Chapter 6 Life Processes

Diffusion is a slow process and is insufficient to meet the requirements of the multi- cellular organisms like humans. Human beings are the multi- cellular organisms and have complex body structures. All the body cells do not contain direct contact with the environment, so they need the oxygen and oxygen requirement cannot fulfil by the diffusion process.

So, in the multi- cellular organisms like human beings they have special types of tissues and the organs which helps them to meet the oxygen requirement of the body.

All the living organisms show various types of processes during their life. This shows that they are alive, not a non- living organism or shows the assurance that they are not dead. When the organism is alive, it shows various types of processes like growth, movement, adaptations or the struggle for survival during the extreme stress conditions, respiration, reproduction, hormonal control and coordination processes, digestion, excretion and circulation. These processes ensure that something is alive.

All the living organisms require energy to live and to maintain life. Plants and animals need various separate raw materials from the outside. Plants need some raw materials as they make their food by their own. These raw materials are as follows:-

1. Carbon dioxide:- carbon dioxide is taken up from the atmosphere through the stomata and releases oxygen.

2. Water:- plants take water from the soil through the roots to the leaves. And, the transportation of water from the soil to the roots and then to the root cortex and then finally transported to the leaves from the stem occurs through the xylem.

3. Sunlight is obtained from the sun to make the food, necessary for the producers (green plants).

4. Chlorophyll:- when organisms take carbon dioxide and water from the environment, they use sunlight and convert them into the glucose or oxygen and this is taken up by the chlorophyll.

Animals feed on the plants as they are the producers plays important role in the food chain extends to the top carnivores. All animals take in food, water and oxygen from the outside according to their complexity and the needs. 

Organisms use raw material -

Food as the source of energy, oxygen for the breakdown of food to obtain energy, water is for the digestion and to maintain homeostasis that is internal temperature of the body.

All the living organisms perform various processes during their life for their adaptations and the survival is known as life processes. There are very essential processes that are considered for maintaining their lives like reproduction (all organisms survives for the reproduction), digestion and absorption of food, respiration (for breathing and exchange of gases in the respiratory tract), body fluids and the circulatory system, excretion process, for locomotion and movement, growth processes, neural control and coordination process, chemical coordination and integration process.

AUTOTROPHIC NUTRITION:- Autotrophs are those organism which prepare their food, i.e, organic food from the inorganic matter by their own through various processes like photosynthesis or by chemicals, is known as autotrophic nutrition. They are also known as “self- nourishing” organisms.

It contains two types of nutrition :

• Photoautotrophic
• Chemoautotrophic

Photoautotrophic nutrition:-Preparation of organic food from the inorganic material in the organism’s own body by the process of photosynthesis is known as photoautotrophic nutrition. All green plants, some bacteria and protists make their own food by using sunlight. Photosynthesis is the process in which when organisms take carbon dioxide and water from the environment and by using sunlight they convert them into the glucose or oxygen and is taken by the chlorophyll, these organisms are known as phototrophs. The equation of photosynthesis is as follows:-

Chemoautotrophic nutrition: The process of making organic food from the energy released by chemical reactions known as chemoautotrophic nutrition. Some bacteria make organic food by the energy that is released during the oxidation of inorganic material with the help of some chemotrophs. Some nitrifying bacteria like Nitrosomonas and Nitrobacter are chemotrophs, which helps in making food from inorganic material. 

 HETEROTROPHIC NUTRITION:- Heterotrophs are those organisms which take organic food from the autotrophs, i.e, they are dependent on other organism for the food consumption. So taking of organic food that is made by autotrophs is known as heterotrophic nutrition.

It includes 4 kinds :

• Saprotrophic nutrition
• Holotrophic nutrition
• Mixotrophic nutrition
• Parasitic nutrition

Saprotrophic nutrition: it is also known as absorptive nutrition, which absorb fluid in the form of food through their body surface is saprotrophic nutrition.

Holotrophic nutrition: The process of taking solid or fluid form of food through mouth is known as holotrophic or ingestive nutrition. In this all invertebrates or vertebrate feeds on plants or animals by breaking the larger molecules into smaller molecules with the help of digestive enzymes and then they are absorbed by the their cells.

