The document discusses different modes of nutrition in living organisms. It describes heterotrophic nutrition where organisms depend on other organisms for food. The three types of heterotrophic nutrition are parasitic, saprophytic, and holozoic. Parasitic organisms harm their hosts, saprophytes feed on dead and decaying matter, and holozoic organisms ingest complex foods. Holozoic nutrition involves ingestion, digestion, absorption, assimilation, and egestion. Examples of different organisms and their modes of nutrition are provided, including the human digestive system.

1. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
Heterotopic mode of nutrition: - The mode of nutrition in which living Organism depends on other living
Organism for the food is called heterotrophic mode of nutrition.
Living Organism depends on other living Organism for their food are called heterotrophs.
Heterotopic mode of nutrition great into three types;
1. Parasitic mode of nutrition
2. Saprophytic mode of nutrition
3. holozoic mode of nutrition
(1) Parasitic mode of nutrition: - The mode of nutrition in which living Organism harm other living
Organism and takes their food is called parasitic mold of nutrition.
 Living Organism lives which harm other living Organism to take the food are called parasite.
 In parasitic mode of nutrition, living Organism depends on other plants or animals for their
nourishment and harm them.
 Such dependent living Organism are called parasites and the one on which parasite depends are
called the host.
 A parasitic plant claims on the host plants from which they get the food.
 The host plant does not get any benefit from the parasite.
 Some examples of the parasite are Cuscuta, lice, hookworm, tapeworm, leeches, ticks, etc.
 Cuscuta is a plant that does not have chlorophyll, it sucks the food and water from the host plant
through adventitious roots.
 Cuscuta is there for the complete parasite.
 Orchid is a partial parasite plant, as it only suck water and prepare their food by photosynthesis.
 Lice, hookworm, tapeworm, leeches, ticks and disease causing microorganisms (Pathogens) are also
called parasites.
Insectivorous Plants: -
 The insectivorous mode of nutrition is observed in plants like Pitcher plant and the Venus fly trap.
 These plants normally do photosynthesis but also trap insects and takes food, so they are partial
autotrophic and partial heterotrophic mode of nutrition.
(2) Saprophytic mode & saprotrophs: -
 Mode of nutrition in which organisms obtain their nutrition from dead and decaying plant and
animal parts, organic matters is called saprophytic mod of nutrition.
 The organism which exhibit saprophytic mode of nutrition are called saprotrophs.
 Saprotrophs secrete strong digestive juice into dead and decaying matter to decompose them absorb
nutrients from them.
 Example of saprotrophs are Bread mold, mushroom, yeasts ( All fungi) and some bacteria.
 These are also called as decomposer, as they decompose organic matter and take their food.
 They convert organic matter into inorganic matter and add them in soil which can be absorbed by
plants through roots.
Symbiotic Relation: - The relation between two living organisms to take their food by helping each other is
called symbiotic relation.

2. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
 In this mode of nutrition there is a close association between two different living organisms in such
ways that both are benefited.
For example, Lichen, algae live in association with fungi, in which algae provides food to fungi prepared by
photosynthesis, while fungi give shelter and water to algae, and both are benefited.
(3) Holozoic mode of nutrition: - - The mode of nutrition in which all animal takes in complex solid food
material is called holozoic mode of nutrition.
Examples: - All animals including vertebrates and invertebrates.
 Holozoic mode equation contains 5 step.
I. Ingestion: - Take in complex organic food through mouth or opening of gut.
II. Digestion: - Change of complex food into simpler substance by the action of enzymes.
III. Absorption: - Passing simpler soluble nutrients into the blood.
IV. Assimilation: - Utilization of absorbed food for various metabolic process and its transportation.
V. Egation: - The removal of undigested food from the body.
 Depending upon the food habits animals are divided into following three categories;
A. Herbivorous animals: - The animal that depends only on green plants examples of goat, cow, deer,
rabbit, etc.
B. Carnivorous animal: - The animals that eat only the flesh of other animal Examples Lion, Tigre, etc
C. Omnivorous animal: - The animals that eat both plant as well as animal part as their food are
known as omnivorous animal. examples are human, rat, cat, dog, etc
Nutrition in Amoeba: - Nutrition in unicellular Organism like amoeba.
 Amoeba is an omnivorous animal having unicellular structure.
 It feeds upon microscopic organisms like bacteria, paramecium, diatoms, algae, dead organic matter, etc.
Nutrition in Amoeba involves following 5 steps;
I. Ingestion: -
 Amoeba do not have opening of gut or mouth, so it may take food from any point of the body
surface.
 Pseudopodia helps in trapping food particles,
 The opening of food cap gradually narrower and narrower, and finally closes.
 So food is finally enveloped and taken inside food vacuoles along with small drop of water.
II. Digestion: -
 Lysosomes from cytoplasm enters in food and completes digestion with the help of strong
digestive juice.
 In this process complex and non-diffusible nutrients change into simple diffusible nutrients.
 Initially the medium inside the food vacuole is acidic but later it becomes alkaline as like
elementary canal of the human.
III. Absorption: -
 In absorption the diffusible nutrients pass through the vacuolar membrane into the cytoplasm by
the diffusion to all other parts of cell.
 The size of food vacuole gradually decreases and disappear at last.
IV. Assimilation: -
 Absorbed nutrients are oxidised to from energy and utilization of absorbed food for various
metabolic process and its transportation.
 In cytoplasm various nutrients are used to synthesis components necessary for nourishment,
which is called biogenesis.
V. Egation: - The removal of undigested food from the body.

