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Nutrition in Animals Class 7 Notes Science Chapter 2

Nutrition in animals refers to the process by which animals obtain and utilize nutrients to support their growth, maintenance, and reproduction. Animals require various nutrients, including carbohydrates, proteins, fats, vitamins, minerals, and water, to sustain life and carry out metabolic activities

Nutrition in Animals Class 7 Notes Science Chapter 2

What is Digestion?

Food is required by all organisms. The intake of food is called ingestion. The ingested food is broken down into simpler substances in the process called digestion.

What is Nutrition ? 

Nutrition involves the intake of food and its conversion into energy and nutrients essential for an organism's growth and development. The process comprises several stages:

  • Ingestion: The act of consuming food.
  • Digestion: Breaking down complex food molecules into simpler forms for absorption.
  • Absorption: The passage of digested food molecules into the bloodstream through the intestinal wall.
  • Assimilation: Utilizing absorbed nutrients to produce essential substances like proteins for bodily functions.
  • Egestion: The elimination of waste or fecal matter from the body.

Different Ways of Taking Food

Each species or type of organism has their own way of taking in food. Bees and hummingbirds suck plant-nectars, infant of humans and some animals feed on mother’s milk, Snakes such as python consume the animals upon which they prey. Aquatic animals filter small food particles floating close by and feed on them.

All organisms have their unique ways of consuming food, tailored to their physiology. These methods include:

  • Chewing: This involves biting and grinding food using teeth within the mouth. Examples include humans and dogs.
  • Scraping: Here, an organ like the jaw scrapes food off a surface. Examples are seen in snails and ants.
  • Syphoning: Food is absorbed into the mouth. Butterflies use this method.
  • Capturing and swallowing: This involves seizing food and then swallowing it whole. Lizards are an example.
  • Sucking: Organisms pierce food and draw out liquid. Mosquitoes utilize this method.
  • Sponging: Saliva combines with food to dissolve it in the mouth. Houseflies demonstrate this approach.

Digestion in Humans

The human digestive system contains alimentary canal and associated glands. The digestive system of man consists of Mouth, Buccal Cavity, Oesophagus, Pharynx, Stomach Duodenum, Small Intestine, Large Intestine (colon), Rectum and Anus.

Human Digestive SystemHuman Digestive System

1. The Mouth and Buccal Cavity

  • Mouth and Buccal Cavity is bounded by the upper lip and lower lip.
  • Food is entered into the Buccal Cavity through mouth is called ingestion. 
  • The food is crushed and chewed in the Buccal Cavity with the help of the teeth and tongue. 
  • The Buccal Cavity leads into pharynx.
  • The different teeth present in the Buccal Cavity are incisors, canines, premolars and molars.
  • Salivary glands are present inside the Buccal Cavity. They secrete saliva. This saliva plays an important role in breaking down complex components like starch, which is further simplified into sugars.

Nutrition in Animals Class 7 Notes Science Chapter 2

Fig. Buccal cavity


2. The Foodpipe /Oesophagus

A flap-like valve called the epiglottis closes the windpipe. It prevents the entry of food particles into tracheae. Movement of food inside the esophagus in the stomach is by peristalsis movement. 

3. The Stomach

Stomach is u-shaped and it is the widest part of the alimentary canal. Food is digested inside the stomach with the help of gastric juice secreted by the gastric glands present in the stomach.

  • Liver is the largest gland in our body. It produces bile juice. Bile plays an important role in the digestion of fats.
  • Pancreas is the Mixed gland, it acts as both an endocrine and an exocrine gland.
  • The pancreas secretes the pancreatic juice that helps to digest carbohydrates, proteins and fats. The pancreatic juice converts carbohydrates into simple sugars and glucose, proteins into amino acids, and the fats to fatty acids and glycerol.

4. Small Intestine

The inner walls of the small intestine have millions of small finger-like projections called the Villi. Due to their presence the surface area for digestion as well as absorption of digested food increases by eight times.

  • Energy needed for various activities is obtained from glucose.
  • This process of utilization of absorbed food, such as glucose, amino acids, fatty acids and glycerol is called as Assimilation.

Absorption in the Small Intestine

The process of utilization of absorbed food such as glucose, amino acids, fatty acids and glycerol is known as assimilation.

  • The inner walls of the small intestine have millions of small finger-like projections, called the villi. The surface of the villi allows amino acids and glucose to reach the blood capillaries, and allow fatty acids and glycerol to reach the lymph vessels, a process called absorption.

5. Large Intestine

The undigested and unabsorbed food then enters the large intestine.  The food then travels upward in the ascending colon of the large intestine.

  • The function of the large intestine is to absorb the water and salts from the undigested food material. 
  • The undigested semi-solid waste that passes into the Rectum is called faeces
  • It is then removed through the anus at intervals in a process called Egestion.

Question for Chapter Notes: Nutrition in Animals
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Which part of the alimentary canal is responsible for the digestion of fats?
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Digestion in Green Eating Animals

Cellulose is an important component in the diet of herbivorous animals.  It is present in the cell wall of plant cells. 

  • Humans cannot digest cellulose. 
  • Grass eating animals like the cow, ox, buffalo and sheep swallow the food without chewing. 
  • After feeding, they bring the food from the stomach back into the mouth and chew it leisurely. 
  • This process is called rumination, and such animals are called ruminants. Digestive System in Cow
    Digestive System in Cow
  • The stomach of a ruminant is divided into four chambers - the rumen, reticulum, omasum and abomasums. Among these, the rumen is the largest.
  • The partially digested food in the rumen is called cud.
  • Micro-organisms present in the stomach of the cow help digest the cellulose.
  • Digestion in ruminants

Grass eating animals like cows, sheep, buffaloes and goats do not chew their food properly. Instead, they swallow it quickly and store it in the rumen. In the rumen, the digestive juices partially digest the food. The partially digested food in the rumen is called cud.

