By Subhash Kumar | Science Educator | UREducator
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Nutrition in Animals
Complete Teaching Resource for CBSE Class 7 Science Chapter 2
Class: VII
Subject: Science
Chapter: 2
Duration: 4 Hours
What Students Will Achieve
Knowledge
- Understand different modes of animal nutrition
- Describe the human digestive system and its functions
- Identify the various types of teeth and their roles
- Explain the digestion process in ruminants and amoeba
Understanding
- Explain the journey of food through the digestive tract
- Analyze the role of different digestive juices
- Understand how different animals adapt their feeding methods
- Explain the importance of villi in nutrient absorption
Skills
- Create models of the digestive system
- Conduct experiments to demonstrate enzyme action
- Identify different types of teeth and their functions
- Compare human digestion with other animals
Prior Knowledge Assessment
Starter Questions:
- What are the main differences between plant and animal nutrition?
- Can you name the organs involved in human digestion?
- Why do cows chew continuously even when they're not eating?
The Digestive Process in Humans
Stages of Nutrition in Humans
Ingestion
Taking food into the mouth
- Teeth break down food mechanically
- Saliva begins chemical digestion
- Tongue helps in mixing and swallowing
Digestion
Breaking down complex food molecules
- Mechanical and chemical processes
- Involves multiple digestive juices
- Occurs throughout the alimentary canal
Absorption
Nutrients entering the bloodstream
- Mainly occurs in small intestine
- Villi increase surface area
- Water absorbed in large intestine
Assimilation
Using nutrients for body functions
- Nutrients transported to cells
- Used for energy, growth and repair
- Excess stored as fat or glycogen
Egestion
Removal of undigested waste
- Through the anus as feces
- Includes fiber and dead bacteria
- Important for removing toxins
Human Teeth and Their Functions
| Type | Number (Adult) | Shape | Function |
|---|---|---|---|
| Incisors | 8 (4 upper, 4 lower) | Chisel-shaped | Cutting and biting food |
| Canines | 4 (2 upper, 2 lower) | Pointed | Tearing and piercing food |
| Premolars | 8 (4 upper, 4 lower) | Two cusps | Crushing and grinding |
| Molars | 12 (6 upper, 6 lower) | Four or five cusps | Chewing and grinding |
Experiment: Testing for Starch Digestion
Objective: Demonstrate the action of salivary amylase on starch
- Take two test tubes labeled A and B
- Put boiled rice in both tubes (chewed in tube B)
- Add 3-4 mL water to each tube
- Add 2-3 drops of iodine solution
- Observe color changes (blue-black indicates starch)
- Note differences between the two tubes
Glands and Their Secretions
Major Digestive Glands
Salivary Glands
- Location: Near the mouth
- Secretion: Saliva (1-1.5L/day)
- Enzyme: Salivary amylase (ptyalin)
- Function: Begins starch digestion
Gastric Glands
- Location: Stomach lining
- Secretion: Gastric juice (2-3L/day)
- Components: HCl, pepsin, mucus
- Function: Protein digestion
Liver
- Largest gland in the body
- Secretion: Bile (500-1000mL/day)
- Function: Emulsifies fats
- Storage: Gallbladder
Pancreas
- Location: Behind stomach
- Secretion: Pancreatic juice (1.2-1.5L/day)
- Enzymes: Trypsin, lipase, amylase
- Function: Complete food digestion
Intestinal Glands
- Location: Small intestine wall
- Secretion: Intestinal juice (2-3L/day)
- Enzymes: Peptidases, disaccharidases
- Function: Final digestion
Digestive Juices and Their Actions
| Gland | Secretion | Enzymes | Substrate | Products |
|---|---|---|---|---|
| Salivary | Saliva | Amylase | Starch | Maltose |
| Gastric | Gastric juice | Pepsin | Proteins | Peptides |
| Pancreas | Pancreatic juice | Trypsin, Lipase, Amylase | Proteins, Fats, Starch | Amino acids, Fatty acids, Maltose |
| Intestinal | Intestinal juice | Peptidases, Disaccharidases | Peptides, Disaccharides | Amino acids, Monosaccharides |
Activity: Model of Digestive System
Objective: Create a working model showing digestion process
- Use different colored papers/clay for each organ
- Show the pathway from mouth to anus
- Include major glands and their secretions
- Label all parts with their functions
- Demonstrate how food changes at each stage
Nutrition in Different Animals
Modes of Animal Nutrition
Herbivores
Plant-eating animals
- Examples: Cow, deer, rabbit
- Special adaptations: Flat molars, long digestive tracts
- Some have symbiotic bacteria for cellulose digestion