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 As amoeba has no opening or anus to remove undigested food from body parts.
 Undigested food present in food vacuole is directly removed by opening it outside without
allowing them to entering into cytoplasm.
Nutrition human
 Human is an omnivorous animal as they eat both plant and animal parts for their nutrition requirement.
 It is holozoic mode of nutrition.
 In holozoic mode of nutrition have 4 steps;
 Ingestion: - To take food in mouth with the help of hand
 Digestion : - The process of converting of complex food in to simple food
 Absorption : - Absorption of digested food in to blood.
 Assimilation :- Packaging and transferring of absorbed food
 Egestion: - Removalof undigested food
 In human there is a well-developed human digestive system, also called elementary canal or gut.
Human elementary canal includes following parts
1. Buccal cavity / Mouth ( Teeth, Tongue AND Salivary glands)
2. Oesophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum
7. Anus
There are also 2 associated glands 1. Liver and 2. Pancreas

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I. MOUTH: -
 Mouth or a buccal cavity have 32 teeth. tongue and group of salivary glands.
 Normally human take the food with the help of hand and put it inside buccal cavity (Ingestion)
 Teeth : - There are 4 types of teeth
 Incisors – Our incisors are 8 teeth in the front centre of our mouth, used for cutting the food.
 Canines – Next teeth, total 4, used for tear and wear food.
 Premolars and Molars – Used for chewing and grinding food.
 With the help of this different teeth human chews the food and grind it in small pieces.
 Tongue also help in a chewing and grinding
 Salivary glands secret saliva which make food soft.
 Salivary glands also contain salivary amylase which starts the first part of chemical
digestion by converting carbohydrate into sugar. (Starch into sugar)
II. Oesophagus: - Soft chewed food will enter into Oesophagus through a common passage pharynx,
where a flap like structure epiglottis prevent entry of food inside windpipe (TRACHEA).
 Oesophagus it is a strong muscular tube like structure which pushes the food towards stomach by
rhythmic contraction and expansion of its muscles, which is also called Peristaltic movement.
 The sphincter valve allows the entry of food inside the stomach.
III. Stomach
 Stomach is the widest part of human digestive system and flatten “U” or “J” shaped.
 As soon as the food enters into stomach the strong inner wall of stomach releases the 3 types of
secretions; 1 HCl 2 mucus 3 pepsin
 Role of HCL in human digestion
 1.2 pH strong at HCl kill bacteria presence insight food and makes it germ free.
 HCl also digests the food particles and makes them soft and small.
 HCl provides acidic condition for pepsin to start digestion of protein.
 Role of mucus
 Mucus made the food watery
 It also covers the inner wall of stomach and protect it from irritating action of acid (HCl)
 Pepsin
 The enzyme pepsin starts digestion of protein under the acidic condition created by HCl.
 Food remain inside the stomach 3 to 4 hour and inner wall of stomach will churn the food and make it
homogeneous acidic liquid.
 If a person suffers from acidity if;