Mixotrophic nutrition: Some organisms carry both types autotrophic or saprotrophic nutrition at the same time is known as mixotrophic nutrition. 

Parasitic nutrition: When the parasites obtain their food material from the body of the host is known as parasitic nutrition.

Photosynthesis is the anabolic process by which green plants (autotrophs) synthesize their own food in the form of glucose or carbohydrates from the simple inorganic compounds like carbon dioxide and water. So, this process is the transformation of light energy into the chemical energy to make their food in their own food,i.e, carbohydrates by green plants.

So, the following raw materials are required like carbon dioxide, water, chlorophyll and sunlight to make complex organic material from the simple inorganic material. 

1. Carbon dioxide:- carbon dioxide is taken up from the atmosphere through the stomata and releases oxygen.

2. Water:- plants take water from the soil through the roots to the leaves. And, the transportation of water from the soil to the roots and then to the root cortex and then finally transported to the leaves from the stem occurs through the xylem.

3. Sunlight is obtained from the sun to make the food, necessary for the producers (green plants).

4. Chlorophyll:- when organisms take carbon dioxide and water from the environment, they use sunlight and convert them into the glucose or oxygen and this is taken up by the chlorophyll.

Hydrochloric acid is present in the gastric juice secreted by the gastric gland which helps in the breakdown of the food. When the food enters in the stomach, contraction and expansion of muscles of the wall of stomach brings churning movement which leads to the mixing of the food with the help of gastric juice (mixture of hydrochloric acid, pepsinogen, prorennin, lipase and mucus) secreted by gastric glands. 

Hydrochloric acid helps in to disinfect the food by killing of bacteria, stops the action of the salivary amylase. It converts the pepsinogen to pepsin in the active form and convert prorenin with the addition of HCL gives the end product Rennin. It produces appropriate, i.e, low hydrogen ion concentration for about 1- 2 acidic p^H for the protein digestion and the food digestion. It moistens the food and helps in the breakdown of the larger food molecules; also denatures the many food proteins which increases the exposure of the peptide bond to the pepsin.

Enzymes are the organic compounds produced by the living cells to carry forward the biochemical reactions in and outside the cells of the organisms. Some chemical reactions occurs by the enzymes known as catalysis and the substances by which these chemical reactions occurs known as catalytic compounds. Enzymes are of two types- intracellular enzymes or Extracellular enzymes. Intracellular enzymes remain inside the cell also known as endoenzymes. Extracellular enzymes leaves the cells and functions outside the cell also known as exoenzymes. 

Extracellular enzymes contain digestive enzymes which help in the breaking down of the food. Digestive enzymes like- salivary amylase or ptyalin secreted by salivary gland in the oral cavity, pepsin (activated from pepsinogen by HCL), rennin (activated from prorenin by HCL), gastric lipase all three produced by the gastric glands in the stomach, pancreatic lipase, pancreatic amylase, DNase, RNase, trypsin (activated from trypsinogen by enterokinase), chymotrypsin (activated from chymotrypsinogen by trypsin) secreted from pancreas in the small intestine, lysozyme in tears, intestinal amylase, maltase, isomaltase, lactase, dipeptidase, intestinal lipase, nucleotidase, nucleosidase, enterokinase they are produced from the intestinal gland in the small intestine.

Small intestine is a narrow tube, 6m long in the adults, is the longest part of the alimentary canal and comprises of three parts duodenum, jejunum and ileum. Duodenum is C- shaped, 25 cm long and extended from the stomach. It receives the hepatopancreatic duct formed by the combination of bile duct and pancreatic duct. Jejunum is the middle portion of the small intestine extends from duodenum and 2.4 cm long. Ileum forms the lower part of the small intestine and 3.6 m long and opens up into the large intestine.

The mucosa in the small intestinal part is raised into millions of tiny microscopic finger - like projection called villi. Villi contains blood vessels and the lacteals, they receives the product of digestion after the absorption. The free surface of the cells which covers the villi bear numerous microvilli. They both villi and microvilli increases the absorptive surface for the digestion of food.

