For alliving being it is necessary to performsome basic functions for proper body:

so that it can prevent damage and breakdown of the body and its functions. These functioning,
These hobasic
functions performed by an organism to maintain its life are called lite processes. Energy i
needed for them. The basic life processes which are common to all IiVing, organisms, are
nutrition, respiration, transportation and excretion. Some of these processes are discussed in
this chapter:

NUTRITION
Energy is required by living organisms to perform various activities necessary for their survival.
Nutrition is the process to transfer source of energy (food) from outside to the body of an
organism for maintaining living structures. In other words, it is a process by which an
organism obrains its nutrients and uilises them for obtaining energy and building and
repairing of the tissues. Nutrients are defined as the substances required for proper growth and
maintenance of a living body, i.e. these are materials, which provide nutrition to organisms.
Modeof Nutrition
It means method of procuring food by an organism. Different organisms have different
modes of nutrition. Two modes of nutrition are autotrophic nutrition and heterotrophic
nutrition. Some organisms use simple food material obrained from inorganic sources in the
form of carbon dioxide arid water. These organisms are termed as autotrophs and this mode
of nutrition is called as autotróphic mode of nutrition.
Other organisms which utilise complex organic substances (like carbohydrates, fats, proteins
etc.) that have to be broken down into simpler ones before using them for the growth and
maintenance are termed as heterotrophs and this mode of nutrition is called as heterotrophic
mode of nutrition. For this, such organisms use biocatalysts called enzymes.

AUTOTROPHIC NUTRITION
This mode of nutrition is performed by autotrophs, e.g. green plants (producers) and some
bacteria. On the basis of the source of energy utilised for preparation of food, autotrophs, can
be of two types:
() Photosynthetic autotrophs Green plants fulfil cheir carbon andenergy organisms
requiremen
are
by the process of photosynthesis using sunlight:as a source of energy. Such
called photoautotrophs.
) Chemosynthetic autotrophs Bacteria urilises chemical energy instead of light enery
Synthesise theirorganic materials (food).Such organisms are called chemoautotropms
 Plant Nutrition: Photosynthesis
Acomplex process by which green parts of the plant
synthesise organic food in the form of
carbohydrates from
carbon dioxide and water in the presence of sunlight and
chlorophyl.
Itinvolves the following reaction:
Sunlight
6CO, + 12H,0 CoH,O6t 6H,0 + 60,T
Carbon Water ChlorophylI Glucose Water Oxygen
dioxide

The equation clearly indicates that the raw materials for

photosynthesis are carbon dioxide, water, light energy
and chlorophyll. Its end products are 'glucose
(carbohydrate) and oxygen.
Carbohydrates are utilised for providing energy to the
plant. The remaining carbohydrates, which are not used
immediately are stored in the form of starch, that serves as
the internal energy reserve and is used by the plant
whenever required. Glycogen sserves as an internal energy
reserve to be used, when required in animals.
Events in Photosynthesis
Major events that OCcur during the process of
photosynthesis are:
() Absorption of light energy by chlorophyll.
(i) Conversion oflight energy into chemical energy and
splitting of water molecules into hydrogen and
Oxygen.
(ii) Reduction of carbon dioxide tocarbohydrates.
may or may not take place one after the
Ine above steps carbon
other immediately, e.g. desert plants take compound.
up
dioxide at night and prepare an intermediate
the energy
Ihis intermediate compound is acted upon by
absorbed during the day by che chlorophyll.
Site of Photosynthesis: Chloroplasts
Leaves are the major photosynthetic organs of a plant.
They have large surface area, vascular supply for food and
water supply and apparatus for gaseous exchange.(Leaves
contain green dots that are cll organelles called
chloroplasts) s
Chloroplasts are the site of photosynthesis as they contain
chlorophyll pigment, which traps the solar energy from
the sun. In the cross section of a leaf, chloroplasts appear
as numerous disc-like organelles just below the upper
epidermis. The structure of a leaf can be broadly studied
ünder cross section of a leaf.
 Cross-Section of Leaf
Internallyaleaffcontains
() Epidermis It Is the
following
main parts:
onsists of two distinctoutermost layer of the leaf and
parts, ie. upper epidermis with
no chloroplasts. It protects the internal leaf tissues by
preventing excessive water loss through evaporation and
lower epidermis, which contains stomata and
) gaseous exchange in the plant. helps in
Lamina or
Midrib. -leaf blade
Vein

