Here are simple, step-by-step explanations provided as NCERT Solutions for Class 12 Science Biology Chapter 16 Environmental Issues. These solutions are highly favored by Class 12 Science students for Biology Environmental Issues. They are incredibly useful for swiftly completing homework assignments and preparing for exams. All questions and answers from NCERT Book of Class 12 Science Biology Chapter 16 are readily available here at no cost to you. Page No 286: Question 1: What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river. ANSWER: Domestic sewage is the waste originating from the kitchen, toilet, laundry, and other sources. It contains impurities such as suspended solid (sand, salt, clay), colloidal material (fecal matter, bacteria, plastic and cloth fiber), dissolved materials (nitrate, phosphate, calcium, sodium, ammonia), and disease-causing microbes. When organic wastes from the sewage enter the water bodies, it serves as a food source for micro-organisms such as algae and bacteria. As a result, the population of these micro-organisms in the water body increases. Here, they utilize most of the dissolved oxygen for their metabolism. This results in an increase in the levels of Biological oxygen demand (BOD) in river water and results in the death of aquatic organisms. Also, the nutrients in the water lead to the growth of planktonic algal, causing algal bloom. This causes deterioration of water quality and fish mortality. Page No 286: Question 2: List all the wastes that you generate, at home, school or during your Trips to other places, could you very easily reduce? Which would be Difficult or rather impossible to reduce? ANSWER: Wastes generated at home include plastic bags, paper napkin, toiletries, kitchen wastes (such as peelings of vegetables and fruits, tea leaves), domestic sewage, glass, etc. Wastes generated at schools include waste paper, plastics, vegetable and fruit peels, food wrappings, sewage etc. Wastes generated at trips or picnics include plastic, paper, vegetable and fruit peels, disposable cups, plates, spoons etc. Yes, wastes can be easily reduced by the judicious use of the above materials. Wastage of paper can be minimized by writing on both sides of the paper and by using recycled paper. Plastic and glass waste can also be reduced by recycling and re-using. Also, substituting plastics bags with biodegradable jute bags can reduce wastes generated at home, school, or during trips. Domestic sewage can be reduced by optimizing the use of water while bathing, cooking, and other household activities. Non- biodegradable wastes such as plastic, metal, broken glass, etc are difficult to decompose because micro-organisms do not have the ability to decompose them. Page No 286: Question 3: Discuss the causes and effects of global warming. What measures need to be taken to control global warming? ANSWER: Global warming is defined as an increase in the average temperature of the Earth’s surface. Causes of global warming: Global warming occurs as a result of the increased concentration of greenhouse gases in the atmosphere. Greenhouse gases include carbon dioxide, methane, and water vapour. These gases trap solar radiations released back by the Earth. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an excessive increase in the Earth’s temperature, leading to global warming. Global warming is a result of industrialization, burning of fossil fuels, and deforestation. Effects of global warming: Global warming is defined as an increase in the average temperature of the Earth’s surface. It has been observed that in the past three decades, the average temperature of the Earth has increased by 0.6ºC. As a result, the natural water cycle has been disturbed resulting in changes in the pattern of rainfall. It also changes the amount of rain water. Also, it results in the melting of Polar ice caps and mountain glaciers, which has caused a rise in the sea level, leading to the inundation of coastal regions. Control measures for preventing global warming: (i) Reducing the use of fossil fuels (ii) Use of bio-fuels (iii) Improving energy efficiency (iv) Use of renewable source of energy such as CNG etc. (v) Reforestation. (vii) Recycling of materials Page No 286: Question 4: Match the items given in column A and B: Column A Column B (a) Catalytic converter (i) Particulate matter (b) Electrostatic precipitator (ii) Carbon monoxide and nitrogen oxides (c) Earmuffs (iii) High noise level (d) Landfills (iv) Solid wastes ANSWER: Column A Column B (a) Catalytic converter (ii) Carbon monoxide and nitrogen oxides (b) Electrostatic precipitator (i) Particulate matter (c) Earmuffs (iii) High noise level (d) Landfills (iv) Solid wastes Page No 286: Question 5: Write critical notes on the following: (a) Eutrophication (b) Biological magnification (c) Groundwater depletion and ways for its replenishment ANSWER: (a) Eutrophication:- It is the natural ageing process of a lake caused due to nutrient enrichment. It is brought down by the runoff of nutrients such as animal wastes, fertilizers, and sewage from land which leads to an increased fertility of the lake. As a result, it causes a tremendous increase in the primary productivity of the ecosystem. This leads