| Science NCERT Exemplar Solutions (Class 6th to 10th) | ||||||||||||||
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| 6th | 7th | 8th | 9th | 10th | ||||||||||
| Science NCERT Exemplar Solutions (Class 11th) | ||||||||||||||
| Physics | Chemistry | Biology | ||||||||||||
| Science NCERT Exemplar Solutions (Class 12th) | ||||||||||||||
| Physics | Chemistry | Biology | ||||||||||||
Class 12th Biology NCERT Exemplar Solutions
1. Reproduction In Organisms
This chapter provides a general introduction to **reproduction**, the fundamental biological process ensuring the continuity of life from one generation to the next. It discusses the different life spans of organisms and the diverse modes of reproduction. The chapter categorizes reproduction into **asexual reproduction** (involving a single parent, producing genetically identical offspring, e.g., fission, budding, vegetative propagation) and **sexual reproduction** (involving two parents, fusion of gametes, leading to genetic variation). Understanding these modes lays the foundation for detailed studies of plant and human reproduction.
2. Sexual Reproduction In Flowering Plants
This chapter focuses specifically on **sexual reproduction in angiosperms** or flowering plants. It describes the structure of the flower as the reproductive organ, including the formation of male and female gametes (**gametogenesis**). The process of **pollination** (transfer of pollen) and different pollination agents are explained. The crucial event of **fertilisation** (fusion of gametes) and the unique **double fertilisation** in angiosperms are detailed. Post-fertilisation events leading to the development of the embryo, endosperm, seed, and fruit are discussed, along with special cases like apomixis and polyembryony.
3. Human Reproduction
This chapter delves into the complex process of **human reproduction**. It describes the structure and functions of the **male and female reproductive systems**. The formation of male and female gametes (**spermatogenesis** and **oogenesis**) is explained. The menstrual cycle in females is discussed. Key events like **fertilisation** (fusion of sperm and egg), **implantation** of the embryo in the uterus, embryonic development (**pregnancy**) with different trimesters, and ultimately **parturition** (childbirth) are covered. Basic concepts of lactation and reproductive hormones are also introduced.
4. Reproductive Health
This chapter addresses the important topic of **reproductive health**, encompassing physical, emotional, behavioural, and social well-being related to the reproductive system. It discusses key issues facing society, such as rapid population growth and strategies for control, including various **contraceptive methods** (barrier, chemical, surgical). Prevention of **sexually transmitted infections (STIs)**, common STIs, and their symptoms are covered. Infertility and **assisted reproductive technologies (ARTs)** like IVF, ZIFT, and GIFT are also discussed, along with the challenges and government initiatives in India regarding reproductive health.
5. Principles Of Inheritance And Variation
This foundational genetics chapter explores how traits are passed from one generation to the next (**heredity**) and the differences observed among individuals (**variation**). It details **Mendel's experiments** with pea plants and his fundamental **Laws of Inheritance** (Dominance, Segregation, Independent Assortment). Concepts like genes, alleles, genotype, phenotype, test cross, and back cross are explained. The chapter discusses deviations from Mendelian inheritance (incomplete dominance, codominance, multiple alleles) and introduces the **chromosomal theory of inheritance**, linkage, crossing over, and sex determination mechanisms.
6. Molecular Basis Of Inheritance
This chapter delves into the molecular mechanisms underlying heredity. It describes the structure of **DNA** and **RNA**, identifying DNA as the primary genetic material (evidence from Griffith, Avery, Hershey-Chase). Processes like **DNA replication** (copying DNA), **transcription** (synthesizing RNA from DNA), and **translation** (synthesizing protein from mRNA) are explained in detail. The **genetic code**, gene regulation (e.g., **lac operon**), and the **Human Genome Project** are discussed, providing a comprehensive understanding of how genetic information is stored, expressed, and transmitted at the molecular level.
7. Evolution
This chapter explores the process of **evolution**, the gradual change in life forms over vast periods of time, leading to the diversity of organisms on Earth. It discusses theories on the origin of life (e.g., Oparin-Haldane hypothesis). Various lines of **evidence for evolution** are presented, including fossils (paleontology), comparative anatomy, embryology, and molecular evidence. **Darwin's theory of natural selection** is explained as a key mechanism of evolution. Concepts like adaptive radiation, genetic drift, gene flow, Hardy-Weinberg principle, and the evolutionary history of man are also covered, illustrating how life has diversified and adapted.
8. Human Health And Diseases
This chapter focuses on factors affecting **human health** and the common diseases. It differentiates between health and disease. Causes of diseases are discussed, primarily focusing on **infectious diseases** caused by pathogens (bacteria, viruses, fungi, protozoans, helminths) like typhoid, pneumonia, common cold, malaria, amoebiasis, ascariasis, filariasis, ringworm, AIDS, and cancer. The **human immune system**, different types of immunity (innate and acquired), vaccination, allergy, autoimmunity, and the harmful effects of **drug and alcohol abuse** are also covered, emphasizing disease prevention and maintaining good health.