Phloem Xylem
Vascular bundle Waxy
cuticle
-Upper
epidermis
Chloroplast

Air spaces<

Guard cell
OJLower
epidermis
Cross-section (palisade) of a leaf
(i) Stomata These are tiny pores, mostly found in the lower
epidermis, which allow gases to enter and exit the leaf
more rapidly between the plant and atmosphere.
(ii1), Guard cells These are bean-shaped cells that frame the
Stomatal openings. They contain chloroplasts and have
cellwall. Each pair of guard cells controls the opening
and Clos1ng of the stoma. Hence, controlling the rate of
diffusion of gases and water vapour into and out of the
leaf.
 Conditions
Varioss Necessary for Photosynthesis
experiments have shown tha. presence
nresence of sunlight
and chlorophyllare
necessary for photosynthesis
They are discussed below:
(2) Sunlight It affects the rate of
photosynthesis
varying intensity, quality and duration. by s
(i) Chlorophyl Agreen coloured photosynthetic pigment
tound in chloroplast of a plant that is responsble ro
trapping solar energy.
Raw Materials for
Following raw materialsPhotosynthesis
are essential to carry out the process
of photosynthesis in plants:
() Carbon dioxide It is released into atmosphere during
respiration and enters the leaf through stomata, i.ç.*
tiny pores present on the surface of the leaves through
which massive amount of gaseous exchange takes place
in leaves. Apart from this, surface of stems, leaves and
roots also contibute in the gaseous exchange.
.Note Aquátic plants use CO, dissoved in water for photosynthesis.
(i)Water It is absorbed by the roots from the soil and
transported' upward through xylem to the leaves and
then to photosynthetic cell. These water molecules
split in the presence of sunlight to form hydrogen and
Oxgyen. This is called photolysis of water.
(iin Other materials Nitrogen, phosphorus, iron and
magnesium are also required
soil.
for photosynthesis and
aretaken up from the
Note Nitrogern isan esSential element used in the synthesis of
proteins and other compounds. It is taken up in the form of
inorganicnitrates (or nitrites) or as organic compounds
prepared bybacteria from atmospheric nitrogen.
HETEROTROPHIC NUTRITION
In heterotrophic mode of nutrition, organisms cannot
prepare food on their own, Heterotrophs obtain energy from.
organic molecules already produced by the autotrophs. The
heterotrophic forms of nutrition differ depending on the
type, availability and process of obtaining food materials by
the organism.
 Accordingly, there are herbivores, carnivores,
saprotrophs and parasites, included in omni vores,
heterotrophs.
Heterotrophic mode of nutrition can be of following thre
main types:
(2 Holozoic nutrition Herbivores (plant-caters),
carn1vores (meat-eaters) and omnivores (both plant and
meat-eaters) possess the holozoic mode of nutrition.
Complex food molecules are taken in and then broken
down into simpler and soluble molecules in this type of
nutrition, e.g. Amoeba, cow, goat, dog, cat, human
being etc.
() Saprotrophic nutrition (saprophytic nutrition)
Saprotrophs are the organisms having saprotrophic
mode of nutrition.They usually feed upon dead
organic matter, breaking down complex materials
outside the body and absorbing it, e.g. fungi like
bread moulds, mushrooms, yeast and bacteria.
(iii) Parasitic nutrition Parasites are the organisms
having parasitic nutrition. These organisms live either
on or inside the body of other organism (host) to
obtain their nutrition without killing them, e.g
Plasmodium, ticks, lice, leech, tapeworm, flatworm,
plants likeCuscuta (amarbel), yellow rattle etc.
Differences between the Two Modes of Nutrition
Autotrophic Nutrition Heterotrophic Nutrition
Itoccurs in green plants,some It occurs in fungi and animals.
bacteriaánd in some protists.
Chlorophyll is necessary for Chlorophyll is absent; as such
trappingsolar energy. they do not trap solar energy.
Food is self-manufactured Food is obtained directly or
usingCO, and water as raw indirectly from autotrophs.
materials.

