Respiration

Respiration
The oxidation of the absorbed food material in order to obtain energy is called respiration.

There are two types of Respiration in the organisms:
1. Aerobic Respiration
2. Anaerobic Respiration
1. Aerobic Respiration
In most of the higher and larger organism, the glucose etc is oxidized by using molecular oxygen. This type of respiration is known as Aerobic Respiration. In aerobic respiration a mole of glucose is oxidized completely into carbon dioxide and water releasing enormous amount of energy. One glucose molecule in this resnpiration produces 686,000 calories of energy. Aerobic respiration thus produces 20 times more energy than the anaerobic respiration.
In aerobic respiration food is oxidized in presence of molecular oxygen.
Stages of Aerobic Respiration
There are two stages of Aerobic Respiration:
(a) External Respiration
In this stage, the organisms take the air (containing oxygen) into their bodies. This is called external respiration. this stage includes the transport of oxygen obtained from the inhaled oxygen to each cell of the body.
(b) Internal Respiration
The second stage is called internal respiration. It consists of the oxidation of glucose, amino acid and fatty acids etc, with molecular oxygen. In this stage all these reactions are included which extract the chemical energy of glucose and other compounds and store it in the form of ATP molecule, this respiration is also called cellular respiration as it occurs within cells.
In the internal or cellular respiration glucose and other compounds are passed through such enzymatic reactions which release the chemical energy gradually in small amounts with the help of which ATP molecules are synthesized.
2. Anaerobic Respiration
Some organisms oxidize their food without using any molecular oxygen. This is known as Anaerobic Respiration. In this type of respiration considerably less amount of energy is released as compared with the other type of respiration.
In anaerobic respiration a glucose molecule is broken down into two molecules of lactic acid with a release of only 47,000 calories of energy.
Glucose ——–> 2 Lactic Acid + Energy (47,000 calories)
Importance of Anaerobic Respiration
1. When earth came into being its environment was totally devoid of oxygen. The aerobic organisms cannot lie in anaerobic environment. The early organisms started respiration in the absence of oxygen to produce energy for survival of organisms.
2. Some existing organisms like bacteria and parasites which live in oxygen environment have anaerobic respiration.
3. Many useful bacteria and yeasts are anaerobic.
4. Even in the aerobic respiration of the first phase is anaerobic. The glycolysis which is the first phase of carbohydrate metabolism involves reaction which does not require the expenditure of molecular oxygen. This proves the idea that aerobic organisms have evolved from anaerobic organisms.
5. In our skeletal muscles, although aerobic metabolism takes place but in sustained activity when the oxygen supply cannot keep pace with energy demand, anaerobic respiration supplies the energy continuously by the breakdown of glucose to lactic acid.
ATP (Adenosine Triphosphate)
It is a chemical compound. ATP is an abbreviation of adenosine triphosphate. Its name indicates that it contains adenosine and three phosphate groups. Adenosine is formed of a nitrogenous base called adenine and a sugar called ribose. In ATP three phosphate groups are attached to the adenosine in a series one after the other.
Significance of ATP
ATP is a big source of energy. The two terminal bonds between the phosphate groups contain large amount of the chemical energy. When these bonds are broken in enzymatic reaction, large amount of energy is released by which energy requiring activities are accomplished, like synthesis of various compounds of carbohydrates, fats, proteins and hormones etc or for carrying out any physical work like muscle contraction, heat production or transport of substances etc.
When the terminal bond is broken the ATP is changed into ADP and phosphate 7300 calories of energy are released.
Gaseous Exchange in Plants
Plants get their energy from respiration. Plants have no special organ or system fro exchange of gases. The gaseous exchange in plants occurs in cells, of every part of the plant i.e. roots, stems and leaves etc according to their energy demand. The conducting system (xylem and phloem) of plants transports water and nutrients but plays no role in the transport of gases. The air spaces present between the cells of parenchyma of leaves, stem and roots are involved in the gaseous exchange.
Gaseous Exchange in Leaves and Young Stems
In the leaves and young stems, gaseous exchange occurs through stomata. Some gaseous exchange also occurs through cuticle.
Gaseous Exchange in Woody Stems and Roots
In woody stem and roots, there are present dead cells beneath the epidermis which form cork tissue. Later on, this tissue becomes porous. The pores are called lenticels. These are involved in gaseous exchange.
Gaseous Exchange in Leaves
The aquatic parts obtain oxygen for their respiration by diffusion from the dissolved oxygen in water. Whereas the land plants get their oxygen from air directly through their stomata which are more abundant on the lower surface than the upper surface of leaves.
Gaseous Exchange in Roots
The roots get their oxygen for gaseous exchange through diffusion from the air existing in the space between soil particles.
Process of Respiration in Plants
The respiration in plants continues day and night. In this process, the oxygen from the airspaces in the leaves and stems is diffused into tissues and cells after getting dissolved in the film of water which is present over the cells. In the cells this oxygen oxidizes the carbohydrates and other organic compounds into carbon dioxide and water to produce energy. Some of the water (vapours) comes in the airspaces from where they diffuse out to the atmosphere through lenticels and stomata. The elimination of carbon dioxide is more evident from the parts without chlorophyll like growing seeds and buds. The water produced in this process becomes a part of the already present water in the body of plants. The various chemical reactions of respiration are controlled by the specific enzymes. This process occurs at a faster rate in the parts of the plant having rapid growth like growing seeds, buds, apical meristem of roots and shoots, because these parts require more energy to accomplish the growth process.
Relationship between Respiration and Photosynthesis
The gaseous exchange in plant is not very evident during the day time as the products of respiration i.e. carbon dioxide and water are used in the process of photosynthesis. In the bright sunshine, because of high rate of photosynthesis the carbon dioxide produced in respiration falls short and therefore, some carbon dioxide has to be taken into the plant from outside for photosynthesis.
In the day time the plants therefore, take in carbon dioxide and expel out oxygen. The process of photosynthesis occurs in chloroplasts whereas the process of respiration takes place in cytoplasm and mitochondria.
Gaseous Exchange in Animals
The gaseous exchange in different animals takes place by different methods and organs. In unicellular aquatic animals like amoeba, the dissolved oxygen in water diffuses directly through their cell surface into the interior of the animal and the carbon dioxide similarly diffuses out from their bodies into the external water. This is the simplest way of gaseous exchange and it can occur only in small animals with a diameter of less than one millimeter. These animals have greater surface area of volume ratio and have low rate of metabolism.
During evolution, as the animals became complex and complex and grew in their size, their skin or external body surface become impervious to water. Thus the gaseous exchange became impossible through diffusion. In large animals certain organs were developed for exchange of gases w.g. the moist vascular skin, gills, lungs and tracheoles. These large animals have developed blood vascular system which transports oxygen from the respiratory surface to the deep cells and tissues in all parts of the body. The blood in all animals has some respiratory pigments like haemoglobin which carry large amount of oxygen efficiently from respiratory surface to the interior cells.
Properties of a Respiratory Surface
1. Respiratory surface should have large surface area.
2. Respiratory surface should be moist.
3. Respiratory surface should be thin walled.
4. Respiratory surface should have blood supply.
Gaseous Exchange Through Skin
For the exchange of gases through the skin the skin must be moist and richly supplied with blood. The oxygen is diffused from the external water to the blood and the carbon dioxide is diffused from the blood to exterior water. In amphibia and fishes the gaseous exchange occurs through the skin besides through the gills or lungs. The frogs and tortoises breath through the skin during their hibernation period.
Gaseous Exchange by Gills
The gills are very effective for gaseous exchange in aquatic animals. Gills are of two types:
(a) External Gills
(b) Internal Gills
(a) External Gills
Some animals have external gills which project out of body of animals. These gills have very thin and highly vascularized surfaces e.g. the dermal papillae of star fish and arthropods.
(b) Internal Gills
These are present inside the body inner to skin e.g. in fishes and arthropods. Have you ever examined a fish closely? How ill you know that the fish is fresh or not? If the colour of gills is red then it is fresh but if the colour of gills is changed, it is definitely not fresh. The red colour of the fish gills shows the presence of oxygenated blood.
Gills of Fish
In fishes the gills are present in the branchial cavity present on lateral sides of the body behind the head. This branchial cavity is covered over by an operculum. There is a counter current flow of water and blood in gills which ensures maximum exchange of oxygen and carbon dioxide between the blood and the bathing water. Water enters through the mouth, flows over the gills and goes out of the body from the opercular aperture.
Human Respiratory System
In humans, there is very efficient respiratory system. It consists of certain organs which are called respiratory organs these include nose, pharynx, larynx, trachea, bronchi and bronchioles.
Nose
The air enters through the external nostrils into the nasal cavity. This is lined with mucous secreting epithelium and ciliated epithelium. The nostrils are lined with hairs. The nasal cavities, located above the oral cavity and behind the nose are covered with epithelial tissue.
