Science 2 Marks Questions

The air we breathe in transported to every parts of body and ultimately it is transported to each cell, in the cells, oxygen in the air helps in the breakdown of food, this process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration occurs in the cells of all organisms.

The stomatal pores are enclosed by two guard cells, which are surrounded by several subsidiary cells. All these three, namely stomatal pores, guard cells and subsidiary cells together constitute stomatal apparatus. The flow of the water into and out of guard cells facilitates closing and opening of stomatal pores. This results in the exchange of gases.

Our body needs energy for all activities. While doing heavy exercises like running, there is larger demand of energy to perform those activities. Hence more oxygen is required to meet extra demand of energy. Therefore an athlete breathe faster and deeper than usual after finishing the race.
Also during running, due to lack of oxygen, some muscles may respire anaerobically and form lactic acid. Extra oxygen is also required to burn this lactic acid into carbon dioxide.

Fish gulps water through mouth and forces it between the gills. The oxygen in it gets diffused into the blood circulating in gills and carbon dioxide in the bloodstream diffuses into the water which is carried out through a gap between fish’s body and the gill cover.

When we work hard or perform physical activity (like running, swimming, cycling), we need mdre energy. To fulfil the energy requirement, we breathe faster. Fast breathing helps in supply of more oxygen to our cells. Due to this, rate of breakdown of food increases and more energy is released. The rapid breakdown of food makes us to feel more hungry.

A cockroach has a small opening on the side of its body, these openings are called spiracles. Oxygen rich air rushes through spiracles into the tracheal tubes diffuses into the body tissue and reaches every cell of body. In the same way carbon dioxide from the cells goes into the tracheal tube and moves out through spiracles.

1. Figure A indicates inhalation and figure 6 indicates exhalation. During inhalation, the ribs contract to move outward and upward, while during exhalation, the movement reverses, i.e. ribs relaxes to move inward and downward.

If we want to make our own bread, we can buy yeast in the grocery store. This yeast consists of little brown grains. The little brown grains of yeast may not seem to be alive, but if we put them in water with sugar, the yeast will carry out cellular respiration and grow. We can grow yeast in a test tube filled with water and sealed with a balloon. Under anaerobic conditions, yeast carries out alcoholic fermentation, so it produces lactic acid and energy.

The end product formed during anaerobic respiration in yeast are:

• Ethyl alcohol.
• Carbon dioxide.
• Energy.

When we inhale dust-laden air, dirt particles are captured within the nostrils. Sometimes they get past the nostril hair in the nasal cavity and irritate the lining of the cavity. As a result we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

Respiration is the process of breakdown of food to produce energy for performing various functions. It involves two major steps:

• Inhalation is the process of taking in of air which is rich in oxygen, inside our body.
• Exhalation is the process of giving out of air which is rich in carbon dioxide from our body to the external environment.

A cockroach has a small opening on the side of its body, these openings are called spiracles. Oxygen rich air rushes through spiracles into the tracheal tubes diffuses into the body tissue and reaches every cell of body. In the same way carbon dioxide from the cells goes into the tracheal tube and moves out through spiracles.
Water animals have gills that help them to use oxygen dissolved in water. Gills are projections of the skin which are well supplied with blood vessels for exchange of gases.

When we inhale a lot of dust laden air, the dust particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

The massage or hot water bath gives relief from muscle cramps or pain, because it improves the circulation of blood leading to increased supply of oxygen to the muscle cells. It helps in complete breakdown of lactic acid into carbon dioxide and water.

Roots of the plants respire under the ground. Root cells get oxygen from the air present in the space between the soil particles. There are several root hairs present on the roots of a plant. The oxygen from the air (between soil particle) diffuses into root hair and reaches to the cells of the roots. This oxygen is utilised for respiration.

Yeast is single celled organism that respires anaerobically and during this process yield alcohol. Yeast get energy through anaerobic respiration, in the absence of oxygen, glucose breaks down into oxygen and carbon dioxide, The equation for the reaction is as follow: Glucose in absence of oxygen → alcohol + carbon dioxide + energy

The air we breathe in transported to every parts of body and ultimately it is transported to each cell, in the cells, oxygen in the air helps in the breakdown of food, this process of breakdown of food in the cell with the release of energy is called cellular respiration.

During heavy exercise the demand for energy is high. But the supply of oxygen to produce energy is limited. Then anaerobic respiration takes place in the muscle cells to fulfil the demand of energy. Glucose in absence of oxygen → Lactic Acid + Energy. The cramps occur only when the muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.

When the air breathed in reaches the lungs it enters the alveoli. The alveoli are lined with blood capillaries and exchange of gases occurs. The oxygen from the alveoli is taken up by the capillaries and carbon dioxide from the blood is transferred to alveoli.

A cockroach has a small opening on the side of its body, these openings are called spiracles. Oxygen rich air rushes through spiracles into the tracheal tubes diffuses into the body tissue and reaches every cell of body. In the same way carbon dioxide from the cells goes into the tracheal tube and moves out through spiracles.

We take in air through our nostrils, when we inhale air, it passes through our nostril into nasal cavity and from there it reaches our lungs through the wind pipe. Lungs are present in chest cavity which is surrounded by ribs on the sides, diaphragm forms the floor of chest cavity. Breathing involves the movement of diaphragm and the rib cage.

When diaphragm contracts and moves downwards, the chest cavity enlarges and the pressure in lungs decreases. The air is breathed in to equalise pressure. When diaphragm relaxes and moves upwards, the lungs push out the air.