Nutrition in Animals
Science Class Seven
Important Terms and Summary
(1) Nutrition: Nutrition requirement, mode of intake of food and its utilization in the body is known as Nutrition.
(2) Need of Nutrition : All organisms including human require food for growth, repair and functioning of body. Getting of nutrients from food and their utilization in body is called Nutrition.
(3) How Plants get Nutrition : Plants synthesize food by the method of Photo Synthesis but animals cannot. Animals get their food from plants. Animals eat food obtained from plants or eat plant eating animals. Thus animals depend directly or indirectly on plants.
(4) Mode of Nutrition :
The process of getting food is called Ingestion. Different animals get their food in using different methods. For example: 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; Tiger, Lion and other flesh eating animals take food in after tearing and chewing the flesh of ther animals, etc.
(5) Digestion in Human: Steps of digestion in human: (a) Ingestion (b) Digestion (c) Absorption (d) Assimilation and (e) Egestion
(6) Ingestion : Taking food in is called Ingestion .
(7) Digestion : The breaking down of complex components of food into simpler substances is called Digestion. Digestion starts right from mouth as food take in and ends at intestine.
(8) Absorption : The passing of digested food into blood vessels from the wall of intestine is called Absorption. The process of Absorption is completed into intestine.
(9) Assimilation : The process in which the absorbed nutrients aer used to build complex substances, such as protein required by the body is called Assimilation.
(10) Egestion : The getting rid of undigested food from body is called Egestion.
(11) Digestive System : The digestive system of human can be divided into 7 parts. These parts are Buccal Cavity, Oesophagus, Stomach, Small Intestine, Large Intestine, Rectum and Anus.
(12) Buccal Cavity : The mouth is called the buccal cavity. Teeth and tongue are present in mouth. When start chewing, salivary gland present in mouth secrets saliva. Saliva, which is a type of amylaze converts starch present in food to sugar. Thus, digestion starts right from mouth.
The process of chewing is called Mastication.
(13) Tongue : Tongue is a fleshy organ present in mouth. Tongue has leaf like structure. Tongue helps in chewing food and enables us to speak.
(14) Teeth : There are two sets of teeth grow in human. First is called milk teeth and other is called permanent teeth.
(15) Milk Teeth : Teeth which grows first are called milk teeth. Milk teeth usually start growing after six month of child birth. The total number of milk teeth are 20, out of which 10 are present in upper jaw and rest 10 grow in lower jaw.
(16) Permanent Teeth : Teeth grow after falling of milk teeth are called Permanent Teeth. There are total 32 permanent teeth in a normal adult human.
(17) Oesophagus: A long pipe like muscular and flexible structure connects mouth and stomach. Oesophagus facilitates chewed food to pass from mouth to stomach. The length of Oesophagus is about 30 cm in an adult person.
(14) Stomach : Stomach is a thick walled j–shaped muscular bag. Stomach is the widest part of alimentary canal. The inner wall of stomach secretes mucos, hydrochloric acid and digestive juices.
Mucous protects the wall of stomach from hydrochloric acid. Hydrochlroric acid kills germs present, if any, in the food. Digestive juice breaks down the protein into simple substances.
Wall of stomach gently churn the food and mix with secreted acid, and digestive juice. In stomach food is converted into semi solid. This semi solid of food is called chime.
(15) Small Intestine : Small intestine has highly coiled pipe like structure. The length of small intestine is about 7.5 meter in an average adult person. Food reaches to small intestine after stomach. In upper part of small intestine food is partly digested. In lower part of small intestine digestion of food completes.
(16) Absorption : Nutrients present in digested food is absorbed in blood through the inner wall of small intestine.
The sending of nutrients from digested food to blood stream from the wall of small intestine is called Absorption.
(17) Villi : There are Many finger like projections present in the inner wall of small intestine are called Villi. These villi increase the surface area of inner wall of small intestine which facilitate the absorption of nutrients present in digested food to the blood stream.
(18) Liver : The liver is a reddish brown gland. Liver is situated in the right side of upper part of the abdomen. The liver is the largest gland in human body. Liver secretes bile juice. The bile juice plays very important role in digestion especially in the digestion of fats.
(19) Gall Bladder : Gall bladder is situated just below the liver. In gall bladder bile juice, which is secreted from liver, is stored.
(20) Pancreas : The pancreas is a large crème coloured gland. Pancreas is located just below the stomach. Pancreas secretes pancreatic juice. The pancreatic juice converts carbohydrates and proteins into simpler forms.
(21) Assimilation : The process of utilization of digested food by different parts of body to release energy is called Assimilation.
(22) Large Intestine : The large intestine is present after the small intestine in the alimentary canal. The undigested food and waste of food enter in the large intestine after small intestine. In large intestine water and some salts are absorbed from undigested food.
(23) Rectum: The last part of large intestine is called rectum. The remaining waste of food in the form of semisolid is stored in the rectum.
(24) Egestion : The residue (faeces) which is stored in rectum is finally thrown out of the body through the anus time to time. The process of removal of faeces from anus is called egestion.
(25) Digestion in grass eating animals : Some of the grass eating animals such as cows, buffaloes, goat, sheep, etc. chewing continuously even when they are not eating anything. Such animals have a separate part in their stomach called rumen. They quickly swallow the grass and store it in rumen. In rumen food is digested partly. This partly digested food is called cud. Later in small lump cud return to the mouth and animal chews it. This process of chewing cud is called rumination. Such animals are called ruminants.
(26) Feeding and digestion in Amoeba : Amoeba is a microscopic and single cell organism. Hence, amoeba is called unicellular animals. It has a cell membrane and a nucleus rounded in shape. There are many small bubbles like vacuoles found in its cytoplasm. An amoeba has finger like projects, which is used for movement and capturing of food. These projections are called pseudopodia or false feet.
Amoeba takes some microscopic organism as food. When an amoeba sense food, it pushes out its finger like projections or false feet around the food particles and engulfs it. In this way food is trapped in a food vacuole. After engulfing food digestive juices are secreted into the food vacuole. These digestives juices act on food and food is broken down into simpler substances. The digested food is absorbed gradually. The absorbed food is used for growth and maintenance of body. The undigested and unabsorbed food is expelled out by vacuoles.
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