Online Notes Pathogen – NCERT Solutions for Biology Class 12
In biology, a pathogen (Greekpathos means “suffering, pain ” and genēs means “producer of”) in the oldest and broadest sense, a pathogen is anything that can produce disease; the term came into use in the 1880s. Typically the term is used to describe an infectious agent such as a virus, bacterium, protozoa, prion, a fungus, or another microorganism. We define a pathogen as a biological agent that causes disease or illness to its host (an organism which is attacked by the pathogen). Most often the pathogens disrupt the normal physiology of a multi-cellular animal or plant. However, pathogens can infect unicellular organisms from all of the biological kingdoms. There are several substrates and pathways whereby pathogens can invade a host. The human body contains many natural defenses against some of the common pathogens in the form of the human immune system and by some “helpful” bacteria present in the human body's normal flora. Some pathogens have been found to be responsible for massive amounts of casualties and have had numerous effects on afflicted groups. Today, while many medical advances have been made to safeguard against infection by pathogens, through the use of vaccination, antibiotics, and fungicide, pathogens continue to threaten human life. Social advances such as food safety, hygiene, and water treatment have reduced the threat from some pathogens. Watch animated lecture with detailed explanation of Biology Class 12 Pathogens have evolved specific mechanisms for interacting with their hosts The human body is a complex and thriving ecosystem. It contains about 1013 human cells and also about 1014 bacterial, fungal, and protozoan cells, which represent thousands of microbial species. These microbes, called the normal flora, are usually are found in certain areas of the body, including the skin, mouth, large intestine, and vagina. In addition, humans are always infected with viruses, most of which rarely, if ever, become symptomatic. If it is normal for us to live in such close intimacy with a wide variety of microbes, how is it that some of them are capable of causing us illness or death? Pathogens are usually distinct from the normal flora. Our normal microbial inhabitants only cause trouble if our immune systems are weakened. The pathogens have developed highly specialized mechanisms for crossing cellular and biochemical barriers and for eliciting specific responses from the host organism that contribute to the survival and multiplication of the pathogen. In order to survive and multiply in a host, a successful pathogen must be able to: (1) Colonize the host (2) Find a nutritionally compatible niche in the host body. (3) Avoid, subvert, or circumvent the host innate and adaptive immune responses. (4) Replicate, using host resources and (5) Exit and spread to a new host. Pathogens have evolved mechanisms that maximally exploit the biological machinery of their host organisms. They totally depend on their host for their survival. For the NCERT solutions of Pathogens, click on CBSE NCERT solutions for Biology Class 12. Pathogens and Diseases Although we can easily understand why infectious microorganisms would evolve to reproduce in a host, it is less clear why they would evolve to cause disease. One explanation is that, in some cases, the pathological responses elicited by microorganisms enhance the efficiency of their spread or propagation and hence clearly have a selective advantage for the pathogen. The virus-containing lesions on the genitalia caused by herpes simplex infection, for example, facilitate the direct spread of the virus from an infected host to an uninfected partner during sexual contact. Similarly, diarrheal infections are efficiently spread from patient to caretaker. In many cases, however, the induction of disease has no apparent advantage for the pathogen. Many of the symptoms and signs that we associate with infectious disease are direct manifestations of the host's immune responses in action. Some hallmarks/ symptoms of bacterial infection, are swelling and redness at the site of infection and the production of pus (mainly dead white blood cells), are the direct result of immune system cells attempting to destroy the invading microorganisms. Fever, too, is a defensive response, as the increase in body temperature can inhibit the growth of some microorganisms. Thus, understanding the biology of an infectious disease requires an understanding of both pathogen and host. For Class 12th online classes, NCERT solutions, CBSE guide, sample papers, latest updates from CBSE Board, enroll in Takshila Learning. Call us : 8800999280/8800999284
