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.
Carbohydrates
CarbohydratesThey 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.
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.
Difference between Prokaryotic Cell and Eukaryotic Cell
Difference between Prokaryotic Cell and Eukaryotic CellProkaryotic Cell
· The organisms made of prokaryotic cells are called prokaryotes e.g. bacteria and cyanobacteria.
· These cells lack a membrane bound nucleus. The hereditary material (DNA) is found in cytoplasm.
· These cells lack membrane bound organelles.
· Ribosomes are of small size in and freely scattered cytoplasm.
· Cellulose is absent in cell wall, rather it is made up of peptido-glycan or murein.
· These cells are simple and of smaller size (average diameter 0.5 – 10 nm)
Eukaryotic Cell
· The organisms mae of Eukaryotic cells are called Eukaryotes, e.g. animals, plants fungi and protists.
· These cells have a membrane bound nucleus; and hereditary material is found inside the nucleus.
· These cells have membrane bound organelles.
· Ribosomes are of large size and are present in endoplasmic reticulum free in cytoplasm.
· Cellulose is present in cell wall of plant cells. The cell wall of most of fungi is composed of chitin.
· These cells are complex and of larger size (Average diameter 10-100nm)
Digestion of Food
Digestion of FoodFirst 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.
Electron Microscope
Electron MicroscopeThis is the most advanced form of microscope. Its resolving power is 250 times or more that of a compound microscope. In this microscope, a beam of electrons under high voltage is passed through the object and its image is reflected on to a screen through an electro magnetic lens to make a photograph.
(Diagram)
With the help of microscope, any object an be magnified up to 250,000 its original size.
Comparison of Light Microscope and Electron Microscope
Light Microscope
The radiation source is light so it is called light microscope.
Wavelength of light is 400 – 700 nm.
Maximum resolution is 200 nm.
Maximum useful magnification is X 1500 with eye.
Lenses are used.
Electron Microscope
The radiation source is beam of electrons, so it is called Electron Microscope.
Wavelength of beam of electrons is 0.005 nm.
Maximum resolution is 0.5 nm.
Maximum useful magnification is X. 250,000 on screen as image or photograph.
Electromagnets are used.
Enzymes
Definition of EnzymesEnzymes 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.
Fats and Oils
Fats and OilsThey are also organic compounds found in plants, animals and humans. They are very important compounds made up of carbon, hydrogen and oxygen. Fats contain more carbon and hydrogen as compared to oxygen. A fat molecule has two parts, glycerol and fatty acids.
Fatty Acids
Different kinds of fats contain different fatty acids. Fatty acids are basically of followin two types:
1. Unsaturated Fatty Acids
2. Saturated Fatty Acids
Unsaturated fatty acids (molecules with one or more than one double bonds) are liquids at room temperature and are called oils. These are good for human health. Saturated fatty acids (molecules without double bond) are solid at room temperature and are called fat. They are not good for human health because they increase cholesterol level in the body. They cause narrowing of blood vessels which may result in heart attack.
Vegetable Sources
Vegetable fats are liquid and are called oils e.g. mustard oil, olive oil, coconut oil, corn oil. etc.
Animal Sources
Animal fats are solids e.g. butter, ghee and fatty meat.
Source of Energy
Fats and oils are rich source of energy they provide double energy as compared to carbohydrates and proteins. One gram of fat on oxidation releases 9.1 kilo cal of energy to make ATP
Frog
FrogFrog is found in he water or near the water. It belongs to class Amphibia. it passes a specific part of life in water and remaining life on land. Its bilogical name is Rana Tigrina. It is a cold blooded animal i.e. blood temperature changes with that of the environment. At the start of winter, water is decreased and temperature is lowered, the frog lives buried in the mud to over come winter.
(Figure)
Coelom
The body cavity of frog is called Coelom. It contains many organs which form different systems.
Digestive System of Frog
This system consists of alimentary canal and accessory glands like liver and Pancreas.
Alimentary Canal
It is a coiled tube through which food passes. It consists of buccal cavity, pharynx, oesophagus, stomach and intestines.
Buccal Cavity and Pharynx
Mouth is present between upper and lower jaws. Upper jaw has a row of pointed maxillary teeth. Lower jaw lacks teeth. There is a pair of set of vomerine teeth on the roof of the buccal cavity. Frog does not chew the food with teeth. But teeth are used only to grasp the food. The old teeth are continuously replaced by the new teeth through its life. Near the vomerine teeth, internal nostrils are present on the roof of the buccal cavity. These open outwards into external nostrils. Behind them, two large bulges indicate the position of eyes. The tongue of frog is sticky. The tongue is attached at anterior end of buccal cavity. The posterior end of tongue is free and bifid. the frog feeds on different insects. To capture its prey, it suddenly throws its tongue on to the prey, which sticks to the tongue and is brought to the buccal cavity, when the tongue is drawn back.
Near the maxillary joints, pair of opening of eustachian tubes are present. In male frog, there is also, present a pair of opening of vocal, sacs on the lateral side of floor of the buccal cavity which help the croaking. Buccal cavity narrows, posteriorly to form pharynx. The digestive system, respiratory system and ears are linked to pharynx. In posterior part of pharynx, there is another opening called Glottis. This leads to lungs through tachea. It closes at the time of digestion of food but remains open when animal is respiring.
(Diagram)
Oesophagus, Stomach and Intestine
Pharynx leads into a small but wider tube called oesophagus or gullet. The oesophagus opens into the stomach. The anterior end of stomach is called Cardiac end while the posterior end is called Pyloric end. The walls of stomach are muscular and glandular.
The muscles of walls of stomach contract and relax, by which food is broken down into tiny pieces. The secretions of stomach have different enzymes which help in chemical digestion. In stomach, digestion of protein of food is started. After stomach, first part of intestine begins which is called duodenum. The ducts from liver and pancreas open into the duodenum. These ducts bring juices from these glands. The second part of intestine is Ilium are called Small intestine. The secretion of pancreas is called Pancreatic Juice. Pancreatic juice enters the bile duct by small duct. This juice digests the food and brings in such form which can be absorbed by the blood through intestine. Digested food is absorbed by illium and surplus water is absorbed by recturm. Remaining undigested food is expelled though cloacal aperture. A membrane keeps the intestine intact at a place and prevents strangulation of small intestine. This membrane is called mesentery.
Respiratory System of Frog
There are three methods of respiration in frog.
· Pulmonary Respiration
· Cutaneous respiration
· Buccal Respiration
(Diagram)
Pulmonary Respiration
The exchange of gases through lungs is called pulmonary respiration. In this process, frog keeps its mouth closed. Air reaches buccal cavity through nostrils. Nostrils are closed floor of buccal cavity is raised; glottis opens, and air is pushed into the lungs. The intake of air is called inspiration. In frog, there is a pair of balloon shaped lungs. Each lung consists of small thin walled chambers called alveoli which greatly increase the surface area of the lungs. On each alveolus, there are many blood capillaries. When lungs are filled with air, then exchange of gases occurs between blood and air in lungs at the site of alveoli. During this, the exchange of gases occurs between blood and air present in buccal cavity. After this air is removed from the lungs. Frog uses its nostrils and floor of buccal cavity for inspiration and expiration.
