Nutrition in Animals Ncert Notes

Introduction to Nutrition in Animals

Nutrition in Animals- Nutrition is the process by which living organisms obtain and utilize food to sustain life, growth, and energy. Animals, unlike plants, cannot produce their own food and depend on other organisms for nutrition. This chapter explores how animals obtain and digest food, the different modes of nutrition in animals, and the digestive systems of various organisms, with a special focus on humans.

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1. Modes of Nutrition in Animals

Animals exhibit different ways of feeding based on their food habits and habitats. These modes include:

• Herbivores: Animals that eat only plants (e.g., cows, goats). They have specialized teeth and digestive systems to break down plant material.
• Carnivores: Animals that eat other animals (e.g., lions, tigers). They have sharp teeth and claws for hunting and tearing flesh.
• Omnivores: Animals that eat both plants and animals (e.g., humans, bears). They have a mix of teeth suited for grinding plants and tearing meat.
• Parasites: Organisms that live on or inside a host and derive nutrition from it (e.g., tapeworms, lice).
• Saprophytes: Organisms that feed on dead and decaying matter (though more common in fungi, some animals like vultures scavenge dead remains).

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2. The Process of Nutrition

Nutrition in animals involves five key steps:

1. Ingestion: The intake of food into the body (e.g., eating or swallowing).
2. Digestion: The breakdown of complex food into simpler, absorbable forms.
3. Absorption: The process of taking digested nutrients into the bloodstream.
4. Assimilation: The utilization of absorbed nutrients by cells for energy, growth, and repair.
5. Egestion: The removal of undigested waste from the body.

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3. Digestion in Humans

The human digestive system is a well-organized structure designed to process food efficiently. It consists of the alimentary canal (a long tube) and associated glands.

The Alimentary Canal

The alimentary canal includes:

• Mouth: The entry point of food where digestion begins.
• Oesophagus (Food Pipe): A tube that carries food from the mouth to the stomach.
• Stomach: A muscular bag where food is churned and mixed with digestive juices.
• Small Intestine: A long, coiled tube where most digestion and absorption occur.
• Large Intestine: Absorbs water from undigested food and forms faeces.
• Rectum and Anus: Store and expel faeces from the body.

Digestive Glands

These glands secrete juices that aid digestion:

• Salivary Glands: Located in the mouth, they secrete saliva containing the enzyme amylase (or ptyalin) to break down starch into sugar.
• Liver: Produces bile, stored in the gallbladder, which helps digest fats.
• Pancreas: Secretes pancreatic juice containing enzymes like trypsin (for proteins), lipase (for fats), and amylase (for starch).
• Gastric Glands: In the stomach, secrete gastric juice with hydrochloric acid, pepsin (for proteins), and mucus.
• Intestinal Glands: In the small intestine, secrete intestinal juice to complete digestion.

Process of Digestion in Humans

1. Mouth: Food is chewed by teeth, mixed with saliva, and partially digested (starch → sugar). The tongue helps in tasting and pushing food to the oesophagus.
2. Oesophagus: Food moves down via peristalsis (wave-like muscle contractions).
3. Stomach: Gastric juices break down proteins into simpler substances. The acidic environment kills harmful bacteria.
4. Small Intestine: Bile from the liver emulsifies fats, while pancreatic and intestinal juices complete digestion of carbohydrates, proteins, and fats. Nutrients are absorbed through villi (tiny finger-like projections).
5. Large Intestine: Absorbs water and forms solid waste (faeces).
6. Anus: Faeces are expelled from the body.

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4. Teeth and Their Role

Teeth play a crucial role in ingestion and digestion. Humans have two sets of teeth in their lifetime:

• Milk Teeth: Temporary teeth in children (20 in number).
• Permanent Teeth: Replace milk teeth in adults (32 in number).

Types of Teeth

• Incisors: Front teeth for cutting and biting (8 in total).
• Canines: Sharp, pointed teeth for tearing food (4 in total).
• Premolars: For crushing and grinding (8 in total).
• Molars: Larger teeth for grinding food (12 in total).

Dental hygiene is essential to prevent cavities caused by bacteria acting on food particles.

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5. Digestion in Other Animals

Different animals have digestive systems adapted to their diet and lifestyle.

Digestion in Grass-Eating Animals (Ruminants)

• Examples: Cows, goats, sheep.
• Ruminants have a four-chambered stomach: rumen, reticulum, omasum, abomasum.
• Process:
  1. Grass is swallowed and stored in the rumen, where bacteria partially digest cellulose (a complex carbohydrate in plants).
  2. The food is regurgitated as cud, chewed again, and sent to other chambers.
  3. Digestion is completed in the abomasum (true stomach), and nutrients are absorbed in the intestines.
• This process is called rumination.

Digestion in Amoeba

• Amoeba is a single-celled organism that uses pseudopodia (false feet) to engulf food.
• Process:
  1. Food is surrounded by pseudopodia, forming a food vacuole.
  2. Digestive enzymes break down the food inside the vacuole.
  3. Nutrients are absorbed into the cytoplasm, and waste is expelled by diffusion through the body surface.
• This is an example of intracellular digestion (digestion inside the cell).

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6. Key Terms and Concepts

• Enzymes: Biological catalysts that speed up digestion (e.g., amylase, pepsin, lipase).
• Peristalsis: Rhythmic muscle contractions that push food through the digestive tract.
• Villi: Tiny projections in the small intestine that increase surface area for absorption.
• Rumination: Chewing cud by ruminants to digest tough plant material.
• Egestion: Removal of undigested waste, distinct from excretion (removal of metabolic waste like urine).

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7. Importance of Nutrition

• Provides energy for daily activities.
• Supplies raw materials for growth and repair of tissues.
• Helps maintain body functions like respiration, circulation, and immunity.

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8. Interesting Facts

• The human small intestine is about 6 meters long when stretched out!
• Cows can spend up to 8 hours a day chewing cud.
• Amoeba has no mouth or stomach, yet it efficiently digests food.

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Conclusion

Chapter 2 of Class 7 Science introduces students to the fascinating world of animal nutrition. From the complex human digestive system to the unique adaptations in ruminants and single-celled organisms like Amoeba, the chapter highlights how diverse feeding mechanisms support life. Understanding these processes helps us appreciate the role of nutrition in survival and the interdependence of organisms in nature.

Ch 2 Nutrition In Animals