Activity 2.1: Identifying Types of Teeth

Aim/Objective: To observe and identify the different types of human teeth and their functions.

Materials Required:

• A mirror.
• Index finger.
• An apple or a piece of bread (optional).

Procedure:

1. Use a mirror to look at your teeth.
2. Count the number of teeth in your upper and lower jaws.
3. Feel the surface of your teeth with your index finger.
4. Try to identify which teeth are used for:
   • Biting and cutting.
   • Piercing and tearing.
   • Chewing and grinding.
5. If you have a piece of food, observe which teeth you use for each of these actions.

Observation:

• The front teeth are flat and sharp (Incisors).
• The teeth next to the front ones are pointed (Canines).
• The teeth further back are flatter and broader (Premolars and Molars).

Explanation:

• Humans are heterodonts, meaning they have different types of teeth for different functions:
  • Incisors (8): Used for biting and cutting food.
  • Canines (4): Sharp and pointed for piercing and tearing food.
  • Premolars (8) and Molars (12): Large, flat surfaces for grinding and crushing food into smaller particles.
• This dental diversity is an adaptation to our omnivorous diet, allowing us to process both plant and animal-based foods efficiently.

Conclusion:

• Humans have specialized teeth categorized as incisors, canines, premolars, and molars, each designed for specific mechanical breakdown of food.

Activity 2.2: The Effect of Saliva on Starch

Aim/Objective: To demonstrate that saliva breaks down starch into simpler sugars.

Materials Required:

• Two test tubes (Label them A and B).
• Boiled rice.
• Iodine solution.
• Water.
• Dropper.

Procedure:

1. Put one teaspoon of boiled rice into test tube A.
2. Put one teaspoon of boiled rice that has been chewed for 3 to 5 minutes into test tube B.
3. Add 3–4 mL of water to both test tubes.
4. Add 2-3 drops of iodine solution to each test tube and observe the color change.

Observation:

• Test tube A (with only boiled rice) turns blue-black upon adding iodine.
• Test tube B (with chewed rice) does not turn blue-black; it remains a yellowish-brown color.

Explanation:

• Rice is rich in starch. Starch reacts with iodine to produce a characteristic blue-black color.
• Saliva contains an enzyme called salivary amylase (ptyalin).
• When rice is chewed, salivary amylase breaks down the complex starch into simpler sugars like maltose.
• Since the starch in test tube B has already been digested by the enzyme in the saliva, it no longer reacts with the iodine to produce a blue-black color.

Conclusion:

• Saliva initiates the digestion of starch by converting it into simpler sugars.