9. Strategies For Enhancement In Food Production
This chapter explores strategies to increase and improve the quantity and quality of **food production** to meet the growing population's needs, especially crucial in India. It covers **plant breeding** techniques for developing high-yielding, disease-resistant, and improved quality crop varieties (e.g., Green Revolution). **Tissue culture** and micropropagation for rapid plant multiplication are discussed. **Animal husbandry** practices, including the management of farms for cattle (dairy), poultry (eggs, meat), fisheries (pisciculture), and apiculture (beekeeping), are explained as ways to enhance livestock production, promoting efficient and scientific methods for food security.
10. Microbes In Human Welfare
This chapter highlights the many beneficial roles that **microorganisms** play in human life and the environment, moving beyond their disease-causing potential. It discusses their use in household products (e.g., making curd, bread, cheese, idli/dosa), industrial production (e.g., antibiotics like penicillin, beverages, organic acids, enzymes), **sewage treatment** for wastewater purification, production of **biogas** ($\textsf{CH}_4$), and as **biocontrol agents** (using microbes to control pests) and **biofertilisers** (enhancing soil fertility). The chapter showcases the significant positive contributions of microbes in various sectors, contributing to sustainable development.
11. Biotechnology: Principles And Processes
This foundational chapter introduces **biotechnology**, defining it as the use of living organisms or their components to create useful products or processes. It focuses on the core principles of **genetic engineering**, which involves manipulating genetic material (**recombinant DNA technology**). Key tools used in genetic engineering are discussed, such as restriction enzymes (molecular scissors), cloning vectors (plasmids, viruses), and competent host cells. The basic processes involved in rDNA technology, including isolation of genetic material, gene cloning, and gene transfer methods, are explained, providing the technical basis for modern biotechnology applications.
12. Biotechnology And Its Applications
Building upon the principles, this chapter explores the diverse and impactful **applications of biotechnology** in various fields. It discusses applications in **agriculture**, such as developing genetically modified (GM) crops for improved yield, pest resistance (e.g., Bt cotton), herbicide tolerance, or enhanced nutritional value (e.g., Golden Rice). Applications in **medicine** include the production of therapeutic proteins (e.g., recombinant insulin), vaccines, gene therapy for treating genetic disorders, and molecular diagnosis. The chapter also touches upon ethical issues and biosafety concerns related to biotechnology and GM organisms, reflecting the societal implications.
13. Organisms And Populations
This ecology chapter introduces the study of individual organisms and their interactions with their environment, as well as the dynamics of **populations** (groups of individuals of the same species). It discusses how organisms respond to various **environmental factors** (temperature, water, light, soil) through **adaptations** (morphological, physiological, behavioural). **Population ecology** explores population attributes like size, density, birth rate, death rate, age distribution, sex ratio, and growth models (exponential and logistic). Different types of **interspecific interactions** (mutualism, competition, predation, parasitism, commensalism, amensalism) are also explained, highlighting the complex web of relationships in nature.
14. Ecosystem
This chapter introduces the concept of an **ecosystem** as a structural and functional unit of nature comprising interacting **biotic** (living) and **abiotic** (non-living) components. It discusses the structure of an ecosystem (species composition, stratification). Key **ecosystem functions** are explored: **productivity** (rate of biomass production), **decomposition** (breakdown of organic matter), **energy flow** through different trophic levels in **food chains** and **food webs** (following the 10% law), and **nutrient cycling** (biogeochemical cycles like carbon, phosphorus, nitrogen). Ecological succession and ecosystem services are also discussed, highlighting the interconnectedness and vital roles of ecosystems in sustaining life.
15. Biodiversity And Conservation
This chapter emphasizes the importance of **biodiversity**, the variety of life at all levels (genetic, species, ecological). It discusses patterns of biodiversity (latitudinal gradients, species-area relationship) and its significance for ecosystem stability, human survival, and well-being. Major threats to biodiversity, collectively known as the "Evil Quartet" (habitat loss/fragmentation, over-exploitation, alien species invasion, co-extinctions), are explained. Strategies for **conservation** are discussed, including **in-situ conservation** (protecting species in their natural habitats like national parks, wildlife sanctuaries, biosphere reserves, sacred groves in India) and **ex-situ conservation** (protecting species outside natural habitats like zoos, botanical gardens, seed banks), stressing the urgent need to protect Earth's rich biodiversity.
16. Environmental Issues
This chapter addresses major **environmental issues** arising from human activities and their impact on the planet. Topics include air pollution (causes, effects, control), water pollution (sources, effects, sewage treatment), soil pollution, and solid waste management. It discusses the effects of deforestation, **climate change** (global warming), **ozone layer depletion**, and degradation of natural resources. The chapter emphasizes the need for sustainable practices, waste reduction, and environmental protection measures, encouraging responsible actions at individual and societal levels to mitigate these issues and ensure a healthier environment, relevant to addressing environmental challenges in India.
Sample Paper
This entry provides a **Sample Paper** designed as a practice tool for students using the Class 12th Biology NCERT Exemplar Solutions. It offers a comprehensive collection of questions covering the concepts and topics from all the preceding chapters (1-16). Attempting this sample paper helps students assess their understanding of the syllabus, identify their strengths and weaknesses, practice time management under exam conditions, and gain confidence for their actual board examinations. It serves as a valuable resource for effective revision and evaluation of preparedness in Biology.