10th Biosciences LIFE PROCESS

 Notes prepared by

 Ashaq Hussain Bhat

 Teacher School Education

 Department

 Jammu And Kashmir

Photosynthesis. 

 The process by which plants manufacture their own food material from CO, and H2O inpresence of sunlight and chlorophyl is called photosynthesis. The general reaction involved in photosynthesis can be represented as:

6CO2 + 6H2O------chlorophyll----->- C6H12O6 + 602

                                   sunlight

The overall equation of photosynthesis is currently accepted as:

6CO2 + 12H20---------sunlight------>C6H12O6 + 602 + 6H2O.

                            chlorophyll

The extra glucose is changed into another food called starch, which is stored in the leaves of plant. 

The photosynthesis takes place in following 

3 steps:

i) Absorption of sunlight energy by chlorophyll.

ii) Conversion of light energy into chemical energy and splitting of H2O into H2 and O by light energy

(iii) Reduction (addition of hydrogen) of CO2 by hydrogen to form a carbohydrate such as glucose   using chemical energy. 

  The raw materials needed for photosynthesis are

( i) Carbon dioxide (CO2): Land plants take CO2 from the atmosphere through the stomata.  and make their food.  Aquatic plants use CO2 that is present in a dissolved state in Water.  Plants do not carry out the process of photosynthesis at night.

 ( ii) Water (H20): It is absorbed by the root of the hair and transported to the photosynthetic organs through  xylem tissues.  Water is the only source of oxygen released during the process of  photosynthesis.

 ( iii) Chlorophyll: It is the photosynthetic apparatus in which photosynthesis occurs.  They are  located in the green parts of a plant, particularly in the mesophyll cells of a leaf.  Chlorophyll contains    four pigments, chlorophyll a, chlorophyll b, xanthophyll and carotene.  Of these, chlorophyll  it is found in all photosynthetic plants that develop oxygen and is involved in energy transfer.    Chloroplasts are also called the kitchen of the cell.  The chloroplast consists of granum and stroma.  Light  the photosynthesis reaction takes place in the granule and the dark reaction in the stroma.

 ( iv) Sunlight: The sun is the main source of energy and is used by plants.  Chlorophyll can absorb    violet, blue, and red components of visible light.  But the rate of photosynthesis is high in red, medium in blue and null in green light.  Photosynthesis also takes place in artificial sources of light

Site of Photosynthesis

Photosynthesis does not occur in all the cells of green plants. It occurs only in those cells which possess the green coloured plastids, called   chloroplasts (Fig.). Chloroplasts are not found in the upper and lower epidermis of green leaf. They occur in mesophyll cells that occupy the space between upper and lower epidermis. The mesophyll is differentiated into palisade and spongy parenchyma in most of the leaves. The green cells of mesophyll (i.e., palisade and spongy parenchyma) are living chlorenchymatous cells which possess a large number of chloroplasts. The chloroplasts of higher plants are discoid, ellipsoidal or biconvex lens shaped and measure about 4-6 micrometer in diameter. They can be seen easily under high power of a light microscope (compound microscope). But the finer details of chloroplasts can be observed  only under an electron microscope. The complete process of photosynthesis, including light phase and dark phase, occurs inside the chloroplast. In fact, there are green coloured grana embedded in liquidy hyaline stroma. The light phase occurs in grana and the dark phase occurs in stroma.Over

Explain the mechanism of photosynthesis?