Digestion of food does not Digestion is required to convert

OCCur. Complex organic substances
present in food into simpler and
soluble forms.
Theyare placed at the bottom They are placed above producers
of the food chain as in the middle of food chain as
producers. Consumers.

e.g. plants, blue-green algae e.g. animals including humans.

andcyanobacteria.
 Nutritionin Amoeba
Amoeba is a unicellular, omnivore organism that does not
possess specialised organs for the process of nutrition. The
mode of nutrition in Amocba is holozoic and takes place
with the help of pseudopodia (inger-like extensions).
It engulfs the food when it comes in contact with its cell
surface by ingestion. Pseudopodia fuses over the food
particle to form afood vacuole.
Digestion in Amocba is intracellular (takes place inside the
cel) in nature. Inside the food vacuole, complex food breaks
into small soluble molecules, readily absorbed by the
groplasm. This process is called absorption. The absorbed
food is further assimilated by moeba to derive energy for
growth. The undigested food material is removed by the
cell membrane, which ruptures suddenly at any place and
eliminates out the undigested food. This process of
throwing out undigested food is called egestion.
Nucleus
(a) Ingestion Pseudopodia
Food particle

Food vacuole

(b) Digestion -Food particle

(c) Absorption

(d) Assimilation
Amoebagrows

Undigested food
(e) Egestion removed

Different stages of nutrition in Amoeba

Note Paramecium is another unicellular organism, which has

definite shape. The food is taken in at aspecificspot in it,
which reaches there by the movement of cilia, which
cover the.entire surface of the cell.
 Nutritionin Human Beings
Nutrition in human beings is the process of intake of esential
nutrients in the form of food. It takes place through human
digestive system.
Description of Human Digestive System
Digestion is a catabolic process, in which complex and large
componènts of food are broken down into their respective
simpler andsmaller forms with the help of various hydrolytic
enzymes. These simpler formsare further taken up by different
parts of body and are finally absorbed.
The entire system, which performs this processof digestion is
known as digestive system. In human beings, the digestive
system constitutes a long tubular structure called alimentary
canal (about 7-8 metres long) and digestive glands associated
with it, which secrete various digestive enzymes.
Mouth/buccal cavity Oesophagus (food pipe)
Salivary Glands

