YASRAJ STUDIES
DAV Class 7 Science Chapter 7 Question Answer – Respiration in Organisms
Introduction
Respiration is an important life process through which living organisms obtain energy from food. During respiration, food is broken down to release energy needed for different activities.
In this chapter, we learn about respiration, breathing, aerobic and anaerobic respiration, respiratory organs in different organisms, breathing rate, and respiration in plants.
A. Fill in the Blanks
1. Lactic acid is produced during __________ respiration.
Answer: Anaerobic
Explanation: When muscles do not get enough oxygen during heavy exercise, they can carry out anaerobic respiration. This process produces lactic acid, which may cause muscle cramps.
2. Insects have organs, called __________ for respiration.
Answer: Tracheae
Explanation: Insects breathe through a network of air tubes called tracheae. These tubes carry air directly to different parts of the insect's body.
3. Taking in of air, rich in oxygen, is called __________.
Answer: Inspiration
Explanation: The process of taking air into the lungs is called inspiration or inhalation. The air taken in contains oxygen needed for respiration.
4. An adult human being normally breathes from __________ to __________ times per minute.
Answer: 14 to 20
Explanation: A healthy adult normally takes about 14–20 breaths per minute while at rest. The breathing rate can increase during exercise.
5. The movement of lungs is controlled by the __________ and the __________.
Answer: Rib cage and diaphragm
Explanation: The rib cage and diaphragm help the lungs expand and contract during breathing. The diaphragm moves downward during inspiration and upward during expiration.
6. __________ acts as the respiratory carrier in our body.
Answer: Haemoglobin
Explanation: Haemoglobin is present in red blood cells. It combines with oxygen and transports it from the lungs to different parts of the body.
B. Match the Following
| Column A | Column B |
|---|---|
| 1. Lactic acid | (e) Muscle cramps |
| 2. Stomata | (c) Transpiration |
| 3. Respiratory carrier | (d) Haemoglobin |
| 4. Lenticels | (a) Pores on branches |
| 5. Alcohol | (b) Fermentation of yeast |
Explanation
- Lactic acid → Muscle cramps: Lactic acid may accumulate in muscles during strenuous activity.
- Stomata → Transpiration: Plants lose water vapour mainly through stomata.
- Respiratory carrier → Haemoglobin: Haemoglobin carries oxygen in the blood.
- Lenticels → Pores on branches: Lenticels are small openings present on the stems of many plants.
- Alcohol → Fermentation of yeast: Yeast produces alcohol and carbon dioxide during fermentation.
C. Tick (✓) the Correct Option
1. Respiration helps in
Answer: (d) Obtaining energy
Explanation: Respiration breaks down food and releases energy. This energy is used for various life processes such as movement, growth and repair.
2. Stomata performs the function of
Answer: (c) Exchange of gases
Explanation: Stomata are tiny openings on the surface of leaves. They allow the exchange of gases such as oxygen and carbon dioxide. They also help in transpiration.
3. The process represented by the following equation,
Glucose + oxygen → Carbon dioxide + water + energy
Answer: (d) Is aerobic respiration
Explanation: Aerobic respiration takes place in the presence of oxygen. Glucose is broken down to form carbon dioxide, water and energy.
4. To survive, plant roots need
Answer: (b) Oxygen
Explanation: Roots also respire. They need oxygen from the air spaces present in the soil for respiration.
5. Earthworms and leeches respire through their
Answer: (d) Skin
Explanation: Earthworms and leeches do not have lungs. They exchange gases through their moist skin.
D. Answer the Following Questions in Brief
1. Define respiration. Name the two types of respiration.
Answer: Respiration is the process by which food is broken down in living organisms to release energy. The two types of respiration are:
- Aerobic respiration
- Anaerobic respiration
Explanation: Aerobic respiration takes place in the presence of oxygen, while anaerobic respiration takes place without using oxygen. Both processes help organisms obtain energy.
2. Name the respiratory organ of the following:
(a) Crab
Answer: Gills
Explanation: Crabs live in water and use gills to take oxygen from water.