  Photosynthesis is completed in two steps: 

(i) Light reaction

 (ii) Dark reaction

 ( i)Light reaction The entire process of photosynthesis occurs within the chloroplasts and   The raw materials needed for the process are CO, and H2O.  These raw materials become   into carbohydrates in the presence of light.  The first step of the process starts when the light falls.  on green leaves.  The pigment chlorophyll present in chloroplasts absorbs visible light and  after absorption it creates such a condition that the water breaks into hydrogen protons (H"),  electrons (e) and gives off molecular oxygen (O2).  This is called photolysis.  So the photolysis  of water is the first step of photosynthesis in which molecular Oz develops.  This O2 enters  the atmosphere.  The electrons and protons released by the photolysis of water are consumed in   the production of assimilative power in the form of NADPH and ATP (ie, reduced nicotinamide  adenine dinucleotide phosphate and adenosine triphosphate).  This entire process  uses light energy in the photolysis of water, the evolution of molecular oxygen (02) and  the synthesis of assimilative power has been assigned as the light reaction of photosynthesis.  Is  The passage occurs in the granum part of the chloroplast.

 ( ii) Dark reaction: 

The assimilative power generated in the light reaction of photosynthesis is  used in the next step where carbon dioxide from the atmosphere is used in the production of   carbohydrate.  This step is discovered in detail by Calvin, Benson and Basham in the year 1953.   It is a cyclic process, which occurs in the stromatic part of the chlorophyll, which is totally enzymatic. process and has been termed as the dark reaction of photosynthesis.  biochemistry    reactions that occur one after another in the form of a cycle that uses the power of assimilation   light reaction and convert CO2 into carbohydrates (CoH120.), it is called dark reaction or calvin   cycle.  The general equation of the Calvin cycle is as follows:

  6CO2 + 6 ribulose bisphosphate + 18 ATP + 12 NADPH                   

C6 H12O6 + 6 ribulose bisphosphate + 18 ADP +18PI+ 12 NADP

Factors Affecting Photosynthesis

The rate of photosynthetic process is affected by several external (environmental) and internal factors.

These factors are :

1. Light

3. Carbon dioxide

4. Water.

2. Temperature

1. Light. The ultimate source of light for photosynthesis in green plants is solar radiation (i.e., radiation  coming from sun). Out of the total solar energy reaching to the earth, only a very small portion (about 2%) intensity (e.g. during cloudy days), the rate of photosynthesis is also low. Increase in light intensity causes is used in photosynthesis. Light varies in intensity, quality (wave length) and duration. Under low light increase in the rate of photosynthesis up to a certain limit. At very high light intensity, the photosynthesis is decreased due to photo-oxidation of the constituents (solarization). The quality of light also affects photosynthesis. Green pigments chlorophylls absorb mostly the blue and the red regions of the spectrum. They reflect green light. Therefore, photosynthesis is high in blue and red light. Photosynthesis does not occur in green light.

2. Temperature. The rate of photosynthesis increases by increase in temperature upto 40°C. Above this temperature, there is a decrease in the photosynthesis. Similarly, low temperature also inhibits photosynthesis  The temperature affects photosynthesis by affecting the activity of enzymes. We know that the dark reaction of photosynthesis involves several enzymes. These enzymes function at a specific range of temperature. Low temperature lowers the activity of enzymes and high temperature causes inactivation of enzymes.

3. Carbon dioxide. Carbon dioxide is present in the atmosphere in the concentration of 0.033% by volume. It is really a low concentration for photosynthesis. Thus, the rate of photosynthesis increases by increasing the concentration of CO2 in the atmosphere if the light and temperature conditions are not limiting. At the same time, very high concentration of CO, becomes toxic to plants and inhibits photosynthesis.

4. Water. Water is an essential raw material in photosynthesis. This rarely acts as a limiting factor because less than 1% of the water absorbed by a plant is used in photosynthesis. However, the rate of photosynthesis is lowered if the plants are inadequately supplied with water. Under water deficient conditions the stomatal apertures remain closed to reduce the loss of water by transpiration. As a consequence, the entry of CO2 is also stopped into the leaves.

      Compensation point.

          The rate of photosynthesis is not constant throughout the day.  Your rate is affected by the amount of light.  It increases with increasing light intensity and decreases with   decrease in light intensity.  During the early hours of the morning or late at night, when the rate of    photosynthesis becomes equal to the rate of respiration, so there will be no net exchange of    gases between the plant body and the surrounding environment.  The intensity of the light where    there will be no net gas exchange between the plant body and the environment    environment and the rate of photosynthesis is equal to the rate of respiration, it is called   compensation point There is no loss or gain of carbon dioxide at this stage.