In this article, we discuss the topic 'Mass Percentage Composition of an element in a given compound'. This covers 11th science, the Unit 1 of Chemistry of Class 11 MASS PERCENTAGE COMPOSITION The mass percentage is one way of representing the concentration of an element in a compound or a component in a mixture. It is used to describe the percent by mass of each element in a compound. The mass percentage is calculated as the mass of a component divided by the total mass of the mixture, multiplied by 100. It is also known as mass percent(w/w) %. Importance of mass percentage For many purposes, it is important to know how much of an element is present in a given amount of a compound. It helps the chemists to derive an empirical formula ( It shows the lowest whole number of moles, and thus the relative number of atoms of each element in a compound)of the given compound, and the empirical formula can help in finding out the actual molecular formula(it shows the actual number of atoms of each element in a molecule). Determining the Mass Percent from a chemical formula Example: To calculate mass percentage of each element in glucose (C6H12O6) Solution: We know the relative amounts (mol) of the elements from the formula, 6Carbon atoms, 12 Hydrogen atoms and 6 Oxygen atoms. Now we multiply the amount of each atom in glucose by its molar mass to find the mass of each element of glucose. Divide each mass by mass of 1 moles of glucose gives the mass fraction of each element, and then multiplying by 100 gives a mass percentage of the elements. From the chemical formula, we know that there are 6 moles of carbon in 1 mole of glucose. 1 mole of carbon has a mass of 12.01g/mol of carbon (from periodic table) So 6 moles of carbon will have 12.01g/mol x 6 = 72.06g of Carbon. Similarly, 1mole of Hydrogen has a mass of 1.008g/mol of Hydrogen (from periodic table) So, 12 moles of Hydrogen will have the mass of 12 x 1.008 = 12.096g of Hydrogen. In the same way, for Oxygen, 1 mole of oxygen has a mass of 16.00g/mol(from periodic table) So, 6 moles of oxygen will have 16.00 x 6 = 96 g of Oxygen. Thus, 1 mole of Glucose (C6H12O6) has a mass of 72.06 +12.096 + 96 =180.16 g/mol To find out the mass % of the three elements of glucose, we first calculate the mass fraction of each element in 1 mole of glucose. Mass fraction is the mass contributed by each element in the total mass of glucose. Mass fraction multiplied by 100 gives a mass percentage of each element. Mass fraction of Carbon= 72.06g/180.16g =0.4000 Mass % of Carbon= 0.4000×100= 40.00% Mass fraction of Hydrogen = 12.096/180.16 =0.06714 Mass% of Hydrogen= 0.06714 x 100=6.714% Mass fraction of Oxygen =96/180.16 =0.53286 Mass% of Oxygen = 0.53286 x 100 = 53.286% Though there is an equal number of moles of Carbon and Oxygen, in the compound, the mass % of Oxygen is greater than that of Carbon because the molar mass of Oxygen is greater than that of Carbon. The mass % of Hydrogen is small because the molar mass of H is small. But we see that the sum of mass % of all the elements in a compound is 100%. In the given example, 40.00% + 6.714% + 53.286% = 100.00% Determining the Mass of an Element from its Mass Percent The above example shows that an element always constitutes the same fraction of the mass of a given compound.The mass fraction of an element in a given compound thus obtained remains constant and can be used to find out the mass of the element in any mass of that compound. Example: To find out the mass of Carbon in 16.55 grams of Glucose (C6H12O6) Solution: We know that 1 mole of glucose has a mass of 180.16 grams In 1 mole of glucose, there are 6 atoms of Carbon, which contributes the mass fraction of 72.06/180.16 = 0.4000 Thus the mass percent is equal to 0.4000 x 100 =40% This means in 1 mole or 180.16 grams of glucose, 40% is Carbon element and it remains same, whatever may be the quantity of glucose. Therefore the mass of Carbon in 16.55 grams of Glucose will also be 40% Mass of carbon in grams= (72.06/180.16) x 16.55 =6.62 grams In other words, 40% of 16.55 is 6.62 grams. Thus we now know how to calculate the Mass Percentage of an element in a given compound (knowing the chemical formula of the given compound), and vice versa i.e. to find out the chemical formula (Empirical / Molecular Formula) of a compound by knowing the masses of the element in a compound. Takshila Learning is known for providing quality education at low cost. Join online classes for excelling board exams and other entrance exams. Keeping in view the latest pattern of question paper of the CBSE board exams, we have developed the study material of all the subjects of Class 10, 11, and 12 and also the CBSE sample papers accordingly by our best faculty members. We provide notes, sample papers, different blogs, and articles on important topics, from different subjects.You can watch our videos anywhere at any time taught by our best-experienced faculty.
