1 Life Processes

INTRODUCTION

All living organisms are made up of cell. Unicellular organisms are made up of single cell only but on the other
hand multicellular organisms are made up of multiple of these cells. So, we can say that cell is the structural
and functional unit of life.

All living organisms have an organized (cellular) structure with different levels of organization. An
organized and ordered structure with cells, tissues, organs, organ system, etc. is an important feature that
distinguishes the living from the non-living. If this organisation breaks down, an organism is no longer alive as
organization is not only confined to the external appearance, but is present in the internal structure as well.
Therefore, living things have to repair and maintain their structure through various processes known as life
process.

The basic functions performed by organisms to maintain their organised living structure are called Life processes.
OR
Life processes are the biological processes which are essential to maintain life or living state of an organism.

The main criteria of life : Any cell bounded by a cell membrane containing living protoplasm and showing
molecular movement in it.

Characteristic features of living organisms

• Need air, water and food for survival
• Respire to release energy from food.
• Shows growth (in terms of number and mass and the growth is internal)
• Shows movement of their own.
• Follow the process of excretion of the body waste.
• Generally responds to the stimuli.
• Reproduce their own kind.

All life process depends on metabolism of the living organism.

Metabolism : The sum total of all the chemical reactions taking place in a living body is known as its metabolism.
Anabolism
Metabolism :
Catabolism
Anabolism : Anabolic reactions are those chemical reactions of the body in which complex substances are
synthesized from simpler substances. They are also known as ‘building up’ reaction eg. photosynthesis,
protein synthesis etc.

Catabolism : In catabolism complex substances are broken down to release simpler substances. They are
also called ‘breaking down’ reactions ex.-respiration.

Food : Food is a kind of fuel which provide energy to all living organism.

Proteins
Carbohydrates Fats

Components of
food

Roughage Minerals
Water Vitamins
Importance of food : All living organism need food for the following reasons.
• It is a source of energy.
• To supply raw material for repair, growth and development of body.
• To supply nutrients like vitamins and minerals to maintain proper health.

Life Processes 1
 NUTRITION
It is a physiological process in which living organisms make or obtain material (nutrients) essential for their life
and which supply energy for metabolic activities, growth and tissue repair.

1. Nutrients : The nutrients are organic as well as inorganic substances which organisms obtained from their
surroundings. These are used as an energy source or for biosynthesis of body constituents. Organic
nutrients are carboyhydrates, fats, proteins and vitamins, whereas inorganic substances are water and
minerals.

2. Modes of nutrition
• The ways by which organism obtain its food are called mode of nutrition.
• The mode of nutrition of an organism depends on its morphological structure and physiological
requirement.
• Depending on the modes of obtaining nutrients, all living organisms can be classified into two major
groups.
(i) Autotrophs (ii) Heterotrophs

(i) Autotrophic nutrition : ‘Auto’ means self and ‘troph’ means nutrition. Autotrophic nutrition is such
type of nutrition in which organism is able to prepare its own food from inorganic materials. The organisms
which can make their own food are called autotrophs.
E.g.: All green plants and few bacteria (autotrophic bacteria) are able to synthesis their food by the
process of photosynthesis.

Autotrophic nutrition is of two types

(a) Photosynthetic nutrition (b) Chemosynthetic nutrition

(a) Photosynthetic nutrition : Sunlight is essential for the synthesis of food in the presence of
photosynthetic pigment, chlorophyll along with carbon dioxide and water.
Chlorophyll
6CO 2 + 12 H2O Sunlight C6H12O 6 + 6H2O + 6O 2

E.g. All green plants and Cyanobacteria.

(b) Chemosynthetic nutrition : Organisms manufacture their food by utilizing energy released as a
result of oxidation of inorganic materials.
E.g. Non-green bacteria, Nitrosomonas (nitrifying bacteria) sulphur bacteria etc.

(ii) Heterotrophic nutrition : The word ‘hetero’ means other and ‘troph’ means nutrition. Thus, heterotrophic
means nutrition obtained from others. Heterotrophic organism are not able to synthesise their own food
and hence depend on organic sources for food. They obtain food already prepared by plants and are
called consumers. e.g. : Non-green bacteria, animals, fungus etc.

Types of heterotrophic nutrition : It is of three main types on the basis of mode of feeding :
(a) Saprotrophic nutrition : ‘Sapro’ means rotten Saprophytic organisms absorb their organic nutrition
from dead and decaying organisms (plants and animals). Such organisms secrete certain enzymes
which hydrolyse complex molecules of dead organisms.
E.g. Bacteria, fungi, etc
(b) Holozoic nutrition : ‘Holos’ means whole and ‘zoikos’ means animals.
Holozoic nutrition means ‘feeding on solid food’. This solid food may be a plant product or an
animal product.
In this mode of nutrition, 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.
E.g. Man, frog, lizard, bird, and amoeba.

2 Life Processes
 Table : Holozoic nutrition in different heterotrophs
S.No. He te rotrophs Na ture of food Ex a m ple s
1. S cavengers Feeding on dead animal V ultures, kites, hyaena etc.
2. S anguivorous Blood sucking animals Mosquito, leech etc.
3. Herbivores Feeding on plants Rabbit, cow , horse, goat etc.
4. Carnivores Feeding on other animals Lion, tiger etc.
5. Omnivores Feeding on both plants and Humans, cockroach, crow, pig etc.
anim als
6. Insectivores Feeding on insects Common bat, frog, lizard etc.

(c) Parasitic nutrition : When an organism (plant and animal) lives in or on the other organism from
which it obtains its nutrition is called a parasite and the mode of nutrition is called parasitic mode
of nutrition. The organism from which a parasite obtains food is called the host. Plant parasites
such as Cuscuta suck food from the host with the help of specilised absorbing organs called
haustoria. Animal parasites are Entamoeba hystolytica, giardia, protozoa, mosquitoes etc.

Nutrition can be divided into two categories on the basis of occurence

Nutrition in plants Nutrition in animals

NUTRITION IN PLANTS

• Plants are autotrophic in nature.

• They are also called as producers because they prepare their own food as well as provide energy to the
heterotrophs at different levels.
• Plants contain a green pigment called chlorophyll which can
entrap solar energy (photo energy) which is then converted
into chemical energy in the form of food and the process is
Sun
called as photosynthesis.

1. Photosynthesis : ‘Photo’ means light and ‘synthesis’ means

to build.
CO

• Photosynthesis is the process by which green plants

O2

Chloroplast
2

prepare their food (glucose) in the presence of sunlight

and chlorophyll with the help of simple inorganic molecules
like carbon dioxide and water.
• Oxygen is released as a by-product during this process. Water
Green plants exchange gases in
• The process of photosynthesis can be represented as atmosphere and absorb water from
Sunlight soil during photosynthesis
6CO 2  12H2O 
Chlorophyll
C6H12 O6  6H2 O 6O2 
Carbon dioxide Water Glucos e water Oxygen
(From air ) (From soil) (Food)

2. Site of photosynthesis

• Site of photosynthesis is different in prokaryotes and eukaryotes.

In prokaryotes – Photosynthesis occurs in lamellar chromatophores.

Life Processes 3
 Diagram - Nostoc

• In higher plants – Chloroplast is the main site of photosynthesis.

Xylem
Single
Cuticle Vascular bundle
Phloem palisade
cell
Upper epidermis Cell wall

Chloroplasts
Palisade cells
Cytoplasm

Sap vacuole
Spongy mesophyll Nucleus

Lower epidermis Sub-stomatal air chamber

Single
Stoma Guard cell spongy mesophyll
cell

The structure of a leaf showing chloroplast

3. Chloroplasts
• The chemical reaction during photosynthesis takes place in chloroplast.
• Chloroplasts are found in the plant cells.
• They are green in colour due to presnece of chlorophyll and present in green parts of plant.

• Shape – Variable – Lower group (eg. algae) – cup or ribbon shaped

Higher plants – Discoidal
• Light reaction of photosynthesis occurs in grana and dark reaction takes place in stroma of chloroplast.

4 Life Processes
 Loop of
Outer DNA Frets or stroma lamellae
Membrane
Granum
Stroma
Intermembrane
space

Inner
Membrane Thylakoid
Granum in L.S. Lipid globule
Ribosomes RNA

Internal structure of chloroplast

4. Requirement for photosynthesis : It is been found by experiments that the conditions necessary for
photosynthesis to take place are the presence of (i) Essential elements (ii) Raw material
(i) Essential elements of photosynthesis
(a) Sunlight
• The radiant energy source for plants is sun.
• Light is the visible part of electromagnetic radiation.
• Visible region consists of white light which is a mixture of 7 lights of different wavelengths.
• Plants utilize the light in the visible region of solar spectra (400 nm – 700 nm).
• There is minimum photosynthesis in green region because green parts of plants reflect whole
of the green light.

400 nm 700 nm
300 nm (4000 Å) (7000 Å) 2600 nm
Ultra-Violet Infra-Red
Radiation V I B G Y O R Radiation

• Maximum rate of photosyntheis occurs with Blue and Red light of VIBGYOR
(b) Chlorophyll
• Green pigment.
• Present in the chloroplast.
• Found in green leaves in maximum amount as well as in other green axial parts of plant.
Sun
(ii) Raw materials of photosynthesis
(a) Carbondioxide
Food goes up Carbon dioxide Sunlight
• Terrestrial plant obtain CO2 from the atmosphere
Oxygen
throught the small openings present on leaves
called as stomata. glucose
food
• They are the small pores present on the surface
Starch
of leaves. (stored food)

• They help in exchange of gases from outer Stem Food goes

Green leaf
down
environment to leaf surface.
• In aquatic plants, CO2 is dissolved in water and
Roots
was absorbed by their body surface, hence they
perform more photosynthesis than terrestial plants. Soil water

Green plants make their own

food by photosynthesis

Life Processes 5
 (b) Water
• It is the essential part of photosynthesis as to
liberate out O 2.
• Water is absorbed by simple osmosis through
plant roots.
• The concentration of water is more in soil as compared to plant roots.
• The water is transported from roots to leaves by xylem.
5. Opening and closing of stomata : The epidermis of leaves bears a number of aerating pores called stomata.
Each aerating or stomatal pore is bordered a pair of guard cells.
Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of
photosynthesis. But it is important to note here that exchange of gases occurs across the surface of stems,
roots and leaves as well. Since large amounts of water can also be lost through these stomata, the plant closes
these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a
function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open.
Similarly the pore closes if the guard cells shrink.

