Introduction to Biology

• Biology is the scientific study of life
• Explores the structure, function, growth, origin, evolution, and distribution of living organisms
• Encompasses a wide range of fields, including botany, zoology, microbiology, genetics, and ecology

Core Principles of Biology

• Cell theory: all living organisms are composed of cells
• Gene theory: traits are inherited through genes
• Evolution: all life forms have evolved over time from a common ancestor through natural selection
• Homeostasis: living organisms maintain a stable internal environment
• Thermodynamics: Life depends on converting energy from one form to another

Cell Biology

• The cell is the basic unit of life
• Cells are either prokaryotic (lacking a nucleus) or eukaryotic (having a nucleus)
• Key cellular structures include the plasma membrane, cytoplasm, and nucleus (in eukaryotes)
• Organelles, such as mitochondria and chloroplasts, perform specific functions within the cell
• The cell membrane controls the transport of substances in and out of the cell
• Cellular respiration occurs in the mitochondria to produce energy in the form of ATP
• Photosynthesis occurs in chloroplasts, converting light energy into chemical energy (glucose)

Genetics

• Genetics is the study of heredity and variation of inherited characteristics
• Genes are segments of DNA that encode specific traits
• DNA is a double-stranded helix composed of nucleotides (adenine, guanine, cytosine, and thymine)
• RNA is a single-stranded nucleic acid involved in protein synthesis (adenine, guanine, cytosine, and uracil)
• Chromosomes are structures within the nucleus that contain DNA
• During cell division, chromosomes are duplicated and passed on to daughter cells
• Meiosis shuffles genetic information to create unique combinations
• Genotype refers to the genetic makeup of an organism
• Phenotype refers to the observable characteristics of an organism
• Mutations are changes in the DNA sequence that can lead to variations in traits
• Genetic engineering involves manipulating genes for various purposes, such as creating genetically modified organisms (GMOs)

Evolution

• Evolution is the process by which populations of organisms change over time
• Natural selection is the driving force of evolution, where individuals with advantageous traits are more likely to survive and reproduce
• Adaptation is the process by which organisms become better suited to their environment
• Evidence for evolution includes the fossil record, comparative anatomy, embryology, and molecular biology
• Speciation is the process by which new species arise
• Phylogenetic trees illustrate the evolutionary relationships between different organisms

Ecology

• Ecology is the study of the interactions between organisms and their environment
• Biomes are large-scale ecosystems characterized by specific climate conditions and dominant plant communities
• 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 composed of communities and their physical environment
• The biosphere is the global sum of all ecosystems
• Energy flows through ecosystems via food chains and food webs
• Nutrient cycles, such as the carbon cycle and nitrogen cycle, describe the movement of essential elements through ecosystems
• Symbiosis refers to the relationships between different species, including mutualism (both benefit), commensalism (one benefits, the other is unaffected), and parasitism (one benefits, the other is harmed)

Microbiology

• Microbiology is the study of microorganisms, including bacteria, viruses, fungi, and protists
• Bacteria are single-celled prokaryotic organisms
• Viruses are infectious agents that require a host cell to replicate
• Fungi are eukaryotic organisms that include yeasts, molds, and mushrooms
• Protists are a diverse group of eukaryotic microorganisms
• Microorganisms play important roles in nutrient cycling, decomposition, and disease
• Antibiotics are used to treat bacterial infections, while antiviral drugs are used to treat viral infections

Botany

• Botany is the scientific study of plants
• Plants are autotrophic organisms that produce their own food through photosynthesis
• Key plant structures include roots, stems, leaves, flowers, and fruits
• Plant tissues include vascular tissue (xylem and phloem), ground tissue, and epidermal tissue
• Plant reproduction can be sexual (involving flowers and seeds) or asexual (vegetative propagation)
• Plant hormones regulate growth, development, and responses to the environment

Zoology

• Zoology is the study of animals
• Animals are heterotrophic organisms that obtain energy by consuming other organisms
• Animals are classified into various phyla, including vertebrates (animals with a backbone) and invertebrates (animals without a backbone)
• Key animal organ systems include the digestive, respiratory, circulatory, nervous, and excretory systems
• Animal behavior is influenced by genetics and environmental factors