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1. Nutrition in Animal
Plants make their food by the process of photosynthesis, but animals cannot make
their food themselves. Animals get their food from plants. Some animals eat plants
directly while some animals eat plant eating animals. Thus, animals get their food
from plants either directly or indirectly.
All organisms require food for survival and growth. Requirement of nutrients, mode
of intake of food and its utilization in body are collectively known as nutrition.
Nutrition in complex animals involves following steps:
 Ingestion
 Digestion.
 Absorption.
 Assimilation
 Egestion.
Ingestion- The intake of food is called ingestion. Method of ingestion, i.e. taking of
food, varies from one animal to another.
Digestion - The process of breaking down of complex component of food into
simpler substances is called digestion.
The process of digestion is different in human, grass eating animals, amoeba, etc.
Absorption – The process of passing of digested food into blood vessels in the
intestine is called the absorption.
Assimilation – The conversion of absorbed food in complex substances such as
proteins and vitamins required by body is called assimilation.
In other words, assimilation is the conversion of absorbed food (nutrients) into living
tissues. Through the process of assimilation our cells are supplied with oxygen and
nutrients.
Egestion – Removal of waste materials from the body is called egestion. The faecal
matter is removed through the anus from time-to-time.
Since the waste of food left after digestion is also called faeces, hence the process
of egestion is also known as defecation.
Different Ways of Tajubg Food: Ingestion
Different organism takes food in different ways.
 A humming bird sucks nectar of plants.
 Human beings use their hands to put food into their mouth and swallow the food after
chewing.

2.  Infants of human and many other animals feed upon their mother’s milk by sucking
them.
 A snake swallows the animals they prey upon without chewing them.
 A frog captures prey with its sticky tongue.
 An earthworm uses its muscular pharynx to swallow its food.
 Spiders weave sticky web in which small insects get stuck.
 Some aquatic animals filter tiny particles floating nearby and feed upon them.
 Amoeba, a unicellular animal, engulfs tiny particles of food by using pseudopodia.
Amoeba surrounds the food by pseudopodia and then makes a food vacuole to
engulf the food.
 In multicellular organisms; like hydra there are numerous tentacles around their
mouth. Hydra uses tentacles to surround its prey and kill them with its stinging cells.
Then the food is pushed inside the body cavity.
Digestion
After taking of food, food is digested and then it is passed to the different parts of
body for the growth, repair and other vital functioning of body.
The food we take is primarily in the form of complex substances. Food in such
complex form is not used as such by animals. Hence, they need to be first broken
down into simpler soluble forms so that they can be absorbed by the cells of the
body.
The process of breaking down of complex component of food into simpler
substances is called digestion. The process of digestion is different in human, grass
eating animals, amoeba, hydra, etc.
Enzymes help in the breakdown of complex molecules like carbohydrates, protein,
fats, etc. into simple molecules.
Digestion in unicellular animals; like Amoeba; is intracellular. The digestive enzymes
are secreted in the food vacuoles.
Digestion in Grass Eating Animals –
Ruminants: None of the animal can digest cellulose which is a major component of
the food eaten by herbivores. The plant eating animals digest their food in two steps.
Their stomach is divided into four chamber the rumen, reticulum, omasum and
abomasum.
First of all, half chewed food is swallowed and it then goes from mouth to the rumen,
the first chamber of the stomach. Here, it is acted upon by bacteria. These
microorganisms digest the cellulose. This half digested food goes to the second
muscular chamber; the reticulum. From the reticulum the food is sent back to the
mouth; as cud; to be chewed again. Chewing of the cud is called rumination and
such animals are called ruminating animals or ruminants. Cow, goat, buffaloes,
sheep, bison, etc. are good example of ruminating animals. The re-chewed food is
swallowed for the second time. After passing the first two chambers it enters the third