Subsidiary cell
Potassium ions
Flaccid guard cell
Turgid guard cell
Stoma closed
Vacuole filled with water

Stoma open
(a) (b)

Opening and closing of stomata. [a. open stomata, b. closed stomata]

6. Mechanism of photosynthesis : It consists of following steps

(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and
oxygen.
(iii) Reduction of carbon dioxide to carbohydrates.

7. Significance of photosynthesis : Photosynthesis is considered the most important process in the

biosphere because of the following reasons
• All green plants are called producers because they synthesize organic food material for living organisms.
The animals and heterotrophic plants (i.e., the consumers) depend directly or indirectly on producer
plants for their requirement of organic food.
• It also maintains the level of atmospheric oxygen which is continuously consumed by plants and
animals during respiration.
• Molecular O 2 released from photosynthesis is also utilized in making ozone (O 3) in the outer layer of
atmosphere. The ozone layer acts as screen and helps in stopping the highly destructive ultraviolet (uv)
rays from reaching the earth.
• Photosynthesis consumes atmospheric carbon dioxide which is being continuously added by the
respiration of organisms and burning of organic fuels. Thus, this process acts as purfier of atmosphere.

8. Activities related to photosynthesis

(i) Experiment to show that chlorophyll is neccessary for the process of phototsynthesis
• Take a potted plant like croton plant or variegated leaves whose leaves are partly green and partly
non green. The green part of the leaf has chlorophyll but the non green part of the leaf does not have
chlorophyll.
• Place this plant in a completely dark place for about three days to destarch its leaves.
• Take out the potted plant from the dark place and keep it in bright sunshine for three to four days.

6 Life Processes
 Experiment to show that chlorophyll is necessary for photosynthesis
• Boil these leaves in water for a few minutes and then remove its green colour ‘chlorophyll’ by boiling
it in alcohol.The green parts of the leaf get decolourised.
• Wash the decolourised leaf with hot water to soften it and remove any chlorophyll.
• Pour iodine solution over the colourless leaf and observe the change in colour of the leaf.
• The outer part of leaf that was originally non green (without chlorophyll) does not turn blue-black on
adding iodine solution showing that no starch is present in this outer part of the leaf.
• From this observation, we conclude that the photosynthesis to make starch does not take
place without chlorophyll.
• The inner part of leaf which was originally green (contained chlorophyll) turns blue-black on adding
iodine solution showing that starch is present in this inner part of the leaf. From this observation
we conclude that the process of photosynthesis to make starch takes place in the presence
of chlorophyll.

(ii) Experiment to show that carbon dioxide is neccessary for the phototsynthesis
• Take two healthy potted plants which are nearly the same size.
• Keep them in a dark room for three days.
• Now place each plant on separate glass plates.
• Place a watch-glass containing potassium hydroxide by the side of one of the plants. The potassium
hydroxide is used to absorb carbon dioxide.
• Cover both plants with separate bell-jars as shown in figure.
• Use vaseline to seal the bottom of the jars to the glass plates so that the set-up is air-tight.
• Keep the plants in sunlight for about two hours.
• Pluck a leaf from each plant and check for the presence of starch with iodine solution.
• We conclude that only leaf from the plant which was kept without KOH will show blue
color as CO 2 has not been absorbed so available for photosynthesis.

Bell jar
Watch-glass
containing
potassium
hydroxide
(A) (B)
Experimental set-up
(a) with potassium hydroxide
(b) without potassium hydroxide

Life Processes 7
NUTRITION IN ANIMALS

• Animals are heterotrophic in nature . They are directly or indirectly dependent on plants to obtain their food
• Nutrition in animals consists of following steps
- ngestion : The process of intake of food.
- Digestion : It is the breakdown of large and complex molecules into simpler, smaller and soluble forms.
- Absorption : Taking up of the digested food through intestinal wall to blood or body fluid.
- Assimilation : In this process absorbed food is taken by body cells.
- Egestion : The process by which undigested matter is expelled out.

1. Nutrition in Amoeba : Amoeba is an aquatic protozoan animal which lives at the bottom of fresh water
bodies or on submerged objects.The animal has no mouth or a fixed place for the ingestion of food. It feeds
on microscopic animals (other protozoans), bacteria, decaying food particles and microscopic plants that
float in the water body. The mode of its nutrition is holozoic and the process of obtaining food is called
phagocytosis. The nutrition involves following five steps

(i) Ingestion. It involves intaking of food. Amoeba engulfs the microscopic food particle by forming
pseudopodia around it. The pseudopodia are temporary processes which help in locomotion and food
capture. The food particle gets surrounded by encircling pseudopodia which touch each other by their
tips. At this moment the membrane closer to food particle gets dissolved and the food is encaptured
along with a few lysosomes (present in the cytoplasm) into the cell in the form of a bag called food
vacuole. Further process takes place inside the food vacuole. The process of ingestion is also known
as phagocytosis.

Food Engulfed food Assimilation of Undigested food

Pseudopodia vacuole within food vacuole digested food thrown out

Food
particle

(i) Ingestion (ii) Forming food (iii) Digestion (iv) Assimilation (v) Egestion
vacuole
Nutrition in Amoeba

(ii) Digestion: The food is converted into soluble form in food vacuole with the help of several digestive
enzymes (present in the cytoplasm). This is called digestion.
(iii) Absorption: The digested food present in the food vacuole is absorbed directly into the cytoplasm of
the cell by the process of diffusion.
(iv) Assimilation: The digested food components are soluble and can easily diffuse into the cytoplasm
passing through the membrane of food vacuole. It is then utilised by the cell. Utilisation of simple food
components by the cell is called assimilation.
(v) Egestion: The portion of food which is not digested and assimilated remains in the food vacuole.
The undigested food is then thrown out of the body at any point on the cell surface. This process of
elimination of undigested food is called egestion.

2. Nutrition in Paramoecium : Paramoecium, is also a unicellular organism that lives in water. 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 the entire surface of the cell. Fine food particles enter through the cell mouth and are rapped
of in the food vacuole. This is the first step of the nutrition, called ingestion. Ingestion is followed by other
steps such as digestion, asborption, assimilation and egestion .

8 Life Processes
 Food Food
vacuole particles

Oral groove
Cytosome

Formation
of food
vacuole

Anal pore

Nutrition in Paramoecium
3. Nutrition in human beings : Human beings are heterotrophic omnivorous organisms. They obtain their
food from plants, animals and their products by holozoic mode of nutrition.
• The essential components of human diet are water, carbohydrates, fats, proteins, minerals, vitamins
and roughage.
• The human digestive system consists of (A) an alimentary canal and (B) many digestive glands.
• Parts of the body concerned with the uptake and digestion of food and elimination of undigestable
remains form the digestive system, also called alimentary system.

Structure and function of the main organs of alimentary canal : The alimentary canal is a long tube
with muscular walls, glandular epithelial lining and varying diameter. It extends from the mouth to the anal
opening (anus). When uncoiled, the alimentary canal measures nearly 9 metre long tube in which the ducts
of several digestive glands open to secrete their respective digestive secretions. The alimentary canal consists
of several organs. These organs are given below in the order in which they are involved in digesting food

Digram : Human Digestive System

Life Processes 9
(A) Alimentary canal:-

(i) Mouth : The mouth is a transverse slit. It is bounded by two soft, movable lips. The lips are covered
with skin on the outer side and lined with mucous membrane on the inner side.
Oral (Buccal) cavity. It is a large space bounded above by the palate, below by the tongue and on the
sides by the jaws.The jaws bear teeth. The buccal cavity is lined by stratified squamous epithelium.
It contains the following parts
(a) Palate : Roof of buccal cavity is called palate.
(b) Tongue. The tongue is a large, muscular, highly mobile organ. It lies mainly in the oral cavity and
partly in the pharynx. Its base is fixed due to attachment with hyoid bone.
Papillae: Upper surface of the tongue bears numerous papillae that contain taste buds.
Functions: The tongue has many functions.
• It is an organ of taste. Its taste buds are sensitive to four tastes salty, sour, bitter and sweet.
• It helps in chewing by sending the food under the grinding teeth.
• It aids in swallowing by pushing the food bolus backward.
• It acts as a brush to clean the teeth.
• It also plays a role in speech. It helps in forming words along with lips, teeth and hard palate.
(c) Teeth : Teeth are present in the jaws as semicircular arches.
• The teeth are embedded in sockets of the jaw bones named maxillae and mandible. Such teeth
are described as thecodont.
• The food taken inside oral cavity is masticated i.e. mechanically broken into smaller particles
before being swallowed by the help of teeth.
• There are 32 teeth in the permanent set. Each jaw has two pairs of incisors, one pair of canines,
two pairs of premolars and three pairs of molars and the milk set consists of only 20 teeth.
• The number of teeth is fixed and they are produced in two sets temporary or milk and
permanent.
• Jaws present in buccal cavity are provided with four different types of teeth
ncisors : For cutting
Canines : For tearing
Premolars : For grinding
Molars : For grinding

Half upper jaw 2 1 2 3

Dental Formula :-  2  I =  2, C   2, PM   2, M   2
Half lower jaw 2 2 2 3

10 Life Processes
DO YOU KNOW?
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. Dentine is simililar to bone. Inside the dentine is pulp cavity.
The pulp cavity contains nerves and blood vessel. The formation of small cavities (or holes) in the teeth due to
the action of acid-forming bacteria and improper dental care is called Dental caries.
If the teeth are not cleaned regularly, they become covered with a stickly, yellowish layer of food particles and
bacteria cells ‘dental plaque’. Since plaque covers the teeth forming a layer over them, the alkaline saliva
cannot reach the tooth surface to neutralise the acid formed by bacteria and hence tooth decay sets in.