A terrestrial organism have advantage with regard to obtain oxygen for respiration over the aquatic organisms because of the amount of oxygen present in the environment. Terrestrial organisms have more amount of oxygen than the aquatic ones cause the terrestrial organisms are in direct contact of oxygen for the respiration but the aquatic organisms respire within the water habitat with the oxygen dissolved in the water. Level of oxygen is high in the atmosphere and low in the water, that’s why the terrestrial organism have advantage to obtain oxygen for respiration over the aquatic organisms.

There are two different ways in which glucose breaks down to provide energy in the various organisms. Glucose or carbohydrate present in the organisms in the form of food and they oxidize to give energy to the organism. Large glucose molecule breaks down into the smaller ones as seen in the aerobic and the anaerobic processes. Two ways are following- aerobic and anaerobic respiration.

1. Aerobic respiration: Glucose get break down into the carbon dioxide, water and energy is released in the form of ATP. It yields more energy available in glucose. It occurs in the mitochondrial matrix and release more energy than anaerobic respiration. 

          C₆H₁₂O₂    +     6O₂          →        6CO₂        +       6H₂O     +      Energy
          (Glucose)       (Oxygen)         (Carbon dioxide)      (Water)      (Stored in ATP)

2. Anaerobic respiration: Lower organisms like bacteria and yeast have this type of respiration. In bacteria, glucose breaks down into lactic acid and energy without the use of oxygen and without the production of carbon dioxide. It occurs in the cytoplasm and releases less energy.

                  C₆H₁₂O₆         →          2CH₃CHOHCOOH     +    Energy
                 (Glucose)                       (Lactic acid)

Exchange of the gases – oxygen and carbon dioxide, take place in various ways in the human beings.

Transport of the oxygen occurs in the two forms:- one is in the form of solution, dissolved oxygen in water and about 3% of the solution present in the plasma. And, another form is oxyhaemoglobin, about 97 percent of oxygen diffuses from plasma into the red blood cells and it loosely joins with iron of haemoglobin to form oxyhaemoglobin and then it combines with one oxygen molecule.

Carbon dioxide transport is carried by the blood in the three forms:- physical solution, bicarbonate ions and carbaminohemoglobin. About 7% of the carbon dioxide dissolves in the plasma and serve as a physical solution. In the bicarbonate ions 70% carbon dioxide released by tissue cells, diffuses into the plasma and then into the red blood cells. Carbon dioxide combines with water to form carbonic acid by the carbonic anhydrase enzyme, then this acid splits into bicarbonate and hydrogen ion. And, they are joined by the sodium and potassium to maintain pH of the blood. And about 23% of the CO2 enters into the red blood cells and combines with amino group of the reduced Hb (haemoglobin) to form carbaminohemoglobin.

Lungs are the two pairs of organ lies in the thoracic cavity on the sides of the heart. The trachea divides into two tubes- major or primary bronchi. Major bronchus enters the right lung and second one enter into the left lung. Then bronchus divides into secondary bronchi further extends into three lobes of right lung and subdivides into small tertiary bronchi and finally they divided into smaller bronchioles (wall consists of epithelium). Then, these terminal bronchioles divided into alveolar ducts enters into alveolar sacs. This respiratory pathway within the lungs are known as respiratory tree.

Alveoli are pouch like structure present on the each nerve ending and possess network of blood capillaries or covers very huge amount of surface of the human body, which increases the surface area for the exchange of gases. That is how, the lungs are designed in human beings to maximise the area for exchange of gases- uptake of oxygen by blood and release of carbon dioxide by blood.

The main components of the transport system in human beings are blood or lymph, circulatory system and blood vessels. There are some main materials that needs to transport in our body like water, minerals, nutrients, gases, hormones, waste material  and cells which protects our body for the diseases by the various systems.