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 He over eats food
 He eats too spicy food
 He does not eat food at proper time.
 The acidity can be treated by mild base like baking soda, milk of magnesia, [ Mg(OH) 2 ], which
neutralised the acid and give relief from irritation.
 After 3 to 4 hours the lower sphincter valve of stomach release the food into the small intestine.
IV. Small intestine
 The most crucial part in a gut, where the most of the digestion and absorption process is carried out is
small intestine.
 It is almost 6-metre-long coiled structure in our abdominal region.
 There are 2 associated glands which help in the digestion of food, namely;
(1) Liver and (2) Pancreas
 Liver
 It is the largest gland in our body located beside stomach, just below diaphragm in abdominal cavity.
 It’s a secrets Bile juice and bile salt, which was temporarily stored in gall bladder.
 When food is present in stomach, the LIVER starts the secretion of bile juice and bile salt, as soon as
the food enters inside the small intestine the gall bladder released bile juice and bile salt and mix it
with the food
 Bile juice
 bile juice is an alkali liquid secreted by liver which neutralise the acid presence inside the food which
enter inside the small intestine and protect the small intestine from its irritating action.
 Bile salt
 Bile salt converts large globules of fat into small globules which makes fat digestion easy, this is
called emulsify.
 Pancreas
 Pancreas is a cream colour leaf shape gland present just below stomach which secret strong digestive
juice and+ completes the digestion of food.
 SECRETION OF PANCREAS
 Pancreatic Amylase -
 Pancreatic Amylase completes the digestion of Carbohydrate and convert them into GLUCOSE.
 Trypsin: -
 Trypsin enzyme completes the digestion of protein and convert them into AMINO ACID.
 Lipase: -
 Lipase complete the digestion of fat and convert them into FATTY ACID AND GLYCEROL.
ABSORPTION OF DEGESTED FOOD.
 The inner lining of the small intestine has many finger-like projections called Villia, which increases the
surface area for DIGESTION & ABSORPTION digested food.
 It also reduces the speed of food.
 The Villia provide the site of absorption of digested food into blood through extensive network of
smaller blood capillaries present on them through diffusion.
ASSIMILATION
 Absorbed food is send to each and every cell of the body, where it is utilized.

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 Digested carbohydrates is absorbed in form of Glucose, is converted in to Sucrose, the only soluble
form of sugar and send to various parts of body for further uses.
 Undigested food material is send to large intestine.
Appendix
 Appendix is vestigial organ in human body which do not have any use.
 When some food particles stuck inside appendix, it will create poisonous effect so it needs to be remove
by operation.
 What is difference between digestive system of herbivorous animal and human ?
 Herbivorous animals eat only plant parts while human eat plant as well as animal parts for that food. The
carnivorous animals eat only animal flesh.
 The plant cell contains cell wall which is made-up of a complex carbohydrate called cellulose, cellulose
is very difficult to digest, so herbivorous animals have;
i. rumen, pouch to store unchewed food.
ii. Long small intestine, almost 7.5 m while human have 6 m long small intestine. And
iii. have 7.5 feet long appendix to digest cellulose.
Large intestine
 Large intestine is wider and 1.5-metre-long divided into 3 part, upward column transverse column and
downward column.
 In large intestine excess water and salt is absorbed from undigested food and convert into faecal matter
which is temporarily stored in a rectum.
 By opening a Sphincter valve of anus and release faecal matter outside their body.
Respiration: -The process of breakdown of nutrients to release energy in living organisms is called
respiration.
 As respiration release energy, it is the only catabolic process occurs in any living organism.
 It can be divided in to two parts;
(1) Chemical process: - The breakdown of nutrients.
(2) Physical process: - Exchange of gases necessary for respiration. The process of getting oxygen
necessary to break nutrients is physical process, in human it is called as breathing.
(1) Chemical process: - The chemical breakdown of nutrients to release energy by living organisms is
chemical part of respiration.
 As actual breakdown of nutrients occurs inside the cell, it is also called Cellular respiration.
 Cellular respiration has two types based on presence of oxygen;
(1) Aerobic respiration: - The process in which nutrients is breakdown in living organisms to release
energy in presence of oxygen is called aerobic respiration.
 The most of living organisms get energy by aerobic respiration.
 In this process the glucose is breakdown in absence of oxygen into two molecules of Pyruvate in side
cytoplasm of cell.
 Then pyruvate enters inside mitochondria, where it is further broken down in presence of oxygen into
CO2, H2O and energy is released.
(2) Anaerobic respiration: - The food is oxidised without using molecule of oxygen, this respiration is
called anaerobic respiration.
 The process in which nutrients is breakdown in living organisms to release energy in absence of oxygen
is called anaerobic respiration.

