CHAPTER- 2 NUTRITION OF ANIMALS SCIENCE

1. NIDHI KAUSH
CLASS 7
CH-2
NUTRITION IN
ANIMALS

6. Holozoic nutrition: It is a process by which animals take in their food. It involves different steps
namely, ingestion, digestion, absorption, assimilation and egestion.
Human beings exhibit holozoic mode of nutrition involving five basic steps.
Ingestion: The process of taking food into the body is called ingestion.
Digestion: the process in which the food containing large, insoluble molecules is broken down
into small, water soluble molecules is called digestion.
Absorption: The process in which the digested food passes through the intestinal wall into blood
stream is called absorption.
Assimilation: The process in which the absorbed food is taken in by the body cells and used for
energy, growth and repair is called assimilation.
Egestion: The process in which the undigested food is removed from the body is called egestion

7. Digestion in the mouth
We take food through our mouth and
the process of taking food into the
body is called ingestion.
The mouth or buccal cavity contains
teeth, tongue and salivary glands.
Digestion begins in the mouth when
we chew the food with the help of our
teeth.
The teeth cut the food into smaller
pieces, chew and grind it.

8. Chewing breaks down the food into smaller pieces
and mixes them with saliva. This process is called
mastication.
The salivary glands secrete watery liquid called
saliva. Saliva is a digestive juice that helps to
partially digest the starch present in the food.
The tongue helps in mixing saliva with the food.
Tongue is a muscular organ that helps you eat the
food. It mixes saliva with the food during chewing
and helps in swallowing it.
We also taste food with our tongue as it has taste
buds that detect different tastes of food.

9. Milk teeth:- A child has only 20
teeth, 10 in each jaw. These are
known as milk teeth. They begin
to fall at the age between 6 to 8
and then new set of teeth grows.
Permanent teeth:- This set
contains 32 teeth, 16 in each jaw.
There are 4 incisors, 2 canines, 4
premolars and 6 molars in each
jaw.
TEETH
Teeth are used for
cutting, grinding and
tearing the food before
you swallow it.
You have different types
of teeth to do the job.

10. Molars In an adult, these are six
(three on each side) large molars
with the flat surface behind the
premolars in each jaw, for grinding.
MOLARS
Your front teeth are incisors.
They are used for biting and
cutting.
INCISORS.
Premolars These are four (two on each side)
large premolars with the flat surface behind the
canines in each jaw, for grinding and chewing.
PREMOLARS
Next to incisors are canines.
These are pointed and are used
for piercing and tearing pieces of
food.
CANINES.

11. Sweets and Tooth Decay
The tooth is covered by white, hard outer covering of tooth called
enamel below which dentine is present. It is similar to bone which
protects the pulp cavity having nerves and blood vessels.
Bacteria are present in our mouth but they are not harmful to us.
However, if we do not clean our teeth and mouth after eating, many
harmful bacteria also begin to live and grow in it.
These bacteria breakdown the sugars present from the leftover food and
release acids. The acids gradually damage the teeth. This is called tooth
decay.
Therefore, tooth decay is defined as the process of rotting of tooth and
formation of cavity or holes in it which leads to the toothache.
When the holes or cavity reaches to the pulp cavity, it causes pain. If
these cavities are not treated on time it causes severe toothache and
may result in tooth loss.

12. TONGUE
IT IS A MUSCULAR ORGAN ATTACHED AT
THE BACK TO THE FLOOR OF THE BUCCAL
CAVITY.
IT IS FREE FROM THE FRONT AND CAN
HELP IN MIXING SALIVA WITH THE FOOD,
SWALLOWING THE FOOD, TALKING OR
SPEAKING AND TASTING WITH THE HELP
OF TASTE BUDS FOR SWEET, SALT, SOUR
AND BITTER FOOD.
SALIVARY GLANDS SECRETE SALIVA
WHICH BREAKS DOWN STARCH INTO
SUGARS.