Oxygen present in the air is dissolved in moisture present on lining of lungs. Then oxygen is diffused into the blood where it combines with hemoglobin to form oxyhaemoglobin. This oxygenated blood goes to all parts of the body by means of capillaries. Where oxygen separates from oxyhaemoglobin molecules and is absorbed by the cells. Carbon dioxide from cells comes out into the blood, which carries it to the lungs, and from here carbon dioxide is expelled.
Cutaneous Respiration
In frog, exchange of gases occurs through skin during hibernation and swimming. This is called cutaneous respiration. Skin is richly supplied with capillaries. Skin is moist. Oxygen diffuses through skin to capillaries and is carried by blood and CO2 diffuses back to blood from cells and is discharged out.
Circulatory System of Frog
It consists of blood vascular and lymphatic systems.
Blood Vascular System
The blood vascular system of frog consists of following parts:
· Heart
· Arteries
· Veins
· Capillaries
Structure of Heart
Heart is conical organ. It is muscular. It has three chambers. It is present in the body cavity between the oesophagus and sternum. Like a pump, it contracts and is relaxes. As a result of this, blood continuously circulates in the body. The heart is surrounded by a membrane which is called pericardial which protects the heart.
(Figure)
The three chambers of heart are as follows:
1. Right Atrium
2. Left Atrium
3. Ventricle
the two atria form the broader interior part of the heart. The right atrium is larger than left atrium. Both atria are thin walled. The posterior conical thick walled part of the heart is called ventricle. A broad vessel, which is called truncus artenosus, arises from dorsal side of the ventricle and then divides into two branches near the atria. A thin walled triangular sinus venosus opens into the right atrium. Some biologists consider truncus arteriosus and sinus venosus as chambers of the heart.
Function of Heart
· The chambers of the heart beat in a rhythmic way.
· First of all sinus venosus contracts. Then, the two atria contract. After this ventricle and finally truncus arteriosus is contracted.
· The deoxygenated blood from the whole body except lungs is carried to sinus venosus by two precavals and one post caval.
· Sinus, venosus opens into the right atrium through an opening.
· Oxygenated blood from the lungs is brought into the the left atrium by two pulmonary veins.
· Both the atria open into the ventricle and push their blood collectively into the ventricle by a common aperture, which is guarded by a valve.
· This valve maintains the unidirectional flow of blood in the heart and prevents the back flow of blood.
· In the middle of ventricle some mixing of oxygenated and deoxygenated blood takes place. On the two sides the blood remains unmixed due to rapid flow of blood.
· When ventricle contracts the blood goes to the truncus arteriosus through an aperture. This aperture controls the speed and direction of the blood by a spiral valve present at the start of truncus arteriosus.
Arterial System of Frog
The blood vessels which carry the blood from heart to different parts of the body are called arteries. The system consisting of arteries is called arterial system.
(Diagram)
It starts from truncus arteriosus. It is divided into two main branches each of which further divides to form three small branches.
Carotid Arch
It supplies blood to lower jaw, tongue, eye and brain.
Pulmocutaneous Arch
It carries blood to lungs and skin.
Systemic Arch
Right and left systemic arches joint posteriorly to form dorsal aorta. But prior to their union, each systemic arch gives out arteries supplying blood to vertebral column, oesophagus and fore limbs.
Dorsal Aorta
It runs along the vertebral column towards hind limbs. It gives off following branches.
Coeliacomesenteric Artery
It supplies blood to digestive system.
Renal Arteries
These supply blood to kidneys and general organs.
Posterior Mesenteric Artery
It supplies blood to rectum.
Illiac Arteries
These supply blood to hind limbs of their sides.
After reaching their specific organs, all the arteries divide and redivide to form capillaries. The walls of capillaries are very thin. Due to this reason, the exchange of materials take place between blood and tissues. The capillaries join to form venules. These venules join to form veins. Then these veins carry blood back to heart.
Venous System
The blood vessels which bring the blood from different body parts, back into the heart are called veins. The system containing of veins is called Venous system.
Following are the major veins in frog.
Pulmonary Veins
Blood from right and left lungs goes to left atrium through pair of pulmonary veins. These have oxygenated blood.
Right and Left Precavals
Each precaval is formed by union of three veins which bring blood from tongue, lower jaw, head, shoulders, forelimbs and skin. Both veins open in sinus venosus. From here blood goes to right atrium.
Postcaval
It is formed by union of five or six pairs of renal veins from the kidney and the genital veins. While passing through the liver, it receives two hepatic veins. Then it enters the sinus venosus. Therefore, venous blood from different body parts enters the heart.
Renal Portal Vein
The veins which bring blood from the hind limbs and pelvic region combine to form Renal portal vein. The renal portal vein enters the kidney of its side and form capillaries. Blood from kidney goes to the post caval through renal veins. Post caval caries the blood to the heart.
Abdominal Vein
The Pelvic veins of two sides combine to form abdominal vein. Before entering the liver, it divides into branches. In liver, it is further divided to form capillaries. The blood from the liver is drained into post caval by hapatic veins of both sides.
Hepatic Portal Vein
The blood vessels (veins) bringing blood form various organs of digestive system (stomach, duodenum, illiums, rectum, pancreas and spleen etc) combine to form a large vein. This is known as hepatic portal vein. Near the liver a branch of abdominal vein combines with it. Then it enters the liver and divides and redivides to form capillaries. The, blood entering the liver through hepatic portal veins goes to the post caval by means of hepatic veins. The blood from post caval goes to heart through sinus venosus.
The blood coming back into the heart is of two types.
· Oxygenated blood which comes from lungs by pulmonary veins.
· Deoxygenated blood from all parts of the body enters sinus venosus through precavals and post caval and then enters the right atrium.
(Diagram)
Lymphatic System of Frog
In circulatory system, due to blood pressure, many components of blood plasma come out of the capillaries and fill the inter cellular spaces. These components are also in the form of fluid and called tissue fluid or interstitial fluid. Much of it reenters the capillaries and some of it enters the lymph vessels where it is known as lymph. The flow of lymph is unindirectional. Through lymph “vessels” lymph goes to big veins. Thus, lymph again enters the blood.
1. The lymph keeps the tissues wet.
2. The lymph helps in transport of various substances from blood to tissues and vice versa.
Excretory System of Frog
In frog, waste materials are removed in different ways e.g. through skin, lungs, liver digestive system etc. But for removal of nitrogenous wastes, there are two kidneys. Kidneys are attached to dorsal wall of body cavity. These are present close to vertebral column in posterior part of body cavity. These are elongated and made up of urinary tubules. Urinary tubules combine to form collecting ducts which open into Ureter. The urine from kidneys comes into ureters after illustration. Both ureters which start from edges of kidneys open into the cloaca. From here, urine is excreted directly or stored in the urinary bladder, which on opening of cloacal aperture is expelled. The carbon dioxide and water are excreted through lungs and skin while through liver and digestive system; undigested food and some wastes are excreted.
