
Development of Embryo
 When the ovum (or egg) is fertilised in the oviduct, then a zygote is formed.
 The zygote divides rapidly by mitosis as it moves down slowly in the oviduct and forms
a hollow ball of hundreds of cells.
 This hollow ball of cells, now called an embryo, sinks into the soft and thick lining of
the uterus and gets embedded in it.
 The embedding of embryo in the thick lining of the uterus is called implantation
 After implantation, a disc-like special tissue develops between the uterus wall (called
uterine wall) and the embryo (or foetus), which is called placenta.
 The foetus is connected to placenta in mother’s body through umbilical cord). It is
through the placenta that all the requirements of the developing foetus like nutrition,
respiration, and excretion, etc., are met from the mother's body.
 In other words, the exchange of nutrients, oxygen and waste products between the
embryo and the mother takes place through the placenta.
 The time period from the fertilisation up to the birth of the baby is called gestation.
 The average gestation period in humans (or the average duration of human
pregnancy) is about nine months (or about 38 weeks).
 During the gestation period, the foetus grows to become a baby.
 Birth begins when the strong muscles in the walls of the uterus start to contract
rhythmically.
 The rhythmic contraction of uterus muscles gradually pushes the baby out of the
mother’s body through vagina.

Sexual Cycle in Females: Menstruation

 In an immature girl, ovaries already contain many thousands of immature ova (or eggs)
which are contained in immature follicles.
 When a girl reaches the age of puberty, then one follicle develops at a time to form a
mature ovum (or egg).
 Ovulation: On maturing, the follicle bursts and the ovum (or egg) shoots out of the
ovary.
 In a normal, healthy girl (or woman), ovulation takes place on the 14 th day of the
beginning of menstrual cycle of 28 days.
 This means that ovulation takes place in the middle of the menstrual cycle (because
14th day is the middle of 28 days).
  In human females (or girls), the ovaries start releasing ovum or egg (female gamete)
once every 28 days from the age of puberty.
 That is, in girls ovulation starts when they attain puberty.
 Before every ovulation, the inner lining of the uterus becomes thick and soft with lot
of blood capillaries (or blood vessels) in it.
 These changes in the uterus are necessary because in case the ovum (or egg) released
by the ovary gets fertilised by the sperm, then the uterus has to keep this fertilised
ovum (or egg) for further development and supply it with food and oxygen, etc., so
that it may grow into a baby in due course of time.
 If, however, a sperm is not available at the time of ovulation, then fertilisation of ovum
(or egg) does not take place.
 Since the ovum (or egg) is not fertilised, so the thick and soft uterus lining having lot
of blood capillaries in it is not required.

 The unfertilised ovum (or egg) dies within a day and the uterus lining also breaks
down.
 Since the thick and soft uterus lining contains a lot of blood vessels, so the breaking
(or disintegration) of the uterus lining produces blood along with other tissues.
 This blood and other tissues come out in the form of bleeding.
 Mensuration: The breakdown and removal of the inner, thick and soft lining of the
uterus along with its blood vessels in the form of vaginal bleeding.
 Since the process of menstruation in a woman occurs again and again after a fixed
period of 28 days (to 30 days), so it is also known as menstrual cycle.
 Menstruation occurs every 28 days because ovulation (release of ovum or egg by
ovary) occurs every 28 days.
 In everyday language, menstruation is called ‘periods’.