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 Very few living organisms get energy by this process, eg. Fungi, few bacteria, animal muscles during
heavy exercise.
 Anaerobic respiration is performed in two different ways by various living organisms.
1. Fermentation: - In cytoplasm of yeast cell, in absence of oxygen, glucose is breakdown into
pyruvate. Further this this pyruvate is breakdown into ethanol, in absence of oxygen along with CO2
and 2 ATP energy.
 As produced Ethanol also has lot of commercial value this type of respiration is also called
commercial mode of respiration.
2. When animal is doing heavy exercise, it need lots of oxygen for respiration, if sufficient amount of
oxygen is not supplied, these animal muscles will start anaerobic respiration.
 In this process pyruvate released during break down of glucose in cytoplasm, will be further
broke into lactic acid in cytoplasm and release 2 ATP energy.
 Released Lactic acid obstructs, contraction and relaxation of muscles and at one stage it will
create cramp in muscles.
 This cramp can be relieved by;
I. Hot water bath
II. Rest and
III. Oil massage by soft to that muscles.
ATP: Adenosine Tri Phosphate
 When inorganic phosphate molecules combine with organic Adino sine required lot of energy, so break
down of the same release energy, which can be used by living organisms.
 One mole of ATP release 30.5 KJ energy.
 It is Energy currency for all living organisms.
 Types of cellular Respiration
 Breakdown of Glucose by various pathway Aerobic and anaerobic respiration.
Human Circulatory System
The human body is a complex machine, requiring many processes to function efficiently. To keep these
crucial processes running without any hitches, vital elements and components need to be delivered to the
various parts of the body. This role of transportation is undertaken by the human circulatory system, moving
essential nutrients and minerals throughout the body and metabolic waste products away from the body.

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Human Circulatory System: -The human circulatory system consists of a network of arteries, veins, and
capillaries, with the heart pumping blood through it. Its primary role is to provide essential nutrients, minerals,
and hormones to various parts of the body.
Alternatively, the circulatory system is also responsible for collecting metabolic waste and toxins from
the cells and tissues to be purified or expelled from the body.
Organs of Circulatory System
The human circulatory system comprises 2 main systems;
(1) Blood circulatory system
(2) Lymphatic system
Blood circulatory System is made up of three main organs that have specific roles and functions. The vital
circulatory system organs include:
I. Heart II. Blood III. Blood Vessels
Heart Size - 5 × 3.5 inches Colour – Pink Shape – Conical Weight - 300 gm.
Position-It is situated in the thoracic cavity, between the lungs.
• Its triangular, superior-broad portion is tilted slightly towards the right side, its lower narrow portion is
tilted towards the left side.
• Heart is enclosed from all the sides by an envelope of two membranes called pericardial membranes.
• The narrow space in between these two membranes is called the pericardial cavity. Fluid is present in
this cavity, called pericardial fluid.
 Pericardial fluid prevents the heart from external jerks.
 It reduces the friction during contraction.
 The human heart is divisible into four chambers.
 The upper two chambers are atriums (atria) while the lower two chambers are called ventricles.
The External Structure of Heart
• Parts of Lower chamber of the heart is smaller and its walls are thin.
• Parts of Lower chamber is broad and muscular.
• Ventricles have a thicker wall than atriums. Internal Structure of Human Heart
• Partition between right and left chambers of heart is known as septum.
a. Right Atrium
• The right atrium has the openings of the superior vena cava, inferior vena cava.
• Deoxygenated blood from the veins of the head, neck and upper limbs enters the right atrium by superior
vena cava and from the rest of the body and lower limbs by the inferior vena cava.
• The coronary sinus, which drains deoxygenated blood from the heart muscle.
• From the right atrium blood passes into the right ventricle through a tricuspid valve.
b. Right Ventricle
• Blood leaves the right ventricle through the pulmonary artery. It is guarded by a semilunar valve.
• This artery further divides into right and left pulmonary arteries entering into the two lungs where they
further branch into pulmonary capillaries in alveoli.
c. Left Atrium (Atrium)
• This chamber receives pulmonary veins from each lung from where they bring oxygenated blood.
• The left atrium empties its blood into the left ventricle through a mitral or bicuspid valve.
d. Left Ventricle:
• Blood leaves the left ventricle by the large, main artery of the body called the aorta.

9. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
• The opening from the left ventricle into the aorta is guarded by the aortic semilunar valve.
The Internal Structure of the Heart
Working of the heart
• The heart of the human works like a pump.
• Pure oxygenated blood enters the left atrium from lungs through pulmonary veins.
• The deoxygenated blood from various parts of the body enters the right atrium through veins and
capillaries.
• The two atriums contract simultaneously so the oxygenated blood from the left atrium to the left ventricle
and deoxygenated blood from the right atrium is pumped into the right ventricle.
• Now both the ventricles contract simultaneously so the pressure is created on the blood and the valves
between atrium and ventricle close and the blood do not go back into the atrium.
• Due to this pressure, the aorta valve opens and the blood comes into the aorta, from here, blood is sent to
different parts of the body with the help of various arteries.
• By the contraction of the right ventricle, blood reaches the lungs through pulmonary arteries where it gets
reoxygenated.

