जीव विज्ञान का परिचय

• Biology is the scientific study of life
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms

Core Principles of Biology

• Cell theory: All living organisms are composed of cells
• Gene theory: Hereditary information is encoded in DNA and passed from parents to offspring
• Evolution: Life evolves over time through processes like natural selection
• Homeostasis: Living organisms maintain stable internal conditions

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA, proteins, and carbohydrates
• Cells: The basic unit of life, containing organelles and carrying out life processes
• Tissues: Groups of similar cells performing a specific function
• Organs: Structures composed of different tissues working together
• Organ systems: Groups of organs that cooperate to perform major bodily functions
• Organisms: Individual living entities composed of organ systems
• Populations: Groups of individuals of the same species living in a specific area
• Communities: Populations of different species interacting in a specific area
• Ecosystems: Communities and their physical environment interacting as an ecological unit
• Biosphere: The sum of all ecosystems on Earth

Key Biological Processes

• Metabolism: The sum of all chemical reactions that occur within an organism
• Includes anabolism (building up) and catabolism (breaking down)
• Cellular respiration: Process by which cells convert glucose into usable energy (ATP)
• Photosynthesis: Process by which plants and other organisms convert light energy into chemical energy
• Reproduction: The production of new individuals, either sexually or asexually
• Growth and development: Increase in size and complexity of an organism over time
• Homeostasis: Maintaining a stable internal environment despite external changes
• Evolution: Change in the genetic makeup of a population over time

Cell Structure and Function

• Cells are the basic structural and functional units of life
• Two main types of cells: prokaryotic and eukaryotic
• Prokaryotic cells: Lack a nucleus and other membrane-bound organelles
• Bacteria and Archaea
• Eukaryotic cells: Have a nucleus and other membrane-bound organelles
• Protists, fungi, plants, and animals

Cell Organelles

• Nucleus: Contains the cell's DNA and controls cell activities
• Ribosomes: Synthesize proteins
• Endoplasmic reticulum (ER): Involved in protein and lipid synthesis
• Rough ER has ribosomes; smooth ER does not
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids
• Mitochondria: Generate ATP through cellular respiration
• Chloroplasts: Conduct photosynthesis (in plants and algae)
• Lysosomes: Contain enzymes for breaking down cellular waste
• Vacuoles: Store water, nutrients, and waste products
• Cell membrane: Controls the movement of substances into and out of the cell

Genetics and Heredity

• Genes: Units of heredity that encode specific traits
• DNA: Deoxyribonucleic acid, the molecule that carries genetic information
• Chromosomes: Structures made of DNA and proteins that contain genes
• Genotype: The genetic makeup of an organism
• Phenotype: The observable characteristics of an organism
• Inheritance: The passing of traits from parents to offspring

DNA Structure and Replication

• DNA is a double helix composed of nucleotides
• Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base
• Four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T)
• A pairs with T; C pairs with G
• DNA replication: The process of copying DNA
• DNA polymerase is the enzyme that catalyzes DNA replication
• Results in two identical DNA molecules

Gene Expression

• Gene expression: The process by which the information encoded in a gene is used to synthesize a protein
• Transcription: The process of copying DNA into RNA
• RNA polymerase is the enzyme that catalyzes transcription
• Translation: The process of using RNA to synthesize a protein
• Ribosomes are the site of translation
• RNA: Ribonucleic acid, a molecule similar to DNA
• Types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA)
• Codon: A sequence of three nucleotides that codes for a specific amino acid

Evolution and Natural Selection

• Evolution: Change in the genetic makeup of a population over time
• Natural selection: The process by which organisms with traits that are better suited to their environment survive and reproduce more successfully
• Adaptation: A trait that increases an organism's fitness in its environment
• Evidence for evolution: fossil record, comparative anatomy, comparative embryology, molecular biology, biogeography

Mechanisms of Evolution

• Mutation: A change in the DNA sequence
• Gene flow: The movement of genes between populations
• Genetic drift: Random changes in allele frequencies
• Natural selection: Differential survival and reproduction based on traits

Taxonomy and Classification

• Taxonomy: The science of classifying organisms
• Linnaean system: A hierarchical system of classification
• Taxa: Groups of organisms in the classification system
• Domain, kingdom, phylum, class, order, family, genus, species
• Three domains of life: Bacteria, Archaea, and Eukarya

Ecology

• Ecology: The study of the interactions between organisms and their environment
• Ecosystem: A community of organisms and their physical environment
• Biomes: Large geographic areas with similar climate and vegetation
• Population ecology: The study of population size, density, distribution, and dynamics
• Community ecology: The study of interactions between different species in a community

Ecological Interactions

• Competition: When two or more species require the same limited resource
• Predation: When one organism (the predator) eats another organism (the prey)
• Symbiosis: A close and long-term interaction between two different species
• Mutualism (both benefit), commensalism (one benefits, the other is unaffected), parasitism (one benefits, the other is harmed)

Biological Diversity and Conservation

• Biodiversity: The variety of life on Earth
• Conservation biology: The study and protection of biodiversity
• Threats to biodiversity: habitat loss, invasive species, pollution, climate change, overexploitation
• Importance of biodiversity: ecosystem services, economic benefits, ethical considerations

Plant Biology

• Plants are multicellular, eukaryotic organisms that are autotrophic
• Autotrophic: Produce their own food through photosynthesis
• Plant structure: roots, stems, leaves
• Plant reproduction: sexual and asexual reproduction
• Vascular plants: have vascular tissue (xylem and phloem) for transporting water and nutrients
• Nonvascular plants: lack vascular tissue

Animal Biology

• Animals are multicellular, eukaryotic organisms that are heterotrophic
• Heterotrophic: Obtain food by consuming other organisms
• Animal classification: vertebrates and invertebrates
• Vertebrates: have a backbone (spinal column)
• Invertebrates: lack a backbone
• Animal tissues: epithelial, connective, muscle, nervous

Human Biology

• Humans are complex multicellular organisms with organ systems working together
• Organ systems: skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, reproductive, immune
• Human genetics: study of human genes, inheritance, and genetic disorders
• Human evolution: the evolutionary history of humans
• Human health: factors affecting human health and disease

Microbiology

• Microbiology: The study of microorganisms
• Microorganisms: Bacteria, archaea, viruses, fungi, protists
• Bacteria: Prokaryotic cells with diverse metabolic capabilities
• Viruses: Acellular entities that require a host to replicate
• Fungi: Eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds)
• Protists: Diverse group of eukaryotic microorganisms
• Importance of microorganisms: nutrient cycling, decomposition, disease, biotechnology