The beating of cilia creates a current in the mucus that carries the trapped particles towards the back of the nasal cavity. From here the mucus drips into the throat and is swallowed. Mucus keeps the nasal cavities moist. Bones of the nose warm up the air. Mucus moistens the air. Hair filter the air and stop the dust particles bacteria and any other foreign substance from going to next part of respiratory system. In this way air is purified and is then pushed into the pharynx.
A number of cavities called sinuses open into the nasal cavity. The sinuses are lined with mucus secreting epithelium. The opening of sinuses into the nasal cavity is very narrow. If these openings are closed due to cold or inflammation, the sinuses get filled up with mucus this results in headache and changed voice.
Pharynx
The nasal cavity opens into the pharynx (throat) through two small apertures which are called internal nares or internal nostrils. The pharynx is muscular passage which extend from behind the nasal cavities to the opening of oesophagus and larynx. The air goes from the pharynx into the larynx.
Larynx
The upper most part of the wind pipe (trachea) is called the larynx. The larynx is a cartilaginous box. Two fibrous bands called vocal cords are located in this box. These vibrate to produce sound. Larynx is, also called sound box or voice box. The air enters the larynx through a small aperture called glottis which is guarded by a muscular flap called epiglotis which fits into this opening while the food is being swallowed into the oesophagus. It prevents the food from entering into the trachea and choking it. During breathing epiglottis keeps the glottis open so that air goes to trachea.
Trachea
The air tube (wind pipe) is known as trachea. It is about 12 cm long and lies in front of the oesophagus. It has incomplete C shaped cartilagenous rings which are regularly placed in its wall and all along its length. These rings prevent the collapsing of the tube nd thus keep the air passage wide open all the time. Trachea is also lined with ciliated mucous epithelium. Any foreign particles present in the inhaling air get trapped in the mucous that is moved out of the trachea by breathing of the cilia in the upward direction. In trachea air is further cleansed and filtered and then moved towards the lungs.
Bronchi
The trachea while passing the chest cavity divides into two smaller tubes which are called bronchi (single bronchus). Bronchi are similar in structure to the trachea but are smaller in diameter and they have in their walls small irregular catilageuous plates. Each bronchus enters into the lungs of its own side. The right bronchus divides into three secondary bronchi and the left bronchus divides into two secondary bronchi which serve the 3 right and 2 left lobes of the lungs respectively.
Bronchioles
the secondary bronchi further divide into very fine branches until they end in thousands of passage ways called respiratory bronchioles. The bronchioles have not cartilaginous plates in their walls. They have smooth muscle and elastic fibers.
Alveoli
The walls of the respiratory bronchioles have clusters of tiny branches(like bunches of grapes) that along with the respiratory bronchioles re the sites of gaseous exchange, these pouches or air sacs are called alveoli (singular: alveolus). The alveoli are enormous in number. Each lung has about three hundred million alveoli.
Pulmonary artery brings deoxygenated blood from the heart into the lung. Here, it divides and re-divides until it forms a network of fine capillaries over the wall of each alveolus. The walls of alveoli are very thin (1/1000 mm thick) and moist. Thus, alveoli are efficient site for gaseous exchange.
The Lungs
There is a pair of lungs present in the chest in man. Actually, the masses of alveoli constitute lungs and their lobes. The lungs re protected by the chest box from sides and by a doem shaped muscular diaphragm from below. Chest box or ribcage is made up of ribs. Between the ribs, there are present inter-costal muscles. The diaphragm is a muscular sheet which partitions the chest and abdomen.
The two lungs re covered by a double layered membrane called pleural membrane. There is a thin film of fluid in between the two layers. This watery fluid makes the movements of the lungs (expansion and contraction) easy. It also protects the lungs from external injuries.
(Diagram)
Mechanism of Breathing
Breathing occurs in two phases:
1. Inspiration
2. Expiration
1. Inspiration
1. During inspiration, the dome-shaped diaphragm contracts and becomes flat some what and thereby lowering the floor of the thoracic cavity.
2. The external inter-costal muscles contract raising the ribcage. A combined action of these two events expands the thoracic cavity, which in turn expands the lungs.
3. The air pressure within the lungs decreases.
4. Thus air from the environment outside the body is pulled into the lungs to equalize the pressure of both sides.
2. Expiration
1. The diaphragm relaxes and assumes dome like shape. During expiration, the external inter-costal muscles relax and the internal inter-costal muscles contract as a result of which ribcage drops.
2. The combined action of these two event decreases the volume of the thoracic cavity which in turn decreases volume of lungs.
3. The air pressure with in the lungs increases.
4. The air is thus forced out of the lungs.
Bad Effects of Smoking on Heath
Smoking is injurious to human health. The smoke contains many chemical and gases. Dried tobacco leaves are used in cigarettes. The tobacco on burning produces a number of dangerous and toxic compounds.
Chemicals Present in Cigarette Smoke and Their Harmful Effects
(a) Nicotine
1. Man is addicted to cigarette damages brain tissues.
2. Causes blood to clot more easily.
3. Harden walls of arteries.
(b) Tar
1. Kills cells in air passages and in lungs.
2. Increases production of mucous and phlegm in lungs.
3. Causes lung cancer.
(c) Carbon Monoxide
Prevents red blood cells from combining with and transporting oxygen around the body.
(d) Carcinogens
promote the growth of cancerous cells in the body.
(e) Irritants
1. Irritate air passages and air sacs in the lungs.
2. Kill cells at the surface of air passages.
3. Causes smoker’s cough and lung cancer.
Combustion
A chemical reaction in which a substance combines with oxygen and produce heat, light and flame is called Combustion.
Respiration
A process that liberates chemical energy from organic molecules when oxidized is called Respiration. It occurs in all living cells. In fact respiration is a series of complex oxidation and reduction reactions in which energy is released bit by bit.
Photosynthesis
The process in green plants by which green plants manufacture their own food by using carbon dioxide and water with the help of energy absorbed by chlorophyll from sunlight is called photosynthesis.
Relation of Combustion, Respiration and Photosynthesis
Combustion is the process of burning in which wood, coal, methane, gas etc are burnt in the presence of oxygen, producing carbon dioxide and water accompanied with the release of energy. It is an exothermic chemical reaction.
Cellular respiration can be compared to burning of fuel in which organic food (carbohydrates, fats and proteins) rich in carbon burn in the presence of oxygen producing carbon dioxide, water and energy.
Respiration like combustion is a catabolic exothermic chemical process. However, the difference between the combustion and respiration is that the combustion takes place in one go, releasing the entire energy as the heat, which may be utilized or is lost into the environment. the respiration completes in several small steps. Each step is under the control of a specific enzyme, releasing energy in small amounts which can be stored in the form of ATPs. Photosynthesis, another metabolic process, is just opposite to combustion. Combustion is a catabolic process; the photosynthesis is an anabolic process. In photosynthesis organic substance is synthesized from carbon dioxide and water in the presence of sunlight energy and chlorophyll. The molecular oxygen is evolved as the by-product combustion is exothermic and releases energy, photosynthesis is endothermic and absorbed energy.
Photosynthesis and respiration are the two metabolic reactions opposite to each other. Photosynthesis takes place only in the gree parts of the plant body having chlorophyll, whereas respiration takes place in all the living cells of plants and animals. Mitochondria are the cellular organelles where respiration takes place while the organelles for photosynthesis re chloroplasts. Photosynthesis takes place during the day time only, whereas respiration takes place day and night. In photosynthesis body weight is increased but in respiration weight is decreased. Respiration is an oxidation reaction whereas photosynthesis is a reduction reaction and can be well understood by comparing their chemical reactions.
(Diagram)
Chemical Equation in Respiration
Glucose + Oxygen ——-> Carbon dioxide + Water + Energy (In presence of mitochondria and enzymes)
Chemical Equation In Photosynthesis
Carbon dioxide + Water ——–> Glucose + Oxygen (In presence of chloroplast and solar energy)
Respiratory Organs of Insects
The respiratory system of insects is called the Tracheal system. It is a network of interconnecting air filled tubes called trachea delivering air directly to the body tissue cells. Trachea open outside through pores called spiracles.
Each trachea has chitinous cuticle lining which prevents it from collapsing.
A pair of spiracles is usually located on the sides of each segment of the thorax and abdomen. Spiracles have valves to open or close them regulated by special muscles. This controls water loss from internal body tissue.
(Diagram)
Trachea break up into numerous smaller tubes called tracheoles which ramify among the body tissues ending blindly. Tracheoles lack a chitinous lining. At rest the tracheoles are filled with watery fluid through which gaseous exchange tkes place in dissolved state.
Ventilation is brought about by contraction and relaxation of abdominal muscles which result in a rhythmic pumping of air into and out of the trachea.
Gas exchange takes place in tracheoles which are permeable to gases and are filled with a fluid in contact with the body tissue. Since oxygen diffuses directly into the tissue cells, blood of insects does not have hemoglobin so it is white. However, removal of carbon dioxide is dependent on blood plasma which takes it up for removal via spiracles