(Diagram)
Reproductive System of Male Frog
The reproductive system of male frog consists of a pair of testes and reproductive ducts. Each testis is attached to kidney by means of a membrane. At anterior end of testis, there is present fat body. Each testis is composed of small ducts called seminiferous tubules in which sperms are produced. Sperms enter the kidney via vesa efferentia. Sperms reach the cloaca through ureter. From here, these are dischaged in the water through cloacal aperture in this way, ureter in male frog does two jobs, one is removal of urine and other is removal of sexual material, so it is called urinogenital duct and the urinary system and genital system are collectively call urinogenital system.
Reproductive System of Female Frog
The reproductive system of female frog consists of a pair of ovaries and reproductive ducts. Ovaries are present close to the kidneys. At their anterior ends, there are present fat bodies. Each ovary contains many follicles in which eggs (ova) are produced. During breeding season, ovaries are enlarged. Ova are released into the body cavity through the coelomic fluid, these enter the oviduct. The anterior part of oviduct is funnel like called oviducal funnel and reach the uterus. The uterus opens into the cloaca. At last, ova are discharge in the water through cloacal aperture. In water, union of sperm with egg results in formation of zygote. From zygotes, offsprings are formed and in this way continuity of race is ensured.
Nervous System of Frog
It consists of three parts:
1. Central Nervous System
2. Peripheral Nervous System
3. Sympathetic Nervous System
Central Nervous System
It consists of brain and spinal cord.
(Diagram)
Brain
Brain is enclosed in protective layers and is located in cranium or brain case, which is major part of skull.
(Diagram)
Brain is divided into three parts:
(a) Fore Brain
(b) Mid Brain
(C) Hind Brain
(a) Fore Brain
This is anterior part of brain. This is associated with sense of smell. It controls the secretion of many hormones. It also receives messages from internal and external environment of the body.
(b) Mid Brain
This is central part of brain. This is associated with eyes and vision.
(c) Hind Brain
This is the posterior part of brain. It controls and coordinates body movements and maintains balance of the body. It also controls respiration, circulation, taste and digestion.
Spinal Cord
The posterior part of the brain is continuous with spinal cord. It runs through the vertebral column. The spinal cord controls the movements of trunk region.
Peripheral Nervous System
It consists of nerves. These nerves connect the central nervous system (CNS) with various parts of the body. Some nerves originate from brain. These are called cranial nerves other nerves originate from spinal cord. These are called spinal nerves. In frog, there are 10 pairs of cranial nerves and 9 or 10 pairs of spinal nerves.
Cranial
Basically, nerves are of three types:
Sensory Nerves
These take messages from sensory organs to CNS.
Motor Nerves
These take messages from CNS to glands and muscles.
Mixed Nerves
These do both above mentioned functions.
Cranial Nerves
In these nerves, first, second and eight pairs are sensory nerves which are associated with senses of smell, sight and hearing. Third, fourth and sixth pairs are motor nerves which carry message from brain to the eye. Nine and ten pairs are mixed nerves, which are supplied to jaw, face, tongue and heart.
Spinal Nerves
These are all mixed nerves. These control functions of different organs.
Ear of Frog
The organ of hearing in frog is “Ear” like other vertebrates.
Structure of Ear of Frog
The ear of frog consists of following three parts.
1. External Ear
2. Middle Ear
3. Internal Ear
1. External Ear
External ear consists of a bone. The vibration is produced in external ear when sound waves strike with it.
(Figure)
2. Middle Ear
Middle Ear consists of a tympanic membrane. On the inner side of the membrane is a cavity known as tympanic cavity. The cavity contains small rod like bones called ossicles. The middle ear is connected to internal ear by a tube which is called Eustachian tube; it transfers the vibrations towards the internal ear.
3. Internal Ear
The internal ear is a very delicate organ. It consist of three semi circular canals. These canals are filled with a fluid and sensory cells are located at special places in these canals.
Function of Ear of Frog
When sound waves strike the tympanic membrane, it is set into vibration, this is in turn vibrates the internal ear and thus sound waves stimulate the hearing receptors in the inner ear. The internal ear, in addition to hearing also keeps the balance of the body.
Eye of Frog
The frog has two eyes one on each side of the head. If we make vertical section of the eye, we find that the innermost layer of the ball is the sensory retina. The retina contains photoreceptor cells. Outside the retina is the choroid, which is richly supplied with blood capillaries supplying nutrients to the retina. The sclerotic is the hard, outer most layer of the eye. It provides shape to the eye ball. The anterior transparent part of the eye is called cornea. Behind the cornea is Iris. The Iris has a window called the pupil. Behind the pupil is the lens of the eye. The cornea, pupil and lens focus light on the retina. A watery fluid is present in between the cornea and lens. Similarly a jelly like fluid is present between the lens and retina, through which light passes before it strikes retina. Optic nerve takes the sensory messages from the eye to the brain.
(Diagram)
Health Problems Related to Nutrition
Under NutritionDuring 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.
Light and Dark Reactions
Light ReactionsWhen 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.
Lipids
LipidsLipids 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.
Meiosis
MeiosisIt is that type of cell division in which cytoplasm and nucleus divides twice and as a result of this, four daughter cells are formed and chromosome number is reduced to half. It means that one diploid (2n) parent cell divides to form four haploid (n) daughter cells.
Meiosis consists of two sub divisions:
1. Meiosis I
2. Meiosis II
1. Meiosis I
It has following stages:
Prophase I
1. It is lengthy than prophase of mitosis. It is very important phase. It is divided into five stages during which there is continuous condensation of chromosomes.
2. The important process of this phase is synapsis in which homologous chromosomes pair with each other length wise.
3. Each pair consists of four chromatids or two chromosomes.
4. After synapsis, the process of crossing over takes place. In this, homologous chromosomes exchange their chromatids parts at certain places.
5. At end of this phase, nuclear membrane breaks up. Nucleolus disappears and chromosomes scatter over the spindle.
6. Like mitosis, mitotic apparatus is also formed here.
(Diagram)
Metaphase I
1. The chromosomes arrange on scatter of the spindle.
2. Here, homologous bivalents arrange at equatorial plate of spindle.
3. Only one spindle fiber is attached to each chromosome.
Anaphase I
1. Homologous pairs of chromosomes are separated.
2. Spindle fibers contract.
3. Chromosomes begin to move towards the opposite poles.
4. This phase is different from metaphase of mitosis because half the number of chromosomes moves towards each pole and each chromosome still has two chromatids.