Menarche:
 The first menstruation (or menstrual flow) begins at puberty (when the girl or woman
is around 10 to 12 years of age).
 It is the beginning of the reproductive life of a girl (or woman).
 It is the time from which a girl (or woman) becomes capable of having a baby.
Menopause:
 Menstruation stops permanently when a woman reaches the age of about 45 to 50
years.
 With the permanent stoppage of menstruation, a woman loses her ability to bear
children.
 She becomes infertile.
 The permanent stoppage of menstruation (or periods) in a woman is called
menopause. Menopause occurs in women at the age of about 45 to 50 years.
 A woman stops ovulating at menopause and can no longer become pregnant.
BIRTH CONTROL
Importance:
 The population of our country is increasing rapidly day by day.
 Though our country has sufficient food resources but still many people do not get
sufficient food for their large families (having many children) due to poverty.
 So, every year it is becoming very difficult for our Government to provide sufficient
food, adequate clothing, good housing and proper education to every citizen of the
country.
 It is, therefore, very important for the couples (husbands and wives) who are in the
reproductive stage of their lives to control the size of their families by having fewer
children by practising family planning through birth control measures.
 Family planning enables a couple to decide on the number of children it wants to have
and when to have them.
 If a couple has less number of children, it can provide good food, good clothes, and
good education to each child.
 This will make the parents as well as the children happy.
 So, a small family is a happy family.
 It should be noted that having fewer children also keeps the mother in good health.
 We should remember that to keep the size of our family small by having less number
of children is in our own interest as well as in the interest of our Nation.
FAMILY PLANNING CAN BE DONE BY PRACTISING BIRTH CONTROL MEASURES.

BIRTH CONTROL METHODS

The prevention of pregnancy in women (by preventing fertilisation) is called contraception.
And any device or chemical (drug) which prevents pregnancy in woman is called a
contraceptive.
1. Natural Methods:
2. Barrier Methods
 In the barrier methods of preventing pregnancy, the physical devices such as condoms
and diaphragm (or cap) are used.
 Condoms are used by males (by putting them as a covering on the penis).
 Condom is called ‘nirodh’ in Hindi. Diaphragm (or cap) is used by females (by putting
it in the vagina to cover the cervix).
No other method of contraception provides protection against sexually transmitted diseases.

3. Chemical Methods

 In the chemical methods of preventing pregnancy, the females use two types of pills: oral
pills and vaginal pills, which are made of specific drugs.

4. Intra-Uterine Contraceptive Device (IUCD)

 The use of intrauterine contraceptive device called Copper-T is also very effective in
preventing pregnancy.
 A Copper-T is placed inside the uterus by a doctor or a trained nurse.
 The IUCD or Copper-T prevents the implantation of fertilised egg in the uterus.
  If a woman uses a Copper-T as a method of contraception for avoiding unwanted
pregnancies, then Copper-T cannot protect her from acquiring sexually transmitted
diseases (if her partner has such a disease).

5. Surgical Methods

Stop Female Foeticide:

 Surgical operations can also be used for the termination of pregnancies in women
particularly after eight weeks of conception.
 Such surgical termination of pregnancy (or abortion) is allowed by law only in certain
circumstances where the doctors decide that continuance of pregnancy can affect the
health of mother or of unborn child gravely.
 Some people, however, misuse the technique of surgical termination of pregnancy for
ulterior motive to get rid of female foetus (or unborn girl child).
 In order to have a male child (son), some misguided people in our country get the sex
of their unborn child determined by ultrasound technique (though it is illegal to do
so), and if it is a female foetus, they get it removed by surgery.
 This killing of the unborn girl child is called female foeticide.
  Female foeticide is reducing the number of girls drastically in some societies of our
country.
 For a healthy society, the male-female sex ratio must be maintained at almost the
same level.
Sexually Transmitted Diseases (STD)

The diseases which are spread by sexual contact with an infected person are called sexually
transmitted diseases (or STD).

Thus, a healthy person can get STD by making sexual contact with an infected person.
Some of the common sexually transmitted diseases are:
Gonorrhoea and syphilis
 These are caused by bacteria.
 The bacteria which cause these diseases spread through sexual contact with an
infected person.
 The most common symptoms of the these sexually transmitted diseases are burning
sensation at urination, passing of urethral discharge (containing pus) and sores in the
genitals. Gonorrhoea and syphilis are curable diseases.
AIDS disease is caused by a virus called HIV (Human Immunodeficiency Virus).
 AIDS damages the body’s immune system so that the body becomes weak and cannot
protect itself against infection.
 So, AIDS is a very dangerous disease which leads to death. No definite cure has been
found for the AIDS disease so far.
 4. HEREDITY AND EVOLUTION
CHARACTERS or TRAITS: A recognizable feature of a human being like height, complexion,
shape of hair, color of eyes, and shape of nose and chin, etc.,
HEREDITY: The transmission of characters (or traits) from the parents to their offspring’s.
VARIATIONS: The differences in the characters (or traits) among the individuals of a species.
 It is a necessity for organic evolution.
 It increases the chances of its survival in a changing environment.
 Eg: The free earlobes and attached earlobes are the two variations.
The number of variations produced during sexual reproduction is very large then asexual
reproduction.
Significance of variation shows up only if it continues to be inherited by the offspring for
several generations.
CHROMOSOME AND GENES:
Chromosome:
 It is a thread-like structure in the nucleus of a cell formed of DNA which carries the
genes.
 Different organisms have different number of chromosomes in their nuclei.