to an increased growth of algae, resulting into algal blooms. Later, the decomposition of these algae depletes the supply of oxygen, leading to the death of other aquatic animal life. (b) Biological magnification: – To protect the crops from the several diseases and pests, a large number of pesticides are used. These pesticides reach the soil and are absorbed by plants with water and minerals from the soil. Due to rain, these chemicals can also enter water sources and into the body of aquatic plants and animals. As a result, chemicals enter the food chain. Since these chemicals cannot be decomposed, they keep on accumulating at each trophic level. The maximum concentration is accumulated at the top carnivore’s level. This increase in the concentration of pollutants or harmful chemicals with an increase in the trophic level is called biological magnification. For example, high DDT concentrations were found in a pond. The producers (phytoplankton) were found to have 0.04 ppm concentration of DDT. Since many types …

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Here are simplified, step-by-step explanations of NCERT Solutions for Class 12 Science Biology Chapter 15: Biodiversity And Conservation. These solutions are highly favored among Biology students in Class 12 Science for their convenience in completing homework and exam preparation. All questions and answers from Chapter 15 of the NCERT Book for Class 12 Science Biology are available here at no cost. Page No 268: Question 1: Name the three important components of biodiversity. ANSWER: Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Three important components of biodiversity are: (a) Genetic diversity (b) Species diversity (c) Ecosystem diversity Page No 268: Question 2: How do ecologists estimate the total number of species present in the world? ANSWER: The diversity of living organisms present on the Earth is very vast. According to an estimate by researchers, it is about seven millions. The total number of species present in the world is calculated by ecologists by statistical comparison between a species richness of a well studied group of insects of temperate and tropical regions. Then, these ratios are extrapolated with other groups of plants and animals to calculate the total species richness present on the Earth. Page No 269: Question 3: Give three hypotheses for explaining why tropics show greatest levels of species richness. ANSWER: There are three different hypotheses proposed by scientists for explaining species richness in the tropics. (1) Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity. (2) Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness. (3) Temperate regions were subjected to glaciations during the ice age, while tropical regions remained undisturbed which led to an increase in the species diversity in this region. Page No 269: Question 4: What is the significance of the slope of regression in a species − area relationship? ANSWER: The slope of regression (z) has a great significance in order to find a species-area relationship. It has been found that in smaller areas (where the species-area relationship is analyzed), the value of slopes of regression is similar regardless of the taxonomic group or the region. However, when a similar analysis is done in larger areas, then the slope of regression is much steeper. Page No 269: Question 5: What are the major causes of species losses in a geographical region? ANSWER: Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Biodiversity around the world is declining at a very fast pace. The following are the major causes for the loss of biodiversity around the world. (i) Habitat loss and fragmentation: Habitats of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization. This results in the breaking up of the habitat into small pieces, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species. (ii) Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered or extinct (such as the tiger and the passenger pigeon). (iii) Alien species Invasions: Accidental or intentional introduction of non-native species into a habitat has also led to the declination or extinction of indigenous species. For example, the Nile perch introduced in Lake Victoria in Kenya led to the extinction of more than two hundred species of native fish in the lake. (iv) Co­−extinction: In a native habitat, one species is connected to the other in an intricate network. The extinction of one species causes the extinction of other species, which is associated with it in an obligatory way. For example, the extinction of the host will cause the extinction of its parasites. Page No 269: Question 6: How is biodiversity important for ecosystem functioning? ANSWER: An ecosystem with high species diversity is much more stable than an ecosystem with low species diversity. Also, high biodiversity makes the ecosystem more stable in productivity and more resistant towards disturbances such as alien species invasions and floods. If an ecosystem is rich in biodiversity, then the ecological balance would not get affected. As we all know, various trophic levels are connected through food chains. If any one organism or all organisms of any one trophic level is killed, then it