                     ______________________

              Respiration and its                                    types  

Respiration is defined as a biochemical process taking place inside a cell at body  temperature in which oxygen is utilised to oxidise food and energy is liberated along with  carbon dioxide and water vapours. The reaction involved in respiration can be represented as

C6H12O6 +602------> 6CO2 + 6H2O + energy(686 kilocalories/2870 KJ/36 ATP).

There are two types of respiration:

1. Aerobic respiration 
2. Anaerobic respiration.

(i). Aerobic respiration: When respiration takes place in presence of oxygen, it is termed as  aerobic respiration. It is found in majority of plants and animals. The reaction involved in  follows:

aerobic respiration is:

                 ( In cytoplasm( glycolysis)       In mitochondrion (kerb's cycle) 

Glucose----->2(pyruvicacid)------>6CO2+ 6H2O+energy(36ATP).

  No oxygen needed                      oxygen is needed

(ii) Anaerobic respiration. When respiration takes place in absence of oxygen, it is termed as  anaerobic respiration. It is found in yeast,  bacteria and parasitic worms. The reaction involved  in anaerobic respiration is:

              Glycolysis                           fermentation

Glucose->2(pyruvicacid)-->ethyl alcohol +  CO2+ Energy(2ATP)

                    No oxygen needed                              in absence of oxygen.

i.e: C6H12O6--->2CO2+2(C2H5OH) +56 kcal.......in yeast cells.

                                               ethyl alcohol

In certain bacteria and parasitic worms, glucose is metabolised to lactic acid without use of 02 and without formation of carbon dioxide,

C6H12O6------ ->2( CH3CHOCOOH) + ENERGY(in muscles of human beings).

                          (Lactic acid)

DIFFERENTIATE BETWEEN 

COMBUSTION AND RESPIRATION

Respiration

(i)It is a biological process occurring in living cells.

(II) In this process food material is  oxidised in stepwise manner.

(III) It occurs at ordinary temperature.IV) It is an enzyme catalysed process.

(V) The energy is stored in the form of  chemical

energy.

Combustion

(i) It is a physical process ad does not  occur in living cells.

(ii) The substrate is oxidised at random.  During this process there is sudden

(iii)release of energy and a sudden rise in  temperature.

iv) It is a non-enzymatic process. 

v)The energy released is lost in the form of heat.

Breathing and Respiration

Breathing :-is a kind of ventilation in which the organisms take oxygen from the environment and release carbon dioxide, In higher animals (mostly in mammals), breathing is regarded as rhythmic movement of muscles and skeleton in order to increase the gaseous exchange across respiratory surface. 

 Respiration :-is a much more complex process that occurs inside the living cells.It is the oxidation of respiratory substrate (mainly glucose) in the cells resulting in the release of carbon dioxide and energy. This respiration involves release of energy in the form of ATP.

EXCHANGE OF GASES IN PLANTS

  Because aerobic respiratory tract requires the presence of oxygen, aerobic organisms have  Procedures to ensure a constant supply of  oxygen.  We've seen this photosynthetic process Green plants need carbon dioxide and release oxygen.  This exchange of gases takes place through stomata.  Similarly, the exchange of gases through respiration (ie, intake of O2 and emission of CO2) also takes place through Stomata. During the day, O2 can be used for aerobic respiration .  At night, when there is no photosynthesis, O2 is used and CO2 is eliminated by stomata.  In fact, plants release CO2 at night when there is no photosynthesis and release O2 during the day. 

Plants have no special means of transporting gases.  Gases move completely through diffusion.  Large and interconnected intercellular spaces in plants ensure that all cells are in contact with air.  Because   Plants are stable in nature, they do not require much energy, so the rate of respiration is Relatively slow.

 Respiration in plants?

