Introduction to Biology

• Biology is the scientific study of life.
• It encompasses the structure, function, growth, origin, evolution, and distribution of living organisms.
• It classifies and describes living things, their functions, how species come into existence, and how they interact with each other and the environment.
• Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms are organized based on a hierarchy from molecules to biomes.

Subdisciplines of Biology

• Biochemistry studies the chemical processes within and relating to living organisms.
• Botany studies plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell biology studies the structure, function, and behavior of cells.
• Ecology studies the interactions of living organisms with each other and their environment.
• Evolutionary biology studies the processes that have led to the diversity of life on Earth.
• Genetics studies heredity and variation in organisms.
• Microbiology studies microorganisms, including bacteria, viruses, fungi, protozoa, and algae.
• Molecular biology studies the structure and function of biological macromolecules, including proteins and nucleic acids.
• Physiology studies the functions and mechanisms in a living system.
• Zoology studies animals, including their physiology, anatomy, behavior, genetics, ecology, evolution, and classification.

Characteristics of Life Processes

• Living organisms exhibit several key characteristics that distinguish them from non-living matter.
• These characteristics include organization, metabolism, growth, adaptation, response to stimuli, reproduction, and homeostasis.

Organization

• Living organisms are highly organized, meaning they contain specific components coordinated and working together.
• This organization occurs on multiple scales, from molecules to cells to tissues to organs to organ systems to organisms.
• Viruses are on the border of living and non-living because they are organized but need a host to reproduce.

Metabolism

• Metabolism is the sum of all chemical reactions that occur within a living organism.
• These reactions enable organisms to obtain and use energy.
• Metabolism involves two main processes: catabolism (breaking down molecules to release and store energy) and anabolism (using energy to build complex molecules).
• All life depends on metabolic processes to provide energy for the other life processes.

Growth

• Growth refers to an increase in size or number of cells in an organism.
• It involves the synthesis of new cellular components and the organization of these components into functional structures.
• Growth can occur through cell division (in unicellular organisms or for tissue repair/development in multicellular organisms) or cell enlargement (increasing the size of individual cells).

Adaptation

• Adaptation is the process by which organisms evolve traits that enhance their survival and reproduction in a particular environment.
• These adaptations can be structural, physiological, or behavioral.
• Adaptations arise through random genetic mutations; beneficial mutations are selected over time.

Response to Stimuli

• Living organisms are able to respond to stimuli in their environment.
• Stimuli can be various, including chemical cues, light, temperature, pressure, or gravity.
• Responses may be fast and short-lived (e.g., a plant bending toward light) or slow and long-term (e.g., hibernation).
• These responses are crucial for survival.

Reproduction

• Reproduction is the process by which organisms generate new individuals of the same species.
• It can be asexual (involving only one parent and producing genetically identical offspring) or sexual (involving two parents and producing genetically diverse offspring).
• Reproduction is essential for the continuation of life and the transmission of genetic information.

Homeostasis

• Homeostasis is the ability of an organism to maintain a stable internal environment despite changes in the external environment.
• This involves regulating various factors, such as temperature, pH, water balance, and nutrient levels.
• Homeostasis is essential for maintaining optimal conditions for cellular functions and overall survival.
• Examples include body temperature, blood pH, and glucose concentration.