  • Partially chewed food is pushed down through the oesophagus into the rumen.
  • The cud is brought back to the mouth to be chewed properly. 
  • The process of chewing cud is called rumination. 
  • Rumination is also called second chewing. 
  • Animals that partially digest food in the rumen and bring it back to the mouth for additional chewing of the cud are called ruminants.
  •  A large sac-like structure, called the caecum, lies between the small and large intestines.

Ruminants have green plants as their food. These plants contain a type of complex carbohydrate, called cellulose. In the caecum, a kind of symbiotic bacteria helps digest cellulose. In ruminants, a major part of all carbohydrates, including the complex carbohydrates such as cellulose and hemicellulose, is digested by bacterial action.

These symbiotic bacteria are not present in the human digestive system. That is why humans cannot digest cellulose.

Question for Chapter Notes: Nutrition in Animals
Try yourself:Why can't humans digest cellulose?
View Solution

Feeding and Digestion in Amoeba

  • The amoeba is a microscopic unicellular organism which belongs to the group protozoa
  • The name comes from the Greek word amoibe, meaning change. 
  • The habitat of the amoeba is freshwater. 
  • The amoeba contains jelly-like cytoplasm. 
  • Inside the cytoplasm are cell organelles like the nucleus, food vacuoles and contractile vacuole. 
  • An amoeba takes in oxygen gives off carbon dioxide through the cell membrane by a mechanism of diffusion. 
  • It takes in oxygen dissolved in water. An amoeba can move all directions and can change its shape with the help of pseudopodia as a locomotory organ.Nutrition in Animals Class 7 Notes Science Chapter 2
    Fig. Steps involved in digestion in amoeba
  • An amoeba engulfs its prey along with a droplet of water with the help of pseudopodia and then forms a food vacuole inside the cytoplasm. 
  • The prey can be killed and digested with the help of the digestive juice secreted by the food vacuole. 
  • The undigested food is thrown out by changing the shape of the body. 
  • Amoeba forms a cyst in unfavorable conditions.
  • The term amoeba is derived from the Greek word amoibe, meaning change.
  • The amoeba is one of the simplest jelly-like animals. the ultimate shapeshifter. 
  • An amoeba is so minute that it can be seen only under a microscope.
  • Amoebae are found at the bottom of freshwater bodies like ponds and lakes, even in a gutter or muddy water. 
  • Some of them are also found in damp soil and food.
  • The amoeba is a single-celled animal. 
  • The amoeba has a jelly-like substance, called the cytoplasm, inside a flexible boundary called the cell membrane. 
  • Floating in the cytoplasm are various structures like the nucleus, food vacuoles and contractile vacuoles.

An amoeba takes in dissolved oxygen from the surrounding water, and gives off carbon dioxide into the water through the cell membrane.

  • An amoeba can move in all directions using temporary feet-like structures, called pseudopodia. 
  • An amoeba, with the help of pseudopodia, captures and engulfs its prey along with a droplet of water.

In an amoeba, digestive juices convert food particles into simpler substances. 

  • The cytoplasm absorbs digested food directly, and uses it for growth, maintenance and multiplication.

In the amoeba, undigested remains of food are thrown out of the body. An amoeba roll into a tiny ball called cyst during unfavorable conditions.

The document Nutrition in Animals Class 7 Notes Science Chapter 2 is a part of the Class 7 Course Science Class 7.
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FAQs on Nutrition in Animals Class 7 Notes Science Chapter 2

1. What are the different ways of taking food?
Ans. The different ways of taking food include chewing and swallowing solid food, drinking liquids, and consuming semi-solid or pureed food through a feeding tube.
2. How does digestion occur in humans?
Ans. Digestion in humans starts in the mouth where food is broken down by chewing and mixed with saliva. It then travels down the esophagus into the stomach, where it is further broken down by stomach acids and enzymes. The partially digested food then enters the small intestine where it is broken down into nutrients and absorbed into the bloodstream. The remaining waste material passes into the large intestine where water is absorbed, and finally, the waste is eliminated through the rectum.
3. How does digestion occur in green-eating animals?
Ans. Green-eating animals, such as cows and sheep, have a specialized digestive system that allows them to extract nutrients from plant material. They have a large fermentation chamber, called the rumen, where plant material is broken down by bacteria and other microorganisms. The partially digested material then passes into the other compartments of the stomach, where further digestion and absorption of nutrients occur.
4. What is the process of feeding and digestion in amoeba?
Ans. Amoeba is a single-celled organism that takes in food through a process called phagocytosis. It extends its pseudopodia (temporary projections) to surround and engulf food particles, forming a food vacuole. Enzymes are then released into the food vacuole to break down the food into simpler substances. The nutrients are absorbed into the cytoplasm of the amoeba, and the remaining indigestible waste is expelled through the cell membrane.
5. What is the significance of nutrition in animals?
Ans. Nutrition is essential for animals as it provides the necessary energy and nutrients for growth, repair, and maintenance of body functions. It enables animals to carry out vital processes such as respiration, reproduction, and movement. Proper nutrition also helps animals maintain a healthy immune system, preventing diseases and ensuring overall well-being.
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