Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• It encompasses a wide range of fields, from molecular biology to ecology.

Core Principles of Biology

• Cell theory states that all living organisms are composed of cells, which are the basic units of life.
• Genes, made of DNA, are the units of heredity and are passed from parents to offspring.
• Evolution: the process by which populations of organisms change over time, driven by natural selection and other mechanisms.
• Homeostasis: the maintenance of a stable internal environment despite external changes.
• Energy: life requires energy, typically from the sun or chemical compounds, to perform essential functions.

Levels of Biological Organization

• Molecules: atoms combine to form molecules, such as proteins, carbohydrates, lipids, and nucleic acids.
• Cells: the basic unit of life, consisting of organelles and other structures enclosed by a membrane.
• Tissues: groups of similar cells performing a specific function.
• Organs: structures composed of different tissues working together.
• Organ Systems: groups of organs that cooperate to perform major bodily functions.
• Organisms: individual living beings composed of organ systems.
• Populations: groups of individuals of the same species living in a specific area.
• Communities: all the populations of different species living in a specific area.
• Ecosystems: communities of organisms interacting with their physical environment.
• Biosphere: the sum of all ecosystems on Earth.

Cell Structure and Function

• Prokaryotic cells (bacteria and archaea) lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells (plants, animals, fungi, and protists) contain a nucleus and other membrane-bound organelles.
• The plasma membrane: a selectively permeable barrier that controls the movement of substances into and out of the cell.
• The nucleus: contains the cell's DNA and controls cellular activities.
• Ribosomes: synthesize proteins.
• Endoplasmic reticulum (ER): involved in protein and lipid synthesis.
• Golgi apparatus: modifies, sorts, and packages proteins and lipids.
• Mitochondria: generate energy (ATP) through cellular respiration.
• Chloroplasts (in plants): carry out photosynthesis.
• Lysosomes: contain enzymes for intracellular digestion.

Genetics

• DNA (deoxyribonucleic acid): the molecule that carries genetic information.
• Genes: segments of DNA that code for specific proteins.
• Chromosomes: structures made of DNA and proteins that contain genes. Humans have 46 chromosomes arranged in 23 pairs.
• DNA replication: the process by which DNA makes a copy of itself.
• Transcription: the process by which RNA is synthesized from a DNA template.
• Translation: the process by which proteins are synthesized from RNA.
• Mutations: changes in the DNA sequence that can lead to genetic variation.
• Mendelian genetics: principles of inheritance based on the work of Gregor Mendel, including dominance, segregation, and independent assortment.
• Genetic engineering: techniques used to manipulate and modify genes.

Evolution

• Natural selection: the process by which organisms with traits that enhance survival and reproduction are more likely to pass on their genes to future generations.
• Adaptation: traits that enhance an organism's survival and reproduction in a specific environment.
• Evidence for evolution: fossils, comparative anatomy, embryology, and molecular biology.
• Species: a group of organisms that can interbreed and produce fertile offspring.
• Speciation: the process by which new species arise.
• Phylogeny: the evolutionary history and relationships of organisms.

Ecology

• Ecosystems: communities of organisms interacting with their physical environment.
• Biomes: large-scale ecosystems characterized by specific climate conditions and plant communities.
• Food chains and food webs: illustrate the flow of energy through an ecosystem.
• Trophic levels: the position an organism occupies in a food chain (e.g., producers, consumers, decomposers).
• Population ecology: studies the factors that affect population size and distribution.
• Community ecology: studies the interactions between different species in a community.
• Conservation biology: aims to protect and preserve biodiversity.

Plant Biology

• Photosynthesis: the process by which plants convert light energy into chemical energy.
• Plant structure: roots, stems, leaves, flowers, and fruits.
• Vascular system: xylem (transports water) and phloem (transports nutrients).
• Plant reproduction: sexual and asexual reproduction.
• Plant hormones: regulate plant growth and development.

Animal Biology

• Animal tissues: epithelial, connective, muscle, and nervous tissue.
• Organ systems: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, and reproductive systems.
• Animal behavior: the study of how animals interact with their environment and each other.
• Animal development: the process by which an animal grows and develops from an embryo.

Microbiology

• Bacteria: single-celled prokaryotic organisms.
• Viruses: non-cellular entities that require a host to replicate.
• Fungi: eukaryotic organisms that include yeasts, molds, and mushrooms.
• Protists: a diverse group of eukaryotic organisms that are not plants, animals, or fungi.
• Microorganisms play important roles in nutrient cycling, disease, and biotechnology.

Biotechnology

• Genetic engineering: manipulating genes to produce desired traits.
• Cloning: creating genetically identical copies of organisms.
• Gene therapy: using genes to treat or prevent diseases.
• Biotechnology applications: medicine, agriculture, and industry.

Human Biology

• Anatomy: the study of the structure of the human body.
• Physiology: the study of the function of the human body.
• Human genetics: the study of genes, heredity, and genetic variation in humans.
• Human evolution: the study of the origins and evolution of humans.
• Human diseases: the study of the causes, prevention, and treatment of human diseases.