Nutrition in Animals Class 7 Notes: CBSE Science Chapter 2

Animal Nutrition:

This is a term that includes the nutrient requirement of the animal, its mode of food intake and the utilisation of the food in their bodies.

Classification of Animals Based on Feeding Habits:

It is of great importance that all organisms intake food in some way or the other for their growth and normal functioning of their body. Based on their feeding habits they can be classified as:

1. Herbivorous: This is the group of animals that feed only on plants or their products as the name suggests; ‘herbi’ meaning plant and ‘vore’ meaning eaters. Example: cow, sheep, deer, rabbit, camel, kangaroo, giraffe, etc.

2. Carnivorous: This is the group that feeds on the meat of other animals and the name suggests the same as, ‘carni’ means meat. Example: tiger, lion, bear, snake, eagle etc.

3. Omnivorous: This group of animals can feed on plants as well as the meat of other animals and the name ‘omni’ means all. Example: dog, human beings, etc.

4. Scavengers: This group of animals feed on dead and decaying meat left by other animals. Example: vulture, crows, jackal, etc.

Mode of Taking Food:

Although all organisms require food, the way they take it into their body differs from each other. All of them have special adaptations that help them for this. They could be as follows:

1. Chewing: This mode involves the biting and grinding of the food in the mouth by the teeth. Example - humans, dogs, etc.

2. Scraping: In this mode, the food is scraped off the surface by the jaw or an organ. Example - snails, ants etc.

3. Siphoning: In this mode, the food is sucked into the mouth. Example - bees, butterflies etc.

4. Capturing and swallowing: In this mode they usually capture the food and then swallow them. Example: lizard, etc.

5. Sucking: This mode involves the piercing of the food and then sucking the liquid out of it. Example: mosquitoes, etc.

6. Sponging: In this mode, the saliva is secreted over the food to dissolve it in order to draw it into the mouth. Example: houseflies etc.

Nutrition:

The process of taking in the food and converting it into necessary energy and nutrients for the growth and development of an organism is termed as nutrition. The process of nutrition is a complex one and includes some steps which are:

1. Ingestion: The process of intake of food into the body.

2. Digestion: The process of breaking down the ingested complex food molecules to simpler molecular form that can be absorbed by the body.

3. Absorption: The process by which the digested food is taken into the blood vessels.

4. Assimilation: The process of transporting the absorbed food to the various organs to build substances like proteins, etc.

5. Egestion: The process of eliminating the waste products from the body.

Digestion in Humans:

• In humans the food is taken in through the mouth and it passes through a continuous canal starting at the buccal cavity and ending at the anus. 

• All the components of this canal together are termed as the alimentary canal or digestive tract. 

• The digestive tract along with the associated digestive glands are termed as digestive system. 

• The different components of the digestive tract and their role in the process of digestion is as follows:

1. Buccal cavity: 

• The buccal cavity is the mouth which contains the teeth, tongue and the palate. This is the beginning of the alimentary canal and thus digestion. The food enters the mouth and is mechanically ground by the different sets of teeth, like the incisors, canines, premolars and the molars. 

• The salivary glands present here secrete the clear liquid, saliva, that helps in lubricating the food.

• The saliva is mixed with the food by the tongue, which has the taste buds for detecting the various tastes. 

• This turns the chewed food into a ball called a bolus, which travels down the alimentary canal for further digestion.

2. Oesophagus or the food pipe:

• The partly digested food moves along the oesophagus.

• The wall of the oesophagus propels the food forward and downwards towards the stomach. 

• Any food that is not accepted by our body is pushed back through the mouth and is known as vomiting.

3. Stomach:

• The food from the oesophagus is pushed into the stomach, which is a J-shaped thick-walled bag, being the widest part of the alimentary canal. 

• The inner wall of the stomach secretes mucus, which protects the stomach lining, hydrochloric acid, which destroys most of the bacteria in the food, helping the digestive juices to act upon the food. 

• The stomach also secretes digestive juices that break down the proteins to simple substances.

4. Small intestine:

• Now the partially digested food enters the small intestine, which is a coiled structure, about 7.5 metres in length. 

