Life Processes Class 10 Notes Biology

Science Chapter 6
Introduction
What is living ?

‘Living’ is something that is alive, something that can grow, move,

reproduce, respire, made up of cells and are capable of carrying out
various cellular activities.

Biology is the study of life and all living organism that have the
potential to carry out the basic process which may be called as the
characteristics of life or life processes.

Some Of The Life Processes In The Living Beings Are

Described Below:
Nutrition: The process of obtaining energy through consumption of
food is called as nutrition.

Respiration: The process of acquiring oxygen through breathing and

make it available to cells for the process of breaking down of organic
substances into simpler compounds is called as respiration.

Transportation: Transportation is the process by which the food and

oxygen is carried from one organ to other organs in the body.

Excretion: It is the process by which the metabolic waste by-products

are removed from the different organs and released out from the body

In unicellular organisms, all these processes are carried out by a single

cell.

In multicellular organisms, well-developed systems are present to carry

out the processes.

Nutrition
“Nutrition is the process of taking in food and converting it
into energy and other vital nutrients required for life.”
What Is The Need Of Nutrition ?

 Organisms need energy to perform various activities. The
energy is supplied by the nutrients.
 Organisms need various raw materials for growth and
repair. These raw materials are provided by nutrients.
What Are Nutrients ?

 Materials which provide nutrition to organisms are called
nutrients.
 Carbohydrates, proteins and fats are the main nutrients and
are called macronutrients.
 Minerals and vitamins are required in small amounts and
hence are called micronutrients.

Types Of Nutrition:

Autotrophic Nutrition:
 The mode of nutrition through which an organism prepares its
own food is called autotrophic nutrition.
 Green plants and blue-green algae follow the autotrophic mode of
nutrition. These organisms are called photosynthetic because
they process raw materials in presence of sunlight to make food.
 Some organisms process certain raw materials through chemical
reactions, without utilising the sunlight. Such organisms are
chemosynthetic.
Heterotrophic Nutrition:
 The mode of nutrition through which an organism takes food from
another organism is called heterotrophic nutrition.
 Organisms, other than autotrophs, follow heterotrophic mode of
nutrition. These organisms directly or indirectly depend on
autotrophs for food.
 For example, almost all the animals directly or indirectly take
food from plants. Animals which eat plants are called herbivores,
while flesh-eating animals are called carnivores.
  Heterotrophic nutrition can be further divided into three types,
viz. saprophytic nutrition , holozoic nutrition and parasitic
nutrition.

Saprophytic Nutrition: In saprophytic nutrition, the organism

secretes digestive juices on food. The food is digested while it is still to
be ingested.

Digestion involves converting complex molecules into simple

molecules so that they can be utilised by the organism. The digested
food is then ingested by the organism.

All the decomposers follow saprophytic nutrition. Saprotrophs feed on

dead remains of different organisms. By doing so, they help in
decomposition of organic waste. This is an important process during
various biogeochemical cycles.

Many bacteria and all the fungi follow saprotrophic mode of nutrition.

Parasitic Nutrition : Organisms that lives in or on other organisms

and also acquire food of its host are known as parasites.

Most parasites are harmful to the hosts health and sometimes, they
even kill the host. Both animals and plants may serve as a host. Unlike
commensalism, the parasite causes some harm to its host. A few
examples of parasites are louse on a human head, Cuscuta plant.

Holozoic Nutrition: In holozoic nutrition, the digestion happens inside

the body of the organism, i.e. after the food is ingested. Animals and
protozoa follow this mode of nutrition.

Nutrition in plants
Photosynthesis:
Green plants are capable of manufacturing their own food in the form
of carbohydrate in presence of light by using water and carbon-dioxide,
this process is called photosynthesis.

Such mode of nutrition is termed as autotrophic nutrition.

Carbohydrates provide energy to the plant and the ones not used are
stored in the form of starch. Starch is the reserve food of plants
whereas reserve food in case of animals in glycogen.
Photosynthesis is the process by which green parts of the plant
synthesize organic food in the form of carbohydrates from CO 2 and
water in the presence of sunlight.

