Current Affairs 7th Class

     Nutrition in Animals   Nutrition in animals is quite different from the nutrition in plants. The animals are heterotrophs because they cannot prepare their own food. They depend on plants and other animals for their nutritional requirement. Animals in fact, gather food from different sources. Big animals require huge amount of food for their nutritional needs.   Look at the flow chart of nutrition in animals  

     Digestion in Animals   Digestion of food in animals include mainly four stages, that is, ingestion, digestion, absorption and excretion. The process of taking food inside the body is called ingestion. The process, by which the food is broken down into small pieces by the digestive juice, is called digestion. The digested food is absorbed by the intestine, which is called absorption. Undigested food and waste materials from the body are released in the form of stool and urine. This process is called as excretion.    Look at the following picture of digestive system of herbivorous and carnivorous Animal:                                     Digestive system of a cow                                                           Digestive system of a lion              Digestive system of a Herbivorous Animal Digestion of food begins in the mouth of a herbivorous animal. Ingested food is first broken down into small pieces by teeth. Tongue mix it with saliva, secreted from salivary glands. The partly digested food from mouth is transported to stomach through esophagus. The stomach of a cow is divided into four chambers, as shown in the given picture. The first and largest part of the stomach is rumen. There are certain bacteria, present in the rumen part, help in digesting cellulose carbohydrates. Thus food is partially digested in rumen, which is known as cud. When the cattle are in rest, the cud (partially digested food) is slowly brought back into mouth for re-chewing. The completely chewed food then go to the small intestine, through the other chambers of stomach. The abomasum part of the stomach secretes hydrochloric acid and digestive enzymes. The omasum part of the stomach absorbs water. The small intestine receives digestive enzymes released by pancreas and liver. Here, in small intestine, complete digestion and absorption of digested food takes place. The food is then send to large intestine, where the remaining water is absorbed .The undigested food is transported further to be expelled out of body.              Which among the followings acts as producer in food chain?          (a) Insects (b) Plants                            (c) Owls (d) Caterpillars (e) None of these                                                          Answer: (b)           Which one of the following is true for cud? (a) Digested food (b) Undigested food (c) Partially digested food (d) All of these (e) None of these   Answer: (c)

       Digestive system of Human   Human digestive system is consisted of many parts. Each of the parts has a distinct function to perform.   Look at the following picture of human digestive system                Oral or Buccal Cavity Our mouth is the first organ of the digestive system, which is known as oral or buccal cavity. When we eat food, the teeth part of our mouth breaks food into small pieces. Oral cavity contains a muscular organ called tongue. It helps in mixing the food with saliva secreted by salivary gland. Thus digestion of food begins in the mouth.              Esophagus Esophagus is a tube like structure, which brings food from mouth to stomach. No action on food takes place in the esophagus.              Stomach Stomach is the largest part of the alimentary canal. It secretes mucus, hydrochloric acid and digestive juices. Hydrochloric acid kills harmful bacteria that enter through mouth with food. The partially digested food then goes from stomach into small intestine.             Small Intestine The length of small intestine is about 7.5 meters. It is called small intestine because of its narrow piped shape. The wall of small intestine secretes a juice called intestinal juice. Intestinal juice breaks down the carbohydrate into glucose and protein into amino acid. The complete digestion and absorption of digested food takes place inside the small intestine. Small intestine receives digestive juice from pancreas and liver. Pancreas secretes pancreatic juice. It breaks down the fats into fatty acid and proteins, carbohydrates into its simplest form. Liver also secretes enzymes called bile. Bile is temporally stored inside gallbladder and it helps for the digestion of fat. Villus of small intestine absorbs the digested food and send it to all the parts of the body.            Large Intestine The large intestine consists of cecum and colon. The main function of large intestine is to absorb extra water from the indigestible food and then pass it to the rectum. The feces (indigestible food) is stored in the rectum for a certain period and then the stored feces is expelled out of body.               A Which one of the following acids is secreted by stomach for the digestion of food? (a) Sulphuric acid (b) Hydrochloric acid (c) Amino acid (d) All of these (e) None of these   Answer: (b)          Liver is an important part of the digestive system. The liver of human body secretes which one of the following digestive juice? (a) Bile more...