3. chamber; the omasum. Here the food is further broken down into smaller pieces and
finally enters the fourth chamber, the abomasum. Here, all enzymes act upon the
food and the digestion is completed.
After digestion and absorption, nutrients from food are taken to the cells in all parts
of the body. The cells oxidize the food to release energy.
Transportationinanimal
Circulatory system
The system which pumps the fluid tissue to transport it throughout the body is called the circulatory
system. Human circulatory system comprises of heart, blood and a network of blood vessels. The
system transports oxygenated blood from lungs and the heart throughout the body via arteries. The
oxygenated blood is supplied to all the organs by arteries branching out as capillaries. The
deoxygenated blood is returned to veins through capillaries. These veins carry deoxygenated blood to
the heart and the lungs.
Human heart
The heart is the central organ for pumping the blood throughout the body. Heart is made up of strong
cardiac muscles. It is located in the chest cavity with its lower part pointing towards the left. Its size is
that of the person’s fist. It pumps blood rich in carbon dioxide to the lungs and oxygen-rich blood to
other parts of the body.
 The heart consists of four chambers namely auricles and ventricles. The two upper chambers of
the heart are known as the auricles.
 Heart has number of valves which allow the blood to flow in one direction. These prevent the
oxygenated blood mixing with de-oxygenated blood.
 SA node, the natural and primary pace maker of the heart is located in the upper wall of the right
atrium in the heart.
 AV node, the secondary pace maker is located in the bundles of tissues on the border between
right atrium and right ventricle of the heart.
Types of circulation
The two types of circulation are single circulation and double circulation.
 Single circulation is the type of circulation in which blood passes through the heart only once
through the heart. For example, it is seen in fishes. Fish is a lower vertebrate with a two
chambered heart. Fish has a two chambered heart comprising of one atrium and one ventricle.
Gills help in purifying the deoxygenated blood. This two chambered heart exhibits single mode of
circulation. Impure blood is pumped to gills for oxygenation. This oxygenated blood from gills is
supplied directly to the body tissues without sending to the heart.
 Incomplete double circulation is observed in amphibians and reptiles which have three-
chambered hearts with two atria and one ventricle.
 Double circulation is the type of circulation during which blood passes twice through the
heart. Higher vertebrates like birds and mammals exhibit double circulation.
Blood pressure
Blood pressure is the pressure exerted by the blood on the walls of the arteries.
 The pressure can be systolic pressure during contraction and diastolic pressure at relaxed state.

4.  The pressure exerted by blood against the wall of an artery during ventricular contraction or
systole is called systolic pressure, and that exerted during ventricular expansion or diastole is
called diastolic pressure.
 Normal blood pressure is 120/80mmHg. If the blood pressure is less than 100/50 then it is termed
to be low blood pressure or hypotension. If it exceeds 140/90, it is termed to be high blood
pressure or hypertension.
 An instrument called the sphygmomanometer is used to measure blood pressure. The normal
systolic pressure is about 120 mm of Hg, and diastolic pressure is 80 mm of Hg.
Transport of gases
Excreationinanimal
Excretion
The process ofthe removal of waste produced in the cells in living organisms is called excretion.The organs that
help in the process ofexcretion constitute the excretory system.
Functions of excretory system
Excretion helps in eliminating different types of wastes.
 Nitrogeneous wastes are the wastes formed in the body as a result of protein metabolism.These
can be in the form of ammonia, urea or uric acid. All these nitrogeneous wastes should be
eliminated from the body due to their toxic nature. Nitrogeneous wastes mix with water in the
body to form urine. Urine is expelled out in periodic intervals.
 Excess sugar from the blood is filtered and sent out through urine in case of diabetic patients.
 Undigested wastes are passed out through anus by the process of egestion.
 Carbon dioxide, an excretory product from every cell is expelled out through lungs.
 Excess salts from the body are eliminated through sweat.
Excretion in lower animals
Lower organisms like amoeba, paramecium, hydra do not possess special organs for excretion. They
eliminate waste products to the environment by the process of diffusion occurring through cell
membrane.