Free Respiration in Organisms Subjective Test 01 Practice Test - 7th grade
Question 1
What is cellular respiration? [1 MARK]
SOLUTION
Solution :Cellular respiration takes place in the cells all of organisms. In the cell, glucose is broken down into carbon dioxide and water with the release of energy. All organisms get energy through cellular respiration.
Question 2
Why are yeast cells used to make wines and beers? What do humans produce during anaerobic respiration? [2 MARKS]
SOLUTION
Solution :Reason: 1 Mark
Product of anaerobic respiration: 1 Mark
Under anaerobic conditions, yeast produces alcohol. They are, therefore, used to make wine and beer.
C6H12O6 ---------------> 2C2H5OH + 2CO2 + 2ATP
During anaerobic respiration, humans produce lactic acid in the muscles. The equation for this process is as follows:
Glucose ----------> Latic acid + Energy
Question 3
What is breathing? What are the two steps in breathing? [2 MARKS]
SOLUTION
Solution : Definition: 1 Mark
Steps: 1 Mark
Breathing is the process of taking in of oxygen and giving out carbon dioxide with the help of respiratory organs.
It involves two steps - inhalation and exhalation.
Question 4
What is the percentage of oxygen in inhaled and exhaled air? [2 MARKS]
SOLUTION
Solution : Percentage of oxygen: 1 Mark each
Percentage of oxygen in inhaled air is 21.
Percentage of oxygen in exhaled air is 16.4.
Question 5
What is the percentage of carbon dioxide inhaled from and exhaled into the air? [2 MARKS]
SOLUTION
Solution :Percentage of carbon dioxide: 1 Mark each
Percentage of carbon dioxide in the inhaled air is 0.04.
Percentage of carbon dioxide in the exhaled air is 4.4.
Question 6
What are muscle cramps? How do they happen? How can we recover from them? [3 MARKS]
SOLUTION
Solution :Definition: 1 Mark
Cause: 1 Mark
Recovery: 1 mark
A muscle cramp is a painful contraction or tightening of the muscles for a few seconds.
They happen when the cells in the muscle respire anaerobically. The glucose in the muscles is converted into lactic acid, and the lactic acid accumulation causes cramps.
Muscle cramps can be cured by massages or hot water bath because it improves blood circulation. Blood supplies oxygen to the muscle cells. Oxygen speeds up and completes the breakdown of lactic acid into carbon dioxide and water.
Question 7
How is the breathing process in animals like earthworms, cockroaches and frogs different from human beings? [3 MARKS]
SOLUTION
Solution : Differences: 1 Mark each
Human beings have well-defined organs to breathe. We breathe through our lungs.
Cockroaches have small openings called spiracles on the sides of its body. The air rushes through the spiracles and reaches tracheal tubes, then diffuses into the body tissues and reaches every cell.
Frog breathes through its skin under water. On land frog uses lungs to breathe. Earthworm also breathes through its skin.
Question 8
What are the features seen in the respiratory systems of different organs? [3 MARKS]
SOLUTION
Solution :1 Mark each
Respiratory systems in animals have the following features:
1. They have a large surface area for efficient exchange of gases.
2. They have thin membranes for faster gaseous exchange.
3. They have a rich vascular (blood) supply.
Question 9
Which part of the cell performs respiration? Is this part present in a prokaryote? Name the energy currency of the cell? [3 MARKS]
SOLUTION
Solution :Name of the part: 1 Mark
Statement: 1 Mark
Energy currency: 1 Mark
Mitochondria is the organelle in which cellular respiration takes place.
Prokaryotes are unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle.
The energy currency of cell is ATP (Adenosine tri phosphate).
Question 10
What is breathing rate? What is the normal breathing rate for human beings? How does it vary? [3 MARKS]
SOLUTION
Solution :Breathing rate: 1 Mark
Normal breathing rate: 1 Mark
Variation: 1 Mark
Breathing rate is the number of times a person breathes in a minute. One full inhalation and one full exhalation is counted as a single breath. The number of breaths per minute is calculated for a person to obtain the breathing rate.
The normal breathing rate for human beings during rest is 15 to 18 breaths per minute.
Breathing rate increases during exercising or running. It slows down when sleeping.
Question 11
Why do we add warm water over sore feet? What happens to us after a hot water bath? [3 MARKS]
SOLUTION
Solution :Sore feet: 1 Mark
Hot water bath: 2 Marks
Lactic acid is a normal byproduct during anaerobic respiration in muscles, but it can irritate muscles and cause discomfort and soreness. Adding warm water increases the blood circulation around the sore area. As a result oxygen supply to the muscle cells also increases. The increase in the supply of oxygen results in the complete breakdown lactic acid into carbon dioxide and water.
Skin appears red after a hot water bath. The reason as we know is that, warm water increases the blood circulation in that particular area.
Question 12
Explain exchange of gases and respiration in unicellular organisms [3 MARKS]
SOLUTION
Solution :Respiration: 1 Mark each
1. In unicellular animals, such as amoeba, exchange of gases takes place through cell surface.
2. They absorb oxygen from the surrounding air or water and give out carbon dioxide through plasma membrane by diffusion.
3. The cells use the oxygen absorbed for cellular respiration and derive energy.
Question 13
Label the parts of the human respiratory system. Also, write their functions. [5 MARKS]
SOLUTION
Solution :Part: 1 Mark each
1. Bronchus - The bronchus(plural: bronchi) are extensions of the windpipe that move air to and from the lungs.
2. Trachea - The trachea is a wide, hollow tube that connects the larynx to the bronchi of the lungs.
3. Lung - It is the main part of the respiratory system where the exchange of gases takes place.
4. Bronchioles - The bronchioles are the passageways through which air passes from the bronchi to the alveoli (air sacs) of the lungs.
5. Diaphragm - The diaphragm in the respiratory system is the dome-shaped sheet of muscle that separates the chest from the abdomen. It helps in breathing by expanding the chest cavity during inhalation and contracting it during exhalation.
Question 14
Explain the process of breathing in detail. [5 MARKS]
SOLUTION
Solution :Each point: 1 Mark
The process of breathing happens as follows:
1. We take in air through our nostrils. When we inhale, air passes through nostrils into the nasal cavity which reaches the lungs through windpipes.
2. The chest cavity where the lungs are present is surrounded by ribs on the sides and diaphragm forms the base.
3. Breathing involves the movement of the diaphragm and the rib cage.
4.During inhalation, ribs move up and the diaphragm moves down to increase the chest cavity space. When the volume in the lungs increases, pressure decreases, which fill the lungs with air.
5. During exhalation, ribs move down and the diaphragm moves up to its former position. The lungs contract and lower volume increase the pressure in the lungs, pushing the air out.
Question 15
Take three test tubes and label them as A, B and C. Fill 34th of each with water. Keep a snail in test tube A, a water plant in test tube B and in C, keep both snail and plant. In which of these test tubes CO2 (carbon dioxide) level will be higher? What does this experiment show? Explain what happens in each test tube separately. [5 MARKS]
SOLUTION
Solution :Observations: 1 Mark each
1. Test tube A will have the highest concentration of CO2.
2. The experiment shows respiration in animals and plants.
3. Test tube A: During breathing, the snail inhales dissolved oxygen from water and releases CO2.
4. Test tube B: The water plants along with respiration performs photosynthesis (food preparation); therefore it absorbs CO2 and releases O2.
5. Test tube C: The CO2 released by the snail will be used by the plant for photosynthesis, thus there will be a balance of gases.