Here have been some major changes in 12th NCERT biology.
Changes in NCERT Biology will impact somehow on NEET & AIIMS 2019 Exam.
There have been some major changes in NCERT biology.

Here We have Discussed Major Changes in 12th NCERT Biology.

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Reproduction in Organism
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16 Add: Summary Budding and gemmule formation are the common asexual methods seen in lower animal
Human Reproduction
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51   Menstrual Hygiene
Maintenance of hygiene and sanitation during menstruation is very important. Take bath and clean yourself regularly. Use sanitary napkins or clean homemade pads. Change sanitary napkins or homemade pads after every 4-5 hrs as per the requirement. Dispose of the used sanitary napkins properly wrapping it with a used paper. Do not throw the used napkins in the drainpipe of toilets or in the open area. After handling the napkin wash hands with soap.
Reproductive Health
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58 The statutory ban on amniocentesis (a foetal sex determination test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo) for sex-determination to legally check increasing female foeticides, massive child immunization, etc., are some programmes that merit mention in this connection. Statutory ban on amniocentesis for sex-determination to legally check increasing menace female foeticides, masssive child immunisation, etc., are some programmes that merit mention in this connection. In aminocentesis some of the amniotic fluid of the developing foetus is taken to analyse the fetal cells and dissolved substances. This procedure is used to test for the presence of certain genetic disorders such as, down syndrome, haemoplilia, sickle-cell anemia, etc., determine the survivability of the foetus.
59 The world population which was around 2 billion (2000 million) in 1900 rocketed to about 6 billion by 2000. The world population which was around 2 billion (2000 million) in 1900 rocketed to about 6 billion by 2000 and 7.2 billion in 2011.
59 Out population which was approximately 350 million at the time of our independence reached close to the billion marks by 2000 and crossed 1 billion in May 2000. Our population which was approximately 350 million at the time of our independence reached close to the billion marks by 2000 and crossed 1.2 billion in May 2011.
59 According to the 2001 census report, the population growth rate was still around 1.7 percent, i.e. 17/1000/year,  a rate at which our population could double in 33 years. According to the 2011 census report, the population growth rate was less than 2 percent, i.e. 20/1000/year,  a rate at which our population could increase rapidly.
62  

The Medical Termination of Pregnancy (Amendment) Act, 2017 was enacted by the government of India with the intension of reducing the incidence of illegal abortion and consequent maternal mortality and morbidity. According to this Act, a pregnancy may be terminated on certain considered grounds within the first 12 weeks of pregnancy on the opinion of one registered medical practitioner. If the pregnancy has lasted more than  12 weeks, but fewer than 24 weeks, two registered medical practitioners must be of the opinion, formed  in good faith, that the required  ground exist. The grounds for such termination of pregnancies are :
(i) The continuation of the pregnancy would involve a risk to the life of the pregnant woman or of grave injury physical or mental health : or
(ii) There is a substantial risk that of the child were born, it would suffer from such physical or mental abnormalities as to be seriously handicapped.

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Sexually Transmitted Diseases (STDs)
Diseases or infections which are transmitted through sexual intercourse are collectively called sexually transmitted diseases (STD) or venereal diseases (VD) or reprodcutive tract infections (RTI). Gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and of course , the most discussed infection in the recent years, HIV leading to AIDS are some of the common STDs.

Sexually Transmitted Infections (STIs)
Diseases or infections which are transmitted through sexual intercourse are collectively called sexually transmitted Infections (STI) or venereal diseases (VD) or reprodcutive tract infections (RTI). Gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and of course , the most discussed infection in the recent years, HIV leading to AIDS are some of the common ST

Molecular Basis of Inheritance
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96 A nitrogenous base is linked to the pentose sugar through a N- glycosidic linkage to form a nucleoside A nitrogenous base is linked to the OH of 1'C pentose sugar through a N-glycosidic linkage to form a nucleoside
96 When a phosphate group is linked to 5' -OH of a nucleoside through phosphoester linkage, When a phosphate group is linked to OH of 5'C of a nucleoside through phosphoester linkage,
97 Similarly, at the other end of the polymer the ribose has a free 3' -OH group which is referred to as 3'- end of the polynucleotide chain. Similarly, at the other end of the polymer the sugar has a free 3' -OH group which is referred to as 3'- end of the polynucleotide chain.
107 Except the adenosine now forms base pair with uracil instead of thymine. Except the adenosine complements now forms base pair with uracil instead of thymine.
111 The process of translation requires transfer of genetic information from a polymer of nucleotides to a polymer of amino acids. The process of translation requires transfer of genetic information from a polymer of nucleotides to from a polymer of amino acids.
112

The salient features of genetic code are as follows:
(i) The codon is triplet. 61 codons code for amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.
(ii) One codon codes for only one amino acid, hence, it is unambiguous and specific.
(iii) Some amino acids are coded by more than one codon, hence the code is degenerate.
(iv) The codon is read in mRNA in a contiguous fashion. There are no punctuations
(v) The code is nearly universal: for example, from bacteria to human UUU would code for Phenylalanine (phe). Some exceptions to this rule have been found in mitochondrial codons, and in some protozoans.
(vi) AUG has dual functions. It codes for Methionine (met) , and it also act as initiato codon.

The salient features of genetic code are as follows:
(i) The codon is triplet. 61 codons code for amino acids and 3 codons do not code for any amino acids, hence they function as stop codons.
(ii) Some amino acids are coded by more than one codon, hence the code is degenerate.
(iii) The codon is read in mRNA in a contiguous fashion. There are no punctuations.
(iv) The code is nearly universal: for example, from bacteria to human UUU would code for Phenylalanine (phe). Some exceptions to this rule have been found in mitochondrial codons, and in some protozoans.
(v) AUG has dual functions. It codes for Methionine (met) , and it also act as initiator codon.
(vi) UAA, UAG, UGA are stop terminator codons.