• It has secretions from liver, bile, that acts on the fats and secretions from pancreas, pancreatic juice that acts on carbohydrates, proteins. 

• At the end of the small intestine, intestinal juice completes the process of digestion of food, and carbohydrates are broken into glucose, fats into fatty acids and proteins into amino acids. 

• This digested food is then absorbed by the intestinal walls, by the finger-like projections called villi, present in them. These absorbed substances are then transported to the various organs of the body through blood vessels. 

• Once they are in the cell, the glucose is converted to carbon dioxide and water with the release of energy.

5. Large intestine: 

• The undigested food is passed onto the large intestine, which is shorter and wider in comparison to the small intestine, measuring around 1.5 metres. 

• The water and salts are absorbed here and the remaining solid waste is passed into the rectum as faeces for egestion from the anus.

Digestion in Grass-Eating Animals:

• Many animals that eat grass like cows, buffaloes etc eat the grass quickly and store it in a special part of their stomach which is called as rumen. 

• The food is partially digested here and that is known as cud. After some time this cud comes into the mouth, and this makes the animal chew it gradually. This process is known as rumination and these animals that exhibit this are known as ruminants. 

• These grass eating animals, like cattle the bacteria present in their rumen helps digest the cellulose of the grass.

• Some animals like horse, rabbit etc, have a large sac-structure, Caecum, which is located between the oesophagus and small intestine for digesting the cellulose.

Feeding and Digestion in Amoeba:

• Amoeba is a single celled microscopic organism that keeps changing its shape constantly with the help of their finger-like projections, pseudopodia. 

• It captures the food with this and engulfs it and the food gets trapped in a food vacuole.

• Digestive juices are secreted into this that break down the food to simple substances for absorption to help it grow and maintain itself.

Important Topics of Class 7 Chapter 2 Science You Shouldn’t Miss!

• Photosynthesis: Understanding the process by which plants make their own food using sunlight, water, and carbon dioxide.

• Types of Nutrition in Animals: Learn about autotrophic and heterotrophic nutrition and how plants obtain nutrients.

• Role of Chlorophyll: Discover the importance of chlorophyll in photosynthesis and its role in giving plants their green colour.

• Nutrients Required by Plants: Study the essential nutrients that plants need for growth and how they absorb these from the soil.

• Symbiotic Relationships: Explore how some plants form symbiotic relationships to obtain nutrients, such as in the case of legumes and nitrogen-fixing bacteria.

Importance of Chapter 2 Nutrition in Animals Class 7 Notes

• The Chapter 2 Nutrition in Animals Class 7 Notes are crucial for students as they provide a clear understanding of how animals, including humans, process and utilize food.

• These notes simplify complex topics like the human digestive system, different types of animal nutrition, and the importance of various nutrients.

• By studying these notes, students can grasp the fundamental processes that keep animals healthy and functioning.

• They also serve as an excellent resource for exam preparation, ensuring that students can confidently answer questions on these topics.

Tips for Learning the Class 7 Science Chapter 2 Nutrition in Animals

• Human Digestive System: Learn the steps of digestion, including the role of the mouth, stomach, intestines, and associated organs.

• Modes of Nutrition in Animals: Understand the different ways animals obtain their food, such as herbivorous, carnivorous, and omnivorous diets.

• Role of Nutrients: Study the importance of carbohydrates, proteins, fats, vitamins, and minerals in maintaining animal health.

• Digestion in Ruminants: Explore the unique digestion process in animals like cows and buffaloes, including the function of the rumen.

• Amoeba's Mode of Nutrition: Discover how simple organisms like amoeba digest food through a process called phagocytosis.

Conclusion

Chapter 2 of Class 7 Science, Nutrition in Animals, is fundamental for understanding how plants produce their food and sustain life on Earth. By learning about photosynthesis, different types of plant nutrition, and the role of nutrients, students gain a strong foundation in biology. These concepts are not only important for exams, but also for appreciating the vital processes that support life in our environment. With the help of these notes, students can confidently grasp these topics and apply their knowledge in future studies.

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