These DAV Class 7 Science Notes and DAV Class 7 Science Chapter 7 Notes – Respiration in Organisms act as excellent revision resources, particularly in preparation for board exams.
Respiration in Organisms Class 7 DAV Notes
→ Respiration: The process in which organisms convert sugars into biochemical energy by using oxygen. At the end of respiration, energy is produced which is utilized to carry out various life processes. Additionally, carbon dioxide is released at the end of respiration.
Respiration happens in two main parts:
(a) Exchange of Gases: Organisms follow different methods for exchange of gases. Oxygen enters an organism and carbon dioxide comes out.
(b) Cellular Respiration: In this step, oxygen is utilized by cells to breakdown sugars so that energy can be released.
→ Types of Respiration: Respiration is of two types, viz. aerobic and anaerobic respiration.
→ Aerobic Respiration: This type of respiration takes place in the presence of oxygen. Plants and animals use this method of respiration.
→ Anaerobic Respiration: This type of respiration takes place in the absence of oxygen. Anaerobes are the organisms which use this method of respiration. Such organisms do not require oxygen to produce energy. Fungi and some of the bacteria use this method of respiration.
→ Yeast is a fungus which uses anaerobic respiration. Due to this, yeast is used in making alcohol and in making breads. Yeast is used for fermentation of batter for idli and dosa.
→ Anaerobic respiration in muscles: Anaerobic respiration also happens in our muscles; when there is extra demand of energy by the muscle cells. When we run too fast, our leg muscles need more energy. Anaerobic respiration happens in the muscle cells to provide extra energy. As a result of this, lactic acid is released in muscles. Due to lactic acid, we feel cramp and pain in the leg muscle. The pain subsides after some rest.
→ Respiration in Plants: Plants also respire to release energy. Plants take in oxygen through minute pores on the surface of roots, stems and leaves. The pores on the leaves are called stomata. Oxygen enters through these stomata and carbon dioxide comes out during respiration. The oxygen goes to different cells where it is utilised to breakdown glucose. The process of respiration can be written as following equation.
Glucose + Oxygen → Carbon dioxide + Water + Energy
→ Respiration in Animals: The mode of respiration in animals is same as in plants. The method for exchange of gases is different. Different animals use different organs for exchange of gases.
- In small organisms; like amoeba and hydra; oxygen enters and carbon dioxide exits by a simple process called diffusion.
- In earthworm and leech, exchange of gases happens through skin. The skin of such animals is always moist and is richly supplied by blood.
- Fish, prawn and crab use gills for exchange of gases. With the help of gills, they can take in oxygen which remains dissolved in water.
- Insects use tracheae for respiration. A trachea is a fine tube and there is a network of many tracheae. Each trachea opens at the surface of body through a minute pore. Such pore is called spiracle.
- Animals; like crocodile, birds and mammals; use lungs for exchange of gases.
→ Respiration in Humans: Human beings have a well developed respiratory system. Lungs is the main respiratory organs in humans. Following are the main parts of the human respiratory system:
- Nasal Passage: The nose opens into a passage; called nasal passage.
- Pharynx: The nasal passage opens into a tube-like part; called pharynx.
- Larynx: Pharynx opens into larynx. Larynx is also called the voice box.
- Trachea: Larynx opens into trachea. Trachea is made up of cartilaginous rings. Cartilage prevents the trachea from collapsing in the absence of air.
- Bronchi: Trachea divides into two branches; called bronchi.
- Alveoli: Bronchi further divide into branches and sub-branches inside the lungs. The sub-branches end up in air sacs; called alveoli. Alveolus is the location where exchange of gases takes place.
- Lungs: Lungs are balloon-like organs which can expand to take in air and contract to push out air.
→ Breathing Rate: The number of times a person breathes per minute is called breathing rate.
→ Mechanism of Breathing: The process of breathing is divided into two phases, viz. inspiration and expiration. The process of taking in air is called inspiration and the process of giving out air is called expiration. The movement of lungs is controlled by diaphragm and the rib cage. Diaphragm is a membrane between chest cavity and abdomen.
→ Inspiration: During inspiration, the muscles around the rib cage contract and lift the ribs upward and outward. This lowers the diaphragm. As a result of these changes, the chest cavity expands and with that the lungs also expand. With the expansion of lungs, air moves inside the lungs.
→ Expiration: During expiration, the muscles around the rib cage expand and rib cage is lowered. This pushes the diaphragm up. As a result of these changes, the chest cavity contracts and with that the lungs also contract. With the contraction of lungs, air moves outside the lungs.
→ Transport of Oxygen in Human Body: In the alveoli, oxygen mixes with blood and carbon dioxide comes out of blood. Oxygen is transported to different parts of the body through blood. Blood contains a red pigment called haemoglobin. Haemoglobin is the carrier of oxygen.
→ Respiration: The process of breaking down glucose (in living organisms) to obtain energy.
→ Aerobic respiration: This happens in the presence of oxygen.
→ Anaerobic respiration: This happens in the absence of oxygen.
→ Fermentation: The process of obtaining alcohol or lactic acid in food items with the help of anaerobic respiration.
→ Inspiration: Taking in oxygen rich air.
→ Expiration: Giving out carbon dioxide rich air.
→ Transpiration: Removal of water vapour from plants (through stomata and lenticels).
→ Asthma: A disease of respiratory system in which the person suffers from bouts of breathlessness.
→ Pneumonia: Inflammation of lungs.
→ Haemoglobin: A red pigment present in blood. This pigment carries oxygen.
→ Lenticels: Small pores on the surface of woody branches in plants. Exchange of gases happens through lenticels.
→ Stomata: Small pores on surface of leaves. Exchange of gases happens through stomata.