(b) Man
Answer: Lungs
Explanation: Humans breathe through their lungs. Oxygen enters the blood through the lungs.
(c) Leech
Answer: Skin
Explanation: Leeches exchange gases through their moist skin.
(d) An insect
Answer: Tracheae
Explanation: Insects have a network of air tubes called tracheae for respiration.
3. Define transpiration.
Answer: Transpiration is the loss of water vapour from the aerial parts of a plant, mainly through stomata and also through lenticels.
Explanation: Plants lose some of the water absorbed by their roots in the form of water vapour. This process is called transpiration.
4. Define the term ‘breathing rate’.
Answer: The number of breaths taken by a person in one minute is called the breathing rate.
Explanation: For example, if a person takes 18 breaths in one minute, their breathing rate is 18 breaths per minute. Exercise usually increases the breathing rate.
5. Name the body organs which help lungs during the process of breathing.
Answer: The rib cage and diaphragm help the lungs during breathing.
Explanation: The rib cage protects the lungs and moves during breathing. The diaphragm changes the size of the chest cavity, helping air enter and leave the lungs.
6. Why do we need to breathe out carbon dioxide?
Answer: We need to breathe out carbon dioxide because it is a waste product of respiration and must be removed from the body.
Explanation: During respiration, carbon dioxide is produced. It is carried by the blood to the lungs and then removed from the body when we exhale.
E. Answer the Following Questions
1. Why do we get muscle cramps after heavy exercise?
Answer: During heavy exercise, our muscles need more energy and may not receive enough oxygen. In such conditions, anaerobic respiration takes place in muscle cells. It produces lactic acid, which can accumulate in the muscles and cause cramps.
Explanation: This is why a person may experience muscle cramps after strenuous physical activity. Rest and normal breathing help the muscles recover.
2. Why does a potted plant die when overwatered?
Answer: Overwatering fills the spaces between soil particles with water and reduces the amount of air available to the roots. As a result, the roots do not get enough oxygen for respiration and the plant may eventually die.
Explanation: Roots need oxygen for respiration. Therefore, proper drainage and a suitable amount of water are important for healthy plant growth.
3. Where are stomata found in a plant? State their function.
Answer: Stomata are tiny openings mainly found on the surface of leaves.
Their main functions are:
- Exchange of gases.
- Loss of water vapour through transpiration.
Explanation: Stomata allow carbon dioxide to enter the leaf and oxygen to leave during gas exchange. Water vapour also passes out through them.
4. How is oxygen transported from lungs to the other parts of the body?
Answer: Oxygen enters the blood from the lungs. It combines with haemoglobin present in red blood cells. Haemoglobin then carries oxygen to different parts of the body.
Explanation: The lungs provide oxygen to the blood, while haemoglobin acts as the carrier that transports it to body tissues.
5. Draw a neat, well-labelled diagram of the human respiratory system.
Answer: Draw and label the following parts in a neat diagram:
- Nose/Nasal cavity
- Windpipe (Trachea)
- Bronchi
- Lungs
- Diaphragm
Explanation: The human respiratory system helps in taking oxygen into the body and removing carbon dioxide. Air passes through the nose and trachea before reaching the lungs.
6. Describe an activity to show that exhaled air contains carbon dioxide.
Answer:
Activity
- Take some freshly prepared lime water in a test tube.
- Put one end of a clean straw into the lime water.
- Blow gently through the straw.
- Observe the lime water.
The lime water turns milky.
Explanation: Exhaled air contains carbon dioxide. Carbon dioxide reacts with lime water and produces a substance that makes the lime water appear milky. Thus, the experiment shows that exhaled air contains carbon dioxide.
7. Describe the changes that take place around the rib cage, diaphragm and chest cavity during inspiration. State the effect of these changes.
Answer:
During inspiration:
- The rib cage moves upwards and outwards.
- The diaphragm moves downwards and becomes flatter.
- The chest cavity increases in size.
- The lungs expand.
- Air moves into the lungs.
Explanation: When the chest cavity becomes larger, air is drawn into the lungs. This process is called inspiration or inhalation.
