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.
Also Check – Nutrition in Animals – Definition and Explanation of Important Keywords
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)
