Life Processes in Animals

Given: The alimentary canal is the pathway through which food travels during digestion.

Concept: The alimentary canal consists of the mouth, oesophagus, stomach, small intestine, large intestine, and anus, in that order.

Answer:

$$\text{Food} \rightarrow \text{Mouth} \rightarrow \textbf{Oesophagus} \rightarrow \text{Stomach} \rightarrow \textbf{Small Intestine} \rightarrow \textbf{Large Intestine} \rightarrow \text{Anus}$$

Explanation of each part:
- Oesophagus: A muscular tube that carries food from the mouth to the stomach.
- Small Intestine: Where most of the digestion and absorption of nutrients takes place.
- Large Intestine: Absorbs most of the remaining water and some salts from undigested food before it is expelled.

Given:
- Test tube A: Pieces of chapati + iodine solution
- Test tube B: Chewed chapati + iodine solution
- Test tube C: Boiled and mashed potato + iodine solution

Concept: Iodine solution turns blue-black in the presence of starch. If starch has been broken down into sugar (by saliva), iodine will NOT turn blue-black.

Observations and Reasons:

| Test Tube | Observation | Reason |
|-----------|-------------|--------|
| A (Chapati pieces) | Iodine turns blue-black | Chapati contains starch. Since it has not been chewed, starch is still present and reacts with iodine. |
| B (Chewed chapati) | Iodine does NOT turn blue-black (remains orange-brown) | During chewing, saliva mixes with the chapati. Saliva contains a digestive enzyme (salivary amylase) that breaks down starch into sugar. So, little or no starch remains to react with iodine. |
| C (Boiled and mashed potato) | Iodine turns blue-black | Potato contains starch. Boiling and mashing do not break down starch chemically, so starch is still present and reacts with iodine. |

Conclusion: Saliva breaks down starch into simpler sugars, which is why chewed chapati does not give a blue-black colour with iodine.

Correct Option: (iii) To help in inhalation and exhalation

Justification: The diaphragm is a dome-shaped muscle located below the lungs. During inhalation, the diaphragm moves downwards, increasing the space inside the chest cavity so that air enters the lungs. During exhalation, the diaphragm moves upwards, reducing the space and pushing air out of the lungs. Thus, the diaphragm plays a key role in the physical process of breathing (inhalation and exhalation).

Concept: Each part of the respiratory system has a specific function.

Correct Matching:

| Name of the Part | Function |
|------------------|----------|
| (i) Nostrils | (a) fresh air from outside enters |
| (ii) Nasal passages | (d) tiny hair and mucus help to trap dust and dirt from the air we breathe |
| (iii) Windpipe | (e) air reaches our lungs through this part |
| (iv) Alveoli | (b) exchange of gases occurs |
| (v) Ribcage | (c) protects lungs |

Brief Explanation:
- Nostrils: The openings through which fresh air from outside enters the body.
- Nasal passages: Lined with tiny hairs and mucus that filter dust and dirt from inhaled air.
- Windpipe (Trachea): The tube through which air travels from the nose/mouth to the lungs.
- Alveoli: Tiny air sacs in the lungs where exchange of oxygen and carbon dioxide between air and blood takes place.
- Ribcage: A bony structure that surrounds and protects the lungs.

Given: Anil incorrectly believes that breathing and respiration are the same process.

Concept: Breathing is a physical process, while respiration is a chemical process. They are related but not the same.

Questions Sanvi can ask Anil:

1. *"If breathing and respiration are the same, then where exactly does the energy come from that our body uses to do work? Does just moving air in and out of the lungs produce energy?"*
- This makes Anil think: Breathing only moves air; it does not produce energy. Respiration is the chemical process inside cells that breaks down glucose using oxygen to release energy.

2. *"Breathing happens in the lungs, but do our muscle cells or brain cells also 'breathe'? If not, how do they get energy?"*
- This highlights that respiration occurs in every cell of the body, not just in the lungs.

3. *"Is breathing a physical process or a chemical process? And what about respiration?"*
- Breathing = physical process (movement of air in and out of lungs). Respiration = chemical process (breakdown of glucose into $CO_2$ and water with release of energy).

Key Difference to explain:
- Breathing: Physical process — inhalation and exhalation of air through lungs.
- Respiration: Chemical process — $\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon dioxide} + \text{Water} + \text{Energy}$, occurring in every cell of the body.