14. THE FOOD PIPE OR OESOPHAGUS
IT IS THE TUBE-LIKE STRUCTURE WHICH CONNECTS
THE MOUTH TO THE STOMACH AND RUNS ALONG
NECK AND CHEST.
IT CARRIES SLIGHTLY DIGESTED FOOD FROM THE
MOUTH TO THE STOMACH.
FOOD IS PUSHED DOWNWARD BY A WAVE LIKE
MOVEMENT OF THE WALL OF FOODPIPE AS A RESULT
OF ALTERNATE CONTRACTION AND RELAXATION.
THIS MOVEMENT IS CALLED PERISTALSIS.
THE CHEWED FOOD THAT ENTERS THE OESOPHAGUS
FROM MOUTH AND IS PASSED DOWN TO STOMACH IS
CALLED BOLUS.
SOMETIMES, FOOD IS NOT ACCEPTED BY OUR
STOMACH AND IS VOMITED OUT BECAUSE THE FOOD
MOVES IN THE OPPOSITE DIRECTION, I.E. FROM
STOMACH TO MOUTH BY ANTI-PERISTALTIC
MOVEMENT IN OESOPHAGUS.

15. STOMACH IS THE THICK WALLED BAG PRESENT ON THE LEFT SIDE OF THE ABDOMEN.
(SEE HUMAN DIGESTIVE SYSTEM FIGURE)
IT IS THE WIDEST PART OF THE ALIMENTARY CANAL. OESOPHAGUS BRINGS SLIGHTLY
DIGESTED FOOD FROM MOUTH INTO THE STOMACH.
THE STOMACH WALLS CONTAIN S THREE TUBULAR GLANDS IN IT WALLS WHICH SECRETE
GASTRIC JUICE.
THE GASTRIC JUICE CONTAINS THREE SUBSTANCES: HYDROCHLORIC ACID, THE ENZYME
PEPSIN AND MUCUS.
THE HYDROCHLORIC CREATES AN ACIDIC MEDIUM WHICH FACILITATES THE ACTION OF
THE ENZYME PEPSIN THAT IS THE DIGESTION OF PROTEIN INTO SIMPLE SUBSTANCES.
THE ACID KILLS MANY BACTERIA THAT ENTER ALONG WITH THE FOOD.
THE MUCUS HELPS TO PROTECT THE STOMACH WALL FROM ITS OWN SECRETIONS OF
HYDROCHLORIC ACID.
THE PARTIALLY DIGESTED FOOD THEN GOES FROM THE STOMACH INTO THE SMALL
INTESTINE.

16. Small intestine is highly coiled and is about
7.5 m long.
After leaving stomach food enters small
intestine and last steps of digestion takes
place in small intestine.
It receives secretions from liver and pancreas
and wall of small intestine also secrets juices.
Small intestine

17. Liver:- Liver is the largest gland in the body and is situated in the
upper part of the abdomen on the right side.
It secrets bile juice that is stored in gall bladder
Pancreas:- It is the large cream coloured gland located just below
the stomach. The pancreatic juice acts on carbohydrates, fats and
proteins and converts them into simple form.The partly digested
food now reaches the lower part of the small
The walls of the small intestine contain glands which secretes
intestinal juice.
The enzymes present in it finally convert the proteins into amino
acids, complex carbohydrates into glucose and fats into fatty
acids and glycerol.

18. Absorption:The small intestine is the main
region for the absorption of digested food.
The inner surface of the small intestine has
numerous finger-like projections called villi
which increase the surface area for rapid
absorption of digested food.
The digested food which is absorbed through
the walls of the small intestine goes into our
blood.
ABSOR
PTION

19. The blood carries these useful substances to each and every
part of the body.
The body uses these substances for its growth and
maintenance.
The absorption of digested food and its utilization by the body
is known as assimilation
.Glucose, which is the final product of carbohydrate digestion,
is broken down with the help of oxygen into carbon dioxide
and water to release energy.
Amino acids are used for growth and repair of worn out cells
.Fatty acid and glycerol Store below the skin as energy
reserves.