 Like animals, plants also need energy. The plants get this energy by the process of respiration. The respiration in plants involves the exchange of oxygen and carbon dioxide which are called respiratory gases.  Diffusion alone can supply all the cells of the plants with as much oxygen as they need for respiration. Diffusion occurs in the roots, stems and leaves of the plant.

(i)Respiration in roots: The roots (root hair) of a plant take the oxygen from the air present in between the soil particles by the process of diffusion. The root hairs are in contact with the air in the soil. Oxygen diffuses into root hair and reaches all the other cells of the root for respiration. Carbon dioxide gas produced during the process moves out through the same root hair by the process of diffusion.

(ii) Respiration in stems: The oxygen from air diffuses into the stems of a herbaceous plant through stomata and reaches all the cells for respiration. The carbon dioxide gas produced diffuses out into the air through the same stomata. In hard and woody stems, the bark has lenticels for gaseous exchange. The oxygen diffuses into the stem of a woody plant through lenticels and reaches all the cells of stem. The carbon dioxide gas produced follows the same path. 

(iii)Respiration in leaves: The leaves of a plant have tiny pores called stomata. The exchange of respiratory gases in the leaves takes place by the process of diffusion through stomata. Oxygen from air diffuses into a leaf and reaches all the cells. The carbon dioxide produced during respiration follows the same path. 

Respiratory organs in different organisms

 The respiratory organs found in different animals are designed in such a way to suit their habitat. Following are the organs which act as respiratory organs in  Different animals:

 (i) General body surface.  In lower organisms such as protists, sponges , protozoa,and hydra etc. exchange of gases takes place through the body surface by simple diffusion.

( i)Skin or Epidermis:- In some animals such as annelids and amphibians which live  In semi aquatis habitai, skin acts as respiratory organs.  This type of respiration in which  Exchange of gases occurs through the skin is called cutaneous respiration.

 (iii)Trachea (Air tribes):- Terrestrial arthropods such as insects, millipedes  have evolved a complex system of whitish shining, inter communicating air  tubes called trachea.  The exchange of gases with the help of trachea is termed as tracheal  rvespiration

 (iv)Gills:- Aquatic animals such as prawns, mussels, fishes and tadpoles breathe in   water through their mouth and force it to pass the gills where the dissolved oxygen is taken up by blood 

(V) Lugs:- Land animals namely reptiles.  birds and mammals breathe air by respiratory organs called lungs.

RESPIRATORY SYSTEM IN HUMAN BEINGS

           Respiratory system of Human beings is divided into two main parts

(I) Respiractory tract or Conducting passage 

(II) respiratory organ  or the lungs

(I) Respiractory tract :-It consists of nose, nasal cavity, pharynx, larynx, traches, primary Bronchi

(a) Nose:- Nose has two openings called nostrils for the entry of air inside the respirator system. It has hair on its inner surface to check and clean the inhaled air. It prevents the entry of dust particles, The nostrils open into a cavity called nasal cavity 

(b) Nasal cavity: It consists of a large irregular cavity divided by a septum. The base of  the skull forms the roof of nasal cavity and the roof of the mouth forms the floor of the nose cavity. The inhaled air is warmed up to the body temperature and is also moistened by the mucous. Then the cleaned and warmed air is sent further

(c) Pharynx: It is a short, vertical tube about 12cm long behindbuccal cavity. The food and air  passages cross here. It is divided into three parts: Nasopharynx, Oropharynx, Laryngopharynx. 