Gene:
 It is the functional unit of heredity.
 Every gene control one or several characteristic features in living organisms.
 It is a unit of DNA on a chromosome which governs the synthesis of one protein that
controls a specific characteristic of an organism.
 They work in pairs.
 Genes for controlling the same characteristic of an organism can be of two types:

DOMINENT GENE RECESSIVE GENE

 The gene which decides the appearance of The gene which can decide the
an organism even in the presence of an appearance of an organism only in the
alternative gene. presence of another identical gene.
It dominates the recessive gene for the A single recessive gene cannot decide the
same characteristic on the other appearance of an organism.
chromosome of the pair.
It is represented by capital letter It is represented by small letter
In pea plants dominant gene for tallness is In pea plants recessive gene for
T dwarfness is t

DIFFERENCES BETWEEN GENOTYPE AND PHENOTYPE

GENOTYPE PHENOTYPE
It is the genetic constitution of an The characters of an organism which are
organism. visible.
It completely depends on the gene It depends on the genotype and
sequences. environmental factors.
It consists of all hereditary information that It only consists of expressed genes and
is the expressed and suppressed genes. determined by its genotype
It is always a pair of letters such as TT, Tt or Tall or dwarf are phenotypes. Genotype
tt TT or Tt results in a tall phenotype and
genotype tt results in a dwarf phenotype

First filial generation or F1 generation:

 It is the progeny produced when two parents cross (or breed).

 Mother and father are parental generation and the children are F1 generation.
Second filial generation or F2 generation:

 When the first-generation progeny cross (or breed) among themselves to produce
second generation progeny.
 The generation produced by crossing two F1 progeny.
 The grandchildren are F2 generation.
GREGOR MENDEL:

He was the first scientist to make a systematic study of patterns of inheritance which involved
the transfer of characteristics from parents to progeny.
He chose pea plants for studying inheritance because pea plants had a number of clear-cut
differences which were easy to tell apart.

HYBRID:
A new form of plant resulting from a cross (or breeding) of different varieties of a plant.

MONOHYBRID CROSS DIHYBRID CROSS

Inheritance of one pair of contrasting Inheritance of two pairs of contrasting
characteristics. characteristics.
Tallness and dwarfness of the pea plants Round-yellow seeds and wrinkled-green
seeds

RULES FOR THE INHERITANCE OF TRAITS: MENDEL’S CONTRIBUTION

Inheritance is the transmission of genetically controlled characteristics (or traits) from one
generation to the next.

Monohybrid Inheritance and the Law of Segregation:

 He first crossed pure-bred tall pea plants with pure-bred dwarf pea plants and found
that only tall pea plants were produced in the first generation of progeny.
 He then crossed the tall pea plants of the first generation (F1 generation) and found
that tall plants and dwarf plants were obtained in the second generation (or F2
generation) in the ratio of 3 : 1 called monohybrid ratio.
 He noted that the dwarf trait of the parent pea plant which had seemingly disappeared
in the first-generation progeny, reappeared in the second generation.
 He said that the trait of dwarfness of one of the parent pea plants had not been lost,
it was merely concealed or suppressed in the first generation to reemerge in the
second generation.
 He called the repressed trait of dwarfness as recessive trait and the expressed trait of
tallness as the dominant trait.

MENDEL’S FIRST LAW OF INHERITANCE

Law of Dominance: When two alternative forms of character are present in an individual, only
one form expresses itself in the F1 progeny and is called the dominant trait, while the form
that does not express itself is called the recessive trait.