Telephase I
1. Half the number of chromosomes reach at opposite poles.
2. Chromosomes again increase their length.
3. Nucleolus reappears. Nuclear membrane is reformed and in this way two daughter nuclei are formed.
4. Now cytoplasm divides and two daughter cells are formed. Each cell is haploid (n).
2. Meiosis II
It is similar to mitosis. The haploid cells formed in meiosis I pass through phases of meiosis II and ultimately four haploid (n) daughter cells are formed. These cells afterwards change into spores (in plants or gametes (animals)
Significance of Meiosis
1. Meiosis takes place only in germ mother cells which form gametes or spores.
2. It maintains the chromosome number of a species constant generation after generation.
3. If gametes had the same number of chromosomes as in somatic cells, the number of chromosomes would have doubled after each generation in a species.
4. The number of chromosomes is constant for each species. During meiosis; gametes (both and) formed are haploid.
5. Gametes unite to form a diploid zygote.
6. During meiosis, pairing of chromosomes takes place which is called synapsis.
7. Exchange of genetic material occurs during meiosis. In this way variations are produced which are raw material for evolution
Mitosis
MitosisIt is that cell division in which the number of chromosomes in both daughter nuclei remains same as in parent nucleus.
(Diagram)
Events of Mitosis
Mitosis has the following phases:
1. Prophase
2. Metaphase
3. Anaphase
4. Telephase
5. Cytokinesis
Prophase
1. In this phase, coiling of chromosomes starts and their length decreases but diameter increases. It means that chromosomes become shorter and thicker, this process is called condensation.
2. Microtubules arrange to form a structure called spindle.
3. In animal cell, there are also present centrioles on both poles of spindle. From each centriole, small microtubules or fiber arise forming a star shaped aster.
4. Spindle fibers, centrioles and aster collectively form mitotic apparatus. In plants, this apparatus is made up of only spindle fibers as asters are absent in these cells.
5. Nuclear membrane is broken down. Nucleolus disappears and chromosomes scatter over the spindle fiber.
6. Each chromosome consists of two similar threads like structure called chromatids, these chromatids are united to each other by means of centromere.
Metaphase
1. The chromosomes arrange themselves on equator of the spindle to form an equatorial plate. In this condition, chromosomes become more visible.
2. The chromosomes are attached at their centromere to one spindle fiber from each pole.
Anaphase
1. First of all spindle fibers shrink and become short.
2. The centromere of each chromosome then divides and the two chromatids of each chromosome start separating. At this stage these are not called chromatids because these are no in united condition these are called chromosomes.
3. These chromosomes start moving slowly towards the opposite poles. In this way, one set of chromosomes moves towrds one pole while other towards the other pole.
Telophase
1. The chromosomes reach their poles.
2. The chromosomes uncoil and become less visible.
3. Nuclear membrane reforms and nucleolus appears too. Therefore two nuclei are formed. Each daughter nucleus has the same number of chromosomes as the parent cell.
Cytokinesis
The division of cytoplasm is called cytokinesis. It begins at the last stages of nuclear division. In plant cell, cytoplasm divides by formation of cell plate which is also called phragmoplast. It gradually extends outward and finally two daughter cells are separated.
In animals, cytoplasm divides by furrowing. During this, there occurs inward pinching of cell membrane resulting into two daughter cells. In mitosis, two daughter cells are formed from one parent cell which are identical to their parent cell.
Significance of Mitosis
1. Mitosis occurs in all types of somatic cells.
2. Daughter cells formed as a result of mitosis have same number of chromosomes as that of parent cell. In this way, all cells of body of an organism have same number of chromosomes.
3. Zygote divides by mitosis to form embryo and after hatching or birth, mitosis continues up to maturity of an individual.
4. Mitosis also results in growth and repairing of damaged or worn out tissues.
5. Healing of wounds is also due to mitosis.
Methods of Food Preservation
PasteurizationThis 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.
Mineral
Mineral SaltsMineral 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.
Multicellular Organism (Brassica Plant)
Multicellular OrganismThe organisms consisting of many cells are called multicellular organism. e.g. Brassica Plant, frog, man etc. diagram?
Brassica Plant (Mustard Plant)
1. This plant is sown in winter and at the end of season, it produces seeds and then dies.
2. This is an annual plant.
3. An oil is extracted from seeds of this plant which is known as mustard oil.
5. The scientific name of this plant is Brassica Campestris.
(Diagram)
Non-Reproductive Parts or Vegetative Parts
These parts do not directly take part in sexual reproduction e.g. root, stem, branches and leaves.
Reproductive Parts
These parts directly take part in sexual reproduction e.g. flower, fruit and seed.
Root of Brassica
The root is that part plant which is present inside the soil. It is produced from radical of seed. The first formed root is called Primary root. During its growth, it gives off secondary and tertiary root. Each root has a root cap at its tip or apex. Behind the root cap, root hairs are present which absorbs water and salts from the soil. Roots also anchor the plant firmly in the soil.
(Diagram)
Internal Structure of Root of Brassica
When transverse section of root of Brassica is observed under the microscope, the following parts are very prominent.
Epidermis
It is outermost and protective layer. It is single celled. Some cells grow outward to form root hair.
Cortex
It is present inner to epidermis. It is made up of several layers of thin walled living cells (parenchyma cells). There are present intercellular spaces. These cells store food.
Endodermis
it is the innermost layer of cortex. There are no intercellular spaces. There are thickenings of special materials around the cell which check diffusion of water from xylem to cortex.
Pericycle
The layer present inner to endodermis is called pericycle. There are also no intercellular spaces. All the branches of roots arise from pericycle.
Vascular Bundles
Xylem is present in middle of root which extends to pericycle in the form of four rays and controls one way transport of water and salts. In between the xylem rays, phloem bundles are present which transport food in two directions.
Stem of Brassica
The stem is that part of the plant which grows above ground. It arises from plumule of seed. It is herbaceous and branched. It bears leaves and flowers. The part of stem or its branch from where a leaf arises is called node. The part between two nodes is called internode. the important function of stem is the conduction of prepared food from leaves to other parts and that of water absorbed from roots to leaves. It supports leaves, flowers and fruits like a pillar. It keeps the leaves in such a position that they can get light to prepare food.
(Diagram)
Internal Structure of Stem of Brassica
When transverse section of stem of Brassica is observed under the microscope, following parts are visible.
Epidermis
It is the outermost protective layer of stem. Outer to epidermis, there is layer of cutin which reduces loss of water from stem. The cells are compactly arranged and there are no intercellular spaces.
Cortex
It is inner to epidermis. It is made up of many layers of parenchyma and collenchyma tissues. The main function of cortex is storage of water and food.
Endodermis
It is innermost layer of cortex. It is not prominent in stem. It allows suitable quantity of waer to enter cortex from xylem.
Pericycle
It is in the form of bundles in between the endodermis and vascular bundles. It is composed of sclerenchyma cells. It forms bundle cap.