     Chemical Reactions   The chemical reaction is the process in which two substances combine and form a new substance. Chemical reactions are widely used for the formation of desired substances. The substances, which are initially involved in the chemical reaction are called reactants. And the substance, which we get after completion of chemical reaction, is known as products.   Look at the following chemical reaction of Hydrogen and Oxygen     In the above picture, molecules of hydrogen and oxygen combine together to form molecules of water.                Types of Reactions Types of reaction depend on nature of the combination of reactants and energy released or absorbed by the resulting chemical, after the reaction. There are three types of reaction, which have been discussed below:            Direct Combination or Synthesis Reaction In the synthesis reaction, two molecules combine chemically to form a more complex molecule and energy of the resulting molecule is stored in its bonds. Proteins are built from amino acid and whole energy is stored in it. Example: Iron and sulfur combine to form iron sulfide.                                Decomposition Reactions In this reaction, the bigger molecule is broken into smaller molecule and energy is released. The electrolysis of water into hydrogen and oxygen is the decomposition or analysis reaction.                  Exchange Reaction In this reaction, reactants exchange and replace their parts to form new compounds. When sodium chloride and silver nitrate are mixed together, sodium nitrate and silver chloride are formed.   The combination of zinc and hydrochloric acid forms zinc chloride and it replaces the hydrogen..                 Acid and Base Reaction When in a chemical reaction, acid and base are involved as a reactants, the reaction is called acid and base reaction. The reaction between hydrochloric acid and sodium hydroxide produces sodium chloride and water. It is an example of acid base reaction. The chemical equation is as follows,                       The word reactant is derived from which one of the following process, in which a new substance is formed? (a) Mathematical process (b) Hydraulic process (c) Chemical process (d) All of these (e) None of these   Answer: (c)          Which one of the following types of reaction is involved for the formation of iron sulfide from iron and more...

      Chemical Bonding   Atoms of the elements lose and gain electrons to form new substances. The process, by which they form the new substances, is called chemical bonding. An atom of a substance is made up of three fundamental particles, i.e. electrons, protons and neutrons. Out of three particles, protons and electrons are charged whereas neutron does not possess any charge. Protons are positively charged and electrons are negatively charged. Two like charges repel each other and two unlike charges attract each other. Negatively charged electrons orbiting the nucleus, whereas protons are present in the nucleus. The atoms, which lose electrons in a chemical bonding is called positive ions or cations. The atoms, which gain electrons are called negative ions or anions. For example, reaction between sodium (Na) and chlorine  leads to the transfer of electrons from Na to  to form cations and  anions. The bonding of atoms of the chemicals mainly depends on their charges. The force between the two charged particles is called electromagnetic force. The force between atoms allows the formation of chemical compound. The strength of the chemical bonding of the two atoms is the actual strength of electromagnetic force between them.     Look at the Following Picture of Formation of Salt from the Reaction of Sodium and Chlorine                                                                                                 Sodium metal                                    Chlorine Gas Formation of slat                                   Table salt                                                                     Atomic structure of sodium                                Atomic structure of chloride                                                    Sodium loses one electron                                          Sodium chloride (table salt)       In the picture (1), sodium loses its one valance electron and gives it to chlorine. In the picture (2) the atoms of the resulting elements are positively charged sodium ions and negatively charged chlorine ions. The bond, between sodium and chlorine is called ionic bond. Because, in this reaction, one reactant is in metallic form and another is in nonmetallic form. The atomic number of sodium is 11 and the valance electron in outer most orbits is 1. The atomic number of chlorine is 17 and the number of valance electrons in outer most orbits is 7. For the classification of atomic structure of known elements a table has been introduced, which is called periodic table.   Periodic Table In the periodic table the elements have been arranged according to their atomic number. The atomic number of an element is the number of protons in its nucleus. The columns of periodic table signify the group of the elements. The elements more...

