| Living organisms are continuously undergoing chemical | | | | low energy-containing compounds like carbon dioxide |
| reactions which gives rise to energy changes in their | | | | and water in the presence of sunlight and chlorophyll. |
| bodies. All these reactions and changes are termed | | | | As solar energy is necessary for photosynthesis, the |
| metabolism. Basically, metabolism consists of two | | | | process cannot occur at night due to the absence of |
| processes, the synthesis or building up of complex | | | | sunlight. The final products of photosynthesis are |
| body substances from simpler constituents and | | | | carbohydrates and oxygen. The former is distributed |
| energy, and the decomposition nor breaking down of | | | | to all parts of the plant. The latter is given off as a gas |
| these complex substances and energy. The first | | | | through the stomata back to the atmosphere in |
| process is known as anabolism and the second as | | | | exchange for the carbon dioxide that was taken in. the |
| catabolism. | | | | occurrence of photosynthesis in green leaves may be |
| One of the main characteristics of living organisms is | | | | demonstrated by experiments showing the absorption |
| the ability to feed. This is referred to as nutrition. | | | | of carbon dioxide, water and energy by the leaves, |
| Nutrition is therefore, the process of acquiring energy | | | | and the production of oxygen and carbohydrates. |
| and materials for cell metabolism, including maintenance | | | | Simple experiments can be set up to demonstrate the |
| and repair of cells and growth. In living organisms, | | | | giving off of oxygen by green plants, the formation of |
| nutrition is a complex series of both anabolic and | | | | carbohydrates (namely, starch) in leaves and the |
| catabolic processes by means of which food | | | | requirements of carbon dioxide, sunlight and chlorophyll |
| materials taken into the body are converted to | | | | for the formation of starch in green leaves. |
| complex body substances (mainly for growth) and | | | | Experiments in physiology involve the placing of |
| energy (for work). In animals, the food materials taken | | | | biological materials like plants and animals or parts of |
| in are usually in the form of complex, insoluble | | | | plants and animals under unusual conditions, e.g. jars, |
| compounds. These are broken down to simpler | | | | cages or boxes. If an experiments is set up to show |
| compounds, which can be absorbed into the cells. In | | | | the effects produced by the absence of carbon |
| plants, complex food materials are first synthesized by | | | | dioxide during the photosynthetic process, then the |
| the plant cells and then distributed to all parts of the | | | | result obtained from such an experiment can be |
| plant body. Here, they are converted to simpler, soluble | | | | argued as being partially due to the placing of the |
| forms, which can be absorbed into the protoplasm of | | | | biological material under unnatural experimental |
| each cell. The raw materials necessary for the | | | | conditions it is, therefore, necessary to set up two |
| synthesis of these complex food materials are | | | | almost identical experiments; one is placed under |
| obtained from air and soil in the plant's environment. | | | | normal conditions (the control experiment) where all the |
| All living organisms that cannot provide their own | | | | factors necessary for photosynthesis are present |
| energy supply by either photosynthesis or | | | | while the other (the test experiment) is placed under a |
| chemosynthesis are known as hetero strophes or | | | | condition where a single factor is eliminated or varied |
| hetero strophic organisms. Hetero strophic means | | | | while all the other factors are present. This enables the |
| feeding on others'. All animals are hetero strophes. | | | | experimenter to be sure that the result shown by his |
| Other organisms such as many types of bacteria, a | | | | test experiment is due to the eliminated or varied |
| few flowering plants and all fungi use this method of | | | | factor and not to the experimented set-up. Thus, the |
| nutrition. The way in which hetero strophes obtain their | | | | control experiment serves as a guide to ensure that |
| food varies considerably. However the way in which | | | | the conclusion obtained by the test experiment is not a |
| the food is processed into usable form within the body | | | | fallacy. |
| is very similar in most of them. But all green plants | | | | After certain proper experiments observation show |
| possess the ability to manufacture carbohydrates | | | | clearly that oxygen is released only when |
| from certain raw materials obtained from the air and | | | | photosynthesis occurs, i.e. during the day. No starch |
| soil. This ability is important not only to the plants | | | | can be formed if sunlight is absent although the other |
| themselves but also to animals, including man, which | | | | entire essential factors such as water, carbon dioxide |
| depend directly or indirectly on plants for food. | | | | and chlorophyll may be present. |
| Photosynthesis is the process whereby plants | | | | Photosynthesis the basic constituent of nutrition the unit |
| manufacture their foods through the use of energy | | | | of healthy living has played and is playing an essential |
| from the sun and available raw materials. It is the | | | | role to living organisms. The complex cellular structures |
| manufacture of carbohydrates in plants. It takes place | | | | of plants are built up from the primary product of |
| in the chlorophylls (i.e. green) cells of leaves and stems | | | | photosynthesis, namely, a simple carbohydrate like |
