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A CLASS-X EPISODE – 1 STATE SYLLABUS LIFE PROCESSES PHOTOSYNTHESIS The subject of Biology deals with the study of plants and animals. From the ancient to modern world, since the origin of life on this planet earth to the present day,evolution has played a major role in evolving new species. Every new species that evolved and those that survived and perpetuated had more advanced characters and phenomena. However the basic and fundamental features and metabolic processes have not changed. This is the best evidence of evolution. All organisms have some basic processes. These processes are important for the sustenance and perpetuation of an organism. They are termed as Life processes. They can be classified into three main groups. 1) Processes for Maintenance a) Digestion b) Respiration c) Transport d) Excretion 2) Control and Co-ordination a) Nervous system b) Sense organs c) Endocrine system 3) Reproduction We have learnt in the earlier classes that there are unicellular and multicellular organisms. While the unicellular organisms remain as a single cell, the multicellular organism begins life as a single cell the zygote. This zygote multiplies and adds more cells. Then it grows into an adult. For all the above processes the organisms requires raw materials. When we build a house we need a number of materials. Can we create them out of nothing? 1 In the same way the organism has either to produce or synthesize or procure the material required for growth from other sources. The organism require food for the raw materials. These raw materials have to be transported to the regions of growth. For example for the synthesis of protein the organism requireds amino acids. Very few amino acids can be synthesized in the body. Rest of the amino acids have to be procured from food. The proteins in the food are broken down in the body to amino acids in the process of digestion. These amino acids are transported to tissues by the transport system. In the cells they are used to synthesize proteins. During this process the wastes are eliminated by the excretory system. For all the above activities energy is required. For production of energy oxygen is required. This is looked after by the respiratory system. All the above activities have to be under control and proper coordination. This is looked after by the constituents of control and coordination system. Only when all the systems are functioning normally the organism grows and develops. How do organisms obtain energy from food? We know that plants of AUTOTROPHS. They prepare their own food by the process of PHOTSYNTHESIS. The sun light plays a major role in Photosynthesis. In this process simple inorganic elements like carbon, hydrogen and oxygen are converted to complex organic substances. Photosynthesis is the only process that utilizes energy from sun to produce food for millions of organisms. This is only process which adds oxygen to the atmosphere. This photosynthesis is the basic life process for the sustenance of organisms in general and man in particular. Plants not only provide food to us but also other useful products like wood for shelter and fossil fuels like coal, wood and petroleum products are products of plants. Respiration is important in releasing energy. It is stored in carbohydrates which in turn are synthesized during photosynthesis. These processes prove the co-ordination between the systems. 2 Photosynthesis as a life process:How do plants synthesize their own food? Plants produce their own food by a process called photosynthesis. Hence they are called AUTOTROPHS. Where does this process occur? Green leaves which have chlorophyll, the green pigment, are primary organs for photosynthesis. 3