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LIFE PROCESSES
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Living organisms require oxygen, water and food in every cell of their various tissues
to live. These basic functions performed by living organisms to maintain life on earth
are called as life processes.
Different organisms utilize different kinds of nutritional processes based on the
complexity of these carbon compounds.
The basic life processes common to all living beings are :
o Nutrition and respiration
o Transport and excretion
o Control and coordination
o Growth
o Movement and reproduction
1. Nutrition
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There are different types of nutrition such as :
a) Autotrophic nutrition – It is the mode of nutrition in which an
organism synthesizes its own food from simple inorganic materials like
carbon dioxide and water present in the surroundings. Autotrophs
contain chlorophyll pigment that is capable of trapping and fixing the
solar energy.
E.g. green plants, Euglena
b) Heterotrophic nutrition – It is the mode of nutrition in which an
organism cannot synthesize its own food from simple inorganic
materials like carbon dioxide and water, and depends on other
organisms for its food.
E.g. All animals, most bacteria and fungi.
A heterotroph can obtain its food from other organisms in three other
ways:
i. Saprophytic nutrition – In this mode of nutrition, the organism
obtains its food from decaying organic matter of dead plants and
animals, rotten bread etc. E.g. Fungi, bacteria.
ii. Parasitic Nutrition – In this mode of nutrition, the organism
obtains its food from the body of another living organism (host)
without killing it. E.g. Tapeworm, Cuscuta (amarbel) etc.
iii. Holozoic nutrition – In this mode of nutrition, the organism
takes the complex organic food materials into its body by the
process of ingestion, the ingested food is digested and then is
absorbed into the body cells of the organism.
E.g. Man, cat, dog etc.
LIFE PROCESSES
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Nutrition in plants
o The process by which green plants make their own food from carbon
dioxide and water by using sunlight in the presence of chlorophyll is
called as photosynthesis.
Sunlight
6CO2 + 12H2O
Chlorophyll
C6H12O6 + 6H2O + 6O2
o The process takes place in the green leaves of the plant.
o The extra glucose is changed into another food called as starch which
is stored in the leaves of the plant.
o The green plants convert sunlight into chemical energy by making
carbohydrates.
o The conditions essential for photosynthesis are:
i.
Sunlight
ii.
Chlorophyll
iii. Carbon dioxide
iv.
Water.
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Nutrition in human beings
o Human beings obtain their food from other animals or plants.
o The human digestive system is made up of two parts:
i.
Alimentary canal
ii.
Digestive glands
o Alimentary canal is about 9 meters long which starts from the mouth
and extends up to the anus.
o The various organs of the digestive system are mouth, oesophagus,
stomach, small intestine and large intestine.
o The glands that are associated and form a part of the human digestive
system are salivary glands, liver and pancreas.
o The ducts of various glands pour out the digestive juices into the
alimentary canal.
o The various steps of nutrition in human beings are:
i.
Ingestion – Ingestion is the process of consuming something
and taking it into the body. Mouth is a special organ for
ingesting the food
ii.
Digestion – Digestion is the mechanical and chemical
breakdown of food into smaller components that are more
easily absorbed into the blood stream.
iii. Absorption – The small intestine is the main region for the
absorption of digested food.
LIFE PROCESSES
iv.
v.
Assimilation – The blood carries the digested and dissolved
food to all the parts of the body where it is assimilated as a part
of the cells.
Egestion – It is the process by which organisms eliminate
solid, semisolid, and/or liquid waste material from the digestive
tract via the anus.
2. Respiration
A. Respiration in plants
 It is a complex process which includes breathing (exchange of O2 and CO2 and
oxidation of food to release energy).
Food + Oxygen
CO2 + H2O + Energy
 The process of respiration which releases energy takes place inside the cells of
the body.
 Oxidation of glucose takes place during this process in the mitochondria of the
cells.
 There are two types of respiration:
a) Aerobic respiration – The respiration that uses oxygen is called as
aerobic respiration. ATP is the main source of energy. It involves two
steps:
i.
