Life Processes

BIOLOGY LIFE PROCESSES

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1. Life processes are the vital processes carried out by living organisms in order to maintain and sustain life. Molecular movements are essential to carry out various life processes.

2. Energy required to carry out different life processes is obtained through the process of nutrition.

3. Nutrition is a process of intake of nutrients such as carbohydrates, fats, proteins etc. by an organism

as well as the utilisation of these nutrients by an organism. 4. Depending on the mode of obtaining nutrition, organisms are classified as autotrophs or heterotrophs.

i. Autotrophs can prepare their own food from simple inorganic sources such as carbon dioxide and water. Examples: Green plants and some bacteria.

ii. Heterotrophs cannot synthesise their own food and are dependent on other organisms for obtaining complex organic substances for nutrition. Example: Animals.

Types of Heterotrophic Nutrition

Saprotrophic Nutrition

Parasitic Nutrition Holozoic Nutrition

An organism obtains its food from decaying organic matter of dead plants, dead animals and rotten bread etc. Example: Fungi

An organism derives its food from the body of another living organism without killing it. Example: Cuscuta

An organism takes complex organic food materials into its body by the process of ingestion. The ingested food is digested and then absorbed into the body cells of the organism. Example: Paramecium

6. Green plants prepare their food by the process of photosynthesis. They utilise CO2, H2O and sunlight, with the help of chlorophyll, giving out O2 as a by-product.

Chlorophyll

2 2 6 12 6 2SunlightGlucose

6CO 6H O C H O 6O+ → +



7. In the light reaction of photosynthesis, light energy is absorbed and converted to chemical energy in

the form of ATP. The water molecules are split into hydrogen and oxygen.

8. Carbon dioxide is reduced to carbohydrates in the dark phase of photosynthesis.

9. Plants carry out gaseous exchange with the surrounding through stoma.

10. In Amoeba, digestion occurs in the food vacuole, formed by the engulfing of food by its pseudopodia.



11. In humans, digestion of food takes place in the alimentary canal, made up of various organs and

glands.

12. In the mouth, food is crushed into small particles through chewing and mixed with saliva, which contains amylase for digesting starch.

13. On swallowing, food passes through the pharynx and oesophagus to reach the stomach. Gastric juice contains pepsin (for digesting proteins), HCl and mucus.

14. The liver secretes bile which emulsifies fat. 15. Pancreatic juice contains the enzymes amylase, trypsin and lipase for digesting starch, proteins and

fats, respectively. 16. In the small intestine, carbohydrates, proteins and fats are completely digested into glucose, amino

acids, fatty acids and glycerol. 17. The villi of the small intestine absorb the digested food and supply it to every cell of the body. 18. The undigested food is egested from the body through the anus. 19. During respiration, the digested food materials are broken down to release energy in the form of ATP.

20. Depending on the requirement of oxygen, respiration may be of two types:

i. Aerobic: Occurring in the presence of oxygen. ii. Anaerobic: Occurring in the absence of oxygen.



21. The end-product of anaerobic respiration in the muscles of human beings is lactic acid, and in yeast cells, ethanol and carbon dioxide are released. Carbon dioxide and water are released during aerobic respiration. A large amount of energy is released in aerobic respiration as compared to anaerobic respiration.

22. Terrestrial organisms use atmospheric oxygen for respiration, whereas aquatic organisms use oxygen dissolved in water.

23. In humans, inhalation of air occurs through the following pathway: 24. Nostrils � Nasal passage � Pharynx � Larynx � Trachea � Bronchus � Bronchiole � Alveolus 25. The alveoli of lungs are richly supplied with blood and are the sites where exchange of gases (O2 and

CO2) occurs between blood and the atmosphere.

26. In humans, the respiratory pigment haemoglobin carries oxygen from the lungs to the different tissues of the body.

27. The circulatory system is composed of the heart, blood and blood vessels which transport various

materials throughout the body.



28. The human heart has four chambers—two atria (right and left) and two ventricles (right and left). The

right half of the heart receives deoxygenated blood, whereas the left half receives oxygenated blood.

29. Ventricular walls are much thicker than atrial walls. 30. Arteries carry blood from the heart to different parts of the body, whereas veins deliver the blood back

to the heart. Arteries are connected to veins by thin capillaries, wherein materials are exchanged between the blood and cells.

31. Humans show double circulation and complete separation of oxygenated and deoxygenated blood. 32. Blood platelets are essential for clotting of blood at the place of injury and thus prevent blood loss. 33. The lymphatic system consists of lymph, lymph nodes, lymphatic capillaries and lymph vessels which

drain into larger veins. 34. In plants, water and minerals are transported through the xylem tissue, from the roots to the aerial

parts of the plant. The root pressure and transpiration pull are the major forces involved in pulling water up the xylem.

35. Translocation of food is carried out through the phloem tissue from the leaves and storage organs to

other parts of the plant. This process requires energy in the form of ATP. 36. During excretion, the harmful metabolic nitrogenous wastes generated are removed from the body.



37. In humans, a pair of kidneys, a pair of ureters, the urinary bladder and the urethra constitute the

excretory system.

38. Nephrons are the basic filtration units of the kidneys. They carry out filtration, selective reabsorption

and tubular secretion to form urine in the kidneys which is then passed out through the urethra via the ureters and urinary bladder.

39. Plants do not have an excretory system and carry out excretion in various ways such as transpiration,

releasing wastes into the surrounding soil, losing their leaves and storing waste materials in cell vacuoles and in old xylem.

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Life Processes