Biology

Plant Anatomy focuses primarily on the internal structure of angiosperms. The study begins with the classification of meristematic and permanent tissues, explaining how cells differentiate to perform specific functions. A significant portion of the syllabus is dedicated to the internal structure of dicot and monocot roots, stems, and leaves. You are expected to distinguish between them based on the arrangement of vascular bundles—such as the radial arrangement in roots versus the conjoint, collateral arrangement in stems.

Plant Physiology is a vital unit that explores the functional mechanics of how plants live, grow, and respond to their environment. The curriculum moves beyond basic structures to explain the complex biochemical and physical processes that sustain plant life. It begins with water relations, covering concepts like osmosis, diffusion, and transpiration, which explain how plants lift water against gravity.

Photosynthesis is a foundational unit that explores how green plants convert light energy into chemical energy. It is defined as a complex physio-chemical process where carbohydrates are synthesized from carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen ) as a byproduct. The syllabus focuses on the chloroplast as the primary site of this action, emphasizing the role of photosynthetic pigments like chlorophyll a, chlorophyll b, and carotenoids in capturing specific wavelengths of light.

Respiration is a vital physiological process where organic compounds (mainly glucose) are oxidized to release energy in the form of ATP. The syllabus breaks this down into two main types: Aerobic respiration, which requires oxygen and yields a high amount of energy (38 or 36 ATP), and Anaerobic respiration (fermentation), which occurs in the absence of oxygen and yields only 2ATP. You are expected to understand the cellular site of these reactions—the cytoplasm for Glycolysis and the mitochondria for the later stages—and how enzymes catalyze each step to power the plant's metabolic activities.

Plant Hormones, also known as Phytohormones, are defined as organic substances produced naturally in plants that regulate physiological processes like growth, development, and movement at very low concentrations. These chemicals act as messengers, synthesized in one part of the plant (like root or shoot tips) and translocated to other parts to exert their effects. The syllabus categorizes these hormones into two functional groups: Growth Promoters, which include Auxins, Gibberellins, and Cytokinins that encourage cell division and elongation; and Growth Inhibitors, primarily Abscisic Acid (ABA) and Ethylene, which regulate dormancy, leaf fall (abscission), and fruit ripening.

Plant Growth in plants is defined as an irreversible, permanent increase in size, volume, or weight, typically driven by cell division and enlargement. Unlike animals, plants exhibit indeterminate growth due to the presence of meristems (apical, lateral, and intercalary). The process follows a characteristic S-shaped (Sigmoid) growth curve, which consists of a slow lag phase, a rapid exponential (log) phase, and a declining stationary phase.

Genetic Materials under the Genetics unit focuses on identifying and understanding the molecules that carry hereditary information. The curriculum primarily establishes DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) as the two types of nucleic acids found in living organisms.

Mendelian Genetics serves as the foundation for understanding how traits are passed from parents to offspring. Gregor Mendel, known as the Father of Genetics, formulated his principles by studying seven pairs of contrasting traits in pea plants (Pisum sativum). The syllabus primarily focuses on his two major experiments: the Monohybrid Cross, which examines a single trait (like plant height) and leads to the Law of Dominance and the Law of Segregation, and the Dihybrid Cross, which examines two traits simultaneously (like seed shape and color) to establish the Law of Independent Assortment.

Linkage and Crossing Over are pivotal concepts that explain how traits are inherited and why genetic variation occurs. These two processes essentially act as opposing forces during meiosis.

A mutation is defined as a sudden, heritable change in the nucleotide sequence of an organism's genome. In the context of your syllabus, these are classified primarily into Gene Mutations (point mutations affecting a single base pair) and Chromosomal Mutations (changes in the structure or number of chromosomes). Mutations can occur spontaneously due to errors during DNA replication or can be induced by external factors called mutagens, such as UV radiation, X-rays, or chemicals like mustard gas. While many mutations are harmful or "silent," they are the ultimate source of all genetic variation, providing the raw material upon which natural selection acts.

Embryology is a crucial sub-unit within the "Reproduction and Development" section. It primarily focuses on the intricate biological processes that transform a single-celled zygote into a complex multicellular organism. For human embryology, the syllabus covers the stages of gametogenesis (spermatogenesis and oogenesis), the chemical and physical events of fertilization, and the subsequent stages of development including cleavage, blastulation, and gastrulation. A major emphasis is placed on the formation of the three primary germ layers—ectoderm, mesoderm, and endoderm—which serve as the foundation for organogenesis.

Biotechnology unit serves as a bridge between theoretical genetics and practical application, focusing on how biological systems can be engineered for human benefit. The curriculum begins with the fundamentals of Genetic Engineering, specifically the Recombinant DNA (rDNA) Technology process. This includes understanding the "molecular tools" like restriction enzymes (molecular scissors), ligases (molecular glue), and vectors (carriers like plasmids). You will study the step-by-step procedure of gene cloning: from isolating a specific DNA segment to inserting it into a host cell (like E. coli) to produce desired proteins or traits.

Animal Tissues are categorized into four fundamental types based on their location, structure, and specialized functions. The study of these tissues, known as histology, explains how groups of similar cells work together with intercellular substances to perform specific tasks. Epithelial tissue serves as the body’s primary covering and lining, providing protection and facilitating absorption and secretion. Connective tissue, the most abundant type, supports and binds other tissues together—ranging from fluid blood to rigid bone. Muscular tissue is specialized for contraction and movement, categorized into skeletal, smooth, and cardiac types.

