Olympiad Test: Respiration In Organisms -1 - Class 7 MCQ

Answer:
The process by which gases are exchanged between the body and the surrounding environment is called breathing. Here is a detailed explanation:
1. Definition of breathing:
- Breathing is the process of taking in oxygen-rich air (inhaling) and removing carbon dioxide (exhaling) from the body.
- It involves the movement of air into and out of the lungs, allowing for the exchange of gases between the blood and the air.
2. Steps involved in breathing:
- Inhalation: During inhalation, the diaphragm and intercostal muscles contract, expanding the chest cavity and increasing the volume of the lungs. This creates a negative pressure that draws air into the lungs.
- Exhalation: During exhalation, the diaphragm and intercostal muscles relax, decreasing the volume of the lungs. This increases the pressure inside the lungs, forcing air out.
3. Importance of breathing:
- Breathing is essential for the survival of organisms as it supplies oxygen to the body's cells and removes carbon dioxide, a waste product of cellular respiration.
- Oxygen is required for the production of energy through cellular respiration, which is necessary for various bodily functions.
4. Organs involved in breathing:
- Lungs: The lungs are the primary organs involved in the exchange of gases. They contain millions of tiny air sacs called alveoli, where oxygen from the inhaled air enters the bloodstream and carbon dioxide is removed.
- Diaphragm and intercostal muscles: These muscles play a crucial role in the expansion and contraction of the chest cavity during breathing.
In conclusion, the correct answer is A: breathing. It is the process through which gases, particularly oxygen and carbon dioxide, are exchanged between the body and the surrounding environment.

Respiration is a catabolic process. Here's a detailed explanation:
Definition of respiration:
- Respiration is the process by which organisms convert energy stored in the chemical bonds of organic molecules into a form that can be used by cells to perform their functions.
- It involves the breakdown of organic molecules, such as glucose, and the release of energy in the form of ATP (adenosine triphosphate).
Catabolic process:
- Catabolism refers to the breakdown of complex molecules into simpler ones.
- Respiration involves the catabolic breakdown of glucose or other organic molecules to release energy.
- During respiration, glucose is oxidized through a series of enzymatic reactions, resulting in the production of carbon dioxide, water, and ATP.
- The energy released during this process is used to perform various cellular functions.
Key points:
- Respiration is a catabolic process because it involves the breakdown of complex organic molecules (glucose) into simpler ones (carbon dioxide and water).
- It releases energy in the form of ATP, which is used by cells for various metabolic activities.
- Catabolic processes are generally associated with the release of energy, while anabolic processes involve the synthesis of complex molecules and require energy input.
- In contrast to respiration, anabolic processes build complex molecules and are often referred to as biosynthesis.
Therefore, the correct answer is B: catabolic.

Food material used to release energy in body cells:
- The food material that is used to release energy in body cells is glucose.
- Glucose is a type of sugar that is obtained from the breakdown of carbohydrates.
- When we consume food, carbohydrates are broken down into glucose during digestion.
- Glucose is then transported to body cells through the bloodstream.
- Once inside the cells, glucose undergoes a series of chemical reactions known as cellular respiration.
- During cellular respiration, glucose is broken down further in the presence of oxygen to produce energy in the form of ATP (adenosine triphosphate).
- ATP is the energy currency of the cell and is used for various cellular processes.
- In addition to glucose, other molecules such as fatty acids and amino acids can also be used as sources of energy in body cells.
- However, glucose is the primary fuel source for most cells in the body.
- The process of releasing energy from glucose is essential for the functioning of various bodily systems and is necessary for activities such as muscle contraction, nerve transmission, and overall metabolism.

Plants exchange gases through stomata

Stomata are tiny openings or pores on the surface of leaves and stems of plants. They play a crucial role in the exchange of gases during photosynthesis and respiration. Here's how plants exchange gases through stomata:

• Gaseous exchange: Stomata allow the entry of carbon dioxide (CO2) into the plant and the exit of oxygen (O2) produced during photosynthesis.


• Opening and closing: Stomata can open and close to regulate gas exchange. This is controlled by specialized cells called guard cells that surround the stomata.


• Transpiration: Stomata also play a role in transpiration, which is the loss of water vapor from the plant. When stomata open, water vapor escapes, helping to cool the plant and facilitate the movement of nutrients.


• Water conservation: To prevent excessive water loss, stomata can close during hot and dry conditions. This minimizes water loss through transpiration.