Incisor
Canine

Premolars

Molars Socket
of jaw

Arrangement of different types of teeth in the jaws on one side and

the sockets on the other side

(ii) Pharynx : The pharynx is about 12 - 14 cm. long vertical canal beyond the soft palate. The food and air
passages cross here.
Function: The function of the pharynx as a part of the digestive tract is merely to serve as a passage
way-for the food from the oral cavity to the oesophagus. It has in its walls the voluntary muscles which
start swallowing movements.
(iii) Oesophagus : The oesophagus is a approx 25 cm. long, narrow, muscular, straight tube lined by stratified
squamous epithelium containing mucous glands. It is also called is food pipe. Opening of food pipe
is called as gullet. It runs downward through the neck behind the trachea and through the thorax
behind the heart, and passes through the diaphragm into the abdomen.
Function : The oesophagus serves to convey the food by peristalsis from the pharynx to the stomach,

DO YO KNOW ?
• Peristalsis : It is a series of contraction and relaxation of muscles of alimentary canal that pushes the food
downward.
(iv) Stomach : The stomach is a wide, J-shaped, distensible, muscular sac placed obliquely on the left side
in the upper part of the abdomen just below the the diaphragm. It is about 30 cm long and 15 cm wide.
Functions : The stomach serves 4 main functions
• Storage of food.
• Mechanical churning of food.
• Regulation of the flow of food into the small intestine.
• Storage of food in the stomach enables us to take food at intervals as a meal instead of continuously
(v) Small intestine : It is convoluted tube and differentiated into 3 regions, viz. duodenum which is the
first part of small intestine and curved C-shaped, jejunum which is comparatively longer and more
coiled and ileum which is the last part of small intestine.The inner surface of small intestine forms
numerous finger like projections called as villi, which increase the surface area for absorption of the
products of digestion. i.e., Glucose, Amino acid, fatty acid and glycerol.
Functions : The small intestine serves 2 main functions
• Completion of digestion
• Absorption of digested food, with the help of villi and microvilli present in the walls of the small intestine.
• The duodenum part of small intestine receives secretions from liver and pancreas through a common
duct called the "Hepato-Pancreatic Duct".

Life Processes 11
 (vi) Large intestine
• It is much shorter & wider than small intestine & is differentiated into three regions.
(a) Caecum :- It is small rounded blind sac from which vermiform appendix arises.
(b) Colon :- It is the inverted U-shaped tube.
(c) Rectum:- It is opens to exterior through anus.
• No digestion takes place in large intestine, only absorption of water takes place.
• In herbivores like horse, rabbit digestion of cellulose takes place in caecum.

Functions : The large intestine mainly aids in the absorption of water ; formation, temporary storage
and elimination of faeces; and production of mucus for lubrication of mucosa. It also plays some role in
digestion, absorption and excretion.

Absorption of digested product : Digested products are absorbed mainly through micro villi present on
the wall of small intestine. W ater and water soluble substance are absorbed by osmosis. Some sugars
which is insoluble absorbed by facilated diffusion. Nutrients like amino acids are actively transported.
The products of fats like monoglycerids, fatty acids and glycerols are water insoluble which are firstly
incoperated into water soluble droplets. They are released into lymph.
Assimilation : It is the process of utilisation of absorbed food for various body functions. The absorbed
nutrients are utilised to resynthesise complex molecules like carbohydrates, protein & fats inside the cells.
Man cannot digest cellulose.
Egestion : Peristalsis gradually pushes the undigested material into large intestine or colon. About 1500ml
of chyme passes into the small intestine each day where most of the water, electrolytes and ions are
reabsorbed.
(B) Digestive glands
(i) Salivary glands : There are three pairs of salivary glands in oral caivty. These secrete saliva.
Digestion : Saliva contains salivary Amylase, bicarbonate ions and Lysozymes
• Salivary amylase converts starch into simple sugars.
• Salivary amylase is also called as ptyalin enzyme.
• This enzyme works in saliva in almost neutral medium
• Bicarbonate ions neutralise the acids in food.
• Lysozyme in saliva acts as antimicrobial enzyme.
Sali var y
Starch   Simple Sugar (Maltose)
amylase

(ii) Gastric glands : It contains gastric glands it secrete HCl, mucus and protein digesting enzymes.
(a) Mucus : secreted by the stomach wall protects its wall from its own secretion of HCl.
(b) HCl :- maintain strongly acidic pH (1.5 – 2.5)
Functions : It kills harmful bacteria.
• It provides acidic medium for gastric digestion
• It changes inactive enzymes into Active one.
• It soften’s the food and dissolve them to make them readly available for enzyme action.
• It stops the action of salivary amylase.
(c) Protein digestive enzyme :- It digests protein and convert it into peptides.
Digestion:
HCl
Pepsinogen  Pep sin
Pep sin
Proteins   peptides
(iii) Liver : It is the largest gland, secrets bile into the small intestine. Bile contains bile salts and bile
pigments. Bile is an alkaline in nature and it is temporarily stored in gall bladder and helps in
emulsification of fats. It also helps in absorption of fats.
(iv) Pancreas : It is situated below the stomach. It secretes pancreatic juice which contains enzymes like
trypsin and lipase. This juice is released into duodenum.

12 Life Processes
 Gall bladder

Duct from Ducts

gall bladder from liver

Common
bile duct
Pancreas

Pancreatic
Duodenum duct

Hepato-pancreatic duct
The duct systems of liver, gall bladder and pancreas

Table : Digestive glands, their secrections and action

TABLE : DIGESTIVE Table : Digestive Glands, Their Secretions & Action

Name of
S.N. Secretion Enzyme Site of action Substrates Products
Gland
Salivary Salivary amylase Buccal cavity Starch Maltose
1. Saliva isomaltose
gland
(a) Pepsin Stomach Protein Peptones
(Pepsinogen inactive)
Gastric
2. Gastric juice
glands (b) Rennin (Prorennin Stomach Casein Paracasein
inactive)
(c) Hydrochloric acid Stomach Pepsinogen Pepsin
(a) Pancretic Small intestine Starch Maltose
amylase isomaltose
(b) Trypsin Small intestine Proteins Peptides
Pancreatic (Trypsinogen
3. Pancreas inactive)
juice
(c) Lipase Small intestine Lipids Fatty acid and
Glycrol

(a) Enterokinase Small intestine Trypsinogen Trypsin (active)

(Enzyme) (inactive)
(b) Dipeptidases Small intestine Dipeptides Amino acids
Intestinal Intestinal
4. (c) Maltase Small intestine Maltose 2 Glucose
gland juice
(d) Sucrase Small intestine Sucrose Glucose, Fructose
(e) Lipase Small intestine Triglycerides Monoglycerides
eg. Fatty acids
Bile (Bile salts No enzymes Duodenum Fats Fat droplets
5. Liver
+ pigments)

DO YO KNOW ?
• Reverse peristalsis or retroperistalsis is the reverse of peristalsis, usually occur before vomiting
• Peptic ulcers are sores or ulcers in the lining of the stomach, lower oesophagus, or small intestine, usually
as a result of inflammation caused by the bacteria.

Life Processes 13
 RESPIRATION
A common man understanding of respiration is intake of oxygen (of air) and release of carbon dioxide which is
infact a kind of gaseous exchange. The scientific meaning of respiration is a complex process involving gaseous
exchange and break down of simple food
The process by which assimilated food is oxidised and energy is released is called as respiration.

1. Breathing :- It is a kind of ventilation in which the organisms take oxygen from the environment and
release carbon dioxide.
Cellular respiration :- It is a much more complex process that occurs inside the living cells. It is the
oxidation of respiratory substrate (mainly glucose) in the cells resulting in the release of carbon dioxide
and energy. Release of energy is in the form of ATP molecules inside the cell for further use and the waste
products i.e., CO 2 and H2O are eliminated out of the body.
oxidation
Food + O 2  CO 2 + H2O + Energy (ATP)

Table : Difference between breathing and cellular respiration

S.NO. Breathing Cellular Respiration

It is a physical phenom enon where exchange It is a biochem ical proces s where glucose is oxidised
1.
of oxygen and carbon dioxide takes place to produce carbon dioxide and water

2. No energy is released Energy is released

3. It is extracellular It is intracellular
A series of respiratory enzym es are involved to bring
4. No enzym es are involved
about the oxidation

Table : Differences between respiration and combustion

S.NO. Re spira tion Com bustion
1. It is a biochemical process. It is a chemical process.
It takes place at normal It takes place at
2.
temperature. high temperature.
Respiration is a slow process that is Combustion is fast process in which the
com pleted in several steps.Thus, the energy is liberated only in one step resulting
3. energy is also liberated in several steps in increase in temperature and production of
and remain stored in the form fire.
of ATP.
A series of respiratory enzymes are
4. No enzymes are involved.
involved.

2. Activity : To demonstrate that we breathe out carbondioxide.

Apparatus and materials required : 2 test tubes, freshly prepared lime water, glass tube, and syringe
Procedure : Take two test tubes (a) and (b) Pour some freshly prepared lime water in each test tube. Now
blow air in test tube (b) in lime water through glass tube. Pass air through lime water of test tube (a) by a
syringe and observe.
Observation : - In test tube (b) lime water turns milky within a short period of time. In test tube (a) the lime
water takes a very long time to turn milky
Conclusion :- Lime water turns milky only when carbon dioxide mixes with it. The lime water (solution of
calcium hydroxide) combines with carbon dioxide to form a white precipitate of calcium carbonate.
Ca(OH) 2 + CO2 
 CaCO 3 + H2 O
(Calcium hydroxide) (Calcium carbonate white ppt)

Experiment shows that exhaled air contains good amount of carbon dioxide and proves that carbon dioxide
is produced during respiration. On the other hand very little amount of carbon dioxide is present in fresh air.

14 Life Processes
 Pichkari

Rubber Tube
tube

Test tube containing

Lime lime water
water

(a) (b)
(a) Air being passed into lime water with a pichkari/syringe.
(b) Air being exhaled into lime water

3. Types of respiration : Mechanisms of respiration vary among different groups of animals depending mainly
on their habitats and levels of organisation.
It is of two types
(i) Aerobic respiration : In most animals and plants, respiration involves use of molecular oxygen and
release of carbon dioxide simultaneously. Such a respiration is called aerobic respiration. The
organisms which carry on aerobic respiration are termed as aerobes.
Glycolysis In presence of O2
Food In cytoplasm Pyruvic acid 6CO 2 + 6H2O + 38 ATP
TP
Kreb cycle in mitochondria

DO YOU KNOW ?
Cutaneous respiration : The exchange of respiratory gases through the vascular skin is called cutaneous
respiration. It takes place in annelids, and amphibians. It can function in water as well as on land. Skin, in
these animals, is suitable for exchange of gases as it is thin, kept moist, permeable, and well vascular.

(ii) Anaerobic respiration : In some organisms, respiration may or may not produce carbon dioxide and
does not utilize molecular oxygen. For example, yeast oxidizes glucose to ethanol (ethyl alcohol) and
carbon dioxide without utilizing oxygen
C6H12O6  2C2H5OH + 2CO 2 + Energy..
The process of releasing energy without the use of oxygen is called anaerobic respiration. It is also
termed fermentation.
Activity : To demonstrate the process of fermentation
Apparatus and materials required : Fruit juice or sugar solution, test tubes, one hole cork, bent
glass tube, freshly prepared lime water, yeast
Procedure : Take some fruit juice or sugar solution in a test tube and add some yeast into it. Close
the opening of test tube with a one hole cork. Insert a bent glass tube in the cork and dip the other end
of tube into the test tube containing freshly prepared lime water (solution of calcium hydroxide). Observe
after few hours.
Observation and result : The lime water turns milky. This shows that carbondioxide is liberated from
the mixture of sugar solution and yeast. Fermentation of sugar results in the production of ethyl alcohol
and CO 2.