will disrupt the entire food chain. For example, in a food chain, if all plants are killed, then all deer’s will die due to the lack of food. If all deer’s are dead, soon the tigers will also die. Therefore, it can be concluded that if an ecosystem is rich in species, then there will be other food alternatives at each trophic level which would not allow any organism to die due to the absence of their food resource. Hence, biodiversity plays an important role in maintaining the health and ecological balance of an ecosystem. Page No 269: Question 7: What are sacred groves? What is their role in conservation? ANSWER: Sacred groves are tracts of forest which are regenerated around places of worship. Sacred groves are found in Rajasthan, Western Ghats of Karnataka,and Maharashtra, Meghalaya, and Madhya Pradesh. Sacred groves help in the protection of many rare, threatened, and endemic species of plants and animals found in an area. The process of deforestation is strictly prohibited in this region by tribals. Hence, the sacred grove biodiversity is a rich area. Page No 269: Question 8: Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem? ANSWER: The biotic components of an ecosystem include the living organisms such as plants and animals. Plants play a very important role in controlling floods and soil erosion. The roots of plants hold the soil particles together, thereby preventing the top layer of the soil to …

NCERT Solutions for Class 12 Biology Chapter 15 – Biodiversity And Conservation Read More »

Here are simplified, step-by-step explanations for NCERT Solutions for Class 12 Science Biology Chapter 14 on Ecosystem. These solutions are highly favored by Class 12 Science students studying Biology, as they assist in swiftly completing homework assignments and preparing for exams. All questions and answers from the NCERT Book of Class 12 Science Biology Chapter 14 are presented here at no cost, making them easily accessible to you. Page No 256: Question 1: Fill in the blanks. (a) Plants are called as_________ because they fix carbon dioxide. (b) In an ecosystem dominated by trees, the pyramid (of numbers) is _________ type. (c) In aquatic ecosystems, the limiting factor for the productivity is _________. (d) Common detritivores in our ecosystem are_________. (e) The major reservoir of carbon on earth is_________. ANSWER: (a) Plants are called as   autotrophs   becausethey fix carbon dioxide. (b) In an ecosystem dominated by trees, the pyramid(of numbers) is of inverted type. (c) In aquatic ecosystems, the limiting factor forproductivity is light . (d) Common detritivores in our ecosystem are earthworms. (e) A major reservoir of carbon on Earth is Oceans. Page No 257: Question 2: Which one of the following has the largest population in a food chain? (a) Producers (b) Primary consumers (c) Secondary consumers (d) Decomposers ANSWER: (d) Decomposers Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals. Page No 257: Question 3: The second trophic level in a lake is- (a) Phytoplankton (b) Zooplankton (c) Benthos (d) Fishes ANSWER: (b) Zooplankton Zooplankton are primary consumers in aquatic food chains that feed upon phytoplankton. Therefore, they are present at the second trophic level in a lake. Page No 257: Question 4: Secondary producers are (a) Herbivores (b) Producers (c) Carnivores (d) None of the above ANSWER: (d) None of the above Plants are the only producers. Thus, they are called primary producers. There are no other producers in a food chain. Page No 257: Question 5: What is the percentage of photosynthetically active radiation (PAR), in the incident solar radiation. (a) 100% (b) 50 % (c) 1-5% (d) 2-10% ANSWER: (b) 50% Out of total incident solar radiation, about fifty percent of it forms photosynthetically active radiation or PAR. Page No 257: Question 6: Distinguish between (a) Grazing food chain and detritus food chain (b) Production and decomposition (c) Upright and inverted pyramid (d) Food chain and Food web (e) Litter and detritus (f) Primary and secondary productivity ANSWER: (a) Grazing food chain and detritus food chain   Grazing food chain   Detritus food chain 1. In this food chain, energy is derived from the Sun. 1. In this food chain, energy comes from organic matter (or detritus) generated in trophic levels of the grazing food chain. 2. It begins with producers, present at the first trophic level. The plant biomass is then eaten by herbivores, which in turn are consumed by a variety of carnivores. 2. It begins with detritus such as dead bodies of animals or fallen leaves, which are then eaten by decomposers or detritivores. These detritivores are in turn consumed by their predators. 3. This food chain is usually large. 3. It is usually smaller as compared to the grazing food chain. (b) Production and decomposition   Production   Decomposition 1. It is the process of producing organic matter (food) by producers. 2. It is the process of breaking down of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw material such as CO2, H2O, and other nutrients. 2. It depends on the photosynthetic capacity of the producers. 2. It occurs with the help of decomposers. 3 Sunlight is required by plants for primary production. 