• Gas diffusion: The gases diffuse through the stomatal pores. Carbon dioxide enters the plant through the stomata and travels to the chloroplasts in the leaves, where it is used for photosynthesis. Oxygen, produced during photosynthesis, exits the plant through the stomata.

In summary, stomata are crucial structures in plants that facilitate the exchange of gases, including carbon dioxide and oxygen, allowing for photosynthesis and respiration to occur.

Anaerobic respiration is also termed as
Anaerobic respiration is the process by which cells produce energy in the absence of oxygen. It occurs in various organisms, including bacteria, yeast, and some human cells. This process is also known as fermentation.
Explanation:
- Anaerobic respiration is a metabolic process that occurs in the absence of oxygen. It allows cells to produce energy when oxygen is not available.
- This process is common in organisms that live in environments with low oxygen levels or in situations where oxygen cannot be efficiently delivered to the cells.
- During anaerobic respiration, glucose is broken down in a series of chemical reactions to produce ATP (adenosine triphosphate), the energy currency of the cell.
- The end products of anaerobic respiration vary depending on the organism. In some cases, the end product is lactic acid, while in others, it is ethanol and carbon dioxide.
- Anaerobic respiration is less efficient than aerobic respiration, as it produces fewer ATP molecules per glucose molecule.
- Fermentation is a specific type of anaerobic respiration that occurs in microorganisms such as yeast and bacteria. It involves the breakdown of glucose into ethanol and carbon dioxide or lactic acid.
- Fermentation is used in various industrial processes, such as the production of alcoholic beverages and bread.
- The other options, transportation and imbibitions, are not related to anaerobic respiration and are incorrect choices.

Why do fishes in aquarium move their mouth repeatedly?

Fishes in aquarium move their mouth repeatedly because:

• They keep breathing with it: Fishes extract oxygen from the water using their gills, which are located inside their mouths. By continuously moving their mouths, they are able to ensure a constant flow of water over their gills, allowing them to extract oxygen and remove carbon dioxide.

It is important to note that fishes do not have vocal cords, so they do not talk or make sounds by moving their mouths. Their mouth movements are primarily related to respiration and not communication.

In man nostrils are analogus to spiracles, through nostrils air enters into nasal cavity. Nostrils consists of fine air and lined with mucus. Hair filters the air from dust particles. 

Prevention of Food Entry into the Trachea
The prevention of food entry into the trachea is a crucial function to ensure the proper functioning of the respiratory system. The opening leading to the trachea is guarded by several structures, with the main one being the epiglottis. Here's a detailed explanation of the prevention mechanism:
1. Epiglottis:
- The epiglottis is a flap-like structure located at the base of the tongue.
- It acts as a lid, covering the opening of the trachea (glottis) during swallowing to prevent food or liquid from entering.
- The epiglottis is composed of elastic cartilage, allowing it to bend and seal off the trachea.
2. Glottis:
- The glottis refers to the opening between the vocal cords in the larynx.
- During normal breathing, the glottis remains open, allowing air to pass freely into the trachea.
- However, during swallowing, the glottis closes to prevent food or liquid from entering the trachea.
3. Soft Palate:
- The soft palate is a muscular structure located at the back of the roof of the mouth.
- It helps prevent food from entering the nasal cavity during swallowing.
- The soft palate is raised, closing off the nasal passage, while the epiglottis covers the trachea.
4. Hard Palate:
- The hard palate is the bony portion of the roof of the mouth.
- While it does not directly guard the opening to the trachea, it plays a role in the process of chewing and breaking down food before swallowing.
Overall, the coordinated actions of the epiglottis, glottis, soft palate, and hard palate work together to prevent the entry of food into the trachea and ensure that the respiratory and digestive systems function properly.

Respiratory membrane should be semipermeable to allow exchange of gases.