Life Processes 15
 CO 2 produce during the process of fermentation (Yeast reacting with sugar solution)
C6H12O6
Glucose (1 molecule)
(6-Carbon molecule)

In Cytoplasm –Glycolysis

Pyruvic acid + Energy

(3-carbon compound, 2 molecule)

Presence of
Absence of oxygen
oxygen
Lack of oxygen In mitochondria –Kreb's cycle

In Yeast
In our
muscle
cells
Ethanol + CO2 + Energy CO2 + Water + Energy
(2-carbon molecule)
Lactic Acid + Energy
(3-carbon molecule)

Breakdown of glucose by various pathways

Anaerobic respiration also occurs inside the muscles during vigorous muscular activities. It usually
occurs during the phase when oxygen gets used up faster than it is available for oxidative break down
of respiratory substrates. In this case, the oxidation of glucose results in the production of lactic acid.

Table : Difference between anaerobic and aerobic metabolism

S .No . Ae ro b ic m e ta b o lism An a e ro b ic m e ta bo lism
1. It us es m olec ular O 2 It does not us e m olec ular O 2 .
2. It alway s releas es CO 2 It m ay or m ay not releas e CO 2 .
3. It produc es H 2 O It does not produc e H 2 O .
4. It provides m uc h m ore energy (whole of that It provides les s energy (only 5% of that
available in gluc os e available in gluc os e).
5. The ox idation of one m olec ule of gluc os e 38 The no. of A TP m olec ules produc e is
A TP m olec ules . only 2 produc es
6. It c ons is ts of four s teps : gly c oly s is , py ruvate It c ons is ts of 2 s teps : gly c oly s is and
ox idation, TCA c y c le and E TS . inc om plete break down of py ruvate.
7. It oc c urs partly in the c y toplas m and partly in It oc c urs in the c y toplas m only .
the m itoc hondria.
8. It is found in the m ajority of anim als and It is oc c urs in a few organis m s s uc h as
plants . y eas ts , bac teria and paras itic worm s .

16 Life Processes
EXCHANGE OF GASES IN PLANTS
Since the aerobic respiration pathway requires presence of oxygen, aerobic organisms must have a mechanism
to ensure a continuous supply of oxygen. Earlier we have seen that photosynthetic process in green plants
needs carbon dioxide and releases oxygen. This exchange of gases occurs through following ways:

1. leaves and young stems:- Surface of leaves and young stem possess numerous tiny pores called as
stomata in their epidermal cells, exchange of gases takes place through stomata and when CO2 concentration
in cell increases stomata opens and CO 2 is released out.
The direction of diffusion depends upon the environmental conditions and the requirements of the plant. At
night, when there is no photosynthesis, CO 2 elimination is the major exchange activity while during day
CO 2 produced during respiration is utilized by photosynthesis, so O 2 release is major event in day time.

2. By young root :- Air occurs in soil interspaces. Root hairs of plants as well as epiblema cells of the young
roots are in contact with them.

Respiration in roots through root hair

3. Respiration in stem : In hard and woody stems of big plants and trees, lenticels are present in place of
stomata through which exchange of gases takes place.

Lenticle

Cork
Cork
Cambium

Respiration in woody stem through lenticels

Life Processes 17
 RESPIRATION IN HUMAN
Respiratory tract serves as a passage way for the fresh air to flow from outside to the lungs and for the foul air
to return from the lungs to the exterior. Gas exchange does not occur here.
Fresh air route
External Nares  Nasal Chambers  Internal Nares  Pharynx  Glottis
 Larynx  Trachea  Bronchi  Bronchioles  Alveolar Ducts
s  Alveoli.

1. Structure of respiratory tract

The respiratory tract consists of following components
(i) External nares (Nostrils) : The external nares are a pair of slits at the lower end of the nose. They
open into the nasal chambers.
(ii) Nasal chambers / nasal cavity : Nasal cavity is meant for inhalation of air from out side. The Nasal
chambers are a pair of passages in the head above the palate. The two chambers are separated from
each other by a median partition, the nasal septum.
(iii) Internal nares : Nasal cavity opens into it and it leads to pharynx.
(iv) Pharynx : The pharynx is a short, vertical, about 12cm long tube behind the buccal cavity. The food
and air passages cross here. Its upper part is called as nasopharynx. The internal nostrils open into it.
It leads into 2 tubes one is wind pipe and 2nd is food pipe or oesophagus.
(v) Larynx: The larynx is the upper part of the trachea. It is short, tubular chamber supported by a
cartilaginous framework. Its opening is called as glottis. The latter always remains open except during
swallowing. The glottis bears a leaf-like cartilaginous flap, epiglottis.It also serve as the voice box.
(vi) Trachea : It is a thin-walled tube, about 10-12cm long and 1.5 - 2 cm wide. It is also called as wind
pipe. It extends downwards through neck. It’s walls are supported by 16-20 C-shaped cartilagenous
rings which prevent them to collapse when air is absent in them.
(vii) Bronchi : In the middle of the thorax, trachea divides into 2 tubes, the primary bronchi. One major
primary bronchus enters the right lung and other in left lung. This primary bronchus further divides into
secondary bronchi.
(viii) Lungs : These are two light weight spongy pouches covered by a membrane called Pleura. Bronchi
are further branched into several bronchioles. At the end of bronchioles alveolar sacs or alveoli are
present which are rich in blood capillaries. Alveoli increase the surface area for exchange of gases. The
membrane of alveoli is very thin and delicate in order to facilitate the exchange of gases.
(ix) Diaphragm: It is a sheet of muscles that lies below the lungs and separates thoracic cavity from
abdominal cavity.
UPPER RESPIRATORY TRACT

Nose
Passageway Nasal cavity
for air Filters, warms and
moistens air
Mouth
Passageway for Pharynx (Throat)
food and air Common passage for
Epiglottis air, food and liquids
covers larynx Larynx (Voice box)
during swallowing Production of sound
Pleural membranes
Trachea (Windpipe)
LOWER RESPIRATORY TRACT

Cover the lungs and line

the chest cavity Branching airways

Lungs organ
of gas exchange Bronchi
Branching airways
Intercostal muscle
Alveoli
Moves ribs during
Air sacs for gas exchange
respiration
Rib

Diaphragm

Skeletal muscle
of respiration
Human respiratory system

18 Life Processes
2. Mechanism of breathing : It includes inhalation and exhalation.
(i) Inhalation: When air is breathed in, the diaphragm and muscles attached to the ribs contract thus
ribs move outward and diaphragm move downward (flat) due to which there occurs expansion of chest
cavity, it results increase in volume of chest cavity. Thus the air pressure decreases and air from
outside rushes into the lungs and alveolar sacs get filled with air containing oxygen. The oxygen
present in air diffuses into the blood and CO2 from blood diffuse out into alveolar sac.
(ii) Exhalation : When air is breathed out the diaphragm and muscles attached to ribs relax thus ribs
move inward and diaphragm move upward (Dome shaped) which brings about contraction in chest
cavity, its volume gets reduced and CO 2 is pushed out from lungs into the air through trachea and
nostrils.

(a) Breathing in : chest cavity becomes (b) Breathing out : Chest cavity becomes
bigger, air is sucked into lungs smaller, air is pushed out of lungs

The mechanism of breathing

DO YOU KNOW?
• Respiratory movements are controlled by Medulla oblongata.
• The lungs have vast surface area for gaseous exchange. In an adult man the alveolar surface area is about
802 m which is about 50 times than that of skin. (1.6 2 m only). Is not it amazing?
• Tidal Volume : Volume of air inspired or expired with each normal breathing.
• Residual Volume (RV) is the volume of air which always remains in the lungs even after maximum or
forceful expiration for gaseous exchange. It means lungs are never empty. An average human has RV of
about 1L.
• In human beings breathing rate is completed in 5 seconds, 2 seconds in inspiration and 3seconds in
expiration.

3. Mechanism of gaseous exchange between tissues and blood

• When the air enters into the lungs through nostrils, trachea and bronchi it enters into the bronchioles,
from bronchioles it moves into thin walled alveolar sacs or alveoli.
• Alveoli are rich in blood capillaries, at this place oxygen from air diffuses into the blood and reaches to
all the cells and tissues of the body. This oxygen now diffuses into the cell and is utilized for the
oxidation of food and production of energy in mitochondria.

• As a result of this carbon dioxide is produced in cells, due to this increased concentration of CO 2 ,it
diffuses into the blood and is brought back to alveoli and expelled out of the lungs through trachea and
nostrils.
• As body size of the animal is very large, only diffusion would not be sufficient to supply the oxygen to
all parts.For this purpose, there is a respiratory pigment called haemoglobin(Hb) which has a very high
affinity for oxygen. Hb is present in red blood corpuscles.
• A normal person has about 15 grams of haemoglobin per 100 ml of blood.

• The exchange of gases is done by blood as following

Life Processes 19
 (i) Transportation of O 2 : The O 2 that diffuses into the blood from the lungs is transported to various body
tissues in the following form :

About 97% of the O 2 that diffuses into the blood combines with haemoglobin of RBCs forming an
unstable compound, oxyhaemoglobin.
lungs
Hb + O2 HbO2
tissue

The remaining 3% O 2 dissolves into water of plasma.

If diffusion were to move oxygen in our body It would take 3 years for a molecule of oxygen to get our
toes from our lungs.

(ii) Transportation of CO 2
CO 2 is more soluble in water, hence is mostly (70 %) transported from the tissues to the lungs in the
dissolved form in blood plasma.

About 23% of carbon dioxide entering into the erythrocytes combines with the globin (protein) part of
haemoglobin to form carbaminohaemoglobin, which is transported to the lungs.

