Short Notes and Board Exams Questions: Life Processes


All living things perform certain life processes like growth, excretion, respiration, circulation etc.

All the processes like respiration, digestion, which together keep the living organisms alive and perform the job of body maintenance are called life processes.
Examples :

                                   Modes of Nutrition


Autrotrophic                                                                     Hetrotrophic

Kind of nutrition in which                                                                               Kind of nutrition in which
inorganic materials like CO2                                                                        , organisms do not possess
water etc. are utilized to prepare                                                               the ability to synthesize their
organic food by the process of                                                                    own food. They depend on
photosynthesis.                                                                                                    autotrophs for their food
E.g., Green plants                                                                                                  supply directly or indirectly.
E.g., Animals, fungi.

Autotrophic Nutrition :


The organisms which carry out autotrophic nutrition are called autotrophs (green plants).

Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO2
andH2O and convert these into carbohydrates in the presence of chlorophyll, sunlight is called Photosynthesis.

Raw Materials for Photosynthesis :

• Sunlight

• Chlorophyll Sunlight absorbed by chlorophyll

• CO2 Enters through stomata and oxygen (O2) is released as by-product through stomata on leaf.

• Water → Water + dissolved minerals like nitrogen, phosphorus etc. are taken up by the roots of the soil.

Site of Photosynthesis :

Chloroplast in the leaf, chloroplast contain chlorophyll (green pigment).

Main Events of Photosynthesis :

• Absorption of light energy by chlorophyll

• Conversion of light energy into chemical energy + splitting (breaking) of water into hydrogen and oxygen

• Reduction of CO2 to carbohydrates


Stomata : Tiny pores present on the surface of the leaves.


 Functions :

(a) Exchange of gases O2/CO2

(b) Loses large amount of water (water vapour) during transpiration.

                                                                                    Hetrotrophic Nutrition

How do organisms obtain their food

Unicellular/Single celled organisms : Food is taken up through entire surface.
Example : (i) Amoeba
(ii) Paramaecium


(i) Amoeba

(ii) Paramaecium

Paramaecium Cilia → Take in food At a specific spot (Present all over the body)




Ingestion                    Digestion                  Absorption                   Assimilation            Egestion
(Intake of                    (Breakdown             (Movement                 (Utilisation               (Removal of
food)                             of complex                 of digested                   of food)                        waste
material into              food)                                                                       products)
simple ones)
Different organisms utilize different nutritional processes as it depends upon the source of carbon from where the food is taken.

Human Digestive System



Respiration involves : (i) Gaseous exchange : Intake of oxygen from the atmosphere and release of

CO2—> Breathing

(ii) Breakdown of simple food in order to release energy inside the cell → Cellular respiration


Breakdown of Glucose by Various Pathways



       Aerobic                                                                                        Anaerobic

• Takes place in the presence                                                                             • Takes place in the absence
of oxygen                                                                                                                            of oxygen
• Occurs in mitochondria                                                                                     • Occurs in cytoplasm
• End products are CO2
and H2O                                                                                                                         • End products are alcohol or lactic acid

• More amount of energy is released                                                           • Less amount of energy is released


Human Respiratory System

Passage of air through the respiratory system :

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Mechanism of Breathing

Inhalation                                      Exhalation

• During inhalation the thoracic                                                        • Thoracic cavity contracts.
cavity (chest cavity) expands.
• Ribs lift up.                                                                                                     • Ribs move downwards.
• Diaphragm become flat in shape.                                                     • Diaphragm becomes dome shaped.
• Volume of lungs increases and                                                           • Volume of lungs decreases
air enters the lungs                                                                                         and air exits from the lungs.




Exchange of gases between alveolus, blood and tissues

(i) Air (rich in O2)—-> Blood Binds with haemoglobin in RBC O2 is released in (in alveolus) (through blood vessels) tissues
(ii) CO2—–> Released in blood Dissolved in blood Blood vessels Released in alveolar sac Sent out through nostrils (from tissue)      (in alveoli)

Terrestial organisms : Use atmospheric oxygen for respiration
Aquatic organisms : Use dissolved oxygen for respiration


Respiration in plants

Respiration in plants is simpler than the respiration in animals. Gaseous exchange occur through :
(a) Stomata in leaves
(b) Lenticels in stems
(c) General surface of the root



Human beings like other multicellular organism need regular supply of food, oxygen etc. This function is performed by circulatory system.

The circulatory system in human beings consists of

Diagram to show blood circulation in human body


    Double circulation

Blood travels twice through the heart in one complete cycle of the body.

Direction of blood flow through human heart

Pulmonary Circulation : Blood moves from the heart to the lungs and back to the heart.
• Systemic Circulation : Blood moves from the heart to rest of the body and back to the heart.

Lymph: A yellowish fluid escapes from the blood capillaries into the intercellular spaces contain less protein than blood. Lymph flows from the tissues to the heart assisting in transporting and destroying germs.


                     Blood vessels                                                                          veins

Carry oxygenated blood from heart to body parts                                       1. carry deoxygenated blood from body         except pulmonary artery                                                                                                parts to heart except pulmonary vein

2. Also called distributing vessels.                                                                             2. Also called collecting vessels

3. Thick and elastic                                                                                                             3. Thin and less elastic

4. Deepseated                                                                                                                       4. Superficial as compared to arteries


Transportation in Plants


There are two main conducting pathways in a plant.
  Xylem                                                                                                                                                       Phloem

1. Carries water & minerals from                                                                    1. Carries product of photosynthesis
the roots to other parts of the plant.                                                         from leaves to the other parts of the  plant

2. No energy is used.                                                                                                       2. Energy is used from ATP.
Transpiration is the process of loss of water as vapour from aerial parts of the plant.