1. Blood:- it is a mobile fluid, sticky and is basic (pH 7.4) and is of two types- oxygenated and deoxygenated. Blood is composed of four components- plasma, Red blood corpuscles, White blood corpuscles and Platelets. Plasma helps in the transportation of the food like glucose, certain amino acids, triglycerides, vitamins, minerals through the plasma from alimentary canal to the tissues for the growth and maintenance; helps in transportation of oxygen from lungs to the tissues for the breakdown of the food; transportation of carbon dioxide from the tissues to the lungs for the elimination from the body; transportation of hormones, wastes materials, metabolic processes products and also helps in the regulation of the hydrogen ion concentration, body temperature etc. Red blood cells help in the transport of oxygen and carbon dioxide by forming oxyhaemoglobin and carbaminohemoglobin respectively. White blood cells plays important role in the body defence against the microorganisms. And, platelets plays vital role in the blood clotting. 

2. Circulatory system or heart:- function of the heart is to pump the oxygenated blood and the deoxygenated blood and some body fluids. Oxygenated blood is pumped throughout the body and takes deoxygenated blood from the various parts of the body to the lungs for the purification of blood from the impure blood.

3. Blood vessels:- blood vessels are elastic, muscular tubes and consists of Arteries and Veins. Arteries carry the blood from the heart to the various parts of the body through the blood vessels and the veins carry the blood from the various parts of the body to the heart through the blood vessels. And, they both arteries and veins joined together by capillaries. This process is completed by the blood vascular system and the lymphatic system.

Oxygenated blood is pumped throughout the body and takes deoxygenated blood from the various parts of the body to the lungs for the purification of blood from the impure one for the maintenance of the body temperature and to maintain hydrogen ion concentration. As the birds and the mammals posses double circulatory system where pure and the impure blood remains separate. If the both oxygenated and deoxygenated blood got mixed then the whole blood will be impure and then our body will not survive for so long cause of the impure blood. That’s why the separation of oxygenated and deoxygenated blood is necessary.

Transportation in plants:- There are two components for the transportation in highly organised plants. Transportation of some materials like gases, water, minerals, organic solutes in the form of food, hormones occurs by these two components- xylem and phloem. 

1. Xylem:- transportation of water and minerals occurs through the xylem. Water and minerals are absorbs from the soil and then by the roots, transport it to the tip of growing stem in the sequential manner. This uptake of water and minerals followed by some processes like osmosis, diffusion. Water and minerals are transported through the root hair to the cortex and then to the leaves by the two pathway apoplast and symplast by the root pressure and the transpirational pull activity. This process is unidirectional.

2. Phloem:- Phloem helps in transportation of food in the form of organic solutes from leaves to the storage organs of the plant and to all parts of the plants, this process is known as translocation. Food is transported through the sieve elements of the phloem and needs metabolic energy to transport the food. They use this metabolic energy in the form of ATP and by the process of osmosis water enters in the sieve tubes that raise the pressure in the phloem and then the food is transported to the parts of the plants. Transportation of food movement involves along the turgor pressure gradient that is induced by maintained gradient of water potential. This process is multidirectional.

Water and minerals are transported through the xylem in plants. Transportation of the water and mineral is the upward movement and is the passive process. Xylem is composed of living and non- living cells. Mainly non- living cells are present, includes tracheary elements- tracheids and vessel elements. Xylem tissue also contains xylem parenchyma cells for storage function and xylem fibres for the mechanical function. Water and minerals from the soil enter into the plant through the root and then through root cortex and finally get passed into the xylem, moves upward into the leaves and the path through which water moves into xylem cells occurs through the apoplast (transport in the cell walls to the intercellular spaces) and symplast (transport occurs from cell protoplast by the interconnection of plasmodesmata) and this upward movement of the water and the minerals from roots to the aerial parts of the plant against the gravitational force through the xylem is known as ascent of the sap.

Food transportation occurs by the phloem in the plants. Transportation of food is a downward movement and is the active process. Phloem is composed of mainly four components- sieve tube elements mainly for sugar transport, companion cells carry all metabolic functions of sieve tubes, phloem fibres provide tension strength and phloem parenchyma cells helps in transfer of food also called transfer cells. Transportation of food in the form of organic solutes from one place to another place in the higher plants are known as translocation process. In this, carbohydrates are translocated from leaves to the roots and then in the storage organs like tubers, bulbs, fruits etc. along to the phloem in the form of sugar (sucrose). They are transported through the sieve elements of the phloem and this translocation needs the metabolic energy to transport the food. They use this metabolic energy in the form of ATP food in the form of organic solutes loaded into the sieve elements of the phloem vascular tissue and by the process of osmosis water enters in the sieve tubes that raise the pressure in the phloem and then the food is transported to the parts of the plants. Transportation of food movement involves along the turgor pressure gradient that is induced by maintained gradient of water potential; and the flow of organic solutes takes place from the high concentration to the lower concentration, i.e, from leaves to the roots and the organs.