Law of Segregation: The alleles do not show any blending and are recovered as such in the F2
generation, though one of these is not shown in the F1 generation.

Dihybrid Inheritance and the Law of Independent Assortment

It involves the inheritance of two pairs of contrasting characteristics (traits) at the same time.
The two pairs of contrasting characteristics chosen by him were shape and color of seeds:
round-yellow seeds and wrinkled-green seeds.
 He first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea
plants having wrinkled-green seeds and found that only round-yellow seeds were
produced in the first generation.
 No wrinkled-green seeds were obtained in the F1 generation.
 He concluded that round shape and yellow color of the seeds were dominant traits
over the wrinkled shape and green color of the seeds.
 When the F1 generation pea plants having round-yellow seeds were cross-bred by
self-pollination.
 Then four types of seeds having different combinations of shape and color were
obtained in second generation or F2 generation.
 These were round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds.
 The phenotypic ratio of different type of seeds can be written as: 9:3:3:1.
 He concluded that though the two pairs of original characteristics (seed shape and
color) combine in the F1 generation, but they separate and behave independently in
subsequent generations.

MENDEL’S SECOND LAW OF INHERITANCE:

When two pairs of traits are recombined, segregation of one pair of characters is independent
of the other pairs of characters during gamete formation.

HOW ARE CHARACTERISTICS (OR TRAITS) TRANSMITTED TO PROGENY

 Genes are responsible for the characteristic features (or traits) of an organism: plant
or animal.
 The characteristics or traits of parents are transmitted to their progeny (offsprings)
through genes present on their chromosomes during the process of sexual
reproduction.
 Genes work in pairs.
 There is a pair of genes for each characteristic of an organism (one is dominant gene,
and the other is recessive gene).
 Each parent possesses a pair of genes for each characteristic on a pair of
chromosomes.
 However, each parent passes only one of the two genes of the pair for each
characteristic to its progeny through gametes.
 The male gamete and female gamete carry one gene for each characteristic from the
gene pairs of parents (which are located on the pair of chromosomes).
 But when a male gamete fuses with a female gamete during fertilization, they make a
new cell called zygote with a full set of genes (on a full set of chromosomes).
 This zygote grows and develops to form a new organism having characteristics (or
traits) from both the parents which it has inherited through genes.
 The two genes (or pair of genes) responsible for a particular characteristic are always
present on the corresponding positions of the pair of chromosomes.
 The genes for tallness and dwarfness are not to be considered two different genes.
 They are just the two forms of the same gene which controls only one characteristic
feature of a plant: length of its stem.
HOW BLOOD GROUPS ARE INHERITED
 A person has one of the four blood groups: A, B, AB or O
 The gene which controls the blood groups is represented by the letter I.
 This gene has three different forms (called alleles) which are represented as IA, IB and
I O.
 The genes IA and IB show no dominance over each other, so they are codominant.
 The genes IA and IB both are dominant over the gene IO. (Blood gene IO is recessive).

SEX DETERMINATION
A person can have a male sex or a female sex.
The process by which the sex of a person is determined is called sex determination.
Genetics is involved in the determination of the sex of a person.
The chromosomes which determine the sex of a person are called sex chromosomes.
There are two types of sex chromosomes, one is called X chromosome and the other is called
Y chromosome.
 The human male (man or father) has one X chromosome and one Y chromosome (XY).
 The human female (woman or mother) has two X chromosomes (XX).

The sex chromosome contributed by father (husband) decides the sex of the baby which the
mother (wife) will give birth.

In some of the animals, sex determination is also controlled by the environmental factors.
 In some reptiles, the temperature at which the fertilized egg is incubated before
hatching, plays a role in determining the sex of the offspring.
 It has been found that in a turtle (Chrysema picta), high incubation temperature leads
to the development of female offspring’s (or female progeny).
 In the case of a lizard (Agama agama), high incubation temperature results in male
offspring’s (or male progeny).
 In some animals, such as snails, individuals can change sex, indicating that sex is not
determined genetically in such animals.

