CBSE 11 Biology

THE LIVING WORLD

The chapter discusses the diversity of living organisms, the necessity of classification, and the principles of taxonomic categorization. It highlights the importance of nomenclature in identifying species globally, as well as the hierarchical structure of taxonomic categories from species to kingdom. The text emphasizes the evolving nature of classification systems and their relevance in understanding biodiversity, ecology, and the relationships among different organisms.

BIOLOGICAL CLASSIFICATION

Biological classification has evolved from early morphological criteria adopted by Aristotle to a sophisticated five-kingdom classification proposed by Whittaker, which includes Monera, Protista, Fungi, Plantae, and Animalia. This classification considers various factors like cell structure, body organization, and evolutionary relationships. The chapter also briefly discusses acellular organisms like viruses and their unique characteristics.

PLANT KINGDOM

The chapter provides an overview of the plant kingdom, discussing five major groups: algae, bryophytes, pteridophytes, gymnosperms, and angiosperms. Each group is characterized by unique reproductive and structural features, reflecting evolutionary adaptations. The importance of each group to ecological systems and human activities is highlighted, emphasizing the roles of algae in carbon fixation and nutrition, the diverse forms of bryophytes, the vascular elements of pteridophytes, the exposed seeds of gymnosperms, and the enclosed seeds of angiosperms.

ANIMAL KINGDOM

The chapter discusses the classification of animals based on fundamental features such as levels of organization, symmetry, presence of coelom, segmentation, and notochord. It provides an overview of various phyla within the animal kingdom, detailing their distinct characteristics and organization. Additionally, it highlights the significance of these classification traits in understanding animal biology and evolution.

MORPHOLOGY OF FLOWERING PLANTS

Flowering plants display a vast diversity in morphology, including variations in roots, stems, leaves, flowers, fruits, and seeds. The root system can be either tap or fibrous, serving functions such as water absorption and food storage. The flower, a modified shoot for sexual reproduction, can exhibit numerous structural characteristics and inflorescence types, which significantly aid in the classification and identification of plant families.

ANATOMY OF FLOWERING PLANTS

The anatomy of flowering plants is structured into various tissues that organize into three main systems: epidermal, ground, and vascular. These systems are crucial for supporting plant functions such as water and nutrient transport, and photosynthesis. Dicotyledonous and monocotyledonous plants display distinct internal anatomical characteristics influenced by their structure and growth processes.

STRUCTURAL ORGANISATION IN ANIMALS

The structural organization of animals emphasizes the division of labor across cells, tissues, organs, and organ systems to ensure survival and functionality. In multicellular organisms, basic tissues combine to form organs that conduct specific functions. Frogs, as members of the class Amphibia, serve as an example to understand organ systems, including their distinctive morphology and anatomy, which are essential for their survival in varied environments.

CELL: THE UNIT OF LIFE

Cells are the fundamental units of life, forming the basis of all living organisms, and can be classified as prokaryotic or eukaryotic based on the presence of membrane-bound nuclei and organelles. The cell theory, formulated by Schleiden and Schwann, posits that all living organisms are composed of cells that arise from pre-existing cells. This chapter explores the structure and function of various cell organelles, emphasizing their roles in maintaining life's processes.

BIOMOLECULES

The chapter discusses the chemical composition of living organisms, highlighting the types of biomolecules such as proteins, nucleic acids, and polysaccharides. It emphasizes the significance of both primary and secondary metabolites in biological processes and provides insights into the structure and function of enzymes, detailing how they catalyze biochemical reactions. Additionally, the chapter explores the role of water as the most abundant chemical in living systems and the diversity of macromolecules crucial for life.

CELL CYCLE AND CELL DIVISION

The chapter outlines the critical processes of the cell cycle and cell division, distinguishing between mitosis and meiosis. It describes how cells replicate and divide through sequential phases, ensuring genetic continuity and variation. Key events during interphase and the stages of mitosis and meiosis are elaborated to highlight their significance in organism growth and reproduction.

PHOTOSYNTHESIS IN HIGHER PLANTS

RESPIRATION IN PLANTS

The chapter discusses the process of respiration in plants, detailing how energy is obtained from food through cellular respiration, including glycolysis, fermentation, and aerobic respiration. It highlights the differences between anaerobic and aerobic pathways, the role of respiration in plants, and the importance of ATP in energy transfer. Additionally, the respiratory pathway is described as an amphibolic pathway that supports both catabolism and anabolism, with the respiratory quotient (RQ) illustrating the type of substrates used.

PLANT GROWTH AND DEVELOPMENT

The chapter focuses on plant growth and development, highlighting the processes of growth, differentiation, and their interrelation. It discusses the phases of growth, the role of meristems, and the impact of environmental factors and plant growth regulators (PGRs) on plant physiology. The chapter emphasizes the significance of both intrinsic and extrinsic factors in achieving optimal growth outcomes in plants.

BREATHING AND EXCHANGE OF GASES

The chapter details the respiratory system's structure and functioning, emphasizing the importance of gas exchange. It covers breathing mechanics, gas transport in blood, and the regulation of respiration. Additionally, various disorders affecting the respiratory system are discussed, highlighting the significance of maintaining respiratory health.

BODY FLUIDS AND CIRCULATION

The chapter discusses the essential role of blood and lymph in transporting nutrients and waste in vertebrates. It describes the composition of blood, including plasma and formed elements, along with the mechanisms of circulation including the functions of the heart and the differences between open and closed circulatory systems. Additionally, it addresses the regulation of cardiac activity and the common disorders of the circulatory system.

EXCRETORY PRODUCTS AND THEIR ELIMINATION

Animals accumulate various nitrogenous wastes, including ammonia, urea, and uric acid, due to metabolic processes. The excretory system plays a crucial role in eliminating these wastes and maintaining homeostasis, particularly in humans where the kidneys filter blood to produce urine through three main processes: filtration, reabsorption, and secretion. Different structures, including nephrons and various excretory organs, are vital in this process along with hormonal regulation.

LOCOMOTION AND MOVEMENT

Movement is a vital feature of all living beings, including various forms such as protoplasmic streaming and locomotion, which occurs primarily in search of resources or safety. The chapter elaborates on the types of movements within human cells, focusing on amoeboid, ciliary, and muscular movements. It highlights the structure and function of muscle types and the skeletal system, noting the importance of muscle contraction mechanisms and the variety of joints facilitating movement.

Neural Control and Coordination

The neural system plays a vital role in coordinating and integrating functions of various organs, maintaining homeostasis, and processing information. Neurons, as the functional units of the neural system, are excitable cells that transmit nerve impulses through a series of electrical changes. The chapter details the structure of the human nervous system, including the central and peripheral systems, and explains the mechanisms of nerve impulse generation and transmission at synapses.

CHEMICAL COORDINATION AND INTEGRATION

Chemical coordination and integration in the human body is primarily achieved through hormones produced by various endocrine glands, which regulate metabolic processes, growth, and various physiological functions. Hormones act as intercellular messengers, and their effects are mediated through specific receptors on target cells. The chapter discusses the structure, function, and mechanisms of action for major endocrine glands and their hormones, including the hypothalamus, pituitary, thyroid, and adrenal glands, along with their impact on health and disease.