Laryngopharynx leads into two tubes windpipe or trachea and food pipe Oesophagus

(iv) Larynx: It is the sound box, it produces sound. It is situated between the phary and trachea. It is prominent in males after puberty and clearly visible externally. A part of protrudes in throat region and is called Adam's apple,

(V) Trachea: The extension of larynx, is a short tubular structure with 'c shap cartilaginous rings (15-20) called trachea. It is also called wind pipe (4-5 inches in length and 1 inch in diameter. The cartilage rings do not allow the trachea to collapse when there is no air in it

(VI) Primary bronchi. These are pairs of tubular structures formed as a result of bifurcation of the trachea. These are right and left primary bronchi that enter into the corresponding lungs. These are also supported by cartilaginous rings

(2) Respiratory organs: 

The respiratory organs in man are a pair of lungs. Secondary Bronchiole and Alveoli

Lungs - Lungs are a pair of highly elastic, thin walled, spongy, pinkish and hollow bag like structures situated in the thoragic cavity on the side of the heart and are well protected by bony thorasic cage. Each lung is conical triangular structure. The upper pointed side is called apex and the lower broad side is  called base. The left lung is slightly  smaller and lighter than right lung. The  right lung is divided into three lobs.  while the left lung is divided into two  lobs. Each lung is enclosed in double  walled pleural sac. The inner membrane is called visceral layer and the outer is called as parietal layer of pleural sac. A narrow  space exists between the two pleura  membranes, it is called pleural cavity  and contains  Fluid called pleural fluid.the fluid  acts as'a lubricant to reduce friction  between the lungs and thoracic wall during breathing

Secondary Bronchiole

 - Each primary bronchus After entering  the corresponding lung divides in  to  Secbndary. bronchi that give rise to tertiary   brorchi ,tertiary bronchi divide into branches that give rise to alveolar ducts that open in to blind sac called Alveoli.  Alveoli or air sacs are functional units of lungs  And forms  the gas exchange surface. There are over 700 million alveoli present in the human lungs representing a total Surface area of 70-90m².Efficient gas exchange. which takes place in human lungs, is due to the increased surface area of lungs.

                              The wall of each alveoli is only 0.0001/mm thick (0.14um). On its outside is a dense network of capillaries.special cells are also present in the alveolus' wall, which  Secreate derergent like chemical called   surfactant. Surfactant  has many functions like it reduces the amount of effort needed to breathe.... 

               ________________________________

Transportation (Animals and Plants)

Transportation - The distribution of food and oxygen to all parts of the body as well as the
removal of body wastes from the body is called as transportation.

Structure of heart. 

Heart:- Heart is a hollow, muscular organ, roughly of the size of one's fist (12cm x 9cm x 6cm)  and about 80-340gms in weight in males and about 230-280 gms in females.Heart is reddish- brown in colour and somewhat conical in form. 

Location: Heart is located between two lungs in the thoracic cavity. 

Protecting: Heart is covered by a double layered sac known as pericardium. The inner layer is called viseural layer  of periurdium and outer layer is called parietal layer of pericardium. In between the two layers of pericardium there is a narrow space called pericardial space full of
Self secreted fluid called pericardial fluid. Pericardial fluid protects the heart from any kind of mechanical injury and shock and also keeps the heart moist for proper functioning.

External structure of heart:
Human heart is four chambered organ divided by septa into two halves, the right half and left
half, each half consists of two chambers. The upper chamber is small in size and is called
auricle and lower chamber is large in size and is called ventricle.
         The auricles are demarcated externally from the ventricles by an irregular grove called
corinary sulcus. While as two ventricles are demarcated externally from each other by an
oblique grove called ventricular sulcus.

Internal structure of heart:

Internal structure of heart: Internally the heart has following components:

(a) Twe auricles 

(b)Two ventricles 

(c) Great blood vessels

 (d) Apertures and valves

Auricles: The auricles have thin walls and are separated from each other by an inter- auricular septum. The septum has an oval thin area called fossa ovalis.

(2 Ventricles: These are thick walled chambers and are separated from each other by a thick, curved partition called inter-ventricular septum. The left ventricle has thicker walls as compared to right ventricle because it has to pump blood to all parts of the body

(c) Great blood vessels: The blood vessels that enter or leave the heart are called great blood vessels. Blood from all the parts of the body except lungs goes to right auricle via three

Vessels, they are:

 (i) Superior vena cava

 (ii) Inferior vena cava

 (iii) Coronary sinus

(i) Superior vena cavu:-It brings deoxygenated blood from upper parts of the body

(i) Superior vena cavu: It brings deoxygenated blood from lower parts of the body.

