Activities

Activity 1: Action of Saliva on Starch

Aim: To investigate how saliva breaks down starch in food.

Materials:

2x Glass test tubes (labeled A and B).
10g Freshly boiled rice (divided into two portions).
10 mL Distilled water (5 mL for each tube).
1x Dropper bottle of Iodine solution (0.01 N).

Procedure:

Place 5g of boiled rice directly into test tube A.
Take the other 5g of boiled rice and chew it thoroughly for exactly 2 minutes in your mouth. Transfer this chewed rice to test tube B.
Add 5 mL of water to both test tubes and shake them gently for 30 seconds.
Allow both tubes to stand for 10 minutes to allow the enzyme action to complete.
Add 2-3 drops of iodine solution to each tube and observe the colour change immediately.

Saliva contains an enzyme called Salivary Amylase (also known as ptyalin). It acts on complex starch molecules and breaks them down into simpler sugars like maltose. Iodine reacts with starch to form a blue-black complex, but it does not react with simple sugars.

For hygiene reasons, ensure that the person chewing the rice only uses their own test tube (Tube B). Wash hands thoroughly before and after handling test tubes and rice.

If the rice is too dry, it may be hard to transfer after chewing. Make sure the boiled rice is moist to facilitate easy transfer and better mixing with saliva.

Observation:

Test tube A: Turns deep blue-black (indicating presence of starch).
Test tube B: Remains the colour of iodine or turns pale yellow (indicating starch has been digested).

Conclusion: Saliva contains enzymes that begin the process of chemical digestion by breaking down starch into sugars in the mouth.

Activity 2: Model of the Breathing Mechanism

Aim: To demonstrate how the movement of the diaphragm affects the lungs.

Materials:

1x Transparent 2L plastic bottle (with bottom removed).
1x Y-shaped glass or plastic tube.
2x Small balloons (to represent lungs).
1x Large balloon or thin rubber sheet (to represent the diaphragm).
Modeling clay or a rubber cork (to seal the bottle neck).

Procedure:

Preparation: Cut off the bottom of the 2L bottle. Bore a hole in the lid or use a cork with a hole.
Assembly: Tie the two small balloons to the forked ends of the Y-tube. Insert the straight end of the Y-tube through the lid and seal the entry point with clay to make it completely air-tight.
The Diaphragm: Cut the large balloon in half and stretch it tightly across the open bottom of the bottle. Secure it with a rubber band or strong tape.
Inhalation Simulation: Gently pull the rubber sheet (diaphragm) downwards and hold for 5 seconds. Observe the balloons.
Exhalation Simulation: Push the rubber sheet upwards into the bottle and hold for 5 seconds. Observe the balloons.

This model demonstrates Boyle's Law. When the diaphragm moves down, the volume of the chest cavity increases, the internal pressure drops (negative pressure), and air rushes into the lungs (balloons) to equalize the pressure.

Be careful when cutting the plastic bottle. The edges can be sharp; you may use sandpaper or tape to smooth the cut edge.

If the balloons don't inflate, check the seal at the bottle neck and the rubber sheet at the bottom. Even a tiny air leak will prevent the pressure difference from forming.

Observation:

Pulling down (Inhalation): The volume inside the bottle increases, and the balloons inflate.
Releasing up (Exhalation): The volume inside the bottle decreases, and the balloons deflate.

Conclusion: The balloons represent the lungs and the rubber sheet represents the diaphragm. Its movement changes the pressure inside the chest cavity, driving the mechanism of breathing.

Activity 3: What do we breathe out?

Aim: To prove that exhaled air is rich in carbon dioxide compared to atmospheric air.

Materials:

20 mL Freshly prepared Lime water (Calcium hydroxide).
2x Test tubes (labeled A and B).
1x 50 mL Syringe (pichkari).
1x Clean plastic straw.