3. Sunlight is not required for decomposition by decomposers (c) Upright and inverted pyramid   Upright pyramid   Inverted pyramid 1. The pyramid of energy is always upright. 1. The pyramid of biomass and the pyramid of numbers can be inverted. 2. In the upright pyramid, the number and biomass of organisms in the producer level of an ecosystem is the highest, which keeps on decreasing at each trophic level in a food chain. 2. In an inverted pyramid, the number and biomass of organisms in the producer level of an ecosystem is the lowest, which keeps on increasing at each tropic level. (d) Food chain and Food web   Food chain   Food web 1. It is a single linear sequence of organisms. 1. It contains a number of interconnected food chains. 2. Members present at higher trophic levels feed on single types of organisms. 2. One organism has alternate food sources. (e) Litter and detritus   Litter   Detritus 1. Litter contains all kinds of wastes generated above the ground. 1. Detritus is composed of the remains of dead plants and animals. 2. Litter contains both biodegradable and non-biodegradable matter. 2. Detritus contains only biodegradable matter. (f) Primary and secondary productivity   Primary productivity   Secondary productivity 1. It is defined as the amount of organic matter produced by producers per unit area over a period of time. 1. It is defined as the rate of production of organic matter by consumers over a period of time. Page No 257: Question 7: Describe the components of an ecosystem. ANSWER: An ecosystem is defined as an interacting unit that includes both the biological community as well as the non-living components of an area. The living and the non-living components of an ecosystem interact amongst themselves and function as a unit, which gets evident during the processes of nutrient cycling, energy flow, decomposition, and productivity. There are many ecosystems such as ponds, forests, grasslands, etc. The two components of an ecosystem are: (a) Biotic component: It is the living component of an ecosystem that includes biotic factors such as producers, consumers, decomposers, etc. Producers include plants and algae. They contain chlorophyll pigment, which helps them carry out the process of photosynthesis in the presence of light. Thus, they are also called converters or transducers. Consumers or heterotrophs are organisms that are directly (primary consumers) or indirectly (secondary and tertiary consumers) dependent on producers …

NCERT Solutions for Class 12 Science Biology Chapter 14 – Ecosystem Read More »

Here are the step-by-step solutions for Chapter 13 “Organisms And Populations” from the NCERT Book of Class 12 Science Biology. These solutions are highly favored by Biology students of Class 12 Science for their simplicity and effectiveness in completing homework assignments and exam preparation. Each question from the chapter, along with its corresponding answer, is presented here to assist you in understanding the concepts thoroughly and efficiently. Page No 239: Question 1: How is diapause different from hibernation? Answer: Diapause is a stage of suspended development to cope with unfavourable conditions. Many species of Zooplankton and insects exhibit diapause to tide over adverse climatic conditions during their development. Hibernation or winter sleep is a resting stage where in animals escape winters (cold) by hiding themselves in their shelters. They escape the winter season by entering a state of inactivity by slowing their metabolism. The phenomenon of hibernation is exhibited by bats, squirrels, and other rodents. Page No 239: Question 2: If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not? Answer: If a marine fish is placed in a fresh water aquarium, then its chances of survival will diminish. This is because their bodies are adapted to high salt concentrations of the marine environment. In fresh water conditions, they are unable to regulate the water entering their body (through osmosis). Water enters their body due to the hypotonic environment outside. This results in the swelling up of the body, eventually leading to the death of the marine fish. Page No 239: Question 3: Define phenotypic adaptation. Give one example. Answer: Phenotypic adaptation involves changes in the body of an organism in response to genetic mutation or certain environmental changes. These responsive adjustments occur in an organism in order to cope with environmental conditions present in their natural habitats. For example, desert plants have thick cuticles and sunken stomata on the surface of their leaves to prevent transpiration. Similarly, elephants have long ears that act as thermoregulators. Page No 239: Question 4: Most living organisms cannot survive at temperature above 45°C°. How are some microbes able to live in habitats with temperatures exceeding 100°C? Answer: Archaebacteria (Thermophiles) are ancient forms of bacteria found in hot water springs and deep sea hydrothermal vents. They are able to survive in high temperatures (which far exceed 100°C) because their bodies have adapted to such environmental conditions. These organisms contain specialized thermo-resistant enzymes, which carry out metabolic functions that do not get destroyed at such high