4. Cellular respiration : The biological oxidation of glucose in the cells is called cellular respiration.
C6H12O 6 + 6O 2 6CO 2 + 6H2O + 38 ATP

5. Significance of respiration
(i) Energy production : Respiration provides oxygen for aerobic metabolism to release energy for creating
ATP molecule that later power the body activities.
(ii) Excretion : It excretes CO 2 and volatile substance such as ammonia, ketone bodies, alcohol, water
vapours etc.
Table : Diffrences between respiration and photosynthesis

S.No. Respiration Photosynthesis

1. It is a catabolic process. It is an anabolic process.
2. Carbohydrates are oxidized Carbohydrates are synthesised.
Light energy is stored in the form of
3. Energy is liberated in the form of ATP.
glucose or chemical energy.
The amount of CO2 in the air increases The amount of CO2 in the air decreases
4.
during respiration. during photosynthesis.
It takes place in all the living cells, both green
5. It takes place only in chlorophyllous cells.
and non–green.
6. Dry weight of plant decreases. Dry weight of plant increases.
O2 is utilized and CO2 & H2O are formed. CO2 & H2O are used while O2 is evolved.
7. Sunlight
C6H12O6 + 6O2  6CO2 + 6H2O + energy. 6CO2 + 12H2O Chlorophyl
   C6H12O6+6H2O+6O2
l

DO YOU KNOW ?
• 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. Stay healthy; just say NO
to tobacco and its products!
• Smoking is injurious to health. 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 these hair due to which germs, dust, smoke and
other harmful chemicals enter lungs and cause infection, cough and even lung cancer.

20 Life Processes
 TRANSPORTATION
The body of every organism (plant or animal) is made up of cells.

All the cells of body need oxygen, water, minerals and organic food for their survival and maintenance.

The substances picked up by respiratory organs or food absorbed by alimentary canal, etc. must be supplied to all
the living cells of body by some mechanism of transportation from the place of their abundance to the places of their
scarcity.

Such coordinated processes carrying out proper distribution of materials among the cells are considered as transpor-
tation.

Transportation is a life process in which a substance synthesized or absorbed in one part of the organism
is carried to other parts of its body.

Transportation

Transportation in plants Transportation in animals

It occurs in two ways It is also known as circulation.
(a) Ascent of sap (transport of water It consists of two types of systems
and minerals) (a) Blood circulatory system
(b) Transport of nutrient and other substances (b) Lymphatic system
by phloem. It is known as translocation

TRANSPORTATION IN HIGHER PLANTS

The higher plants have specialized system for the transportation of materials inside the body. This system is called
vascular system or vascular tissues. The vascular tissue consists of xylem and phloem.

1. Transportation of water : It is carried out by special type of tissue called xylem.

(i) Xylem tracheids
(ii) Xylem vessels
(iii) Xylem parenchyma
(iv) Xylem sclerenchyma

Function : It helps in transportation of water and minerals which is called “ascent of sap”. It helps in providing
mechanical support.

To explain the transportation of water following theories have been proposed.

(i) Root pressure theory : Root hair absorb water from the soil through osmosis.This water is collected in
cells of cortex.
The cortical cells having elastic walls become fully turgid, exert pressure on their fluid contents and force
them towards xylem vessels.So this intermittent pumping action creates pressure in root which forces water
up in xylem vessels.
The effect of root pressure is more significant in night than day time when transpiration pull becomes the
major factor in transportation of water.
However, this pressure is not enough to move water over the heights in tall plants. There is another theory to
explain movement of water in xylem upwards to the highest point.

Life Processes 21
 (ii) Transpiration pull theory : This theory was originally given by Dixon and Jolly. It is based on.
(a) Cohesive and adhesive properties of water molecules to form and unbroken continuous water column in
xylem.
(b) Transpirational pull.
• The main loss of water is through stomatal transpiration.
• Water evaporates from the surface of the cells into the air spaces of the spongy tissues and then
passes into the outer atmosphere through the pores or stomata.
• The cell sap of mesophyll cells becomes concentrated by losing water and causes a drop in turgor
pressure.
• As a result water is sucked from adjoining mesophyll cells and ultimately from vascular tissues.
• This tension is transmitted all the way down to the unbroken column of water through the stem to the
absorbing parts of the root.
• The molecules of the water show cohesion (mutual attraction) and molecules of water and vessel
wall show adhesion (affinity for water). Due to these adhesive and cohesive forces, water column
does not break but pulled upward by the force called as “transpiration pull”.
• The whole process can be compared with a person (transpiration pull) pulling a bucket full of water
(forces on water column) from a well with a rope (column of water due to cohesion).

Transportation of water and dissolved minerals

DO YOU KNOW?
Transpiration : The evaporation of water from the leaves of a plant is called transpiration.
• The continuous evaporation of water (or transpiration) from the cells of a leaf creates a kind of suction which
pulls up water through the xylem vessels.
• Only Two percent of total water absorbed is used up in various metabolic activities in the plant body.
• Importance of transpiration.
- t helps in absorption of water & minerals from the soil.
- It regulates the temperature of the plant.

22 Life Processes
2. Tronslocation of food :- It is carried out by special type of tissue called phloem.
(i) Sieve tubes
(ii) Companion cells
(iii) Phloem parenchyma
(iv) Phloem sclerenchyma
Function : It helps in transportation of food.
Phloem translocates the manufactured food (product of photosynthesis) in the form of sucrose from the leaves to
the different parts of the plant.
The phloem transports amino acids and other substances.
• 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.
• Unlike transport in xylem which can be largely explained by simple physical forces, the translocation in
phloem is achieved by utilising energy.
• 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.

Translocation

TRANSPORTATION IN HUMANS

In humans there is a circulatory system that uses blood or lymph as carriers of materials (fluid exchange medium).
Circulatory system consists of blood vascular system (blood as carrier) and lymphatic system (lymph as carrier).
1. Blood vascular system
Blood vascular system consists of blood, blood vessels and heart.
(i) Blood : The blood is a specialized kind of living connective tissue which is made to circulate, by the
muscular pumping organ called as the heart.
• In adult human beings there is 5.5 to 6 litre of blood.
• The formation of blood is called “Haemopoiesis”.
• Blood consists of two parts
(a) Plasma (b) Blood carpuscles

Life Processes 23
 (a) Plasma
• The liquid part (or fluid part) of blood is called plasma.
• The plasma consists of water (90% aaprox.), inorganic and organic substances.
• norganic salts (0.9%) and the organic substances are glucose, amino acids, proteins, hormones,
digested food and waste excretory products.
• Serum is plasma from which fibrinogen is removed.
(b) Blood corpuscles : Blood corpuscles are of three types.
(b.i) Red blood corpuscles (RBCs) or erythrocytes
• Mammalian RBC is a biconcave / disc-like structure devoid of nucleus.
• The number of RBCs is about 5-5.5 million per mm 3 of blood (RBC count).
• The erythrocytes contain haemoglobin.
• 100 ml of blood contains 15 gm of haemoglobin. If the amount of haemoglobin in blood is less, the person
suffers from anaemia.
• The haemoglobin carries oxygen to the different cells of the body.
• The life span of a RBC is 120 days.

(b.ii) White blood corpuscles (WBCs) or leucocytes

• White blood cells are called soldiers of the body.
• This is because they protect the body from the attack of disease-causing germs (pathogens) and other
harmful foreign materials.
(b.ii.i) Granulocytes
In granulocytes the cytoplasm contains granules and the nucleus is multilobed. Neutrophils, Basophils
and Eosinophils are three different types of granulocytes.
(b.ii.ii) Agranulocytes
Monocytes and lymphocytes are two different types of agranulocytes. Lymphocytes secrete antibodies
which destroy microbes.
(iii) Blood platelets
• These are small and without nuclei.
• These help in blood clotting at the site of injury by liberating thromboplastin.

Different types of cells present in blood

Functions of Blood : Blood performs the following functions

• Transportation of nutrients : The digested and absorbed nutrients like glucose, amino acids, fatty
acids are first transported to the liver and then to all the tissues for their storage, oxidation and synthesis
of new substances.
• Transportation of respiratory gases : The respiratory gases (oxygen, carbon-dioxide) are transported
by the blood. Oxygen is transported from the respiratory surface (lung, skin and buccal cavity) to the
tissues and carbon dioxide from the tissues is taken to the respiratory organ for its removal.

24 Life Processes
 • Transportation of excretory products : Different wastes from the different parts of the body are collected
by the blood and then taken to the organs (kidneys, lungs, skin and intestine) from where they are
excreted.
• Transportation of hormones : Hormones are produced by endocrine glands. These hormones have
target organs (place to act). These are carried by the plasma of blood and bring about the coordination
in the working of the body.
• Maintenance of pH : The plasma proteins act as buffer system and maintains required pH of the body
tissues.
• Regulation of body temperature : The blood flows in all the parts of the body, so it equalizes the body
temperature. It carries heat from one place to another place in the body.
• Transportation of metabolic intermediates : The blood carries metabolic intermediates from one
tissue to another for further metabolism. In the muscle cells due to anaerobic respiration lactic acid is
produced. This lactic acid is carried to the liver for further oxidation.
• Water balance : The blood maintains water balance to constant level by distributing it uniformly in the
body.
(ii) Blood vessels : These are hollow tubes through which the blood flows.
(a) Arteries : These are thick walled and deep seated blood vessels which generally carry the oxygenated
blood away from the heart to various body parts.
(b) Veins : These are thin walled and superficially located blood vessels which generally carry deoxygenated
blood from the body parts to heart.
(c) Capillaries : The capillaries are thin walled and extremely narrow tubes or blood vessels which connects
arteries to veins. The exchange of various materials like oxygen, food , carbon dioxide, etc. between the
blood and the body cells takes place through capillaries.
Table : Difference between artery and vein

S.NO. Characters Artery Vein

1. Direction of blood flow Away from the heart. Towards the heart.
2. Nature of blood Generally oxygenated. Generally deoxygenated.
3. Position Deep seated. Superficial.
4. Nature of wall Thicker & more elastic Thinner & less elastic.
5. Pressure & s peed of blood. At higher pressure & faster. At low pressure & slower.
6. Valves Absent Present

(iii) Human heart

Internal structure of human heart

Life Processes 25
 • Heart is a hollow muscular organ that lies obliquely in the thoracic region in a cavity between the two
lungs that is pericardial cavity.
• Heart is made up of 4 chambers, upper 2 chambers are auricles or atrium and the lower 2 chambers are
ventricles. Auricles are the receiving chambers and ventricles are the pumping chambers. Walls of
ventricles are thicker as they have to pump the blood.
• Four pulmonary veins enter into left auricle, two from each lung bring oxygenated blood.
• From left ventricle aorta takes the oxygenated blood to all body parts.
• Right auricle has openings for venacava that brings deoxygenated blood from the body. Blood enters into
right ventricle through tricuspid valve.
• From right ventricle pulmonary artery carries deoxygenated blood to lungs.
• The series of events which occur during one heart beat is called as cardiac cycle.