Nephron is a unit of structure and function in a kidney. Nephron is composed of two parts renal cortex and renal medulla. Renal cortex is composed of Bowman’s capsule, Proximal convoluted tubule and Distal convoluted tubule and on the other hand, renal medulla is composed of Loop of Henle. 

Structure of a nephron:

Nephron is a long tubule length varying from 35-55 mm and having four regions with their different anatomical and physiological features.

1. Bowman’s capsule:- is a large, having double walled cup present at the starting of the nephron structure and lies in the renal cortex. Capsule encloses a cluster a blood vessels known as glomerulus. The Bowman’s capsule and the glomerulus (group of almost 50 capillaries) together forms the Renal corpuscle or also known as Malpighian body. The inner wall of the Bowman’s capsule has wide gaps called slit pores. So, the basement membrane of the capillary walls is present in between the blood in the glomerulus capillaries, which helps in the ultrafilteration.

2. Proximal convoluted tubule (PCT):- it is twisted part extends from the Bowman’s capsule and lies in the renal cortex. It wall or membrane consists of single layer of columnar cells having microvilli on the free surface, lies on the basement membrane.

3. Loop of Henle:- it is U-shaped lies in the renal medulla that is the lower part of the nephron. It is consist of thick and thin descending limb extended from the proximal convoluted tubule and an ascending limb which joins the Distal convoluted tubule.

4. Distal convoluted tubule:- it is greatly twisted and lies in the renal cortex. It extends from the loop of Henle and straight goes and opens up into the collecting tubule. Distal convoluted tubule have special sensitive region formed by the cellular modifications and the afferent arteriole occurs at their contact site. This mechanism plays the important role in the glomerulus filtration rate.

5. Collecting ducts:- they are the large tubes, receives the collecting tubule of several nephrons. They pass into the renal medulla and join each other and forms the large Duct of Bellini. They run across the medullary pyramids and opens up into the calyces and extends to the pelvis part.

Functions of the nephron:-

1. Nephron helps in the removal of the nitrogenous wastes (urea and the uric acid) from the blood.

2. Nephron regulates the fluid balance or the water balance by eliminating the excess water from the blood by converting them into the urine. So, balancing of fluid regulates the blood pressure.

3. It also removes the pigments, drugs, poison, extra salt and vitamins from the blood. Ionic balance should be constant for the normal functioning of the nerves and the muscles.

4. It helps in the ultrafiltration process performed by the Bowman’s capsule which filters out the acidic substances from the blood to maintain the basic hydrogen ion concentration, i.e, 7.4.

5. The blood around the nephron travels back into the body organs through the renal vessels which are non- toxic and the the waste that is collected by the ultrafiltration technique travels down by crossing the collecting duct to the bladder and get released through the urethra. 

By eliminating the acidic substances, excess water, minerals and salts and the nitrogenous waste from the blood; this maintain the volume, composition, pH and the osmotic pressure of the body fluids known as fluid homeostasis.

Excretion is process where all waste material and the excess amount of water, minerals and salts are excreted out through the life processes which are involved by the plants as well as by the animals. In plants various methods are used to get rid of excretory products.

1. Through stomata:- when the process photosynthesis occurs, in which plants make their food by their own with the help of sun’s energy. This process releases oxygen by consuming carbon dioxide from the environment and also releases their end products in the environment through the stomata, therefore it helps in the exchange of gases. 

2. Through evaporation or transpiration:- the amount of water, minerals and salts are excreted out through stomata.

3. Some other waste removed with the dead cells when plant loses some of their leaves or some waste are stored in the vacuoles which are resins and gums are excreted out.