20. THE UNDIGESTED AND UNABSORBED FOOD MOVES INTO THE
LARGE INTESTINE, TO A PART CALLED COLON, WHERE SOME
AMOUNT OF WATER AND SALTS ARE ABSORBED FROM THE
UNDIGESTED FOOD
THE REMAINING UNDIGESTED FOOD THAT MOVES TO THE
SECOND PART CALLED RECTUM. HERE, IT IS STORED AND
REMOVED FROM THE BODY THROUGH THE ANUS.
THE EXIT OF THIS WASTE MATERIAL IS REGULATED BY THE
ANAL SPHINCTER.
THIS PROCESS IS KNOWN AS EGESTION.

21. Digestion in grass eating animals(ruminants)
Plant eating animals such as cows, deer, goats, buffaloes, camels and yaks quickly swallow
their food after chewing it once.
The swallowed food goes to a chamber called rumen. They bring back the food later into the mouth and chew it again. These animals are called ruminants and the process is called rumination.
The stomach of ruminants consists of four compartments: rumen, reticulum, omasum and abomasum.
The swallowed food first enters the rumen, where the microorganism begins the digestion of the food (cellulose- a complex carbohydrate).
In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separated into layers of solid and liquid material
Solid clump together to form the cud or bolus.

22. The cud is brought back from the rumen to the mouth, where it is
chewed slowly by completely mixing it with saliva and is further
broken down. When the cud is chewed and swallowed again, it
enters the omasum where the food is broken down further into
simple compounds that enter in the abomasum.
Hydrochloric acid and digestive juices (gastric juices) are secreted
in these chambers and the food is now fully digested.
It is then sent to the small intestine for absorption and the leftover
undigested food is passed on to the large intestine from where it is
excreted.
Grass is rich in cellulose and we humans cannot digest it.

24. NCERT EXERCISE
Q.1.FILL IN THE BLANKS:
(A) THE MAIN STEPS OF NUTRITION IN HUMANS ARE ___________, ___________,
___________ , ___________ AND ___________
(B) THE LARGEST GLAND IN THE HUMAN BODY IS ___________.
(C) THE STOMACH RELEASES HYDROCHLORIC ACID AND ___________ JUICES
WHICH ACT ON FOOD.
(D) THE INNER WALL OF THE SMALL INTESTINE HAS MANY FINGER -LIKE
OUTGROWTHS CALLED ___________
(E) AMOEBA DIGESTS ITS FOOD IN THE ___________ .
ANS.(A) INGESTION, DIGESTION, ABSORPTION, ASSIMILATION, EGESTION
(B) LIVER (C) DIGESTIVE (D) VILLI (E) FOOD VACUOLE.

25. NCERT EXERCISE
Q.2. MARK ‘T’ IF THE STATEMENT IS TRUE AND ‘F’ IF IT IS
FALSE:
(A) DIGESTION OF STARCH STARTS IN THE STOMACH.
(B) THE TONGUE HELPS IN MIXING FOOD WITH SALIVA.
(C) THE GALL BLADDER TEMPORARILY STORES BILE.
(D) THE RUMINANTS BRING BACK SWALLOWED GRASS INTO
THEIR MOUTH AND CHEW IT FOR SOMETIME.
ANS. A) F (B) T (C) T (D) T

26. NCERT EXERCISE
Q.3.TICK (S) MARK THE CORRECT
ANSWER IN EACH OF THE FOLLOWING:
(A) FAT IS COMPLETELY DIGESTED IN
THE
(I) STOMACH (II) MOUTH (IN) SMALL
INTESTINE (IV) LARGE INTESTINE
(B) WATER FROM THE UNDIGESTED
FOOD IS ABSORBED MAINLY IN THE:
(I) STOMACH (II) FOOD PIPE (III) SMALL
INTESTINE (IV) LARGE INTESTINE
ANS.(A) (III) SMALL INTESTINE (B) (IV)
LARGE INTESTINE
Q.4.MATCH THE ITEMS OF
COLUMN I WITH THOSE GIVEN
IN COLUMN II:

27. NCERT EXERCISE
Q.5. WHAT ARE VILLI? WHAT IS
THEIR LOCATION AND
FUNCTION?
ANS. THE FINGER LIKE
PROJECTIONS IN THE INNER
WALLS OF THE SMALL
INTESTINE IS CALLED VILLI.
THESE ARE FOUND IN SMALL
INTESTINE.
FUNCTION: THE VILLI INCREASE
THE SURFACE AREA FOR
ABSORPTION OF THE DIGESTED
FOOD
Q.6. WHERE IS THE BILE
PRODUCED? WHICH
COMPONENT OF THE
FOOD DOES IT HELP TO
DIGEST?
ANS. BILE IS PRODUCED
IN LIVER. THE BILE JUICE
STORED IN SAC CALLED
THE GALL BLADDER. IT
HELPS IN THE DIGESTION
OF FATS.

28. NCERT EXERCISE
Q.9. WHICH PART OF THE DIGESTIVE CANAL IS
INVOLVED IN:
(I) ABSORPTION OF FOOD ________ .
(II) CHEWING OF FOOD ________ .
(III) KILLING OF BACTERIA ________ .
(IV) COMPLETE DIGESTION OF FOOD ________ .
(V) FORMATION OF FAECES ________ .
ANS. (I) SMALL INTESTINE (II) MOUTH (III) STOMACH
(IV) SMALL INTESTINE (V) LARGE INTESTINE

29. NCERT EXERCISE
Q. 10. WRITE ONE SIMILARITY AND ONE DIFFERENCE BETWEEN
THE NUTRITION IN AMOEBA AND HUMAN BEINGS.
ANS. SIMILARITY: THE DIGESTIVE JUICES IN AMOEBA ARE
SECRETED INTO FOOD VACUOLE AND IN HUMAN BEINGS THE
DIGESTIVE JUICES ARE SECRETED IN STOMACH AND SMALL
INTESTINE. THEN THE JUICES CONVERT COMPLEX FOOD INTO
SIMPLER SOLUBLE AND ABSORBABLE SUBSTANCES. ‘
DIFFERENCE: AMOEBA CAPTURES THE FOOD WITH HELP OF
PSEUDOPODIA AND ENGULF IT. IN HUMAN BEINGS FOOD IS
TAKEN BY THE MOUTH.

30. NCERT EXERCISE
Q.11. MATCH THE ITEMS OF COLUMN I WITH SUITABLE ITEMS IN
COLUMN II.

31. NCERT EXERCISE
Q.12.LABEL FIG. 2.11 OF THE DIGESTIVE SYSTEM

32. NCERT EXERCISE
Q.13. CAN WE SURVIVE ONLY ON RAW, LEAFY
VEGETABLES/GRASS? DISCUSS.
ANS. WE KNOW THAT THE ANIMALS, FUNGI, BACTERIA, NON-
GREEN PLANTS AND HUMAN BEING DO NOT HAVE THE
ABILITY TO MAKE THEIR OWN FOOD. THEY DEPEND UPON
AUTOTROPHS FOR THEIR FOOD DIRECTLY OR INDIRECTLY.
THE GREEN PLANT (LEAFY VEGETABLES/GRASS) TRAP SOLAR
ENERGY AND MAKE THEIR OWN FOOD IN THE FORM OF
GLUCOSE. SO, WE CAN SAY THAT LEAFY VEGETABLES AND
GRASS CAN PROVIDE SUFFICIENT ENERGY TO HELP US
SURVIVE.