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Class 10 Science : Takshila Learning always designs subject matter in a way that it is easy to the Class 10 students to understand the concepts and learn how to attempt questions in CBSE Class 10 Science exams. In the previous article of CBSE Class 10th Science, we have discussed 'the construction and working of the eye'. Now, we will learn 'the defects of vision and their correction'. Defects of vision and their correction The ability to see is called vision.It is also called an eyesight.Vision is known as 'Drishti' in Hindi. There are three common defects of vision or defects of the eyes: MyopiaHypermetropiaPresbyopiaMyopia (Short-sightedness or nearsightedness) Myopia is the defect of vision due to which a person cannot see the distant objects clearly, though he/she can see the nearby objects clearly. The far point of an eye suffering from myopia is less than infinity.
The defect of the eye called myopia is caused:- Due to thehigh converging power of eye lens because of its short focal length.Due to the eyeball being too long.In some cases, in an eye suffering from myopia, the ciliary muscle attached to the eye lens does not relax sufficiently to make the eye-lens thinner to reduce its converging power. So due to the greater converging power of the eye-lens in amyopic eye, the image of a distant object is formed in front of the retina and hence the eye cannot see it clearly. Myopia is corrected using spectacles containing concave lenses. The concave lens used for correcting myopia should be of such a focal length that it produces a virtual image of the distant object at the far point of the myopic eye. The whole purpose of using a concave lens here is to reduce the converging power of the eye-lens. Calculation of Power of concave lens to correct myopia The focal length of concave lens needed to correct myopia in a person is calculated by using the lens formula:- 1/v-1/u=1/f Hypermetropia Hypermetropia is the defect of vision due to which a person cannot see the nearby objects clearly,buthe can see the distant objects clearly. The near point of a Hypermetropia eye is more than 25centimeter away. Hypermetropia is just the opposite of myopia. The defects of the eye are caused:- Due to low converging power of eye-lens because of its large focal lengthDue to the eyeball being too short.
In some cases, the ciliary muscle attached to the eye lens becomes weak and cannot make the eye-lens thicker to increase the converging power so due to thelow converging power ofthe eye-lens in an eye suffering from hypermetropia the image of nearby objects is formed behind the retina and hence the eye cannot see it clearly. Hypermetropia is corrected by using spectacles containing convex lenses. The convex lens used for correcting Hypermetropia should be of such a focal length that it forms a virtual image of the object at the near point N' of the Hypermetropia eye. Calculation of Power of concave lens to correct Hypermetropia The focal length of convex lens needed to correct Hypermetropiaa in a person is calculated by using the lens formula 1/v-1/u=1/f Presbyopia
Presbyopia is the defect of vision due to which an older person cannot see the nearby objects clearly due to loss of power of accommodation of the eye. The nearest point of the old person having presbyopia gradually recedes and becomes much more than 25 cms away. It is corrected in the same way as Hypermetropia by using spectacles having convex lenses. A person suffering from myopia as well as hypermetropia uses spectacles having bifocal lenses in which upper part consists of a concave lens used for distant vision and the lower part consists of a convex lens used for reading purposes. Cataract The medical condition in which the lens of the eye of a person becomes progressively cloudy resulting in blurred vision is called cataract. Cataract develops when the eye-lens of a person becomes cloudy due to the formation of a membrane over it.
