Nutrition in Animals Notes

NUTRITION IN ANIMALS • CONTENTS • • • Digestion : The food is digested in the food vacuole by digestive enzymes. Holozoic Nutrition Nutrition in human • Nutrition in a Ruminant Absorption : The digested food present in the food vacuole is absorbed directly into the cytoplasm of amoeba by diffusion. The digested As animals do not have chlorophyll, they can't food just spreads out from the food vacuole into prepare their food own. They obtain their food the cytoplasm of amoeba cell. directly or indirectly from plants. Animals may be herbivores, carnivores or omnivores. • to obtain energy for maintaining life process. HOLOZOIC NUTRITION • In this type of nutrition, animals take in solid food such as fruits, vegetable & meat, etc. Five steps in the process of holozoic nutrition in animals. are (1) Ingestion (2) Digestion (3) Absorption (4) Assimilation (5) Egestion Egestion : When a sufficient amount of undigested food collects inside amoeba, then its cell membrane suddenly ruptures at any place & the undigested food is thrown of the cell. FOOD PSEUDOPODIUM PSEUDOPODIA INGESTION Nutrition in Amoeba : Amoeba is a unicellular animal. It eats microscopic plants & animals that float in water. • Assimilation : Food absorbed by amoeba is used FOOD DIFFUSION OF DIGESTED FOOD FOOD VACUOLE DIGESTION AND ABSORPTION The complete process of nutrition in amoeba is as follows - WASTES EGESTED AFTER DIGESTION Ingestion : An amoeba ingests food by using its ASSIMILATION AND EGESTION Figure : The process of nutrition in amoeba pseudopodia. When a food particles comes near an amoeba, it ingests this food particle by surrounding it with its pseudopodia. The pseudopodia close to form a small cavity called food vacuole. NUTRITION IN HUMAN • Nutrition in human is holozoic. The food ingested through the mouth passes through a number of organ in our body which constitute the alimentary canal. • The alimentary canal along with digestive glands known as digesttive system. BITTER • The digestive system of human consists of SOUR following organs SALTY SWEET MOUTH FIGURE : TONGUE AND ITS TASTE ZONES PHARYNX SALIVARY GLANDS OESOPHAGUS (v) Oesophagus or Food Pipes : It is a connecting LIVER GALL BLADDER tube between the mouth and stomach. The food is STOMACH PANCREAS pushed down towards the stomach by the movement of the muscles of the food pipe. SMALL INTESTINE LARGE INTESTINE FOOD RECTUM ANUS OESOPHAGUS FIGURE : Digestive system of human being (i) Mouth : It is a transvers slit & also called opening of alimentary canal. Mouth opens into buccle cavity. (ii) Buccle cavity : Mouth open into a cavity which contain teeth, tongue & salivary glands. Salivary glands secrete saliva which contain salivary amylase enzyme & convert the starch into simple sugar. (iii) Teeth : Teeth are hard structures held in sockets of the jaws. Teeth cut, chew and break food into smaller pieces. (iv) Tongue : Tongue is the organ used for taste. It contains taste buds to distinguish whether a type of food is sweet, sour, bitter or hot (figure). It also helps in rolling and pushing the food into the pharynx. It mixes the saliva with the food and also helps us in speaking. STOMACH Figure : Movement of the food in the oesophagus (vi) Stomach : Stomach is a J-shaped bag-like structure made of muscles. The stomach secretes gastric juice and hydrochloric acid. Hydrochloric acid kills microorganisms and provides an acidic medium for effective digestion. In the stomach food is throughly mixed with the gastric juice secreted by the gastric glands present in the stomach. The gastric juice contians an enzyme called pepsin which helps to break down proteins into simpler substances. (vii) Small Intestine : It is a coiled tube and is about 7 metres in length. It consists of three parts, namely dueodenum, jejunum and ileum. In the small intestine the food is mixed with bile juice and pancreatic juice. These are secreted by the liver and the pancreas, respectively. Bile juice breaks down fats into fatty acids and glycerol. The pancreatic juice breaks down starch into simple sugar and proteins into amino acids. Digestion of all the components of food gets completed here and the end products are ready for absorption. Absorption of food occurs through millions of small projections in the inner walls of the part of small intestine called ileum. These projections are known as villi. The incorporation of absorbed nutrients into the cell components is called assimilation. The food that remains undigested and unabsorbed then enters the large intestine. (viii) Large intestine : It is the last organ of the digestive system. It is about 1.5 m in length. It consists of three parts, namely caecum, colon and rectum. It helps in absorbing water and in removing undigested solid wastes from the body in the form of faeces through an opening called anus. (ix) Anus : It is the last part of the alimentary canal. Its main function is to expel solid faceces out of the body. (x) Digestive Glands : (a) Salivary Glands : There are three pairs of salivary glands located in the mouth. Salivary glands secrete saliva which contains amylase enzyme. Amylase works on starch and converts it into simple sugar. (b) Liver : It is reddish brown gland and is located in the upper part of the abdomen. It secretes bile juice that is stored in gallbladder. The bile helps in breaking down fat into simpler substances. (c) Pancreas : It is a cream-coloured gland and is located just below the stomach. It secretes pancreatic juice into a small intestine. It acts on carbohydrates and protein and converts them into simpler substances. NUTRITION IN A RUMINANT A ruminant is an herbivours animal which regurgitates its food & digest it in step. For example- Cow, goats, sheep etc. The 2 steps involved in digestion of ruminants are (1) The ruminant first eats the foods & regurgitates a semi digested food called cud. (2) The ruminant then eats the cud when at rest. This process of eating the cud is called ruminating. Ruminants have a special stomach with 4 chambers, which are as follows - • Rumen : This is the largest chamber of the stomach. It is namely used for storing food. • Reticulum : It helps in moving the food bakc to the mouth when needed. • Omasum : This is the smallest chamber of the stomach. Its main function is to absorb excess water. • Abomasum : This is a true stomach where gastric juices are secreted to help digestion. Here the food is digested just like in the human stomach. Disgestion of food in ruminants : The ruminants mostly eat grasses and leaves which are rich in cellulose, The ruminants can digest cellulose becuase celluose-digesting bacteria and protozoa are present in their stomach. OESOPHAGUS ABOMASUM PANCREAS OMASUM SMALL INTESTINE ANUS MOUTH SALIVARY GLANDS RETICULUM LARGE INTESTINE CAECUM RUMEN LIVER FIGURE : Four chambered stomach of cow (ruminant) Half-chewed grass travels from the mouth to the first chamber of the stomach called rumen where it is acted upon by bacteria and microorganism. It then goes into the reticulum from where it is returned to the mouth as cud for through chewing called rumination. It enters a third chamber called omasum. Here it is broken down into still smaller pieces. Finally, it enters the fourth chmaber called abomasum where enzymes act upon it and digestion is completed. It is finally sent to the small intestine where the absorption of the nutrients takes place.