114
Evolution
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141 Pre-historic cave art developed about 18,000 years ago. Agriculture came around 10,000 years back and human settlements started. Pre-historic cave art developed about 18,000 years ago One such cave paintings by Pre-historic humans can be seen at Bhimbetka rock shelter in Raisen district of Madhya Pradesh. Agriculture came around 10,000 years back and human settlements started.
Human Health & Deasease
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159 Drugs like barbiturates, amphetamines, benzodiazepines, lysergic acid diethyl amides (LSD), and other similar drugs, that are normally used as medicines to help patients cope with mental illnesses like depression and insomnia, are often abused. Drugs like barbiturates, amphetamines, benzodiazepines, and other similar drugs, that are normally used as medicines to help patients cope with mental illnesses like depression and insomnia, are often abused.
Strategies for Enhancement in Food Production
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176 Microbes are being grown on an industrial scale as source of good protein. Microbes like Spirulina can be grown easily on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food rich in protein, minerals, fats, carbohydrate and vitamins. Incidentally such utilisation also reduces environmental pollution. Microbes are being grown on an industrial scale as source of good protein.Blue- green algae like Spirulina can be grown easily on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food rich in protein, minerals, fats, carbohydrate and vitamins. Incidentally such utilisation also reduces environmental pollution.
176 It has been calculated that a 250 Kg cow produces 200 g of protein per day. In the same period, 250g of a micro-organism like Methylophilus methylotrophus, because of its high rate of biomass production and growth, can be expected to produce 25 tonnes of protein. Certain bacterial species like Methylophilus methylotrophus, because of its high rate of biomass production and growth, can be expected to produce 25 tonnes of protein.
Microbes in Human Welfare
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179 Microbes are diverse– protozoa, bacteria, fungi and microscopic plants viruses, viroids and also prions that are proteinacious infectious agents. Microbes are diverse– protozoa, bacteria, fungi and microscopic animal and plant viruses, viroids and also prions that are proteinacious infectious agents.

Biotechnology: Principles and Processes
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194 (ii) Maintenance of sterile (microbial contamination-free) ambiance in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc.

(ii) Bioprocess engineering
Maintenance of sterile (microbial contamination-free) ambiance in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc.

197
199 The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA but can still be selected out from non- recombinant ones by plating the transformants on ampicillin containing the medium. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA but can still be selected out from non-recombinant ones by plating the transformants on tetracycline containing medium.
200 This results into inactivation of the enzyme, which is referred to as insertional inactivation. This results into inactivation of the gene for synthesis of this enzyme, which is referred to as insertional inactivation.
208 (v) enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice. (v) enhanced nutritional value  food   , e.g. golden rice i.e., Vitamin ‘A’ enriched rice.
209 The toxin is coded by a gene named cry. The toxin is coded by a gene crylAc named cry.
Organisms and Populations
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220 perpetually rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal springs, and stinking compost pits, to name a few. Even our intestine is a unique habitat for hundreds of species of microbes.

rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost(snow laden) polar regions, high mountain tops, boiling thermal springs, and stinking compost pits, to name a few. Even our intestine is a unique habitat for hundreds of species of microbes.

222 Water: Next to temperature, water is the most important factor influencing the life of organisms. In fact, life on earth originated in water and is unsustainable without water. Its availability is so limited in deserts that only special adaptations make it possible to live there Water:  Water is another the most important factor influencing the life of organisms. In fact, life on earth originated in water and is unsustainable without water. Its availability is so limited in deserts that only special adaptations make it possible for the organism to live there
224 the organism has two other alternatives. the organism has two other alternatives for survival.
225 their stomata arranged in deep pits to minimize water loss through transpiration. their stomata arranged in deep pits (sunken) to minimise water loss through transpiration.
226 If you had ever been to any high altitude place (>3,500m Rohtang Pass near Manali and Mansarovar, If you had ever been to any high altitude place (>3,500m Rohtang Pass near Manali and Leh,
226 How do they live under such crushing pressures and do they have any special enzymes? How do they live under such high pressures and do they have any special enzymes?
236 as they move, stir up and flush out from the vegetation insects that otherwise might be difficult for the egrets to find and catch. as they move, stir up and flush out insects from the vegetation that otherwise might be difficult for the egrets to find and catch.
Ecosystem
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250 During succession some species colonise an area and their populations become more numerous, whereas populations of other species decline and even disappear. During succession some species colonise an area and whereas populations of other species decline and even disappear.
250 Succession is hence a process that starts where no living organisms are there Succession is hence a process that starts in an area where no living organisms are there
253 What is important is to appreciate that nutrients which are never lost from the ecosystems, they are recycled time and again indefinitely. What is important is to appreciate that nutrients which are never lost from the ecosystems, rather they are recycled time and again indefinitely.
256

SUMMARY
An ecosystem is a functional unit of nature and comprises abiotic and biotic components.

SUMMARY
A
n ecosystem is a structural and functional unit of nature and comprises abiotic and biotic components.
Environmental Issues
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278 Burning reduces the volume of the wastes, although it is generally not burnt to completion and open dumps often serve as the breeding ground for rats and flies.

Burning reduces the volume of the wastes, although it is generally not completely burnt to completion and open dumps often serve as the breeding ground for rats and flies.

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Important Changes In 12th NCERT Biology

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