Introduction to Biology

Introduction to Biology

• Biology is the science of life, helping understand everything around us
• Biologists study life via testing hypotheses and theories
• Distinguishing between living and non-living is central to biology
• Living things share fundamental characteristics like carbon and hydrogen, but have unique features setting them apart from non-living things

Characteristics of Living Things

• Organisms consist of cells—the fundamental building blocks of life, varying in size and appearance, and carrying genetic material (DNA)
• Living organisms utilize energy and raw materials from food to conduct activities and maintain life
• Living organisms respond to stimuli from their environment
• Living organisms maintain homeostasis—keeping internal conditions stable despite external changes
• All organisms can reproduce, grow, and develop
• Living organisms evolve and adapt to the environment through hierarchical levels of organization starting with atoms

Levels of Biological Organization

• Atoms are the smallest units of a chemical element, forming molecules and macromolecules
• Molecules form when atoms bond with each other
• Cells are formed from molecules and macromolecules to make larger structures
• Tissues are formed from similar cells working together
• Organs are composed from two or more tissue types, such as muscle and nervous tissue
• Organ systems consist of groups of organs with related functions
• Organisms represent a complete, living individual
• Populations are groups of organisms of the same species in a specific area
• Communities consist of several interacting populations within an environment
• Ecosystems encompass a community interacting with its physical environment
• Biosphere encompasses all the Earth's ecosystems and is the highest level of organization

Cells

• Cells are the fundamental units of life, with various shapes and structures
• Cells are classified as prokaryotic (no nucleus) or eukaryotic (have a nucleus).
• Prokaryotic cells are simpler, smaller, and lack some organelles found in eukaryotic cells
• Eukaryotic cells contain a nucleus and various organelles, including mitochondria, chloroplasts, etc.

Cell Specialization

• Specialized cells perform particular functions and contain unique materials with distinctive shapes
• Differentiation is a process to form specialized cells, where cells change and take on specific tasks
• Different types of cells in organisms work together in complex ways
• Blood cells, like red blood cells and white blood cells, are examples of specialized cells with distinctive functions

Stem Cells

• Stem cells are unspecialized cells that can differentiate into various cell types, maintaining cellular diversity & function
• Stem cells also have the unique property of self-renewal, producing copies of themselves to replenish existing cell populations
• Self-renewal is the ability of stem cells to produce copies of themselves through symmetric or asymmetric cell division

Free Radicals

• Free radicals are harmful chemicals, naturally occurring and formed when oxygen reacts with specific molecules
• They damage DNA, enzymes, and membranes within cells, resulting in cell damage
• Free radicals can be eliminated by antioxidants, which help neutralize their harmful effects