Animal tissues are categorized into four fundamental types based on their structure and specific functions. These tissues work in coordination to maintain the body's internal environment and facilitate movement, protection, and communication. 1. Epithelial Tissue 2.Connective Tissue 3. Muscular Tissue 4. Nervous Tissue

Gametogenesis is the biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. In humans, this occurs in the gonads and is divided into two primary types: Spermatogenesis in males and Oogenesis in females. The process is essential for sexual reproduction, ensuring that the offspring maintain a constant chromosome number ($2n$) after the fusion of sperm and egg.

Development of Frog (Rana tigrina) is a foundational topic that explores the transformation from a single-celled zygote into a complex multicellular organism. This process, known as embryogenesis, begins with fertilization, which occurs externally in water. Once the egg is fertilized, it undergoes cleavage—a series of rapid mitotic divisions. In frogs, this cleavage is holoblastic (complete) but unequal due to the presence of yolk at the vegetal pole, eventually forming a hollow ball of cells called the blastula.

Digestive System in the syllabus (Zoology) focuses on the anatomy and physiology of human nutrition. The curriculum transitions from the structural organization of the alimentary canal—including the histology of the gut wall (mucosa, submucosa, muscularis, and serosa)—to the functional role of associated glands like the liver, pancreas, and salivary glands. You are expected to understand how food is mechanically and chemically broken down as it moves from the buccal cavity to the stomach and small intestine.

The Human Respiratory System is a vital biological complex designed for the exchange of gases—specifically taking in oxygen and expelling carbon dioxide. In the Class 12 NEB Zoology syllabus, the system is described through two main lenses: the Conducting Part and the Respiratory Part. The journey of air begins at the external nostrils, moving through the nasal cavity (where it is filtered and warmed), the pharynx, and the larynx (voice box), before entering the trachea. The trachea then bifurcates into the left and right bronchi, which further divide into a tree-like network of bronchioles within the lungs.

Circulatory System is a vital unit within the Animal Physiology section. It focuses on the mechanisms of transport, the anatomy of the heart, and the physiological processes that maintain homeostasis.

Excretory System focuses primarily on human osmoregulation and the elimination of nitrogenous wastes. The system is centered around the kidneys, which are bean-shaped organs located retroperitoneally. Each kidney contains millions of functional units called nephrons. These nephrons perform the critical task of filtering blood to remove urea, excess salts, and water. The process begins with glomerular filtration in the Bowman's capsule, followed by selective reabsorption of essential nutrients (like glucose and amino acids) in the convoluted tubules, and finally tubular secretion to maintain ionic balance.

The Human Nervous System is a complex network of specialized cells that coordinate body activities by transmitting signals between different parts of the body. In the system is primarily categorized into the Central Nervous System (CNS), which includes the brain and spinal cord, and the Peripheral Nervous System (PNS), consisting of cranial and spinal nerves. The functional unit of this system is the neuron, which operates through electrochemical impulses. The syllabus emphasizes the structure of the brain (forebrain, midbrain, and hindbrain), the mechanism of nerve impulse conduction via the sodium-potassium pump, and the physiology of reflex actions, which are involuntary responses to stimuli mediated by the reflex arc.

Sense Organs focuses primarily on the detailed anatomy and physiology of the human eye and ear. These organs are categorized as sensory receptors that detect external stimuli—light for the eye (photoreceptor) and sound/equilibrium for the ear (phonoreceptor and statoreceptor). The syllabus requires a deep understanding of how these organs convert physical energy into nerve impulses that the brain can interpret.

Endocrinology is a vital sub-section of the "Control and Coordination" unit. It focuses on the study of the endocrine system, which regulates physiological processes through the secretion of hormones directly into the bloodstream. Unlike the nervous system’s rapid electrical signals, the endocrine system provides slower, long-term chemical regulation of functions such as growth, metabolism, sexual development, and homeostasis.

Human Reproductive System is a major unit that covers the anatomy, physiology, and hormonal regulation of human reproduction. The syllabus focuses on the structural details of both male and female systems, the process of gamete formation (gametogenesis), the menstrual cycle, and embryonic development.

In the Class 12 NEB Biology syllabus (specifically within the Zoology section), the chapter on Human Population focuses on the demographic trends, the biological impacts of rapid growth, and the socio-economic challenges associated with population dynamics. The curriculum describes the population as a functional group of individuals of the same species occupying a particular area. It covers key demographic determinants such as natality (birth rate), mortality (death rate), and migration, explaining how these factors interact to determine the growth rate of a nation.

In the Class 12 Biology syllabus under the National Examination Board (NEB) of Nepal, the study of Health Disorders focuses primarily on the physiological malfunctions of the human body, categorized into respiratory, circulatory, and excretory systems. Students explore chronic conditions such as Asthma, Bronchitis, and Emphysema, focusing on how environmental factors and lifestyle choices like smoking damage the alveoli and respiratory tract. The syllabus also covers cardiovascular issues, including Hypertension (High Blood Pressure), Myocardial Infarction (Heart Attack), and Angina Pectoris, emphasizing the role of cholesterol and arterial blockage.

The syllabus begins with Human Diseases, where you study the life cycles and control measures of parasites like Entamoeba histolytica, Plasmodium (Malaria), and Wuchereria bancrofti (Elephantiasis). This transition into Medical Zoology is crucial for understanding public health challenges in Nepal. Furthermore, the curriculum emphasizes Economic Zoology, detailing the commercial rearing of organisms. This includes Pisciculture (fish farming), Apiculture (honey bee farming), and Sericulture (silk production), providing students with the technical knowledge required for entrepreneurship in the agricultural sector.

Microbial Diseases and Application of Microbiology bridges the gap between theoretical biology and practical health and industry. This unit explores the dual nature of microbes: as pathogenic agents that cause significant health burdens and as biological tools that drive modern technology.