     Dissolution of Solid   In a dissolution process, two substances are required. One is called solvent and the other is solute. The substance, which dissolves in another substance, is called solute and the substance in which the solute dissolves, is called solvent. In this process the quantity of the solvent is greater than the solute. The dissolution of salt in water is dissolution of solid in liquid. The dissolution of salt in water is due to the attraction of positive and negative charges. Water is the chemical compound of hydrogen and oxygen. Two molecules of hydrogen and one molecule of oxygen forms a molecule of water.   Look at the following picture of dissolution of salt in water   The dissolution of sugar in water is also dissolution of solid in liquid. The solid can also be a solvent and its solutes are gas, liquid and solid. The dissolution of hydrogen in palladium is the dissolution of gas in liquid.               When sugar is dissolved in water, sugar water solution is formed. Which one of the following is solute particles in the solution? (a) Milk (b) Sugar (c) The mixture of milk and sugar (d) All of these (e) None of these   Answer: (b)           Which one of the following is known us universal solvent? (a) Methane (b) Mercury (c) Water (d) All of these (e) None of these   Answer: (c)

     Chemical Equations   Chemical equation is the symbolic representation of a chemical reaction. The reactants of the reaction are represented on the left hand side of the equation and products are represented on right hand side. The representation of reactants in an equation are in symbolic form. Plus sign between the reactants separates every reactant. On the right hand side, every product is also separated by plus sign. The arrow mark (read as yield) between the reactants and resulting elements is used to denote the net forward reaction. Following symbol is used between the reactants and products. = Symbol is used to denote a stoichiometric relation.  Symbol is used to denote the chemical reaction in both directions or reversible reaction.  Symbol is used to denote equilibrium. The physical state of the chemicals are denoted in parenthesis after the symbol of the chemicals. The letter s in parenthesis (s) denotes the solid state of the chemicals. The letter l in parenthesis (I) denotes the liquid state of the chemicals and letter g in parenthesis (g) denotes the gaseous state of the chemicals. The letter aq in parenthesis (aq) denotes the aqueous solutions. The Greek letter delta (a) above the arrow denotes the energy in the form of heat is added to the reaction. The letter hv above the arrow is used to denote the energy in the form of light is added to the reaction.   Look at the following picture of chemical equation Reactants                                             Products     In the above picture, methane and oxygen are reactants and carbon dioxide and water are products. An arrow mark between the reactants and the products is used to denote the forward direction of the reaction. In the above reaction, one molecule of methane and two molecules of oxygen react together and form two molecules of water and one molecule of carbon dioxide.   Look at the following picture of chemical equation   Reactants Products In the picture above, the coefficient of the molecule is shown. Reactants in the given equation are hydrogen and oxygen whereas product is water. Look at the following chemical equation     In the above chemical equation, N, is symbolic representation of nitrogen, and 2 in front of N represent the number of atoms. H is the symbolic representation of hydrogen and 3 behind H is representing the number of molecule of hydrogen. In the parenthesis, g represents the gas form of hydrogen. Arrows in the both= direction indicates the reversible reaction. 1000°C (Ferric oxide above the arrow) indicates the necessity of resistive components during the reaction. The product of the reaction is ammonia in the form more...

         Surrounding Affects the Living Things   Our earth is the third planet and only one capable of supporting life in the solar system. The distance between the Sun and the Earth is about, 14, 95, 65, 1,39 km. It varies slightly during the year. The variation of distance between the Earth and Sun is due to the angle of the earth axis, relative to the Sun. There are various kinds of species living on the Earth. All living organisms require food to survive and they obtain food from plants and animals. Therefore, all living organism, directly or indirectly depend on plants. The natural resources such as plants, animals, minerals, water and air are of two types, renewable resources and nonrenewable resources. Renewable resources are replaced by natural process. The water cycle is an example of renewable resource. Oxygen is obtained from plants and called renewable resource. Other renewable resources are soil, solar energy, wind, etc. Non- renewable resources cannot be replaced by natural process and its reserve is decreased due to uses. None renewable resources are formed by physical and chemical reaction and it takes long time. The nonrenewable resources are, metals, coal, petroleum, natural gas, etc.

