Nutrition in Animals and Humans is an important topic in General Science for competitive examinations such as ADRE, Assam Police, APSC and other Assam government exams. This chapter explains how animals obtain food, digest it, absorb nutrients and remove waste from the body.
1. Modes of Procuring Food
Different organisms use different methods to obtain food.
Human beings: use their hands to put food into the mouth.
Cow and horse: take food directly into the mouth.
Amoeba: uses pseudopodia (false feet) to engulf food.
Paramecium: uses cilia, which are hair-like structures, to sweep food particles into the body.
Frog: uses its sticky tongue to catch prey.
2. Process of Nutrition
The major steps involved in nutrition are:
Ingestion
The process of taking food into the body is called ingestion.
Digestion
The process by which complex food molecules are broken down into simpler and soluble substances is called digestion.
Absorption
The process by which digested nutrients pass into the blood is called absorption.
Assimilation
The incorporation and utilisation of absorbed nutrients by body cells is called assimilation.
Egestion
The removal of undigested food from the body in the form of faeces is called egestion.
ADRE Quick Trick
I → D → A → A → E
Ingestion → Digestion → Absorption → Assimilation → Egestion
3. Teeth in Human Beings
Humans have two sets of teeth:
1. Milk teeth
2. Permanent teeth
The first set consists of 20 milk teeth. They are gradually replaced by permanent teeth.
An adult human normally has 32 permanent teeth.
Type of tooth Number in each jaw Function
Incisors 4 Cutting and biting
Canines 2 Tearing
Premolars 4 Chewing and grinding
Molars 6 Chewing and grinding
Total 16
Therefore:
16 teeth × 2 jaws = 32 permanent teeth
Functions of Teeth
Incisors: cut and bite food.
Canines: tear food.
Premolars: chew and grind food.
Molars: chew and grind food.
4. Structure of a Tooth
A tooth has three main external parts:
Crown
The visible portion of the tooth above the gum is called the crown.
Neck
The portion between the crown and root is called the neck.
Root
The part of the tooth embedded in the jaw is called the root.
Internal Parts
Enamel:
The hard outer covering of the tooth. It is the hardest substance in the human body.
Dentine:
A hard, bone-like layer beneath the enamel.
Pulp cavity:
The soft inner part containing blood vessels and nerves.
5. Care of Teeth and Oral Hygiene
Proper oral hygiene is essential for healthy teeth and gums.
Important points
Brush your teeth properly twice a day.
Clean your mouth after eating.
Use a soft toothbrush.
Clean between the teeth appropriately.
Eat fresh fruits and vegetables.
Avoid excessive sticky and sugary foods.
What is Plaque?
Plaque is a sticky layer containing food particles, saliva and bacteria.
Bacteria in plaque can convert sugars and starches into acids. These acids can damage tooth enamel and may cause cavities.
6. Human Digestive System
The digestive system helps convert food into simpler substances that can be absorbed and used by the body.
The main parts of the alimentary canal are:
Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
Important digestive glands/organs include:
Salivary glands
Liver
Pancreas
Gall bladder
Alimentary Canal
The continuous digestive tube from the mouth to the anus is called the alimentary canal.
7. Digestion in the Mouth
Digestion begins in the mouth.
Food is chewed by the teeth and mixed with saliva.
The three major components of the mouth involved in eating and digestion are:
Teeth
Tongue
Salivary glands
Role of Saliva
Saliva makes food moist and slippery, making swallowing easier.
The enzyme salivary amylase begins the digestion of starch.
Starch → simpler sugars
8. Oesophagus
The oesophagus, or food pipe, is a muscular tube connecting the mouth to the stomach.
After swallowing, food moves towards the stomach through rhythmic muscular movements called peristalsis.
9. Digestion in the Stomach
The stomach is a J-shaped, muscular organ.
Gastric glands in the stomach produce gastric juice containing:
Hydrochloric acid
Mucus
Digestive enzymes
Functions
Hydrochloric acid: provides an acidic medium and helps kill many microorganisms.
Mucus: protects the stomach lining.
Digestive enzymes: help digest food, especially proteins.
The stomach muscles churn food and mix it with gastric juice.
10. Small Intestine
The small intestine is a long, narrow and coiled part of the alimentary canal.
Most digestion is completed in the small intestine.
Partially digested food mixes with:
Pancreatic juice
Bile
Intestinal juices
The end products of digestion are then ready for absorption.
11. Absorption of Digested Food
The inner wall of the small intestine contains numerous finger-like projections called villi.
Functions of Villi
Increase the surface area for absorption.
Help digested nutrients enter the blood.
Help transport nutrients to different parts of the body.
Important ADRE Fact
Villi are mainly responsible for increasing the surface area of the small intestine for absorption.
12. Assimilation
After absorption, nutrients are transported by the blood to different cells.
The incorporation and utilisation of these nutrients by body cells is called assimilation.
The absorbed nutrients may be used for:
Energy
Growth
Repair
Other body functions
13. Large Intestine and Egestion
The large intestine absorbs much of the remaining water and some salts from undigested material.
The remaining waste passes into the rectum.
The removal of undigested food from the body through the anus is called egestion.
14. Digestion in Grass-Eating Animals
Grass-eating animals such as cows and buffaloes feed mainly on plant material.
Animals such as cows are ruminants.
They have a specialised digestive system that helps them digest plant material.
Rumination
Ruminants initially swallow grass and later bring partially digested food back into the mouth for further chewing.
This process is called rumination.
15. Digestion of Cellulose
Grass is rich in cellulose.
Humans cannot efficiently digest cellulose because they do not produce the necessary enzyme for cellulose digestion.
Ruminants have microorganisms in their digestive system that help break down cellulose.
Important Exam Point
Cellulose digestion in ruminants is helped by microorganisms present in their digestive system.
16. Feeding and Digestion in Amoeba
Amoeba is a unicellular organism.
It obtains food using pseudopodia, also called false feet.
Steps
1. Pseudopodia surround the food particle.
2. The food is engulfed.
3. A food vacuole is formed.
4. Digestive enzymes act on the food.
5. Useful nutrients are absorbed and utilised.
6. Undigested material is expelled.
ADRE Important One-Liners
1. The process of taking food into the body is ingestion.
2. Breakdown of complex food into simpler substances is digestion.
3. Digested nutrients entering the blood is absorption.
4. Utilisation of absorbed nutrients by cells is assimilation.
5. Removal of undigested food is egestion.
6. The hardest substance in the human body is tooth enamel.
7. Humans normally have 32 permanent teeth.
8. Incisors are used for cutting and biting.
9. Canines are used for tearing.
10. Premolars and molars help in chewing and grinding.
11. The food pipe is called the oesophagus.
12. The muscular movement that pushes food through the oesophagus is peristalsis.
13. Digestion begins in the mouth.
14. Salivary amylase begins starch digestion.
15. Most digestion is completed in the small intestine.
16. Villi help in absorption.
17. The large intestine mainly absorbs water and some salts.
18. Pseudopodia are used by Amoeba for feeding.
19. Cilia help Paramecium obtain food.
20. Rumination is characteristic of ruminant animals.
ADRE Exam Focus
For ADRE preparation, give special attention to:
Nutrition processes + teeth and functions + digestive organs + digestive enzymes + villi + absorption + ruminants + Amoeba feeding.
Keywords: ADRE Science Notes, ADRE General Science, Nutrition in Animals and Humans, ADRE Science Questions, Human Digestive System Notes, Digestion in Humans, Assam Direct Recruitment Science Notes.
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