The narrowest and most numerous tubes of lungs are termed as bronchioles.
- Definition: Bronchioles are the smallest branches of the bronchial tree, which is the system of airways in the lungs. They are responsible for carrying air from the bronchi (larger airways) to the alveoli (air sacs) in the lungs.
- Narrowness: Bronchioles are narrower in diameter compared to the bronchi, allowing for more precise regulation of airflow within the lungs. Their narrowness increases the velocity of airflow, facilitating efficient gas exchange in the alveoli.
- Number: Bronchioles are the most numerous tubes in the lungs, branching extensively to reach all areas of the lung tissue. This extensive branching provides a large surface area for gas exchange to occur.
- Structure: The walls of bronchioles are composed of smooth muscle, elastic fibers, and a thin layer of epithelial cells. The smooth muscle can contract and relax, allowing for regulation of airflow and control of ventilation.
- Function: The bronchioles play a crucial role in delivering air to the alveoli, where oxygen is taken up by the bloodstream and carbon dioxide is expelled. They also help in humidifying and warming the inhaled air before it reaches the alveoli.
- Relation to other structures: Bronchioles branch off from the bronchi and further divide into even smaller tubes called terminal bronchioles. These terminal bronchioles then connect to the respiratory bronchioles, which lead to the alveoli.
In summary, bronchioles are the narrowest and most numerous tubes in the lungs. They are responsible for delivering air to the alveoli and play a vital role in the process of respiration.

The bean-shaped cells of stomata are called guard cells.
Stomata are tiny openings or pores found on the surface of leaves and stems of plants. They play a crucial role in facilitating gas exchange and regulating water loss through transpiration. The guard cells are specialized cells that surround and control the opening and closing of the stomata.
Guard cells have the following characteristics:
- Bean-shaped: Guard cells have a unique shape resembling a kidney or bean, with a thicker middle portion and two curved sides.
- Pair arrangement: They are usually found in pairs, with one guard cell located on either side of the stomatal pore.
- Chloroplasts: Guard cells contain chloroplasts, which enable them to perform photosynthesis and produce energy for their functions.
- Elasticity: The inner walls of guard cells are thicker and rigid, while the outer walls are thinner and more elastic. This structural arrangement allows the guard cells to change shape and control the opening and closing of the stomata.
- Stomatal pore: The stomatal pore is the opening between the two guard cells. When the guard cells are turgid or swollen, the stomatal pore opens, allowing the exchange of gases. Conversely, when the guard cells lose water and become flaccid, the stomatal pore closes, reducing water loss through transpiration.
Importance of guard cells:
- Gas exchange: Guard cells control the opening and closing of stomata, allowing the exchange of gases such as oxygen, carbon dioxide, and water vapor with the surrounding environment.
- Photosynthesis: The presence of chloroplasts in guard cells enables them to produce energy through photosynthesis, contributing to the plant's overall metabolic processes.
- Transpiration regulation: By opening and closing the stomata, guard cells help regulate the rate of transpiration, which is the loss of water vapor through the stomata. This process is crucial for maintaining the plant's water balance and preventing excessive water loss.
In conclusion, the bean-shaped cells of stomata are called guard cells. These specialized cells play a vital role in regulating gas exchange and water loss in plants.

The number of guard cells forming a stomata is 2.
Explanation:
The stomata are small openings or pores found on the surface of leaves, stems, and other plant organs. They play a crucial role in the exchange of gases and water vapor between the plant and its environment. Each stomata consists of two specialized guard cells that surround the pore.
The guard cells are responsible for opening and closing the stomata, allowing for the exchange of gases and regulating water loss through transpiration. When the guard cells are turgid, they swell and create an opening between them, allowing carbon dioxide to enter the leaf for photosynthesis. When the guard cells are flaccid, they close the stomata to prevent excessive water loss.
Therefore, the correct answer is A: 2.

The actual site of gaseous exchange in respiratory system is alveoli. Alveolus are richly supplied with blood capillaries permeable membrane which allows exchange of gases through it. 

The trachea is prevented from collapsing by:
Incomplete cartilaginous rings:
- The trachea is supported by a series of C-shaped cartilaginous rings.
- These rings are incomplete, meaning they do not encircle the entire trachea.
- The rings are open at the back, allowing flexibility and movement.
Function of the cartilaginous rings:
- The cartilaginous rings provide structural support to the trachea.
- They help to maintain the shape and patency of the tracheal lumen, preventing it from collapsing.
- The rings are rigid enough to keep the trachea open during inhalation and exhalation.
- The open ends of the rings allow the trachea to expand and contract as needed.
Alternative options:
- Bony rings and chitinous rings are not correct options as they do not exist in the human trachea.
- Complete cartilaginous rings are also not correct as they would restrict the flexibility and movement of the trachea.
In summary:
The trachea is prevented from collapsing by the presence of incomplete cartilaginous rings. These rings provide structural support while allowing flexibility and movement of the trachea.