Value Based Question
It was time for the 400 m race in the annual athletic meet of the school. Shweta, who was tipped to win the race, maintained a clear lead over others till about 30 m from the finishing line. She then felt cramps in her legs but did not give up. She quickly took some deep and fast breaths and continued running. Her presence of mind, determination, courage and positive attitude helped her to just manage to win the race. Rita and Neetu, who finished second and third, respectively, were the first to congratulate her on her success.
1. State the values displayed by Shweta.
Answer: Shweta displayed:
- Determination
- Courage
- Presence of mind
- Positive attitude
- Perseverance
Explanation: Shweta did not give up when she faced difficulty. She remained determined and continued her effort. These qualities helped her complete the race successfully.
2. Write about some situation in which you, or one of your friends, displayed a behaviour similar to that of Rita and Neetu.
Answer: During a school competition, my friend performed very well and won the first position. Although I did not win, I congratulated my friend sincerely and appreciated the hard work.
Explanation: Congratulating others for their success shows sportsmanship, friendship and a positive attitude. We should appreciate the efforts of others instead of feeling jealous.
3. State the likely reason due to which Shweta felt cramps in her legs.
Answer: Shweta was running fast, so her leg muscles required a large amount of energy. When the oxygen supply was not sufficient, anaerobic respiration took place in the muscles. Lactic acid was produced and this could have caused the cramps.
Explanation: During strenuous exercise, muscles may temporarily use anaerobic respiration when their oxygen supply cannot meet their energy demand.
Something To Do
1. Observe the changes in a leaf when both of its surfaces are coated with oil/Vaseline. Perform this activity and give a simple explanation of your observation.
Answer: Take a healthy leaf and coat both its surfaces with a thin layer of oil or Vaseline. Observe the leaf for some time.
The leaf will gradually become unhealthy and may eventually die.
Explanation: The coating blocks the stomata and interferes with gas exchange. Since leaves need gases for their life processes, blocking the stomata affects normal functioning of the leaf.
2. Find out about two diseases related to the respiratory system. List their causes, their effect on respiration and their cure.
Answer:
| Disease | Cause | Effect on Respiration | Treatment |
|---|---|---|---|
| Asthma | Allergens and other triggers | Causes difficulty in breathing and narrowing of airways | Managed with medicines prescribed by a doctor |
| Pneumonia | Infection of the lungs | Can make breathing difficult and affect normal lung function | Treatment depends on the cause and should be taken under medical advice |
Explanation: Respiratory diseases can affect the normal functioning of the respiratory system. Proper medical care is important when a person has breathing problems or symptoms of respiratory illness.
3. Record the breathing rates of your friends and their family members:
Let the person rest for 15 minutes after performing each activity. Enter your results in the table given below.
| Name of the Person | At Rest | After Brisk Walk for 10 Minutes | After Skipping 100 Times |
|---|---|---|---|
| __________ | __________ | __________ | __________ |
| __________ | __________ | __________ | __________ |
| __________ | __________ | __________ | __________ |
| __________ | __________ | __________ | __________ |
Answer: Do it yourself.
Explanation: Breathing rate generally increases after physical activity because working muscles require more oxygen and produce more carbon dioxide. After resting, the breathing rate gradually returns towards its normal resting level.
Important Points to Remember
- Respiration releases energy from food.
- Respiration may be aerobic or anaerobic.
- Humans breathe with the help of lungs.
- Rib cage and diaphragm help in breathing.
- Haemoglobin transports oxygen in the blood.
- Insects respire through tracheae.
- Earthworms and leeches respire through their skin.
- Crabs respire through gills.
- Stomata help plants in gas exchange and transpiration.
- Lactic acid may be produced during anaerobic respiration in muscles.
- Breathing rate increases during exercise.
- Carbon dioxide is a waste product of respiration and is removed during exhalation.
Conclusion
Respiration is an essential life process that provides energy to living organisms. Different organisms have different respiratory organs according to their surroundings and body structures. In humans, the lungs, rib cage and diaphragm work together to carry out breathing, while haemoglobin transports oxygen throughout the body. Understanding respiration helps us learn how living organisms obtain and use energy.