6CO2+6H2O→ChlorophyIILight�6�12�6+6�2(�����
��)6CO2+6H2OLightChlorophyII(Glucose)C6H12H6+6O2
Mechanism Of Photosynthesis

 Light reaction – Thylakoids of Grana
 Dark reaction – Stroma

Events Occurring During Photosynthesis


 Absorption of light energy by chlorophyll.
 Conversion of light energy to chemical energy and splitting
of water molecules into hydrogen and oxygen.
 Reduction of CO2 into carbohydrate.

Steps Of Photosynthesis :
During the process of photosynthesis, the following events occur :


 Absorption of light energy by chlorophyll.
 Conversion of light energy to chemical energy and splitting
of water molecules into hydrogen and oxygen.
H2O→2H++2e−+12O2H2O2H++2e−+21O2
The above processes are considered as light reaction as it can take
place only in the presence of light.


 Reduction of carbon-dioxide to carbohydrates. This is also
known as dark reaction as it does not require light.
Desert plants take up CO2 at night and prepare an intermediate which
is acted upon by the energy absorbed by the chlorophyll during the
day.

Conditions Necessary For Photosynthesis

 
 Sunlight
 Chlorophyll
 Carbon-dioxide
 Water
These conditions are needed for autotrophic mode of nutrition.

Site of Photosynthesis: Leaf in the organ where maximum

photosynthesis takes place. If you see the cross section of a leaf you
will find some green dots. These green dots are cell organelles called
chloroplasts which contain chlorophyll.

Chlorophyll containing organelles (chloroplasts) are found in large

numbers in plant and algal cells.
Raw Materials For Photosynthesis
1. Carbon dioxide: It is a gas, which is released into the
atmosphere during respiration by all living organisms. This gas is
utilized by autotrophic plants which enters the leaf through the
stomata present on its surface during the process of
photosynthesis.
2. Water: It is another requirement for photosynthesis which is
transported upward through xylem tissues to the leaves, from
where it reaches the photosynthetic cells. Elements such as N, P,
Fe and Mg are required by the plant to build their body is taken
up from the soil along with water by roots. Nitrogen is the most
important constituent of amino acid and nitrogenous bases. This
is taken up in the form of inorganic nitrates or nitrites. It can also
be taken as organic compounds which have been prepared by
bacteria from atmospheric nitrogen.
3. Chlorophyll: It is a green pigment in plants which act as a
catalyst. It is responsible for absorption of sun’s energy. The
chlorophyll pigments are photoreceptor molecules which play a
key role in the photosynthetic process. The different types of
chlorophyll molecules are chlorophyll a, b, c, d and
bacteriochlorophyll; of which chlorophyll a and b are most
common.
4. Light: It affects the rate of photosynthesis by its intensity,
quality and duration. In green light, the rate of photosynthesis is
 minimum, while in red and blue lights the rate of photosynthesis
is maximum. Rate of photosynthesis is higher in plants getting
average light of 10-12 hrs a day.
5. Gaseous exchange during photosynthesis : Stoma are tiny
pores present on the surfaces of the leaves (more on the lower
surface and less on the upper surface). Stomata function in gas
exchange between the plant and the atmosphere during
photosynthesis. Each stoma is bordered by two bean / dumbbell
shaped guard cells in dicots and monocots respectively. However
exchange of gases also occurs across the surface of stems, roots
etc.

Opening and Closing of Stomatal Pore : The opening and closing

of the stomata is the function of 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. Since large amounts
of water can also be lost through stomata the plant closes these pores
when it does not need CO2 for photosynthesis.

