Introduction to Biology

• Biology is the scientific study of life and living organisms.
• It explores the structure, function, growth, origin, evolution, and distribution of living things.
• Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as 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.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells.
• Gene theory: Hereditary information is encoded in DNA and genes.
• Evolution: Life evolves through natural selection and other mechanisms.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on energy transformations.

Branches of Biology

• Biochemistry: Studies the chemical processes within and relating to living organisms.
• Molecular Biology: Examines the molecular basis of biological activity between biomolecules in the various systems of a cell.
• Cell Biology: Studies the structure, function, and behavior of cells.
• Genetics: Focuses on heredity and variation of inherited characteristics.
• Evolutionary Biology: Studies the evolutionary processes that produced the diversity of life on Earth.
• Ecology: Investigates the interactions between organisms and their environment.
• Physiology: Examines the functions and mechanisms in a living system.
• Anatomy: Deals with the structure of organisms and their parts.
• Botany: The scientific study of plants.
• Zoology: The scientific study of animals.
• Microbiology: Studies microorganisms.

The Cell

• The cell is the basic structural, functional, and biological unit of all known living organisms.
• It is the smallest unit of an organism that is considered living.
• Cells contain organelles, which perform specific functions within the cell.
• Two primary types of cells exist: eukaryotic cells and prokaryotic cells.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Prokaryotic cells do not have a nucleus or membrane-bound organelles.

Genetics

• Genetics studies genes, heredity, and variation in living organisms.
• Genes are units of heredity and are made up of DNA.
• DNA (deoxyribonucleic acid) carries the genetic instructions for all known living organisms and many viruses.
• The central dogma of molecular biology describes the flow of genetic information: DNA to RNA to protein.
• Mutations are changes in the DNA sequence and can lead to variations in traits.
• Genetic engineering involves manipulating genes for practical purposes.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is a key mechanism of evolution.
• Organisms with traits better suited to their environment are more likely to survive and reproduce.
• Adaptation is the process by which organisms become better suited to their environment.
• Evidence for evolution includes fossils, comparative anatomy, and molecular biology.
• Speciation is the process by which new species arise.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Ecosystems are communities of living organisms interacting with their physical 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.
• Trophic levels describe the position of an organism in a food chain or food web.
• Energy flows through ecosystems, while nutrients cycle within them.
• Biodiversity is the variety of life in an ecosystem.

Plant Biology

• Plants are multicellular, eukaryotic organisms in the kingdom Plantae.
• Plants perform photosynthesis, using sunlight, water, and carbon dioxide to produce oxygen and energy in the form of sugar (glucose).
• Plant cells have unique structures such as cell walls and chloroplasts.
• Plant anatomy includes roots, stems, leaves, and reproductive structures (flowers, cones).
• Plant physiology studies plant functions such as photosynthesis, transpiration, and nutrient transport.
• Plant reproduction can be sexual or asexual.

Animal Biology

• Animals are multicellular, eukaryotic organisms in the kingdom Animalia.
• Animals are heterotrophic, meaning they obtain nutrients by consuming other organisms.
• Animal cells lack cell walls.
• Animal anatomy includes tissues, organs, and organ systems (e.g., digestive, respiratory, circulatory).
• Animal physiology studies animal functions such as digestion, respiration, circulation, and reproduction.
• Animal behavior is the study of how animals interact with their environment and each other.
• Animals are classified into different phyla based on their body plan and evolutionary history.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, archaea, viruses, fungi, and protists.
• Microorganisms are essential for nutrient cycling, decomposition, and various industrial processes.
• Microorganisms can be beneficial (e.g., in digestion, fermentation) or harmful (e.g., causing diseases).
• Bacteria are prokaryotic cells with diverse metabolic capabilities.
• Viruses are non-cellular entities that require a host cell to replicate.
• Fungi are eukaryotic organisms that can be unicellular (e.g., yeasts) or multicellular (e.g., molds, mushrooms).
• Protists are a diverse group of eukaryotic microorganisms, including algae and protozoa.

Human Biology

• Human biology focuses on the structure, function, growth, origin, evolution, and distribution of humans.
• It involves anatomy, physiology, genetics, and evolutionary biology to understand the human body.
• The human body consists of various organ systems (e.g., skeletal, muscular, nervous, endocrine, cardiovascular, respiratory, digestive, urinary, reproductive, immune).
• Human genetics studies genes, heredity, and genetic variation in humans.
• Human evolution examines the evolutionary history of humans and their relationships with other primates.
• Human health and disease are important areas of study in human biology.