Tracheal System in Cockroach
The tracheal system in a cockroach is responsible for the exchange of gases, allowing the insect to breathe. It consists of a network of tubes called tracheae that extends throughout the body, delivering oxygen directly to the cells.
Opening of the Tracheal System
The opening of the tracheal system in a cockroach is through structures called stigmata. Stigmata are tiny pores or spiracles located on the lateral sides of the body segments. There are a total of 10 pairs of stigmata in a cockroach, with one pair on each of the thoracic and abdominal segments.
Function of Stigmata
The stigmata serve as the openings of the tracheal system, allowing oxygen to enter and carbon dioxide to exit the body. They are surrounded by specialized muscles known as the spiracular muscles, which control their opening and closing.
Respiratory Process
1. When a cockroach takes in air, the spiracular muscles relax, allowing the stigmata to open.
2. Oxygen from the environment enters the tracheal system through the open stigmata.
3. The oxygen then diffuses through the tracheae and reaches the cells of the body, where it is utilized for cellular respiration.
4. Carbon dioxide, a waste product of cellular respiration, diffuses out of the cells and enters the tracheae.
5. The carbon dioxide is then expelled from the body through the open stigmata.
Conclusion
The tracheal system in a cockroach opens to the outside through the stigmata, which are tiny pores located on the lateral sides of the body segments. These stigmata allow for the exchange of gases, enabling the cockroach to breathe and carry out cellular respiration.

Respiratory System:
- The respiratory system is responsible for the exchange of gases, particularly oxygen and carbon dioxide, between the body and the external environment.
- It includes organs such as the nose, windpipe (trachea), lungs, and blood vessels.
Passage of Oxygen in the Respiratory System:
- Oxygen enters the respiratory system through the nose.
- From the nose, it travels through the windpipe (trachea).
- The windpipe branches into smaller tubes called bronchi, which lead to the lungs.
- In the lungs, oxygen diffuses into the bloodstream through the walls of tiny air sacs called alveoli.
- The oxygen-rich blood is then transported to the body's cells, where it is used for cellular respiration.
- Carbon dioxide, a waste product of cellular respiration, is carried back to the lungs through the bloodstream.
- In the lungs, carbon dioxide is expelled from the body when we exhale.
Correct Diagram:
The correct diagram illustrating the passage of oxygen in the respiratory system is:
C: Nose → windpipe → lungs → blood

Gills are the respiratory organs in aquatic animals. Gills are richly supplied with blood vessels when water enters into the bronchial chamber dissolved oxygen from the water is absorbed.

The short tube leading from the nose is the pharynx.
The pharynx is a muscular tube that connects the nasal cavity and the mouth to the esophagus and the larynx. It serves as a passage for both air and food.
Why the other options are incorrect:
- Alveoli: Alveoli are tiny air sacs located at the ends of the bronchioles in the lungs. They are not part of the nasal passage.
- Trachea: The trachea, also known as the windpipe, is a long tube that connects the larynx to the bronchi. It is located below the pharynx.
- Bronchi: The bronchi are the two main branches of the trachea that lead into the lungs. They are not part of the nasal passage.
Key Points:
- The short tube leading from the nose is called the pharynx.
- The pharynx connects the nasal cavity and the mouth to the esophagus and the larynx.
- The pharynx serves as a passage for both air and food.

Answer:
The correct answer is A: trachea. The air goes from the pharynx (throat) to the trachea (windpipe) in the respiratory system. Here is a detailed explanation of the pathway of air:
Pharynx:
- The pharynx is the region at the back of the throat where both food and air pass through.
- It serves as a common pathway for both the digestive and respiratory systems.
Trachea:
- The trachea, also known as the windpipe, is a tube-like structure that connects the pharynx to the lungs.
- It is made up of C-shaped rings of cartilage, which provide support and prevent the trachea from collapsing.
- The trachea is lined with tiny hair-like structures called cilia, which help to filter and remove any foreign particles from the air.
Bronchi:
- The trachea divides into two main branches called bronchi.
- The bronchi are further divided into smaller branches called bronchioles, forming a branching network in the lungs.
Bronchioles:
- The bronchioles are small, thin-walled tubes that carry air from the bronchi to the alveoli (small air sacs in the lungs).
- They do not have cartilage like the trachea and bronchi, but they have smooth muscles that help regulate airflow.
In summary, the air travels from the pharynx to the trachea, then to the bronchi, and finally to the bronchioles.

Lactic acid accumulation leads to muscle fatigue. It is also called as muscle cramp, due to the insufficient supply of oxygen.