Introduction to Biology

• Biology is the scientific study of life.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells.
• Gene theory: Hereditary information is encoded in DNA and passed from parents to offspring.
• Evolution: Populations of organisms change over time through natural selection.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow and exchange of energy and matter.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins.
• 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 the same area.
• Communities: Populations of different species interacting with each other.
• Ecosystems: Communities interacting with their physical environment.
• Biosphere: The part of Earth inhabited by living organisms.

Cell Structure and Function

• Cells are the basic units of life.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• The plasma membrane is a selectively permeable barrier that controls the movement of substances into and out of the cell.
• The nucleus contains the cell's genetic material in the form of DNA.
• Ribosomes are responsible for protein synthesis.
• The endoplasmic reticulum (ER) is involved in protein and lipid synthesis.
• The Golgi apparatus modifies, sorts, and packages proteins and lipids.
• Mitochondria are responsible for cellular respiration and energy production.
• Lysosomes contain enzymes for breaking down cellular waste.
• Cytoskeleton provides structural support and facilitates cell movement.

Genetics

• Genes are units of heredity that contain instructions for building proteins.
• DNA (deoxyribonucleic acid) is the molecule that carries genetic information.
• DNA is composed of nucleotides, each consisting of a sugar, a phosphate group, and a nitrogenous base.
• The four nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).
• DNA replicates to produce identical copies of itself during cell division.
• RNA (ribonucleic acid) is involved in protein synthesis.
• Transcription is the process of copying DNA into RNA.
• Translation is the process of using RNA to synthesize proteins.
• Mutations are changes in the DNA sequence that can lead to genetic variation.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the process by which individuals with advantageous traits are more likely to survive and reproduce.
• Adaptations are traits that enhance an organism's survival and reproduction in a particular environment.
• Genetic variation is the raw material for evolution.
• Mutation, gene flow, and genetic drift can introduce or alter genetic variation.
• Speciation is the process by which new species arise.
• Evidence for evolution includes fossils, comparative anatomy, embryology, and molecular biology.

Ecology

• 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 interacting with each other.
• Ecosystems consist of communities and their physical environment.
• Biomes are large-scale ecosystems characterized by specific climate conditions and vegetation.
• The biosphere is the part of Earth inhabited by living organisms.
• Energy flows through ecosystems from producers to consumers.
• Food chains and food webs depict the transfer of energy and nutrients in ecosystems.
• Nutrient cycles, such as the carbon cycle and nitrogen cycle, involve the movement of elements through ecosystems.
• Biodiversity refers to the variety of life on Earth.

Plant Biology

• Plants are multicellular, eukaryotic organisms that belong to the kingdom Plantae.
• Plants are autotrophs, meaning they produce their own food through photosynthesis.
• Plant cells contain chloroplasts, which are the sites of photosynthesis.
• Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose.
• Plant structures include roots, stems, leaves, flowers, fruits, and seeds.
• Roots anchor the plant and absorb water and nutrients from the soil.
• Stems provide support and transport water and nutrients throughout the plant.
• Leaves are the primary sites of photosynthesis.
• Flowers are involved in sexual reproduction.
• Fruits develop from flowers and contain seeds.
• Seeds contain embryos that can develop into new plants.

Animal Biology

• Animals are multicellular, eukaryotic organisms that belong to the kingdom Animalia.
• Animals are heterotrophs, meaning they obtain their food by consuming other organisms.
• Animal cells lack cell walls.
• Animal structures include tissues, organs, and organ systems.
• Tissues include epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
• Organs are composed of different tissues working together.
• Organ systems include the digestive system, respiratory system, circulatory system, excretory system, nervous system, and reproductive system.
• Animals exhibit diverse body plans and adaptations.
• Animals reproduce sexually or asexually.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, viruses, fungi, and protozoa.
• Microorganisms are ubiquitous and play important roles in ecosystems, industry, and human health.
• Bacteria are prokaryotic cells that can be beneficial or harmful.
• Viruses are non-cellular entities that require a host cell to replicate.
• Fungi are eukaryotic organisms that include yeasts, molds, and mushrooms.
• Protozoa are unicellular eukaryotic organisms that include parasites.
• Microorganisms can cause infectious diseases.
• Antibiotics are used to treat bacterial infections.
• Vaccines are used to prevent viral infections.