Shikshakendra

Nervous system in Human Beings All the parts of the nervous system are structurally connected with one another and functionally integrated, but for sake of our convenience they can be divided into the following three parts: (i) Central Nervous system   It consists of two parts:   1. Brain   2. Spinal 1. Brain       Brain is enclosed and well protected in the cranial cavity or brain box of skull.  The brain is surrounded by three membranes called meneings. This fluid protects brain from external shocks and mechanical injury. Structure of brain     Human brain is a whitish, symmetrical structure that weighs about 1200-1400g and forms about 80% of central nervous system.   It is divisible into three regions: (A) Fore Brain      It is the largest part of human brain that forms 4/5th of the brain. It is divided into three parts: (a) olfactory lobes :   These are a pair of poorly developed, club...

  Stimuli The changes in the environment or environmental factors to which the organisms respond and react are called stimuli. Coordination The working together of the various organs of an organism in a systematic manner so as to produce a proper reaction to the stimulus, us called coordination. System functions by the release of chemical messengers -- the hormones and is called endocrine system and the other works by the Conduction of nerve impulses like the Conduction of an electric current and is called nervous system. ANIMALS-- NERVOUS SYSTEM The system by which controls and coordinates all the activities of various parts in response to external and internal stimuli by the Conduction of nerve impulses is called nervous system. Sense organs Name of receptors     stimulus    location Photoreceptors             light             Eyes Phonoreceptors          ...

 Excretion in plants Like animals plants also produce a number of waste products but they have no special organs for waste removal. They remove their waste products by different methods. Some of these methods of waste removal are as under:  • carbon dioxide water are wastes produced during Respiration. Oxygen is produced during photosynthesis.  All these wastes are removed through the stomata present on the surface of leaves or lenticels present on stem. Carbon dioxide is excreted by plants during night while oxygen is excreted by plants during day time. Water is excreted from plants in the form of water vapour by the process of Transpiration. It is excreted at day time as well as night. • some of the waste products collect in the leaves, barks and fruit of the plants. • plants get rid of these wastes by shedding off leaves, peeling of barks and falling fruits. • some of the plant wastes like excess salts get stored in the fruits in the form of solid bodies called raphide...

            Excretion The process of elimination of waste products mainly the nitrogenous wastes from the body is known as  excretion. The removal of wastes it is necessary to maintain the water and salt percentage of the blood by osmoregulation which is defined as the process of maintaining the right amount of water, salt and proper ionic balance in the body.  Both excretion and osmoregulation go side by side and the organs responsible for these processes form the urinary system or excretory system. Need for excretion The excretory processes play an important role in maintaining: • The internal environment of the body constant, i.e., homeostasis. • Osmotic relationship between blood, lymph and tissue fluids. • Acid base balance in the body. Excretion in Human Beings All body organs which help the animal in excretion of soluble nitrogenous waste product, excess of salts, excess of water and other metabolic wastes collectively constitute excretory ...

     Transportation in plants  Plants require a number of substances such as nitrogen, phosphorus, iron, calcium, magnesium, etc. for building their bodies. These substances are present in soil and are required even by parts situated at the top of plants. Transportation in plants is carried out by two complex tissues - xylem and phloem.  Xylem transports water and minerals from root to the aerial parts while phloem transports prepared food from leaves to the other parts of the plant.  1. Transport of water Water with its dissolved inorganic mineral nutrients is called sap the upward transport of water from the root to the aerial parts of the plants like branches, leaves, flowers, etc. is known as ascent of sap. The ascent of sap takes place through xylem, a complex tissue. Xylem vessels, xylem tracheids, xylem parenchyma and xylem fibres are the various elements of xylem.  The ascent of sap takes place through xylem vessels and xylem tracheids in flowe...

Lymphatic System Lymph and its associated parts constitute lymphatic system. It consists of: 1. Lymph        Lymph is a colourless or straw coloured fluid connective tissue. It is another medium for circulation in human body. Source of lymph is blood. Some amount of plasma, proteins and blood cells escape into the  intercellular spaces present in tissues through the pores present in blood capillaries to form lymph or tissue fluid. 2. Lymph capillaries           Interwoven with the blood capillaries are present lymph capillaries which are blind at one end. They have very thin walls. Lymph flows in lymph capillaries. 3. Lymph Vessels           Lymph capillaries join to form lymph Vessels. Lymph Vessels resemble the veins in structure but have thinner walls and more valves. The smaller lymph Vessels join to form larger vessels, which unite to form two main lymphatic vessels or trunks. These vessels open into ve...

 Transportation Body of unicellular organism such as Amoeba is in direct contact with the environment. They can take the required substances such as oxygen, food, etc. Directly from the environment by the process of diffusion through the body surface. Transports of oxygen, minerals, etc. to all the cells/tissues and waste products like carbon dioxide, urea, etc. from the cells/tissues to the excretory organs for their removal from the body. This takes place by different methods in plants and animals called transport system. Transportation in Human Beings In humans, substance like oxygen and minerals are transported to the body cells and metabolic wastes such as carbon dioxide are removed from cells by extracellular fluids.  These fluids keep on circulating in the body and helps in transportation of various substances.  This flow of extracellular fluid in the body is called circulation Circulatory system or transport system in human consists of :  • circulatory medium...