Food And Nutrition

Need for Food

Everything needs energy to do some job e.g. to operate machines, electricity, steam, fuels like coal, petrol, wood etc are burned to get energy. Similarly, living organisms require energy to carry out their diverse activities of life. They maintain the complex structure of cells, excrete waste material, and reproduce for continuation of their race. They grow in size during their life span as they are small when born and are large when adult. A considerable amount of energy is required to carry out the functions of life. The organisms, therefore, need to have some source of energy in order to maintain their life. Organisms get their energy from food. The type of food depends upon the kind of organism using the food. Some organisms use inorganic compounds to get their energy requirements. Some organisms use vegetables (plants) while some others require flesh (animals) as their food.
The organisms burn up their food (metabolize) to get a special form of energy called ATP (Adenosine triphosphate) which is used by them to carry out their functions of life.

Nutrients of Food and Their Importance

The food of organisms and the organic compounds, building their bodies are almost same. Their bodies are composed of carbohydrates, proteins and fats etc. These substances are used by organisms as their food. They get energy from these substances. They use the components of food in growth and repairing of damaged tissues. Thus substances acquired by organisms to obtain energy are called nutrients and the process by which they are obtained is called nutrition. The food of all organisms which depends upon already prepared food has been found to consist of six basic components. These are as follows:
1. Carbohydrates
2. Proteins
3. Fats, Oils
4. Vitamins
5. Minerals
6. Water

Carbohydrates

They are organic compounds. They are found in all organisms. They are commonly known as sugars. They contain three elements carbon, hydrogen and oxygen in which hydrogen and oxygen exists in 2:1 ratio that is why they are called hydrates of carbon or carbohydrates. One gram of carbohydrates provides 3800 calories of energy.
Forms of Carbohydrates
Carbohydrates occur in three forms.
1. Monosaccharide
2. Disaccharides
3. Polysaccharides
1. Monosaccharides
Monosaccharides are simple sugars. Their common example is glucose. Glucose is main source of energy in our body cells.
2. Disaccharides
Disaccharides are formed by condensation of two monosaccharide units e.g. sucrose is formed by the combination of glucose and fructose. Maltose is another disaccharide.
3. Polysaccharides
Why many monosaccharides link together, they form polysaccharides. A single polyusaccharide may have many hundred units of monosaccharides. The common examples of polysaccharides are glycogen and starch. Glycogen occurs in animals and starch in plants. Another polysaccharide is cellulose, present in the cell walls of plants. It is the most abundantly occurring carbohydrate.
Sources of Carbohydrates
Carbohydrates containing starch are obtained from cereals and their products like wheat, rice, maize, oats and barley. They are also obtained from carrots, radish, turnip, beet, beet root and potatoes. Simple sugar called glucose is obtained from grapes. The sugar derived from fruit is called fructose. Then from beet and sugar cane is called sucrose and that from milk is lactose.
Importance of Carbohydrates in Human Body
One gram carbohydrate food provides 3800 calories to our body. The Carbohydrates are the cheapest and easy source of energy. Surplus carbohydrates are stored as glycogen in the liver and muscles, or converted to fats and stored in the fat cells beneath the skin and causes obesity.
Children, laborers and people, involved in physical labor need more carbohydrates in their daily diet whereas other should avoid them because their excess in the body can cause blood pressure, diabetes, obesity and heart diseases, therefore, carbohydrate products should be taken with care.

Proteins

Proteins are very important organic compounds found in all organisms. Proteins contain carbon, hydrogen, oxygen and nitrogen and sometimes some amount of sulphur. There is no 2:1 ratio between hydrogen and oxygen. A protein molecule is composed of many building units linked together to form a chain. A chain of amino acids is called polypeptide. Amino acids are building units of a protein molecule. About twenty different amino acids occur in nature that combines in different manners to make different type of proteins. Proteins are structural part of the cell membrane. Some proteins are fibrous. They form different structures in the body like muscles, bones and skin. They also occur in our blood and cells. The enzymes which control different chemical reactions in the body are also proteins in nature. As a result of protein catabolism, energy is released. One gram of protein produces 4.3 kilo cal of energy which is used to synthesize ATP.
Amino Acids
Plants can synthesize all the amino acids they need from carbohydrates, nitrates and sulphates but animals can not synthesize all amino acids. Amino acids are the building units of proteins.
There are about twenty different types of amino acids which are used in the synthesis of protein found in the human body.
Non-Essential Amino Acids
There are many amino acids which a human body can synthesize within the body. These are called non-essential amino acids.
Essential Amino Acids
There are approximately ten amino acids, which human beings cannot make. These are called essential amino acids and can be obtained directly from proteins in the diet.
Sources of Proteins
Following are the sources of proteins:
Animal Sources e.g. meat, fish, chicken, milk and cheese.
Plant Sources e.g. legumes, pulses, dry fruit and cereals.
Importance of Proteins in Human Body
1. Proteins are essentially required for growth and development.
2. Growing children ,pregnant women and lactating mothers need a lot of proteins.
3. An adult requires 50-100 gms of proteins daily.
4. Protein deficiency in children and cause a disease called Kwashiorkor.
5. Proteins play an important role in the building of cellular protoplasm.
6. They also play an important role in the building of muscles and connective tissues.
7. Many proteins are required for making enzymes, hormones and antibodies.
8. If proteins are eaten in excess than needed by body, the excessive amino acids are converted into carbohydrates by the liver, which are either oxidized to release energy and converted into glycogen and fat and stored.

Lipids

Lipids are obtained from two sources:
Animal Sources
Ghee, butter, cream, animal fat and fish oil.
Plant Sources
Oils from mustard, olives, coconut, maize, soya beans, sunflower and peanuts.
Importance of Lipids
1. The use of fat rich products increase in winters because they provide double the amount of energy as compared to carbohydrates.
2. They provide 9000 cal/gm energy to the body.
3. In plants fats are stored in seeds, and in animals, they are found beneath the skin and around the kidneys where they are not only stored but also protect these parts.
4. They provide materials for building new protoplasm and cell membrane.
5. Some fatty acids are essential for man.
6. Saturated fats (animal fats) should be used with, great care in our diet as they lead to rise in the cholesterol level, which accumulates in the blood vessels, and thus affects the flow of blood in the arteries This can result in heart attack

Vitamins

Vitamins are very complicated compounds. When vitamins were discovered, their chemical nature was not well known. Therefore, they were denoted with English letters as A, B, C, D, E and K. Now it is known that vitamin B is not a single vitamin but a group of vitamins call ed as vitamin B complex. It has eight different compounds as B1, B2 etc although they have no energy value but they are essential in small quantities for the normal activities of life. It has been observed that when animals were given a diet rich in carbohydrates, fats and proteins but lacking vitamins, the growth and development of the organisms were affected and the animal suffered from various diseases. Vitamins are needed for healthy growth and development of the body. They also serve as enzyme.
Plants can prepare their vitamins from simple substances but animals obtain it directly or indirectly from plants. Fifteen or more vitamins have been isolated and most of them seem to act as essential part of coenzyme involved in chemical changes taking place in the body.
If our diet has variety and consists of fresh fruit and vegetables, our body will receive all those vitamins which are necessary for us.
Fat Soluble Vitamins
Some vitamins are fat-soluble and can be stored along with fat.
Water Soluble Vitamins
Some vitamins are water soluble and hence cannot be stored in the body, thus their in take is required continuously.

Minerals

Mineral Salts
Mineral salts are inorganic compounds. They do not provide energy to the body. However, they are required for the normal chemical activities of the body. Man can obtain them from animals or plants which absorb them from the soil. Some minerals are needed by man and mammals in relatively large quantities, other are required in very small quantities.
Trace Elements
The mineral required by organisms in minute quantity are called Trace Elements.
Few Important Minerals
Calcium, Sodium, Potassium, Magnesium, Chlorine, Iron, Phosphorous and iodine etc.
Role of Minerals
Sodium Chloride
It helps to make hydrochloric acid in the stomach which is very important for the digestion of food. Along with potassium it helps to conduct messages through nerves.
Potassium
It is found in the living cells especially in the red blood cells and muscles and it helps in the growth of the organism. The body acquires it through cereals.
Magnesium
It is an important component of the bones. It is obtained by eating different vegetables. It helps the enzymes which control different metabolic reaction.
Calcium
It plays an important role in strengthening the bones and teeth. It helps in blood clotting, muscular contraction and in the conduction of nerve impulse. It is found in milk, eggs, fruit, cereals and green leafy vegetables.
Iron
It is very important mineral. It helps in making hemoglobin in the red blood cells. It occurs in meat, liver, eggs, peanuts, spinach and other vegetables.
Flourine
It helps in the growth and development of the bones and teeth. If it is mixed in drinking water in suitable amounts, dental decay (caries) can be reduced in children. The body can obtain this mineral from vegetables and fish.
Note: In addition to these mineral trace elements like cobalt, manganese, zinc and copper are also necessary for the better health of the human body.

Role of Water

Water
Water makes approximately 70% of the body tissues. It is an essential component of the protoplasm. One can live without food for more than a week but a person can die within two to three days due to lack of water.
Importance of Water
1. It plays an important role in digestion.
2. It helps in transport of digested food and other materials in dissolved form.
3. All the chemical reactions inside the cell take place in the presence of water.
4. It helps in excretion of urine, removal of faeces.
5. Enzymes become more active in solution form.
6. It keeps the blood thin and so that it can be easily circulated.
7. Water regulates the body temperature.
8. Its deficiency in tbe body causes dehydration, which can prove fatal.
9. Plants cannot photosynthesize without water.
10. The people living in hot and dry places need more water. By breathing, sweating and urination about 2-3 liters of water is lost per day.

