Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• 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 must maintain homeostasis to survive.

Branches of Biology

• Biochemistry: Study of the chemical processes within and relating to living organisms.
• Botany: Study of plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell Biology: Study of cell structure and function.
• Ecology: Study of the interactions of organisms with each other and their environment.
• Evolutionary Biology: Study of the evolutionary processes that produced the diversity of life on Earth.
• Genetics: Study of heredity and variation in organisms.
• Microbiology: Study of microorganisms, including bacteria, viruses, fungi, and protozoa.
• Molecular Biology: Study of the molecular basis of biological activity.
• Physiology: Study of the functions and mechanisms in a living system.
• Zoology: Study of animals, including their classification, physiology, behavior, and ecology.

Characteristics of Life

• Organization: Living things exhibit a complex organization, from atoms to molecules to organelles to cells to tissues to organs to organ systems to organisms to populations to communities to ecosystems to the biosphere.
• Metabolism: Living organisms carry out metabolic processes, including chemical reactions that provide energy and synthesize new molecules.
• Growth: Living organisms increase in size or cell number.
• Reproduction: Living organisms produce new individuals, either sexually or asexually.
• Response to Stimuli: Living organisms respond to changes in their environment.
• Adaptation: Living organisms evolve adaptations that allow them to survive and reproduce in their environment.
• Homeostasis: Living organisms maintain a stable internal environment.

Cell Structure and Function

• The cell is the basic unit of life.
• All living organisms are composed of one or more cells.
• Cells are either prokaryotic or eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Major cell structures include the plasma membrane, cytoplasm, nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, and cytoskeleton.
• The plasma membrane controls the movement of substances into and out of the cell.
• The cytoplasm is the region between the plasma membrane and the nucleus.
• The nucleus contains the cell's DNA.
• Ribosomes are responsible for protein synthesis.
• The endoplasmic reticulum is involved in protein and lipid synthesis.
• The Golgi apparatus processes and packages proteins.
• Lysosomes contain enzymes that break down cellular waste.
• Mitochondria are responsible for cellular respiration and ATP production.
• The cytoskeleton provides structural support and facilitates cell movement.

Genetics

• Genes are the basic units of heredity.
• Genes are composed of DNA.
• DNA (deoxyribonucleic acid) is a molecule that contains the instructions for building and maintaining an organism.
• DNA is organized into chromosomes.
• Humans have 46 chromosomes, arranged in 23 pairs.
• Genes code for proteins.
• Proteins carry out a variety of functions in the cell.
• The process of protein synthesis involves transcription and translation.
• Transcription is the process of copying DNA into RNA.
• Translation is the process of using RNA to build proteins.
• Mutations are changes in the DNA sequence.
• Mutations can be harmful, beneficial, or neutral.

Evolution

• Evolution is the process of change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the mechanism by which evolution occurs.
• Natural selection is the differential survival and reproduction of individuals with advantageous traits.
• Evidence for evolution includes fossil records, comparative anatomy, comparative embryology, and molecular biology.
• Adaptation is the result of evolution by natural selection.
• Speciation is the process by which new species arise.
• The theory of evolution is a unifying principle in biology.

Ecology

• Ecology is the study of the interactions of organisms with each other and their environment.
• An ecosystem consists of all the living organisms in a particular area, as well as the non-living components of the environment.
• Populations are groups of individuals of the same species living in the same area.
• Communities are groups of different populations living in the same area.
• The biosphere is the global sum of all ecosystems.
• Energy flows through ecosystems.
• Nutrients cycle within ecosystems.
• Organisms within an ecosystem can have different feeding roles, such as producers, consumers, and decomposers.
• Population size can be affected by factors such as birth rate, death rate, immigration, and emigration.
• Carrying capacity is the maximum population size that an environment can support.
• Ecological succession is the process of change in the species structure of an ecological community over time.
• Human activities can have a significant impact on ecosystems.

Classification of Living Things

• Taxonomy is the science of classifying and naming organisms.
• The current taxonomic system uses a hierarchical classification system.
• The major taxonomic ranks are domain, kingdom, phylum, class, order, family, genus, and species.
• There are three domains of life: Bacteria, Archaea, and Eukarya.
• The domain Eukarya includes four kingdoms: Protista, Fungi, Plantae, and Animalia.
• Species are the basic unit of classification.
• A species is defined as a group of organisms that can interbreed and produce fertile offspring.
• Binomial nomenclature is the system of naming organisms using two names: the genus and the species. For example, Homo sapiens is the binomial name for humans.

Biochemistry

• Biochemistry explores the chemical processes within and relating to living organisms.
• Key biomolecules include carbohydrates, lipids, proteins, and nucleic acids.
• Carbohydrates are sugars and starches that serve as a primary energy source.
• Lipids include fats, oils, and phospholipids; important for energy storage, insulation, and cell membrane structure.
• Proteins are made of amino acids; involved in almost all cell functions, including enzymes, structural components, and hormones.
• Nucleic acids (DNA and RNA) carry genetic information.
• Enzymes are biological catalysts that speed up chemical reactions in living organisms.
• Metabolism encompasses all the chemical reactions that occur in a cell or organism.

Microbiology

• Microbiology focuses on the study of microorganisms, including bacteria, viruses, fungi, and protozoa.
• Bacteria are single-celled prokaryotic organisms.
• Viruses are non-cellular entities that require a host cell to reproduce.
• Fungi are eukaryotic organisms that include yeasts, molds, and mushrooms.
• Protozoa are single-celled eukaryotic organisms.
• Microorganisms play important roles in nutrient cycling, decomposition, and disease.
• Some microorganisms are beneficial to humans, while others are pathogenic.

Plant Biology

• Plant biology (botany) studies plants, encompassing their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Plants are autotrophs, meaning they produce their own food through photosynthesis.
• Photosynthesis converts light energy into chemical energy in the form of glucose.
• Plant structures include roots, stems, leaves, flowers, and fruits.
• Plant reproduction can be sexual or asexual.
• Plants play a vital role in ecosystems, providing oxygen, food, and habitat for other organisms.

Animal Biology

• Animal biology (zoology) examines animals, including their classification, physiology, behavior, and ecology.
• Animals are heterotrophs, meaning they obtain their food by consuming other organisms.
• Animal cells lack cell walls.
• Animals exhibit a wide range of adaptations to their environments.
• Animal behavior is influenced by both genetics and environment.
• The study of animal diversity and evolution is essential for understanding the natural world.