Vascular Bundles
In stem, vascular bundles are arranged in the form of ring. Vascular bundle consists of phloem and xylem. Phloem is towards outside and xylem is towards inside. Few layers of cambium are present between the xylem and phloem. Cambium causes increase in diameter of the stem with passage of time.
Medullary Rays
There are present few layers of thin walled living cells between every two layers. These are called medullary rays. The medullary rays connect the cortex with pith for the transport of food.
Pith
The central part of stem consists of living, rounded, thin walled parenchyma cells. This part is called pith. Here food is stored.
Leaf of Brassica
1. Leaf is produced on node of stem or its branch.
2. Each leaf consists of two parts. The stalk of leaf is called petiole and upper broad part is called lamina.
3. Young leaves are without petiole and their margins are entire or smooth.
4. Lower leaves are large in size. These are also without petiole but there margins are wavy.
5. In the middle of leaf there is a thick midrib.
6. From midrib, arise veins of different thickness and form a network in leaf. This arrangement of veins is called reticulate venation.
7. Veins are composed of xylem and phloem.
8. The angle formed between stem and leaf is called axil. In this axil, buds are present which gwo and become branches.
9. The dorsal and ventral surfaces of leaves are different from each other. Such leaves are called bifacial leaves.
10. The main function of leaf is the preparation of food by process of photosynthesis.
Internal Structure of Leaf
When transverse section of leaf is observed under the microscope, following structure are visible.
(Diagram)
Epidermis
This layer of cells covers both upper and lower surfaces of leaf. Upper layer is called upper epidermis and lower layer is called lower epidermis. There are more number of stomata in lower epidermis than upper epidermis. This results in less transpiration and CO2 enters according to need. Each stomata consists of two guard cells, which are bean shaped, or kidney shaped. There is a pore between guard cells through which exchange of gases takes place and water vapours come out of leaves.
Mesophyll
The tissue present between upper and lower epidermis is called mesophyll. It consists of two parts.
Palisade Mesophyll
Uper part consists of elongated cells which hare lying vertical. These are double layered closely packed cells and are called Palisade Mesophyll.
Spongy Mesophyll
The lower part is sponge like and has more intercellular spaces. This is called spongy mesophyll.
Both types of cells have chloroplasts containing chlorophyll. So, photosynthesis takes place here. The function of mesophyll is to manufacture food for the plant.
Vascular Tissue
It consists of midrib and veins. The midrib is bundle. Upper part of midrib is xylem and lower part is phloem. Pericycle and endodermis surround this bundle. Besides this Lamina has other bundle which are called veins.
Flower of Brassica
The flower is reproductive part. With the maturation of age, the plant bears yellowish flowers. Many flowers are arranged on a branch in a special way. This branch is called peduncle. This arrangement of flowers on the peduncle is called Inflorescence.
Parts of Flowers
Flower consists of a stalk and floral leaves. The stalk is called Pedicel. The upper part of pedicel is comparatively swollen and flattened. This is called thalamus. On the thalamus, floral leaves are arranged in four whorls.
(Diagram)
The details of floral leaves is as follows:
Calyx
It is the outermost whorl of floral leaves. It consists of four sepals. On maturation, its colour changes to yellow. In young flowers sepals cover the inner parts of the flower. The main function of calyx is to protect inner parts of the flower.
Corolla
It is the second whorl of floral leaves. It consists of four free petals. Its yellow colour is conspicuous and can attract insects, honey bees and butterflies which help in pollination.
Androecium
It is the third whorl present inner to petals. It is the male reproductive part. It consists of six free stamens. These are arranged in two whorls, the outer whorl has two small stamens and inner whorl has four long stamens. Each stamen consists of two parts. Lower stalk is called filament. Upper swollen part is called anther, Inside anther, a large number of pollen grains are produced. When anther matures, a longitudinal slit appears in its walls from which pollen grains escape. AT the base of filament, four nectaries are present. These nectaries secrete nectar. To get nectar, insects visit the flowers. In this way, pollen grains get attached to the bodies of insects and are transferred from one flower to the other. This process is called pollination.
Gynoecium
It is the inner most part of flower. It is female reproductive part. It consists of two carpels, which are fused. Each carpel has three parts. The basal swollen part is called ovary. The stalk like part above the ovary is called Style. The top of style is somewhat swollen and it is called Stigma. Overy contains many ovules. Ovules are ripened to form seeds while ovary is ripened to form fruit. The fruit of Brassica is called Siliqua.
Need for Food
Need for FoodEverything 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
Nutrients of Food and Their ImportanceThe 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
Nutrition and Food Technology
Nutrition and Food TechnologyFor 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.
Nutrition in Man
Nutrition in ManLike all other animals human beings need food for following activities:
1. To get energy this may be used to carry out different activities in the body.
2. To build new protoplasm in the cells, renew and replaced damaged cells and tissues for grwoth and reproduction.
3. To maintain health and build resistance against various diseases.
Man’s diet consists of following components:
1. Carbohydrates
2. Proteins
3. Lipids
4. Vitamins
5. Mineral Salts
6. Water
Organelles in Cytoplasm
MitochondriaThey re oval or rod like in shape. Their membrane is doubled. Outer membrane is smooth while inner membrane has enfolding in the mitochondrial matrix. These enfolding are called cristae. The cristae bear small rounded bodies which are called particles.
There are about one million elementary particles in one mitochondrian. They are involved in oxidative phosphorylation. They also have many respiratory enzymes.
Number of Mitochondria
Their number is different in different cells of different animals. In more active cells, their number is more than 1000 e.g. liver cell.s The cells of ear lobes have a few number of mitochondria.
Function
Mitochondria re very important organelles of Eukaryotic cell.s Many oxidation-reduction reaction occur in the mitochondria. As a result energy is produced. This energy is used by cell in various functions. This the reason that mitochondria are also called “Power house of cell”.
Golgi Bodies
They were discovered by Camillo Golgi. They consist of set of smooth, flattened sacs which are called cristernae. The cristemae are stacked over each other. Golgi bodies are in the form of network in some cells or meshwork or filamentous in other cells.
Function
Golgi bodies store the secretions, convert them into finished products and pack them at their margins into small rounded sacs called Golgi vesicles, which transport secretions outside the cell.
Endoplasmic Reticulum
It is a network of tubules and cristemae extending throughout the cytoplasm from nuclear membrane to cell membrane.
Types of Endoplasmic Reticulum
Following are the two types of Endoplasmic Reticulum:
Smooth Endoplasmic Reticulum
It is also called non-granular endoplasmic reticulum because ribosomes are not attached on it.
Rough Endoplasmic Reticulum
It is also called granular endoplasmic reticulum because ribosomes are attached on it.
Functions
1. Smooth endoplasmic Reticulum plays a role in synthesis of lipids.
2. Rough endoplasmic reticulum plays an important role in synthesis of proteins. It also transports materials from one part of cell to other.