Dietary Fibers

Dietary Fiber (Roughage)
These are foods which provide fibers to our body.
Sources of Dietary Fibers
All fruit and vegetables provide fibers to the body for example, citrus fruits, cereals, spinach, cabbage and salads. The cell wall in plant cells are largely made of cellulose which cannot be digested by man. Bacteria living in the gut of ruminants digest the cellulose and convert it into fatty acids, which renders it absorbable.
Importance of Dietary Fibers
1. Roughage adds bulk to the food enabling the muscles of the alimentary canal to grip it and keeps the food moving by peristalsis.
2. Absence of roughage in our diet may lead to constipation and related disorders.
3. Fibers keep the intestines in a healthy condition, thus our daily diet must contain a lot of fruit and vegetables

Nutrition and Food Technology

For thousands of years, man has been making efforts to grow more food for storage so that it can be used when needed. Modern man knows how to preserve food for use subsequently when needed. Man has adopted modern techniques of food preservation in which its nutritional value and taste are preserved. Foods are damaged by bacteria; fungi and other micro-organisms, which occur everywhere. These organisms make food unsafe for use and storage, so it is necessary to kill bacteria or other organisms as soon as they enter food.
Early methods of preservation affected the taste of the preserved food, but modern scientific techniques prevent contamination of food, keep the taste and make it consumable even after a long period of storage. To achieve this, temperature plays an important role.
Food that we take is usually made up of dead tissue and it can be spoiled for two reasons, either the food is contaminated and destroyed by bacteria or fungi or the enzymes still active in tissue start breaking down the cells, thus making food poisonous and tasteless to eat.
All bacteria, fungi and micro-organisms must be killed or their growth must be retarded in order to protect the food from spoilage. Heat is the best source, as extreme increase in temperature retards bacterial growth and enzymes can also be denatured. Thus temperature extreme can be useful in the preservation of food

Methods of Food Preservation

Pasteurization
This method was discovered by famous biologist, Louis Pasteur. By this method milk is prevented from turning sour. In this process, milk is heated to 71 C for a few seconds and then cooled rapidly. This kills most of the bacteria. The bacteria which survive this treatment may become retarded in growth. In this way, the milk is preserved for a few days.
Refrigeration
In this methods, food is kept at very low temperature usually below freezing point. It retards the action of enzymes and the growth of bacteria. In deep freezers food can be preserved for many years. Quick freezing helps to maintain the taste and texture of meat, fruit and vegetables.
Dehydration
In this method food is dried. Such food can be kept safe for a long period at normal temperature. Bacteria do not grow without water, therefore when water content is removed from meat and vegetables, they can be preserved for long durations. Pickling of food is another common indigenous technology in which taste and texture of pickled food is maintained for long.
Canning
In this method the food is first heated at a high temperature. This kills bacteria and destroys enzymes. Then, the food is sealed in a metallic container. In this way; food becomes safe from contamination. Metallic cans are usually lacquered to prevent food from chemically reacting with metals and producing toxic substances

Health Problems Related to Nutrition

Under Nutrition
During under nutrition a person’s diet is deficient in the required calories. children are mostly affected due to availability of less than normally required diet and they suffer from a disease called marasmus. In this disease, children are reduced to a skeleton as the body becomes completely depleted. Some of the countries like Ethiopia are famine stricken. Although international community does try its best to rescue the famine inflicted areas yet it is not possible for them to meet their complete nutritional requirements on such a large scale. The world population is continuously and rapidly increasing each year. It has been estimated that by 2025, the world population will rise to ten billion, whereas water and soil resources are being continuously depleted by increasing use by the continuously growing population. The experts therefore envisage that increasing human population if not checked will soon eat up all the food resources of the world which may lead to destruction of human race.
Malnutrition
If malnutrition (a diet missing in one or more essential nutrients) continues for a prolonged period, particularly under special circumstances, such as during pregnancy or immediately after childbirth, it is found to be very harmful.
If malnutrition occurs during lactation period, it causes irrepairable damage to the infant. During the last quarter of pregnancy when foetus is rapidly developing its cerebral tissues, the protein deficient diet of the mother results in mental retardness and nervous abnormalities in foetus, which may prove fatal or lead to permanent disorders. These abnormalities may also occur in infants if the lactating mother is taking a protein deficient diet during the first year of breast-feeding.
If a human diet lacks essential elements or nutrients, the body will fail to prepare vital compounds, and thus the person will suffer from various diseases. Deficiency of a few amino acids, vitamins, fatty acids (about thirty compounds) and 21 mineral elements, called as essential nutrients in diet are responsible for various diseases.
In the poor countries like ours packaged or junk food(sugar coated cumin seeds, betal nuts, chewing gums and drinks) are not prepared under proper care. The food colours scents and flavours are added to make them commercially attractive. But these are substandard and harmful for human health. The use of food additives may be the cause of dangerous diseases like cancer and ulcer etc. These items should, therefore, be avoided.
Over Nutrition
It is the problem of the developed countries where people eat too much. Obesity is the most common disorder due to over nutrition. Obesity is the cause of a large number of diseases too

Balanced Diet

A diet containing essential dietary components in the correct proportion, which helps to maintain health and fulfills the body requirements of organisms, is known as balanced diet. The degree to which any particular meal is adequate in providing energy from food depends on the nature of the job of a person.
A common man’s diet is said to be suitable if it provides 50% calories from carbohydrates, 40% from fats, and 10% from proteins. Carbohydrates are abundantly used foods because they are readily available and cheaper as compared to fats and proteins. We can live without carbohydrates it our diet has all the components of food and is capable to provide total calories required by the body. Fats are taken in our diet to obtain energy. Our daily food requirement varies with sex, age and occupation e.g. children need more food because they are growing. Youth need more food than elderly people due to physical exertion. Men need more food than women. Pregnant women, lactating mother’s convalescents need more food as compared to others.

Teeth

Teeth
God has blessed animals and human beings with teeth. They help in breaking and chewing of the food. They are present in oral cavity.Teeth are attached to the upper and lower jaws.
Kinds of Teeth
Humans have two sets of teeth during their lives.
Milk Teeth
The first set of teeth begins to come through the gums when the baby is about six months old. these are called the milk teeth and all twenty teeth are formed over a period of two years.
Permanent Teeth
The milk teeth begin to drop out at the age of six years and are gradually replaced by the second set of teeth called the permanent teeth. In man the milk teeth do not fall off simultaneously, they fall off one by one and similarly permanent grow one by one as well. Healthy teeth are strong and give a beautiful and lustrous look. You must brush your teeth at least twice a day.
Structure of a Tooth
A tooth has two permanent parts, the Crown and the Root. The crown is that part of tooth which projects out of the gum and jaws. The root the the tooth is embedded into the gums and is therefore, hidden.
Enamel
This is the outer most part of tooth which is very hard and lustrous. It is deposited on the outside of the crown of the tooth by cells in the gum. The enamel is a non-living substance. It is made up of calcium salts. It imparts beauty to the tooth and protects the tooth. If the enamel gets removed then the teeth start decaying.
Dentine
It is the part of teeth present under the enamel which is hard. But it wears off if the enamel gets removed. Running through the dentine are strands of cytoplasm arising from the cells in the pulp. These cells keep on adding more dentine to the inside of the tooth.
Pulp
The innermost part of the tooth is hollow and is made up of soft connective tissue which is called the pulp. The strands of cytoplasm in the dentine derive their food and oxygen from the pulp which enables the tooth to live and grow. The pulp contains sensory nerves and blood capillaries. These nerve endings are sensitive to heat and cold and can produce the sense of pain e.g. toothache.
Cement
Cement is a thin layer of very hard material which covers the dentine at the root of the tooth. the fibers holding the tooth in the jaw are embedded in the cement at one end and in the jaw at the other. In this way teeth remain firmly embedded in the jaws.
Protection and Cleanliness of Teeth
Teeth are a gift of nature. For a good health, presence of clean, good healthy teeth is necessary if we wish our teeth to remain healthy; we should wash and clean them after every meal. Our tongue helps in cleansing the upper portion of teeth to some extent. If food particles are firmly trapped up between the teeth, or between gums and teeth, then it becomes difficult to remove them with the tongue. The main cause of tooth decay is a sugar coating left by sugary food on the teeth, which is converted into acid by bacteria. The acid damages the enamel and allows the bacteria to infect the soft dentine and reach the pulp cavity. The dentine begins to decay and causes toothache. Sugary foods such as sweets, toffees and chocolates, the bacteria which cause decay, form a thin layer of scum over the surface of the teeth. This layer becomes very hard with the passage of time and becomes difficult to remove. This scum is called plaque.
The teeth should be cleansed properly and regularly with a miswaak or a tooth brush. So that there is no formation of plaque. We should eat less sugar or sweet and sticky foods and also cleanse the teeth afterwards. Balanced diet should be taken, especially by young people who have growing teeth