Stomach

Liver
Pancreas

Gall bladder Large intestine

Rectum
Bile duct

Small Intestine Anus

Human digestive system
Alimentary Canal
.t is a long tube, where the entire process of digestion takes
place. It is an internal coiled tube, which runs from anterior
mouth to the posterior anus. The complete process of
ingestion, digestion, absorption, assimilation and egestion of
food material is done within the alimentary canal itself.
Themajor portions of alimentary canal are discussed below:
() Mouth The first patt of the digestive system from
where the food enters into the alimentary canal. Mouth
ismainly comprised of two major parts:
Tongue It is a highly muscular sensory organ present
at floorof buccal cavity: It bars several taste buds and
helps in mixing food with saliva. Apart from this, it is
also helpful in producing speech.
 " leeth These are hard structures present on the bones o
both lower and upper iaw. Teeth are basically used for ue
the
purpose of grinding, cutting and chewing of food.
Human beings bear four different rypes of teeth, i.e. incisors
for cutting the food, canines for tearing of food, premolars
and molars forcrushing, chewing and grinding of fo0d.
Dental Caries (Tooth Decay)
It isa condition, which causes gradual softening of enameland
dentine. It usually begins when bacteria acting on sugars produce
acids and soften or demineralise the enamel. Masses of bacterial cells
together with food particles stick to the teeth to form dental plaque.
Due to this, the saliva fails to reach the tooth surface to neutralise the
acid because 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.
 (i) Pharynx Small funnel-shaped chamber located behind
and
the oral cavity.
Communicates with both oesophagus
trachea (windpipe).
(iii) Oesophagus Thin, long muscular tube that leads into
stomach.
(0) Stomach It is the most dilated J-shaped part of the
alimentary canal, which is situated between the oesophagus
and the small intestine, below the diaphragmn. ltserves as a
Sstorehouse of food where partial digestion takes place
through the secretion of gastricglands. The muscular walls
of the stomach help in mixing the food properly.
(2) Small intestine The longest part of the alimentary canal
smallintestine is fitted in a compact spaceas extensively
coiled structure in our belly.
The length of small intestine differs in all organisms
depending upon their food habits, e.g. herbivores have
long small intestine to facilitate cellulose digestion.
Cellulose is not digested in human alimentary canal as
there is nodigestive enzyme (likecellulase), which can act
cellulose. Carnivores have shorter length of small
intestine as meat is easily digestible.
Small intestine is the site of complete digestion of food
into different components. Secretions from liver and
pancreas enter the intestine to help in the digestion
process. The inner lining of the small intestine has
numerous finger-like projections called villi, which
increase the surface area for absorption.
(vi) Large intestine Although shorter, but is called large
intestine because it is wider in diameter than small
intestine.
(vi) Rectum The last and broad
serves to store faecal matter chamber-like structure that
temporarily.
(vii) Anus The end point of alimentary
exit of waste material. The exit canal, which helps in
of waste material 1s
regulated by anal sphincter.
Digestive Glands
associated with
Various glands are associated with alimentary canal
serving the process of digestion of food. These are giiven
below:
() Salivary glands These glarnds secrete
saliv:
containing an enzyme called salivary amylas
(ptyalin). It converts starch into sugar at a
optimum pH of about 7. It is due to thesesalivar
glands that our mouth waters when we eat or smel
something we like.
() Gastric glands These are found in the wall of the
stomach. The gastricglands release digestive juice
containing HCkpepsin, mucous etc.
Hydrochloric acid (HCI), killsthe bacteria ingested
with food. It creates an acidic medium of pH about
2, facilitating the action of pepsin enzyme, which
onproteins present in food.
Due to this highly acidic nature of HCI, the
digestion of starch in stomach is prevented. It also
prepares the ingested food for further processing
in the small intestine. The mucus protects the
lining of the stomach from the action of the
hydrochloric acid produced under normal
conditions.
(i) Liver It is known as the largest glandof thebod,
which secretes bile juice, They act on large fat
molecules to form smaller globules increasing the
efficiency of enzyme action. Gal| bladder stole
bile juices for the further use.
Note Bile juice flows into the gallbladder through the
common hepatic duct that joins the cystic duct coming
from the gall bladder to form acommon bile duct.
Bile acts on the food entering from stomach and makes
it alkaline. This facilitates the action of pancreatic
secretions on food.

(iv) Intestinal glands Walls of small intestine contain

numerous glands that secrete intestinal juice
containing amylolytic, proteolytic and lipolytic
enzymes.
(v) Pancreas It secretes pancreatic juice, which
contains enzymes like amylase,trypsin and lipase:.
It is connected to the small intestine through its
main duct called pancreatic duct, which joins the
bile duct to form common hepatopancreatic au
that opens into small intestine (duodenum).
Note This gland also secretes hormones glucagon and hsu
which regulate glucose metabolism in body.
Mechanism of Digestion of Food
The food we cat contains various components like
carbohydrates, proteins, fats, vitamins, minerals etc.
Various stepsinvolved in digestion of these nutrients as
given below:
1. Ingestion
Intake of food by mouth. Food is moistened bysaliva,
before swallowing, masticated by teeth to smaller
particles.
2. Digestion
The process of breaking down large organicmolecules
(like carbohydrates) into smaller molecules (like simple
sugars) is called digestion. It is done with the help of
enzymes.
It is completed in following main steps:
Carbohydrates digestion initiates inside mo
Starch is convertedto simplesug¡r
by salivary amylase. )
Proteins are converted to peptones with
the help of pepsinand renin.
Emulsification of fats with the help of bile juices.

Breakdown of emulsified fat by lipase.

Formatiorn of amino acid, glucose and fatty

acids with the helpof pancreatic
and intestinatjuices.
 3.Absorption
It is the process by which digested food passes from the
alimentary canal into the blood. All the digested food is taken up
by the walls of intestine, which has numerous villi and lacteals
(smalllymph capillary found in the villi of the small intestine).
They increase the surtace arca of absorption.
Note Fatty acids are insoluble in water so, they donot reach the blood
stream directly. For this, they are first converted into small, water
soluble droplets with the help of bile salts in the intestinal lumen,
then actedupon by digestive enzymes.