Coronary sinus:  It bring deoxygenated blood from the heart walls.

  Blood vessels that leave from the heart are

 (i)pulmonary aorta

(ii) systemic aorta.

Pulmonary aorta arises from right ventricle and carries deoxygenated blood to the  lungs for purification.

Systemic aorta arises from left ventricle and supplies Deoxigenated blood to all parts of the body except lungs

Aperture and valves :-There are four valves in the heart which control the flow of blood  within the heart. They are:

(a)Bicuspid valve or Mitral valve: It consists of two cusps, it guards the opening of the left auricle in to left ventricle.

(b)Tricuspid valve: It consists of three cusps. It guards the right auricio ventricular aperture,

(C) Seminar a pulmonary valves. It has three cusps and is present at the base of aortic and puimonary arcles

(d) Aortic semilunar valve: It is present at the point of origin of aorta from the left ventricle,

BLOOD AND IT'S COMPOSITION

 Blood:- Blood is a bright red colored connective tissue that circulates in the human body with the fluid plasma in which various corpuscles are seen foun, Blood constitutes about 80% of the body weight of a person. A normal aduli man contains about 6-7 liters of blood.

Composition of blood: 

the various components of blood are briefly described as under

1. Plasma: It is a straw colored fluid part of the blood and forms about 60% of the total

blood. The major portion of plasma is water (90%) in which various substances like

glucose: amino acids, fatty acids, proteins, chlorides, sulphates, phosphates etc. are

dissolved. Some gases like O, and Co2 are dissolved in blood plasma.

2. Corpuscles: They form the living part of blood and constitute about 40% of the total

blood. They are of the following types:

1) Erythrocytes or RBC's: -They are very small, bi concave disk like, enucleated struc- tures bounded by a thin plasma membrane. The number of RBC's is approximately 5.6 million per mm  of the blood. The number of RBC's is however slightly less in females than that of the males. These cells originate from the bone marrow and have a life span  of about 120 days. After the completion of life span, they are broken down in the spleen & forms bile pigments in the liver. Their cytoplasm contains some iron containing pigments called Hemoglobin which carries oxygen and carbon dioxide and is re- sponsible for the red color of blood.

(2) Leucocytes or WBC's: -Leucocytes are nucleated, colorless and slightly larger than
erythrocytes. They are Amoeba shaped cells and show movements with the help of pseudopodia. The number of leucocytes ranges from40000-11000/mm3 of blood. This  numbeſ may however rise in case of infections. These cells havecompar atively shorter  life,sp.an (4-10) days. The various types of leucocytes include neutrophils, basophils,  lymphocytes, monocytes etc. The main function of all these cells is to protect the body from foreign invasions.

(2) Platelets or thrombocytes: These cells are around, colorless bi-convex and non-
nucleated. Their number ranges from 1.5 lakh 4.5 lakh/mm of blood. Their nuinber increases during exercise and hemorrhage. They dis integrate at once when the blood vessels is ruptured. At the sight of injury, these cells secrete thrombin and other chemical substances which help in the formation of a clot, thus preventing further blood loss.

 Functions of Blood 🩸

The various functions of blood are as under: -

1. It transports oxygen and carbon dioxide in the body

.2. It carries nutrients like glucose, amino acids, fatty acids, salts etc. from the small intes-tine to the body tissues.

3. It helps in the regulation of body temperature.

4. Blood platelets help in the coagulation of blood.

5. It transports the nitrogenous wastes like urea from kidney to where they are excreted out of the body.

 Blood vessels

the study of blood vessels is called angiology There are three types of blood vesels

Through which the blood flows

(1) Arteries

(2) veins. 