Digestion of Food

First of all food comes in the oral cavity where the teeth crush and break the food and convert it into small particles. The tongue rolls the morsel of food and pushes it under teeth again and again so that the food is evenly divided into fine particles and the saliva secreted from the salivary glands gets mixed with the food. The saliva lubricates the food and makes the particles adhere to one another, forming a ball of food called bolus. Now the chemical digestion of food begins. Saliva contains an enzyme to digest starch in the food. The combined action of teeth, tongue and saliva pushes the bolus through the throat into the oesophagus, and then it reaches the stomach.
Definition of Digestion
Digestion is the process in which the insoluble and non-diffusible components of food are broken down and by the action of enzymes are converted into soluble and diffusible substance to be absorbed into the blood stream.
Types of Digestion
1. Mechanical digestion
2. Chemical Digestion
1. Mechanical Digestion
In mechanical digestion, the food consisting of large sized particle is broken into fine pieces by cutting, grinding, chewing and churning up, so that enzymes can act upon it efficiently and effectively. Mechanical digestion of food takes place in the mouth and stomach.
2. Chemical Digestion
In chemical digestion, the digestive enzymes mix with the food and act upon it to break it down further into simple and diffusible chemical forms. The enzymes act on carbohydrates, proteins and fats separately. Chemical digestion takes place in all the major parts of the digestive system. The digestive glands such as liver and pancreas also play very important role in this digestion.
Digestive System
All living things require food to live and carry on their life functions. Animals are unable to synthesize their food.
Digestion is the process in which the non-diffusible molecules of food are changed to diffusible ones by the action of enzymes. All the organs which take part in this process make a system which is called the digestive system.
Human Digestive System
The process of digestion takes place in the alimentary canal. It starts from the mouth and ends at the anus. The tube assumes different shapes according to their role in the process of digestion. It consists of the mouth, oesophagus, stomach, small intestine, and large intestine. Besides these organs liver and pancreas, also play important roles in digestion.
Peristalsis
The muscles of alimentary canal produce rhythmic waves of contraction which is called peristalsis. Due to this process, food is carried through various parts of the alimentary canal.
Ingestion
The food of animals and human is in the solid form and may be bulky. Taking in of the food in the oral cavity and swallowing is called ingestion.
Digestion of Food in the Mouth
During mastication, the food is mixed thorougly with the saliva while the food is in the oral cavity (buccal cavity). The saliva is secreted by three pairs of salivary glands located in the buccal cavity. The saliva is continuously secreted by the salivary glands in response to the presence of food in the buccal cavity.
Saliva is alkaline and contains an enzyme ptyalin. This enzyme converts starch into sugar (maltose). The morsel of food after being chewed and thoroughly mixed with the saliva is called a bolus. It is rolled down by the swallowing action into the oesophagus which conveys it to the stomach by the wave of peristalsis. The end of stomach lined with oesophagus is called cardiac end.
Digestion of Food in the Stomach
Stomach is a thick sac like structure, in which food is stored for some time. Its wall is strong and muscular. Its inner surface has numerous glands called gastric glands. These glands secrete a juice called gastric juice. Human stomach secretes about one to two liters of this juice daily; Gastric juice contains Hydrochloric acid and two enzymes, renin and pepsin. Hydrochlroic acid changes the medium of food to acidic. This medium kills the bacteria that may be found in the food. the pepsin acts on proteins and breaks them down into peptones. Renin helps to curdle milk in infants. There is no chemical action on carbohydrates and fats present in food. the regular movements of the stomach churn up the food. the food is changed into a thick fluid called chyme. When digestion in the stomach is complete, the distal end of the stomach called the pyloric end relaxes, and allows a small amount of chyme to pass into the first part of the small intestine. Food stays in stomach for about 2-3 or 3-4 hours.
Digestion of Food in the Small Intestine
Food from stomach enters the duodenum which is the first part of the small intestine. An alkaline pancreatic juice from the pancreas and bile juice from the liver and poured into the duodenum by a common duct. Both the juices contain bicarbonates which neutralize the acidic chyme and make. It rather alkaline besides these juices other intestinal juices from the walls of the small intestine are also poured. These entire juices act on food and help in digestion of food.
Liver
It is largest gland, in the body. Its colour is reddish brown. It lies just below the diaphragm on the right side of the body under the ribs. It has five lobes, three on the right side and two on the left. The cells of the liver secrete a greenish yellow alkaline fluid which is called the bile juice. It contains bile salts and bile pigments which give greenish yellow colour to the juice. Bile contains no digestive enzymes, but it does contain bile salts which break down the large molecules of fats to small fat droplets. This process is called emulsification. This process helps in the digestion of fats. Bile juice also contains bile pigments that are by products of red blood cells, these pigments are eliminated from the body along with the faeces, and the colour of faeces is due to these pigments. Besides this, bile juice also kill the germs in the food.
Functions of Liver
1. Liver stores glycogen and regulates the level of glucose in the blood.
2. It breaks down excess amino acids. this process is called deamination.
3. It is involved in detoxification.
4. It produces and secretes bile juice which is stored in the gall bladder.
5. It metabolizes carbohydrates, fats, proteins and other compounds.
6. As a result of chemical changes a lot of heat is produced, therefore liver helps to keep the body warm.
7. It makes fibrinogen and other blood proteins.
8. It decomposes the damaged red blood cells.
Pancreas
It is a leaf like organ. It lies below the stomach and between the two arms of duodenum. The pancreas produces a juice which is called the pancreatic juice. This juice flows down the pancreatic duct into the duodenum. It contains three enzymes.
1. Pancreatic amylase which acts on undigested starches of the food and converts them into maltose.
2. Enzyme trypsin which breaks down proteins into peptides.
3. Lipase which splits fats into fatty acids and glycerol.
If any of the constituents of food still remain undigested, enzymes secreted by the glands in the small intestine act upon them and complete the digestion by converting peptides to amino acids, maltose and other sugars to glucose and fats to fatty acids and glycerol.
The enzymes secreted by the intestinal walls are amino-peptidases and disaccharidase,(which form glucose from maltose, lactose and sucrose). In this way food is completely digested at intestine.

Enzymes

Definition of Enzymes
Enzymes are chemical compounds. They are protein in nature. They are formed in living cells. They are not consumed in a reaction but act as a catalyst as they only speed up the chemical reactions.
Types of Enzymes
There are two types of enzymes:
1. Intracellular Enzymes
2. Extracellular Enzymes
1. Intracellular Enzymes
They work within a cell, in which they are produced.
2. Extracellular Enzymes
Some enzymes are secreted out of the cells where they work. They are called extracellular enzyme. Bacteria and fungi secrete such extra cellular enzymes into the medium in which they are growing. The higher organisms secrete extracellular enzymes into the lumen of alimentary canal to act on the food.
The enzymes acting on the starch are known as Amylases; those acting on proteins are known as Proteinases, while those acting on fats are known as Lipases.
Characteristics of Enzymes
The characteristics of enzymes are as follows:
1. All enzymes are protein in nature; they can be destroyed by heating.
2. They act best within a narrow, temperature range.
3. They work efficiently in narrow range of acidity or alkalinity.
4. A particular enzyme forms the same end-product, because it acts on a particular/specific substrate

Light and Dark Reactions

Light Reactions
When light falls on the leaves, it is absorbed by chlorophyll. The solar energy is used to split water into oxygen and hydrogen and this is called photolysis (photo means light and lysis means to break). The oxygen is released into the atmosphere as by-product of photosynthesis. As this process takes place only in the presence of light, it is called light reaction.
During light reaction, two compounds are formed when the solar energy is converted into chemical energy these are:
1. NADPH (Nicotinamide Adenine Dinucleotide Phosphate)
2. ATP (Adenosine Triphosphate)
NADP, already exists in the cells of the leaf. The hydrogen released on the splitting of water molecule is accepted by this compound and it is reduced to NADPH.
ADP (Adenosine Diphosphate) is already present in the cell; it combines with the phosphate group using light energy to form a compound called ATP.
These compounds are energy rich compounds which are needed for the dark reactions of the process. Light reaction is called high dependent reaction.
(Diagram)
Dark Reactions
Using the energy of ATP and the NADPH, water combines with carbon dioxide to form carbohydrate. Thus the solar energy is now converted into chemical energy to form glucose. Other organic compounds are also synthesized from this glucose.
This stage is completed in a series of chemical reactions with the help of enzymes. Neither light energy nor chlorophyll is needed for dark reactions. Therefore dark reaction is also called light independent reaction.
Various steps of the dark reactions were studied by a scientist called Melvin Calvin so the dark reaction is also called the Calvin’s Cycle.

