The functional unit of lung is:

(i) The basic life processes common to all living organisms are movement, nutrition, reproduction, respiration, transport, and excretion.

(ii) Animals can move from one place to another, while plants can only move parts of their body, such as roots, leaves, and flowers. Non-living things cannot move by themselves.

2. Nutrition:

(i) The process of intake of nutrients by an organism and utilisation of the nutrients by organisms is called nutrition.

(ii) Autotrophic nutrition involves the intake of simple inorganic materials from the environment (water, carbon dioxide) and using external energy like the sun to synthesise complex, high-energy organic material.

(iii) Heterotrophic nutrition involves the intake of complex material prepared by other organisms. It includes animals and fungi.

3. Autotrophic nutrition:

(i) Chloroplast of plant cells is the active site for photosynthesis.

(ii) Light reaction occurs in the grana of the chloroplast. Absorption of light energy, conversion of the light energy to chemical energy, and splitting of water molecules into hydrogen and oxygen occurs in light reactions.

(iii) Dark reaction occurs in the stroma of a chloroplast. Reduction of carbon dioxide to carbohydrates takes place in this process.

(iv) Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. Other materials like nitrogen, phosphorus, iron, and magnesium are taken from the soil.

(v) Gaseous exchange usually takes place through stomatal opening and closing. The guard cell's wall swell when water flows into them, causing stomatal pores to open. Similarly, the pore closes if the guard cells shrink.

4. Nutrition in human beings:

(i) In human beings, the food eaten is broken down by various steps along the alimentary canal, and the digested food is absorbed in the small intestine to be sent to all cells in the body.

(ii) The small intestine is the site of the complete digestion of carbohydrates, proteins, and fats. It receives the trypsin for digesting proteins and lipase for breaking down emulsified fats.

(iii) Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest. Hence, carnivores like tigers have a shorter small intestines than herbivores like cows.

(iv) Gradual softening of enamel and dentine is called tooth decay or dental caries. If untreated, microbes may invade the pulp. It causes inflammation and infection.

(v) During the process of respiration, complex organic compounds such as glucose are broken down to provide energy in the form of ATP. ATP is used to provide energy for other reactions in the cell.

5. Respiration:

(i) Respiration may be aerobic or anaerobic. Aerobic respiration makes more energy available to the organism.

(ii) Aerobic respiration is the oxidation process of food in the presence of oxygen.

(iii) The end products of this type of respiration are carbon dioxide, water, and energy.

(iv) Aerobic respiration involves the oxidation of food in various steps. These are glycolysis, the formation of acetyl Co-A and the Krebs cycle. 

(v) Anaerobic respiration is a process of respiration that takes place in the absence of oxygen.

(vi) It involves alcoholic fermentation, the anaerobic breakdown of sugar into carbon dioxide and energy.

(vii) Lactic acid fermentation is the incomplete breakdown of sugar into lactic acid into carbon dioxide and energy.

(viii)Three types of respiratory organs in animals are trachea as in insects, gills as in aquatic animals, and lungs in terrestrial animals.

(ix) The respiratory system in human beings comprises the nose, larynx, trachea, bronchi, bronchioles, alveoli, and lungs.

(x) The lungs are the primary respiratory organs of man where the actual gas exchange occurs. The breathing process involves the inhalation and exhalation of gases.

(xi) During inspiration, the muscles of the diaphragm and external intercostal muscles contract.

(xii) During expiration, the muscles of the diaphragm and external intercostal muscles relax.

(xiii)The gases are transported by blood, oxygen from the lungs is carried to the body tissues, and carbon dioxide is eliminated.

6. Transportation in human beings:

(i) In human beings, the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the RBCs. Carbon dioxide is more soluble in water and hence is mostly transported in the dissolved form in our blood.

(ii) In human beings, the transport of material such as oxygen, carbon dioxide, food, and excretory products is a function of the circulatory system. The circulatory system consists of the heart, blood, and blood vessels.

(iii) Blood pressure refers to the force that blood exerts against the wall of a vessel. This pressure is much greater in arteries than in veins. The average systolic pressure is about $120 mm$ of Hg and diastolic pressure of $80 mm$ of Hg.

(iv) Blood pressure is measured by sphygmomanometer.

(v) Heartbeat refers to one complete contraction and relaxation of the heart. The heart pumps out our blood to the arteries about $70$ to $72$ times per minute.

(vi) Stethoscope is used to listen to heartbeats.

(vii) Lymph is another type of fluid and helps in transportation. Lymph carries digested and absorbed fat from the intestine and drains excess fluid from extracellular space back into the blood.

7. Transportation in plants:

(i) In highly differentiated plants, the transport of water, minerals, food, and other materials is a function of the vascular tissue, which consists of the xylem and phloem.

(ii) The upward movement of water and minerals from roots to different plant parts is called the ascent of sap

(iii) Transport of food in plants takes place utilization of energy. Thus, unlike the transport through the xylem, it is a form of active transport. The flow of substances through the phloem occurs in both directions, i.e., upward and downward, unlike the xylem in which the transport of water and minerals takes place in an upward direction.

(iv) Transpiration is the process of loss of water as vapour from aerial parts of the plant. This process creates a vacuum which creates a suction called transpiration pull. 

8. Excretion:

(i) The human excretory system comprises a pair of kidneys, a pair of ureters, urinary bladder, urethra.

(ii) The kidney has three main parts: The cortex, medulla, and pelvis. 

(iii) Leading from the pelvis is a tube called the ureter, which carries urine to the bladder. 

(iv) Kidneys are actually made up of thousands of tiny tubules called nephrons. 

Urine produced in the kidneys passes through the ureters into the urinary bladder, where it is stored until it is released through the urethra.

Blood which enters the kidney through the renal artery contains unwanted waste substances as well as some useful substances.

(iv) Nephrons remove the waste substances such as excess water and also re-absorb certain useful substances like glucose that are needed by the body and put it back into the blood.

The process of expulsion of the urine to the outside is called urination.

(iii) In case of kidney failure, an artificial kidney can remove nitrogenous waste products from the blood through dialysis.

(iv) Normally in a healthy adult, the initial filtrate in the kidneys is about $180$ litre daily. However, the volume excreted is only a litre or two a day because the remaining filtrate is reabsorbed in the kidney tubules.

9. Excretion in plants:

(i)Gaseous waste excretion in plants occurs through stomatal pores on leaves and ‘lenticels’ in stems and is released into the air.

(ii) The metabolism in plants also generates organic by-products, which are stored in different forms in different parts.

(iii) The gums, oils, latex, resins, etc, are some waste products stored in plant parts like bark, stems, leaves, etc.

(iv) The plants get rid of these wastes by shedding leaves, peeling off bark, and felling fruits.

(v) Waste products can also be stored in the form of oil produced from orange, eucalyptus, jasmine, latex from the rubber tree, papaya tree, and gums from acacia. These may be excreted into the soil.