temperatures. Page No 239: Question 5: List the attributes that populations but not individuals possess. Answer: A population can be defined as a group of individuals of the same species residing in a particular geographical area at a particular time and functioning as a unit. For example, all human beings living at a particular place at a particular time constitute the population of humans. The main attributes or characteristics of a population residing in a given area are:- (a) Birth rate (Natality): It is the ratio of live births in an area to the population of an area. It is expressed as the number of individuals added to the population with respect to the members of the population. (b) Death rate (Mortality): It is the ratio of deaths in an area to the population of an area. It is expressed as the loss of individuals with respect to the members of the population. (c) Sex ratio: It is the number of males or females per thousand individuals. (d) Age Distribution: It is the percentage of individuals of different ages in a given population. At any given time, the population is composed of individuals that are present in various age groups. The age distribution pattern is commonly represented through age pyramids. (e) Population density: It is defined as the number of individuals of a population present per unit area at a given time. Page No 239: Question 6: If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population? Answer: A population grows exponentially if sufficient amounts of food resources are available to the individual. Its exponential growth can be calculated by the following integral form of the exponential growth equation: Nt = Noert Where, Nt= Population density after time t NO= Population density at time zero r = Intrinsic rate of natural increase e = Base of natural logarithms (2.71828) From the above equation, we can calculate the intrinsic rate of increase (r) of a population. Now, as per the question, Present population density = x Then, Population density after two years = 2x t = 3 years Substituting these values in the formula, we get: ⇒ 2x = x e3r ⇒ 2 = e3r Applying log on both sides: ⇒ log 2 = 3r log e Hence, the intrinsic rate of increase for the above illustrated population is 0.2311. Page No 239: Question 7: Name important defence mechanisms in plants against herbivory. Answer: Several plants have evolved various mechanisms both morphological and chemical to protect themselves against herbivory. (1) Morphological defence mechanisms: (a) Cactus leaves (Opuntia) are modified into sharp spines (thorns) to deter herbivores from feeding on them. (b) Sharp thorns along with leaves are present in Acacia to deter herbivores. (c) In some plants, the margins of their leaves are spiny or have sharp edges that prevent herbivores from feeding on them. (2) Chemical defence mechanisms: (a) All parts of Calotropis weeds contain toxic cardiac glycosides, which can prove to be fatal if ingested by herbivores. (b) Chemical substances such as nicotine, caffeine, quinine, and opium are produced in plants as a part of self-defense. Page No 240: Question 8: An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree? Answer: An orchid growing on the branch of a mango tree is an epiphyte. Epiphytes are plants growing on other plants which however, do not derive nutrition from them. Therefore, the relationship between a mango tree and an orchid is an example of commensalisms, where one species …

NCERT Solutions for Class 12 Science Biology Chapter 13 – Organisms And Populations Read More »

Find simplified step-by-step explanations in the NCERT Solutions for Class 12 Science Biology Chapter 12: “Biotechnology And Its Applications.” These solutions are highly favored by Class 12 Science students for Biology, making them invaluable for completing homework assignments swiftly and preparing for exams. All questions and answers from Chapter 12 of the NCERT Book for Class 12 Science Biology are available here at no cost, aiding students in their studies. Page No 215: Question 1: Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because − (a) bacteria are resistant to the toxin (b) toxin is immature: (c) toxin is inactive: (d) bacteria encloses toxin in a special sac. ANSWER: toxin is inactive: In bacteria, the toxin is present in an inactive form, called prototoxin, which gets converted into active form when it enters the body of an insect. Page No 215: Question 2: What are transgenic bacteria? Illustrate using any one example. ANSWER: Transgenic bacteria contain foreign gene that is intentionally introduced into its genome. They are manipulated to express the desirable gene for the production of various commercially important products. An example of transgenic bacteria is E.coli. In the plasmid of E.coli, the two DNA sequences corresponding to A and B chain of human insulin are inserted, so as to produce the respective human insulin chains. Hence, after the insertion of insulin gene into the bacterium, it becomes transgenic and starts producing chains of human insulin. Later on, these chains are extracted from E.coli and combined to form human insulin. Page No 215: Question 3: Compare and contrast the advantages and disadvantages of production of genetically