Respiration In Organisms Class 7 Notes | YoLearn.ai

Introduction to Respiration

Every living organism, from the smallest bacterium to the largest animal, requires energy to perform its life functions. This energy is derived from the food we eat. The process by which this food is broken down in the cells of an organism with the release of energy is called cellular respiration. It's not just about breathing in and out; it's a biochemical process that happens at a cellular level. During respiration, the glucose (sugar) present in the food is broken down, often using oxygen, to produce carbon dioxide, water, and most importantly, energy in the form of ATP (Adenosine Triphosphate). Without this continuous supply of energy, cells cannot function, and life cannot be sustained. Therefore, understanding respiration is key to comprehending the very basis of life.

Types of Respiration: Aerobic vs. Anaerobic

The Human Respiratory System

The human respiratory system is a complex network of organs and tissues that help us breathe. The process of breathing involves taking in oxygen-rich air and exhaling carbon dioxide-rich air. Air first enters the body through the nostrils or mouth, passes through the nasal cavity, and then down the pharynx (throat) and larynx (voice box). From there, it enters the trachea (windpipe), which divides into two tubes called bronchi. Each bronchus enters a lung. Inside the lungs, the bronchi further divide into smaller tubes called bronchioles, which end in tiny air sacs called alveoli. It is in the alveoli where the exchange of gases (oxygen and carbon dioxide) takes place between the air and the blood. The diaphragm, a large, dome-shaped muscle located at the base of the chest cavity, plays a crucial role in breathing by contracting and relaxing, causing the lungs to expand and contract.

Breathing vs. Cellular Respiration

Respiration in Other Organisms

Key Points to Remember

• All living organisms require energy obtained through respiration.
• Cellular respiration is the process of breaking down food in cells to release energy.
• Aerobic respiration requires oxygen and releases a large amount of energy, producing carbon dioxide and water.
• Anaerobic respiration occurs without oxygen, releases less energy, and produces alcohol/CO2 (in yeast) or lactic acid (in muscles).
• Muscle cramps during strenuous exercise are due to the accumulation of lactic acid from anaerobic respiration.
• The human respiratory system involves nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, and lungs.
• The diaphragm's contraction and relaxation are essential for the mechanism of breathing.
• Breathing is the physical intake and exhalation of air, while respiration is the cellular energy-releasing process.
• Plants exchange gases through stomata (leaves), lenticels (stems), and root hairs (roots).
• Earthworms respire through moist skin, insects through spiracles and trachea, and fish through gills.

Important Definitions

Respiration

The biochemical process occurring in cells where food (glucose) is broken down to release energy.

Breathing

The physical process of taking in oxygen-rich air (inhalation) and giving out carbon dioxide-rich air (exhalation).

Aerobic Respiration

A type of respiration that uses oxygen to completely break down glucose, releasing a high amount of energy.

Anaerobic Respiration

A type of respiration that occurs without oxygen, partially breaking down glucose and releasing less energy.

Cellular Respiration

The process within individual cells where glucose is broken down to produce energy, usually in the form of ATP.

ATP (Adenosine Triphosphate)

The primary energy currency of the cell, used to power various cellular activities.

Diaphragm

A large, dome-shaped muscle located at the base of the chest cavity, crucial for regulating breathing.

Stomata

Tiny pores predominantly found on the surface of plant leaves, facilitating gas exchange with the atmosphere.

Gills

Specialized respiratory organs in aquatic animals like fish, adapted to absorb dissolved oxygen from water.

Trachea (Windpipe)

The main air tube that extends from the larynx into the chest, branching into bronchi to carry air to the lungs.

Exam Tip for Respiration In Organisms

Students often confuse 'breathing' with 'respiration'. Remember, breathing is a mechanical process of gas exchange, while respiration is a chemical process of energy release inside cells. Always clearly define both and explain their differences, especially their location (respiratory organs vs. cells) and purpose (gas exchange vs. energy production). Pay close attention to the end products of aerobic vs. anaerobic respiration, as these are common multiple-choice questions or short answer questions. Practicing drawing the human respiratory system can also be very helpful for diagram-based questions.

Check Your Knowledge

• Q: What is the primary purpose of respiration in living organisms? A: The primary purpose of respiration is to release energy from food (glucose) to fuel various life processes.
• Q: Name the two main types of respiration and state one key difference. A: The two main types are aerobic respiration (requires oxygen) and anaerobic respiration (does not require oxygen).
• Q: What causes muscle cramps after heavy exercise? A: Muscle cramps are caused by the accumulation of lactic acid, a by-product of anaerobic respiration in muscle cells when oxygen supply is insufficient.
• Q: How do plants respire? A: Plants respire through stomata on leaves, lenticels on stems, and through their root hairs, exchanging oxygen and carbon dioxide with the environment.

Frequently Asked Questions