     Introduction   Plants require water, sunlight, carbon dioxide and minerals for making their food. These nutrients in the plants are converted into glucose by the process of photosynthesis. The growth rate of a plant mainly depends on the availability of nutrients in the soil on which the plant grows. Lack of nutrients in the soil cause improper growth and shorter life-span of the plant. There are two modes of nutrition’s in plants. These are autotrophs and heterotrophs. Heterotrophic plants are further classified into three groups, saprophytes, parasite and insectivores. The living organisms, which make their own food by photo syntheses with the help of chlorophyll present in their body, have autotrophs mode of nutrition. The living organisms, which are unable to make their own food and depend on the autotrophs for their nutritional needs, is said to have heterotrophs mode of nutrition. In this chapter, we will study about the nutrition in different types of plants.         Nutrition in Green Plants Green plants are capable of making their own food by the process of photosynthesis, due to the presence of a pigment called chlorophyll in the plants. Leaves of a plant absorb carbondioxide and trap Sun rays which act as reactants in the process of photosynthesis. Different parts of a plant perform different functions. Root of a plant absorbs water and minerals from the soil . Water and minerals absorbed by the root of the plant are transported throughout the plant through its stem, which is called transportation or conduction. Stem of a plant gives support to the plant to stand on the soil. The xylem and phloem tissues in the stem help the plant to transport essential substances from one part to another.   Look at the following picture to understand the process of photosynthesis in a plant:                    The following reaction takes place between the reactants during the process of photosynthesis.        (Carbon dioxide)     (Water)   Chlorophyll    (Carbohydrates)    (Oxygen)               Function of Leaves Leaves are the part of a green plant where the process of photosynthesis occurs.           Absorption of Solar Energy through the Leaves of the Plant Leaves absorb solar energy and carbon dioxide from air.   Look at the following picture of the structure of chlorophyll in a leaf:      Chlorophyll transfers absorbed solar energy into the centre of the cell where, exchange of electrons between the water molecules and solar energy takes place. The result of the exchange of these electrons is the production of oxygen gas and hydrogen ions. ATP (adenosine triphosphate) is an enzyme. The function of ATP is to transport the energy within the cell for metabolism which is produced during the exchange of these more...

         Nutrition in a Non Green Plants (without chlorophyll)   We have studied about the involvement of chlorophyll in the process of photosynthesis. Whole process of photosynthesis depends on the presence of chlorophyll in the plant. The process of photosynthesis in general condition is not possible without chlorophyll. However, there are many plants in our surrounding which do not have chlorophyll such as, cuscuta, monotropa, etc. They all depend on heterotrophic mode of nutrition such as, saprophytic, parasitic and insectivorous.              Saprophytes Saprophytic plants live and grow on dead and decaying organic matters. It secretes enzyme to break down the complex organic compound into its simpler form for the absorption.   Look at the following picture of non-green (saprophytic) plants:                Monotropa           Parasitic The plant which absorbs nutrition from its host plant is called parasite. Parasitic plants do not have either chlorophyll or leaves. Hence, they cannot perform the process of photosynthesis. They absorb nutrients made by the host plant and is fully dependent on host plant to meet that need.   Look at the following picture of parasitic plant:                Cuscuta                 Insectivorous Plant Some plants eat insects are called insectivorous plant. Pitcher of a pitcher plant traps insects and internal structure of pitcher break down the insects into small pieces which is digested by digestive juice secretes by the pitcher. Look at the following picture of pitcher plant:     Pitcher Plant              Symbiotic Relationship When two plants live together and share their food and shelter for each other, these relationship between the plants are known as symbiotic relationship. Fungi and roots of almost all vascular plants form mutualistic association called mycorrhizae. Look at the following picture of lichen on a pine tree:    Symbiotic plants                   What is the function of root of a green plant? (a) It absorbs water and mineral from soil (b) It absorbs oxygen from air (c) It absorbs carbon dioxide from air (d) All of these (e) None of these   Answer: (a) Explanation Root of a green plant absorbs water and mineral from soil.           Which one of the following is an insectivorous plant? (a) Cactus plant (b) Babool plant (c) Pitcher plant (d) All of these (e) None of these   Answer: (c) Explanation Out of the given plants, pitcher plant is more...