modified crops. ANSWER: The production of genetically modified (GM) or transgenic plants has several advantages. (i) Most of the GM crops have been developed for pest resistance, which increases the crop productivity and therefore, reduces the reliance on chemical pesticides. (ii) Many varieties of GM food crops have been developed, which have enhanced nutritional quality. For example, golden rice is a transgenic variety in rice, which is rich in vitamin A. (iii) These plants prevent the loss of fertility of soil by increasing the efficiency of mineral usage. (iv) They are highly tolerant to unfavourable abiotic conditions. (v) The use of GM crops decreases the post harvesting loss of crops. However, there are certain controversies regarding the use of genetically modified crops around the world. The use of these crops can affect the native biodiversity in an area. For example, the use of Bt toxin to decrease the amount of pesticide is posing a threat for beneficial insect pollinators such as honey bee. If the gene expressed for Bt toxin gets expressed in the pollen, then the honey bee might be affected. As a result, the process of pollination by honey bees would be affected. Also, genetically modified crops are affecting human health. They supply allergens and certain antibiotic resistance markers in the body. Also, they can cause genetic pollution in the wild relatives of the crop plants. Hence, it is affecting our natural environment. Page No 216: Question 4: What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit? ANSWER: Cry proteins are encoded by cry genes. These proteins are toxins, which are produced by Bacillus thuringiensis bacteria. This bacterium contains these proteins in their inactive from. When the inactive toxin protein is ingested by the insect, it gets activated by the alkaline pH of the gut. This results in the lysis of epithelial cell and eventually the death of the insect. Therefore, man has exploited this protein to develop certain transgenic crops with insect resistance such as Bt cotton, Bt corn, etc. Page No 216: Question 5: What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency. ANSWER: Gene therapy is a technique for correcting a defective gene through gene manipulation. It involves the delivery of a normal gene into the individual to replace the defective gene, for example, the introduction of gene for adenosine deaminase (ADA) in ADA deficient individual. The adenosine deaminase enzyme is important for the normal functioning of the immune system. The individual suffering from this disorder can be cured by transplantation of bone marrow cells. The first step involves the extraction of lymphocyte from the patient’s bone marrow. Then, a functional gene for ADA is introduced into lymphocytes with the help of retrovirus. These treated lymphocytes containing ADA gene are then introduced into the patient’s bone marrow. Thus, the gene gets activated producing functional T- lymphocytes and activating the patient’s immune system. Page No 216: Question 6: Diagrammatically represent the experimental steps in cloning and expressing an human gene (say the gene for growth hormone) into a bacterium like E. coli ? ANSWER: DNA cloning is a method of producing multiple identical copies of specific template DNA. It involves the use of a vector to carry the specific foreign DNA fragment into the host cell. The mechanism of cloning and transfer of gene for growth hormone into E.coli is represented below. Page No 216: Question 7: Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil? ANSWER: Recombinant DNA technology (rDNA) is a technique used for manipulating the genetic material of an organism to obtain the desired result. For example, this technology is used for removing oil from seeds. The constituents of oil are glycerol and fatty acids. Using rDNA, one can obtain oilless seeds by preventing the synthesis of either glycerol or fatty acids. This is done by removing the specific gene responsible for the synthesis. Page No 216: Question 8: Find out from internet what is golden rice. ANSWER: Golden rice is a genetically modified variety of rice, Oryza sativa,which has been developed as a fortified food for areas where there is a shortage of dietary vitamin A. It contains a precursor of pro-vitamin A, called beta-carotene, which has been introduced into the rice through genetic engineering. The rice plant naturally produces beta-carotene pigment in its leaves. However, it is absent in the …

NCERT Solutions for Class 12 Science Biology Chapter 12 – Biotechnology And Its Applications Read More »

