CHAPTER AT A GLANCE
1. Introduction: Living organisms require oxygen, water and food in every cell of their various tissues to sustain life. The various processes essential for maintenance of life are called life processes. These include nutrition, respiration, circulation, excretion and reproduction. Organisms obtain energy from food to perform these life processes which are essential for survival.
2. Nutrition: Nutrition is the process bywhich an organism procures its nourishment, the supply of nutrients required by its body and cells to stay alive.
(i) Types of nutrition
(a) Autotrophic nutrition: Autotrophs contain chlorophyll pigment, which is capable of trapping and fixing the solar energy. This energy is utilised for synthesising food from the raw materials like carbon dioxide, water and a few minerals, e.g. green plants, Euglena.
(b) Heterotrophic nutrition: A heterotrophic organism is a consumer
which derives its nutrition from other organisms, e.g. all animals, mostly bacteria and fungi.
(c) Parasitic nutrition: These animals live on or inside the body of the host and obtain their food, e.g. tapeworm, Cuscuta etc.
(d) Saprophytic nutrition: In this type ofnutrition, animals depend on dead decaying organic matters, e.g., fungi, bacteria.
(e) Holozoic nutrition: In this type ofnutrition, the complex organic food material is taken into its body by the process ofingestion, the ingested food is digested and then absorbed into the body cells of the organism, e.g. man, Amoeba.
(ii) Nutrition in plants: Green plants are autotrophic and synthesise their
own food by the process of photosynthesis.
Photosynthesis: Photosynthesis is the process by which chlorophyll containing plants manufacture their own energy sources (simple sugars) from intracellular chemical reaction of carbon dioxide and water in presence of sunlight and chlorophyll
Chlorophyll, present in chloroplasts, is a green colour pigment.
CO2 is obtained through stomata, which opens and closes by the turgidity of guard cells.
3. Nutrition in human beings
- The process of nutrition in human beings is called as digestion. Human beings consists of specialised organs for the process of digestion, called as digestive system.
- Human digestive system is made up of two parts- alimentary canal and digestive glands.
- Alimentary canal, also called digestive tract, is a pathway by which food enters the body and solid wastes are expelled.
- It includes mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus.
- Digestive glands are the glands which bring about digestion process. These include salivary glands (present in buccal cavity), gastric glands, intestinal glands, liver and pancreas.
Respiration is a complex process which includes breathing i.e. exchange of 02 and CO2 and oxidation of food to release energy. Oxidation of glucose
takes place during respiration. It occurs in the mitochondria of cells.
(i) Types of respiration
(a) Aerobic respiration: Aerobic respiration is the process of producing cellular energy involving oxygen. Cells breakdown food in the mitochondria in a long, multistep process that produces roughly 36 ATP.
(b) Anaerobic respiration: In anaerobic respiration, glucose breakdown
without oxygen and produces 2ATP. It takes place in certain bacteria and yeast which release energy in the absence of 02.
(ii) Respiration in animals: Every cell in animal requires oxygen to perform cellular respiration.
• Cellular respiration is the process by which animals take in 02 and exchange it for CO2 and O as waste products.
• Animals have specific organs for respiration like skin, lungs, gills.
• Air travels through the following path:
The process of breathing is divided into two phases:
(a) Inspiration is a process bywhich atmospheric air reaches lungs and volume of thorax increases.
(b) Expiration is the process by which foul air oflungs is released. It occurs by relaxing intercoastal muscles and diaphragm.
• Respiratory pigments take up oxygen from the air in the lungs and carry it to tissues.
• In human beings respiratory pigment is haemoglobin which remains present in RBC.
• Emphysema, asthma, pneumonia, bronchitis are the respiratory disorders
(I) Transportation in human beings
• Transportation is a process in which substances are absorbed in one part and move to the other parts of the body.
• The blood is responsible to transport food, oxygen and waste materials in human bodies.
• Erythrocytes, leucocytes, blood platelets are three types of blood cells.
• Circulatory system delivers nutrients and oxygen to all cells in the body. It includes the heart and the blood vessels running throughout the body.
• Heart is situated in the thoracic cavity between two lungs. Heart is made up of cardiac muscles which works continously.
• Normal heart rate is 72/minute.
• On contraction; systolic phase is 120 mm ofHg and on relaxation diastolic phase is 80 mm ofHg.
• Karl Landsteiner discovered blood groups A, B and AB.
• ‘AB‘ is known as universal recepient as it can receive blood from all other groups.
• ‘0’ is known as universal donor as it can donate blood to all other groups.
• Double circulation in man: The circulatory system of man is called double circulation as the blood passes through the heart twice in one complete cycle of the body. It involves two circulation:
(i) Pulmonary circulation: It begins in the right ventricle which expels the blood into the pulmonary trunk. The blood flowing into the vascular system of the lungs, becomes oxygenated and returns to the heart (left atrium) through pulmonary veins.
(ii) Systemic circulation: This circulation is maintained by the left ventricle which sends the blood into the aorta.
(II) Transportation in plants
• It is the process of transporting water, minerals and food to all parts of the plant body.
• Xylem and phloem are conducting tissues of plants. The loss of water in the form of vapours from the leaf to the atmosphere is called as transpiration.
• Transport of food from leaves to other parts of the plant is called
translocation, which is carried out by phloem.
(i) Excretion in animals
• The removal of unwanted waste materials from the body is called
• The process of maintaining the right amount of water and proper ionic balance in the body is called as osmoregulation.
(ii) Excretion in human beings
• Excretory system of human beings consists ofa pair of kidneys, a pair ofureters, urinary bladder, and urethra.
• Artificial kidney is used when natural kidney begin malfunction or stop working.
(iii) Excretion in plants
• Oxygen is waste product of photosynthesis in plants. Plants get rid of excess of water by transpiration. Waste products may be stored in leaves that fall off.
• Many waste products are stored as resins and gums in plants.