Types of circulation
(a) Single circulation : In this, blood passes once through the heart to supply once to the body. It is found
in fishes which have two chambered (one auricle and one ventricle), venous and branchial heart.
(b) Double circulation : A circulatory system in which the blood travels twice through the heart in one
complete cycle of the body is called double circulation. Double circulation involves two circulations
(b.i) Systemic circulation : Blood completes its circulation from left ventricle to right auricle through the
body organs.
(b.ii) Pulmonary circulation : Blood completes its circulation from right ventricle to left auricle through the
lungs.

Double circulation in human body

DO YOU KNOW ?
Blood pressure
• Blood pressure is the pressure exerted by the blood on the wall of blood vessel in which it is present.
• The blood pressure varies according to the contraction and relaxation of the heart.
• In the condition of contraction or systolic phase (Lubb sound) it is about 120 mm of Hg. This is called
“systolic pressure”.
• In the relaxation or diastolic phase (Dub sound) it is about 80 mm of Hg and is called “diastolic pressure”.
• The normal blood pressure of man (20 years) is 120/80 mm of Hg.
• The blood pressure is measured by “sphygmomanometer”.

26 Life Processes
 Brachial artery
(arm artery)
Sphygmomanometer

Cuff
Pressure of
inflated cuff Intermittent
blood flow
Free
Brachial blood
artery closed : flow
No blood
flow

Stethoscope

(a) No sound heard in (b) When tapping sound (b) when tapping sound
stethoscope : cuff pressure is first heard : cuff pressure just disappears cuff pressure
greater than systolic pressure is equal to systolic pressure is equal to diastole pressure

• Pulse : Every time the heart beats, blood is forced into arteries. This blood makes the arteries expand a
little. On expansion of an artery each time the blood is forced into it, is called pulse.
• The “electrocardiograph” (E.C.G.) is the device to record these electrical changes.

2. Lymphatic system
A system of tiny tubes called lymph vessels (or lymphatics) and lymph nodes (or lymph glands) in the human
body which transports the liquid called lymph from the body tissues to the blood circulatory system is called
lymphatic system. The lymphatic system consists of the following parts.
(i) Lymph capillaries
(ii) Larger lymph vessels
(iii) Lymph nodes (or Lymph glands)
(iv) Lymph.
Functions of lymph
• t provides immunity through lymphocytes by producing antibodies.
• Fats are absorbed through lymph vessels (lacteals) in the intestine.
• t supplies digested food and oxygen to various parts of the body.
• t helps in removal of waste products like fragments of dead cells,etc.
• t returns proteins and excess tissue fluid to the blood from the tissue spaces.

Life Processes 27
 EXCRETION
There are various metabolic activities which take place inside the living organisms. All these activities are chemical
reactions. As a result in animal body several end products are formed which are of no use to the cells. These are
called as wastes. These must be removed from the body for proper functioning of the body. The elimination of these
waste nitrogenous products from the body is called as excretion.

To maintain a healthy body, two important homeostatic process occurs in living organisms which help to maitain the
steady state. They are :

1. Excretion : Excretion is a biological process by which an organism gets rid of excess or toxic waste
products of metabolism. If allowed to accumulate, these products of organism’s cells would
generally be harmful and prevent the maintenance of a steady state.
Blood transports urea to the kidneys for filtration and removal in the form of urine.

2. Osmoregulation : It is a process that maintains the amount of water and proper ionic balance in the
body fluids. It maintains a constant osmotic condition in the body by regulating the water content and solute
concentration of body fluids, particularly of sodium, potassium and chloride ions.
On the basis of principal nitrogenous waste product excreted from the body of animals can be divided into three
categories.

Table : Different categories of animals based on type of nitrogenous waste

Product
S.No. Category Solubility in water Examples
formed

Ammonia Highly soluble, therefore needs Aquatic animals. Eg. Fishes,

1 Ammonotelic
(highly toxic) plenty of water for its excretion amoeba, tadpoles of frog.

Urea Less soluble thus needs less Mammals like cow, man etc,
2 Ureotelic
(less toxic) water for excretion. amphibians like toad and frog

Insoluble solids or semi-solid.

Uric acid
3 Uricotelic Need very little water for Insects, reptiles and birds
(least toxic)
excretion

EXCRETION IN HUMAN BEING

As a result of various metabolic process going on in our body a number of waste products are formed. These have to
be eliminated as they are toxic to the body.
The waste products include
• Carbon dioxide which is liberated during respiration and is eliminated by the lungs.
• Nitrogenous metabolic wastes, such as urea and uric acid produced in the liver from excessive proteins.
• Bile pigments : Bile pigments (e.g., billrubin) derived by the breaking down of haemoglobin of the erythrocyte.
• Excess salts, water and vitamins : Concentration of these substance above the required level, is harmful to the
body. Elimination of all metabolic nitrogenous wastes from the body is called as excretion.

1. Types of excretory organs in human beings

Excretory organs in humans can be divided into two categories
(i) Primary or major excretory organs
• In humans primary excretory organ is kidney
• They eliminate the principal metabolic waste, namely, nitrogenous materials
(ii) Accessory or additional excretory organs
• Some other organs such as skin, liver, lungs also remove certain metabolic wastes besides their normal
functions, they form accesory or additional excretory organs.

28 Life Processes
2. Human excretory system
The human excretory system comprises of
(i) Kidneys
(ii) Ureters
(iii) Urinary bladder
(iv) Urethra

Adrenal gland Renal vein

Right kidney left kidney

Renal artery
Vena cava
Ureter Dorsal aorta

Urinary bladder

Urethral sphincter
Urethra

Human excretory system

(i) Kidneys : Kidneys are bean shaped organs.
• Location : Located on either side of the vertebral column in the lower abdominal cavity.
• Each kidney is surrounded and covered by a tough, fibrous, capsule of connective tissue.
• This capsule is called renal capsule.

Functions of kidneys
- Excretion of waste products
- Maintain the water/osmotic balance in the blood (osmoregulation).
- Maintain pH by regulating concentration of H+ ions.
- Regulation of blood pressure by controlling the fluid content.
(ii) Ureters : A pair of ureters are found in human body. Renal pelvis leads into ureters. Urine formed in the
kidney is brought to the urinary bladder by two hollow muscular tubes called ureters.
(iii) Urinary bladder : Urine formed in kidney is stored in urinary bladder which is a hollow muscular, inverted
pear shaped organ.
(iv) Urethra : A single urethra is present in human. From urinary bladder urine is passed outside via urethra
during urination (micturition).

3. Nephron
• Nephron is the functional unit of kidneys.
• A nephron consists of a twisted tubule, closed at one end, open at the other with a network of associated
blood vessels.
• Each kidney of human being has about one million nephrons.
• Each nephron is differentiated into four regions having different anatomical features and different physiological
roles.

Life Processes 29
 Structure of nephron
• The 4 regions of nephron are
(i) Bowman’s capsule
• It is a large double walled cup like structure.
• It contains a tuft of capillaries called glomerulus and the outer wall is continuous with the rest of the
nephron.
• The Bowman’s capsule and the glomerulus together constitute the renal corpuscle or malpighian body.
(ii) Proximal convoluted tubule (PCT)
• It starts from the back of Bowman’s capsule.
• It is highly convoluted.
(iii) Loop of henle
• It is a U shaped segment of the nephron.
• It consists of two straight parallel limbs i.e. a descending limb which is a continuation of the PCT and
enters into the renal medulla and an ascending limb which re-enters the renal cortex and joins the DCT.
(iv) Distal convoluted tubule (DCT)
• It is greatly twisted like the PCT.
• The terminal part is relatively short and this part of DCT is called the collecting tubule.
• The collecting tubule opens into the collecting duct.
• All the collecting ducts then open into pelvis which leads into ureter.
4. Physiology of excretion
• Kidney filter all of the blood that comes from the heart forming urine.
• The process of cleaning happens in the nephrons present in kidneys and is completed in three stages.
(i) Ultrafilteration
• The afferent arterioles bring blood into the Bowman’s capsule further branches into fine capillaries which
form a knot of capillaries called glomerular capillaries or glomerulus.
• Along with the plasma, organic and inorganic molecules of low molecular weight such as urea, glucose,
amino acids and salts also pass into the renal tubule.
• Plasma proteins and blood corpucles of the blood, remain in the glomerulus. The blood corpucles are
RBC, WBC and platelets.

30 Life Processes
 (ii) Selective reabsorption : During reabsorption, necessary substances in the filtrate are reabsorbed by renal
tubules which then travel back into the blood stream.

(iii) Tubular secretion

• The process of passage of unwanted substances out of the capillaries directly into the renal tubules is
called as tubular secretion.
• It occurs mostly in distal convoluted tubules.

5. Artificial kidney or haemodialysis

A machine that uses dialysis to remove impurities and waste products from the blood stream before returning the
blood to the patient’s body is called Haemodialyzer.

Haemodialysis
Kidneys are most vital organs for survival of the organisms. Though the kidneys remain active throughout the life.
Its efficiency gradually declines with normal ageing proces. The other causes of decline in the normal functioning
of kidneys are diseases such as kidney infection, injury or restricted blood flow to kidneys.
these abnormalities result in kidney damage and malfunctioning. A general term for decline in the performance of
kidney due to a disease is kidney failure.
There are two alternatives of kidney failure (i) A matching kidney from a healthy person may be transplanted, or
(ii) An ‘artificial kidney’ machine may be employed in order to get rid of metabolic wastes from the blood and to
maintain normal levels of water and mineral ions in body fluids. The artificial kidney functions on the same
principle as the normal kidney and the procedure is called haemodialysis. The blood is pumped out of the body
and made to flow into the dialysis machine. Heparin is added to the blood to prevent clotting. The blood circulates
slowly through the long cellulose tubes coiled in a tank filled with dialysing solution. The cellulose membrane
allows ions, very small molecules and water to diffuse through it. The blood corpuscles, platelets and protein
molecules are too large and do not pass through the membrane. Finally the clean blood is pumped back into
patient.

EXCRETION IN PLANTS
Plants do not produce nitrogenous wastes like urea and uric acid because extra amino acids and nucleotides are not
formed. They produce other types of waste products, called secondary metabolites, e.g., alkaloids, tannins, aro-
matic oils.
• Many plants this products are - Nitrogenous waste, organic acid, tannins, latex, resins, gums.

Mechanism of excretion in plant :-

Plants do not have any mechanism to collect, transport and throw out their waste products. They have adopted
varied strategies to protect their living cell from waste products.

