Introduction to Biology

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

Characteristics of Life

• Organization: Living things exhibit a complex organization, from cells to tissues, organs, and organ systems
• Metabolism: Living organisms carry out chemical reactions to obtain and use energy (e.g., photosynthesis, respiration)
• Growth: Living things increase in size or cell number
• Reproduction: Organisms produce new organisms, either sexually or asexually
• Response to stimuli: Living things react to changes in their environment
• Adaptation: Organisms evolve adaptations that enable them to survive and reproduce in their environment
• Homeostasis: Maintenance of a stable internal environment

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins
• Cells: Basic unit of life; molecules form organelles, such as the nucleus and mitochondria, which make up cells
• Tissues: Similar cells performing a specific function are organized into tissues (e.g., muscle tissue, nervous tissue)
• Organs: Different tissues are organized into organs (e.g., heart, brain)
• Organ systems: Organs that work together form organ systems (e.g., digestive system, circulatory system)
• Organisms: Individual living entities composed of organ systems
• Populations: Groups of individuals of the same species living in a particular area
• Communities: Populations of different species living and interacting in an area
• Ecosystems: Communities interacting with their physical environment
• Biosphere: The portion of Earth inhabited by life

Basic Biological Principles

• Cell theory: All living things 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: The genetic makeup of a population changes over time

Scientific Method

• Observation: Observing a phenomenon or identifying a problem
• Hypothesis: Formulating 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: Drawing conclusions based on the data and determining whether the hypothesis is supported or refuted

Major fields of biology

• Biochemistry: Study of the chemical processes within and relating to living organisms
• Molecular biology: Study of the structure and function of biological macromolecules
• Cell biology: Study of cell structure and function
• Genetics: Study of heredity and variation
• Evolutionary biology: Study of the evolutionary processes that have produced the diversity of life
• Ecology: Study of the interactions between organisms and their environment
• Physiology: Study of the function of living organisms and their parts
• Anatomy: Study of the structure of living organisms

Importance of Biology

• Understanding the human body: Biology is essential for understanding human health and disease
• Addressing environmental issues: Biology helps us understand and address environmental challenges such as climate change, pollution, and biodiversity loss
• Improving agriculture: Biology plays a critical role in developing new crops and farming practices
• Advancing biotechnology: Biology is the foundation of biotechnology, which has applications in medicine, agriculture, and industry

Cell Structure

• All living organisms are composed of cells
• Cells are the basic structural and functional units of life
• There are two main types of cells: prokaryotic and eukaryotic

Prokaryotic Cells

• Lack a nucleus and other membrane-bound organelles
• Genetic material is located in the cytoplasm in a region called the nucleoid
• Generally smaller and simpler than eukaryotic cells
• Examples include bacteria and archaea

Eukaryotic Cells

• Contain a nucleus and other membrane-bound organelles
• Nucleus houses the cell's genetic material (DNA)
• Larger and more complex than prokaryotic cells
• Examples include protists, fungi, plants, and animals

Key Eukaryotic Cell Structures

• Nucleus: Contains the cell's DNA and controls cell activity
• Endoplasmic reticulum (ER): Involved in protein and lipid synthesis
• Golgi apparatus: Modifies, sorts, and packages proteins and lipids
• Mitochondria: Site of cellular respiration, which generates energy (ATP)
• Lysosomes: Contain enzymes that break down waste materials and cellular debris
• Ribosomes: Site of protein synthesis
• Cell membrane: Outer boundary of the cell, regulates the passage of substances in and out

Cell Membrane

• Composed of a phospholipid bilayer with embedded proteins
• Selectively permeable, meaning it controls which substances can pass through
• Involved in cell communication and adhesion

Cell Transport

• Movement of substances across the cell membrane
• Passive transport: Does not require energy (e.g., diffusion, osmosis)
• Active transport: Requires energy (e.g., transport proteins, endocytosis, exocytosis)