Peristalsis
It is the necessary action of the digestive process and is essential for
moving food in a regulated manner along the digestive tube. The
lining of the alimentary canal has muscles, which contract
hythmicallyin order to push the food torward. These movements
are called peristaltic movement. They occur all along the gut,
into stomach.
e.g. it Occurs in oesophagus when food is moved

4. Assimilation
The distributionof digested food products to various cells of the
body. The villi in small intestine are richly supplied with blood
vessels, which take the absorbed food to each and every cell of the
body, where it is utilised for obtaining energy, building up new
tissues and repairing the older ones.
5. Egestion
of the
Theelimination of undigested food formed in thecolon
large intestine through anus is called egestion.
from small
Peristalsis gradually pushes the undigested foodmaterial
intestine to large intestine. The remaining after
reabsorption of water and ions is sored in the rectum for
some

timeand is ultimately removed from the body through anus.

. Nutrition is the process of transfer of energy
outside to the body of living organisms, source from
necessary for maintaining livingstructures andproviding energY
performing basic
life processes.
Nutrients are the energy providing substances
when
consumed by living beings.
Autotrophic Nutrition The mode of nutrition performed by
green plants; some bacteria, etc., for manufacturing their own
food from inorganicsources, i.e. CO, and water. The
are called autotrophs. organisms
Photosynthesis is the process by which green plants
synthesise organic food as carbohydrates in the presence of
sunlight and chlorophyll, water, CO, and some other raw
materials.
Chloroplasts are the site of photosynthesis, present in leaves
of aplant. They Contain a green coloured pigment, chlorophy
that traps solar energy from Sun.
Photosynthesis occurs in three stages, i.e. absorption of light
energy, conversion of light into chemical energy and splitting of
water molecule, i.e. photolysis.
Heterotrophic Nutrition The heterotrophs cannot synthesise
their own food, but are dependent on the autotrophs for their
nutrition. It can be of three types:
. Holozoic nutrition, where complex molecules are taken in
and broken into simpler forms, e.g. Amoeba, cow, goat,
humans, etc.
Saprotrophic nutrition, where nutrition is derived from the
breakdown of complex molecules in dead and decaying
organic matter.
In parasitic nutrition the organisms derived nutrition from
the host's body they live on or inside, e.g. licks, lice, leech,
etc.
Nutrition in Amoeba which is a unicellular omnivorse
It lacks special
gathers and ingests food with pseudopodia.beings involves
Organs for nutrition. Nutrition in human in
Dreakdown of complex substances ingested from outside
the body by different parts of alimentary canal.
. Human digestive system consists of alimentary canal, i.e.
a tube-like structure consisting of mouth,
pharynx,
oesophagus, stomach, small intestine and large intestine.
Mouth is first part of digestive system which helps in intake
of
food. Tongue a muscular organ bearing taste buds. It also
helps in mixing the chewed food with saliva. Teeth help in
chewing of food. Mouth opens into buccal cavity that further
opens into pharynx.
Oesophagus or the food pipe helps in transfer of food down
to stomach.
Stomach J-shaped organ which stores and partially digest
the food entering through the food pipe.
Intestine is the main organ of digestion and absorption.
Small intestine is longer in length compared to large
intestine.
Anus is the end point of the alimentary canal from where
the waste is removedout fromthe body.
Digestive glands are the salivary, gastric intestinal glands
along with pancreas and liver.
Salivary glands (in mouth) secrete saliva containing salivary
amylase vwhich helps in digestion of starch.
Gastric glands present in stomach secrete digestive juice
Containing pepsin, HCl and mucus.
Intestinal glands present in walls of smallintestine secrete
intestinal juice containing amylolytic, proteolytic and lipolytic
enzymes.
Liver is the largest gland of our body, secretes bile juice for
emulsification of fats.
Pancreas secretes pancreatic juice containing trypsin,
amylase and lipase enzyme.
The process of digestion in all involves ingestion, i.e. intake
of food by mouth, digestion, absorption, i.e. passage of
digested food from alimentary canal to blood, assimilation
i.e. distribution of digested food to cells of the body and
egestion, i.e. the elimination of undigested food (waste)
from body.