4. Wastes products as resins and gums are present in the old part of the xylem which are also get excreted.

5. Some wastes product can be excreted into the soil or through petals, fruits etc.

Urine is the fluid and the dissolved waste materials which are excreted out by the kidney. Urine formation involves three processes:

• Glomerulus filtration,
• Tubular reabsorption,
• Tubular secretion.

When the amount of water or any fluid get increased above the normal amount, then ultrafiltration process will be increase due to increase in blood pressure of the glomerulus. Then this sends the signal to the brain or the hypothalamus to stop the release of the hormone vasopressin or antidiuretic hormone (ADH) which automatically helps in the regulation of the amount of the urine. ADH hormone deficiency slows down the permeability of the cells of the distal convoluted tubule and collecting duct that decrease reabsorption of water. This more filtration and less reabsorption produce dilute urine and then finally, the amount of urine get back into the normal state. That is how the amount of urine produced is regulated.

(c) Excretion

Kidneys are the paired organ that helps in maintaining the fluid electrolyte balance and acid base balance by the urine formation. Excretion is the process of removal of the feces or the metabolic waste from the body.

(a) Transport of water

Xylem is a complex tissue composed of living and non-living cells. The conducting cells are mostly non- living and includes two types of tracheary elements- tracheids and vessel elements. Water and minerals from the soil enter into the plant through the root and then through root cortex and finally get passed into the xylem, moves upward into the leaves. The upward movement of the water and the minerals from roots to the aerial parts of the plant against the gravitational force through the xylem is known as ascent of the sap.

(d) All of the above.

The organisms make their own food, i.e, organic food from the inorganic material with the help of photosynthesis process. And, photosynthesis is the process in which when organisms take carbon dioxide and water from the environment and by using sunlight they convert them into the glucose or oxygen and is taken by the chlorophyll.

(b) Mitochondria

The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondrial matrix. And, this reaction takes place in krebs cycle also known as tricarboxylic acid cycle (TCA cycle).

Fats are the triglycerides and they are digested through the lipases. Digestion process starts in stomach and finally gets completed in the small intestine through various agents, juices etc. small intestine is the place where the fats digestion takes place, and the digestion of fats gives the fatty acids and the glycerol as their end products.

Small intestine:- In this food is in the form of fat digested by the three secretions; Bile, pancreatic juice and the intestinal juice.

1. Bile:- bile is secreted by the liver, has no enzymes and no catalytic reactions. Salts are present which reduces the surface tension of the large fat droplets and they break them into the smaller ones and this process is known as emulsification. It produces a fine emulsion of fats in the intestine. Triglycerides get converted into the emulsified triglycerides by the action of the Bile salts.

   Triglycerides      ---Bile salts→    Emulsified Triglycerides

2. Pancreatic juice:- it contains fat- digesting enzymes which hydrolysis fats. It converts triglycerides into the diglycerides, then the diglycerides broken down into the monoglyceride and the fatty acids and they finally get converted into the another 3 fatty acid molecules and the glycerol.

   Triglycerides          ---Lipase→          Fatty Acid        +      Diglycerides
   Diglycerides           ---Lipase→          Fatty Acid        +      Monoglyceride
   Monoglyceride       ---Lipase→          Fatty Acid        +      Glycerol

3. Intestinal juice:- intestinal glands secrete the intestinal juice or intestinal lipase. Only a small amount of enzymes are released into the intestinal juice. This intestinal lipase helps in the hydrolysis of the absorbed Triglycerides, Diglycerides to monoglycerides and fatty acids.

Human digestive system includes various glands and salivary gland is one of them. Saliva is secreted by salivary gland located under the tongue which helps in the digestion of food and it contains water, salts, mucin and some enzymes salivary amylase or ptyalin. P^H is neutral i.e, 6.7. about 1.5 litres saliva and mucus are secreted in every 24 hours in the buccal cavity. Salivation activation depends on the smell, idea and imagination of food.

Role of saliva:

1. Saliva moistens food and this changes it into the semisolid mass for easily swallowing and moisten of food allows stimulation of taste buds.
2. Salvia moistens and burnish (lubrication) the buccal mucosa, tongue and lips which makes speech or fluent speaking possible.
3. Its pH is neutral 6.7 and acidity is very low, so this prevents tooth decay. 
4. It contains many salivary enzymes which kills many bacteria that are present in the buccal cavity with the food.