ACQUIRED AND INHERITED TRAITS

 5. OUR ENVIRONMENT
The physical and biological world where we live is called our environment.
The environment includes our physical surroundings like air, water bodies, soil and all the
organisms such as plants, animals, human beings and micro-organisms like bacteria and fungi
(called decomposers).

ECOSYSTEM
It was first coined by A.G.Tansley, an English botanist, in 1935.
It is a self-contained unit of living things (plants, animals and decomposers), and their non-
living environment (soil, air and water).
It needs only the input of sunlight energy for its functioning.

Eg: Grassland (meadow), Forest, Desert, Mountain, Pond, Lake, River and Sea.
The structure of an ecosystem can be split into two main components, namely:

ABIOTIC COMPONENTS
These are the non-living component of an ecosystem.
It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude, turbidity,
etc.

BIOTIC COMPONENTS
It refer to all living components in an ecosystem.
Based on nutrition, biotic components can be categorised into autotrophs, heterotrophs and
saprotrophs (or decomposers).
PRODUCERS:
It include all autotrophs such as plants.
Called autotrophs as they can produce food through the process of photosynthesis.
All other organisms higher up on the food chain rely on producers for food.
CONSUMERS OR HETEROTROPHS:
These are organisms that depend on other organisms for food and further classified into:
 Primary consumers (herbivores):
o Animals which eat only plants.
o They rely on producers for food.
o Eg: Cow, Buffalo, Goat, and Hippopotamus.
 Secondary consumers:
o They depend on primary consumers or herbivores for energy.
o They can either be carnivores or omnivores.
o Eg: Frog, Lizard and Bird.
 Tertiary consumers:
o These are organisms that depend on secondary consumers or small carnivores
for food.
o They can also be carnivores or omnivores.
o Eg: Lion, Tiger and Hawk.

 Quaternary consumers:
o These are present in some food chains.
o These organisms prey on tertiary consumers for energy.
o They are usually at the top of a food chain as they have no natural predators.
o Planktons:
 These are very minute or microscopic organisms freely floating on the
surface of water in a pond, lake, river or ocean.
 They provide food for many fish and other aquatic animals
 Planktons are of two types :
 Phytoplanktons:
 These are microscopic aquatic plants seen floating on water.
 Eg: free-floating algae
 They are capable of producing food by photosynthesis.
 Zooplanktons:
 The microscopic aquatic animals freely floating on water.
  Eg: freely-floating protozoa. a very, very small fish.

DECOMPOSERS:
Def: 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.
They include saprophytes such as fungi and bacteria.

They directly thrive on the dead and decaying organic matter.

They are essential for the ecosystem as they help in recycling nutrients to be reused by plants.

FUNCTIONS OF ECOSYSTEM

 It regulates the essential ecological processes, supports life systems and renders
stability.
 It is also responsible for the cycling of nutrients between biotic and abiotic
components.
 It maintains a balance among the various trophic levels in the ecosystem.
 It cycles the minerals through the biosphere.
 The abiotic components help in the synthesis of organic components that involve the
exchange of energy.
So the functional units of an ecosystem or functional components in an ecosystem are:
 Productivity – It refers to the rate of biomass production.
 Energy flow – It is the sequential process through which energy flows from one trophic
level to another. The energy captured from the sun flows from producers to
consumers and then to decomposers and finally back to the environment.
  Decomposition – It is the process of breakdown of dead organic material. The top-soil
is the major site for decomposition.
 Nutrient cycling – In an ecosystem nutrients are consumed and recycled back in
various forms for the utilisation by various organisms.

FOOD CHAIN
The sequence of transfers of matter and energy in the form of food from organism to
organism.

In simple words, it is a list of organisms showing who eats whom.

It represents a single directional (or unidirectional) transfer of energy.
The study of food chains in an area or habitat helps us in knowing various interactions among
the different organisms and also their interdependence.