Chordata and Vertebrata

Characters of Class Pisces (fishes) 1. The class of fishes is called Pisces. They are aquatic vertebrates.
2. According to their size and shape, the fishes are of many kinds.
3. They have a head, a trunk and a tail.
4. The head and trunk are directly jointed together and neck absent.
5. Body of fish is flexible tapering at both ends and streamlined. This type of body helps in swimming.
6. They can swim with fins, which are attached to the trunk.
7. They body is covered with scales which remain moist by special type of secretion of body.
8. Breathing organs are gills which are present in the hollow spaces found on both sides of the head for exchange of gases i.e. oxygen and carbon dioxide.
9. Mouth has teeth, which is used for grasping instead of grinding of food.
10. In some fishes air pouch is present, which is called air bladder. The air bladder is used for buoyancy.
Class Amphibia
1. This group of animals can live both in water and on land.
2. They need water for reproduction. Therefore they are called Amphibians.
3. The skin is thin, moist and slimy.
4. Small teeth are present in the upper jaw which is only used for grasping the prey.
5. Breathing organs are two lungs. Skin is also used for the exchange of gases.
6. Eggs are laid in water or moist places and their outer shells are not hard.
7. They are cold blooded animals e.g. they cannot maintain their body temperature constant.
8. They become very slow and bury themselves in the mud. This process is called hibernation.
9. During the process of reproduction fertilized egg is changed into adult passing through a number of physical changes. This process is called metamorphosis.
10. The fertilized egg develops into larva. The larva of frog is called Tadpole. It has tail and gills. This larva later changes into adult.
Class Reptilia
The animals of this class are called reptiles. They have following features.
Reptiles
1. Most of the reptiles are terrestrial and only a few five in water.
2. They are also called crawlers.
3. They have thick, dry and rough skin.
4. The skin is covered with scales which originate from the ectoderm.
5. There are present lungs for respiration.
6. Teeth are present in their buccal cavity, which are used for cutting and biting.
7. The locomotary organs are legs but snakes and a few types of lizards have no legs.
8. Most of the lizards are not poisonous except members of the genus Heloderma which are found in American desert.
9. All the reptiles lay their eggs on land. Water dwelling reptiles e.g. turtle also lay their eggs on land.
10. Their eggs have a tough outer shell of calcium carbonate.
Class Aves
The animals included in this class are called Birds. Their distinguishing characters are as follows.
1. Birds have a single unique feature, which makes them different from other animals which is the presence of feathers. Their forelimbs are modified to form wings while hind limbs help in walking, wading and sitting on the branches.
2. All the birds have horny beaks without teeth.
3. All the birds lay eggs.
4. All the birds must have two wings for support and propulsion, strong but light and hollow bones.
5. Their digestive system is able to digest high caloric food.
6. They have a higher blood pressure and higher metabolic rate.
7. Nervous system and especially eye sight is very well developed so that they can track their path even at a very high speed.
8. They migrate during winters towards warmer places covering thousands of miles.
9. It is the most studied and most observable class in the world.
10. The birds are very beautiful and have melodious voices.
Types or Groups of Birds
Running Birds (Ratitae)
They have following characters:
1. They have flattened sternum.
2. Their pectoral muscles are weak.
3. Their examples are Ostrich, Emu, Rhea and Casso wary.
Flying Birds (Carinatae)
They have following characters:
1. A keel is present on sternum in these birds.
2. Keel is vertical bony part that is present below the sternum in the centre from anterior to posterior end.
3. Pectoral muscles are very strong, powerful and are inserted on the keel. These muscles help them to fly.
4. Their common examples are pigeon, hen, crow, kite etc.
Class Mammalia
All the animals included in this class are called “mammals”. These animals are highly advanced vertebrates. There are almost four thousand species of mammals including man.
Characteristics of Mammals
Their distinguishing characters are given below:
Hair
The body of mammals is covered with hair. In most of the mammals hair may cover the whole body but in a few may be restricted to some areas. The hair conserves heat of the body.
Glands
Their skin is provided with sweet glands, scent glands, sebaccous glands and mammary glands.
Skeleton
Two occipital condyles, secondary bony palate, three bones in middle ear and fused pelvic bones and seven cervical vertebrae are present in their skeleton.
External Ear
Fleshy external ears are present in mammals.
Eyelids
Moveable eyelids are present in mammals.
Teeth
Two sets of teeth are present. Milk teeth are replaced by permanent set of teeth.
Brain
Brain is higly developed. It perform more functions than that of other vertebrates.
Cranial Nerves
Twelve pairs of cranial nerves are present.
Circulatory System
Circulatory system has four chambered heart, persistent left aorta and non-nucleated biconcave red blood corpuscles are present in female.
Sexes
Sexes are separate i.e. there are two individuals, male and female.
Fertilization
Most of them have internal fertilization and fetus developed inside the uterus of female giving birth to their children.
Breast Feeding
They feed the children by milk from mammary glands.
Endothermic
They are endothermic i.e. they can maintain their body temperature according to the environment. It means that they are warm-blooded animals.
Egg Laying Mammals
These mammals lay eggs. Mostly two eggs are laid in one year. Fertilization of egg is internal i.e. inside the body of mother. Eggs are laid in burrows of animals. Young ones are hatched from the eggs. Mother feed their children with milk. Their egg laying character shows their relationship with reptiles. Duck bill platypus and Spiny ant eater are the examples of egg laying mammals.
Pouched Mammals or Marsupial Mammals
These mammals have a pouch outside the belly called marsupium, this is the reason that they are also known as Marsupial mammals.
1. Fertilization of eggs and development of embryo is internal.
2. The embryo is at first encapsulated by shell membrane and floats free for several days in the uterine fluid.
3. There is no placenta.
4. After hatching from the shell membranes, the embryo does not implant or “take root” in the uterus and absorb nutrient secretions from the vascularized yolk sac.
5. The gestation period is brief and the marsupials give birth to tiny young that is effectively still an embryo.
6. These young creeps into the marsupium where it gets milk from mother through nipple.
7. It lives in marsupium until it can take care of itself.
8. Examples are Kangaroo, Koala, Tasmanian wolf and Wombat etc. These are found in Australia and Tasmania, Opossum is found in America. It lives on trees.
Placental Mammals
This is common group of mammals in which embryo completes its development inside the mother’s uterus. After gestation period young ones are born. Embryo remains in the uterus and gets its nourishment from mother through umbilical cord and placenta. Gestation period of these mammals is longer than those of other mammals. Pregnancy is called Gestation Period. In man it is of 9th months.
In mice it is 21 days, in rabbit 30 to 36 days, in cats and dogs 60 days, in cattle 250 days and in elephants 22 months. It is lengthier in large mammals.
The conditions of young ones at time of birth are different in different mammals. For example in antelope, at the time of birth, the body of young is covered over, with heavy fur, eyes are open and it can walk about. In case of rat, young is very weak, eyes are closed and has no hair on the body.
Flora and Fauna of Pakistan
Flora
Definition
“Different types of plans present in a particular region constitute its flora.”
Details
1. Hilly regions of Pakistan have snow fall and low temperature. These regions have thick forests where trees of Juniper (Sanober), Cedar, Chir, Chalghoza, Olive Apple, Plum Peach and Loqaut are very common.
2. Plain areas of Pakistan have fertile and less fertile soils. In areas where rainfall is low, desert environment is present in which Aeacia (Babool), Kikar, Ber, Pilas etc grow.
3. Fertile plains have trees of Sheesham, Bakain, Cane, Bamboo and Eucalyptus. These are source of timber whereas; fruit trees include mango, banana, Kino, Orange, Grapes, Jamman etc.
4. Plain and hilly areas have natural pasture lands that provide fodder for cattle.
5. In sea, rivers, ponds, canals and streams, algae are abundant, which on one hand are the source of food for aquatic animals and on the other hand they provide oxygen to atmosphere.
6. A large number of plants are used as ornamental plants. These include flowering plants like rose, motia, jasmine, lady of night, chrysanthemum etc.
7. Besides this wheat, maize, rice, oats, burley, grams garlic, onion, potatoes, carrots, cabbage and turnips etc are cultivated in plains and hilly areas to meet our food requirements.
Fauna
Definition
“Different kinds of animals present in a particular region are known as its Fauna.”

Detail
1. In the seas adjoining our coastal areas numerous types of animals are found starting from protozoa to mammals. The most noticeable are octopus, mussels, star fish, sea urchins, crabs, prawns, fishes, amphibians, whale, dolphin etc.
2. Many animals are used as food e.g. prawns, crabs and fish etc. Our rivers are rich in fish life particularly Rohu, Khagga, Malhi, Trout, and carps are abundant and used as human food, as well as a source of earning lively hood.
3. Frogs and toads are abundant.
4. The tortoises, turtles, snakes, crocodiles are also common.
5. On the plains of Pakistan we have very rich wild life. There is a great diversity of land fauna starting from earthworms, almost all kinds of insects, spiders, myriapods, snails, slugs to toads, lizards, snakes and enormous variety of birds and mammals.
6. Some of the birds peculiar to Pakistan are Houbara bustard, partridge, pheasant, falcons etc.
7. The mammals peculiar to Pakistan include Black buck, Blue ball, Brown bear, Musk deer, Urial, Ibex, Asiatic ass.etc.
8. Most of the animals provide milk, meat, hide and wool. Some are used for transportation. Some of the animals are now endemgered species because of their excessive hunting and pollution.
WARM BLOODED ANIMALS
The animals which do not change their body temperature with the change of temperature in environment are called as Warm Blooded Animals. Their body temperature remains constant.
Example
Common examples of warm blooded animals are following.
(i) Parrot
(ii) Sparrow
(iii) Pigeon
(iv) Ostrich
(v) Kiwi
(vi) Duck billed platypus
(vii) Kangaro
(viii) Oppossum
(ix) Elephant
(x) Whale
(xi) Monkey
(xii) Man
COLD BLOODED ANIMALS
The animals in which the body temperature is changed with the changes of temperature in the environment are called Cold Blooded Animals.
Example
Common example of cold blooded animals are following.
(i) Shark
(ii) Labeo (Rohu)
(iii) Trout
(iv) Hilsa (Pullah Fish)
(v) Cat Fish (Khagga)
(vi) Frog
(vii) Toad
(viii) Snake
(ix) Wall-Lizard
(x) Crocodile