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Heartbeat
• Rhythmic contraction and expansion of the heart is called heartbeat. Contraction and expansion occur
separately in the atria and ventricles.
• In some heart patients, the heart does not beat normally. The muscle cells stop functioning. In such
patients, a machine called a pacemaker is inserted in the patient's heart, so that heart beats normally.
 Heartbeat in humans is 72 times in one minute.
• Each heartbeat has two components, systole, and diastole. Systole represents contraction while diastole
represents expansion or distension of heart chambers.
• Systolic pressure: -When ventricles contract and pushes the blood in artery under high pressure is called
systolic pressure. Normal systolic pressure is 120 mm Hg at 1 atmospheric pressure.
Diastolic pressure: - When ventricles expansion and pushes the blood in artery under low pressure is
called diastolic pressure. Normal systolic pressure is 80 mm Hg at 1 atmospheric pressure.
 Blood pressure is measured by Sphygmomanometer.
Cardiac Cycle: The sequence of events that takes place during the completion of one heartbeat.
Pulse: A wave of distension passes along the arteries following each ventricular systole. This wave of
distension is called an arterial pulse.
• It is generally felt by placing fingers over the radial artery at the wrist.
• The pulse rate is the same as the heartbeat rate.
Electrocardiogram (ECG) The functioning of the heart can be graphically recorded by an instrument called an
electrocardiograph.
Functions of Circulatory System
The most important function of the blood circulatory system is transporting oxygen throughout the body.
The other vital functions of the human circulatory system are as follows:
(1) It helps in sustaining all the organ systems.
(2) It transports blood, nutrients, oxygen, carbon dioxide, and hormones throughout the body.
(3) It protects cells from pathogens.
(4) It acts as an interface for cell-to-cell interaction.
(5) The substances present in the blood help repair the damaged tissue.
Types of Circulatory systems
There are two types of circulatory system found in animals: -
(i) Open Circulatory System: In this type of circulatory system, the main blood vessels arise from
the heart and pour the blood into tissue spaces (sinuses). e.g. Arthropoda (Cockroach),
Echinodermata.
(ii) Closed Circulatory System: In this type of circulatory system, the blood remains only in the
blood vessels and is carried to the various organ through vessels and capillaries. e.g. Human
beings, Annelida (Earthworm), some molluscs.
• In human beings, the circulatory (transport) system is divided into two systems:
(i) Blood Circulatory System
i. Blood
ii. Blood vessels
iii. Heart
(ii) Lymphatic System
i. Lymph
ii. Lymph vessels
iii. Lymph vessels

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Blood
 Blood is an important fluid conducting tissue, which transports the materials to different body parts.
Composition of Blood Liquid part - (Matrix) - Blood plasma
Solid part - Blood corpuscles - (RBC, WBC and Platelets)
Plasma It composes 55% of blood.
• The plasma has 90-92% water and the remaining 8% -10% are other materials.
• The plasma is a faint yellow viscous fluid.  Plasma contains some soluble proteins (serum albumin,
serum globulins, prothrombin, and fibrinogen), inorganic salts, food materials, waste products, dissolved
gases, anticoagulants, and antibodies.
Functions of Plasma
• Transportation of nutrients, respiratory gases, excretion of wastes and hormones of endoc rine glands.
• Prothrombin and fibrinogen plasma proteins help in blood clotting at injuries.
• Globulins of blood plasma act as antibodies and provide immunity (disease resistance) to the body.
• Plasma also helps in the transportation of minerals like iron, copper etc.
Blood Corpuscles
• They form 45% part of blood.
• Erythrocytes or Red Blood Corpuscles (RBC)
• Leucocytes or White Blood Corpuscles (WBC)
• Platelets or Thrombocytes.
Functions of Blood
(1) Transportation of oxygen from lungs to tissues.
(2) Transportation of carbon dioxide from the tissues to the lungs.
(3) Transportation of excretory material from the tissues to the kidneys.
(4) Transportation of digested food from the small intestine to the tissue.
(5) Distribution of hormones and enzymes.
(6) Formation of clots to prevent blood loss.
(7) Distribution of heat and temperature control:
(8) Prevention of infection and wound healing: WBCs in the blood help in wound healing. Bacteria are
destroyed by the WBCs before they can enter the general circulation. Also, the WBCs provide a defense
to the body against disease germs and foreign substances.
Blood vessels In humans, three types of blood vessels are present.
1) Arteries: The vessels which carry blood from the heart to various organs of the body.
2) Veins: They collect the blood from different parts of the body and pour it into the heart.
3) Capillaries: These are the smallest blood vessels and one-cell thick.