(3) The capillaries

(1) Arteries are the blood vessels that carry oxygenated blood away from the heart' Except  pulmonary artries) to various parts of body, Arteries are thich walled. Highly elastic blood vessels having narrow lumen and no valves, each artrial wall is made up of three concentric layers i.e. the inner most tunica interna or intima, the middle layer is called tunica media and outermost layer tunica externa

(2) veins: Veins are the blood vessels that collect  deoxygenated blood from all parts the body (except pulmonary veins) to the heart,  Veins are thin walled, less elastic blood vessels having wide lumen and semilunar valves. Each vein is composed of three layers i.e. inner layer called tunica interna, middle layer called tunica media and outer layer called tunica externa.

(3) Capillaries: Capillaries were discovered by Malpighi in 1661. The capillaries are formed of single layer of endothelial cells. The capillaries are microscopic, narrow vessels present at the junction of artries (arterioles) and veins (venules), where exchange of food materials. gases, waste materials etc takes place. Capillaries are found abundantly in those tissues where metabolism is very fast.

Blood clotting

Blood cougulation: The conversion of liquid blood into semi-solid blood at the bleeding site iscalled coagulation it is also called as blood clotting and the semi-solid blood is called clor.(vagulation is of great biological value for the survival of animals e.g. if someone receives a cut in the skin. the blood flows for a shorter while and then clots, which prevents further flow of blood. Thus clot acts as plug. thereby sealing the ruptured blood vessels.. 

Blood pressure

The pressure created by the blood on the walls of blood vessels due to repeated pumping

of heart is called blood pressure. The maximum pressure at which the blood leaves the heart

minimum pressure in the arteries during the relaxation phase of heart is called the diastolic

pressure. The normal blood pressure values are:

Systolic pressure = 120mmhg.

Diastolic pressure = 80mmhg.

BP = Systolic pressure (120mmHg)

Diastolic pressure (80mmHg).eins.

High blood pressure is called hypertension. Blood pressure is measured by using an

instrument called sphygmomanometer.

Lymphatic system Composition  And its functions

Lymph: Lymph is a tissue (fuid that enters the lymph capillaries from the intercellular spaces of the tissues. It is filtered from the blood plasma  and is slightly yellowish incolor. It is leaked out from the blood capillaries and finally reaches a system of channels called the lymphatic system. This lymph moves through the vessels as a result of the pressure exerted by the muscular contractions near the vessels and a system of

valves that prevents its backward flow. Normally about 2-3 liters of lymph are produced during a day. The lymph leaked out from the blood returns back to it through the right and left sub-clavian veins.

Composition: 

The composition of lymph resembles closely to that of the blood excep

that it contains less proteins, no RBC's and platelets but more of lymphocytes. The

various components in the lymph include water (90%), mineral ion (1%). proteins (4.

5%), fats (1%), lymphocytes (2%) and waste products like urea (1%).

Functions

 The various functions of lymph are as under

1. It adds lymphocytes to blood.

2. It returns the blood proteins which are leaked out from the capillaries, back into the

blood circulation.

3. It transports fatty acids and glycerol from the small intestines.

4. It protects the body from various infections.

5. It also carries cellular waste products like urea from the tissue fluid to the excretory

organs.

TRANSPORTATION OF WATER IN PLANTS

The components of xylem tissue (tracheids andvessels) of roots, stems, and leaves are inter-connected to form a continuous system of water-conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the interconnected water-conducting channels.

TRANSPORTATION OF SAP (MINERALS) IN PLANTS

Phloem transports food materials from the leaves  to different parts of the plant body. The transportation of food in phloem is achieved by utilizing energy from ATP. As a result of this, the osmotic pressure in the tissue increases causing water to move into it. This pressure moves the material in the phloem to the tissues which have less pressure. This is helpful in moving materials according to the needs of the plant. For example ,the food material, such as sucrose, is transported into the phloem tissue using ATP energy.. 