When the living organisms obtain food and utilizes it for the use in various biological activities like growth, maintenance and for the energy need is known as nutrition. Some nutritional elements like amino acids, fatty acids, vitamins and minerals.

Autotrophic nutrition: Preparation of organic food from the inorganic material in the organism’s own body is known as autotrophic nutrition also called self nourishing organisms.

There are two modes of autotrophic nutrition:-

• Photoautotrophic nutrition
• Chemoautotrophic nutrition

Photoautotrophic nutrition is the preparation of organic food from inorganic material by utilizing sun’s energy (photosynthesis process) and on the other hand, chemoautotrophic nutrition or chemosynthesis is the preparation of organic food with the help of chemical reaction energy. 

The necessary conditions for autotrophic nutrition are chlorophyll, sunlight, carbon dioxide, water in photoautotrophic nutrition they take carbon dioxide and water from the environment and transform these into the glucose and oxygen by the process of photosynthesis trapped by chlorophyll; and in chemoautotrophic nutrition, some bacteria develops a technique to capture energy released by the oxidation of inorganic chemical substances and make organic food. Eg. Nitrifying bacteria like Nitrosomonas and Nitrobacter. 

Their by products are glucose and oxygen. And, their by products are represented in the following equation:-

Exchange of the gases takes place in the alveoli. They have a balloon- like or pouch like structure which provides the maximum area for the exchange of gases. Alveoli are the tiny air sacs made up of squamous epithelium, which are present in the lungs and are thin walled, network of blood vessels are present for the exchange of gases. Numerous alveoli in the lungs show the maximum area for the exchange of gases between the air in the alveoli and into the blood in their surrounding capillaries and diffusion of oxygen occurs through this way. And, the diffusion of carbon dioxide occurs from the blood through the thin walls into the alveoli.

Blood has components- Red blood corpuscles, White blood corpuscles, platelets and Plasma. Red blood cells are the most abundant cells in the human body and they contain an oxygen- carrying pigment, the haemoglobin, in their cytoplasm. Haemoglobin is a conjugated protein, consists of globin and contains a non- protein group called heme; hence the name haemoglobin is given. Due to high partial pressure of the oxygen in the lungs, haemoglobin takes up the oxygen molecules and changes up into the bright red colour of the pigment, called Oxyhaemoglobin; and transport oxygen to the blood cells. 

The deficiency of haemoglobin in our body affects the oxygen uptake capacity of blood and this can lead to the deficiency of oxygen in the cells. By this deficiency, it leads to the disease anemia. Anemia can be caused by many reasons including loss of oxygen, loss of blood, destruction of red blood cells or failure in formation of blood etc.

Mammals like human beings, monkeys etc. have a double circulatory system and they include four chambered hearts (two auricles and two ventricles). Heart’s internal structure consists of auricles, ventricles, blood vessels, apertures and valves (contains various parts). As the blood passes through the heart twice during one cycle, this is known as double circulation of blood. Auricles act as the collecting chamber for the blood returning to the heart. They have to force the blood into the ventricles because of the thin wall of auricles; and ventricles act as the distributing chambers of the blood reaching the atria. Process of double circulation involves two parts – pulmonary and systemic circulation.

In pulmonary circulation, the exchange of blood takes place between heart and lungs. The deoxygenated blood from the right ventricle is pumped into the lungs through the pulmonary artery and from lungs oxygenated blood goes to the left auricle through the pulmonary vein; and from the left auricle the blood is pumped into the left ventricle.

In systemic circulation, the exchange of blood takes place between heart and body. The oxygenated blood from left ventricle is pumped into the aorta for further transportation of blood in the body and the deoxygenated blood from the body enters the right auricle through vena cava; and from right auricle the blood is pumped into the right ventricle of the heart by the body tissues. 

Both pulmonary circulation and systemic circulation take place simultaneously.  

This double circulation is necessary for the regulation and the maintenance of the body temperature.