CBSE NCERT Class 7 Science Nutrition in Animals

Question: What do you understand by animal nutrition?

Answer : Animal nutrition includes requirement of nutrients, mode of intake of food, and its utilization in the body.

Question: What are the main steps of digestion in humans?

Answer : The main steps of digestion in humans are ---

(1)  Ingestion (2)  Digestion (3)  Absorption (4)  Assimilation (5)  Egestion

Question: What is digestion?

Answer : The breakdown of complex components of food such as carbohydrates into simpler substances is called digestion

Question: Name the process of taking in food?

Answer : Ingestion.

Question: What are the different modes of taking food into the body in different organisms.

Answer :

Bees and humming-birds suck the nectar of plants

Bees and  humming-birds suck the nectar of plants

Snakes like the python swallow the animals they prey upon.

Some aquatic animals filter tiny food particles floating nearby and feed upon them.

Question: What are   the different modes of feeding in animals

Answer : Scraping, chewing, brewing, capturing and swallowing, sucking etc. are  the different mode of feeding in animals

Question:  Name the type of food and mode of feeding of the following animals-

(a)    Ant  (b)  Mosquito

Answer :

 (a) Ant:  Type of food-Sugar, food particles     

Mode of feeding -Scraping

(b) Mosquito:   Type of food- Blood               Mode of feeding -Sucking

Question: What are the main organs of digestive system

Answer : The main organs of digestive system are liver , Gall bladder Stomach,Pancreas,Small intestine, Large intestine , Rectum ,Anus. The digestive tract and the associated glands together constitute the digestive system.

Question: What are Milk teeth and permanent teeth

Answer : The first set of teeth grows during infancy and they fall off at the age between six to eight

years. These are termed milk teeth.

The second set that replaces them are the permanent teeth. The permanent teeth may last throughout life or fall off during old age.

Question: What causes tooth decay?

Answer : if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it. These bacteria break down the sugars present from the leftover food and release acids. 

The acids gradually damage the teeth and causes tooth decay.

Question: What is mastication?

Answer : Mixing of saliva with chewed food is called mastication this moisten the food and helps in swallowing food.

Question: Write the functions of the tongue.

Answer: 

The functions of the tongue are as follows:

(1) It is used for talking.

(2) It mixes saliva with the food during chewing and helps in swallowing food.

(3) It is used to identify the taste of food like sweet or salty etc. due to presence of taste buds on it.

Question: What is peristalsis?

Answer: The powerful muscles in oesophagus gently push food down to the stomach in a wave - like action, called peristalsis.

Question: What happens to the food in different parts of the digestive tract?

Answer :

The mouth : Our mouth has the salivary glands which secrete saliva. The saliva breaks down the starch into sugars.

Oesophagus - It is along, narrow, muscular tube which directly leads to the stomach.

It is about 25 cm long and passes downwards through the neck, the thorax and the abdominal cavity .

Oesophagus gently push masticated food down to the stomach in a wave - like action, called peristalsis.

The stomach: The inner lining of the stomach secretes mucous, hydrochloric acid and

Digestive juices.

The mucous protects the lining of the stomach by neutralizing acid produced by gastric juice .

The hydrochloric acid  kills many bacteria that enter along with the food and makes the medium in the stomach acidic.

The digestive juices break down the proteins into simpler substances

The small intestine : The small intestine is highly coiled and is about 7.5 metres long .

Liver (reddish brown ) is  the largest gland in the body. 

It secretes bile juice that is stored in a sac called the gall bladder. It digests fats.

The pancreas is cream colored gland secretes pancreatic juice that acts on carbohydrates and proteins and changes them into simpler forms.

he carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acids

The digested food can now pass into the blood vessels in the wall of the intestine having

thousands of finger-like  villi .

The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body

Large intestine:  The food that remains undigested and unabsorbed then enters into the large intestine. 

It is about 1.5 metre in length.

Its function is to absorb water and some salts from the undigested food material.

Question: What are secreted inside the stomach?

Answer :

Gastric juice is secreted by the walls of stomach which contains HCl and Pepsin. 

HCl  helps to kill the germs present in the food. 

After mixing with the food it makes an acidic   medium which is essential for the activation of pepsin enzyme. Pepsin digests protein into peptides.

Question: What are digestive enzymes?

Answer :

There are different types of enzymes which are used for the digestion of different food materials like  carbohydrates, fats, protein etc. The process of digestion involves the association of several catalytic  organic compounds. These are amylase, pepsin, lipase, tripsin etc. These organic compounds are known as digestive enzymes.

Question: Why do we get instant energy from glucose?

Answer :

Glucose is the simplest form of carbohydrate that can be easily broken down to give energy. Hence, we get instant energy from glucose. Moreover, glucose mixes directly into the blood stream making it readily available to the body.

Question: What is absorption?

Answer : The digested food can now pass into the blood vessels in the wall of the intestine. This process is called absorption.

Question: What is the role of villi performing in the small intestine?

Answer :

The villi increase the surface area for absorption of the digested food. The surface of the villi

absorbs the digested food materials and pass into blood. The absorbed substances are transported via the blood vessels to different organs of the body

Question: Why do we get instant energy from glucose?

Answer :  Glucose is the simplest form of carbohydrate that can be easily broken down to give energy. Hence, we get instant energy from glucose.

Question: What is assimilation?

Answer : Absorbed digested food materials transported via the blood vessels to different organs

of the body where they are used to build complex substances such as the proteins required by the body. This is called assimilation

Question: What is egestion?

Answer : The process of  the removal of waste  faecal matter  through the anus fromtime-to-time. This is called egestion.

Question: What is Rumination?

Answer : A process in which partially digested food returns to the mouth in small lumps and the

animal chews it. This type of process is called Remination or Rumination and such types of animals are  called Ruminants. 

Question: How does digestion occur in Ruminants grass-eating animals?

Answer :

 Ruminants quickly swallow the grass and store it in a separate part of the stomach called rumen. Here the food gets partially digested and is called cud.

Later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination. 

The cellulose present in grass  is digested here by the action of certain bacteria which are not present in humans.

Question: Describe nutrition in  amoeba.

Answer : Amoeba is a single-celled organism found in pond water. It has a cell membrane, a dense, rounded nucleus and many bubble-like vacuoles. Amoeba constantly changes its shape and position. It pushes out one or more finger like projections, called pseudopodia or false feet for movement and capturing of food. Amoeba feeds on microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole and digested by the digestive juices.

Question: Write one similarity and one difference between the nutrition in amoeba and human beings.

Answer :

Similarity: Both amoeba and human beings use digestive juices to digest food.

Difference: Humans need to chew food whereas in amoeba, there is no chewing

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