EXCRETION

Under normal conditions, the living cells of organisms (both plants and animals) work all the time in order to sustain life of the organism. Most of this work is done in the form of biochemical reactions. Some examples of these reactions are breakdown of glucose, and many other catabolic (breakdown) and anabolic (synthetic) reactions. During -synthesis of proteins, fats,carbohydrates, hormones, pigments, oxidative these biochemical reactions (i) Some metabolites are produced which may be toxic if accumulate in the cells and (ii) water and salt content of the body may increase or decrease. The two important homeostatic processes occurring in living organisms which help to maintain the steady state are :

1. Excretion

 2. Osmoregulation.

1. Excretion : Excretion is a biological process by which an organism gets rid of excess or toxic waste products of metabolism. If allowed to accumulate, these products of organism's cells would generally be harmful and prevent the maintenance of a steady state. The definition of excretion given above clearly states that the waste products have been made by the body itself and they are the products of metabolism.Therefore, egestion (removal of undigested food) is not regarded as excretion because it is not the product made by the human body. It is the leftover part of the material taken into the gut through mouth,

2. Osmoregulation : It is a process that maintains the amount of water and proper ionic balance in the body fluids. It maintains a constant osmotic condition in the body by regulating the water content and solute concentration of body fluids, particularly of sodium, potassium and chloride ions. (The body fluids are cell contents, blood plasma, tissue fluid and lymph).

Importance of Excretion and Osmoregulation

Both excretion and osmoregulation go on side by side and they have the following functions in the body:

1. Excretion removes the unwanted by-products of metabolic pathways which unnecessarily hinder the chemical equilibria of reactions.

2. Excretion removes many toxic chemical substances which damage the cells, act as enzyme inhibitors or affect the metabolic activities of the organism.

3. Excretion and osmoregulation regulate the ionic concentration of body fluids. This is important because proper balancing of ions is necessary for enzyme activity, protein synthesis, production of hormones, permeability of membranes, muscle contraction and many other metabolic activities. It regulates the water content of the body fluids which is very important in maintaining the solute potential and volume of body fluids.

5. Excretion is a very important process in regulating the pH of the body fluid. The pH of urine varies between 4.5 and 8.

STRUCTURE OF HUMAN KIDNEY

Human Kidney: A kidney is a bean shaped structure lying in the abdominal cavity  They are two in number, one on each side of the vertebral column. The left kidney is slightly higher than the right kidney. The outer surface of each kidney is convex ad the inner one is concave In the concave depression, there is an opening called Hilum through which blood ves- sels, lymph vessels, nerves & ureters enter or leave the kidney. The hilum expands into a funnel shaped structure called the pelvis. Each kidney is enclosed is a tough fibrous covering known as Capsule. A longitudinal section of kidney shows two distant regions,An outer cortex and inner medulla. Each kidney is made up of numerous delicate structures called nephron. They act as the functional units of kidney and are the sites of urine formation,

Structure of Nephron

Nephrons are the functional units of kidney. They are responsible for the removal of nitrogenous metabolic wastes from the human body. A mammalian nephron begins with a malphighian body consisting of a double walled cup like structure known as bowman capsule, enclosing a mesh of capillariesknown as glomerulus. The capsule later continues into a long convoluted tubule which is distin- guished into proximal and distal convoluted tubules respectively. 

The DCT from different nephrons join to form a collecting duct which carry the urine into the renal pelvis from where it is carried to the uri- nary bladder through the ureters. Between the tu- bules, there is a presence of a long U-Shaped seg. ment called the loop of Henley... 

 Functions of kidney.

Ans: The various functions of kidney are as under:

1. It excretes the nitrogenous metabolic wastes like ammonia, urea and uric-acid from the body of organisms.

2. It helps to maintain the normal pH of blood and other body fluids.

3. It helps to maintain the blood pressure.

4. It eliminates drugs and other toxic substance from the body.

 Hemodialysis or Artificial dialysis

Ans: The removal of the waste products particularly urea form the body by artificial means is called Hemodialysis.

                           _____________

                              _________