3. Endoplasmic reticulum provides support to the cell.
Ribosomes
These are tiny granular structures. These re not bounded by any membrane. These are formed in the nucleolus nd re freely dispersed in cytoplasm or attached with endoplasmic reticulum.
Functions
Ribosome is involved in protein synthesis. It is the only organelle which is also found in Prokaryotic cell.
Plastids
These are pigment containing organelles. These are found in plant cells. Many plastids have one or more than one pigments.
Types of Plastids
Plastids are of three types which are as follows:
Chloroplasts
These are mot important plastids. These re green in colour and found in green parts of plant. These contain chlorophyll which helps in photosynthesis. The study of ultra structure reveals that it is bounded by a double membrane.
Inside the chloroplast there is present a semifluid matrix called called stroma, which is made up of proteins and other chemicals. The inner membrane forms stacked membrane system which becomes suspended in the stroma. Each membrane stack is called granum (plural grana. The membranes of grana are the sites where photosynthesis occurs in the presence of sun light.
Functions
In chloroplasts, photosynthesis takes place and food is prepared for plant.
Chromoplasts
These are second type of plastids. These are of various colours other than green. In plants, colours other than green are due to chromoplasts. These are present in the petals of the flowers and in the ripened fruit.
Functions
These help the plants in pollination. These impart various colours to petals and fruits.
Leucoplasts
These are third type of plastids. These are colourless plastids. These are triangular tubular or of any other shape. These are found in food storage prts of the plant especially the roots and tubers.
Centriole
In animal cells, two centrioles are present near the nucleus. There are hollow and cylindrical. Each centriole consists of nine triplets of microtubules.
Function
Centrioles help in spindle formation during division of animal cell. Spindle is composed of protein fibers which help the chromosomes to move. Centrioles are absent in cells of higher plants. In some cells, centrioles help in the formation of flagella or cillia.
Vacuole
It is a fluid filled small sac which is bounded by a single membrane. In animal cells, these are comparatively smaller in size but many in number while in plant cells; there is a large central vacuole which is filled with water and salts.
Functions
In small organisms, extra water and wastes are excreted through contractile vacuoles, while food is digested in food vacuole. Increase in size of vacuole results in an increase in size of cell.
Photosynthesis
PhotosynthesisPhotosynthesis is a Latin word derived from two words photo (light) synthesis (building up). In this process, green plants manufacture carbohydrates from carbon dioxide and water. The energy needed for this process is obtained from sunlight, which is absorbed by chlorophyll and oxygen is produced as by-product. Leaves are the major sites of photosynthesis in most plants but all green parts of a plant including green stems; un-ripened fruit can carry out photosynthesis. Temperature also plays a very important role in photosynthesis. Temperature affects the rate of photosynthesis. This process occurs during day time only.
Conditions and Factors Necessary for Photosynthesis
Water
Plants need water for many functions of life. Water enters the root hair from the soil. It passes through various cells and reaches the xylem of the root. From here it moves to the stem and then the veins of the leaves. Finally, it reaches the mesophyll cells in the leaves. It provides hydrogen for the synthesis of glucose and helps in opening and closing of stomata. If leaves get less water, less stomata open, this reduces the rate of photosynthesis. Opening of more stomata provide more carbon dioxide for photosynthesis.
Carbon Dioxide
This is an important factor which affects photosynthesis. The amount of carbon dioxide in the atmosphere is about 0.03% and does not vary much. Its amount differs from place to place which may affect the rate of photosynthesis. e.g. the concentration of carbon dioxide close to the ground in a dense forest is higher than in an open field. Although carbon dioxide is needed in very little amount by the plants, yet photosynthesis cannot take place without it. It diffuses from the air into the intercellular spaces through stomata and enters the chloroplasts in the mesophyll cells. Carbon dioxide provides carbon to build up glucose molecule. If the amount of carbon dioxide in the atmosphere increases to 1% rate of photosynthesis also increases, and it starts decreasing if concentration of carbon dioxide is decreased. If the concentration of carbon dioxide decreases below 0.03% the rate of photosynthesis also declines.
Chlorophyll
It is the green substance. It is found in special organelles called chloroplasts, which are found in the green leaves and herbaceous stems. In leaves, it is present in the mesophyll cells. Chlorophyll changes light energy into chemical energy and makes food in plants. Plants lacking chlorophyll cannot carry out photosynthesis occurs only in those parts where chlorophyll is present.
Sunlight
Light is very important for the process of photosynthesis. Without light the photosynthesis cannot take place. It provides energy needed for the synthesis of glucose molecule. Light intensity varies from day to day and from place to place. Plants photosynthesize faster on a bright sunny day than on a cloudy day. While light consists of seven colours. The blue and red are best for photosynthesis.
Is Chlorophyll Necessary for Photosynthesis?
Experiment
Since it is not possible to remove chlorophyll from a leaf without killing it, so it becomes necessary to use a leaf where chlorophyll is present only in patches. Such a leaf is known as variegated leaf and a plant with such leaves is used in this experiment.
For destarching the leaves, the pot is kept in a dark place for a couple of days and then exposed to day light for a few hours. The leaf is then removed from plant. Its outline is carefully drawn to note the position of presence or absence of chlorophyll on it.
Now iodine is applied to the leaf to test for the presence of starch (starch when ever comes in contact with iodine turns blue).
This test shows that only those parts which were prevously green turned blue with iodine while the white parts turned brown. This result indicates that starch is formed only in those parts of the leaf where chlorophyll exists (i.e. green parts). In other words photosynthesis is not possible without chlorophyll. If this were possible the white parts of the laf should have also given a blue colour with iodine.
(Diagram)
Is Light Necessary for Photosynthesis
Experiment
A potted plant is destarched by keeping it in the dark room for two days. It is then transferred to light. Two of its leaves are selected for the examination. One leaf is wrapped completely in black paper. The other leaf is also wrapped in black paper but an L-shaped part of the paper is cut out so that light can reach this part of the leaf through it. The plant is placed in the sunlight for 4 to 6 hours. The two leaves are now detached from the plant and tested for presence of starch. It would be observed that the leaf which does not receive any light is free of starch (remains brown with iodine). However, in the second leaf, light could pass through the L-shaped opening in the black paper. Only this L-shaped area turns dark blue while the other parts of the leaf remain brown. This shows that light plays a vital role in the manufacture of starch since starch is manufactured due to photosynthesis, light is essential for this process.
(Diagram)
Is Carbon Dioxide Necessary for Photosynthesis
Experiment
Two potted plants are destarched by keeping them in a dark room they are watered properly during this period. Each pot is enclosed in a transparent polythene bag as show in figure. A petri dish containing soda lime (potassium hydroxide) is placed on one of the pots to absorb any carbon dioxide present in the polythene bag. In the other pot a petri dish is placed containing sodium bi-carbonate solution which would produce carbon dioxide. The plants are then left in light for several hours. A leaf from each pot is detached and tested for starch. The leaf from the pot containing soda lime does not turn blue. soda lime had absorbed any carbon dioxide present in the bag. The leaf from the other pot where carbon dioxide was being released by the sodium bicarbonates solution turns blue indicating the presence of starch. These results show that carbon dioxide is essential for photosynthesis
Proteins
ProteinsProteins 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.