Procedure:

Fill test tubes A and B with 10 mL of clear lime water each.
Control (Tube A): Use the syringe to pump atmospheric air into the lime water in tube A. Perform 20 full pumps.
Test (Tube B): Use the straw to gently blow exhaled air into tube B. Blow for about 15-20 seconds (approx. 3-4 deep exhales).
Compare the time or number of breaths required for the lime water to turn milky in both tubes.

Carbon dioxide reacts with Lime water to form Calcium Carbonate ( $CaCO_3$ ), which is insoluble in water and appears as a milky white precipitate.

Do not blow too hard into the test tube as it may cause the lime water to splash out. Lime water is basic and can irritate the eyes.

If you have a stopwatch, record the exact number of seconds it takes for Tube B to turn cloudy. It usually takes less than 30 seconds of gentle blowing.

Observation: The lime water in test tube B (exhaled air) turns milky almost immediately, whereas the lime water in test tube A (atmospheric air) remains clear or takes much longer to show any turbidity.

Conclusion: Exhaled air contains a significantly higher concentration of carbon dioxide than the surrounding atmospheric air, confirming it as a byproduct of respiration.

Activity 4: Researching Animal Breathing Organs

Aim: To explore different structures used for gas exchange in various habitats.

Procedure:

Create a detailed table with columns: Animal Name, Habitat, Respiratory Organ, and Mechanism.
Research and document the following specific examples:
- Fish: Gills (Counter-current exchange to extract $O_2$ from water).
- Frogs: Lungs (on land), moist Skin (in water), and buccal cavity.
- Earthworms: Moist Skin (cuticular respiration via diffusion).
- Insects: Spiracles and Tracheal tubes (direct air delivery to tissues).
- Birds/Mammals: Lungs (Alveolar structure for high surface area).

Regardless of the organ, all respiratory surfaces share three common features: they are thin-walled, they have a large surface area, and they are kept moist to facilitate the diffusion of gases.

When researching, look for "Scanning Electron Microscope" (SEM) images of these organs. Seeing the intricate branching of insect tracheae or fish gill lamellae makes the concept of "increased surface area" much clearer.

Conclusion: Animals have evolved highly specialized respiratory structures that are specifically adapted to the physical properties of their environment (aquatic vs. terrestrial) and their metabolic demands.

Activities

Activity 1: Action of Saliva on Starch

Aim: To investigate how saliva breaks down starch in food.

Materials:

2x Glass test tubes (labeled A and B).
10g Freshly boiled rice (divided into two portions).
10 mL Distilled water (5 mL for each tube).
1x Dropper bottle of Iodine solution (0.01 N).

Procedure:

Place 5g of boiled rice directly into test tube A.
Take the other 5g of boiled rice and chew it thoroughly for exactly 2 minutes in your mouth. Transfer this chewed rice to test tube B.
Add 5 mL of water to both test tubes and shake them gently for 30 seconds.
Allow both tubes to stand for 10 minutes to allow the enzyme action to complete.
Add 2-3 drops of iodine solution to each tube and observe the colour change immediately.

For hygiene reasons, ensure that the person chewing the rice only uses their own test tube (Tube B). Wash hands thoroughly before and after handling test tubes and rice.

If the rice is too dry, it may be hard to transfer after chewing. Make sure the boiled rice is moist to facilitate easy transfer and better mixing with saliva.

Observation:

Test tube A: Turns deep blue-black (indicating presence of starch).
Test tube B: Remains the colour of iodine or turns pale yellow (indicating starch has been digested).

Conclusion: Saliva contains enzymes that begin the process of chemical digestion by breaking down starch into sugars in the mouth.

Activity 2: Model of the Breathing Mechanism

Aim: To demonstrate how the movement of the diaphragm affects the lungs.

Materials:

1x Transparent 2L plastic bottle (with bottom removed).
1x Y-shaped glass or plastic tube.
2x Small balloons (to represent lungs).
1x Large balloon or thin rubber sheet (to represent the diaphragm).
Modeling clay or a rubber cork (to seal the bottle neck).

