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| Non-Rationalised Science NCERT Notes and Solutions (Class 12th) | ||||||||||||||
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Class 12th Biology NCERT Notes and Solutions (Non-Rationalised)
1. Reproduction In Organisms
This chapter provides an overview of reproduction as a fundamental biological process ensuring the continuity of species. It discusses the diverse modes of reproduction in organisms, categorizing them into **asexual reproduction** (involving a single parent, like fission, budding, vegetative propagation) and **sexual reproduction** (involving two parents and the fusion of gametes). The chapter also introduces concepts like lifespan and different phases in the life cycle (juvenile, reproductive, senescent), laying the groundwork for detailed studies of specific reproductive processes in subsequent chapters.
2. Sexual Reproduction In Flowering Plants
This chapter focuses on the detailed process of **sexual reproduction in angiosperms** (flowering plants). It covers the structure of the flower as the reproductive organ, gametogenesis (formation of microspores/pollen and megaspores/ovules), pollination (transfer of pollen), and the crucial event of **fertilisation** (fusion of male and female gametes). The post-fertilisation changes leading to the development of the embryo, endosperm, seed, and fruit are explained. Special modes like apomixis and polyembryony are also discussed, highlighting the complexities of plant reproduction.
3. Human Reproduction
This chapter describes the intricate process of **human reproduction**. It details the structure and function of the **male and female reproductive systems**. The formation of gametes (**spermatogenesis** and **oogenesis**) is explained. The processes of menstruation, fertilisation (fusion of sperm and egg), implantation of the embryo in the uterus, and subsequent embryonic development (**pregnancy**) are covered. The stages of development from zygote to blastocyst and the events of childbirth (**parturition**) are also discussed, along with the basics of lactation.
4. Reproductive Health
This chapter addresses the crucial topic of **reproductive health**, defined as a state of physical, emotional, behavioral, and social well-being related to the reproductive system. It discusses major issues including population growth and control strategies (various **contraceptive methods**), prevention of **sexually transmitted infections (STIs)**, infertility and **assisted reproductive technologies (ARTs)** like IVF, ZIFT, GIFT, and ICSI. Challenges and government initiatives in India regarding reproductive health are also highlighted, promoting awareness and responsible reproductive behaviour for a healthy society.
5. Principles Of Inheritance And Variation
This foundational chapter in genetics explores how traits are inherited and the sources of variation. It details **Mendel's experiments** with pea plants and his **Laws of Inheritance** (Dominance, Segregation, Independent Assortment). Deviations from Mendelian inheritance, such as incomplete dominance, co-dominance, multiple alleles, and polygenic inheritance, are discussed. Concepts like the **chromosomal theory of inheritance**, linkage, crossing over, **sex determination** (e.g., in humans, birds), and common mendelian disorders (e.g., colour blindness, sickle-cell anaemia) are also covered, explaining the mechanisms behind heredity.
6. Molecular Basis Of Inheritance
This chapter delves into the molecular details of heredity. It describes the structure of **DNA** and **RNA**, identifying DNA as the primary genetic material. The key processes of **DNA replication** (making copies of DNA), **transcription** (synthesizing RNA from DNA template), and **translation** (synthesizing protein from mRNA template) are explained. The concept of the **genetic code**, gene regulation (e.g., **lac operon**), and the **Human Genome Project** are discussed, providing a deep understanding of how genetic information is stored, expressed, and transferred.
7. Evolution
This chapter explores the process of **evolution**, the gradual change in life forms over vast periods, resulting in the diversity we see today. It discusses theories on the origin of life (chemical evolution). Various lines of **evidence for evolution** from paleontology (fossils), comparative anatomy, embryology, and molecular biology are presented. **Darwin's theory of natural selection** and the mechanisms driving evolution (mutation, genetic drift, gene flow) are explained. Concepts like adaptive radiation (e.g., Darwin's finches) and the evolutionary history of man are also covered, illustrating how life has adapted and diversified.
8. Human Health And Disease
This chapter focuses on the factors affecting human health and the common diseases. It introduces the concept of health and the causes of diseases, primarily focusing on **infectious diseases** caused by pathogens (bacteria, viruses, fungi, protozoans, helminths) like typhoid, pneumonia, common cold, malaria, and AIDS. The **human immune system**, its types (innate and acquired), and mechanisms of defense are explained. Concepts like vaccination, allergy, autoimmunity, and the harmful effects of **drug and alcohol abuse** are also discussed, promoting understanding of health management and disease prevention.
9. Strategies For Enhancement In Food Production
Addressing the challenge of feeding a large population, this chapter explores strategies to improve the quantity and quality of food production. It covers **plant breeding** techniques for developing high-yielding, disease-resistant varieties (e.g., Green Revolution in India). **Tissue culture** and micropropagation techniques for producing large numbers of plants quickly are discussed. **Animal husbandry** practices, including management of farms for cattle, poultry, fisheries, and apiculture, are explained to enhance the production of milk, eggs, meat, and fish. The chapter aims to provide insight into methods for increasing food availability.
10. Microbes In Human Welfare
This chapter highlights the beneficial roles of **microorganisms** in various aspects of human life, contrasting their image as disease-causing agents. It discusses the use of microbes in household products (e.g., making curd, bread, 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 indispensable positive contributions of microbes to society and the environment.
11. Biotechnology : Principles And Processes
This foundational chapter introduces **biotechnology**, the use of biological processes, organisms, or systems to produce products or services. It focuses on the core principles of **genetic engineering**, including the creation of **recombinant DNA (rDNA)** technology. Key techniques and tools used in genetic engineering are discussed, such as restriction enzymes (molecular scissors), cloning vectors (for carrying foreign DNA), gene transfer methods, and downstream processing. The chapter outlines the steps involved in producing genetically modified organisms, providing the technical basis for modern biotechnological applications.
12. Biotechnology And Its Applications
Building upon the principles, this chapter explores the diverse and significant applications of **biotechnology**. It discusses applications in **agriculture**, such as producing genetically modified (GM) crops (e.g., Bt cotton, Golden Rice) for increased yield, pest resistance, or improved nutritional value. 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 broader 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 (physiological, morphological, behavioral). **Population ecology** explores population attributes like size, density, birth and death rates, age distribution, and growth models (exponential and logistic). Different types of **interspecific interactions** (mutualism, competition, predation, parasitism, commensalism, amensalism) are also explained.
14. Ecosystem
This chapter introduces the concept of an **ecosystem** as a functional unit comprising biotic (living) and abiotic (non-living) components interacting together. 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% rule), 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.
15. Biodiversity And Conservation
This chapter emphasizes the importance of **biodiversity**, the variety of life at all levels of biological organization (genetic, species, ecosystem). It discusses patterns of biodiversity (latitudinal gradients, species-area relationship) and its significance for ecosystem stability and human well-being. Major threats to biodiversity, collectively known as the "Evil Quartet" (habitat loss and fragmentation, over-exploitation, alien species invasions, co-extinctions), are explained. Strategies for **conservation** are discussed, including **in-situ conservation** (national parks, wildlife sanctuaries, biosphere reserves, sacred groves in India) and **ex-situ conservation** (zoological parks, botanical gardens, seed banks), stressing the urgent need to protect life on Earth.
16. Environmental Issues
This chapter addresses major **environmental issues** resulting from human activities and their impact on the planet. Topics include air pollution (causes, effects, control measures), 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 and environmental protection, encouraging responsible actions to mitigate these issues and ensure a healthier future, particularly relevant in addressing environmental challenges in India.