Science 2 Marks Questions

When we inhale a lot of dust-laden air, the dust particles get trapped in the hair of our nasal cavity. These particles irritate the lining of the cavity. As a result, we sneeze to expel these dust particles. Sneezing expels these foreign particles from the inhaled air, and dust-free, clean air enters our bodies.

(i) To help in inhalation and exhalation. The diaphragm contracts and flattens during inhalation to allow the lungs to expand, and relaxes during exhalation to push air out.

It does not filter air or produce sound. Its main role is to help in the movement of air into and out of the lungs.

Rakshita is trying to inve stigate the gas we inhale and exhale while breathing. The lime water in test tube B turned milky (or cloudy), but the lime water in test tube A did not. Lime water turns milky when it reacts with carbon dioxide. Therefore, this indicates that the exhaled air contains more carbon dioxide than the air we inhaled.

Breathing is the physical process of inhaling and exhaling air.
Respiration is the chemical process of breaking down food to release energy.

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1.The small intestine has a large surface area due to villi and microvilli.
2.It is lined with blood vessels, which help in quick absorption of nutrients into the bloodstream.

The diaphragm flattens and the ribs are lifted to increase the volume of the chest cavity, which reduces pressure inside the lungs and allows air to flow in.

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(a) 1. Rumen 2. Pancreas
(b) Rumination

The pathway of air in the human respiratoiy system is given as:

(a) Snail, as it does not breathe through trachea.
(b) Earthworm, because unlike others earthworm breathes through its skin and does not have lungs.
(c) Fish, because unlike others most fishes breathe through their gills and do not have lungs.
(d) Tadpole, because unlike others tadpole breathes through gills and does not have lungs.

Passive smoking, also known as second¬hand smoking, happens when a non-smoker breathes in the smoke from someone else’s cigarette, cigar, or pipe. This smoke contains harmful chemicals, just like the smoke inhaled by the smoker.

The small intestine is a long, coiled tube (6 metres) where most of the digestion and absorption of food happens. Digestive juices from the liver (bile) and the pancreas (pancreatic juice) are mixed with the food in the small intestine. These juices help to break down fats, proteins, and carbohydrates into simpler forms. After digestion, the tiny finger¬like structures on the inner walls of the small intestine absorb the nutrients into the blood.

The process of breathing happens in two steps inhalation (breathing in) and exhalation (breathing out).
(i) When we inhale air, the diaphragm moves downwards and the chest cavity expands. This makes space for the lungs to fill with air. Air rushes in and fills the tiny air sacs in the lungs called alveoli.
(ii) When we exhale, the diaphragm moves upwards and the chest cavity becomes smaller. This pushes out the air containing carbon dioxide and water vapour from the lungs.

Ruminants quickly swallow the food and store it in an isolated part of the stomach called the rumen, where the food gets partially digested and is called cud, which later on returns to the mouth in the form of small lumps and then is chewed up by the animal. This process is called rumination.

Conclusion: This indicates that exhaled air contains carbon dioxide. Lime water reacts with carbon dioxide to form calcium carbonate, which causes the milky appearance. The change only in test tube B confirms that more carbon dioxide is present in the air we breathe out than in the air we breathe in.

Take a small piece of chewed rice in a test tube and add a few drops of iodine solution. The colour will not turn blue-black, showing that starch in the rice has been partially digested by saliva.

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The stomach and small intestine have to work harder to break down the larger food particles.This can lead to indigestion, bloating, and discomfort.Nutrient absorption may not be as efficient because the food isn't properly broken down.

At higher altitudes, the air pressure is lower. This means there are fewer oxygen molecules in each breath you take compared to what you'd get at sea level.Cold air can irritate your lungs and airways, causing them to constrict. This makes it harder to breathe deeply and get enough oxygen.So, when people are in hilly areas during winter, the combination of less oxygen in the air and the constricting effect of cold air on their lungs can lead to feelings of breathlessness.

Priya likely concluded that the air she exhaled contains carbon dioxide. Lime water turns milky when it reacts with carbon dioxide, so by blowing through the straw and observing this change, Priya determined that her breath contained a significant amount of carbon dioxide, a key byproduct of respiration.

I partially agree with Sahil. Stomach acid, or hydrochloric acid, is essential for digestion as it helps break down proteins and kills harmful bacteria. However, it can also be harmful because its corrosive nature can damage the stomach lining. The stomach produces mucus to protect itself from the acid's effects, but if this protection fails, it can lead to ulcers or other digestive issues.

If the mucus lining in the stomach were absent, the stomach would be exposed to the corrosive effects of hydrochloric acid. This would lead to the stomach acid digesting the stomach's own tissues, causing ulcers and severe damage to the stomach lining. Consequently, the stomach's function would be impaired, leading to digestive problems and internal bleeding.

Athletes breathe heavily after a race to replenish the oxygen debt incurred during intense physical activity. During the race, their muscles require more energy than the body can supply through normal oxygen intake, leading to anaerobic respiration and the build-up of lactic acid. The heavy breathing helps to clear the excess carbon dioxide, convert lactic acid back into glucose, and restore the body's oxygen levels to normal.

If bile were absent, fat digestion would be significantly impaired because bile emulsifies fats into smaller droplets, increasing the surface area for enzymes to act on. Additionally, the absorption of fat-soluble vitamins would be reduced, impacting overall nutrient uptake.

(1) Presence of a Gizzard (Birds):
→ Birds lack teeth, so they have a specialized organ called a gizzard.
→ Mammals, on the other hand, use their teeth for the initial breakdown of food through chewing.
(2) Crop for Storage (Birds):
→ Many birds have a crop, which is an expanded part of the esophagus used for storing food temporarily.
 → Mammals do not have a crop; instead, their stomach is the primary storage site for ingested food.

Nasal hairs and mucus play a crucial role in the respiratory system by filtering and cleaning the air we breathe. The nasal hairs trap larger particles like dust and pollen, preventing them from entering the lungs. Simultaneously, the mucus moistens the incoming air and traps smaller particles, further ensuring that the air reaching the lungs is clean and humidified, which is essential for healthy respiratory function.

Mechanical digestion is the physical breakdown of food into smaller pieces. This process increases the surface area of food, making it easier for chemical digestion to occur. An example of mechanical digestion is chewing food in your mouth. Your teeth break down large pieces of food into smaller ones, which helps your saliva mix with the food and start the process of chemical digestion.

Food, especially those rich in starch like chapati or rice, tastes sweeter when chewed for a longer time because of the action of saliva. Saliva contains an enzyme called amylase, which breaks down the complex starch molecules into simpler sugars, such as glucose and maltose. These sugars are what give the food a sweet taste as they are released during prolonged chewing.

Digestion is crucial for animals because it breaks down complex food components into simpler, absorbable forms that the body can use. This process is essential for obtaining nutrients needed for energy, growth, and repair. Without digestion, animals cannot effectively utilize the food they consume, leading to malnutrition and an inability to sustain life processes.