Carnivores
Flesh-eating animals
- Examples: Lion, tiger, eagle
- Special adaptations: Sharp canines, short digestive tracts
- Strong stomach acids for meat digestion
Omnivores
Both plant and animal eaters
- Examples: Humans, bears, crows
- Special adaptations: Variety of tooth types
- Adaptable digestive systems
Parasites
Dependent on host
- Examples: Tapeworm, leech
- Special adaptations: Suckers, reduced digestive systems
- Absorb nutrients directly from host
Ruminant Digestion
| Compartment | Function | Process |
|---|---|---|
| Rumen | Fermentation vat | Bacteria break down cellulose, forms cud |
| Reticulum | Honeycomb filter | Separates large particles for regurgitation |
| Omasum | Water absorption | Removes water from digested material |
| Abomasum | True stomach | Gastric juices complete digestion |
Nutrition in Amoeba
Process of Nutrition
- Ingestion: Forms pseudopodia around food particle
- Digestion: Food vacuole forms, digestive enzymes secreted
- Absorption: Nutrients absorbed into cytoplasm
- Assimilation: Used for growth and energy
- Egestion: Undigested material expelled
Project: Comparing Animal Diets
Objective: Research and compare different animal digestive systems
- Select three animals with different diets (herbivore, carnivore, omnivore)
- Research their digestive systems and adaptations
- Create a comparison chart of their teeth, digestive tracts, and processes
- Present findings with diagrams to the class
Maintaining Digestive Health
Common Digestive Disorders
Tooth Decay
- Caused by bacterial action on sugars
- Produces acids that erode enamel
- Prevention: Regular brushing, flossing
- Avoid excessive sweets and soft drinks
Diarrhoea
- Frequent watery stools
- Causes: Infection, food poisoning
- Danger: Dehydration
- Treatment: ORS, medical attention
Acidity
- Excess stomach acid production
- Causes: Spicy food, stress, irregular meals
- Symptoms: Heartburn, nausea
- Prevention: Balanced diet, regular meals
Food Poisoning
- Caused by contaminated food
- Symptoms: Vomiting, abdominal pain
- Prevention: Food hygiene, clean water
- Treatment: Rest, fluids, medical care
Maintaining Digestive Health
| Practice | Benefit | Implementation |
|---|---|---|
| Balanced Diet | Provides all necessary nutrients | Include fruits, vegetables, grains, proteins |
| Adequate Water | Prevents constipation, aids digestion | Drink 8-10 glasses daily |
| Regular Meals | Maintains digestive rhythm | Eat at consistent times daily |
| Chewing Thoroughly | Eases digestion process | Chew each bite 20-30 times |
| Dental Hygiene | Prevents tooth decay and gum disease | Brush twice daily, floss regularly |
Activity: Creating ORS Solution
Objective: Learn to prepare Oral Rehydration Solution
- Take 1 liter of clean boiled water
- Add 6 teaspoons sugar
- Add 1/2 teaspoon salt
- Mix thoroughly until dissolved
- Discuss importance in diarrhea treatment
Evaluation Strategies
Formative Assessments
- Labeling diagrams of digestive system
- Quiz on digestive processes
- Experiment report evaluation
- Class participation in discussions
Summative Assessments
- Chapter test (MCQs + short answers)
- Project on comparative animal nutrition
- Practical exam on digestive experiments
- Case study analysis
Extended Learning: Visit to Dairy Farm
Objective: Observe ruminant digestion firsthand
- Interview farmers about cattle feeding practices
- Observe the process of rumination
- Learn about special feeds and supplements
- Compare human and ruminant digestion
- Prepare a report with photographs
Frequently Asked Questions
Why can't humans digest cellulose like cows can?
Humans lack the necessary enzymes and symbiotic bacteria to break down cellulose because:
- We don't produce cellulase enzyme required for cellulose digestion
- Our digestive systems lack the specialized chambers (like rumen) that house cellulose-digesting bacteria
- Our diets historically haven't required this adaptation as we eat more easily digestible plant parts
- The cellulose we consume acts as dietary fiber, aiding digestion rather than providing nutrients
What happens when food enters the windpipe instead of the foodpipe?
When food enters the windpipe (trachea):
- The body triggers a coughing reflex to expel the foreign material
- You may experience a choking sensation
- In severe cases, it can lead to aspiration pneumonia if not cleared
- The epiglottis normally prevents this by covering the trachea during swallowing
- This is why we shouldn't talk or laugh while eating