Invertebrata

Protozoa 1. According to two-kingdom classification, protozoa are the first phylum of invertebrate animals but according to five kingdom classification it is placed in a separate kingdom, “protista” in which all other eukaryotic unicellular organisms are also placed.
2. Body of all protozoans consists of one cell and istherefore called unicellular.
3. They are so small in size that they cannot be seen with naked eye. They can be seen with the help of a microscope.
4. They are unicellular but they intake food, respire, reproduce.
5. Protozoans mostly live in damp, watery places. Their habitat is mostly moist soil, decaying matter of animals and plants. Most of them live singly but some form colonies. In a colony, unicellular organisms become partially interdependent and limit themselves to perform specific functions in a group. If separated from group they still can perform all life activities and can live independently.
6. Some protozoans are parasites and causes different diseases e.g. a type of Amoeba causes dysentery, plasmodium causes malaria.
7. Protozoans are also useful for man because they feed and destroy bacteria which are harmful for human health, for example Amoeba can feed on bacteria.
Paramecium
It is unicellular animal which is found in pools and ponds. It is slipper shaped its body is covered with cilia. Cilia are small hair like out structures arising from protoplasm. Their lashing movement in water acts as oars and help in swimming (locomotion) of the animal. Paramecium feed on algae. Bacteria and other small protozoans, through an oral groove provided with cilia. Cilia push food inside the protoplasm through a canal called gullet making a food vacuole in the protoplasm. There are two contractile vacuoles, one at each end of the body for discharging surplus water there are two nuclei one large, mega nucleus which controls almost all functions of cell other small, micro or reproductive nucleus which controls reproduction. Many protozoa like Amoeba and Paramecium are unicellular but they respond to the intensity of light like all other multicellular organisms. They can detect high intensity of light and move towards the area having low intensity of light.
Phylum Porifera
1. This phylum is called porifera because animals belonging to this phylum have numerous small pores on their bodies.
2. They are also called sponges.
3. They are multicellular but they have no organs or true tissues.
4. Every cell performs its all function.
5. Sponges are aquatic animals. Most of them are found in sea water but some live in fresh water.
6. Sponges have different colours.
7. Green colour of sponge is due to algae that live in their body. Algae produce oxygen during photosynthesis which is used by sponges and the sponges release carbondioxide, which is used by algae for photosynthesis. This association in which both the organisms benefit from each other is called mutualism.
Phylum Cnidaria
1. Animals belonging to this phylum have a special cavity in their body which is called coelenteron and due to this reason they are called coelenterates.
2. They are diploblastic animals as their bodies have two layers of cells. Outer layer is called ectoderm and inner layer is called endoderm. Between these layers a jelly like substance the mesoglea is present.
3. Coelentrates are aquatic animals. They are mostly marine but few live in fresh water.
4. Most of the animals of this phylum can move freely but a few remain attached to stones or rocks throughout their life.
5. Hydra, Jellyfish and Sea anemone are common examples of this phylum.
Phylum Platyhelminthes
They are triploblastic animals because their body is made of three layers, an outer ectoderm, a middle mesoderm and an inner endoderm layer. They are also called flat worms because their body is thin, flattened and tape like. Some animals are free living but most are parasite. Parasites live in liver, stomach and intestine of other animals. They attach themselves to the walls of intestine of their host by sucker and suck blood and food. Tape worm sucks food from intestine and sometimes grows up to 40 feet in length. Liver fluke, tape worm and planaria are common examples of this phylum.
Phylum Mollusca
1. This phylum is one of the largest phyla of animal kingdom. It has about fifty thousand species.
2. Mollusca are a latin word which means “soft”. Their body is soft so in most of the animals and external shell is present for support and protection.
3. Some animals have internal shell and some lack shell. They are also known as shell fish.
4. They are found in aquatic and moist habitat.
5. Most of Mollusca are used as human food.
6. Buttons are made from their shell.
7. The pearls are produced by these animals.
8. Their body is quite complicated.
9. They have a muscular foot for locomotion and gills for respiration.
10. Snails, Fresh water mussel, Cuttle fish, Octopus and Oyster are common examples of this phylum.
Phylum Arthropoda
1. The bodies of these animals are also segmented but these segments are external.
2. Their bodies are covered with the hard shell composed of chitin, forming an exoskeleton.
3. They have jointed legs on their body and therefore they are called arthropoda (arthro means jointed and poda means foot)
4. These animals are found in all habitats, in air, water and on land.
5. Common examples are Prawn, Crab, Spider, Scorpion, Centipede, Millipede and Insects.
Phylum Echinodermata
1. The animals of this phylum are exclusively marine.
2. They are called echinoderms because their bodies are covered with spines or spicules.
3. All animals have internal skeleton consisting of dermal caleareous ossicles.
4. They have a water vascular system and dermal gills.
5. These animals are considered to be closest to the chordates from evolutionary point of view, Sea star (known as star fish). Brittle star, Sea urchin and Sea cucumber are examples of this phylum.
Phylum Annelida
1. Animals in this group have elongated segmental body.
2. Annelids occur in water as well as on land.
3. They have well developed systems in their bodies.
4. They have close type circulatory system.
Phylum Nematode
1. Nematodes or round worms have long smooth cylindrical body which is pointed at both the ends.
2. The body is un-segmented.
3. Nematodes have a complete and one way digested tube.
4. They are free-living as well as parasites of animals, man and even plants

Bryophytes and Tracheophytes

Bryophytes Bryophytes are on of the two main groups of kingdom ‘Plantae’ the second being the ‘tracheophytes’. Bryophytes is a group of plants which are multicellular, photosynthetic eukaryotes; and their reproductive organs are multicellular; their zygote develops into small, protected embryo that develops into a complete new hence bryophytes have also been called embryophytes. The cell of these plants is made up to cellulose.
Characteristics of Bryophytes
The important characteristics of Bryophytes are as follows:
1. Bryophytes are plants without vascular tissue (xylem a phloem), whereas tracheophytes have vascular tissue. Therefore tracheophytes are vascular plants, whereas bryophytes are non-vascular plants.
2. Bryophytes are the simplest land plants. Bryophytes divided into three groups. Liverworts, hornworts, and mosses.
3. Marchantia is an example of liverworts; its plant body is a thick branched green thallus.
4. Anthoceros is a horn wort, and Funaria is a moss.
5. All bryophytes and generally found growing in moist habitants such as damp soil and rocks, moist brick walls, and along the banks of streams.
Life Cycle of Funaria Moss
It is a common moss found grwoing t moist places. Green leafy, moss plant of Furania, as like all Bryophytes, Funaria is haploid gametophyte, its height is about 0.5 – 1 inch.
(Diagram)
Gamatophyte Generation
It consists of 3 parts:
1. A vertical stem like structure.
2. Leaf like photosynthetic structures arranged on the stem, which are composed of a single layer of cells, and without stalk.
3. Numerous multicellular rhizoids, arising from the lower side of the stem and which absorb water and salts, and anchor the plant to the soil.
Male sex organs, called antheridia (singular antheridium) are located at the tip of male branch, and the female sex organs, called archegonia (singular archegonium) are located at the tip of female branch.
Fertilization takes place in the presence of water within the archegonium located at the tip of female branch. The zygote develops into the embryo (2n). The embryo forms the sporophyte (2n). The sporophyte remains attached to the tip of female branch. The sporophyte gets water, slts and also part of its food, from the parent gametophyte plant.
Sporophyte Generation
The sporophyte consists of three parts:
1. A foot
2. A long stalk like seta
3. Capsule
The foot is anchored to the female branch and absorbs nutrients from the gametophyte. The seta elevates the capsule in the air. Within the capsule, haploid spores are produced by meiosis. The spores are dispersed by wind. Each spore develops eventually into new haploid gametophyte plant, and the life cycle continues.
Like other bryophytes, Funaria also has well defined alteration of generations; haploid gametophyte generation is dominant, whereas diploid sporophyte is attached to and more or less dependent on the gametophyte.
Pteridophytes
1. Unlike bryophytes the plant body in Pteridophytes is differentiated into root, stem and leaves.
2. In contrast to other vscular plants Pteridophytes do not bear flowers, fruits and seeds.
3. Due to presence of vascular tissues, they are similar to gymnosperms and angiosperms.
4. Although the dominant generation in Pteridophytes is also the sporophyte but unlike gymnosperms and angiosperms both sporophyte and gametophyte generations are independent and free living. However, the gametophyte in much reduced and smaller in size.
Spermatophytes
Seed plants or Spermatophytes are that group of vascular plants which produce seeds. Seed is a ripened ovule. It contains a young plant with embryonic root, stem and one or more leaves, which has stored food material and is protected by a resistant seed coat or testa.
Spermatophytes like pteridophytes possess vascular tissues. They also have life cycles with alternation of generations. Unlike bryophytes and pteridophytes, spermatophytes do not have free living gametophyte; instead the gametophyte is attached to and nutritionally dependend upon the sporophyte generation.
Main Groups of Spermatophytes
Gymnosperms
They produce seeds which are totally exposed or borne on the scales of cones.
Angiosperms
They are flowering plants which produce their seeds within a fruit.
Pinus and Thuja – The Typical Gymnosperm
Pinus is normally grows at an altitude of 5000 ft to 8000 ft. It has many types e.g. chir, kail, chilghoza etc. However, some species are found in the plains. It is also grown as ornamental plants. Pinus tree is a sporophyte, which is evergreen and quite tall. It consists of an extensive root system and a strong, stout and woody stem and its branches. The upper branches progressively become shorter in length. In this way, the tree assumes a symmetrical conical shape.
(Diagram)
Thuja
Thuja (common known as Mor Pankh) is a short tree. It has profuse branches, which are covered with small, dark green scale leaves. It is conical in appearance. It is grown as ornamental plant in parks and homes.
Leaves of Thuja
Thuja has small scale like green leaves that cover the stem.
Female Cone of Thuja
In Thuja the female cones are spherical or oval in shape. These are about the size of a bair (berry). They consist of hard, brown colour scales with triangular apices.
Pinus
Pinus has two types of shoots.
Shoots of Pinus
Long Shoots or Shoots of Unlimited Growth
They are formed on the main stem and continue growth indefinitely by buds borne at their apices. They are covered by scale leaves.
Dwarf Shoots or Shoots of Limited Growth
These shoots originate in the axils of the scale leaves on the long shoots. They are very short (only a few millimeters in length). Each dwarf shoot bears 1 t 5 foliage leaves in addition to scales leaves.
Leaves of Pinus
Scale Leaves
These are small, membranous and brown in colour. They cover the stem.
Foliage Leaves or Needles
These are commonly long and narrow, tough, and leathery. In contrast to scale leaves they are green and photosynthetic. Depending upon the type of species, a cluster of 2 to 5 needles is produced on each dwarf shoot. Each dwarf shoot with its cluster of needles is called a spur.
Reproduction in Pinus
Pinus tree produces reproductive structures known as cones every year. Cones are of two types, male and female c9ones. Both male and female cones are produced on the same tree but on different branches.
Male Cone of Pinus
Male cones, usually 1 cm or less in length, are much smaller than the female cones. They are produced in clusters. These are generally born on the lower branches of the tree. Each male cone is composed of spirally arranged leaf-like structures called scales or microsporophylls. Each microsporophyll has two long sacs called pollen sacs of microsporangia on it are under surface. Asexual reproductive cells, microspores or pollen grains are produced by meiosis in the microsporangia. Pollen grains are haploid. After being transferred to the ovule, the pollen grain forms pollen tube. It is the male gametophyte in which male gametes or sperms are produced.
Female Cone of Pinus
The female cones are much larger than the male cones. These are usually found on the upper branches. Each female cone is also made of spirally arranged scales which are called megasporophylls. These scales become woody on maturity. Two ovules are present side by side at the base of each scale. Haploid megaspores are formed in the ovule by meiosis. Measpores give rise to female gametophytes which produce female gametes. Fertilization results in the formation of embryo after which the ovule is ripened to form seed. Female cones normally remain attached for three years on the plant. On maturity the cones open up and the seeds are set free and dispersed.
Angiosperms
Angiosperms are the flowering plants which are most successful plants. They are more important than the gymnosperms. They have adapted to almost every type of environment. There are about at least 235,000 species. They are dominant plants. Angiosperms are vascular plants which bear flowers. Their seeds are produced within fruits. The fruit protects the developing seeds and also helps in their dispersal. Seed and fruit producing habit have helped flowering plants in their evolutionary success.
Angiosperms are found in wide variety of sizes and forms. Ensize they range from over 300 ft in height (some species of Eucalyptus) to searcely 1mm in length (duckweed, Woiffia).
On the basis of size and woody texture, angiosperms are classified as herbs, shrubs (bushes) and trees. Herbs are the plants which are small in size. Their stems are Herbs which are then cut or pulled from the soil. In contrast shrubs and trees have hard woody stems, which retain their shape even after being cut. Shrubs are shorter than trees but have more branches. In addition to tracheids, angiosperms have efficient water conducting structures known as vessels in their xylem.
Classes of Angiosperms
On the basis of the number of cotyledons in the seed, angiosperms are divided, into two classes.
1. Monocotyledons or Monocots
2. Dicotyledons or Dicots
Monocots
1. Monocot seeds have only one cotyledon or embryonic leaf.
2. A nutritive tissue called “endosperm” is usually present in the mature seed.
3. Monocots are mostly herbs with long narrow leaves.
4. Leaves have parallel veins i.e. in the lamina of the leaf veins run parallel to one another.
5. The floral parts of most flow3ers usually occur in threes or multiples of three (i.e. 3, 6, 9 …)
6. Monocots include different grasses, cereals (wheat rice, maize etc) ,palms, onions and lilies.
Dicots
1. Dicot seeds have two cotyledons.
2. In mature seed, te endosperms is usually absent.
3. Their leaves vary in shape but usually are broader than monocot leaves.
4. Leaves have reticulate veins i.e. branched veins resembling a net. The flower parts are four or five in number or multiples of 4 or 5.
5. Dicots include rose, peas and pulses, sheesham, Kiikar (Acacia), sarsoon (mustard), cacti, mango, orange and sunflower etc.