Function :

(a) Absorption and upward movement of water and minerals by creating PULL.
(b) Helps in temperature regulation in plant.
Transport of food from leaves (food factory) to different part of the plant is called Translocation.


                             EXCRETORY SYSTEM IN MAN


Excretory/urinary system consists of :

(1) The kidneys : The excretory organ

(2) The ureters : The ducts which drain out urine from the kidneys

(3) The urinary bladder : The urinary reservoir

(4) The urethra : The channel to the exterior

                                                                                      The human excretory system


1. The metabolic activities in the body generates many kinds of wastes including nitrogenous wastes which are harmful for the body and hence needed to be removed.
Excretion is a process by which these wastes are removed from our body.

2. Unicellular organisms remove these wastes by simple diffusion.


    Human Excretory System

     Formation of Urine

• Each kidney contains many filtration units called as nephrons.

• Nephrons are made up of a cluster of thin walled capillaries called glomerulus which is associated with a cup like structure called as Bowman’s capsule and the long tube which terminates through this capsule.

• The renal artery brings oxygenated blood to the kidneys along with the nitrogenous wastes like urea and uric acid and many other substances.

• The blood gets filtered through the glomerulus and this filtrate enters the tubular part of nephron.

• As this filtrate moves down the tubular part, glucose, amino acids, salts and excess of water gets selectively reabsorbed by the blood vessels surrounding these tubules.

• The amount of water reabsorbed depends upon :
* How much excess of water is there in the body and,

* How much nitrogenous wastes need to be excreted out.

• So the fluid now flowing in the tubular part is urine which gets collected in collecting ducts of nephrons.

• These collecting ducts together leave the kidney at a common point by forming the ureter.

• Each ureter drains the urine in the urinary bladder where it is stored until the pressure of expanded bladder leads to an urge to pass it out through urethra.

• This bladder is a muscular structure which is under nervous control.

• 180 litres of filtrate is formed daily but only 2 litres is excreted out as urine so the rest is reabsorbed in the body.


Functions of Nephron

• Excretion of nitrogenous wastes.

• To maintain the water and ionic balance (osmic regulation).


Excretion in Plants

Plants use different strategies for excretion of different products :

• Oxygen and carbon dioxide is diffused through stomata.

• Excess water is removed by transpiration.

• Plants can even loose some of their old parts like old leaves and bark of tree.

• Other waste products like raisins and gums especially in old xylem cells which can also be lost by plants.

• Plants also secrete some waste substances into the soil around them.

Structure of a Nephron

The urine formation involves three steps :
1. Glomerular filtration : Nitrogenous wastes, glucose water, amino acid filter from the blood into Bowman Capsule of the nephron.

2. Tubular reabsorption : Now, useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.

3. Secretion : Urea, extra water and salts are secreted into the tubule which open up into the collecting duct & then into the ureter.

                                                                     Artificial Kidney

Haemodialysis : The process of purifying blood by an artificial kidney. It is meant for kidney failure patients.



              VERY SHORT QUESTIONS (1 Mark)


1. State one difference between autotrophic and hetrotrophic mode of nutrition.

2. Define peristaltic movement.

3. What is the role of saliva in the digestion of food ?

4. Name the tissue that transports water and minerals in plants.

5. What is the role of acid in our stomach ?

6. What is emulsification ?

7. Name the cell organelle in which photosynthesis occur.

8. Name the largest artery in the human body.

9. Define transpiration.

10. What is the structural and functional unit of kidney called ?




1. How is small intestine designed to absorb digested food ?

2. What are stomata ? Draw a labeled diagram of stomata.

3. Write the equation for the process of breakdown of glucose in a cell :
(a) in the presence of oxygen.
(b) in the absence of oxygen.

4. Write the differences between inhalation and exhalation.

5. List the three events which occur during photosynthesis.

6. How does transpiration help in upward transport of substances.

7. Write the functions of the components of blood.

8. Why is small intestine longer in herbivores than in carnivores ?

9. Explain the cause of cramps after excessive physical exercise.

10. Why is the rate of breathing in aquatic organisms much faster than that seen in terrestrial organisms.



1. Describe the process of double circulation in human beings.

2. What are the methods used by plants to get rid of their waste products ?

3. Give reason for the following :
(a) Arteries are thick walled blood vessels.
(b) Veins are thin walled blood vessels.
(c) Veins have valves in them.



1. If you chew chapatti for long, after some time it taste sweet ? Why is this so ?

2. What is the benefit of residual volume of air in the respiratory process ?

3. Why is the energy needs in plants is very less as compared to animals ? Explain.

4. Draw a well-labelled diagram of Nephron. Explain the process of formation of urine in the human kidney.

5. Draw a diagram showing Human Respiratory System. Label the following parts :
(a) Alveolus (b) Trachea
(c) Bronchus (d) Lungs


Hints to Long Answer Type Questions

1. Chapati will taste sweet as saliva breaks down starch which is a complex molecule to give sugar.

2. The lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

3. Plant gets most of energy during photosynthesis.

4. See the given diagram.

5. See the given diagram.

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