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Class VII - science: Nutrition In Animals
One Word Answer Questions:
Q) The breakdown of complex components into simpler substances is called?
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Q) Name the canal through which food passes?
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Q) Name a gland which secretes digestive juices?
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Q) Name a sac in which the bile juice is stored?
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Q) The microscopic single celled organism which is found in pond water is called?
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Q) Which adaptation helps animals to protect themselves?
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Q) The natural home of an animal is called its?
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Short Answer Questions:
Q) What are milk teeth and permanent teeth?
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Q) What is tooth decay and can we prevent it?
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Q) Explain the function of large intestine?
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Q) Explain the function of Oesophagus?
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Q) Explain about the digestive system of Amoeba?
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Q) What are Villi? What is their location and function?
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Q) Differentiate between the small intestine and the large intestine?
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Q) How do animals living in cold regions?
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Q) What are arboreal animals?
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Q) Explain omnivores and parasites?
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Q) Why do aerial animals have light bodies?
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Q) How do animals like fish, elephant and leaf insect protect themselves?
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Q) Explain adaptations to environment?
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Q) Explain about Structure of seeds?
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Q) Explain about Agriculture?
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Long Answer Questions:
Q) Explain briefly about the human digestive system?
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Q) Name the type of carbohydrate that can be digested by the ruminants and not by the humans? Give an appropriate reason?
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Q) The frog is an amphibian? How it is adapted to live on land and in water?
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Q) What are the Dispersal of seeds?
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Nutrition In Animals

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

The intake of food is called ingestion. Method of ingestion, i.e. taking of food, varies from one animal to another.


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.


The process of passing of digested food into blood vessels in the intestine is called the absorption.


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.


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 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.
  • 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.

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 Humans

The digestive system of humans is well developed. It consists of the gut or alimentary canal, along with many associated digestive glands. The alimentary canal is divided into mouth, oesophagus, stomach, small intestine, large intestine and rectum.

nutrition in animals
Digestion In Human
The mouth and buccal cavity:

The food is ingested through the mouth. The mouth contains tongue, teeth and salivary glands. Teeth break the food into smaller particles. This process is called mastication. The chewed food is mixed with saliva. Saliva is a watery fluid secreted by the salivary glands. Saliva contains a type of enzyme called the salivary amylase, which converts starch into sugar.


Our teeth cut, tear and grind the food before we swallow it. There are four types of teeth in our mouth.

nutrition in animals

These are flat and chisel-shaped teeth. They lie in the front of the mouth. There are eight incisor teeth; four in the upper jaw and four in the lower jaw. The incisor teeth are well adapted for cutting and biting of food items.


These are round shaped, sharp and pointed teeth. Canines are well adapted to hold and tear the food. There are four canine teeth found in human.


There are two premolars on each side of each jaw. Premolars help in crushing and grinding the food. There are total 8 premolar teeth in an adult human.


There are two molars on both sides in both the jaws. They have almost a flat surface with small projections. These teeth are meant for fine grinding of food. There are total 12 molar teeth including the wisdom teeth in an adult human. The 4 molar teeth are also called wisdom teeth. Wisdom teeth usually grow between the ages of 18 to 21.The tooth is covered with a white substance called enamel. It is the hardest substance in the human body

Milk teeth and Permanent teeth

Humans get two sets of teeth in their lifetime. The first set erupts when we are babies, are called milk teeth. Milk teeth last until we are about 8 years old. Milk teeth are replaced by the second set of teeth and are called permanent teeth.
An adult human has 32 teeth in all; 16 in each jaw.


The tongue is a muscular organ. Tongue helps to mix saliva in the food. It also helps to push the food down the food-pipe or oesophagus. Taste receptors are present in tongue and give us the sense of taste.

nutrition in animals

Oesophagus is also called food pipe. It is a tube-like structure connecting the mouth and the stomach. It is about 30 cm. long. Oesophagus has powerful muscles which gently push the food down to the stomach. The oseophagus contracts and relaxes in a rhythmic fashion to facilitate the forward movement of food. This movement happens in other parts of the alimentary canal as well and is called peristalsis. Digestion does not takes place in oesophagus

nutrition in animals

It is a muscular J-shaped thick walled bag. Stomach is the widest part of alimentary canal. It receives food at one end from food pipe and open into the small intestine from other end. Stomach churns the food to mix digestive juices. The food in the stomach is churned into semi solid. The churned semi-solid food is called chime. Gastric juice is secreted from the wall of stomach and mixed with food. Gastric juice contains some enzymes and hydrochloric acid. The enzymes present in the gastric juices break down protein from food. The hydrochloric acid kills the harmful bacteria present if any in the food and helps the gastric enzymes to work.

Small intestine:

The food leaves the stomach at certain intervals of time and enters into the small intestine. The small intestine is the longest part of the digestive system. It is about 20 feet or seven meters long in an adult human. Small intestine is a highly coiled tube. It consists of three parts: duodenum, jejunum and Ileum.

In the duodenum, the liver and pancreas pour their secretions. Liver secretes bile juice and pancreas secretes the pancreatic juice. The bile juice contains the bile which carries out emulsification of fat. In this process, the fat is broken into tiny droplets. The pancreatic juice contains several enzymes. The enzymes of the pancreatic juice break down starch into simple sugars and proteins into amino acids.

Minerals and vitamins do not need to be changed because cells are able to absorb them easily. From duodenum the food goes to the lower part of the intestine. There are numerous finger-like projections on the wall of the small intestine. These projections are called villi. They have fine blood capillaries to absorb the food. After absorption; food mixes in the blood stream and is carried to all the cells of the body. The cells utilize this food to release energy.

Large intestine:

The digested food enters into large intestine after small intestine. The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length. In large intestine excess of water from the materials is absorbed. The semi solid residue is stored in the last part of the large intestine called rectum and finally throw out of the body through the anus time to time. The throwing out of waste of digested food from rectum is called egestion. Egestion is also known as defecation.


Some grass eating animals like cows, buffaloes, continuously chew their food even after eating. This is because they quickly swallow the grass and store it in a part of the stomach called rumen.

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 chambers.
  • rumen
  • reticulum
  • omasum
  • 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.

nutrition in animals
Digestive System Of Ruminant(Cow)

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 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.

Amoeba: It is a microscopic single celled organism which is found in pond water. Amoeba has a cell membrane, a rounded dense nucleus and many small bubbles like vacuoles in its cytoplasm. It constantly changes its shape and position and pushes out one, or more fingers like projections called pseudopodia or false feet for movement and capture of food.
nutrition in animals
  • Amoeba feeds on some microscopic organisms. When it sense food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole.
  • The digestive juices which are secreted by the food vacuole act on the food and break it into simpler substances. Gradually the digested food is absorbed.
  • The absorbed substances are used for growth, maintenance and multiplication and the undigested residue of the food is expelled outside by the vacuole. All animals have similar process of digesting food and releasing energy.
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