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NCERT Solutions class 12 Biology PDF
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Chapter 1: Reproduction in Organisms
Chapter 2: Sexual Reproduction in Flowering Plants
Chapter 3: Human Reproduction
Chapter 4: Reproductive Health
Chapter 5: Principle of Inheritance and Variation
Chapter 6: Molecular Basis of Inheritance
Chapter 7: Evolution
Chapter 8: Human Health and Diseases
Chapter 10: Microbes in Human Welfare
Chapter 11: Biotechnology: Principles and Processes
Chapter 12: Biotechnology and its Applications
Chapter 13: Organisms and Populations
Chapter 14: Ecosystem
Chapter 15: Biodiversity and Conservation
Chapter 16: Environmental Issues
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Main Point to Ponder
Chapter-1: Reproduction in Organisms
Reproduction, a characteristic feature of all organisms for continuation of species; modes of reproduction – asexual and sexual reproduction; asexual reproduction – binary fission, sporulation, budding, gemmule formation, fragmentation; vegetative propagation in plants.
Chapter-2: Sexual Reproduction in Flowering Plants
Flower structure; development of male and female gametophytes; pollination – types, agencies and examples; outbreeding devices; pollen-pistil interaction; double fertilization; post fertilization events – development of endosperm and embryo, development of seed and formation of fruit; special modes-apomixis, parthenocarpy, polyembryony; Significance of seed dispersal and fruit formation.
Chapter-3: Human Reproduction
Male and female reproductive systems; microscopic anatomy of testis and ovary; gametogenesis – spermatogenesis and oogenesis; menstrual cycle; fertilisation, embryo development upto blastocyst formation, implantation; pregnancy and placenta formation (elementary idea); parturition (elementary idea); lactation (elementary idea).
Chapter-4: Reproductive Health
Need for reproductive health and prevention of Sexually Transmitted Diseases (STDs); birth control – need and methods, contraception and medical termination of pregnancy (MTP); amniocentesis; infertility and assisted reproductive technologies – IVF, ZIFT, GIFT (elementary idea for general awareness).
Chapter-5: Principles of Inheritance and Variation
Heredity and variation: Mendelian inheritance; deviations from Mendelism – incomplete dominance, co-dominance, multiple alleles and inheritance of blood groups, pleiotropy; elementary idea of polygenic inheritance; chromosome theory of inheritance; chromosomes and genes; Sex determination – in humans, birds and honey bee; linkage and crossing over; sex linked inheritance – haemophilia, colour blindness; Mendelian disorders in humans – thalassemia; chromosomal disorders in humans; Down’s syndrome, Turner’s and Klinefelter’s syndromes.
Chapter-6: Molecular Basis of Inheritance
Search for genetic material and DNA as genetic material; Structure of DNA and RNA; DNA packaging; DNA replication; Central dogma; transcription, genetic code, translation; gene expression and regulation – lac operon; genome and human and rice genome projects; DNA fingerprinting.
Origin of life; biological evolution and evidences for biological evolution (paleontology, comparative anatomy, embryology and molecular evidences); Darwin’s contribution, modern synthetic theory of evolution; mechanism of evolution – variation (mutation and recombination) and natural selection with examples, types of natural selection; Gene flow and genetic drift; Hardy – Weinberg’s principle; adaptive radiation; human evolution.
Chapter-8: Human Health and Diseases
Pathogens; parasites causing human diseases (malaria, dengue, chickengunia, filariasis, ascariasis, typhoid, pneumonia, common cold, amoebiasis, ring worm) and their control; Basic concepts of immunology – vaccines; cancer, HIV and AIDS; Adolescence – drug and alcohol abuse.
Chapter-9: Strategies for Enhancement in Food Production
Improvement in food production: Plant breeding, tissue culture, single cell protein, Biofortification, Apiculture and Animal husbandry.
Chapter-10: Microbes in Human Welfare
In household food processing, industrial production, sewage treatment, energy generation and microbes as biocontrol agents and biofertilizers. Antibiotics; production and judicious use.
Chapter-11: Biotechnology – Principles and processes
Genetic Engineering (Recombinant DNA Technology).
Chapter-12: Biotechnology and its Application
Application of biotechnology in health and agriculture: Human insulin and vaccine production, stem cell technology, gene therapy; genetically modified organisms – Bt crops; transgenic animals; biosafety issues, bio piracy and patents.
Chapter-13: Organisms and Populations
Organisms and environment: Habitat and niche, population and ecological adaptations; population interactions – mutualism, competition, predation, parasitism; population attributes – growth, birth rate and death rate, age distribution.
Ecosystems: Patterns, components; productivity and decomposition; energy flow; pyramids of number, biomass, energy; nutrient cycles (carbon and phosphorous); ecological succession; ecological services – carbon fixation, pollination, seed dispersal, oxygen release (in brief).
Chapter-15: Biodiversity and its Conservation
Concept of biodiversity; patterns of biodiversity; importance of biodiversity; loss of biodiversity; biodiversity conservation; hotspots, endangered organisms, extinction, Red Data Book, biosphere reserves, national parks, sanctuaries and Ramsar sites.
Chapter-16: Environmental Issues
Air pollution and its control; water pollution and its control; agrochemicals and their effects; solid waste management; radioactive waste management; greenhouse effect and climate change; ozone layer depletion; deforestation; any one case study as success story addressing environmental issue(s).
Which is a better mode of reproduction sexual or asexual? Why?
Arrange the following terms in the correct developmental sequence: Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.
Sporogenous tissue – pollen mother cell – microspore tetrad – Pollen grain – male gamete
During the development of microsporangium, each cell of the sporogenous tissue acts as a pollen mother cell and gives rise to a microspore tetrad, containing four haploid microspores by the process of meiosis (microsporogenesis). As the anther matures, these microspores dissociate and develop into pollen grains. The pollen grains mature and give rise to male gametes.
Write two major functions each of testis and ovary.
They produce male gametes called spermatozoa by the process of spermatogenesis.
The leydig cells of the seminiferous tubules secrete the male sex hormone called testosterone. Testosterone aids the development of secondary sex characteristics in males.
Functions of the ovary
They produce female gametes called ova by the process of oogenesis.
The growing Graffian follicles secrete the female sex hormone called estrogen. Estrogen aids the development of secondary sex characteristics in females.
Is sex education necessary in schools? Why?
The young individual or adolescents are more susceptible in acquiring various sexually transmitted diseases. Hence, providing information to them at the right time would help them to lead a reproductively healthy life and also protect them from the myths and misconceptions about various sex related issues.
What is pedigree analysis? Suggest how such an analysis, can be useful.
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
DNA-dependent DNA polymerases
DNA-dependent RNA polymerases
The DNA-dependent DNA polymerases use a DNA template for synthesizing a new strand of DNA, whereas DNA-dependent RNA polymerases use a DNA template strand for synthesizing RNA.
Attempt giving a clear definition of the term species.
Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
What is apiculture? How is it important in our lives?
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
Do eukaryotic cells have restriction endonucleases? Justify your answer.
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?
What is primary productivity? Give brief description of factors that affect primary productivity.
Primary productivity of an ecosystem depends on the variety of environmental factors such as light, temperature, water, precipitation, etc. It also depends on the availability of nutrients and the availability of plants to carry out photosynthesis.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity.
Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness.
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.