SCIENCE- NOTES NAME: RESPIRATION IN ORGANISMS STD.VII DIV: Q1. Draw the diagram of human respiratory system and explain the function of the following parts: i. Nasal cavity ii. Trachea iii. Lungs iv. Bronchioles v. Alveoli i. Nasal cavity: It is the cavity which receives air from the nostrils and passes it into the trachea. ii. Trachea: It is also known as the wind pipe. It is guarded by an opening known as glottis, which gets further covered by epiglottis thus keeping the opening of food pipe separated from the wind pipe. Trachea later divides into two main sub branches called as bronchi which enter into the lungs. iii. Lungs: Lungs are organs of respiration, which are located in the thoracic cavity on either sides of the heart. The right lung is divided into three lobes and the left lung into two lobes. They are spongy due to the presence of blood capillaries filled with blood and air spaces. 1
iv. Bronchioles: Each bronchus which is the part of trachea, divides further into tiny branches called bronchioles. They are the passages to carry air to the terminating regions known as alveoli. v. Alveoli: Alveoli are tiny air sacs (appearance like a bunch of grapes) which are made up of single layer membrane. They are involved in exchange of respiratory gases (O 2 and CO 2 ). Q2. Explain the mechanism of breathing in human beings. Breathing which is a physical process involves inhalation and exhalation. A. INHALATION: It is characterised by downward movement of diaphragm and the chest cavity moves out which allows the air to enter into the lungs due to the space created. B. EXHALATION: During exhalation the ribs move downward and inward. This causes reduction in the size of the chest cavity and the air is pushed out. Diaphragm move upward and comes back to its normal dome shaped structure. Q3. Explain the process of exchange of gases in insects such as a cockroach. i. The diagram (A) given below shows the position of small openeings known as spiracles on the insect s body. (A) (B) 2
ii. iii. Diagram (B) shows the tubular system which runs along the body of the cockroach. These tubular structures are known as trachea. Trachea open through the spiracles which will help cockroach to exchange the respiratory gases. Q4. Justify the statement that composition of inhaled and exhaled air is not the same. INHALED AIR EXHALED AIR 1. Inhaled air is rich in oxygen as compared to exhaled air. 2. Water vapour in inhaled air varies. 3. Temperature of inhaled air is approximately equal to room temperature. Exhaled air has more carbon dioxide because the oxygen is used up for oxidation of food and carbon dioxide is formed. Exhaled air is saturated with water vapour. Temperature of exhaled air is same as that of body temperature. Q5. Differentiate between aerobic and anaerobic respiration including the chemical equations. AEROBIC RESPIRATION ANAEROBIC RESPIRATION 1. It occurs in presence of oxygen Occurs in absence of oxygen. 2. Carbon dioxide and water are the end products. 3. Releases relatively large amount of energy. 4. It occurs in plants, animals and human beings. End products are- carbon dioxide and alcohol or lactic acid. Energy released is less than aerobic respiration. Carried out by certain bacteria like lactic acid bacteria and fungus like yeast. 5. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy C 6 H 12 O 6 CO 2 + Alcohol + Energy Q6. Explain the following term: i. Respiration: It is a vital process in which oxygen rich air is inhaled to oxidise the food to release energy in the body cells and carbon dioxide rich air is exhaled out form the body. 3
Q7. Frogs can breathe through their skin. List two features of their skin which facilitate this gaseous exchange? Frogs respire through their skin during hibernation. i. Skin of frogs is soft and moist ii. It is supplied with large number of blood capillaries. Q8. i. Label part A and part B in the above diagram. Part A- Gills Part B- Operculum ii. Explain how these two parts are helpful in respiration in fish. Operculum is the covering of gills. Gills are special organs for respiration. Operculum allows the water to enter and pass over the gills to give oxygen and receive carbon dioxide and pass out from under the operculum. Q9. Complete the following table: Organism Breathing organ Characteristics of the breathing organ Amoeba or Paramecium Cell membrane Diffusion of oxygen and carbon dioxide through the cell membrane. Earthworm Skin Skin is moist which helps in exchange of respiratory gases. Tadpoles Gills - 4
Birds Lungs Air filled cavities are present near the lungs which make the body of the birds lighter. Plants Stomata It consists of two guard cells which control the opening and closing of stoma to take in oxygen. Lenticels These are small openings on the bark of the trees (woody stems). Q10. Give reasons: i. Inhaled oxygen is supplied to the body through the blood. Red blood cells of blood have a protein known as haemoglobin. It binds with oxygen and acts as a carrier to provide oxygen to all the parts of the body. ii. We get cramps when we perform a rigorous physical exercise. During a physical exercise body muscles utilise a lot of energy for which they respire fast, but they do not get sufficient oxygen. Under such conditions, anaerobic respiration takes place which results in the formation of lactic acid and its accumulation in the muscles. Thus we get cramps due to lactic acid accumulation in our muscles. 5