Introduction to Biology and Its Branches

Topic Subtitle

• Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development, and evolution.
• Biology examines a vast array of topics, from the structure of cells to the interactions within ecosystems.

Branches of Biology

• Cell biology: Studies the structure and function of cells.
• Genetics: Studies heredity and variation in organisms.
• Molecular biology: Studies biological processes at the molecular level.
• Microbiology: Studies microorganisms.
• Botany: Studies plants.
• Zoology: Studies animals.
• Ecology: Studies the interactions between organisms and their environment.
• Physiology: Studies the function of living organisms and their parts.
• Evolutionary biology: Studies the processes that have transformed life on Earth.
• Biochemistry: Studies the chemical processes in living organisms.

Key Concepts in Biology

• Cell theory: States that all living things are composed of cells. Cells are the basic units of structure and function in living things. Cells come from pre-existing cells.
• Evolution: The process by which populations of organisms change over time. Driven by mechanisms like natural selection, genetic drift, and gene flow. Key to understanding the diversity of life.
• Homeostasis: The maintenance of a stable internal environment in an organism. Essential for survival and function of cells, tissues, and organs.
• Metabolism: All chemical reactions that occur within an organism. Includes both catabolism (breaking down molecules) and anabolism (building up molecules). Fundamental to energy production and utilization.
• DNA: Deoxyribonucleic acid. Contains genetic information, and necessary for protein synthesis in all known organisms (except some viruses).
• Genes: Sections of DNA that encode for specific proteins.

Fundamental Processes

• Photosynthesis: Process by which plants and some other organisms use light energy to convert water and carbon dioxide into sugar (glucose).
• Respiration: Process by which organisms break down glucose to release energy. Aerobic respiration uses oxygen; anaerobic occurs without oxygen.
• Reproduction: The process by which organisms produce offspring. Can be sexual, involving two parents, or asexual, involving one parent.
• Growth and Development: Increase in size and complexity of an organism, proceeding via the precise interactions of molecular components and cellular activities.
• Adaptation: Inherited characteristic that enhances the survival and reproduction of an organism in specific environments. Shapes the diversity of life.

Levels of Biological Organization

• Organisms: Individual living things.
• Populations: Groups of individuals of the same species in a given area.
• Communities: All populations of different species in a given area.
• Ecosystems: All living organisms (biotic) in an area and their non-living environment (abiotic).
• Biosphere: All the ecosystems on Earth.