| only. These green cells contain chloroplasts, which are | | | | glucose. At this stage, it must be realize that, though |
| essential for the synthesis of food. All the raw | | | | much emphasis has been placed on photosynthesis, |
| materials required for photosynthesis, namely, water | | | | the process of protein synthesis is just as important as |
| and mineral salts from the soil, and carbon dioxide from | | | | the former. During protein synthesis, nitrogenous |
| the atmosphere have, therefore, to be transported to | | | | compounds absorbed by plants and in certain cases, |
| the chlorophylls cells, which are most abundant in | | | | phosphorus and others element, combine with glucose |
| leaves. | | | | to form the various plant proteins. |
| The tiny pores, or stomata, which usually occur greater | | | | Besides contributing to the synthesis of plants proteins, |
| numbers on the lower surfaces of most leaves, allow | | | | glucose is important also because it can be |
| gases from the atmosphere to pass into the tissues | | | | transformed into fats and oils after a series of |
| within. A stoma is an oval-shaped epidermal cells | | | | chemical reactions. It is also the primary product from |
| known as guard cells. Each stoma is actually the | | | | which other organic compounds are formed. |
| aperture of a sub-stomata air chamber. This is a large | | | | The importance of photosynthesis in all food cycles |
| intercellular air space, which lies adjacent to the stoma. | | | | cannot be overemphasized. Animals are unable to |
| It is continuous with other intercellular air spaces found | | | | make use of the sun's energy to synthesize |
| inside the leaf. The size of each stomata pore | | | | energy-rich compounds from simples easily-available |
| depends on the curvature of the guard cells flanking it. | | | | substances like water and carbon dioxide found in the |
| When the guard cells are full of water they become | | | | atmosphere around us, rather the ultraviolet rays from |
| swollen, or turgid, and consequently the pore opens. | | | | the sun causes some to living body; the melanin and |
| However, when the water level is low they become | | | | keratin it affects the color and strength of animals skin, |
| soft, or flaccid, and collapse, as the result, which the | | | | and some internal damages. From the rays, Therefore, |
| pores close. When the stoma is open air enters the | | | | it is fortunate that plants have the ability to use the |
| sub-stomata chamber and diffuses throughout the | | | | energy provided by sunlight to synthesize and store |
| intercellular air dissolves in the water, which surrounds | | | | energy-rich compounds upon which ultimately all forms |
| the cells. This solution of carbon dioxide then diffuses | | | | of animal life are dependent. |
| into the cells of the leaf, particularly the palisade cells. | | | | For his survival, man eats not only plant products like |
| Here, it is used by the chloroplasts for photosynthesis. | | | | fruits, vegetables and cereals, but also animals like |
| Water carrying dissolved mineral salts such as the | | | | cattle and fish. Cattle and other herbivorous animals |
| phosphates, chlorides and bicarbonate of sodium, | | | | depend entirely on plant life for their existence. While |
| potassium, calcium iron and magnesium, is absorbed | | | | certain fish are herbivorous, others have a mixed diet |
| from the soil by the roots. This soil water enters the | | | | and a large number are entirely carnivorous. |
| roots hairs by a process called osmosis the | | | | Carnivorous animals depend indirectly on plants for a |
| movement of water molecule from a region of lower | | | | living. Their immediate diet consist of smaller animals |
| concentration to a region of higher concentration | | | | which themselves must feed, if not entirely, then partly, |
| through a semi-permeable membrane. It is then | | | | on plants. Photosynthesis is the first step in all food |
| conducted upwards from the roots, through the stem | | | | cycles. |
| to the leaves by the xylem tissue. It is transported to all | | | | During the process of photosynthesis, carbon dioxide is |
| the cells, via the vein and their branches. | | | | removed from the atmosphere and oxygen is added |
| The chloroplasts contain the green pigment, | | | | to it. If this purification process did not exist in nature, |
| (chlorophyll) which gives the plants it color and capable | | | | soon the atmosphere would become saturated with |
| of absorbing light energy from sunlight. This energy is | | | | the carbon dioxide given out during the respiration of |
| used for one of the first essential steps in | | | | animals and plants and during decomposition of organic |
| photosynthesis; namely, the splitting of the water | | | | matter so that all life would gradually come to a stop. |
| molecule into oxygen and hydrogen. This oxygen is | | | | Without photosynthesis, there will be no nutrition. And if |
| liberated into the atmosphere. The hydrogen | | | | there is no nutrition, living thing will not exist. And if |
| components are used too reduces carbon dioxide, in a | | | | there's no living things in the earth the earth will still be |
| series of enzymes and energy consuming reactions, to | | | | without form and entirely void. There will be no for |
| form complex organic compounds like sugars and | | | | living things to do work if photosynthesis does not |
| starches. | | | | court. I wonder what will be the fate of living things |
| During photosynthesis high energy-continuing | | | | today or sometime, when photosynthesis comes to a |
| compounds like carbohydrates are synthesized from | | | | stop. |