Procedure:

Preparation: Cut off the bottom of the 2L bottle. Bore a hole in the lid or use a cork with a hole.
Assembly: Tie the two small balloons to the forked ends of the Y-tube. Insert the straight end of the Y-tube through the lid and seal the entry point with clay to make it completely air-tight.
The Diaphragm: Cut the large balloon in half and stretch it tightly across the open bottom of the bottle. Secure it with a rubber band or strong tape.
Inhalation Simulation: Gently pull the rubber sheet (diaphragm) downwards and hold for 5 seconds. Observe the balloons.
Exhalation Simulation: Push the rubber sheet upwards into the bottle and hold for 5 seconds. Observe the balloons.

Be careful when cutting the plastic bottle. The edges can be sharp; you may use sandpaper or tape to smooth the cut edge.

If the balloons don't inflate, check the seal at the bottle neck and the rubber sheet at the bottom. Even a tiny air leak will prevent the pressure difference from forming.

Observation:

Pulling down (Inhalation): The volume inside the bottle increases, and the balloons inflate.
Releasing up (Exhalation): The volume inside the bottle decreases, and the balloons deflate.

Conclusion: The balloons represent the lungs and the rubber sheet represents the diaphragm. Its movement changes the pressure inside the chest cavity, driving the mechanism of breathing.

Activity 3: What do we breathe out?

Aim: To prove that exhaled air is rich in carbon dioxide compared to atmospheric air.

Materials:

20 mL Freshly prepared Lime water (Calcium hydroxide).
2x Test tubes (labeled A and B).
1x 50 mL Syringe (pichkari).
1x Clean plastic straw.

Procedure:

Fill test tubes A and B with 10 mL of clear lime water each.
Control (Tube A): Use the syringe to pump atmospheric air into the lime water in tube A. Perform 20 full pumps.
Test (Tube B): Use the straw to gently blow exhaled air into tube B. Blow for about 15-20 seconds (approx. 3-4 deep exhales).
Compare the time or number of breaths required for the lime water to turn milky in both tubes.

Carbon dioxide reacts with Lime water to form Calcium Carbonate ( $CaCO_3$ ), which is insoluble in water and appears as a milky white precipitate.

Do not blow too hard into the test tube as it may cause the lime water to splash out. Lime water is basic and can irritate the eyes.

If you have a stopwatch, record the exact number of seconds it takes for Tube B to turn cloudy. It usually takes less than 30 seconds of gentle blowing.

Conclusion: Exhaled air contains a significantly higher concentration of carbon dioxide than the surrounding atmospheric air, confirming it as a byproduct of respiration.

Activity 4: Researching Animal Breathing Organs

Aim: To explore different structures used for gas exchange in various habitats.

Procedure:

Create a detailed table with columns: Animal Name, Habitat, Respiratory Organ, and Mechanism.
Research and document the following specific examples:
- Fish: Gills (Counter-current exchange to extract $O_2$ from water).
- Frogs: Lungs (on land), moist Skin (in water), and buccal cavity.
- Earthworms: Moist Skin (cuticular respiration via diffusion).
- Insects: Spiracles and Tracheal tubes (direct air delivery to tissues).
- Birds/Mammals: Lungs (Alveolar structure for high surface area).

Regardless of the organ, all respiratory surfaces share three common features: they are thin-walled, they have a large surface area, and they are kept moist to facilitate the diffusion of gases.

Life Processes in Animals - Activities

Activities

Activity 1: Action of Saliva on Starch

Activity 2: Model of the Breathing Mechanism

Activity 3: What do we breathe out?

Activity 4: Researching Animal Breathing Organs

On this page

Life Processes in Animals - Activities

Activities

Activity 1: Action of Saliva on Starch

Activity 2: Model of the Breathing Mechanism

Activity 3: What do we breathe out?

Activity 4: Researching Animal Breathing Organs

On this page