Exercises: Respiration in Organisms | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

I. Objective Type Questions

A series of chemical reactions result in the release of energy by oxidation of food.
The breakdown of food molecules into energy occurs through a series of chemical reactions known as cellular respiration, which involves the oxidation of food molecules like glucose.

Q.2. When the diaphragm ____ (contracts/expands) oxygen-rich air is taken into the lungs.

When the diaphragm contracts, oxygen-rich air is taken into the lungs.
The diaphragm is a muscle located at the base of the lungs that contracts during inhalation, allowing the lungs to expand and take in oxygen-rich air.

Q.3. The wind pipe is made up of several ring-like structures, held together by ____ (muscles/cartilage).

The windpipe is made up of several ring-like structures, held together by cartilage.
The windpipe, also known as the trachea, is a tube-like structure made up of several C-shaped cartilage rings that prevent the airway from collapsing and allow for smooth airflow during breathing.

Q.4. Plant roots typically take in ____ (oxygen/carbon dioxide) available in small spaces between soil particles and give off ____ (oxygen/carbon dioxide).

Plant roots typically take in oxygen available in small spaces between soil particles and give off carbon dioxide.
Plant roots need oxygen for respiration, and they obtain it from the air pockets present in the soil. During respiration, they release carbon dioxide as a by-product.

Q.5. ____ (Aerobic/Anaerobic) respiration is the most efficient form of respiration.

Aerobic respiration is the most efficient form of respiration.
Aerobic respiration is a type of cellular respiration that requires oxygen and yields a large amount of energy in the form of ATP molecules. It is the most efficient form of respiration because it produces the maximum amount of energy from the breakdown of glucose, resulting in a higher yield of ATP molecules. Anaerobic respiration is less efficient because it produces less ATP and can also result in the buildup of lactic acid or other toxic by-products.

B. Choose the correct option.

II. Very Short Answer Type Questions

Fish, tadpoles.

Q.2. Animals that breathe through spiracles ____ ____

Insects, such as grasshoppers and cockroaches.

Q.3. Animals that breathe through their moist skin as well as their lungs ____ ____

Frogs, salamanders.

Q.4. Organisms that respire anaerobically ____ ____

Yeast, some bacteria.

III. Short Answer Type Questions

Respiration is the process by which living organisms take in oxygen and release carbon dioxide. It is called a chemical process because it involves the breaking down of glucose molecules in the presence of oxygen to release energy in the form of ATP (Adenosine Triphosphate).

Q.2. How does the diaphragm help in pumping air?

The diaphragm is a dome-shaped muscle that separates the chest cavity from the abdominal cavity. During inhalation, the diaphragm contracts and moves downwards, which increases the volume of the chest cavity and decreases the pressure in the lungs. This creates a pressure difference between the lungs and the atmosphere, causing air to rush into the lungs. During exhalation, the diaphragm relaxes and moves upwards, decreasing the volume of the chest cavity and increasing the pressure in the lungs, which causes air to be pushed out of the lungs.

Q.3. What is oxyhaemoglobin?

Oxyhaemoglobin is a molecule formed by the binding of oxygen to haemoglobin, a protein found in red blood cells. It is responsible for transporting oxygen from the lungs to the rest of the body, where it is needed for cellular respiration.

Q.4. Why do roots of plants need to respire?

Roots of plants need to respire because they require energy to carry out various metabolic processes such as absorption of water and nutrients, synthesis of new cells, and maintenance of cell functions. Additionally, the roots are often located in areas of low oxygen concentration, so they need to respire anaerobically (without oxygen) to produce energy.

IV. Long Answer Type Questions

Fish respiration occurs through the gills. Gills are specialized respiratory organs in fish that are responsible for taking in oxygen and expelling carbon dioxide. They are located on both sides of the fish's head and are covered by a bony structure called the operculum.

As water flows over the gills, the gill filaments extract oxygen from the water and release carbon dioxide back into the water. The oxygen-poor blood from the fish's body flows over the gill filaments in the opposite direction to the water, allowing for the diffusion of oxygen from the water into the blood.

Each gill filament contains many tiny projections called lamellae that increase the surface area for gas exchange. The thin walls of the lamellae also help to facilitate the diffusion of gases.

Q.2. Describe how exchange of gases takes place inside the human respiratory system. 

The human respiratory system involves the exchange of gases between the body and the environment. Air is taken in through the nose or mouth and passes through the pharynx, larynx, trachea, and bronchi before reaching the alveoli, which are small air sacs in the lungs.

In the alveoli, oxygen from the air diffuses into the blood in the capillaries surrounding the alveoli. At the same time, carbon dioxide from the blood diffuses into the alveoli to be exhaled out of the body.

This exchange of gases occurs due to differences in concentration gradients between the air and blood. Oxygen diffuses from an area of high concentration in the air into an area of low concentration in the blood, while carbon dioxide diffuses from an area of high concentration in the blood into an area of low concentration in the air.

Q.3. What is the difference between aerobic and anaerobic respiration? Write the equations to show both the processes.

Aerobic and anaerobic respiration are two different types of cellular respiration. Aerobic respiration occurs in the presence of oxygen and involves the breakdown of glucose to produce energy, carbon dioxide, and water. The equation for aerobic respiration is:

Glucose + Oxygen → Carbon dioxide + Water + Energy

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

Anaerobic respiration, on the other hand, occurs in the absence of oxygen and involves the breakdown of glucose to produce energy and lactic acid or alcohol. The equation for anaerobic respiration in animals is:

Glucose → Lactic acid + Energy

C₆H₁₂O₆ → 2C₃H₆O₃ + Energy (ATP)

While anaerobic respiration in plants and yeast is:

Glucose → Ethanol + Carbon dioxide + Energy

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy (ATP)