CBSE – 7th Standard Science

CHAPTER 2

Nutrition in Animals

• Plants can prepare their own food by photosynthesis but Animals

• All organisms including humans require food for growth, repair and functioning of the body.

• Animals nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.

• The breakdown of complex components of food like carbohydrates into simpler substances is called
• For digestion in humans, the food passes through a continuous canal consisting of several digestive organs and glands.

• The digestive tract and the associated glands together constitute the digestive system.

• Glands secrete digestive juice which converts complex substance of food into simpler ones.

• The canal can be divided into various compartments as – buccal cavity, food pipe or oesophagus, stomach, small intestine, large intestine, rectum and anus.

• Food is taken into the body through the mouth.

• The process of taking food into the body is called ingestion.

• The swallowed food passes into food pipe.

• Food pipe runs along the neck and chest.

• Food is pushed down by movement of the wall of food pipe.

• Stomach is a thick-walled flattened U shaped bag.

• The inner lining of stomach secretes mucous, hydrochloric acid and digestive juices.

• Small intestine is highly coiled and is about 7.5 m long.

• Small intestine receives secretions from liver and the pancreas.

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

• The absorption of digested food into blood vessels takes place through thousands of fingers like outgrowth called villi.

• LIVER– It is situated in upper part of the abdomen. It is the largest gland in the body.

• It secretes bile juice which is stored in a sac called gall bladder.

• Bile plays an important role in digestion of fats.

• The food that remains undigested enters into large intestine.

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

• The remaining waste passes into the rectum and remains there as semi-solid faeces.

• The faecal matter is removed through the anus. This is called egestion.

• The grazing animals like cows, buffaloes and deer are known as Ruminants.

• They quickly swallow the grass and store it in part of stomach called Rumen.

• The swallowed food returns to mouth and the animal chews it. This process is called Rumination.

• Amoeba is a microscopic single-celled organism.

• It moves and captures the food by pushing out one or more finger like projections called Pseudopodia or False feet.

• The food becomes trapped in the food vacuole.

• Absorbed foods are used for growth, maintenance and multiplication.

• The undigested food is expelled outside by the vacuole.

• Animal nutrition includes nutrient requirement, mode of intake of food and its utilization in the body.

• Human digestive system consists of alimentary canals and secretory glands. It consists of buccal cavity, oesophagus, stomach, small intestine and large intestine ending in rectum and anus.

• The main digestive glands which secrete digestive juices are salivary glands, liver and pancreas.

• Nutrition is a complex process involving ingestion, digestion, absorption, assimilation and egestion.

• The absorbed substances are transported to different parts of the body and the undigested residues are expelled out of the body as faeces through the anus.

• Starfish feeds on animals covered by hard shells of calcium carbonate.

• After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell.

• The stomach then goes back into the body and the food is slowly digested.

• 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 or due to some dental disease.

• Normally 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 break down the sugars present from the leftover food and release acids (see Chapter 5 to know what an acid is).

• The acids gradually damage the teeth This is called tooth decay.

• If it is not treated in time, it causes severe toothache and in extreme cases results in tooth loss.

• Chocolates, sweets, soft drinks and other sugar products are the major culprits of tooth decay.

• Therefore, one should clean the teeth with a brush or datun and dental floss (a special strong thread which is moved between two teeth to take out trapped food particles) at least twice a day and rinse the mouth after every meal.

• Also, one should not put dirty fingers or any unwashed object in the mouth.