Rapid Revision – Class 7 Science -Chapter 2 – Nutrition in Animals – Complete Notes

Animal Nutrition-

• Animals cannot perform photosynthesis and must acquire food externally.
• Their food sources include direct consumption of plants or indirectly through other animals that have consumed plants.

Importance of Food-

• Essential for growth, tissue repair, and energy for bodily functions.
• Understanding animal nutrition involves studying nutrient requirements, food ingestion, and utilisation in the body.

Also Check – Chapter 2 – NUTRITION IN ANIMALS -Class 7 – Detailed Notes

Components of Food-

• Consists of carbohydrates, proteins, fats, vitamins, minerals, and water.
• Each component plays a specific role in health and well-being.
• Carbohydrates are the primary energy source; proteins are vital for growth and repair; fats provide concentrated energy; vitamins and minerals are crucial for biochemical reactions; water is essential for various bodily functions.

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Digestion of Complex Substances-

• Complex food components like carbohydrates are broken down into simpler substances through digestion.
• This involves enzymes and chemical reactions in the digestive system, allowing nutrient extraction and conversion into usable forms.

Different Ways of Taking Food–

• Varies among organisms based on specific adaptations (e.g., bees feeding on nectar, infants on milk, snakes swallowing prey whole, aquatic animals filtering food particles).

Also Check – Chapter 2 – Nutrition in Animals Textbook Exercise -(Solved)

Digestion in Humans-

• Ingestion begins in the mouth with mechanical and chemical digestion.
• The oesophagus transports food to the stomach where gastric juices break down proteins.
• The small intestine continues digestion with enzymes from the pancreas and bile from the liver, leading to nutrient absorption.
• The large intestine absorbs water and minerals, forming faeces.
• The rectum stores faeces until elimination through the anus.
• Nutrients absorbed are used by cells for energy.

Also Check – Class 7- Chapter 2 – Nutrition in Animals – 4 Worksheets Solved and Unsolved

The Mouth and Buccal Cavity-

• Serves as the entry point for food (ingestion).
• Mechanical digestion begins here through chewing, breaking food into smaller pieces.
• Diverse teeth types (incisors, canines, premolars, molars) for various functions like biting, tearing, and grinding.
• Each tooth is anchored in its own socket within the gums.

Teeth and Their Functions-

• Incisors– Flat, sharp-edged front teeth for cutting and biting.
• Canines- Pointed, sharp teeth behind incisors for tearing food.
• Premolars- Flat-surfaced teeth behind canines for grinding and crushing.
• Molars- Large, flat teeth at the back for grinding tough or fibrous foods.

Also Check – Activity -Arrangement of teeth and different type of teeth

Role of Teeth in Digestion-

• Mechanical Digestion- Teeth increase the surface area of food for enzymatic action.
• Chemical Digestion- Food mixes with saliva containing enzymes (like amylase) for carbohydrate breakdown.

Saliva and Salivary Glands-

• Saliva moistens food, easing chewing and swallowing.
• Contains enzymes for the initial breakdown of carbohydrates.

Also Check – Activity – Effect of saliva on starch – Class 7

Tongue and Taste Buds-

• The tongue aids in mixing food with saliva and swallowing.
• Contains taste buds for detecting different tastes.

Milk Teeth and Permanent Teeth-

• Milk teeth (primary teeth) emerge from infancy, aiding early food consumption.
• Replaced by permanent teeth, which should last a lifetime.
• Dental care and hygiene are crucial for maintaining oral health.

Tooth Decay and its Causes-

• Caused by harmful bacteria interacting with sugars, producing acids.
• Acids erode enamel, leading to cavities.
• Prevention includes good oral hygiene, limited sugar intake, and regular dental check-ups.

Swallowing Mechanism and Prevention of Choking-

• Food enters the windpipe (trachea) risk during eating/drinking.
• Epiglottis, a flap-like valve, closes off the windpipe during swallowing.
• Food and liquids are directed into the oesophagus, not the windpipe.
• Coughing, hiccups, or a choking sensation occur if food enters the windpipe, to expel foreign material.

Digestive Process in the Oesophagus and Stomach-

The Oesophagus-

• Muscular tube connecting mouth to stomach.
• Peristalsis moves food smoothly to the stomach.

Vomiting Reflex-

• Expels stomach contents via the oesophagus due to triggers like spoiled food or overeating.

The Stomach-

• Muscular, J-shaped organ between oesophagus and small intestine.
• Secretes mucus, hydrochloric acid, and digestive juices.
• Begins protein digestion with enzymes like pepsin.

The Small Intestine and its Role in Digestion-

Structure-

• Long, coiled tube (~7.5 metres).
• Lined with villi for increased nutrient absorption surface area.

Digestive Secretions-

• Receives bile from the liver (stored in the gallbladder) for fat digestion.
• Receives pancreatic juice from the pancreas for carbohydrate, fat, and protein digestion.

Digestive Process-

• Continues breakdown of carbohydrates into simple sugars.
• Breaks down fats into fatty acids and glycerol.
• Proteins into amino acids for nutrient absorption.

Absorption in the Small Intestine-

• Post-digestion, food components are absorbed in the small intestine.
• Villi lining the small intestine increases surface area for efficient absorption.
• Villi contain capillaries, facilitating absorption of nutrients like glucose, amino acids, fatty acids into the bloodstream.
• These nutrients are used for building complex substances and various bodily functions.

Assimilation and Energy Production-

• Absorbed glucose undergoes metabolic breakdown with oxygen, forming carbon dioxide and water.
• This process releases energy for growth, repair, and maintenance.

Role of the Large Intestine (Colon)-

• Absorbs water and salts from undigested food.
• Waste material becomes semi-solid (faeces) and stored in the rectum.
• Faeces are eliminated from the body through egestion.

Digestion in Grass-Eating Animals (Ruminants)-

• Specialised digestive system for extracting nutrients from cellulose-rich plants.
• Quick swallowing of grass, storing in the rumen for partial digestion (cud).
• Rumination involves regurgitating and chewing cud to break down cellulose.
• Rumen bacteria assist in cellulose digestion.

Also Check- Chewing the Cud- The Ruminant Digestive System

Caecum in Some Animals-

• Animals like horses and rabbits have a caecum for cellulose digestion.
• Bacteria in the caecum aid in breaking down cellulose.

Feeding and Digestion in Amoeba-

• Amoeba engulfs food using pseudopodia, forming a food vacuole.
• Digestive juices break down food into simpler substances.
• Absorbed nutrients used for growth and maintenance; undigested residue expelled.

Starfish Feeding Method-

• Starfish feed on shell-protected animals like mollusks.
• Uses tube feet and arms to open prey’s shell.
• Extrudes stomach into the shell, digesting prey’s soft tissues.
• Retracts the stomach, leaving indigestible parts.

Also Check – Chapter 2- Nutrition in Animals Class 7 Worksheet – Fill in the Blanks

Also check – Chapter 2- Nutrition in Animals Class 7 Worksheet – Multiple-Choice Questions (MCQs)

Also Check – Chapter 2- NUTRITION IN ANIMALS -Class 7 Question and Answer (Long)

Also Check – Chapter 2- NUTRITION IN ANIMALS -Class 7 Question and Answer (Short)