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The major differences between various blood vessels have been given in Table.
Comparative Study of Blood Vessels
Features Artery Vein Capillaries
1 Direction
of blood
flow
Take the blood away
from heart to different
parts of body.
Bring the blood towards
the heart from various
body parts
Blood flows from arterioles
(capillaries) to venules.
2 Kind of
blood
Oxygenated blood except
in pulmonary artery.
Deoxygenated blood
except in pulmonary vein.
Blood changes from oxygenated
to deoxygenated.
3 Blood
pressure
Pressure is high Pressure is low Pressure is extremely low
4 Blood flow Blood flows rapidly with
jerks
Blood flows smoothly
without jerks
.. Blood flows smoothly without
jerks
5 Lumen Narrow Wide Very small
6 valves Absent Present Absent
7 Location Mostly deep seated . Mostly superficial Form a network all over the
body and in the organs.
Lymphatic System
• The human circulatory system consists of another body fluid called lymph. It is also known as tissue
fluid.
• It is produced by the lymphatic system which comprises a network of interconnected organs, nodes, and
ducts.
• Lymph is a colorless fluid consisting of salts, proteins, water, which transport and circulates digested
food and absorbed fat to intercellular spaces in the tissues.
• Unlike the circulatory system, lymph is not pumped; instead, it passively flows through a network of
vessels.
Excretion in Human Beings & Plants
EXCRETION: -The biological process of removal of harmful nitrogenous wastes from the body is called
excretion.
The waste products in animals include:
(i) Nitrogenous compounds like ammonia, urea and uric acid.
(ii) Carbon dioxide and water.
(iii) Excess salts and vitamins.
(iv) Unwanted medicines.
Ammonotelic organisms are those which excrete ammonia. e.g. most aquatic animals.
Ureotelic organisms are those which excrete urea. e.g. sharks, frogs, mammals.
Uricotelic organisms are those which excrete uric acid. e.g. birds, insects, land snails, many reptiles.
Excretory Organs/Structures in Animals: -
Animals Amoeba Hydra Flatworm Earthworm Insects e.g. cockroach All chord ates
Excretory
Structures
Cellular
surface
Body
surface
Protonephridia
(flame cells)
Nephridia Malpighi an tubules Kidneys
Waste
products
CO2 and
ammonia
CO2 and
ammonia
Mainly
ammonia
ammonia and
urea Uric acid
Uric Acid Urea
HUMAN EXCRETORY SYSTEM: Human excretory system consists of: -
– A pair of kidneys – A pair of ureters. – Urinary bladder. – Urethra

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KIDNEY :
• The main excretory organ of our body are kidneys.
 HUMAN EXCRETORY SYSTEM
> The excretory system collects the liquid wastes of the body and removes them.
> The excretory system of human consists:
o Two kidneys
o Two ureters
o Bladders
o Urethra
o Bean shaped organs towards back of our body just above the waist.
o Every person has two kidneys.
Colour – Dark red
Shape – Bean shaped
Weight – 125–170 gms. Size – 10 cm length, 5 cm breadth, 3 cm thickness.
Position – Located laterally either sides of vertebral column.
External Structure: -
• Each kidney is surrounded and covered by a tough, fibrous, capsule of connective tissues. This capsule
is called renal capsule.
• Lateral surfaces of kidney are convex while medial surfaces are concave.
• Each kidney is made up of a large number (10 lakhs) of excretory units called Nephrons.
• The human kidney is not located at similar positions due to presence of liver above right kidney,
so the right kidney get slightly lower position.
Internal Structure:
• The internal structure of kidneys can be divided into two parts.
• Its outer part is called cortex and inner part is called medulla.
• Nephron is the structural and functional unit of excretion.
• A nephron consists of a long coiled tubule differentiated into proximal nephron, loop of Henle and
distal nephron. The latter opens into the collecting tubule.
• At the proximal end of the nephron, a double walled cup-shaped structure is present called Bowman's
capsule.
• It consists of network of capillaries called glomerulus.
• One end of the glomerulus is attached to renal artery and the other end to the renal vein.