Glycolysis
ii.
Krebs cycle
b) Anaerobic respiration – The respiration which takes place without
oxygen is called as anaerobic respiration.
B. Respiration in animals.
 Animals have specific organs for respiration like skin, lungs, and gills.
 Air travels through the following organs:
Nostrils
nasal passage
pharynx
larynx
trachea
bronchi
bronchioles
alveoli
 The process by which the atmospheric air reaches the lungs is known as
inspiration.
 The process by which foul air of the lungs is released is known as expiration.
 The respiratory pigments take up oxygen from the air in the lungs and carry it
to the tissues. In humans, haemoglobin is the respiratory pigment that is
present in the RBC.
LIFE PROCESSES
3. Transportation
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In biology, transport is a life process in which a substance absorbed in one part
of the body of an organism is carried to other parts of its body.
A. Transportation in plants
 The loss of water in the form of vapour from the leaf to the atmosphere is
known as transpiration.
 The plants have two transport systems:
1) Xylem – It carries water and minerals. The water and minerals
dissolved in the soil move from the roots of the plant to its leaves
through two types of xylem tissue called xylem vessels and tracheids.
2) Phloem – It carries the food materials which the plant makes.
 The transport of food from the leaves to other parts of the plants is called
translocation.
 The transport of materials in a plant can be divided into two parts:
i.
Transport of water and minerals in the plant.
ii. Transport of food and other substances in the plant.
B. Transportation in human beings
 The main transport system in human beings is the blood circulatory system.
 In the human circulatory system, the blood caries oxygen, digested food and
other chemicals like hormones and enzymes to all the parts of the body.
 The human blood circulatory system consists of the heart and the blood vessels
through which the blood flows in the body.
 In blood circulatory system, blood flows through three types of blood vessels:
i. Arteries
ii. Veins
iii. Capillaries
 Lymphatic system also helps in the transport of materials in the human body.
 Lymph is the fluid that circulates and carries materials in the lymphatic system.
 The human circulatory system is made up of the heart, arteries, veins,
capillaries and blood.
 The heart is a special muscle called as the cardiac muscle having four
chambers inside it. The upper two chambers of the heart are called as atria and
the lower two chambers are called as ventricles.
 Heart is situated in the thoracic cavity between two lungs and pumps at the rate
of 72 heartbeats/ minute. On contraction, systolic phase – 120 mm of Hg and
on relaxation, diastolic phase – 80 mm of Hg.
LIFE PROCESSES
 The circulatory system of man is known as the double circulation as the blood
passes through the heart twice in the complete cycle of the body. It involves
two circulations:
a. Pulmonary circulation – It starts in the right ventricle where it expels
blood in the pulmonary trunk, the blood flowing into the vascular
system of the lungs, becomes oxygenated and returns to the heart
through pulmonary veins.
b. Systemic circulation – This circulation is maintained by the left
ventricle which sends the blood into the aorta.
4. Excretion
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The process of removal of toxic wastes from the body of an organism is called
as excretion.
A. Excretion in plants
 The main waste products produced by plants are CO2, water vapour
and O2.
 The gaseous wastes of respiration and photosynthesis in plants are
removed through the stomata in the leaves and lenticels in stems and
released into the air.
 Plants also store some of the waste products in their body parts and get
rid of them by shedding of leaves, peeling of bark and felling of fruits.
 Many waste products are stored as resins and gums in plants.
B. Excretion in animals and humans.
 Different animals have different arrangements for excretion which
depend on the constitution of the animal.
 The process of maintaining the right amount of water and proper ionic
balance in the body is called as osmoregulation.
 Excretory system of human beings consists of a pair of kidneys, a pair
of ureters, urinary bladder and urethra.
 The function of the kidneys is to remove the poisonous substance urea,
other wastes and excess of water from the blood and excrete them in
the form of urine.
 Artificial kidney is used when natural kidneys start malfunctioning or
stop working.