Here are simplified, step-by-step NCERT Solutions for Class 12 Science Biology Chapter 11: Biotechnology – Principles And Processes. These solutions are highly favored by Biology students in Class 12 for their ease of understanding and clarity. They serve as valuable aids for swiftly completing homework assignments and effectively preparing for exams. Crafted by proficient experts, these NCERT Solutions ensure a 100% accuracy rate, providing students with reliable guidance throughout their studies. Page No 205: Question 1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet). Answer: Recombinant proteins are obtained from the recombinant DNA technology. This technology involves the transfer of specific genes from an organism into another organism using vectors and restriction enzymes as molecular tools. Ten recombinant proteins used in medical practice are − Recombinant protein Therapeutic use 1. Insulin Treatment for type I diabetes mellitus 2. Interferon-α Used for chronic hepatitis C 3. Interferon -β Used against herpes and viral enteritis 4. Coagulation factor VIII Treatment of haemophilia A 5. Coagulation factor IX Treatment of haemophilia B 6. DNAase I Treatment of cystic fibrosis 7. Anti-thrombin III Prevention of blood clot 8. Interferon B For treatment of multiple sclerosis 9. Human recombinant growth hormone For promoting growth in an individual 10. Tissue plasminogen activator Treatment of acute myocardial infarction Page No 205: Question 2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces. Answer: The name of the restriction enzyme is Bam H 1. Page No 205: Question 3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know? Answer: Enzymes are smaller in size than DNA molecules. This is because DNA contains genetic information for the development and functioning of all living organisms. It contains instructions for the synthesis of proteins and DNA molecules. On the other hand, enzymes are proteins which are synthesised from a small stretch of DNA known as ‘genes’, which are involved in the production of the polypeptide chain. Page No 205: Question 4: What would be the molar concentration of human DNA in a human cell? Consult your teacher. Answer: The molar concentration of human DNA in a human diploid cell is as follows: ⇒ Total number of chromosomes × 6.023 × 1023 ⇒ 46 × 6.023 × 10­­­23 ⇒ 2.77 ×1018 Moles Hence, the molar concentration of DNA in each diploid cell in humans is 2.77 × 10 23 moles. Page No 205: Question 5: Do eukaryotic cells have restriction endonucleases? Justify your answer. Answer: No, eukaryotic cells do not have restriction endonucleases. This is because the DNA of eukaryotes is highly methylated by a modification enzyme, called methylase. Methylation protects the DNA from the activity of restriction enzymes .These enzymes are present in prokaryotic cells where they help prevent the invasion of DNA by virus. Page No 205: Question 6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks? Answer: The shake flask method is used for a small-scale production of biotechnological products in a laboratory. On the other hand, stirred tank bioreactors are used for a large-scale production of biotechnology products. Stirred tank bioreactors have several advantages over shake flasks: (1) Small volumes of culture can be taken out from the reactor for sampling or testing. (2) It has a foam breaker for regulating the foam. (3) It has a control system that regulates the temperature and pH. Page No 205: Question 7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules. Answer: The palindromic sequence is a certain sequence of the DNA that reads the same whether read from 5’ → 3’ direction or from 3’→ 5’ direction. They are the site for the action of restriction enzymes. Most restriction enzymes are palindromic sequences. Five examples of palindromic sequences are: Page No 205: Question 8: Can you recall meiosis and indicate at what stage a recombinant DNA is made? Answer: Meiosis is a process that involves the reduction in the amount of genetic material. It is two types, namely meiosis I and meiosis II. During the pachytene stage of prophase I, crossing over of chromosomes takes place where the exchange of segments between non-sister chromatids of homlogous chromosomes takes place. This results in the formation of recombinant DNA. Page No 205: Question 9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker? Answer: A reporter gene can be used to monitor the transformation of host cells by foreign DNA. They act as a selectable marker to determine whether the host cell has taken up the foreign DNA or the foreign gene gets expressed in the cell. The researchers place the reporter gene and the foreign gene in the same DNA construct. Then, this combined DNA construct is inserted in the cell. Here, the reporter gene is used as a selectable marker to find out the successful uptake of genes of interest (foreign genes). An example of reporter genes includes lac Z gene, which encodes a green fluorescent protein in a jelly fish. Page No 206: Question 10: Describe briefly the followings: (a) Origin of replication (b) Bioreactors (c) Downstream processing Answer: (a) Origin of replication −Origin of replication is defined as the DNA sequence in a genome from where replication initiates. The initiation of replication can be either uni-directional or bi-directional. A protein complex recognizes the ‘on’ site, unwinds the two strands, and initiates the copying of the DNA. (b) Bioreactors − Bioreactors are large vessels used for the large-scale production of biotechnology products from raw materials. They provide optimal conditions to obtain the desired product by providing the optimum temperature, pH, vitamin, oxygen, etc. Bioreactors have an oxygen delivery system, a foam control system, …

NCERT Solutions for Class 12 Science Biology Chapter 11 – Biotechnology: Principles And Processes Read More »