Life Processes 31
 (i) Old leaves : Waste products are stored in older leaves which soon fall off.

(ii) Old xylem : Resins, gums, tannins and other waste products are deposited in the old xylem which soon
becomes non-functional e.g. Hard wood.

(iii) Bark : Bark consists of dead cells which is peeled off periodically. Tannins and other wastes are deposited
in the bark. Incidentally, tannins are raw material for dyes and inks.

(iv) Central vacuole : Most plant waste products are stored in central vacuole of their cells. They are unable to
influence the working of cytoplasm due to presence of a selectively permeable membrane called tonoplast.

(v) Root excretion : Some waste substances are actually excreted by the plants in the region of their roots.

(vi) Detoxification : The toxic oxalic acid is detoxified by formation of calcium oxalate which gets crystallized
into needles (raphides), prism (prismatic crystals), stars (sphaeraphides) and crystal sand. Excess of cal-
cium is also precipitated as calcium carbonate crystals, e.g. cystolith.

(vii)Salt glands : They excrete excess salts obtained from the habitat.

32 Life Processes
 SOLVED QUESTIONS

Q.1 Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Ans. As in multicellular organisms, all the cells are not in direct contact with environment, simple diffusion does
not meet the requirement of all the body cells.

Q.2 What criteria do we use to decide whether something is alive?

Ans. All the living organism must have movement at molecular levels along with respiration and other life process
like nutrition, respiration, transportation and excretion to be called alive. The basic criteria of life is any cell
having living protoplasm, bounded by a cell membrane and showing molecular movement in it.

Q.3 What are outside raw materials used for by an organism ?

Ans. Outside raw materials used for by an organism includes:
(a) Food, (b) Water, (c) Oxygen of air (d) Carbon dioxide (by plants for photosynthesis) (e) Sunlight (by
plants for photosynthesis) (f) Minerals

Q.4 What processes would you consider essential for maintaining life ?
Ans. All the life processes are essential for maintaining life for eg. (a) Nutrition,(b) Respiration, (c) Transporta-
tion, (d) Excretion

Q.5 What are difference between autotrophic and heterotrophic nutrition ?

Ans. Autotrophic Nutrition- The mode of nutrition in which an organism makes its own food from the simple
inorganic materials like carbon dioxide and water present in the surroundings with the help of sunlight and
chlorophyll. eg. All green plants, cyanobacteria.
Heterotrophic Nutrition- The mode of nutrition in which an organism cannot makes its own food from the
simple inorganic materials like carbon dioxide and water present in the surroundings and depends on other
organisms for food. eg. Fungi, animals, human beings etc.

Q.6 Where do plants get each of the raw materials required for photosynthesis?
Ans. The raw materials and their source for photosynthesis are as follows
S.No. Raw material Source
1. Carbon dioxide Atmospheric air
2. Sunlight Sun
3. Water Soil
4. Minerals Soil
5. Chlorophyll Chloroplast of green plants
Q.7 What is the role of the acids in our stomach ?
Ans. HCl plays following role in our stomach
(a) Make the medium acidic for action of enzyme pepsin.
(b) Kills the harmful bacteria present in food
(c) Prevents fermentation of food
(d) Helps in breaking down of complex molecules into simpler ones.
Q.8 What is the function of digestive enzymes ?
Ans. Digestive enzymes break-down the various complex components of food into simple and soluble compo-
nents so that they can be absorbed easily.

Q.9 How is small intestine deigned to absorb digested food?

Ans. The inner lining of small intestine has numerous finger-like projections called villi and microvilli which
increase the surface area for secretions and absorption. The villi are richly supplied with blood vessels
which transport the absorbed food to each and every cells of the body. Where, it is utilized to obtaining
energy and repair of old tissues

Life Processes 33
Q.10 What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen
for respiration?
Ans. The terrestrial organisms take oxygen from the air. In atmosphere the amount of oxygen is good enough,
about 21% of atmospheric air is oxygen. An aquatic organism like fish takes oxygen dissolved in water. The
amount of oxygen dissolved in water is very low. Water fully saturated with air contains only a fraction of the
amount of oxygen that would be present in the same volume of air.
Apart this, water is more dense than air. Therefore, aquatic animals spend more energy to respire than
terrestrial animals. As a result the rate of breathing in case of aquatic organisms are many times more than
the terrestrial once.
Q.11 What are different ways in which glucose is oxidized to provide energy in various organisms?
Ans. Refer breakdown of glucose by various pathways (page 18)

Q.12 How is oxygen and carbon dioxide transported in human beings ?

Ans. In human beings the oxygen and carbon dioxide are transported in the following manner
(i) Oxygen – It is transported from lungs to various tissues by haemoglobin (respiratory pigment) haemo-
globin has very high affinity with oxygen and forms oxyhaemoglobin with oxygen.
(ii) Carbon dioxide is more soluble in water than oxygen. Therefore most of the carbon dioxide produced
during respiration is transported in dissolved form in our body (as bicarbonte ions)

Q.13 How are fats digested in our bodies? Where does this process take place?
Ans. Digestion of fats takes place in small intestine. Fats entering in intestine are in the form of large globules.
Bile juice breaks down these large globules into smaller globules. Afterwards fat digesting enzyme lipase
present in pancreatic juice and intestinal juice converts it into fatty acids and glycerol

Q.14 What is the role of saliva in the digestion of food?

Ans. The saliva contains an enzyme called salivary amylase that breaks down starch. which is complex
molecule into maltose.

Q.15 What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Ans. The conditions necessary for autotrophic nutrition are
In autotrophic nutrition green plants make their food by the process of photosynthesis. The food is pre-
pared from simple inorganic raw materials.
The requirement for autotrophic nutrition are
(a) raw materials like carbon dioxide and water.
(b) green coloured pigment chlorphyll for trapping energy (present in chloroplast)
(c) source of energy : Sunlight
By product of photosynthesis is oxygen.

Q.16 What are differences between aerobic and anaerobic respiration? Name some organisms that use
anaerobic mode of respiration.
Ans. Refer table : Difference between Anaerobic and Aerobic Respiration

Q.17 How are the alveoli designed to maximize the exchange of gases?
Ans. The structural features of alveoli to maximise the exchange of gases are
(i) There are millions of alveoli in the lungs and they have vast surface area (If spreaded they cover about
802 m area). So they have very large surface area.
(ii) Their wall is just one cell thick to facilitate diffusion.
(iii) The alveoli are richly supplied with blood (they are covered by a network of blood capillaries)
(iv) They are kept moist and are permeable to gases.

Q.18 How are the lungs designed in human beings to maximize the area for exchange of gases?
Ans. In lungs, the bronchioles terminate in balloon-like structures called alveoli that increase the surface area.
The alveoli contains network of blood capillaries for exchange of gases.

34 Life Processes
Q.19 What are the components of the transport system in human beings? What are the functions of these
components?
Ans. In human beings there are two types of transport systems.
(A) Blood transport system
The components are
(i) Heart : To pump the blood
(ii) Blood vessels
(a) Arteries : Carry blood away from the heart.
(b) Veins : Carry blood towards the heart.
(c) Capillaries : Fine tubular structures for exchange of materials.
(iii) Blood : It has haemoglobin in RBCs for transportation of oxygen, plasma of it carries CO2, digested
food, excretory wastes and hormones etc. White blood corpucles fight against infection. Platelets
help in clotting of blood.
(B) Lymphatic system : The components are
(i) Lymph (ii) Lymph vessels
(iii) Lymphatic capillaries (iv) Lymph nodes
(v) Lymphatic organs (spleen and thymus)
Functions : Lymph returns leaked out blood plasma back to blood, helps in transport of absorbed
fats and fights against infection.

Q.20 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. The separation of the right and left side of heart is useful to prevent oxygenated blood and deoxygenated
blood from mixing. Such separation allows a highly efficient supply of oxygen to the body. This is useful in
animals that have high energy needs, such as birds and mammals that constantly use the energy to main-
tain their body temperature.

Q.21 What are the components of transport system in highly organized plants?
Ans. The transport system of higher plants consists of xylem and phloem. Xylems have (i) vessels (ii) trachieds
(iii) xylem parenchyma (iv) xylem sclerenchyma. Vessels and trachieds transport water and minerals from
root to other part of the plants. Phloem, which consists of sieve tubes and companion cells, along with
phloem parenchyma and phloem sclerenchyma transport food from leaves to storage organs and other parts
of the plant.

Q.22 How are water and minerals transported in plants?

Ans. Water and minerals are transported in plants through xylem which consists of trachieds and vessels. Water
and minerals absorbed by root hairs present in root by osmosis is passed to xylem tissues of root. along
with xylem parenchyma and xylem sclerenchyma. From root xylem it passes to stem xylem and thus water
reaches to leaves with the help of transpirational pull.

Q.23 How is food transported in plants?

Ans. Food is transported in plants through phloem which consists of sieve tubes, sieve cells and companion cells,
along with phloem parenchyma and phloem sclerenchyma. The food prepared in leaves in soluble form
transported to leaves phloem. Active transport of food passes to all other parts of plants by the process of
osmosis based on the difference of concentration gradient.

Q.24 What would be the consequence of a deficiency of haemoglobin in our bodies?

Ans. Haemoglobin is a pigment present in RBC. It has a high affinity for oxygen. It carries oxygen from lungs to
various tissues which are deficient in oxygen. Presence of less haemoglobin will result in less supply of
oxygen to tissues. A person having less haemoglobin will get tired soon, have a pale look, show
breathlessness and suffer from anaemia. The metabolism of the body is badly affected.

Life Processes 35
Q.25 Describe double circulation in human beings. Why is it necessary ?
Ans. In mammals and birds the blood goes through the heart twice during each cycle. This is known as double
circulation. Deoxygenated blood which enters right auricle and then it enters the right ventricle from where it
is pumped to lungs for oxygenation. From lungs after oxygenation it comes to left auricle and then enters left
ventricle from where it is pumped to various parts of body. Such system of circulation does not allow mixing
of oxygenated and deoxygenated blood which allows efficient supply of oxygen to the body. This is specially
required in organisms having high metabolic rate. Birds and mammals including human beings are warm
blodded animals. To keep their body temperature constant, their energy requirements are high. So, they
need double circulation.

Q.26 What are the differences between the transport of materials in Xylem and phloem?
Ans. Difference between transport by Xylem and Phloem.