Fungi and Algae

Fungi
During rainy season, a large number of umbrella-shaped mushrooms emerge on dung-piles. Fluffy mass of tangled threads like structure with black-dots of molds is also often seen growing on orages and bread, these mushrooms and molds are fungi.
Characteristics of Fungi
1. Fungi are simple heterotrophic eukaryotes which cannot manufacture their food and have absorptive mode of nutrition (e.g. absorbed prepared food).
2. Cell wall is made up of Chitin instead of cellulose.
3. Some fungi are parasitic while others are saprotrophs.
4. Parasitic fungi obtain their food from other living organisms.
5. Saprotrophic fungi get their food from dead animals, plants, their wastes and decaying materials.
Economic Importance of Fungi
Fungi are useful as well as harmful to humans. e.g.
Useful Aspects of Fungi
Saprotrophic Fungi
Saprotrophic fungi chemically break down dead bodies of organisms and their wastes into simple components. They clean the environment and also cause the recycling of nutrients.
Mycorrhizal Fungi
Mycorrhizal fungi improve the growth production of crop plants.
Edible Fungi
Mushrooms and some other fungi are edible.
Antibiotics
Some antibiotics are also obtained from some fungi. For example, Penicillin, the first antibiotic discovered in 1928 by Alexander Flemming. Penicillin is obtained from the fungus penicillium.
Yeasts
Yeasts are used in making bread and alcohol.
Mushroom
1. During rainy season, a large number of umbrella like mushrooms emerge on dung piles.
2. Mycelium of mushroom is saprotrophic, spreading under group in the soil that contains, decaying and organic matter.
3. When spores are to be formed, many hyphae of mycelium come out of the soil to form umbrella shaped fruit bod, the familiar mushroom. It can be 3,4 inches in height.
4. Fruid body consists of two main parts; a lower stalk or stripe, and an upper umbrella shaped cap or pilens which bears annulus around it just below the cap.
5. On maturation, many radial plates or gills are seen on the underside of the cap on which enormous numbers of spores are produced.
6. Some mushrooms, like Agaricus, can be used as food before their fruit bodies become overripe. Agaricus is rich in protein. Some mushrooms, like Amanita, are deadly poisonous.
(Diagram)
Algae
Algae are a group of simple eukaryotes in which, like plants, chlorophyll is found. They are photosynthetic autotrophs and have cellulose in their cell wall. However unlike plants but ike fungi, their organs are unicellular and body is simple, thallus. Therefore they are placed in another kingdom, the Protista.
Algae, are mostly (found in water). A large number of algae are found in vast saltwater oceans. These are called marine algae, other are found in lakes, ponds, puddles, streams and rivers. These are called fresh water algae. Some marine algae, called the helps and grow as long as 60 meters or more in a season. Some of them are used as food.
Characteristics of Algae
1. All the algae have chlorophyll so they are autotrophic; they make their own food by photosynthesis.
2. Their cell walls are made up of cellulose.
3. Algae are mostly marine found in the sea. While others are found in fresh water lakes, ponds, puddles, streams and rivers and they are also found in damp soil.
4. Their plant body is called a thallus without a true root, stem or leaf.
5. Algae are sometimes classified on the basis of the pigments they contain. Their green colour can be masked by the presence of other pigments.
6. Their reserved food material is starch.
7. Algae have a wide variety from unicellular algae, e.g. chlamydomanas and spirogyra to multicellular large seaweeds like sargassum.
8. Previously algae were regarded as plants and were placed in thallophyta.
Chlamydomonas
It is fresh water green alga, commonly found in fresh pond and drains. It is single celled green algae which are seen only under a microscope.
Structure
1. Chlamydomonas is spherical, oval or pear-shaped.
2. The cell is enclosed by a cell wall which maintains its shape.
3. In the anterior part, the cell wall forms an outgrowth called apical papilla.
4. Two flagella (singular flagellum) arise from the cytomplasm below the apical papilla and come out through the cell wall. These help in swimming.
5. A thin cell membrane lies beneath the cell wall, it represents the ourter surface of cytoplasm.
6. In cytoplasm, there is, a cup shaped chloroplast, which is involved in production of food by process of photosynthesis.
7. The chloroplast contains, a spherical structure called pyrenoid in its posterior part, and a single red orange light-sensitive eye-spot on one side in its anterior regions.
8. The pyrenoid is supposed to store carbohydrates in the form of starch grains.
9. The eye spot helps chlamydomonas to determine its position nd direction according to changes in the intensity of light.
10. There are two contractile vacuoles near the base of flagella ‘which periodically expel excess water and waste from the cell.
11. A nucleus is present in the middle of chloroplast in the cytoplasm.
12. Although body, of chlamydomonas consists of a single cell, yet it performs all the basic functions of life. It reproduces both sex and asexual.
(Diagram)
Spirogyra
1. Spirogyra is a multicultural filamentous green alga. It is found in great abundance in fresh water ponds, lakes and streams. Its filamentous thallus consists of cylindrical cells.
2. These cells are joined end to end, to form un-branched filaments. Usually the filaments are found occurring in a large number.
3. The filaments are surrounded by a layer of mucilage that makes them slippery.
4. During day time, the oxygen produced during photosynthesis stores in the mucilage and the filaments start floating on the surface of water.
5. Each cell of Spirogyra is usually twice as long as broad.
6. The cell is surrounded by cellulosic cell wall. A peripheral layer of cytoplsm is present just inside the cell wall and around a large, central vacuole.
7. The vacuole is filled with cell sap.
8. A single nucleus is suspended near the vacuole by cytoplasmic strand.
9. The most prominent part of cell is its chloroplast. There may be one ore more than one chlrorplasts in each cell. The chloroplasts run along the; length of the cell in the form of spiral ribbon in the peripheral cytoplasm.
10. Numerous pyrenoids are located in a row in the chloroplast and are meant for storing starch. Spirogyra continually grows in length by cell division.
11. Each cell can be divide into two, so filament increases in length. The Spirogyra reproduces both sexually and asexually.