Role of Water
WaterWater 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.
Structure of Eukaryotic Cell
Structure of CellThere are two types of cells:
1. Prokaryotic cell
2. Eukaryotic Cell
Prokaryotic cell lacks a membrane bound nucleus and membraned organelles e.g. bacterial cell while eukaryotic cell has a membrane bound nucleus and membraned organelles e.g. cells of plants and animals.
With the help of light microscope and electron microscope, a typical Eukaryotic cell shows the following structural details.
(Diagram)
1. Cell Wall
2. Cell Membrane
3. Nucleus
4. Cytoplasm
1. Cell Wall
It is the outer most boundary of plant cells. It is rigid and non-living. It is chemically composed of Cellulose. The cell wall of fungi is made up of Chitin. The walls of some cells are thick and walls of some cells are thin. For example, in plants, xylem vessel elements and tracheids (which transport water and minerals) have thick walls whereas as parenchyma cells (which store water and food) have thin walls. The primary layer of cell wall is known as primary walls which are further strengthened by an additional layer called secondary wall especially in xylem vessels. Secondary wall is thicker than the primary wall. Electron microscope studies reveal that cellulose fibers in primary and secondary walls have a criss cross arrangement.
Functions
Cell wall provides a definite shape, rigidity, protection and support to plant cell.
2. Cell Membrane
It is a thin membrane which is also called Plasma membrane. It is present in cells of all plants and animals. It is outer most boundary of animal cell while in plant cells; it is present inner to cell wall. Both nucleus and cytoplasm are surrounded by cell membrane. According to fluid mosaic model, cell membrane is composed of two layers of lipids in which protein molecules are partially or completely embedded.
Functions
Cell membrane is selectively permeable membrane. It means that it allows some things to pass through easily while some not. Thus, it controls the movement of material inside or outside the cell.
3. Nucleus
It is most important and distinct part of the cell. It is present in center of the animal cell while in plant cell it is pushed on one side due to large central vacuole. It is also surrounded by a membrane which is called membrane. Under microscope, it to be doubled and nuclear electron appears porous.
1. The number of chromosomes is fixed for each species. This number is called diploid number (2n). E.g human’s cell has 46 chromosomes, cell of Radish has 18 chromosomes, and cell of union has 16 chromosomes.
2. Chromosomes are composed of protein and DNA.
3. In the nucleolus (plural, Nucleoli) ribosomal RNA is formed which helps in the formation of ribosome.
4. Cytoplasm
It is viscous opaque substance. It is present between nuclear membrane and cell membrane. In a living cell, many types of organelle of different sizes and shapes are found. It contains many insoluble granules of storage substances. There are also present organic compounds like carbohydrates, proteins, lipids (fats), enzymes and inorganic compounds like water and salts.
Functions
Cytoplasm provides chemicals, site and environment for different biochemical reactions.
Difference between Prokaryotic Cell and Eukaryotic Cell
Prokaryotic Cell· The organisms made of prokaryotic cells are called prokaryotes e.g. bacteria and cyanobacteria.
· These cells lack a membrane bound nucleus. The hereditary material (DNA) is found in cytoplasm.
· These cells lack membrane bound organelles.
· Ribosomes are of small size in and freely scattered cytoplasm.
· Cellulose is absent in cell wall, rather it is made up of peptido-glycan or murein.
· These cells are simple and of smaller size (average diameter 0.5 – 10 nm)
Eukaryotic Cell
· The organisms mae of Eukaryotic cells are called Eukaryotes, e.g. animals, plants fungi and protists.
· These cells have a membrane bound nucleus; and hereditary material is found inside the nucleus.
· These cells have membrane bound organelles.
· Ribosomes are of large size and are present in endoplasmic reticulum free in cytoplasm.
· Cellulose is present in cell wall of plant cells. The cell wall of most of fungi is composed of chitin.
· These cells are complex and of larger size (Average diameter 10-100nm)
Teeth
TeethGod 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.
The Discovery of Cell and Cell Theory
Discovery of CellIn 1665, an English biologist Robert Hooke invented first compound microscope and observed the sections of corks and leaves under this microscope. He noticed in them small box like chambers of same size which he called “cells”. After this, biologists observed different organisms under the microscope. They found that structure of cells was complex.
Cell Theory
In 19th century, the compound microscope was highly advanced and biologists observed things just a micrometer apart. After this, a series of discoveries started, which provided basic information for cell theory.
1. In 1831 – 33, Robert Brown discovered nucleus in cells of plants.
2. In 1838, a German botanist Mathias Scheiden observed that all plants were made up of cells.
3. In 1839, Theoclor Schwann obsrved that the bodies of of animals were made up of cells which were similar to plant cells.
4. Thus, Schleiden and Schwann formulated the “Cell Theory”. According to this, all organisms are made up of cells.
5. In 1840, J. Purkinji gave the name “Protoplasm” to the things found inside the cells. At that time, cell was considered as a bag of thick dense substance containing a nucleus.
Later on, resolving power and quality of microscopes were highly improved. Section cutting of tissues and cells and their staining became easier and better. It revealed that cell was not a simple mass of granular substance; instead it contained many sub cellular bodies called “Organelles”. Each organelle has a definite job in the cell.
6. Human is made up of about 60 trillion cells. From Amoeba and unicellular algae to whales and tallest red wood trees, all’ are made up of similar basic units called cell.s All animals and plants are thus made up of cells and cell products.
Salient Features of Cell Theory
1. All animals and plants are made up of cells and cell products. Among these some organisms are unicellular and some are multicellular.
2. Cell is structural and functional unit of living organisms.
3. New cells come from the divisions of pre-existing cell.
Tissues
TissuesA group of cells which perform same function is known as tissue. The tissues are divided into different types on the basis of their form and structure or function.
Plant Tissues
Following are the types of tissues in plants:
1. Simple Tissues
2. Compound Tissues
1. Simple Tissues
Simple tissues consists of only one type of cells. In plants, they are of following types:
i. Meristematic or embryonic tissues
ii. Permanent Tissues
i. Meristematic Tissues
1. Cells of this tissue have ability to divide.
2. Cytoplasm is dense nd nucleus is big in these cells.
3. Vacuoles are smaller if present other wise absent.
4. All cells are identical.
5. There are no intercellular spaces.
6. Their walls are thin and nucleus is present in centre of cell.
7. These tissues found on apex of root or shoot are called apical meristems. The cells of these tissues divide; and redivide to add primary tissue for elongation of setm or root.
This type of growth is called primary growth.