  Respiration in plants The plants get energy by the process of Respiration. During Respiration the plants exchange oxygen and carbon dioxide. so, oxygen and carbon dioxide are called respiratory gases. Respiration differs from that of animals. • All plant parts perform Respiration individually While animals respire as a unit.  • The transport of gases in plants from one part to another is very little as compared to animals. • The rate of Respiration in plants is much slower as compared to animals  Exchange of gases in roots  The roots of a plant take the oxygen needed for Respiration from the air present in between the soil particles by the process of diffusion. The root hairs are the extensions of the epidermal cells. Oxygen diffuses into root hairs and passes into other cells of the root cells move out into the soil by the process of diffusion. Exchange of gases in stems  The oxygen from air diffuses into stem of a herbaceous plant through stomata and reaches...

 Respiration The proceess by which organisms obtain energy by utilising food in the cells is called respiration. •In this process Of respiration, food reacts with oxygen to release energy. Carbon dioxide and water are also produced during the process.  • The energy released during the process is stored in the form of ATP( adenosine triphosphate)  The intake of molecular oxygen and elimination of carbon dioxide produced are also parts of respiration. Thus respiration may be defined as the process which involves: • Intake of molecular oxygen by breathing, • use of molecular oxygen in cells for Oxidation of glucose, • production of carbon dioxide, water and energy, • storing energy in the form of ATP and  • elimination of carbon dioxide and water by breathing. Breathing and Respiration The mechanism by which organisms inhale oxygen from the environment and exhale carbon dioxide into the environment is termed as breathing.  Diff. b/w breathing & Respiration ...

 Nutrition in Humans  The nutrition in humans beings takes place through human digestive system.  The human digestive system consists of the alimentary canal and its associated glands. The alimentary canal has following parts in sequence:  mouth, buccal cavity, oesophagus, stomach, small intestine and large intestine.  The human alimentary canal is about nine metres long tube, extending from mouth to anus. The glands associated with the digestive system are salivary glands, liver and pancreas.  The various steps of Nutrition in humans are: 1. Ingestion:    In humans, a special organ for the ingestion of food is present which is called mouth. 2. Digestion: In humans the digestion of food begins in the mouth itself. Mouth leads to buccal cavity which contains teeth ( incisors, canines, premolars & molars).  The teeth help in physical digestion. The buccal cavity receives saliva from three pairs of salivary amylase. The human saliva contains...

HETEROTROPHIC NUTRITION Word heterotrophic is derived from two Greek words -- Hetero meaning different  and trophe means nutrition .  In this type of Nutrition, the organisms cannot prepare it's own food buy is dependent on other organisms for its food requirements.  Heterotrophic nutrition is further divided into following 3 types:  1. Saprophytic Nutrition Sapro means rotten. I'm this type of Nutrition, the organisms get their food material from dead decaying organic matter.  Eg: mushroom, bacteria etc. 2. Parasitic Nutrition In this type of Nutrition, an organism, may be plant or animal, depends on other living organisms is called parasite and the other organism on which parasites depends is called host.  Eg: Tapeworm, ticks, lice etc. ‌‌ 3. Holozoic Nutrition The animals consume the entire food by ingestion and then digest it by converting it into simpler substances. Eg: Amoeba, cow,. buffalo How do organisms obtain their Nutrition? • Nutrition in Amoeb...

  ~ Image Formation in Lenses Using Ray Diagrams  We can represent image formation by lenses using Ray diagrams. Read diagrams will also help us to study the nature, position and relative size of the image formed by lenses. For drawing Ray diagrams in lenses, a like of spherical mirrors, we consider any two of the following rays -  i) A ray of light from the object, parallel to the principal axis, after refraction from a convex lens coma passes through the principal focus on the other side of the lens, as shown in figure. 10.13 (a).                                              Fig 10.13 (a) In case of a convex lens, the ray appears to diverge from the principal focus located on the same side of the lens, as shown in fig. 10.13 (b).                                   ...

~ The Refractive Index You have already studied that a ray of light that travels obliquely from one transparent medium into another will change its direction in the second  medium. The extent of the change in direction that  takes place in a given pair of media is expressed in  terms of the refractive index,the "constant"  appearing on the right-hand side of Eq.(10.4).  The refractive index can be linked to an important  Physical quantity, the relative speed of  propagation of light in different media. It turns  out that light propagates with different speeds in  different media. It turns out that light propagates  with different speeds in different media. Light travels fastest in vacuum with speed of  3×10/8  power m s/-1. In air, the speed of light is only marginally Less, compared  to that in vacuum. It  reduce considerably in glass or  water.  The  value of the refractive index for a given pair of m...