Transport by xylem Transport by phloem

Inroganic substances like water and Organic food prepared in

1 1
minerals are transported photosynthesis is transported

Transport does not require energy (It

2 2 Energy is needed for transport of food.
takes place by simple physical forces)

It is unidirectional flow (only upward Movement is upward, downwards and

3 3
transportation) sideways.

Xylem is mainly formed of dead cells : Phloem is mainly made of living cells :
4 4
vessels and tracheids Sieve tube helped by companion cells.

Q.27 Describe the structure and functioning of nephron.

Ans. Each nephron is a cluster of very thinwalled blood capillaries. Each capillary cluster in the kidney called
glomerulus is associated with the cup shaped Bowman’s capsule that collects the filtered urine. Nephron
filters the blood in order to remove nitrogenous waste. They also absorb some useful substance such as
glucose, amino acids, minerals and major amount of water from filtrate.

Q.28 What are the methods used by plants to get rid of excretory products?
Ans. (i) Plant produces carbon dioxide as wastes during respiration and oxygen as waste during photosynthesis.
(ii) Excess of water is removed through transpiration.
(iii) Some waste products like gums and resins are stored in older xylem tissue.

Q.29 How is amount of urine produced regulated ?

Ans. About 180 litres of fluid is collected in human nephrons daily after filtration. But most of this water is re-
absorbed by the tubule.
The amount of urine produced is regulated by the process of re-absorption. If input of water is more then,
there is less re-absorption of water. When water is to be conserved in the body, reabsorption increases. This
is called osmoregulation.

36 Life Processes
Q.30 Compare the functioning of alveoli in the lungs and nephrons in the kidney with respect to their structure and
functioning.
Ans. Differene between alveoli and nephrons are as follows

Alve oli Ne phrons

Shape like bunc hes of grapes . Individual Nephron is a tube lik e struc ture with a cup
1 1
alveolus is a sac or balloon lik e s truc ture. s haped m outh.

2 W all : Thin walled, just one cell thic k 2 Thin walled, tube is just one c ell thick
Blood s upply : Highly vas cular, ric hly
3 3 Surrounded by capillaries.
supplied by blood c apillaries
Due to long tubes of m illions of nephron large
4 Surface area : Provide large surface area 4
s urfac e area.
5 Perm eability : Perm eable to gases 5 Perm eable to water and s m all solutes

Ex change of gases by diffus ion to get Filtration of blood and selec tive reabsorption of
6 6
ox ygen and relase out carbon diox ide filtrate to produce urine

Life Processes 37
 EXERCISE - I
Q.1 The dark reaction in photosynthesis is called so because it
(A) cannot accur during day time (B) is light dependent
(C) is light independent (D) Occurs rapidly at night
Q.2 For the process of photosynthesis all except one of the following items are essential. Point out the exception
(A) CO2, optimum temperature (B) Glucose and oxygen
(C) Water and minerals (D) Light and chlorophyll
Q.3 Ribbon shaped chloroplast is present in
(A) zygnema (B) algae (C) bacteria (D) fungi
Q.4 The oxygen molecule in glucose formed during photosynthesis comes from
(A) water (B) organic acids (C) CO2 (D) atmosphere
Q.5 The visible product of photosynthesis is ______.
(A) glucose (B) cellulose (C) starch (D) fructose
Q.6 Which one of the following is not a part of the large intestine?
(A) Rectum (B) Colon (C) Caecum (D) Duodenum
Q.7 Dental formula of an adult man is
2123 2123 2123 2132
(A) (B) (C) (D)
2123 2122 2124 2132
Q.8 The cells of the epithelial lining in the vertebrate stomach are not damaged by HCl because of
(A) mucus secretion covering the epithelium (B) neutrilizatioin of HCl by alkaline gastric juice.
(C) HCl being too dilute (D) epithelium being resistant to HCl
Q.9 The structure which prevents entry of food into wind pipe during swallowing in mammals is
(A) larynx (B) glottis (C) epiglottis (D) pharynx
Q.10 Which of the following is a common passage in swallowing food and breathing?
(A) Pharynx (B) Larynx (C) Glottis (D) Gullet
Q.11 Ptyalin is secreted by
(A) stomach (B) salivary gland (C) pancreas (D) bile
Q.12 Bilirubin and bilivirdin are found in
(A) blood (B) bile (C) saliva (D) none of these.
Q.13 Larynx is a modified portion of
(A) pharynx (B) trachea (C) bronchioles (D) lungs
Q.14 Exchange of gases in man takes place in
(A) trachea (B) bronchus (C) alveoli (D) all
Q.15 In fever breathing rate
(A) increases (B) decreases (C) stop (D) none
Q.16 During inspiration, the pressure of air is maximun in
(A) trachea (B) bronchi (C) alveoli (D) environment
Q.17 Match the columns
Column-I Column-II
(a) Larynx (p) Lid of larynx
(b) Trachea (q) Air sacs
(c) Alveoli (r) Voice box
(d) Epiglottis (s) Wind pipe
(t) Common passage.
(A) a—r, b—s, c—q, d—p (B) a—t, b—s, c—p, d—q
(C) a—r, b—s, c—q. d—t (D) a—r, b—t, c—q, d—p
Q.18 In which of the following animals, respiration occurs without respiratory organ ?
(A) Frog (B) Fish (C) Cockroach (D) Earthworm
Q.19 Rate of respiration is directly affected by
(A) CO2 concentration (B) O2 in trachea
(C) concentration of O2 (D) diaphragm expansion

38 Life Processes
Q.20 When CO2 concentration in blood increases, breathing becomes
(A) slow and deep (B) faster and deeper
(C) shallower and slow (D) there is no effect on breathing
Q.21 Residual air mostly occurs in
(A) alveoli (B) bronchus (C) nostrils (D) trachea
Q.22 The combination of oxygen with haemoglobin is called
(A) oxidation (B) oxygenation (C) reduction (D) none of the above
Q.23 A portion of cardiovascular system that transports oxygen depleted blood from the heart to lungs and brings
oxygenated blood back to heart is
(A) pulmonary circulation (B) coronary circulation
(C) systemic circulation (D) single circulation system
Q.24 A respiratory pigment is absent in
(A) bird (B) frog (C) rabbit (D) cockroach
Q.25 A young man of 25 years has his blood pressure
(A) 130/90 mm Hg (B) 120/80 mm Hg (C) 120/90 mm Hg (D) 130/80 mm Hg
Q.26 All veins have deoxygenated blood except
(A) renal artery (B) hepatic vein (C) hepatic portal vein (D) pulmonary veins
Q.27 Blood passes from left ventricle to right atrium. It is
(A) pulmonary circulation (B) systemic circulation
(C) coronary circulation (D) arteriovenous Circulation
Q.28 Blood pressure is measured by
(A) electro - cardiogram (B) stethoscope
(C) sphygmomanometer (D) barometer
Q.29 Mammalian heart is enclosed by
(A) perichondrium (B) periosteum (C) no membrane (D) pericardium
Q.30 SA node is located
(A) upper lateral wall of left atrium (B) lower lateral wall of left atrium
(C) upper lateral wall of right atrium (D) lower lateral wall of right atrium
Q.31 The role of pacemaker in heart is to
(A) initiate heart beat (B) control blood pressure
(C) control atherosclerosis (D) purify blood
Q.32 Thromboplastin required for blood clotting at the place of injury is released by
(A) blood platelets (B) eosinophils (C) neutrophils (D) lymphocytes
Q.33 Glomerular capsule and Convoluted tubules always lie within the _______.
(A) renal pelvis (B) renal medulla (C) renal cortex (D) none of these
Q.34 The basic functional unit of human kidney is
(A) henle's loop (B) nephron (C) nephridia (D) pyramid
Q.35 The lungs are important organs for excretion of
(A) ammonia (B) water (C) carbon dioxide (D) urea
Q.36 The muscular tubes which take the urine from the kidneys to the bladder are
(A) urinary bladders (B) ureters (C) urethras (D) nephrons
Q.37 The kidneys resemble the contractile vacuoles of amoeba in
(A) expelling out excess of water (B) expelling out glucose
(C) expelling out urea and uric acid (D) expelling out salts
Q.38 In the kidneys of mammals, Loop of Henle can be found in
(A) medulla (B) cortex (C) pelvis (D) pyramid
Q.39 Excretion of bile pigments in urine indicates
(A) anaemia (B) diabetes (C) gout (D) jaundice
Q.40 Workers in deep mines usually suffer from dehydration because
(A) water is lost due to evaporation (B) water is lost due to defecation
(C) water is lost in the form of sweat (D) water is lost along with salts in the form of sweat

Life Processes 39
 EXERCISE-II
Q.1 Name the different modes of nutrition and classify them with one example of each ?
Q.2 Give the importance of bile juice during digestion process, also write from where it is secreted , what is its
site of action ?
Q.3 How does exchange of gases takes place in the following?
(i) Roots (ii) Stem (iii) Leaves
Q.4 Name the respiratory organs in the following.
(i) A fish (ii) A bird (iii) An earthworm
Q.5 Why AB+ blood group is considered as universal recipient ?
Q.6 What is double circulation ?
Q.7 Name the excretory unit of Amoeba.
Q.8 Name the major excretory product of human beings.
Q.9 What is the importance of the following process occurring during photosynthesis in plants?
(i) Emission of electrons from chlorophyll
(ii) Photolysis of water
Q.10 Describe the digestion process of carbohydrate in humans
Q.11 What happens to the rate of breathing during vigorous exercise and why ?
Q.12 Why do walls of trachea not collapse when there is less air in it ?
Q.13 Distinguish between transpiration and translocation.
Q.14 Distinguish between arteries and veins.
Q.15 What is meant by excretion and osmoregulation ?
Q.16 How excretion takes place in Amoeba ?
Q.17 Describe the mechanism of photosynthesis ?
Q.18 How are oxygen and carbon dioxide transported in human beings ? How are lungs designed to maximise the
area for exchange of gases ?
Q.19 (a) Draw a sectional view of the human heart and label on it Aorta, Pulmonary arteries, Vena cava, Left
ventricle.
(b) Why is double circulation of blood necessary in human beings ?
Q.20 (a) Draw the structure of a nephron and label the following on it : Glomerulus, Bowman's capsule, Renal
artery, Collecting duct.
(b) What happens to glucose that enters the nephron along with filtrate ?

ANSWER KEY
EXERCISE - I

Que. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Ans. C B B A C D A A C A B B B C A
Que. 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Ans. D A D A B A B A D B D B C D C
Que. 31 32 33 34 35 36 37 38 39 40
Ans. A A C B C B A A D D

40 Life Processes