8. Meristematic cells are also found on the lateral sides of roots and stems as lateral(cambium) or intercalary meristem, and these add, secondary tissues. In this way, thickness of stem or root is increased. This type of growth is called secondary growth.
ii. Permanent Tissues
The cells of this tissue lack the ability to divide and they originate from meristems. These are given below:
a. Epidermal Tissues
b. Ground Tissues
(a) Epidermal Tissues
1. They are found as the outermost covering of leaf, stem or root.
2. There are non intercellular spaces.
3. Cells are rectangular in shape.
4. In the epidermal tissues of stem and leaves, there are small openings called stomata for gaseous exchange.
(b) Ground Tissues
1. Most of the portion of body of herbaceous plants consists of ground tissues i.e. parenchyma.
2. They are thin walled.
3. Cells are large in size.
4. Cells sometimes may develop the ability to divide.
5. Their main functions are to prepare and store food and water.
Supporting or Mechanical Tissues
These provide strength flexibility to the plant. They are of following two types:
a. Collenchyma Tissues
b. Sclerenchyma Tissues
(a) Collenchyma Tissues
1. These consist of living cells.
2. Their walls are not uniformly thickened.
3. Usually walls are thickened at angles.
4. These are more flexible or elastic than sclerenchyma.
5. These tissues are found in stem, in midrib of leaves and in cortex of petiole.
(b) Sclerenchyma Tissues
1. These consist of dead cells.
2. Their walls are highly thickened due to deposition of lignin.
3. Lignin provides hardness and strength to the cell.
4. These cells are without protoplasm.
5. Sclerenchyma cells are of two types,
· Stone cells having uniformly thick cell walls; found in testa of seeds.
· Fibrous cells which are elongated cells found in xylem and phloem for strength and transport of water
2. Compound Tissues
These are the tissues which consists of two or more than two types of cells. But all cells perform a common function.
These Tissues are of following types:
Xylem Tissue
1. This vascular tissue transports water in the plants and provides strength to the plant.
2. In this tissue, there are present xylem parenchyma and two types of thick walled dead cells.
Long cells which are called vessel elements or cells. They are joined together to form long pipe-lines. These transport water from roots to leaves.
Spindle shaped cells, which are called tracheicts. These provide strength to root and shoot etc.
3. Xylem conducts water in one direction that is from roots towards the stem and leaves.
Phloem Tissues
1. This vascular tissue transports food in the plants.
2. It helps in two directional conduction of food material i.e. from leaves to roots and vice-versa.
3. This tissue mostly consists of living cells. There are three types of cells
(a) Phloem Parenchyma
(b) Sieve Tube Cells
(c) Companion Cells
(a) Phloem Parenchyma
These cells store surplus water and food. They can start to divide when needed.
(b) Sieve Tube Cells
Their end walls have small pores called sieve plates. These cells join to form long pipelines, which are called sieve tubes. There is no nucleus in these cells. Their main function is to transport food.
(c) Companion Cells
In some plants, each sieve tube cell is accompanied by a companion cell. The companion cell has a nucleus. The corn cell controls the movement of food through sieve tubes.
Animal Tissues
Following are four types of tissues that are found in animals:
1. Epithelial Tissues
2. Connective Tissues
3. Muscle Tissues
4. Nerve Tissues
1. Epithelial Tissues
1. these are found as outer most layers of an organ or as lining of body invaginations.
2. Their cells are long and flat.
3. These may form one or more layers of epithelial tissues of skin which is called squamous epithelial cells.
4. Squamous Epithelium provides protection to skin.
5. Some cells are cubical in shape and known as cuboidal epithelial cells.
6. Cuboidal epithelial cells from the lining of glandular ducts and help in the production of cell secretions.
7. Some cells are small and elongated which are found at certain places in the inner lining of different organs and secret juice. These are called columnar epithelial cells e.g. cells of gastric glands in stomach which secrete the gastric juice.
8. Some columnar cells have cilia at their free surface. These are called ciliated columnar epithelial cells e.g. cells present in trachea. Due to movement of these cilia, mucous and other materials are expelled.
2. Connective Tissues
1. This tissue is made up of semi fluid matrix.
2. These matrixes contain a variety of cells and fibers.
3. These tissues provide support to different body parts and bind them together. These also protect the organs from germs and help in the production of blood cells.
4. These are of two types:
Soft connective tissues e.g. fatty tissues and tendons.
Hard connective tissues e.g. cartilage and bone.
5. Blood is also a special connective tissue with cells suspended in the fluid medium. It transports materials in the body.
2. Muscular Tissues
1. This tissue is made up of special contractile cells or fibers.
2. The cells are elongated and are called muscle fibers.
3. These cells have the ability to contract and relax which results in movements of body and the organs.
4. Following are the three types of muscles in our body.
Skeletal Muscles
These are attached to cartilage and bones. These seem to be striped fibers under the microscope. Therefore these are striped or striated muscles. Their movements are under our control so these are voluntary muscles e.g. muscles of arm and legs which move these parts.
Smooth Muscles
These are found around hollow organs such as blood vessels, gut. These produce slow, sustained contractions but do not fatigue. These re composed of spindle shaped unstriated muscles. These are involuntary and are under the control of the autonomic nervous system.
Cardiac Muscles
These are found in the heart. These are composed of branched fibers and are capable of sustained contraction but do not not fatigue. These are also involuntary in action.
4. Nervous Tissues
1. These are composed of nerve cells which are called neurons.
2. Each neuron consists of a cell body, axon and dendrites.
3. These productive nerve impulse to conduct messages.
4. By this tissue, different body parts have coordination with each other.
5. This tissue also forms brain and spinal cord.
Unicellular Organism (Amoeba)
The organisms consisting of only one cell are called unicellular organisms e.g. Amoeba, Paramecium etc.Amoeba
1. It is mostly found in fresh water pond or pool.
2. In the ponds, it is found moving about around the weeds and stones. Some species are found in the moist soil.
3. Amoeba is a large protist.
4. It does not have the permanent shape.
5. Its size is about the end of pin or it measures about 0.25mm. Therefore it is observed under the microscope.
6. Its structure is very simple.
7. It consists of nucleus and cytoplasm, which are surrounded by a cell membrane.
8. Cell membrane protects it.
9. Cytoplasm is divided into two parts. Outer clear and transparent part is called ectoplasm while the inner, viscous, translucent and granular part is called endplasm.
10. Endoplasm contains food vacuoles of different sizes. These food vacuoles help in the digestion of food.
11. The food of Amoeba consists of microbes present in the water of pond.
12. Contractile vacuole maintains the concentration of water in the body. It removes surplus water out of the cell.
13. In Amoeba, the exchange of gases and removal of waste.
14. In Amoeba, there are also present mitochondria, golgi bodies and ribosomes.
15. Nucleus changes its place with the movement of the organism.
(Diagram)
Vitamins
VitaminsVitamins 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
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