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When a solution of acid and base is mixed, both of them neutralize each other and a third substance is formed called salt and this phenomenon is known as neutralization or neutralization reaction. The solution formed due to the mixing of a solution of acid and base is neither acidic nor basic in nature. Such solution is called neutral solution. Salt formed due to neutralization reaction may be acidic or basic in nature. Acidic or Basic nature of the salt depends on the potency of acid and base. Heat is evolved in the neutralization reaction. Reactions in which heat is evolved are called as exothermic reactions. Thus, neutralization reaction is an exothermic reaction. Example: Hydrochloric acid is an acid and Sodium hydroxide is a base. When a solution of sodium hydroxide is mixed with the hydrochloric acid solution, both neutralize each other and Sodium chloride (common salt) is formed. The reaction mixture becomes hot, as it is an exothermic reaction. The reaction involved in this can be represented as follows: Sodium hydroxide solution + Hydrochloric acid solution ——> Sodium Chloride Solution + Water Liquid Sodium chloride is the chemical name of common salt which is used in general.
Watch and understand the same topic with Class 7 Science. Neutralization Reaction in Everyday Life: Uses of neutralization reaction in everyday life: Indigestion : Hydrochloric acid released in our stomach that helps in the digestion of food and to kill bacteria, if any, present in food. Sometimes our stomach release more hydrochloric acid than required. Production of more hydrochloric acid in the stomach reveals as indigestion. This situation can be painful and causes pain in the stomach. To get rid of such symptoms, a medicine made of the milk of magnesia (a base) is taken orally. Milk of magnesia, being a base neutralizes the hydrochloric acid and gives relief from pain because of indigestion. Ant sting : Bee sting or Ant sting contains methanoic acid. Methanoic acid is also called formic acid. Ant or bee inject formic acid into our skin while biting. Due to injection of acid by ant or bee causes pain at the place of bite. Rubbing baking soda over the place of bite gives relief from pain. Baking soda, which is a base, neutralizes the effect of formic acid injected by bee or ant. Another base, such as zinc carbonate (Calamite solution) is also used in the case of bee or ant sting. Soil Treatment : Due to excessive use of fertilizers or wrong method of harvesting, the soil becomes acidic or basic. Acidic or basic nature of soil affects the yield as plants do not grow properly on such soil. Acidic soil is neutralized with slaked lime or quick-lime. Slaked lime (Calcium hydroxide) and quicklime (Calcium oxide) are used as bases. The basic soil is neutralized with organic matter. Organic matter release acid and neutralizes the basic nature of the soil. Factory Waste : Generally, wastes of the factories are acidic. If acidic wastes are flushed into rivers, acid present in them pollutes the water and kills the aquatic organisms. Thus, factory wastes are treated with basic substances to treat the acid present in them before being flushed in the river.
What is Google AdWords and what are its Advantages?
Most of us create a website to sell our products or services. Even after doing SEO(Search Engine Optimisation), we don't get that traffic for what we are looking for. SEO takes time but sometimes we don't have that much time to wait. We look for the best and the easiest solution for traffic. PPC is the best solution for instant traffic. Its conversion rate is also very high. PPC is a part of Search engine marketing(SEM). PPC: Pay per click is a part of digital marketing. In PPC advertisers pay a fee each time one of their ads is clicked. PPC services are being provided by asearch engine like Google, Bing. It is the easiest way to come to search engine results page (SERP) and get their top position when someone searchesfor specific keywords. Google provides PPC solution with name Google AdWords. Let's understand how AdWords works. When a user searches a query on Google search engine. That query is called Keywords.If you have chosen thesame keyword, your ad appears on next to or on top of organic search.When people click on that Advertisement. They will reach your site to buy or to know more about it. Watch recorded lectures on PPC by clicking free online digital marketing course
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