FOOD WEB
Def: The inter-connected food chains operating in an ecosystem which establish a network of
relationships between various species.
In simple words, the network of a large number of food chains existing in an ecosystem.
TROPHIC LEVELS
 The various steps in a food chain at which the transfer of food or energy takes place.
 In a food chain, each step representing an organism forms a trophic level.
 In most simple terms, trophic level means feeding level of the organism.
 The plants are producers or autotrophs) and constitute the first trophic level. They fix
up the sun’s energy and make it available for consumers (or heterotrophs).
 Herbivores (which feed upon plants) constitute the second trophic level.
 Carnivores (that feed upon herbivores) constitute the third trophic level.
 Large carnivores or Top carnivores (which feed upon small carnivores), constitute the
fourth trophic level.

The trophic levels in a food chain can also be represented by pyramid of numbers.

EFFECT OF MAN'S ACTIVITIES ON THE ECOSYSTEM

The shortening of food chains due to man's activities like hunting leads to an imbalance in the
functioning of an ecosystem and ultimately in the functioning of the whole biosphere.
The formation of Sahara Desert:
 It is an example of the ill effect of man's activities on the delicately balanced
ecosystem.
 When the Romans started capturing lions, the population of lions in the forest was
reduced.
 Lion is a predator which kills the herbivorous animals like deer, sheep, goat, buffalo,
etc.
 Now, since the population of predator lion decreased, there was no one to kill the
herbivorous animals.
 Due to this the population of herbivorous animals increased rapidly.
 The large population of these herbivorous animals ate up all the vegetation in that
region, turning the lush-green forests into vast desert called Sahara Desert.
 TRANSFER OF ENERGY IN FOOD CHAINS
The food chain in a community actually represents a stepwise transfer of food and the energy
contained in food.
The flow of energy in the ecosystem is said to be unidirectional because the energy lost as
heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.
The flow of materials like water, carbon and nitrogen, etc., in the ecosystem is cyclic.
 The food and energy enter the living components of the ecosystem through the
process of photosynthesis.
 On an average, about 1% of the sun's energy falling on the leaves is used by the plants
in the process of photosynthesis and stored as chemical energy of food.
 Energy is not created in the ecosystem.
 Energy is only converted from one form to another form.
 There is a continuous transfer of energy from one trophic level of organisms to the
next trophic level in a food chain
 At each trophic level of organisms, some of the energy is utilized by the organisms for
their metabolic activities like respiration and for growth.
 A part of the energy at each trophic level (like producers, herbivores and carnivores)
is utilized for the functioning of decomposers.
 There is a loss of energy at each energy transfer in various trophic levels of organisms
which goes into the environment and remains unutilized.
 When we move from the first trophic level of producers (plants) to second trophic
level of herbivores and third trophic level of carnivores the amount of energy available
gradually decreases.
 As at each trophic level, energy is lost as heat energy which goes into the environment.
 TEN PER CENT LAW
Given by Lindeman in the year 1942.
Only 10 per cent of the energy entering a particular trophic level of organisms is available for
transfer to the next higher trophic level.
Food chains generally consist of three or four steps (three or four organisms) because after
that the energy available for the next organism will be so small that it will be insufficient to
sustain the life of that organism.
There are, however, some food chains containing five organisms but there are rarely more
than five organisms in a food chain.

BIO-CONCENTRATION OF PESTICIDES:
The accumulation of harmful chemicals such as pesticides in the living organisms like plants,
animals and humans unknowingly, through the food chain.

The pesticides enter the food chain at the producer level and in the process of transfer of
food through food chains these harmful chemicals get concentrated at each trophic level.

Biological magnification: The increase in concentration of harmful chemical substances like

pesticides in the body of living organisms at each trophic level of a food chain.
Dichlorodiphenyltrichloroethane (DDT) is an insecticide used in agriculture. People are most
likely to be exposed to DDT from foods, including meat, fish, and dairy products. This led to
toxic effects in humans.
DEPLETION OF OZONE LAYER
The ozone layer is a region in the earth’s stratosphere that contains high concentrations of
ozone and protects the earth from the harmful ultraviolet radiations of the sun.
Ozone (O3)
 It is a molecule formed by three atoms of oxygen.
 It is a deadly poison.
 In the higher levels of the atmosphere, ozone shields the surface of the earth from
ultraviolet (UV) radiation from the Sun.
 This radiation is highly damaging to organisms, as it is known to cause skin cancer in
human beings
 It at the higher levels of the atmosphere is a product of UV radiation acting on oxygen
(O2) molecule.
 The higher energy UV radiations split apart some molecular oxygen (O 2) into free
oxygen (O) atoms.
 These atoms then combine with the molecular oxygen to form ozone as shown—