Cellular Respiration

• Process by which cells break down glucose to produce energy in the form of ATP
• Occurs in the mitochondria
• Involves glycolysis, the Krebs cycle, and the electron transport chain

Photosynthesis

• Process by which plants and other organisms convert light energy into chemical energy
• Occurs in chloroplasts
• Involves light-dependent reactions and the Calvin cycle

Cell Communication

• Cells communicate with each other through chemical signals
• Signals can be local (e.g., paracrine signaling) or long-distance (e.g., endocrine signaling)
• Signals bind to receptors on target cells, triggering a response

Cell Cycle

• The life cycle of a cell, including growth, DNA replication, and cell division
• Consists of interphase (G1, S, G2) and mitosis (or meiosis)
• Cell cycle is tightly regulated to ensure proper cell division

DNA Structure and Function

• Deoxyribonucleic acid (DNA) is the genetic material of all living organisms
• DNA molecule is a double helix composed of two complementary strands
• Each strand is made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine)
• DNA carries the instructions for building proteins and other molecules

RNA Structure and Function

• Ribonucleic acid (RNA) is involved in protein synthesis
• RNA molecule is typically single-stranded
• RNA contains uracil (U) instead of thymine (T)
• Types of RNA include messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Gene Expression

• Process by which the information encoded in a gene is used to synthesize a functional gene product (protein or RNA)
• Involves transcription (DNA to RNA) and translation (RNA to protein)

Genetics and Heredity

• Genetics is the study of heredity and variation
• Genes are units of heredity that determine traits
• Genes are located on chromosomes
• Alleles are different versions of a gene
• Genotype is the genetic makeup of an organism
• Phenotype is the observable characteristics of an organism

Patterns of Inheritance

• Mendelian genetics: Principles of segregation and independent assortment
• Dominant and recessive alleles
• Incomplete dominance and codominance
• Sex-linked traits
• Polygenic inheritance

Evolution

• Evolution is the change in the genetic makeup of a population over time
• Natural selection is the primary mechanism of evolution
• Adaptation: Inherited traits that enhance survival and reproduction
• Evidence for evolution: Fossils, comparative anatomy, embryology, molecular biology, biogeography

Mechanisms of Evolution

• Mutation: Random changes in DNA sequence
• Gene flow: Movement of genes between populations
• Genetic drift: Random changes in allele frequencies due to chance events
• Natural selection: Differential survival and reproduction based on heritable traits

Ecology

• Ecology is the study of the interactions between organisms and their environment
• Populations: Groups of individuals of the same species living in a particular area
• Communities: Populations of different species living and interacting in an area
• Ecosystems: Communities interacting with their physical environment
• Biosphere: The portion of Earth inhabited by life

Ecological Interactions

• Competition: Organisms compete for resources such as food, water, and space
• Predation: One organism (the predator) consumes another organism (the prey)
• Symbiosis: Close and long-term interaction between two different species (e.g., mutualism, commensalism, parasitism)
• Food chains and food webs: Show the flow of energy and nutrients through an ecosystem

Population Ecology

• Study of population size, density, distribution, and dynamics
• Factors affecting population growth: Birth rate, death rate, immigration, emigration
• Carrying capacity: The maximum population size that an environment can support

Community Ecology

• Study of the interactions between different species in a community
• Species diversity: The variety of species in a community
• Succession: The process of change in the species structure of an ecological community over time

Ecosystem Ecology

• Study of the flow of energy and nutrients through an ecosystem
• Primary producers: Autotrophs that convert sunlight into chemical energy (e.g., plants)
• Consumers: Heterotrophs that obtain energy by eating other organisms (e.g., herbivores, carnivores, omnivores)
• Decomposers: Break down dead organic matter (e.g., bacteria, fungi)
• Biogeochemical cycles: The movement of elements (e.g., carbon, nitrogen, phosphorus) through ecosystems