External Factors Affecting Photosynthesis


 There are number of factors which affect the process of
photosynthesis thereby affecting the productivity of a
plants.
 Each factor has three principal values i.e., minimum,
optimum and maximum. Optimum means the process is
taking place at its highest rate.
  Maximum value means beyond which the process is
adversely affected.
Important External Factors Are :

 Light
 Temperature
 Water
 Carbon dioxide
Light

 In photosynthesis light is converted into chemical energy in
the form of food.
 The rate of photosynthesis is affected by quality, intensity
and duration of light.
 The chlorophyll absorbs mostly the blue and red regions of
the spectrum.
 The green light has inhibitory effect. The low intensities of
light increase the rate of photosynthesis while the higher
intensities retard the rate of photosynthesis.
 Plants getting average light of 10-13 hours a day exhibit
higher rate of photosynthesis.
Temperature

 Temperature acts as a limiting factor under field conditions
particularly on cool days.
 The influence of temperature on photosynthesis depends on
both light intensity and availability of CO2.
 An increase in temperature above 30oC results in a fall in
the rate of photosynthesis. Changes in temperature do not
affect the light reactions of photosynthesis but markedly
influence the rate of enzyme-mediated dark reactions.
 However, the effect of temperature on the rate of
photosynthesis varies from plant to plant.
Water

 Water deficiency may retard the rate of photosynthesis as it
is one of the raw materials for the process.
  Under water deficient conditions stomata remain closed to
reduce the transpiration thereby affecting the entry of CO 2.
Carbon dioxide

 Carbon dioxide is present in low concentration and forms
about 0.032% of the atmosphere. It enters the leaves
through stomata.
 The rate of photosynthesis increases with an increase in
CO2 concentration up to a certain limit. Higher concentration
of CO2 may prove toxic to plants.

Internal Factors Affecting Photosynthesis

Chlorophyll
Photosynthesis does not occur in etiolated and chlorophyll less leaves.
In the variegated leaves, photosynthesis occurs only at the places
which possess chlorophyll.

Anatomy of leaf
The amount of CO2 that reaches the chloroplast depends on structural
features of the leaves like the size, position and behaviour of the
stomata and the amount of intercellular spaces Some other characters
like thickness of cuticle, epidermis, presence of epidermal hairs,
amount of mesophyll tissue, etc., influence the intensity and quality of
light reaching into the chloroplast.

Nutrition In Human Beings

Human beings are heterotrophic omnivorous organisms. They obtain
their food from plants, animals and their products by holozoic modes of
nutrition.
 Ingestion: Process of taking food inside the body through
mouth.
 Digestion: Process of conversion of complex food particles
into simpler ones by the action of enzymes.
 Absorption: Process of diffusion of soluble food particles
into the blood.

  Assimilation: Process of utilization of absorbed food by the
body cells.
 Egestion: Process of removal of undigested food from the
body.

Human Digestive System


 The organs which are responsible for ingestion, digestion,
absorption, assimilation and egestion constitute the
digestive system.
 The digestive system comprise the alimentary canal and
associated digestive glands.
  It consists of mouth, buccal cavity, oesophagus, stomach,
small intestine, large intestine, rectum and anus.
 Digestive glands are salivary glands, liver and pancreas.

Alimentary Canal
Alimentary canal in man is 9 meters long and consists of the following
parts :

Mouth:

 It leads into buccal cavity. Palate forms the roof of the
buccal cavity and is differentiated into anterior hard and
posterior soft palate.
 The floor of the buccal cavity has a tongue bearing taste
buds. Mucous membrane of the tongue contains taste buds
which contain receptors sensitive to sweet, salty, bitter and
sour taste.
Teeth:

Types of teeth Function Number of teeth

Incisors Used for biting 4

Canines Used for tearing 2

Premolars Used for grinding 4

Molars Used for grinding 6

There are 32 teeth of four different types, in human adult. These are:
Pharynx:

 It is a short, conical region that lies after the mouth cavity
and connects it to the esophagus.
Oesophagus:

 It is a long, narrow, muscular tube which leads to the
stomach. No digestive glands are present in the
oesophagus. It conveys the food (bolus) to stomach through
peristalsis.
 Peristalsis is a series of wave of contraction of muscles that
passes from one end to the other. This pushes the food
forward.
Stomach:

 It lies below the diaphragm on the left side of abdominal
cavity and is J-shaped.
 It is divisible into cardiac and pyloric part. The food is stored
and partially digested in the stomach.

