Introduction to Biology

• Biology is the scientific study of life
• Focuses on the structure, function, growth, origin, evolution, and distribution of living organisms
• The cell is the basic unit of life
• Genes are the basic unit of heredity
• Evolution is the engine that propels the creation and extinction of species
• Living organisms are open systems that survive by transforming energy and decreasing their local entropy

Key Concepts in Biology

• Cell Theory: All living organisms are composed of cells, and all cells come from pre-existing cells
• Gene Theory: Traits are inherited through genes, which are located on chromosomes
• Evolution: Life changes over time through processes like natural selection and genetic drift
• Homeostasis: Living organisms maintain stable internal conditions
• Energy: Life depends on the ability of organisms to obtain and use energy

Subdisciplines of Biology

• Biochemistry: The study of the chemical processes within and relating to living organisms
• Molecular Biology: The study of the molecular basis of biological activity; overlaps with biochemistry, genetics, and cell biology
• Cell Biology: The study of cell structure and function
• Genetics: The study of heredity and variation in organisms
• Evolutionary Biology: The study of the evolutionary processes that produced the diversity of life on Earth
• Ecology: The study of how organisms interact with each other and their environment
• Physiology: The study of the normal functions of living organisms and their parts
• Anatomy: The study of the structure of organisms and their parts
• Microbiology: The study of microorganisms, including bacteria, viruses, and fungi
• Botany: The scientific study of plants
• Zoology: The scientific study of animals

Characteristics of Life

• Organization: Living things exhibit a complex organization, from cells to tissues to organs to systems
• Metabolism: Living organisms carry out chemical reactions to obtain and use energy
• Growth: Living things increase in size or cell number
• Reproduction: Living organisms produce new organisms, either sexually or asexually
• Response to Stimuli: Living organisms react to changes in their environment
• Adaptation: Populations of living organisms evolve to become better suited to their environment
• Homeostasis: Maintaining a stable internal environment

The Scientific Method in Biology

• Observation: Begins with observing a phenomenon or identifying a problem
• Hypothesis: A testable explanation for the observation
• Experimentation: Designing and conducting experiments to test the hypothesis
• Data Analysis: Analyzing the data collected during the experiment
• Conclusion: Determining whether the data supports or refutes the hypothesis
• Communication: Sharing the results of the study with the scientific community

Levels of Biological Organization

• Smallest to largest: molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere
• Each level builds upon the previous one and exhibits emergent properties

Chemical Basis of Life

• Living organisms are composed of organic molecules like carbohydrates, lipids, proteins, and nucleic acids
• Carbon is the backbone of organic molecules due to its ability to form stable bonds
• Water is essential for life, as a solvent, in chemical reactions, and for regulating temperature

Cell Structure and Function

• Cells are the basic structural and functional units of life
• Prokaryotic cells lack a nucleus and other membrane-bound organelles; includes bacteria and archaea
• Eukaryotic cells have a nucleus and other membrane-bound organelles; includes animals, plants, fungi, and protists
• Organelles such as the nucleus, mitochondria, chloroplasts, and endoplasmic reticulum perform specific functions
• The plasma membrane controls the movement of substances into and out of the cell

Energy and Metabolism

• Metabolism is the sum of all chemical reactions that occur in an organism
• Catabolism breaks down complex molecules into simpler ones, releasing energy
• Anabolism builds complex molecules from simpler ones, requiring energy
• Enzymes are biological catalysts that speed up chemical reactions
• ATP (adenosine triphosphate) is the primary energy currency of the cell
• Photosynthesis converts light energy into chemical energy in plants and some bacteria
• Cellular respiration breaks down glucose to produce ATP in most organisms

Genetics and Heredity

• DNA (deoxyribonucleic acid) is the genetic material that carries hereditary information
• Genes are segments of DNA that encode for specific traits
• Chromosomes are structures made of DNA and proteins that carry genes
• DNA replication is the process by which DNA is copied
• Transcription is the process by which RNA is synthesized from DNA
• Translation is the process by which proteins are synthesized from RNA
• Mutations are changes in the DNA sequence that can lead to variations in traits
• Mendelian genetics describes the patterns of inheritance of traits from parents to offspring

Evolution and Diversity

• Evolution is the change in the genetic makeup of a population over time
• Natural selection is the process by which individuals with certain traits are more likely to survive and reproduce
• Adaptation is the process by which populations become better suited to their environment through natural selection
• Genetic drift is the random change in the frequency of alleles in a population
• Speciation is the process by which new species arise
• The fossil record provides evidence of past life and evolutionary changes
• Comparative anatomy and embryology reveal similarities between different species
• Molecular biology provides evidence of evolutionary relationships based on DNA and protein sequences
• Biodiversity refers to the variety of life on Earth, including the diversity of genes, species, and ecosystems

Ecology and Environment

• Ecology is the study of the interactions between organisms and their environment
• Populations are groups of individuals of the same species living in the same area
• Communities are groups of different species living in the same area
• Ecosystems are communities of organisms interacting with their physical environment
• Biomes are large-scale ecosystems characterized by specific climate and vegetation
• The biosphere is the sum of all ecosystems on Earth
• Food chains and food webs describe the flow of energy and nutrients through an ecosystem
• Trophic levels represent the different levels of feeding in an ecosystem
• Biogeochemical cycles describe the movement of elements such as carbon, nitrogen, and phosphorus through the environment
• Human activities can have a significant impact on the environment, leading to pollution, deforestation, and climate change

Plant Biology

• Plants are multicellular, eukaryotic organisms that are primarily photosynthetic
• Plant cells have cell walls made of cellulose and chloroplasts for photosynthesis
• Vascular tissues, such as xylem and phloem, transport water and nutrients throughout the plant
• Roots anchor the plant and absorb water and nutrients from the soil
• Stems provide support and transport materials between the roots and leaves
• Leaves are the primary sites of photosynthesis
• Flowers are the reproductive structures of plants
• Plant life cycles involve alternation of generations between a sporophyte and a gametophyte

Animal Biology

• Animals are multicellular, eukaryotic organisms that are heterotrophic
• Animal cells lack cell walls and chloroplasts
• Animals have diverse body plans and organ systems
• The nervous system coordinates and controls body functions
• The endocrine system produces hormones that regulate various processes
• The circulatory system transports blood, oxygen, and nutrients throughout the body
• The respiratory system exchanges gases between the body and the environment
• The digestive system breaks down food and absorbs nutrients
• The excretory system removes waste products from the body
• The immune system protects the body from disease
• Animals reproduce sexually, and their development involves fertilization and embryogenesis