Def: It is the gradual thinning of the earth’s ozone layer in the upper atmosphere caused due
to the release of chemical compounds containing gaseous bromine or chlorine from industries
or other human activities.
The depletion of ozone layer is due to the use of chemicals called chlorofluorocarbons.
Chlorofluorocarbons (CFC) are the chemicals which are widely used in refrigeration
(refrigerators and air conditioners) as a coolant, in fire extinguishers and in aerosol sprayers.
 MANAGING THE GARBAGE WE PRODUCE
The household wastes (or rubbish) is called garbage.
Some of the garbage is biodegradable whereas a major part of it is non-biodegradable.
If the household garbage or waste is not disposed of properly, it can pollute the environment
like soil, water and air.
Disposal of waste means to get rid of waste in a scientific way.
There are different methods which depends on the nature of the waste.

RECYCLING
 The solid wastes like paper, plastics and metals, etc., are recycled.
 Waste paper is sent to paper mills where it is reprocessed to form new paper once
again.
 Broken plastic articles like plastic bags, buckets, bowls, cups, plates, etc., are sent to
plastic processing factories where they are melted and remoulded to make new
articles.
 Waste metal articles are sent to metal industries where they are melted and recycled
as solid metal for various purposes.

PREPARATION OF COMPOST
 Biodegradable domestic wastes can be converted into compost by burying in a pit dug
into ground, and used as manure.
 Left-over food, fruit and vegetable peels, and leaves of potted plants, etc.

INCINERATION
 It means reducing to ashes.
 Def: The burning of a substance at high temperature (of more than 1000°C) to form
ash.
 It is used to destroy household waste, chemical waste and biological waste (like that
from hospitals).
  It greatly reduces the volume of the waste and left behind which can be disposed of
by landfill.
 It is carried out in an incinerator (which is a kind of furnace).
 All the organic matter present in waste is removed as carbon dioxide and water
vapour.

LANDFILL

 Def: The disposal of wastes by putting it in low-lying areas of ground and covering it
with earth.
 Most of the solid waste in urban areas (which cannot be disposed of by other
methods) is dumped in low-lying areas of ground and covered with earth to level the
uneven ground.
 A big landfill site can be used to dispose of waste materials (or garbage) for a
considerable time.

SEWAGE TREATMENT

 Def: The dirty drain water containing urine and faeces which is carried from our homes
by the underground pipes (called sewers).
  If untreated sewage is dumped into a river, it can pollute the river water.
 It is disposed of by treating it at the sewage treatment plant (or sewage works).
 The treatment of sewage produces clean water which is discharged into the river.
 The organic matter present in sewage is digested in the digesters of sewage treatment
plant to produce sewage gas (biogas) and manure.
TEA VENDORS IN TRAIN:
 Tea in trains was served in plastic glasses which had to be returned to the vendor and
it was not a hygienic.
 Later on disposable plastic cups were introduced, it was hygienic but the disposal of
millions of plastic cups on daily basis posed a big problem.
 Sometime back kulhads (disposable cups made of clay) led to the loss of fertile top soil
from fields so it was also discontinued.
 These days, disposable paper cups are being used.
 The use of disposable paper cups has the following advantages over the plastic cups:
o Paper cups:
 These are biodegradable.
 Disposed of by burning without causing much air pollution.
o Plastic cups
 These are non-biodegradable.
 Burning produces poisonous gases which cause too much air pollution.
BIODEGRADABLE AND NON-BIODEGRADABLE WASTES
1. LIFE PROCESSES
2 CONTROL AND COORDINATION
3. HOW DO ORGANISMS REPRODUCE
4 HEREDITY
5. OUR ENVIRONMENT