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• In the glomerulus, blood comes in through afferent arteriole and blood is drained out through efferent
arteriole.
• Glomerulus and Bowman capsule are collectively called Malpighian body or renal corpuscle.
• Structure of Nephron: -
• Nephron is the structural and functional unit of kidney, which is about 3 cm long and 20-60 μm in
diameter.
• Each kidney has about one million nephrons in humans. A nephron can be divided into three regions:
• The function of glomerulus is to filter the blood passing through it. This process is called ultrafiltration.
(I) Proximal nephron (Bowman's capsule + Proximal convoluted tubule)
(II) Loop of Henle (Ascending + Descending limb)
(III) Distal nephron (Distal convoluted tubule which opens into collecting duct)
(I) Proximal nephron: Nephron tubule is closed at its proximal (starting) end but its distal end is open
and continues into the loop of Henle. At the proximal or closed end the nephron is expanded and
curved inwardly to form a double-walled cup shaped Bowman's capsule. Within the Bowman's
capsule a network or tuft of capillaries is present, it is called glomerulus. Diameter of afferent
arteriole is greater than efferent arteriole.
(II) Loop of Henle: It starts after the proximal convoluted tubule, It ends before the distal convoluted
tubule. This hairpin like loop has a descending limb, followed by an ascending limb.
(III) Distal nephron: The ascending limb of Henle's loop merges into distal convoluted tubule. The
distal convoluted tubules of a number of adjacent nephrons open into a common collecting duct or
tubule.
Ureter:
• The collecting ducts open into the ureter.
• Each ureter originates from interior part of kidney.
• The anterior part of the ureter is broad, like a funnel and called pelvis and its posterior part is in the form
of long tubule.
Urinary Bladder:
• Each ureter opens into the urinary bladder.
• The structure of urinary bladder is muscular sac like and pear shaped.
• Its wall is flexible, it collects urine when necessary by the contraction of muscles, the urine is excreted
through urethra.
Urethra: It is a muscular and tubular structure, which extends from the urinary bladder to the outside. It
carries the urine to the outside.
Micturition: Micturition is the term used for urination. (Passing out of urine)

15. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
Functions of Kidney:
> Regulation of water and electrolyte balance. (Osmoregulation)
> Regulation of acid base balance.
> Regulation of blood pressure.
> Excretion of metabolic waste and foreign chemicals.
Physiology of Excretion: -
> The impure blood enters to each kidney through renal artery.
> The afferent arterioles which is branch of renal artery provides blood to the glomerulus.
> Glomerulus is a group of blood capillaries formed by division of afferent arterioles located in Bowman
capsule.
> The arterioles which carry blood away from glomerulus are called efferent arterioles.
> The radius of afferent arterioles is greater than that of efferent arterioles so the pressure in glomerulus
increases which is necessary for ultrafiltration.
> Due to the blood pressure, water, glucose, urea, uric acid and some salt from the blood of afferent
arteriole filter in Bowman capsule through ultra-filtration.
> It also contains glucose, amino acid and some useful salts along with filtrate.
> This liquid from the Bowman capsule moves through the glandular part of the nephron.
> From glucose, useful salt and some part of water is reabsorbed. The amount of water reabsorbed
depends on how much excess water there is in the body and on how much of dissolved waste there is to
be excreted.
> The remaining liquid now contain only waste material is called urine.
> The urine from the nephron is collected in urinary bladder through ureter.
> 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.
> By the contraction of muscles of urinary bladder, the urine passes out of the body when necessary.
> All the systems of our body keep the internal environment stable even on the changing conditions of
external environment.
> Usually the homeostatic activities are performed by excretory organ.
> They not only excrete out salts and nitrogenous waste products but also perform important role of water
balance.
Osmoregulation: - The process of maintaining the right amount of water and proper ionic balance in the body
is called osmoregulation.
Urine Formation: - It involves three processes: glomerular filtration (ultrafiltration), tubular reabsorption and
tubular secretion.
(1) Ultrafiltration: -
> Walls of glomerulus and Bowman's capsule are thin and semipermeable membrane. In the glomerulus
there are many minute pores present.
> Afferent arteriole is wider and releases the blood into glomerulus, whereas efferent arteriole is narrow.
Thus, there is development of high blood pressure.
> Due to this pressure, separation of small, selective molecules ions from the large molecules in the blood
occurs and called ultrafiltration.
> Fluid which is filtered out from the blood is called as glomerulus filterate / capsular filtrate / ultrafiltration.
(2) Tubular Reabsorption: -

16. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
> The ultrafiltration contains salts, glucose, amino acids, urea, uric acid and large amount of water.
> Glucose, salts, amino acids and water are reabsorbed by various parts of nephron and finally they enter
into the surroundings blood capillaries.
(3) Tubular secretion: -
It is removal of wastes from the surrounding blood capillaries into the glomerular filtrate.
Glomerular filtrate entering collecting duct is called urine. Urine composition is different from filtrate by the
loss as well as gain of many substances during the course of nephrons.
Chemical composition of urine:
> Urine is slightly acidic liquid, light yellow in colour.
> The healthy human being has 95% water, 5% urea, uric acid and salts of phosphoric acid.
> A young and healthy person excretes 1.5-1.8 liters’ urine per day.
> This quantity may increase due to intake of tea, coffee, wine etc.
 Role of lungs in excretion: Human lungs eliminate around 18L of CO2 per hour and about 400ml of
water per day in normal resting condition. Water loss via the lungs is small in hot humid climate and
large in cold dry climates.
 Role of skin in excretion: - Human possess two types of glands on skin;
(1) Sweat glands: - These excrete sweat, contain 99.5% Water, NaCl, Lactic acid, Urea, Amino acid and
glucose.
(2) Sebaceous glands: - These secrete sebum which contain waxes, sterols, hydrocarbons and fatty acids.
 Role of liver in excretion: -
> Liver is the main site for elimination of cholesterol, bile pigments, inactivated products of steroid
hormones, some vitamins and many drugs. Bile carries these materials to the intestine from where they
are excreted with the faeces.
 ARTIFICIAL KIDNEY OR HAEMODIALYSIS
> Kidney dialysis also known as hemodialysis or renal dialysis, is a medical treatment used to remove
nitrogenous waste materials from the blood of patients lacking kidney function or kidney failure, due
to infections, injury or restricted blood flow to kidneys.
> In this procedure, the blood is circulated through a machine known as artificial kidney or dialyser that
removes wastes and excess fluid from the bloodstream.
> The blood from an artery is pumped through a dialyser or artificial kidney, where it flows through a
semipermeable membrane which removes unwanted elements in the blood by diffusion.
> The blood is then returned to the body through a vein.
> Main difference of kidney & dialysis is that there is no reabsorption in dialysis.
> In kidney, initial filtrate is about 180L daily but actual excretion is only a liter or two a day.
Excretion
• All the living organisms perform various biochemical reactions and produce toxic .
• If these toxic substances accumulate in body harms an organism, so for normal working an organism,
removal of these toxic substances from the body is necessary.
• The process of removal of toxic wastes from the body of an organism is called excretion.
> Excretion in Plants.
• Plants produce a number of waste products during their life processes.
• The plants remove their waste products by different methods.
> Gaseous excretion: -

17. EXCELLENT CLASSES STD – 10 CHAPTER – 5 SUB :- SCIENCE
• The main products produced by plants are carbon dioxide, water and oxygen.
• Carbon dioxide and water vapour are produced during respiration by plants whereas oxygen is produced
as a waste during photosynthesis.
• The gaseous wastes of respiration and photosynthesis in plants carbon dioxide, oxygen and water vapour
are removed through stomata in leaves and lenticels in stems and released in air.
• The plants excrete carbon dioxide produced as a waste during respiration only at night time.
• As during the day time carbon dioxide released during respiration is being used during the process of
photosynthesis.
• The excrete oxygen and water vapour as waste during day time.
• The removal of Water vapour during day through stomata is called transpiration.
> Other wastes: -
• The plants also store some of the waste from their body parts like leaves, fruits and bark of trees.
• The remove these wastes by shedding of leaves, felling of fruits and peeling of bark.
• When the dead leaves bark and ripe fruits fall off from trees, then the waste products contained in them
are also removed.
• The plants also secrete their wastes in the form of gum and resins from their stems and branches
• The plants also excrete some waste substances into the soil and around them.
Summary
• The plants get rid of gaseous waste products through stomata in leaves and lenticels in stem.
• The get rid of stored solid and liquid wastes by the shedding of leaves, peeling of bark and felling of
fruits.
• The get rid of wastes by secreting them in the form of gum and resins.
• Plants also excrete some waste substances into soil around them.
Excretion in Animals.
• Different animals have different arrangements (organs) for excretion of waste.
• In Amoeba and other single cellular organisms
o In Amoeba and other single cellular organisms remove carbon dioxide by diffusion through the cell
membrane.
o Nitrogenous wastes and excess water are removed by the contractile movement of vacuole.
• In earthworm,
> The tubular structures called nephridia are the excretory organs.
> The moist skin also acts as an excretory organ.
• In human and other mammals
> The microscopic thin tubules form nephron, which works as excretory unit and remove nitrogenous
substances.
> Carbon dioxide produced during respiration is removed.
> Skin also removes salt and water by sweating.
 Removal of waste products in Human.
> The major wastes produced by human body are carbon dioxide and Urea.
> Carbon dioxide is produced as a waste by the oxidation of food during respiration.
> Human lungs excrete carbon dioxide.
> Kidneys excrete urea.