Small Intestine:

 From the stomach the food is moved to the small intestine.
It is a very long tube (7 mt. long and 2.5 cm. diameter)
which originates from the distal end of the stomach and
extends to the large intestine.
  The small intestine is the longest part of the alimentary
canal and is greatly coiled and twisted. The small intestine
is subdivided into three sections: the duodenum, the
jejunum, and the ileum.
Duodenum:

 The duodenum (about 10 inches ) part of the small intestine
is the main seat of digestion in the gut. The acidic chyme in
the duodenum receives the bile secreted from the liver, the
pancreatic juice secreted from the pancreas and the
intestinal juice from the glands of the intestinal wall.
 Bile is a yellowish-green in colour, bitter in taste, slightly
alkaline fluid secreted from the liver.
 Bile being alkaline in nature neutralises the acidic chyme.
Bile emulsify fat into microscopic droplets and thus helps in
the digestion and absorption of fat. So bile is called
digestive juice though it does not contain enzyme.
 Again the pancreas, a large gland located below the
stomach, secretes pancreatic juice into the duodenum
through the pancreatic duct. There are three enzymes
namely amylase, pancreatic lipase and trypsin, in
pancreatic juice that break down carbohydrates, fats, and
proteins respectively.
 Glands of intestine are present in the mucous layer of the
intestinal wall. These glands secrete intestinal juice, which
contains various enzymes.
 The enzymes present in it finally convert the carbohydrates
into glucose, proteins to amino acids and fats into fatty
acids and glycerol.
Jejunum:

 The jejunum is about 8.2 feet (2.5 meters) long. The
digested carbohydrates, fats, proteins, and most of the
vitamins, minerals, and iron are absorbed in this section.
 The inner lining of the small intestine is composed of up to
five million tiny, fingerlike projections called villi. The villi
increase the rate of absorption of nutrients into the
bloodstream by greatly increasing the surface area of the
small intestine.
Ileum:
 
 The ileum, the last section of the small intestine, is the
longest, measuring 11 feet (3.4 meters). Certain vitamins
and other nutrients are absorbed here
Large Intestine

 It has three parts – caecum, colon and rectum.
 Large intestine absorbs water and electrolytes.

Digestive Glands

Salivary Glands

 The salivary glands secrete the first of the digestive juices,
the saliva.
 There are three pairs of salivary glands, namely the
parotids, sub-maxillary and sublingual glands.

Gastric Glands:

 They are branched tubular glands which lie in the mucus
membranes of the stomach.
 They secrete gastric juice, which is acidic, containing HCl,
enzymes and mucus.
Liver:

 It is the largest gland in man and lies below diaphragm in
the right upper part of abdomen.
 Liver comprises of two lobes, right and left, the right lobe is
much larger than the left lobe.
 The cells of liver, i.e., hepatic cells, produce bile juice, which
is stored in the gall bladder via cystic ducts.
Bile juice flows out of liver through hepatic ducts forming common bile
duct and opens into the duodenum.
Pancreas:

 It is a soft lobulated gland present in between the loops of
duodenum.
 It secretes pancreatic juice containing enzymes which is
poured into duodenum with the help of pancreatic duct.

What Are Life Processes ?

 Living beings are complex organisations of molecules which perform various life
processes like growth, respiration, digestion, reproduction, excretion etc., which
makes them different from non-living.
 The basic processes or functions performed by living organisms to keep them
alive are called life processes.

Nutrition is defined as the process of intake of nutrients and its

utilisation by an organism in various biological activities.
 In autotrophic mode of nutrition, organisms prepare their own food and they are
called autotrophs. Organisms prepare food by the process of photosynthesis.
 Photosynthesis is the process by which chlorophyll containing cells prepare
glucose using carbon dioxide and water in presence of light energy and oxygen
gas is released as a by product during this process.
 6CO2 + 12H2O Sunlight/Chlorophyll C6H12O6 + 6O2 + 6H2O [Equation for
photosynthesis]

Steps of nutrition in human beings

Organs of the digestive system

Nutrition in amoeba