• The components of foods which animals eat such as carbohydrates, fat and proteins are complex solid organic matter. These are changed into simple soluble forms so that they can be easily absorbed in the body and provide nutrients.

• Animal nutrition includes the nutrient requirement, intake of food and its utilization in the body?" We, human beings take wholesome food and so do the majority of the animal. This type of nutrient of readymade solid or liquid organic food is called holozoic nutrition.

Protein for Growth

Carbohydrates for Energy

Fats for Health

Vitamins and Minerals

Water Functions


• Protein builds new cells and fixes damaged ones in all parts of your body. During childhood, adolescence and pregnancy protein is especially important for growth. Protein is made up of amino acids. Along with growth and repair, they preserve muscle mass, hormone production, enzyme production, properly functioning immune system and to provide energy if carbohydrates aren’t available. Protein is found mostly in meat, eggs, fish, nuts, seeds and beans.


• Carbohydrates are broken down to the simplest form as glucose, which is your body’s main source of energy. Carbohydrates are important for your brain, nervous system, kidneys and muscles. They are mainly stored in the liver and muscles to use later for energy. Fiber, a type of carbohydrate, removes waste and promotes bowel health by allowing waste to move more quickly through your gut. They are mostly found in grains, fruits and milk but are also found in nuts, seeds, beans and vegetables.


• Fats are broken down into their simplest form of fatty acids. Fat is used for cell membranes, energy, absorbing fat soluble vitamins, support for your internal organs and to provide taste and texture to food. Types of fats are monounsaturated, saturated and trans fats. Good fats, or unsaturated fats, include olive oil, avocados and nuts. Bad fats, otherwise known as saturated fats, are meat, butter and lard. Trans fats, or very bad fats, are in baked goods, fried foods and snack food.

Vitamins and Minerals

• Vitamins and minerals are essential because they connect with each other and perform many different things in your body. Water soluble vitamins are in the watery parts of food and can move freely throughout your body. They form energy, build protein and make collagen. Fat soluble vitamins are in fatty foods and have to be transported through your body through a protein escort. They interact with each other to protect eyes, bones, skin, lungs and your intestines. Major minerals, or electrolytes, balance bodily fluids. Trace minerals perform various tasks such as carrying oxygen throughout your body, blood clotting, immune system and strengthening bones.


• You drink water to replenish what you lose through waste removal, sweat and everyday metabolic functions. Water is important for keeping a normal body temperature, urination, bowel movements, sweating, protecting your spinal cord and providing a barrier for your joints. Increase your water intake with exercise, fever, illness and when the temperature is hot.


The digestive system in humans includes a set of organs which help in the process of digestion of food. This set of organs is called the alimentary canal and some related organs (glands) which secrete digestive juices and enzymes into the alimentary canal to help digestion of food. The alimentary canal is a long tube which begins from the mouth and ends at the anus. It consists of mouth, pharynx, oesophagus, stomach small intestine, large intestine, rectum and anus.










The process of digestion begins in the mouth. The mouth contains teeth, tongue and salivary glands and mixes it with saliva. Saliva is a digestive juice which is secreted by the salivary gland. They work together in chewing the food. Chewing breaks down the food into small pieces and mixes it with saliva. The mixing and chewing of food is called mastication. Saliva contains the enzyme amylase which converts starch into sugar so it tastes sweet.



From the mouth, the food is pushed down into the next organ called food pipe or oesophagus. It acts as a passage to carry the food from the mouth to the stomach without any digestion. Food is pushed down by the wave-like movement of the wall of the food pipe. This wave-like movement in the food pipe which pushes food forward is called peristalsis. It can be seen throughout the alimentary canal.





From the oesophagus, the food reaches the stomach, which is a thick-walled, bag-like structure. It is the widest part of the alimentary canal. It is highly elastic and receives food from the food pipe at one end and opens into the small intestine at the other The inner membrane of the stomach secretes a juice called gastric juice and acid called hydrochloric acid. The enzyme present in gastric juice breaks down the proteins into peptones and peptides. The mucus protects the stomach wall from being corroded by the action of hydrochloric acid. Food remains in the stomach from a few minutes to a few hours depending on the type of food.



It is the most important part where digestion of food gets completed. It is the longest part of the alimentary canal (approximately 6 m in length) arranged in coils. Digestive juices from the liver and pancreas are secreted into the small intestine, which helps to digest the semi-digested food (chyme) completely. The liver is a reddish-brown coloured gland, situated on the right side, just above the stomach. It is the largest gland in the body. It secretes a green liquid, called bile. Bile is temporarily stored in a hollow pear-shaped orange, the gall bladder attached to the liver Bile is alkaline and helps to neutralize the acidity of food leaving the stomach. It also helps in breaking of fats. The pancreas is an organ located between the stomach and the first part of the small intestine. The small intestine completely breaks down carbohydrates into simple sugars like glucose, fats into fatty acids and glycerol and proteins into amino acids

Undigested and unabsorbed food from the small intestine reaches the large intestine where excess water and minerals from this food are absorbed by its walls and the semi-solid waste food is passed into the rectum from where it is passed out through the anus. Rectum stores faeces (waste) for being pushed out of the body through the anus (the end opening of the alimentary canal). This is called egestion or defecation.



The food absorbed into the blood is transported to different parts of the body. It is used to provide energy and materials for growth and repair of the body tissues. This is the final stage in the process of digestion and is known as the assimilation of food. Glucose is broken down in the cells with the help of oxygen into carbon dioxide and water, to provide energy. Amino acids are used for building and repairing of body parts. Fatty acids and glycerol are stored under the skin and act as energy reserves.


Ruminants are hooved, plant-eating animals that digest their food in two steps. Some examples are cows, buffaloes, goats, sheep and bison. In the first step, they hurriedly eat the food; half chew it and quickly swallow it. In their leisure time, when they are relaxing, the food comes back into their mouth in small lumps for further chewing. This process is called chewing the cud or rumination and that is why these animals are called ruminants. Ruminants have a unique stomach divided into four chambers- rumen, reticulum, Omasum and Abomasum.





Amoeba is a unicellular organism and all the processes of nutrition in it are carried out by a single cell. In Amoeba, the food is collected with the help of temporary finger-like projection called pseudopodia. The food particles are ingested (engulfed) by one pseudopod. When two encircling pseudopodia meet, a food vacuole is formed containing the prey. Digestion of the prey takes place in the food vacuole in the cytoplasm. This type of digestion which takes place within the cell is termed as intracellular digestion. The digested food diffuses into the cytoplasm from the food vacuole. The undigested matter is thrown out of the body. This process is called egestion.